2. MUHAMAD AMIN BIN ZAINI (AE090096)
3. AZMAN BIN AHAMAD (AE090140)
Wednesday, March 31, 2010
GROUP MEMBERS
1. RAJA MUHAMMAD MUZAFFAR BIN RAJA MAHADI (AE090237)
2. MUHAMAD AMIN BIN ZAINI (AE090096)
3. AZMAN BIN AHAMAD (AE090140)
2. MUHAMAD AMIN BIN ZAINI (AE090096)
3. AZMAN BIN AHAMAD (AE090140)
These are news from World Health Organization (WHO)
Electromagnetic fields and public health
Base stations and wireless technologies
Mobile telephony is now commonplace around the world. This wireless technology relies upon an extensive network of fixed antennas, or base stations, relaying information with radiofrequency (RF) signals. Over 1.4 million base stations exist worldwide and the number is increasing significantly with the introduction of third generation technology.
Other wireless networks that allow high-speed internet access and services, such as wireless local area networks (WLANs), are also increasingly common in homes, offices, and many public areas (airports, schools, residential and urban areas). As the number of base stations and local wireless networks increases, so does the RF exposure of the population. Recent surveys have shown that the RF exposures from base stations range from 0.002% to 2% of the levels of international exposure guidelines, depending on a variety of factors such as the proximity to the antenna and the surrounding environment. This is lower or comparable to RF exposures from radio or television broadcast transmitters.
There has been concern about possible health consequences from exposure to the RF fields produced by wireless technologies. This fact sheet reviews the scientific evidence on the health effects from continuous low-level human exposure to base stations and other local wireless networks.
Health concerns
A common concern about base station and local wireless network antennas relates to the possible long-term health effects that whole-body exposure to the RF signals may have. To date, the only health effect from RF fields identified in scientific reviews has been related to an increase in body temperature (> 1 °C) from exposure at very high field intensity found only in certain industrial facilities, such as RF heaters. The levels of RF exposure from base stations and wireless networks are so low that the temperature increases are insignificant and do not affect human health.
The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is restricted where RF signals may exceed international exposure limits. Recent surveys have indicated that RF exposures from base stations and wireless technologies in publicly accessible areas (including schools and hospitals) are normally thousands of times below international standards.
In fact, due to their lower frequency, at similar RF exposure levels, the body absorbs up to five times more of the signal from FM radio and television than from base stations. This is because the frequencies used in FM radio (around 100 MHz) and in TV broadcasting (around 300 to 400 MHz) are lower than those employed in mobile telephony (900 MHz and 1800 MHz) and because a person's height makes the body an efficient receiving antenna. Further, radio and television broadcast stations have been in operation for the past 50 or more years without any adverse health consequence being established.
While most radio technologies have used analog signals, modern wireless telecommunications are using digital transmissions. Detailed reviews conducted so far have not revealed any hazard specific to different RF modulations.
Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern. It should be noted that geographically, cancers are unevenly distributed among any population. Given the widespread presence of base stations in the environment, it is expected that possible cancer clusters will occur near base stations merely by chance. Moreover, the reported cancers in these clusters are often a collection of different types of cancer with no common characteristics and hence unlikely to have a common cause.
Scientific evidence on the distribution of cancer in the population can be obtained through carefully planned and executed epidemiological studies. Over the past 15 years, studies examining a potential relationship between RF transmitters and cancer have been published. These studies have not provided evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks.
Other effects: Few studies have investigated general health effects in individuals exposed to RF fields from base stations. This is because of the difficulty in distinguishing possible health effects from the very low signals emitted by base stations from other higher strength RF signals in the environment. Most studies have focused on the RF exposures of mobile phone users. Human and animal studies examining brain wave patterns, cognition and behaviour after exposure to RF fields, such as those generated by mobile phones, have not identified adverse effects. RF exposures used in these studies were about 1000 times higher than those associated with general public exposure from base stations or wireless networks. No consistent evidence of altered sleep or cardiovascular function has been reported.
Some individuals have reported that they experience non-specific symptoms upon exposure to RF fields emitted from base stations and other EMF devices. As recognized in a recent WHO fact sheet "Electromagnetic Hypersensitivity", EMF has not been shown to cause such symptoms. Nonetheless, it is important to recognize the plight of people suffering from these symptoms.
From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. Since wireless networks produce generally lower RF signals than base stations, no adverse health effects are expected from exposure to them.
Protection standards
International exposure guidelines have been developed to provide protection against established effects from RF fields by the International Commission on Non-Ionizing Radiation Protection (ICNIRP, 1998) and the Institute of Electrical and Electronic Engineers (IEEE, 2005).
National authorities should adopt international standards to protect their citizens against adverse levels of RF fields. They should restrict access to areas where exposure limits may be exceeded.
Public perception of risk
Some people perceive risks from RF exposure as likely and even possibly severe. Several reasons for public fear include media announcements of new and unconfirmed scientific studies, leading to a feeling of uncertainty and a perception that there may be unknown or undiscovered hazards. Other factors are aesthetic concerns and a feeling of a lack of control or input to the process of determining the location of new base stations. Experience shows that education programmes as well as effective communications and involvement of the public and other stakeholders at appropriate stages of the decision process before installing RF sources can enhance public confidence and acceptability.
Conclusions
Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.
WHO Initiatives
WHO, through the International EMF Project, has established a programme to monitor the EMF scientific literature, to evaluate the health effects from exposure to EMF in the range from 0 to 300 GHz, to provide advice about possible EMF hazards and to identify suitable mitigation measures? Following extensive international reviews, the International EMF Project has promoted research to fill gaps in knowledge. In response national governments and research institutes have funded over $250 million on EMF research over the past 10 years.
While no health effects are expected from exposure to RF fields from base stations and wireless networks, research is still being promoted by WHO to determine whether there are any health consequences from the higher RF exposures from mobile phones.
The International Agency for Research on Cancer (IARC), a WHO specialized agency, is expected to conduct a review of cancer risk from RF fields in 2006-2007 and the International EMF Project will then undertake an overall health risk assessment for RF fields in 2007-2008.
Base stations and wireless technologies
Mobile telephony is now commonplace around the world. This wireless technology relies upon an extensive network of fixed antennas, or base stations, relaying information with radiofrequency (RF) signals. Over 1.4 million base stations exist worldwide and the number is increasing significantly with the introduction of third generation technology.
Other wireless networks that allow high-speed internet access and services, such as wireless local area networks (WLANs), are also increasingly common in homes, offices, and many public areas (airports, schools, residential and urban areas). As the number of base stations and local wireless networks increases, so does the RF exposure of the population. Recent surveys have shown that the RF exposures from base stations range from 0.002% to 2% of the levels of international exposure guidelines, depending on a variety of factors such as the proximity to the antenna and the surrounding environment. This is lower or comparable to RF exposures from radio or television broadcast transmitters.
There has been concern about possible health consequences from exposure to the RF fields produced by wireless technologies. This fact sheet reviews the scientific evidence on the health effects from continuous low-level human exposure to base stations and other local wireless networks.
Health concerns
A common concern about base station and local wireless network antennas relates to the possible long-term health effects that whole-body exposure to the RF signals may have. To date, the only health effect from RF fields identified in scientific reviews has been related to an increase in body temperature (> 1 °C) from exposure at very high field intensity found only in certain industrial facilities, such as RF heaters. The levels of RF exposure from base stations and wireless networks are so low that the temperature increases are insignificant and do not affect human health.
The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is restricted where RF signals may exceed international exposure limits. Recent surveys have indicated that RF exposures from base stations and wireless technologies in publicly accessible areas (including schools and hospitals) are normally thousands of times below international standards.
In fact, due to their lower frequency, at similar RF exposure levels, the body absorbs up to five times more of the signal from FM radio and television than from base stations. This is because the frequencies used in FM radio (around 100 MHz) and in TV broadcasting (around 300 to 400 MHz) are lower than those employed in mobile telephony (900 MHz and 1800 MHz) and because a person's height makes the body an efficient receiving antenna. Further, radio and television broadcast stations have been in operation for the past 50 or more years without any adverse health consequence being established.
While most radio technologies have used analog signals, modern wireless telecommunications are using digital transmissions. Detailed reviews conducted so far have not revealed any hazard specific to different RF modulations.
Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern. It should be noted that geographically, cancers are unevenly distributed among any population. Given the widespread presence of base stations in the environment, it is expected that possible cancer clusters will occur near base stations merely by chance. Moreover, the reported cancers in these clusters are often a collection of different types of cancer with no common characteristics and hence unlikely to have a common cause.
Scientific evidence on the distribution of cancer in the population can be obtained through carefully planned and executed epidemiological studies. Over the past 15 years, studies examining a potential relationship between RF transmitters and cancer have been published. These studies have not provided evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks.
Other effects: Few studies have investigated general health effects in individuals exposed to RF fields from base stations. This is because of the difficulty in distinguishing possible health effects from the very low signals emitted by base stations from other higher strength RF signals in the environment. Most studies have focused on the RF exposures of mobile phone users. Human and animal studies examining brain wave patterns, cognition and behaviour after exposure to RF fields, such as those generated by mobile phones, have not identified adverse effects. RF exposures used in these studies were about 1000 times higher than those associated with general public exposure from base stations or wireless networks. No consistent evidence of altered sleep or cardiovascular function has been reported.
Some individuals have reported that they experience non-specific symptoms upon exposure to RF fields emitted from base stations and other EMF devices. As recognized in a recent WHO fact sheet "Electromagnetic Hypersensitivity", EMF has not been shown to cause such symptoms. Nonetheless, it is important to recognize the plight of people suffering from these symptoms.
From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. Since wireless networks produce generally lower RF signals than base stations, no adverse health effects are expected from exposure to them.
Protection standards
International exposure guidelines have been developed to provide protection against established effects from RF fields by the International Commission on Non-Ionizing Radiation Protection (ICNIRP, 1998) and the Institute of Electrical and Electronic Engineers (IEEE, 2005).
National authorities should adopt international standards to protect their citizens against adverse levels of RF fields. They should restrict access to areas where exposure limits may be exceeded.
Public perception of risk
Some people perceive risks from RF exposure as likely and even possibly severe. Several reasons for public fear include media announcements of new and unconfirmed scientific studies, leading to a feeling of uncertainty and a perception that there may be unknown or undiscovered hazards. Other factors are aesthetic concerns and a feeling of a lack of control or input to the process of determining the location of new base stations. Experience shows that education programmes as well as effective communications and involvement of the public and other stakeholders at appropriate stages of the decision process before installing RF sources can enhance public confidence and acceptability.
Conclusions
Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.
WHO Initiatives
WHO, through the International EMF Project, has established a programme to monitor the EMF scientific literature, to evaluate the health effects from exposure to EMF in the range from 0 to 300 GHz, to provide advice about possible EMF hazards and to identify suitable mitigation measures? Following extensive international reviews, the International EMF Project has promoted research to fill gaps in knowledge. In response national governments and research institutes have funded over $250 million on EMF research over the past 10 years.
While no health effects are expected from exposure to RF fields from base stations and wireless networks, research is still being promoted by WHO to determine whether there are any health consequences from the higher RF exposures from mobile phones.
The International Agency for Research on Cancer (IARC), a WHO specialized agency, is expected to conduct a review of cancer risk from RF fields in 2006-2007 and the International EMF Project will then undertake an overall health risk assessment for RF fields in 2007-2008.
effect of wireless in daily life
Wireless technology can provide many benefits to computing including faster respond to queries; reduce time spent on paperwork, increased online time for user, just-in-time and real control, tighter communications between clients and hosts. Wireless technology is governed by two general forces: technology, which provides a set of basic building blocks, and user application, which determine a set of operation that must be carried out efficiently on demand. This paper summarizes technological changes that are underway and describes their impact on wireless computing development and implementation. It also describes the applications that influence the development and implementation of wireless computing and shows what current systems offer.
There are many effect of using wireless in daily life. Beside, the increasing of number of using wireless is high than before the wireless is being exposed to public. In Malaysia, 8 over 10 houses have their own wireless networking. Not only house, in public area such as shopping mall also have the wireless network. This shows that’s wireless is very important to everyone not only in Malaysia but the whole world. Besides, people nowadays use this kind of technology randomly in high quantities on it. But we don’t know even they noticed that there are effect of using wireless in daily life.
There are many effect of using the wireless technology in daily life. For example to our health.
Use of Wireless communication devices are increasing exponentially. This growth is phenomenal particularly in past few years. Several researches concluded that increased exposure to the ‘Radiofrequencies (RF)’ emitted by these wireless communication devices cause potential health effects.
Almost all the present studies demonstrate effects on the healthy adults who comparably have lesser exposures to the RF fields. Experts are now realizing that findings of such studies are not relevant in case of children who have a higher exposure to the RF fields.”Potential health consequences from multiple, long –term, low intensity RF exposure need to be studied in detail in present context”, feel the researchers.
In case of children the ‘Specific Absorption Rates (SAR)’ is expected to be higher compared to the adults. It is mainly because of the closeness of the exposure wavelength the whole-body resonance frequency in case of children who are shorter in height compared to the adults.
The young generation of today is also expected to experience a longer period of exposure with the RF field generated by the mobile devices. Children normally start using these devices at an early age and this makes them more exposed than to the adults. Many studies conducted with this focus have revealed that there is an exponential growth in the mobile phone ownership among children. Researchers feel that there is an urgent need to conduct studies with human populations being affected by these devices causing present and future health problems.
There are many effect of using wireless in daily life. Beside, the increasing of number of using wireless is high than before the wireless is being exposed to public. In Malaysia, 8 over 10 houses have their own wireless networking. Not only house, in public area such as shopping mall also have the wireless network. This shows that’s wireless is very important to everyone not only in Malaysia but the whole world. Besides, people nowadays use this kind of technology randomly in high quantities on it. But we don’t know even they noticed that there are effect of using wireless in daily life.
There are many effect of using the wireless technology in daily life. For example to our health.
Use of Wireless communication devices are increasing exponentially. This growth is phenomenal particularly in past few years. Several researches concluded that increased exposure to the ‘Radiofrequencies (RF)’ emitted by these wireless communication devices cause potential health effects.
Almost all the present studies demonstrate effects on the healthy adults who comparably have lesser exposures to the RF fields. Experts are now realizing that findings of such studies are not relevant in case of children who have a higher exposure to the RF fields.”Potential health consequences from multiple, long –term, low intensity RF exposure need to be studied in detail in present context”, feel the researchers.
In case of children the ‘Specific Absorption Rates (SAR)’ is expected to be higher compared to the adults. It is mainly because of the closeness of the exposure wavelength the whole-body resonance frequency in case of children who are shorter in height compared to the adults.
The young generation of today is also expected to experience a longer period of exposure with the RF field generated by the mobile devices. Children normally start using these devices at an early age and this makes them more exposed than to the adults. Many studies conducted with this focus have revealed that there is an exponential growth in the mobile phone ownership among children. Researchers feel that there is an urgent need to conduct studies with human populations being affected by these devices causing present and future health problems.
Types of Unauthorized Access to Wireless Networks
The unauthorized access to the wireless signals is really common. The various types of unauthorized access are malicious association, accidental association, ad hoc networks, and nontraditional networks, man in the middle attack, identity theft and denial of service. When a user turn on its PC, and he or she receives unauthorized signals from a neighboring building. User might not even signals are emerging and make use of it are have a clue from where they are emerging and make use of it , then we can call it accidental association. When a person uses crackers to access the password of the wireless network it is termed as malicious network. When the wireless technology has no centre device to act for it encryption settings are hard to mange therefore security cannot be achieved. Bluetooth devices and PDAs are nontraditional form of networks; they can be easily hacked by using cracker technology.
Major disadvantages of wireless technology
Wireless is a public frequency network therefore its interface is highly risky to be used for official private information. The speed and the viability of the wireless signals drop as more and more users use the same frequency. Moreover its original throughput is three times less than it claims to deliver. Wireless technology is available in only three major channels ranging from 2.5 GHz, 11 and 1.6 GHz, Which is much lower than the wired network. They are 50 times slower than the wired network technologies. The wireless signals are also attuned by the barriers such as walls, doors and devices itself. The setup of the wireless technology is difficult maintain. Hence it an unstable network. Though wireless technologies provide flexibility to use and carry your laptop or any other portable device with you anywhere, but the longer the distance the weaker the signals. The extensive use of wireless signals over the mobile phone is dangerous to the health of the human beings. The various health problems that wireless can pose are memory loss and even cancer.
Wireless signals are prone to disrupt by the infrared and radio signals. Wireless technologies are four times more expensive than wired technology due to their difficult setup. If one needs to transfer confidential data over the network wireless technology is a serious risk to be used. Banks, investigation agencies and legal data should be transferred using wired network technologies, because they are more safe and sound. The wireless technology offers public access points which hinder the efficient transfer of data.
Wireless signals are prone to disrupt by the infrared and radio signals. Wireless technologies are four times more expensive than wired technology due to their difficult setup. If one needs to transfer confidential data over the network wireless technology is a serious risk to be used. Banks, investigation agencies and legal data should be transferred using wired network technologies, because they are more safe and sound. The wireless technology offers public access points which hinder the efficient transfer of data.
Disadvantages of wireless networks
The development in the communication systems and the networking has given rise to the wireless networks. The ease and flexibility of wireless communication has enabled us to use personal assistance devices to be used anywhere. This has enabled the mankind to excel in every field of the life, but at the same time it has many threats as well.
Security threats to Wireless Networks
Besides all the comforts of the life wireless networks poses serious security threats. The main reason is the signals are spread in the air and it is convenient for the hackers to catch wireless signals. Wireless networks require very tight security so that the unauthorized users cannot exploit the information. As more and users are making use of the wireless technologies, the risk of data being lost is increasing. The current wireless encryption protocols are difficult to handle .moreover the common users are not aware of the ways of addressing wireless security matters. One must build strong security protocols in order to secure the wireless signals like WPA and WPA2. Moreover wireless intrusion prevention system is another better way to build strong security system.
Security threats to Wireless Networks
Besides all the comforts of the life wireless networks poses serious security threats. The main reason is the signals are spread in the air and it is convenient for the hackers to catch wireless signals. Wireless networks require very tight security so that the unauthorized users cannot exploit the information. As more and users are making use of the wireless technologies, the risk of data being lost is increasing. The current wireless encryption protocols are difficult to handle .moreover the common users are not aware of the ways of addressing wireless security matters. One must build strong security protocols in order to secure the wireless signals like WPA and WPA2. Moreover wireless intrusion prevention system is another better way to build strong security system.
Wireless Routers - Some Disadvantages
.png)
Wireless routers allow flexibility and freedom for many internet users. With Wi-Fi, a person can sit at a coffee shop and start surfing the web as if they were connected to a phone jack or cable at home. Even today, some towns are going completely wireless so that anyone within the vicinity can access the net for free.
But with all the advantages that wireless routers provide there are things we should be mindful of when we decide to plug in the router. Wireless routers are not necessarily without their flaws. Here are few things to keep in mind.
If a person were to connect directly to the internet with a cable and compare that with the same connection, but with a wireless router, there would be a noticeable difference. The wireless connection will be slightly slower than the direct connection. The reason is simple; a Wi-Fi transmits through the air and there's some degradation with this medium. It's like comparing television reception between cable and antennas. Cable is obviously faster.
Possibly a huge concern with wireless routers and Wi-Fi is the encryption protocols. In some public Wi-Fi places (such as a local café), the transmission is encryption free. This means that all of your private data stored in your laptop or PDA will be exposed to anyone in the same vicinity. It's possible that an unscrupulous person could obtain passwords and important personal information.
An older protocol for wireless routers is the Wired Equivalent Privacy (WEP). Although it does have a level of encryption, the encryption can be easily compromised. The problem has caused a number of wireless router owners to upgrade to WPA and WPA2 encryption protocols.
With the increasing Wi-Fi hotspots in the neighborhood, Wi-Fi pollution is becoming more apparent. Sometimes stores or organizations will broadcast over the same channel, causing interference and lack of access points. Cities are just noticing this problem as more users are jumping into the wireless realm.
Other devices and equipment can also contribute to the pollution. Studies have shown that Bluetooth devices, cordless phones and microwave ovens all contribute to interference of public wireless transmissions. This is a known problem in high-density areas such as cities with many access points.
Wireless routers do not have a limitless range. As such, the broadcasting radius could be limited to just a 150 to 300 ft. If you want to improve the range, you'd have to purchase Wi-Fi antennas.
The wireless Wi-Fi realm is different to other mediums such as Bluetooth. The power consumption is much greater for devices using Wi-Fi through a wireless router or access point. People who use PDAs or laptops will burn through battery power.
Another problem is that for countries all over the world, you'll find differing spectrum assignments. The lack of consistency has caused problems for internet users traveling from country to country. In some instances, governments may prohibit use of certain channels or require special authorization.
There are many disadvantages of wireless routers and Wi-Fi, but the disadvantages should not necessarily stop a person to use the service. Consider the pros and cons of the wireless realm first before jumping into the World Wide Web.
Disadvantages of Wireless Internet
With wireless Internet service, there’s the problem of someone, within the wireless traffic, hacking into your connection. So, you need to be sure to use wireless security to ensure all your private information is safe from those unauthorized viewers. There are many firewalls out there that work well for this purpose or you can look into using a network system to set up password protected connections.
Verizon wireless and Sprint wireless are two popular wireless companies in business today. Verizon wireless offer several different types of wireless devices that are commonly used by consumers. Cell phones and wireless broadband Internet are the most popular services they offer. They also offer PDAs and wireless PC cards.
Wireless technology comes in various other forms as well. You can find wireless speakers for your stereo system, wireless headphones, wireless receivers and transmitters and even microphones. You can find wireless computer mice, keyboards, satellite TV, cordless telephones and even garage door openers. The future will probably bring us a world full of wireless technology. Hard wired devices will end up being more of a thing of the past, once wireless technology grows.
Verizon wireless and Sprint wireless are two popular wireless companies in business today. Verizon wireless offer several different types of wireless devices that are commonly used by consumers. Cell phones and wireless broadband Internet are the most popular services they offer. They also offer PDAs and wireless PC cards.
Wireless technology comes in various other forms as well. You can find wireless speakers for your stereo system, wireless headphones, wireless receivers and transmitters and even microphones. You can find wireless computer mice, keyboards, satellite TV, cordless telephones and even garage door openers. The future will probably bring us a world full of wireless technology. Hard wired devices will end up being more of a thing of the past, once wireless technology grows.
disadvantage
One of the disadvantages of wireless technology is that it can be operated only for a limited period of time. There is the possibility that interference of other radio equipments may affect the system though this may vary from model to model. Once you get really into microphones, you may consider looking for cheap vintage microphones for sale. You can use them, or add them to your collection, and hey, the look really cool. The neat thing is that they are available on the internet for really cheap prices.
• Lower speed compared to wired network.
• Less secure because hacker's laptop can act as Access Point. If we connected to their laptop, they'll read all our information (username, password).
• More complex to configure than wired network.
• Affected by surrounding. example: walls (blocking), microwave oven (interference), far distance (attenuation)
• Lower speed compared to wired network.
• Less secure because hacker's laptop can act as Access Point. If we connected to their laptop, they'll read all our information (username, password).
• More complex to configure than wired network.
• Affected by surrounding. example: walls (blocking), microwave oven (interference), far distance (attenuation)
Advantages of wireless technology in other application
Security systems
Wireless technology may supplement or replace hard wired implementations in security systems for homes or office buildings. This will help human in case to prevent theft. With this wireless also, consumer can reduce the amount of wire that use. This indirectly will make the environment become more smart and simple. Supplier also easy to install this system unit without making major wiring.
Television remote control
Modern televisions use wireless (generally infrared) remote control units. Now radio waves are also used. This helps us especially to change one channel to another just from far.
Global Positioning System (GPS):
allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth
The following list summarizes the main benefits of using wireless technologies:
1 Completes the access technology portfolio: customers commonly use more than one access technology to service various parts of their network and during the migration phase of their networks, when upgrading occurs on a scheduled basis. Wireless enables a fully comprehensive access technology portfolio to work with existing dial, cable, and DSL technologies.
2 Goes where cable and fiber cannot: the inherent nature of wireless is that it doesn't require wires or lines to accommodate the data/voice/video pipeline. As such, the system will carry information across geographical areas that are prohibitive in terms of distance, cost, access, or time. It also sidesteps the numerous issues of ILEC colocation.
3 Involves reduced time to revenue: companies can generate revenue in less time through the deployment of wireless solutions than with comparable access technologies because a wireless system can be assembled and brought online in as little as two to three hours.
4 Provides broadband access extension: wireless commonly both competes with and complements existing broadband access. Wireless technologies play a key role in extending the reach of cable, fiber, and DSL markets, and it does so quickly and reliably. It also commonly provides a competitive alternative to broadband wireline or provides access in geographies that don't qualify for loop access.
.png)
Range from peer-to-peer networks suitable for a small number of users to large infrastructure networks that enable roaming over a broad area.
Wireless technology may supplement or replace hard wired implementations in security systems for homes or office buildings. This will help human in case to prevent theft. With this wireless also, consumer can reduce the amount of wire that use. This indirectly will make the environment become more smart and simple. Supplier also easy to install this system unit without making major wiring.
Television remote control
Modern televisions use wireless (generally infrared) remote control units. Now radio waves are also used. This helps us especially to change one channel to another just from far.
Global Positioning System (GPS):
allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth
The following list summarizes the main benefits of using wireless technologies:
1 Completes the access technology portfolio: customers commonly use more than one access technology to service various parts of their network and during the migration phase of their networks, when upgrading occurs on a scheduled basis. Wireless enables a fully comprehensive access technology portfolio to work with existing dial, cable, and DSL technologies.
2 Goes where cable and fiber cannot: the inherent nature of wireless is that it doesn't require wires or lines to accommodate the data/voice/video pipeline. As such, the system will carry information across geographical areas that are prohibitive in terms of distance, cost, access, or time. It also sidesteps the numerous issues of ILEC colocation.
3 Involves reduced time to revenue: companies can generate revenue in less time through the deployment of wireless solutions than with comparable access technologies because a wireless system can be assembled and brought online in as little as two to three hours.
4 Provides broadband access extension: wireless commonly both competes with and complements existing broadband access. Wireless technologies play a key role in extending the reach of cable, fiber, and DSL markets, and it does so quickly and reliably. It also commonly provides a competitive alternative to broadband wireline or provides access in geographies that don't qualify for loop access.
.png)
Range from peer-to-peer networks suitable for a small number of users to large infrastructure networks that enable roaming over a broad area.
advantage of wireless technologyge on wifi(internet), bluetooth, mobile phone
Advantages of wireless technology in internet or WiFi:-
Wireless internet or Wi Fi is one of the latest developments in providing people with Internet access whenever they need it even while traveling. This is a convenient way to stay connected with family members or business clients anytime of the day.
Wireless internet or Wi Fi is one of the latest developments in providing people with Internet access whenever they need it even while traveling. This is a convenient way to stay connected with family members or business clients anytime of the day.
With the fast evolution and advancement of the Internet, millions of people all over the world make use of the Internet in their daily life.
The internet offers a lot of useful information such as weather forecast, entertainment, research, music, news, online shopping, and many more.
The Web also provides a more convenient way for people to communicate with others even in far away countries.
Businesses are also dependent on the Internet in dealing with their clients whether local or abroad. They too are kept posted with the trends as well as stock updates though the Net. They also use corporate e mails in nearly all of their correspondence. Customer services and technical support of many companies also rely on the power of internet. Indeed, the Internet had become a necessity for ordinary people as well as business people.
Because of enormous growth of dependency on the Internet, people want to have internet connection even when on the go. This is now possible through the development of wireless Internet. Wireless Internet is popularly known as Wi Fi, which is the trade name of this kind of wireless technology. A wireless Internet access is commonly called as hot spot in which a LAN or local area network transmits radio waves as opposed to a wired network.
.png)
.png)
Some of the internet wireless instrument
Internet connection is broadcast with the use of a central hub connected to a computer system that functions as the server. The server broadcasts the signal to clients which have Wi Fi capable devices such as desktop computers, PDAs, laptops, mobile phones, game consoles, and many more electronic gadgets. The wireless internet covers diverse IEEE 802.11 advanced technologies such as 802.11n, 802.11b, 802.11g, and 802.11a.
A home network can be set with wireless Internet, as well. This is done through the utilization of a router which performs as an access point. The router broadcasts Internet connectivity to Wi Fi enabled devices within its area of reach. With this set of connections, anyone from the family can make use of their laptops or desktops and can gain access to the Internet.
What’s more, wireless Internet through home network can also be accessed by neighbors without your knowledge. To resolve this issue, a password security can be configured so that only authorized devices can have access to the network. With the growing risk of security issues, the security protocols for Wi Fi log on have been made available with the employment of Wi Fi Protected Access (WPA) and the Wi Fi Protected Access 2 (WPA2).
Wireless internet through its public hot spot is being offered for free to its customers by many business establishments. These establishments include internet cafes, food chains, coffee shops, hotels, and restaurants. Some airports also provide the same service for travelers’ convenience. These features are becoming very prevalent in many places and countries. There are also a number of cities which provide wireless Internet access to their residences and visitors. Since the hot spot can cover only a certain area, you have to be within the range of the hub in order to log on to the Web.
Significantly, a wireless Internet is of great advantage compared to wired network. Wired network usually consumes a lot of time in order to set up in a building or house. It also entails more expenses as it requires a lot of UTP cables to be wired for each of a client’s computers. In some instances, there is a need to route wires through thick wall or ceilings. Wireless LANs can be deployed easily and is less expensive. More clients can be added to the network without the necessity for extra materials.
Since 2008, many of the latest laptops and gadgets come with a built in wireless network device. There are also a lot of gadgets which can be applied for computers or laptops that do not have any wireless network device. Some of these devices are the USB Wi Fi adapters, PCI wireless adapters, PCMCIA Wi Fi cards and other similar devices. There are also wireless repeaters used to extend the range of signal of any existing wireless network. This device is ideal for locations having many physical barriers like thick walls and in cases where there is a need to share the Internet in two separate buildings.
Advantages of wireless technology in Bluetooth wireless USB adapter :-
Bluetooth is a wireless technology, using a small microchip, a portable device and a mobile. Your mobile and the device get interconnected by Bluetooth as soon as they come within the specific range.
The technology thus gives you short range connectivity using 2.4 GHZ radio waves, without the use of wires and different size of cables. But what you need is the Bluetooth USB adapter and the chip. This chip function just likes the cable wires but they use radio waves to connect and transmit the information.
Bluetooth USB is a small hardware device. Bluetooth adapters and the dongles are the small devices almost the size of your small finger and they can be attached to the USB port in your personal computers. As you attach the dongle the computer automatically gets connected to the nearby mobile by Bluetooth. You can then use these settings to download the ring tones or wallpapers to your mobile.
How is it advantageous?
The first benefit is that you don't have to tangle yourself in those noodle strip wires and cables. You just insert the US dongle in the USB port and download the wallpapers or ring tones or the games to your mobile.
It is simple to use. You just need to be in the range of 10-15 meter distance, so that your devices get connected by Bluetooth.
It is safe to use. The devices with Bluetooth exchange the authentication details and get connected automatically.
The technology also supports the VOIP technology hence you can talk to your friends also.
When you are using the USB adapter on your personal computer, then you are in a way using the computer and the mobile technologies together.
Around 8 devices can connect within the piconet or Personal Area Network formed by the Bluetooth.
You can transfer the games, ring tones, songs, text messages, and files among the connected devices in the piconet at the speed of 1-2Mbps.
When you connect the Bluetooth USB adapter to your computer you make your computer Bluetooth enable. That means your computer can now exchange the authentication code with other Bluetooth enabled devices in the short range of the piconet and get connected wirelessly. Now you can coordinate the contacts on your desktop or print the sheets or transfer files.
Although the connectivity is affected if there are more devices within the piconet or there are any changes in the environment, but the advantages out power the demerits.
.png)
Some of the Bluetooth USB that use wireless technology
Advantages of wireless technology in mobile phone :-
A mobile phone or mobile also called cell phone and hand phone is an electronic device used for mobile telecommunications (mobile telephone, text messaging or data transmission) over a cellular network of specialized base stations known as cell sites. Mobile phones differ from cordless telephones, which only offer telephone service within limited range, e.g. within a home or an office, through a fixed line and a base station owned by the subscriber and also from satellite phones and radio telephones.
This is one of the modern instruments that use wireless technology. One of the advantages using this wireless technology in mobile phone is it:-
• Portable were we can carry it everywhere we want
• Allow us to use all available service in that have such as sending message,MMS and make video call with clear visual without distribution
This is because Wireless telephone that permits telecommunication within a defined area that may include hundreds of square miles, using radio waves in the 800 – 900 megahertz (MHz) band. To implement a cell-phone system, a geographic area is broken into smaller areas or cells, usually mapped as uniform hexagrams but in fact overlapping and irregularly shaped. Each cell is equipped with a low-powered radio transmitter and receiver that permit propagation of signals among cell-phone users.
.png)
Several examples of non-flip mobile phones, from the early 2000s.
Wireless internet or Wi Fi is one of the latest developments in providing people with Internet access whenever they need it even while traveling. This is a convenient way to stay connected with family members or business clients anytime of the day.
Wireless internet or Wi Fi is one of the latest developments in providing people with Internet access whenever they need it even while traveling. This is a convenient way to stay connected with family members or business clients anytime of the day.
With the fast evolution and advancement of the Internet, millions of people all over the world make use of the Internet in their daily life.
The internet offers a lot of useful information such as weather forecast, entertainment, research, music, news, online shopping, and many more.
The Web also provides a more convenient way for people to communicate with others even in far away countries.
Businesses are also dependent on the Internet in dealing with their clients whether local or abroad. They too are kept posted with the trends as well as stock updates though the Net. They also use corporate e mails in nearly all of their correspondence. Customer services and technical support of many companies also rely on the power of internet. Indeed, the Internet had become a necessity for ordinary people as well as business people.
Because of enormous growth of dependency on the Internet, people want to have internet connection even when on the go. This is now possible through the development of wireless Internet. Wireless Internet is popularly known as Wi Fi, which is the trade name of this kind of wireless technology. A wireless Internet access is commonly called as hot spot in which a LAN or local area network transmits radio waves as opposed to a wired network.
.png)
.png)
Some of the internet wireless instrument
Internet connection is broadcast with the use of a central hub connected to a computer system that functions as the server. The server broadcasts the signal to clients which have Wi Fi capable devices such as desktop computers, PDAs, laptops, mobile phones, game consoles, and many more electronic gadgets. The wireless internet covers diverse IEEE 802.11 advanced technologies such as 802.11n, 802.11b, 802.11g, and 802.11a.
A home network can be set with wireless Internet, as well. This is done through the utilization of a router which performs as an access point. The router broadcasts Internet connectivity to Wi Fi enabled devices within its area of reach. With this set of connections, anyone from the family can make use of their laptops or desktops and can gain access to the Internet.
What’s more, wireless Internet through home network can also be accessed by neighbors without your knowledge. To resolve this issue, a password security can be configured so that only authorized devices can have access to the network. With the growing risk of security issues, the security protocols for Wi Fi log on have been made available with the employment of Wi Fi Protected Access (WPA) and the Wi Fi Protected Access 2 (WPA2).
Wireless internet through its public hot spot is being offered for free to its customers by many business establishments. These establishments include internet cafes, food chains, coffee shops, hotels, and restaurants. Some airports also provide the same service for travelers’ convenience. These features are becoming very prevalent in many places and countries. There are also a number of cities which provide wireless Internet access to their residences and visitors. Since the hot spot can cover only a certain area, you have to be within the range of the hub in order to log on to the Web.
Significantly, a wireless Internet is of great advantage compared to wired network. Wired network usually consumes a lot of time in order to set up in a building or house. It also entails more expenses as it requires a lot of UTP cables to be wired for each of a client’s computers. In some instances, there is a need to route wires through thick wall or ceilings. Wireless LANs can be deployed easily and is less expensive. More clients can be added to the network without the necessity for extra materials.
Since 2008, many of the latest laptops and gadgets come with a built in wireless network device. There are also a lot of gadgets which can be applied for computers or laptops that do not have any wireless network device. Some of these devices are the USB Wi Fi adapters, PCI wireless adapters, PCMCIA Wi Fi cards and other similar devices. There are also wireless repeaters used to extend the range of signal of any existing wireless network. This device is ideal for locations having many physical barriers like thick walls and in cases where there is a need to share the Internet in two separate buildings.
Advantages of wireless technology in Bluetooth wireless USB adapter :-
Bluetooth is a wireless technology, using a small microchip, a portable device and a mobile. Your mobile and the device get interconnected by Bluetooth as soon as they come within the specific range.
The technology thus gives you short range connectivity using 2.4 GHZ radio waves, without the use of wires and different size of cables. But what you need is the Bluetooth USB adapter and the chip. This chip function just likes the cable wires but they use radio waves to connect and transmit the information.
Bluetooth USB is a small hardware device. Bluetooth adapters and the dongles are the small devices almost the size of your small finger and they can be attached to the USB port in your personal computers. As you attach the dongle the computer automatically gets connected to the nearby mobile by Bluetooth. You can then use these settings to download the ring tones or wallpapers to your mobile.
How is it advantageous?
The first benefit is that you don't have to tangle yourself in those noodle strip wires and cables. You just insert the US dongle in the USB port and download the wallpapers or ring tones or the games to your mobile.
It is simple to use. You just need to be in the range of 10-15 meter distance, so that your devices get connected by Bluetooth.
It is safe to use. The devices with Bluetooth exchange the authentication details and get connected automatically.
The technology also supports the VOIP technology hence you can talk to your friends also.
When you are using the USB adapter on your personal computer, then you are in a way using the computer and the mobile technologies together.
Around 8 devices can connect within the piconet or Personal Area Network formed by the Bluetooth.
You can transfer the games, ring tones, songs, text messages, and files among the connected devices in the piconet at the speed of 1-2Mbps.
When you connect the Bluetooth USB adapter to your computer you make your computer Bluetooth enable. That means your computer can now exchange the authentication code with other Bluetooth enabled devices in the short range of the piconet and get connected wirelessly. Now you can coordinate the contacts on your desktop or print the sheets or transfer files.
Although the connectivity is affected if there are more devices within the piconet or there are any changes in the environment, but the advantages out power the demerits.
.png)
Some of the Bluetooth USB that use wireless technology
Advantages of wireless technology in mobile phone :-
A mobile phone or mobile also called cell phone and hand phone is an electronic device used for mobile telecommunications (mobile telephone, text messaging or data transmission) over a cellular network of specialized base stations known as cell sites. Mobile phones differ from cordless telephones, which only offer telephone service within limited range, e.g. within a home or an office, through a fixed line and a base station owned by the subscriber and also from satellite phones and radio telephones.
This is one of the modern instruments that use wireless technology. One of the advantages using this wireless technology in mobile phone is it:-
• Portable were we can carry it everywhere we want
• Allow us to use all available service in that have such as sending message,MMS and make video call with clear visual without distribution
This is because Wireless telephone that permits telecommunication within a defined area that may include hundreds of square miles, using radio waves in the 800 – 900 megahertz (MHz) band. To implement a cell-phone system, a geographic area is broken into smaller areas or cells, usually mapped as uniform hexagrams but in fact overlapping and irregularly shaped. Each cell is equipped with a low-powered radio transmitter and receiver that permit propagation of signals among cell-phone users.
.png)
Several examples of non-flip mobile phones, from the early 2000s.
advantage of wireless technology
Wireless networking is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:
• Can span a distance beyond the capabilities of typical cabling,
• Can provide a backup communications link in case of normal network failure,
• Can link portable or temporary workstations,
• Can overcome situations where normal cabling is difficult or financially impractical, or
• Can remotely connect mobile users or networks.
Wireless networks offer the following productivity, convenience, and cost advantages over traditional wired networks:
• Mobility: provide mobile users with access to real-time information so that they can roam around in the network without getting disconnected from the network. This mobility supports productivity and service opportunities not possible with wired networks.
• Installation speed and simplicity: installing a wireless system can be fast and easy and can eliminate the need to pull cable through walls and ceilings.
• Reach of the network: the network can be extended to places which can not be wired
• More Flexibility: wireless networks offer more flexibility and adapt easily to changes in the configuration of the network.
• Reduced cost of ownership: while the initial investment required for wireless network hardware can be higher than the cost of wired network hardware, overall installation expenses and life-cycle costs can be significantly lower in dynamic environments.
• Scalability: wireless systems can be configured in a variety of topologies to meet the needs of specific applications and installations. Configurations can be easily changed and range from peer-to-peer networks suitable for a small number of users to large infrastructure networks that enable roaming over a broad area.
.png)
Handheld wireless radios such as this Maritime VHF radio transceiver use electromagnetic waves to implement a form of wireless communications technology.
• Can span a distance beyond the capabilities of typical cabling,
• Can provide a backup communications link in case of normal network failure,
• Can link portable or temporary workstations,
• Can overcome situations where normal cabling is difficult or financially impractical, or
• Can remotely connect mobile users or networks.
Wireless networks offer the following productivity, convenience, and cost advantages over traditional wired networks:
• Mobility: provide mobile users with access to real-time information so that they can roam around in the network without getting disconnected from the network. This mobility supports productivity and service opportunities not possible with wired networks.
• Installation speed and simplicity: installing a wireless system can be fast and easy and can eliminate the need to pull cable through walls and ceilings.
• Reach of the network: the network can be extended to places which can not be wired
• More Flexibility: wireless networks offer more flexibility and adapt easily to changes in the configuration of the network.
• Reduced cost of ownership: while the initial investment required for wireless network hardware can be higher than the cost of wired network hardware, overall installation expenses and life-cycle costs can be significantly lower in dynamic environments.
• Scalability: wireless systems can be configured in a variety of topologies to meet the needs of specific applications and installations. Configurations can be easily changed and range from peer-to-peer networks suitable for a small number of users to large infrastructure networks that enable roaming over a broad area.
.png)
Handheld wireless radios such as this Maritime VHF radio transceiver use electromagnetic waves to implement a form of wireless communications technology.
6. Digital Wireless Systems
As other links in the audio chain have been converted to the digital domain it is of interest to look at the impact of digital technology on wireless transmission systems. Digital techniques can be applied to professional wireless in several ways, each offering potential benefits. The first level of application has been the use of digital control circuits for various tasks such as frequency selection, diversity antenna switching and most display functions. Nearly all frequency-agile wireless systems benefit from the use of digital controls and digital displays.
The next digital application level employs DSP (Digital Signal Processing) to replace traditional analog companding circuits. An audio DSP circuit is used in the transmitter to optimize the input signal for transmission and a complementary audio DSP is used in the receiver to optimize the output signal. The radio transmission path is still in the analog domain. Benefits may include increased audio dynamic range, decreased companding artifacts, and wider frequency response.The highest level of digital implementation uses a fully digital transmission path.
The input signal is digitized in the transmitter and remains in the digital domain until the receiver output. It is even possible to output a digital signal from the receiver to subsequent digital equipment. Potential benefits of an all-digital wireless approach include both improved audio quality and improved radio transmission. However, the technical requirements are not trivial and the inevitable compromise between performance and cost requires some difficult decisions. In concept, fully digital wireless transmission is simple. Add an analog-to-digital (A/D) converter at the input of the transmitter. Transmit the resulting digital information to
the receiver.
Demodulate the digital information and add a complementary digital-to-analog (D/A) converter at the output of the receiver. The ultimate limitation lies in the amount of digital information that must be reliably transmitted for acceptable audio quality. In general, information transmission techniques (wired or wireless) must balance bandwidth limitations with hardware (and software) complexity. Bandwidth refers to the range of frequencies and/or amplitudes used to convey the information. In audio, a frequency range of 20- 20,000Hz and an amplitude range (dynamic range) of 120dB is perhaps the ultimate goal.
However, a frequency range of 300-3000Hz and a dynamic range of 30dB are sufficient for telephone-quality speech. As expected, high fidelity audio equipment tends to be more complex and costly than telephone equipment. In analog FM radio systems, audio fidelity is greatly dependent on allowable deviation, which is related to RF bandwidth: wider deviation increases occupied bandwidth. Walkie-talkies use less bandwidth than wireless microphones. Even so, bandwidth limitations necessitate the use of companders to achieve acceptable dynamic range in most high quality analog wireless systems.
The bandwidth required for a high fidelity digital wireless system depends on the amount of digital information transmitted and the transmission rate. In practice, the bandwidth is limited by physical and regulatory requirements. This effectively constrains the amount and rate of information that can be transmitted. Ultimately, the fidelity and reliability of a digital wireless system is limited by these same bandwidth restrictions. A digital representation of an analog audio signal is generated by sampling (measuring the amplitude of) the audio waveform at some rate. The rate must be equal to at least twice the highest audio frequency desired. The resolution (accuracy) of the amplitude measurement must be sufficient to handle the desired dynamic range. The resolution is given in "bits". 8-bit audio is considered moderate fidelity while 16-bit audio is considered high fidelity.
.png)
Example of microphone wireless.
The bit rate of a digital signal is the resolution multiplied by the sampling rate. CD audio is 16 bits x 44.1KHz for a bit rate of 705,600 bits per second or 705.6K bits-per second. In the simplest form of digital transmission, the theoretical occupied bandwidth of such a signal would be equal to the bit rate. That is, to transmit CD-quality audio would require a bandwidth of 705.6KHz. In "real world" systems the occupied bandwidth would be even greater. Based on allowable deviation limits it is not possible to transmit such a signal. By comparison, cellular telephones use 8-bit resolution with a 6KHz sample rate.
By using special "coding" techniques the occupied bandwidth is only 30KHz. The resulting audio quality difference is obvious. In digital signal transmission it is possible to send morethan one bit per cycle by coding the bits into "symbols". The symbol rate is equal to the bit rate divided by the number of bits transmitted with each symbol. The
theoretical occupied bandwidth of a coded digital transmission is then equal to the "symbol" rate. For instance, a digital coding scheme that transmits two bits per symbol will have only half the occupied bandwidth of the CD example above.
It is further possible to reduce the bandwidth by using
compression schemes similar to those used in MiniDisc and MP3 recording devices. However, these are "lossy" techniques that eliminate some of the audio information. Nevertheless, when done properly, the audio quality can be quite good. Finally, the "reliability" of the digital signal transmission is also affected by the integrity of the radio path. Dropouts, interference, and multipath can cause loss of digital data. Extra bits are usually added to the signal for error correction, though this increases bandwidth slightly. One issue that is important in any digital scheme is latency, which is the signal delay that occurs whenever a signal passes through certain digital processes.
These include the A/D or D/A converters, the coding and decoding devices and any DSP that is applied in the analog signal path. Latency must be kept to a minimum to avoid distraction to the user and possible interference with non-delayed signal paths. The latency that is typical of cellular telephone circuits would be unacceptable in a live performance setting. Traditional analog transmitters and receivers use a moderate amount of bandwidth. Complex transmit/receive technologies are required to transmit digital information in a comparable bandwidth. Since spectrum is limited and increasingly crowded, successful digital transmission systems must have not only high audio quality but high bandwidth-efficiency as well.
The next digital application level employs DSP (Digital Signal Processing) to replace traditional analog companding circuits. An audio DSP circuit is used in the transmitter to optimize the input signal for transmission and a complementary audio DSP is used in the receiver to optimize the output signal. The radio transmission path is still in the analog domain. Benefits may include increased audio dynamic range, decreased companding artifacts, and wider frequency response.The highest level of digital implementation uses a fully digital transmission path.
The input signal is digitized in the transmitter and remains in the digital domain until the receiver output. It is even possible to output a digital signal from the receiver to subsequent digital equipment. Potential benefits of an all-digital wireless approach include both improved audio quality and improved radio transmission. However, the technical requirements are not trivial and the inevitable compromise between performance and cost requires some difficult decisions. In concept, fully digital wireless transmission is simple. Add an analog-to-digital (A/D) converter at the input of the transmitter. Transmit the resulting digital information to
the receiver.
Demodulate the digital information and add a complementary digital-to-analog (D/A) converter at the output of the receiver. The ultimate limitation lies in the amount of digital information that must be reliably transmitted for acceptable audio quality. In general, information transmission techniques (wired or wireless) must balance bandwidth limitations with hardware (and software) complexity. Bandwidth refers to the range of frequencies and/or amplitudes used to convey the information. In audio, a frequency range of 20- 20,000Hz and an amplitude range (dynamic range) of 120dB is perhaps the ultimate goal.
However, a frequency range of 300-3000Hz and a dynamic range of 30dB are sufficient for telephone-quality speech. As expected, high fidelity audio equipment tends to be more complex and costly than telephone equipment. In analog FM radio systems, audio fidelity is greatly dependent on allowable deviation, which is related to RF bandwidth: wider deviation increases occupied bandwidth. Walkie-talkies use less bandwidth than wireless microphones. Even so, bandwidth limitations necessitate the use of companders to achieve acceptable dynamic range in most high quality analog wireless systems.
The bandwidth required for a high fidelity digital wireless system depends on the amount of digital information transmitted and the transmission rate. In practice, the bandwidth is limited by physical and regulatory requirements. This effectively constrains the amount and rate of information that can be transmitted. Ultimately, the fidelity and reliability of a digital wireless system is limited by these same bandwidth restrictions. A digital representation of an analog audio signal is generated by sampling (measuring the amplitude of) the audio waveform at some rate. The rate must be equal to at least twice the highest audio frequency desired. The resolution (accuracy) of the amplitude measurement must be sufficient to handle the desired dynamic range. The resolution is given in "bits". 8-bit audio is considered moderate fidelity while 16-bit audio is considered high fidelity.
.png)
Example of microphone wireless.
The bit rate of a digital signal is the resolution multiplied by the sampling rate. CD audio is 16 bits x 44.1KHz for a bit rate of 705,600 bits per second or 705.6K bits-per second. In the simplest form of digital transmission, the theoretical occupied bandwidth of such a signal would be equal to the bit rate. That is, to transmit CD-quality audio would require a bandwidth of 705.6KHz. In "real world" systems the occupied bandwidth would be even greater. Based on allowable deviation limits it is not possible to transmit such a signal. By comparison, cellular telephones use 8-bit resolution with a 6KHz sample rate.
By using special "coding" techniques the occupied bandwidth is only 30KHz. The resulting audio quality difference is obvious. In digital signal transmission it is possible to send morethan one bit per cycle by coding the bits into "symbols". The symbol rate is equal to the bit rate divided by the number of bits transmitted with each symbol. The
theoretical occupied bandwidth of a coded digital transmission is then equal to the "symbol" rate. For instance, a digital coding scheme that transmits two bits per symbol will have only half the occupied bandwidth of the CD example above.
It is further possible to reduce the bandwidth by using
compression schemes similar to those used in MiniDisc and MP3 recording devices. However, these are "lossy" techniques that eliminate some of the audio information. Nevertheless, when done properly, the audio quality can be quite good. Finally, the "reliability" of the digital signal transmission is also affected by the integrity of the radio path. Dropouts, interference, and multipath can cause loss of digital data. Extra bits are usually added to the signal for error correction, though this increases bandwidth slightly. One issue that is important in any digital scheme is latency, which is the signal delay that occurs whenever a signal passes through certain digital processes.
These include the A/D or D/A converters, the coding and decoding devices and any DSP that is applied in the analog signal path. Latency must be kept to a minimum to avoid distraction to the user and possible interference with non-delayed signal paths. The latency that is typical of cellular telephone circuits would be unacceptable in a live performance setting. Traditional analog transmitters and receivers use a moderate amount of bandwidth. Complex transmit/receive technologies are required to transmit digital information in a comparable bandwidth. Since spectrum is limited and increasingly crowded, successful digital transmission systems must have not only high audio quality but high bandwidth-efficiency as well.
5. Range of Wireless
As an example, we can take wireless microphone as example. A logical question concerning wireless performance is the transmission range of various systems. Unfortunately, the answer is much more complicated than a simple distance measurement. Ultimately, the receiver must be able to pick up a "useable" signal from the transmitter. "Useable" means that the strength of the desired signal is within the sensitivity range of the receiver and further that it is sufficiently stronger than (or different from) undesirable signals and RF noise to produce an acceptable signal-to-noise ratio at the audio output of the receiver.
Elements that affect useability are the transmitter/antenna, the transmission path, the receiver/ antenna and RFI. Some characteristics of these elements are controllable, some are not. (See Figure 3-13.) Important transmitter characteristics are power output and antenna efficiency. Maximum power is limited by government regulations and battery capability. Antenna efficiency is limited by size and design. Recall that the efficiency of typical wireless transmitter antennas is fairly low, about 10% or less for VHF. This means that for a 50 mW VHF transmitter the effective radiated power (ERP) is less than 5 mW.
This may be further attenuated by proximity to the body or other lossy objects. Important receiver characteristics are antenna efficiency, receiver sensitivity and the ability of the receiver to reject unwanted signals and noise. Antenna efficiency is again limited by size and design but receiver antennas
tend to be much more efficient than transmitter antennas since they can be made large enough to be better tuned to the proper frequency. Other receiver characteristics are limited by design. Both elements are limited by cost.
The transmission path is characterized by distance, intervening obstructions and propagation effects. Losses due to these characteristics are generally frequency dependent: the higher the frequency the greater the loss. Once the operating frequency is chosen, only the path length and antenna locations are controllable. These are usually limited by the application itself. Under good conditions (line-of-sight) at a distance of about 100 ft. the field strength of the signal from a 50 mW transmitter is on the order of 1000 uV/m, well within the range of sensitivity of a typical receiver.
Finally, RFI is characterized by its spectrum, that is, its distribution of amplitude and frequency. It typically consists of both broadband noise and discrete frequencies. However, its strength can be comparable to or greater than the desired signal in poor conditions. Except for a few predictable sources it is largely uncontrollable. Rather than quote a specific maximum operating distance most manufacturers of wireless microphone systems give a "typical" range. For systems of the type discussed here (10-50 mW, VHF or UHF) the typical range may vary from 100 ft. to 1000 ft. The lower number represents a moderately severe environment while the upper figure might be achieved in absolute ideal conditions. Extremely poor conditions could result in a range of only 50 feet or less. It is impossible to accurately predict the range of an arbitrary wireless microphone system in an arbitrary application
Elements that affect useability are the transmitter/antenna, the transmission path, the receiver/ antenna and RFI. Some characteristics of these elements are controllable, some are not. (See Figure 3-13.) Important transmitter characteristics are power output and antenna efficiency. Maximum power is limited by government regulations and battery capability. Antenna efficiency is limited by size and design. Recall that the efficiency of typical wireless transmitter antennas is fairly low, about 10% or less for VHF. This means that for a 50 mW VHF transmitter the effective radiated power (ERP) is less than 5 mW.
This may be further attenuated by proximity to the body or other lossy objects. Important receiver characteristics are antenna efficiency, receiver sensitivity and the ability of the receiver to reject unwanted signals and noise. Antenna efficiency is again limited by size and design but receiver antennas
tend to be much more efficient than transmitter antennas since they can be made large enough to be better tuned to the proper frequency. Other receiver characteristics are limited by design. Both elements are limited by cost.
The transmission path is characterized by distance, intervening obstructions and propagation effects. Losses due to these characteristics are generally frequency dependent: the higher the frequency the greater the loss. Once the operating frequency is chosen, only the path length and antenna locations are controllable. These are usually limited by the application itself. Under good conditions (line-of-sight) at a distance of about 100 ft. the field strength of the signal from a 50 mW transmitter is on the order of 1000 uV/m, well within the range of sensitivity of a typical receiver.
Finally, RFI is characterized by its spectrum, that is, its distribution of amplitude and frequency. It typically consists of both broadband noise and discrete frequencies. However, its strength can be comparable to or greater than the desired signal in poor conditions. Except for a few predictable sources it is largely uncontrollable. Rather than quote a specific maximum operating distance most manufacturers of wireless microphone systems give a "typical" range. For systems of the type discussed here (10-50 mW, VHF or UHF) the typical range may vary from 100 ft. to 1000 ft. The lower number represents a moderately severe environment while the upper figure might be achieved in absolute ideal conditions. Extremely poor conditions could result in a range of only 50 feet or less. It is impossible to accurately predict the range of an arbitrary wireless microphone system in an arbitrary application
4. 4. Wireless Systems in the Post-DTV Transition Era
In the United States, the Federal Communications Commission (FCC) has been supervising the transition of broadcast television from its traditional analog format to an all-digital format (DTV). In the process, the commission has also been mandated to increase efficient use of TV spectrum and to increase the amount of spectrum available for public safety and other wireless services.
Therefore, the transition has provided both consolidation of the broadcast spectrum and the reallocation of the resulting open spectrum for other uses. The FCC has consigned all broadcast television into a "core" band, TV Channels 2-51. All existing TV stations above Channel 51 have migrated into the core band. The upper frequency limit of the broadcast band is now 698 MHz and (nearly) all full-power TV stations are now digital. All former television spectrum above Channel 51 (698-806 MHz) has now been reallocated for new services.
This spectrum is generally referred to as the “700 MHz” band. Within the 700 MHz band, most of this spectrum has been auctioned by competitive bidding to telecommunications companies while the rest has been set aside for public safety services. The telecommunications spectrum, 698-763 MHz (roughly TV 52-62) and 775-793 MHz (roughly TV 65-67), is being developed for various services such as broadband internet access, streaming video, and other digital data transmission. The public safety bands total 24 MHz in two "paired" bands: 763-775 MHz (roughly TV 63-64) for fixed transmitters and 793-805 MHz (roughly TV 68-69) for mobile transmitters.
For both statutory and practical reasons, the 700 MHz band is no longer available for use by wireless microphones or other wireless systems. Not only will they no longer be authorized in this spectrum, but also the interference from new services in this band will make operation of such systems unreliable at best. For this reason, manufacturers and distributors of wireless systems in the US market are no longer supplying wireless systems in the 700 MHz band. New wireless systems continue to be available mainly in the core television band (TV 2-51) and in a few other narrow frequency bands.
Therefore, the transition has provided both consolidation of the broadcast spectrum and the reallocation of the resulting open spectrum for other uses. The FCC has consigned all broadcast television into a "core" band, TV Channels 2-51. All existing TV stations above Channel 51 have migrated into the core band. The upper frequency limit of the broadcast band is now 698 MHz and (nearly) all full-power TV stations are now digital. All former television spectrum above Channel 51 (698-806 MHz) has now been reallocated for new services.
This spectrum is generally referred to as the “700 MHz” band. Within the 700 MHz band, most of this spectrum has been auctioned by competitive bidding to telecommunications companies while the rest has been set aside for public safety services. The telecommunications spectrum, 698-763 MHz (roughly TV 52-62) and 775-793 MHz (roughly TV 65-67), is being developed for various services such as broadband internet access, streaming video, and other digital data transmission. The public safety bands total 24 MHz in two "paired" bands: 763-775 MHz (roughly TV 63-64) for fixed transmitters and 793-805 MHz (roughly TV 68-69) for mobile transmitters.
For both statutory and practical reasons, the 700 MHz band is no longer available for use by wireless microphones or other wireless systems. Not only will they no longer be authorized in this spectrum, but also the interference from new services in this band will make operation of such systems unreliable at best. For this reason, manufacturers and distributors of wireless systems in the US market are no longer supplying wireless systems in the 700 MHz band. New wireless systems continue to be available mainly in the core television band (TV 2-51) and in a few other narrow frequency bands.
3. UHF vs. VHF
Like the VHF region, the UHF region contains several bands that are used for wireless microphone systems. However, certain physical, regulatory, and economic differences between VHF and UHF regions should be noted here. The primary physical characteristic of UHF radio waves is their much shorter wavelength (one-third to two-thirds of a meter). The visible consequence of this is the much shorter length of antennas for UHF wireless microphone systems. Quarter-wave antennas in the UHF range can be less than 10 cm.There are other consequences of the shorter UHF wavelength. One is reduced efficiency of radio wave human bodies.
This can result in potentially less range for a UHF signal compared to a VHF signal of the same radiated power. "Line-of-sight" operation is more important in the UHF range. Another consequence is the increased amount of radio wave reflections by smaller metal objects, resulting in comparatively more frequent and more severe interference due to multi-path (dropouts). However, diversity receivers are very effective in the UHF band, and
the required antenna spacing is minimal. Finally, the
signal loss in coaxial antenna cables is greater in the UHF
range. Amplifiers and/or low-loss cable may be required in UHF antenna systems. While the regulations for users and for licensing are essentially the same in the VHF and UHF bands (FCC Part 90), regulations for the equipment allow two potential differences.
For FM signals in the UHF band, greater occupied bandwidth is allowed. This effectively permits greater FM deviation, for potentially greater audio dynamic range. In addition, greater transmitter power is allowed (up to 250 mw). Finally, the available radio spectrum for UHF wireless microphone system use is five times greater than for high-band VHF. This allows for a much larger number of systems to be operated simultaneously.
In practice, the effectively greater deviation limits of UHF are not generally used because of the resulting reduction in the number of simultaneous systems that may operated: the corresponding increased occupied bandwidth of each system uses up more of the available frequency range. Also, use of increased transmitter power is rare due to the resulting severely decreased battery life and to the increased potential of mutual system interference. Even with limited deviation and power, however, the capability for an increased number of simultaneous systems is a significant benefit in certain applications. This is especially true since UHF systems can generally be used in conjunction with VHF systems at the same location without mutual interference.
The primary economic difference between VHF and UHF operation is the relatively higher cost of UHF equipment. Typically, it is more difficult and hence more expensive to design and manufacture UHF devices. In many ways this is a consequence of the behavior of high frequency (short wavelength) radio signals. This cost differential applies to antennas, cables, and other accessories as well as to the basic transmitter and receiver. Currently, though, economies of scale have reduced this premium substantially so that it is now possible to produce basic UHF systems at prices comparable to VHF. However, advanced features and performance tend to remain in the province of high-end UHF products.
This can result in potentially less range for a UHF signal compared to a VHF signal of the same radiated power. "Line-of-sight" operation is more important in the UHF range. Another consequence is the increased amount of radio wave reflections by smaller metal objects, resulting in comparatively more frequent and more severe interference due to multi-path (dropouts). However, diversity receivers are very effective in the UHF band, and
the required antenna spacing is minimal. Finally, the
signal loss in coaxial antenna cables is greater in the UHF
range. Amplifiers and/or low-loss cable may be required in UHF antenna systems. While the regulations for users and for licensing are essentially the same in the VHF and UHF bands (FCC Part 90), regulations for the equipment allow two potential differences.
For FM signals in the UHF band, greater occupied bandwidth is allowed. This effectively permits greater FM deviation, for potentially greater audio dynamic range. In addition, greater transmitter power is allowed (up to 250 mw). Finally, the available radio spectrum for UHF wireless microphone system use is five times greater than for high-band VHF. This allows for a much larger number of systems to be operated simultaneously.
In practice, the effectively greater deviation limits of UHF are not generally used because of the resulting reduction in the number of simultaneous systems that may operated: the corresponding increased occupied bandwidth of each system uses up more of the available frequency range. Also, use of increased transmitter power is rare due to the resulting severely decreased battery life and to the increased potential of mutual system interference. Even with limited deviation and power, however, the capability for an increased number of simultaneous systems is a significant benefit in certain applications. This is especially true since UHF systems can generally be used in conjunction with VHF systems at the same location without mutual interference.
The primary economic difference between VHF and UHF operation is the relatively higher cost of UHF equipment. Typically, it is more difficult and hence more expensive to design and manufacture UHF devices. In many ways this is a consequence of the behavior of high frequency (short wavelength) radio signals. This cost differential applies to antennas, cables, and other accessories as well as to the basic transmitter and receiver. Currently, though, economies of scale have reduced this premium substantially so that it is now possible to produce basic UHF systems at prices comparable to VHF. However, advanced features and performance tend to remain in the province of high-end UHF products.
2. The VHF Band
At the beginning of the low-band VHF range is the 49 MHz region, used not only by wireless microphones but also by cordless telephones, walkie-talkies, and radio controlled toys. 54-72 MHz is occupied by VHF television channels 2- 4. The 72 MHz area is used by "assistive listening" type wireless microphone systems. 76-88 MHz is assigned to VHF television channels 5 and 6. At the top, 88-108 MHz is the commercial FM radio broadcast band. All of these regions have been used at one time or another for wireless microphone systems. Allowable deviation limits (typically up to 15 KHz) can accommodate high-fidelity audio (the same as for FM broadcast).
The propagation of these waves through the air is very good, as is
their ability to pass through many non-metallic substances (a result of their relatively long wavelength). The most attractive feature of operation in this band is low equipment cost.
Except for assistive listening systems, however, lowband VHF is not recommended for serious applications. Due to the large number of primary and secondary users, and high levels of general radio frequency (RF) "noise," this band is prone to interference from many sources. Transmitter power is limited to less than 50 mW (except in the 72-76 MHz range where up to 1 watt is allowed for assistive listening systems). Finally, the minimum proper antenna size for units in this range can be over one meter long (one quarter of a five meter wave), which can severely
limit portability and/or efficiency.
Next is the high-band VHF range, widely used for professional applications, in which quality systems are available at a variety of prices. In the US, the high-band VHF range is divided into two bands, which are available to wireless microphone users. The first of these, from 169-172 MHz, includes eight specific frequencies designated by the FCC (Part 90.263b or just "Part 90") for wireless microphone use by general business. These frequencies are often referred to as "travelling frequencies," because they can (theoretically) be used throughout the US without concern for interference from broadcast television.
Legal limits ofdeviation (+/_12 KHz) allow high quality audio transmission. Once again, power is limited to 50 mw. Propagation characteristics are good, and antenna length is more manageable at about one-half meter for a quarter-wave type.
Unfortunately, the primary users in this band include many business band and government operations such as digital paging services, forestry, hydro-electric power stations, and the Coast Guard. Since the secondary user category is not restrictive, the potential for interference from both primary and other secondary users is always present. Also, general RF noise is still fairly strong in this band. In addition, due to the limitation of available frequency bandwidth, and the spacing of the prescribed eight frequencies, it is only feasible to operate, at most, two or three units simultaneously on travelling frequencies. Finally, these frequencies are not generally legal outside of the US and Canada.
The larger part of the high-band VHF region is 174- 216 MHz. This band is designated by the FCC for use by broadcasters and by commercial film/video producers ("Part 74"). The primary users of this band are VHF television channels 7-13.
Once again, high quality audio is possible within legal deviation limits (+15 kHz). The 50 mw power restriction is the same as for low-band, propagation losses are still minimal, and acceptable quarter-wave antenna sizes range down to less than one-half meter. The possibility of interference from other secondary users and general RF noise exists, but it is much less likely than for low-band frequencies. In addition, although this range includes powerful primary users (television channels 7-13), there are ample frequencies available (locally unused television channels) in almost any part of the US.
.png)
The propagation of these waves through the air is very good, as is
their ability to pass through many non-metallic substances (a result of their relatively long wavelength). The most attractive feature of operation in this band is low equipment cost.
Except for assistive listening systems, however, lowband VHF is not recommended for serious applications. Due to the large number of primary and secondary users, and high levels of general radio frequency (RF) "noise," this band is prone to interference from many sources. Transmitter power is limited to less than 50 mW (except in the 72-76 MHz range where up to 1 watt is allowed for assistive listening systems). Finally, the minimum proper antenna size for units in this range can be over one meter long (one quarter of a five meter wave), which can severely
limit portability and/or efficiency.
Next is the high-band VHF range, widely used for professional applications, in which quality systems are available at a variety of prices. In the US, the high-band VHF range is divided into two bands, which are available to wireless microphone users. The first of these, from 169-172 MHz, includes eight specific frequencies designated by the FCC (Part 90.263b or just "Part 90") for wireless microphone use by general business. These frequencies are often referred to as "travelling frequencies," because they can (theoretically) be used throughout the US without concern for interference from broadcast television.
Legal limits ofdeviation (+/_12 KHz) allow high quality audio transmission. Once again, power is limited to 50 mw. Propagation characteristics are good, and antenna length is more manageable at about one-half meter for a quarter-wave type.
Unfortunately, the primary users in this band include many business band and government operations such as digital paging services, forestry, hydro-electric power stations, and the Coast Guard. Since the secondary user category is not restrictive, the potential for interference from both primary and other secondary users is always present. Also, general RF noise is still fairly strong in this band. In addition, due to the limitation of available frequency bandwidth, and the spacing of the prescribed eight frequencies, it is only feasible to operate, at most, two or three units simultaneously on travelling frequencies. Finally, these frequencies are not generally legal outside of the US and Canada.
The larger part of the high-band VHF region is 174- 216 MHz. This band is designated by the FCC for use by broadcasters and by commercial film/video producers ("Part 74"). The primary users of this band are VHF television channels 7-13.
Once again, high quality audio is possible within legal deviation limits (+15 kHz). The 50 mw power restriction is the same as for low-band, propagation losses are still minimal, and acceptable quarter-wave antenna sizes range down to less than one-half meter. The possibility of interference from other secondary users and general RF noise exists, but it is much less likely than for low-band frequencies. In addition, although this range includes powerful primary users (television channels 7-13), there are ample frequencies available (locally unused television channels) in almost any part of the US.
.png)
1. Frequency Bands For Wireless Systems
Existing wireless microphone systems transmit and receive on a specific radio frequency, called the operating frequency. Individual radio frequencies are found in frequency "bands" which are
specific ranges of frequencies. Use of radio frequencies in the United States is regulated by the FCC (Federal Communication Commission). The FCC has designated certain bands of frequencies and certain frequencies in those bands for use by wireless microphones, as well
as by other services. In the US, the frequencies used for wireless audio systems may be grouped into four general bands or ranges: low-band VHF (49-108 MHz), high-band VHF (169-216 MHz), low-band UHF (450-698 MHz) and high-band UHF (900-952 MHz). VHF stands for "Very High Frequency," UHF stands for "Ultra High Frequency." (See Figure 3-1.)
.png)
The FCC further determines who can operate in each band and who has priority if more than one user is operating. "Primary" users include licensed broadcasters (radio and television) and commercial communications services (2-way radio, pagers, and cellular telephones). Wireless microphone operators are always considered to be "secondary" users. In general, priority is given to primary users: secondary users may not interfere with primary users, and secondary users may be subject to interference from primary users. On the subject of licensing, it should be noted that
while manufacturers must be licensed by the FCC to sell wireless equipment, it is the responsibility of the operator to observe FCC regulations regarding their actual use. We will briefly describe each band and its advantages and disadvantages for wireless microphone system operation, based on the designated users of the band, the physical characteristics of the band, and the regulatory limitations of the band
specific ranges of frequencies. Use of radio frequencies in the United States is regulated by the FCC (Federal Communication Commission). The FCC has designated certain bands of frequencies and certain frequencies in those bands for use by wireless microphones, as well
as by other services. In the US, the frequencies used for wireless audio systems may be grouped into four general bands or ranges: low-band VHF (49-108 MHz), high-band VHF (169-216 MHz), low-band UHF (450-698 MHz) and high-band UHF (900-952 MHz). VHF stands for "Very High Frequency," UHF stands for "Ultra High Frequency." (See Figure 3-1.)
.png)
The FCC further determines who can operate in each band and who has priority if more than one user is operating. "Primary" users include licensed broadcasters (radio and television) and commercial communications services (2-way radio, pagers, and cellular telephones). Wireless microphone operators are always considered to be "secondary" users. In general, priority is given to primary users: secondary users may not interfere with primary users, and secondary users may be subject to interference from primary users. On the subject of licensing, it should be noted that
while manufacturers must be licensed by the FCC to sell wireless equipment, it is the responsibility of the operator to observe FCC regulations regarding their actual use. We will briefly describe each band and its advantages and disadvantages for wireless microphone system operation, based on the designated users of the band, the physical characteristics of the band, and the regulatory limitations of the band
Other Broadband Services
National broadband wireless data service providers use a different variation
on spread spectrum technology and a different range of radio frequencies.
The broadband wireless services provided by Sprint, AT&T, and Verizon
all share the frequencies around 800 MHz and 1,900 MHz used by those
companies’ digital mobile telephone networks. WiMAX services, such as
Clearwire, use signals in the 2.3 to 2.5 GHz and 3.5 GHz bands.
Many new radio frequencies may open up for mobile telephone and
data services in the United States after February 17, 2009, when all the
existing analog television stations move to new digital channels, and the
old VHF channels will close down. The newly vacant radio spectrum will
become available for new services, including broadband wireless data.
on spread spectrum technology and a different range of radio frequencies.
The broadband wireless services provided by Sprint, AT&T, and Verizon
all share the frequencies around 800 MHz and 1,900 MHz used by those
companies’ digital mobile telephone networks. WiMAX services, such as
Clearwire, use signals in the 2.3 to 2.5 GHz and 3.5 GHz bands.
Many new radio frequencies may open up for mobile telephone and
data services in the United States after February 17, 2009, when all the
existing analog television stations move to new digital channels, and the
old VHF channels will close down. The newly vacant radio spectrum will
become available for new services, including broadband wireless data.
BLUETOOTH
5 Bluetooth
Bluetooth is the other type of wireless networking technology that we ought
to describe. Bluetooth uses radio signals to replace the wires and cables that
connect a computer or a mobile telephone to peripheral devices, such as a
keyboard, a mouse, or a set of speakers. You can also use Bluetooth to transfer
data between a computer and a mobile telephone, smartphone, BlackBerry, or
other PDA (personal digital assistant).
Bluetooth is an FHSS system that splits the radio signal into tiny pieces.
It moves among 79 different frequencies 1,600 times per second in the same
unlicensed 2.4 GHz range as 802.11b and 802.11g Wi-Fi services.
Bluetooth is not practical for connecting a computer to the Internet
because it’s slow (the maximum data transfer rate is only about 700Kbps),
and it has a very limited signal range (most often about 33 feet, or 10 meters,
or less).
In order to prevent interference between Bluetooth and Wi-Fi signals,
many computers that use both technologies (including the widely used Intel
Centrino chip set) coordinate the two services. When either module is active,
it notifies the other, and the active service takes priority. This coordinated
operation is slightly slower than either service operating alone, but the
difference is insignificant.
Bluetooth is the other type of wireless networking technology that we ought
to describe. Bluetooth uses radio signals to replace the wires and cables that
connect a computer or a mobile telephone to peripheral devices, such as a
keyboard, a mouse, or a set of speakers. You can also use Bluetooth to transfer
data between a computer and a mobile telephone, smartphone, BlackBerry, or
other PDA (personal digital assistant).
Bluetooth is an FHSS system that splits the radio signal into tiny pieces.
It moves among 79 different frequencies 1,600 times per second in the same
unlicensed 2.4 GHz range as 802.11b and 802.11g Wi-Fi services.
Bluetooth is not practical for connecting a computer to the Internet
because it’s slow (the maximum data transfer rate is only about 700Kbps),
and it has a very limited signal range (most often about 33 feet, or 10 meters,
or less).
In order to prevent interference between Bluetooth and Wi-Fi signals,
many computers that use both technologies (including the widely used Intel
Centrino chip set) coordinate the two services. When either module is active,
it notifies the other, and the active service takes priority. This coordinated
operation is slightly slower than either service operating alone, but the
difference is insignificant.
WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is yet another
method for distributing broadband wireless data over wide geographic areas.
It’s a metropolitan area network service that typically uses one or more base
stations that can each provide service to users within a 30-mile radius. The
IEEE 802.16 specification contains the technical details of WiMAX networks.
In the United States, the earliest WiMAX services were offered by
Clearwire as a wireless alternative to DSL and cable broadband Internet
access in fixed locations (such as homes and businesses), but mobile
WiMAX access is not far behind. By early 2008, Clearwire plans to offer
access to their wireless networks through an adapter on a PC Card. When
those adapters become available, WiMAX, 3G cellular data services, and
metropolitan Wi-Fi networks will compete for the same commercial niche:
wireless access to the Internet through a service that covers an entire metropolitan area.
Each WiMAX service provider uses one or more licensed operating frequencies somewhere between 2 GHz and 11 GHz. A WiMAX link can transfer
data (including handshaking and other overhead) at up to 70Mbps, but most
commercial WiMAX services are significantly slower than that. And as more
and more users share a single WiMAX tower and base station, some users
report that their signal quality deteriorates.
Unlike the cellular broadband wireless data services that piggyback on
existing mobile telephone networks, WiMAX is a separate radio system that is
designed to either supplement or replace the existing broadband Internet
distribution systems. In practice, WiMAX competes with both 3G wireless
services and with Internet service providers that distribute Internet access to
fixed locations through telephone lines and cable television utilities. Home
and business subscribers to a WiMAX service usually use either a wired LAN
or Wi-Fi to distribute the network within their buildings. Figure 2-9 shows a
typical WiMAX network.
.png)
Figure 2.9
method for distributing broadband wireless data over wide geographic areas.
It’s a metropolitan area network service that typically uses one or more base
stations that can each provide service to users within a 30-mile radius. The
IEEE 802.16 specification contains the technical details of WiMAX networks.
In the United States, the earliest WiMAX services were offered by
Clearwire as a wireless alternative to DSL and cable broadband Internet
access in fixed locations (such as homes and businesses), but mobile
WiMAX access is not far behind. By early 2008, Clearwire plans to offer
access to their wireless networks through an adapter on a PC Card. When
those adapters become available, WiMAX, 3G cellular data services, and
metropolitan Wi-Fi networks will compete for the same commercial niche:
wireless access to the Internet through a service that covers an entire metropolitan area.
Each WiMAX service provider uses one or more licensed operating frequencies somewhere between 2 GHz and 11 GHz. A WiMAX link can transfer
data (including handshaking and other overhead) at up to 70Mbps, but most
commercial WiMAX services are significantly slower than that. And as more
and more users share a single WiMAX tower and base station, some users
report that their signal quality deteriorates.
Unlike the cellular broadband wireless data services that piggyback on
existing mobile telephone networks, WiMAX is a separate radio system that is
designed to either supplement or replace the existing broadband Internet
distribution systems. In practice, WiMAX competes with both 3G wireless
services and with Internet service providers that distribute Internet access to
fixed locations through telephone lines and cable television utilities. Home
and business subscribers to a WiMAX service usually use either a wired LAN
or Wi-Fi to distribute the network within their buildings. Figure 2-9 shows a
typical WiMAX network.
.png)
Figure 2.9
Cellular Mobile Wireless Services
Several broadband wireless data services are extensions of cellular mobile
telephone technology. You might see them described as 3G services because
they’re based on the third generation of cellular telephone technology. If
you have been using a mobile telephone for more than a year or two, you
probably remember that the earliest phones were only good for voice calls,
but as each new generation was introduced, your mobile carrier offered
more and better features. Table 2-2 describes the various generations.
For people who use their computers away from their home or office, the
great advantage of a mobile broadband service is that it covers a much wider
territory than any Wi-Fi base station; you can connect your computer to the
Internet without the need to search for a new hot spot and use a different
access account in each new location, and you can even keep the same connection
alive in a moving vehicle. Each of the major wireless broadband services
offers coverage in most metropolitan areas and much of the countryside
between cities.
Table 2 :- Cellular Mobile Telephone Generations
Name Features
1G Analog voice communication only
2G System can handle more calls
Digital voice
Uses less power
Less background noise
Digital data
Simple text messages
Email
2.5G Packet-switched signaling
Faster data transfer (up to 144Kbps)
Supports relatively slow Internet connections
3G Even more calls at the same time
Much faster data transfer rates (up to 2.4Mbps)
Broadband Internet
Video and music
4G Based on Internet technology
Packet signaling
Very high speed (100Mbps–1Gbps)
Will combine telephone, computer, and other technologies
telephone technology. You might see them described as 3G services because
they’re based on the third generation of cellular telephone technology. If
you have been using a mobile telephone for more than a year or two, you
probably remember that the earliest phones were only good for voice calls,
but as each new generation was introduced, your mobile carrier offered
more and better features. Table 2-2 describes the various generations.
For people who use their computers away from their home or office, the
great advantage of a mobile broadband service is that it covers a much wider
territory than any Wi-Fi base station; you can connect your computer to the
Internet without the need to search for a new hot spot and use a different
access account in each new location, and you can even keep the same connection
alive in a moving vehicle. Each of the major wireless broadband services
offers coverage in most metropolitan areas and much of the countryside
between cities.
Table 2 :- Cellular Mobile Telephone Generations
Name Features
1G Analog voice communication only
2G System can handle more calls
Digital voice
Uses less power
Less background noise
Digital data
Simple text messages
2.5G Packet-switched signaling
Faster data transfer (up to 144Kbps)
Supports relatively slow Internet connections
3G Even more calls at the same time
Much faster data transfer rates (up to 2.4Mbps)
Broadband Internet
Video and music
4G Based on Internet technology
Packet signaling
Very high speed (100Mbps–1Gbps)
Will combine telephone, computer, and other technologies
Metropolitan Wi-Fi Services
In some metropolitan areas, a large number of interconnected Wi-Fi base
stations are being installed by either local government agencies or private
businesses to provide wireless service throughout an entire region or in
selected neighborhoods as an economical alternative to cable and telephone
(DSL) services. The base stations for these services are often mounted on
utility poles or rooftops.
These same networks might also provide a variety of special data services
to the local government and major subscribers. For example, the local natural
gas, electric, and water utilities could add small Wi-Fi adapters to their meters
and use the system to send readings once a month. And city buses might
have transponders that report their locations to a central tracking system,
like the one in Seattle at http://busview.org/busview_launch.jsp, as shown in
Figure 2-8.
It’s not yet clear whether these city-wide Wi-Fi services will be able to
overcome possible interference problems and competition from other
wireless data alternatives, or whether they will attract enough business to
remain viable. But if they do, any computer within the coverage area that
has a Wi-Fi adapter should detect the signal and have access to a broadband
Internet connection.
.png)
Figure 2-8: Wireless technology tracks city buses in Seattle and
reports locations on a website.
stations are being installed by either local government agencies or private
businesses to provide wireless service throughout an entire region or in
selected neighborhoods as an economical alternative to cable and telephone
(DSL) services. The base stations for these services are often mounted on
utility poles or rooftops.
These same networks might also provide a variety of special data services
to the local government and major subscribers. For example, the local natural
gas, electric, and water utilities could add small Wi-Fi adapters to their meters
and use the system to send readings once a month. And city buses might
have transponders that report their locations to a central tracking system,
like the one in Seattle at http://busview.org/busview_launch.jsp, as shown in
Figure 2-8.
It’s not yet clear whether these city-wide Wi-Fi services will be able to
overcome possible interference problems and competition from other
wireless data alternatives, or whether they will attract enough business to
remain viable. But if they do, any computer within the coverage area that
has a Wi-Fi adapter should detect the signal and have access to a broadband
Internet connection.
.png)
Figure 2-8: Wireless technology tracks city buses in Seattle and
reports locations on a website.
Wi-Fi
The IEEE (Institute of Electrical and Electronics Engineers) has produced a
set of standards and specifications for wireless networks under the title IEEE
802.11 that define the formats and structures of the relatively short-range
signals that provide Wi-Fi service. The original 802.11 standard (without any
letter at the end) was released in 1997. It covers several types of wireless media:
two kinds of radio transmissions and networks that use infrared light.
The 802.11b standard provides additional specifications for wireless Ethernet
networks. A related document, IEEE 802.11a, describes wireless networks
that operate at higher speeds on different radio frequencies. Still other
802.11 radio networking standards with other letters are also available or
moving toward public release.
The specifications in widest use today are 802.11a, 802.11b, and 802.11g.
They’re the de facto standards used by just about every wireless Ethernet
LAN that you are likely to encounter in offices and public spaces and in most
home networks. It’s worth the trouble to keep an eye on the progress of those
other standards, but for the moment, 802.11a and 802.11g are the ones to
use for short-range wireless networks, especially if you’re expecting to connect
to networks where you don’t control all the hardware yourself.
The 802.11n standard is the next one in the pipeline, and when it’s
released, it will replace both 802.11b and 802.11g because it’s faster, more
secure, and more reliable. The older standards will still work, so new Wi-Fi
equipment will support all three (often along with 802.11a, which uses
different radio frequencies) and automatically match your network interface
to the signals it detects from each base station.
There are two more names in the alphabet soup of wireless LAN
standards that you ought to know about: WECA and Wi-Fi. WECA (Wireless
Ethernet Compatibility Alliance) is an industry group that includes all of the
major manufacturers of wireless Ethernet equipment. Their twin missions
are to test and certify that the wireless network devices from all of their
member companies can operate together in the same network, and to
promote 802.11 networks as the worldwide standard for wireless LANs.
WECA’s marketing geniuses have adopted the more friendly name of Wi-Fi
(short for wireless fidelity) for the 802.11 specifications.
Once or twice per year, the Wi-Fi Alliance conducts an “interoperability
bake-off ” where engineers from many hardware manufacturers confirm
that their hardware will communicate correctly with equipment from other
suppliers. Network equipment that carries a Wi-Fi logo has been certified
by the Wi-Fi Alliance to meet the relevant standards and to pass interoperability
tests. Figure 2-7 shows one version of the Wi-Fi logo.
.png)
Figure 2.7
Wi-Fi was originally intended to be a wireless extension of a wired LAN, so the distances between Wi-Fi base stations and the computers that communicate through them are limited to about 100 feet (35 meters) indoors or up to 300 feet (100 meters) outdoors, assuming there are no obstructions between the access point and the computer. When 802.11n equipment becomes available, it will support connections between computers and base stations at least as far apart as the older Wi-Fi versions. There are ways to extend the range of a Wi-Fi signal, but those techniques require special equipment and careful installation.
Because most Wi-Fi signals have such a limited range, you must find
new access point, or hot spot, and set up a new connection every time you move your computer to a new location. And because many Wi-Fi access points don’t permit strangers to connect through them, you may have to establish a separate account for each location. The Wi-Fi networks described in this book follow the 802.11a, b, and g standards, but much of the same information will also apply to the new 802.11n networks when they become available.
set of standards and specifications for wireless networks under the title IEEE
802.11 that define the formats and structures of the relatively short-range
signals that provide Wi-Fi service. The original 802.11 standard (without any
letter at the end) was released in 1997. It covers several types of wireless media:
two kinds of radio transmissions and networks that use infrared light.
The 802.11b standard provides additional specifications for wireless Ethernet
networks. A related document, IEEE 802.11a, describes wireless networks
that operate at higher speeds on different radio frequencies. Still other
802.11 radio networking standards with other letters are also available or
moving toward public release.
The specifications in widest use today are 802.11a, 802.11b, and 802.11g.
They’re the de facto standards used by just about every wireless Ethernet
LAN that you are likely to encounter in offices and public spaces and in most
home networks. It’s worth the trouble to keep an eye on the progress of those
other standards, but for the moment, 802.11a and 802.11g are the ones to
use for short-range wireless networks, especially if you’re expecting to connect
to networks where you don’t control all the hardware yourself.
The 802.11n standard is the next one in the pipeline, and when it’s
released, it will replace both 802.11b and 802.11g because it’s faster, more
secure, and more reliable. The older standards will still work, so new Wi-Fi
equipment will support all three (often along with 802.11a, which uses
different radio frequencies) and automatically match your network interface
to the signals it detects from each base station.
There are two more names in the alphabet soup of wireless LAN
standards that you ought to know about: WECA and Wi-Fi. WECA (Wireless
Ethernet Compatibility Alliance) is an industry group that includes all of the
major manufacturers of wireless Ethernet equipment. Their twin missions
are to test and certify that the wireless network devices from all of their
member companies can operate together in the same network, and to
promote 802.11 networks as the worldwide standard for wireless LANs.
WECA’s marketing geniuses have adopted the more friendly name of Wi-Fi
(short for wireless fidelity) for the 802.11 specifications.
Once or twice per year, the Wi-Fi Alliance conducts an “interoperability
bake-off ” where engineers from many hardware manufacturers confirm
that their hardware will communicate correctly with equipment from other
suppliers. Network equipment that carries a Wi-Fi logo has been certified
by the Wi-Fi Alliance to meet the relevant standards and to pass interoperability
tests. Figure 2-7 shows one version of the Wi-Fi logo.
.png)
Figure 2.7
Wi-Fi was originally intended to be a wireless extension of a wired LAN, so the distances between Wi-Fi base stations and the computers that communicate through them are limited to about 100 feet (35 meters) indoors or up to 300 feet (100 meters) outdoors, assuming there are no obstructions between the access point and the computer. When 802.11n equipment becomes available, it will support connections between computers and base stations at least as far apart as the older Wi-Fi versions. There are ways to extend the range of a Wi-Fi signal, but those techniques require special equipment and careful installation.
Because most Wi-Fi signals have such a limited range, you must find
new access point, or hot spot, and set up a new connection every time you move your computer to a new location. And because many Wi-Fi access points don’t permit strangers to connect through them, you may have to establish a separate account for each location. The Wi-Fi networks described in this book follow the 802.11a, b, and g standards, but much of the same information will also apply to the new 802.11n networks when they become available.
Wireless Data Services
Because radio signals move through the air, you can set up a network connection
from any place within range of the network base station’s transmitter;
it’s not necessary to use a telephone line, television cable, or some other
dedicated wiring to connect your computer to the network. Just turn on the
radio connected to the computer and it will find the network signal. Therefore,
a radio (or wireless) network connection is often a lot more convenient
than a wired one.
This is not to say that wireless is always the best choice. A wired network
is usually more secure than a wireless system because it’s a lot more difficult
for unauthorized eavesdroppers and other snoops to monitor data as it
moves through the network, and a wired link doesn’t require as many complex
negotiations between the sender and receiver on protocols and so forth. In
an environment where your computer never moves away from your desk and
there are no physical obstacles between the computer and the network access
point, it’s often easier to install a data cable between the computer and a
modem.
So now we have a bunch of radio transmitters and receivers that all
operate on the same frequencies and all use the same kind of modulation.
(Modulation is the method a radio uses to add some kind of content, such as
voice or digital data, to a radio wave.) The next step is to send some network
data through those radios. Several different wireless data systems and services
are available to connect computers and other devices to local networks and
to the Internet, including Wi-Fi, WiMAX, and a handful of services based on
the latest generations of cellular mobile telephone technology.
from any place within range of the network base station’s transmitter;
it’s not necessary to use a telephone line, television cable, or some other
dedicated wiring to connect your computer to the network. Just turn on the
radio connected to the computer and it will find the network signal. Therefore,
a radio (or wireless) network connection is often a lot more convenient
than a wired one.
This is not to say that wireless is always the best choice. A wired network
is usually more secure than a wireless system because it’s a lot more difficult
for unauthorized eavesdroppers and other snoops to monitor data as it
moves through the network, and a wired link doesn’t require as many complex
negotiations between the sender and receiver on protocols and so forth. In
an environment where your computer never moves away from your desk and
there are no physical obstacles between the computer and the network access
point, it’s often easier to install a data cable between the computer and a
modem.
So now we have a bunch of radio transmitters and receivers that all
operate on the same frequencies and all use the same kind of modulation.
(Modulation is the method a radio uses to add some kind of content, such as
voice or digital data, to a radio wave.) The next step is to send some network
data through those radios. Several different wireless data systems and services
are available to connect computers and other devices to local networks and
to the Internet, including Wi-Fi, WiMAX, and a handful of services based on
the latest generations of cellular mobile telephone technology.
Wireless Data Services
Because radio signals move through the air, you can set up a network connection
from any place within range of the network base station’s transmitter;
it’s not necessary to use a telephone line, television cable, or some other
dedicated wiring to connect your computer to the network. Just turn on the
radio connected to the computer and it will find the network signal. Therefore,
a radio (or wireless) network connection is often a lot more convenient
than a wired one.
This is not to say that wireless is always the best choice. A wired network
is usually more secure than a wireless system because it’s a lot more difficult
for unauthorized eavesdroppers and other snoops to monitor data as it
moves through the network, and a wired link doesn’t require as many complex
negotiations between the sender and receiver on protocols and so forth. In
an environment where your computer never moves away from your desk and
there are no physical obstacles between the computer and the network access
point, it’s often easier to install a data cable between the computer and a
modem.
So now we have a bunch of radio transmitters and receivers that all
operate on the same frequencies and all use the same kind of modulation.
(Modulation is the method a radio uses to add some kind of content, such as
voice or digital data, to a radio wave.) The next step is to send some network
data through those radios. Several different wireless data systems and services
are available to connect computers and other devices to local networks and
to the Internet, including Wi-Fi, WiMAX, and a handful of services based on
the latest generations of cellular mobile telephone technology.
from any place within range of the network base station’s transmitter;
it’s not necessary to use a telephone line, television cable, or some other
dedicated wiring to connect your computer to the network. Just turn on the
radio connected to the computer and it will find the network signal. Therefore,
a radio (or wireless) network connection is often a lot more convenient
than a wired one.
This is not to say that wireless is always the best choice. A wired network
is usually more secure than a wireless system because it’s a lot more difficult
for unauthorized eavesdroppers and other snoops to monitor data as it
moves through the network, and a wired link doesn’t require as many complex
negotiations between the sender and receiver on protocols and so forth. In
an environment where your computer never moves away from your desk and
there are no physical obstacles between the computer and the network access
point, it’s often easier to install a data cable between the computer and a
modem.
So now we have a bunch of radio transmitters and receivers that all
operate on the same frequencies and all use the same kind of modulation.
(Modulation is the method a radio uses to add some kind of content, such as
voice or digital data, to a radio wave.) The next step is to send some network
data through those radios. Several different wireless data systems and services
are available to connect computers and other devices to local networks and
to the Internet, including Wi-Fi, WiMAX, and a handful of services based on
the latest generations of cellular mobile telephone technology.
Benefits Of Wireless
Wireless broadband provides Internet access to mobile devices in addition to
allowing network operators to extend their networks beyond the range of
their wired connections. For our purposes, two-way radio is the most sensible
approach to wireless broadband, but other methods (such as infrared light
or visible signaling) are also possible. Connecting your computer to the
Internet (or a local network) by radio offers several advantages over connecting
the same computer through a wired connection.
First, wireless provides convenient access for portable computers; it’s not necessary to find a cable or network data outlet. And second, it allows a user to make a connection from more than one location and to maintain a connection as the user moves from place to place. For network managers, a wireless connection makes it possible to distribute access to a network without the need to string wires or cut holes through walls. In practice, access without cables means that the owner of a laptop or other portable computer can walk into a classroom, a coffee shop, or a library and connect to the Internet by simply turning on the computer and running a communication program. Depending on the type of wireless network you’re using, you might also be able to maintain the same connection in a moving vehicle.
When you’re installing your own network, it’s often easier to use Wi-Fi
links to extend your network and your Internet connection to other rooms
because a wired system requires a physical path for the cables between the
network router or switch and each computer. Unless you can route those
cables through a false ceiling or some other existing channel, this almost
always means that you must cut holes in your walls for data connectors and
feed wires inside the walls and under the floors. A radio signal that passes
through those same walls is often a lot neater and easier.
allowing network operators to extend their networks beyond the range of
their wired connections. For our purposes, two-way radio is the most sensible
approach to wireless broadband, but other methods (such as infrared light
or visible signaling) are also possible. Connecting your computer to the
Internet (or a local network) by radio offers several advantages over connecting
the same computer through a wired connection.
First, wireless provides convenient access for portable computers; it’s not necessary to find a cable or network data outlet. And second, it allows a user to make a connection from more than one location and to maintain a connection as the user moves from place to place. For network managers, a wireless connection makes it possible to distribute access to a network without the need to string wires or cut holes through walls. In practice, access without cables means that the owner of a laptop or other portable computer can walk into a classroom, a coffee shop, or a library and connect to the Internet by simply turning on the computer and running a communication program. Depending on the type of wireless network you’re using, you might also be able to maintain the same connection in a moving vehicle.
When you’re installing your own network, it’s often easier to use Wi-Fi
links to extend your network and your Internet connection to other rooms
because a wired system requires a physical path for the cables between the
network router or switch and each computer. Unless you can route those
cables through a false ceiling or some other existing channel, this almost
always means that you must cut holes in your walls for data connectors and
feed wires inside the walls and under the floors. A radio signal that passes
through those same walls is often a lot neater and easier.
2) BLUETOOTH
5.1 Overview: Unwiring USB
Imagine if all the devices in a home office -- such as printer, scanner, external hard drive, and digital camera -- could be connected to your PC without any wires. Imagine if all the components for an entire home entertainment center could be set up and connected without a single wire. Imagine if digital pictures could be transferred to a photo print kiosk for instant printing without the need for a cable. These are just some of the possible scenarios for high-speed wireless USB (WUSB) connectivity, the latest technology developed to bring even greater convenience and mobility to devices.
Universal serial bus (USB) technology has been a popular connection type for PCs and it's migrating into consumer electronic (CE) and mobile devices. Now this high-speed and effective connection interface is unwiring to provide the functionality of wired USB without the burden of cables. This next iteration of USB technology is the focus of the new Wireless USB Promoter Group, which will define the specifications that will eventually provide standards for the technology.
5.2 WUSB Topology
The fundamental relationship in WUSB is a hub and spoke topology, as shown in Figure 1. In this topology, the host initiates all the data traffic among the devices connected to it, allotting time slots and data bandwidth to each device connected. These relationships are referred to as clusters. The connections are point-to-point and directed between the WUSB host and WUSB device.
.png)
Figure 1 -- WUSB topology
The WUSB host can logically connect to a maximum of 127 WUSB devices, considered an informal WUSB cluster. WUSB clusters coexist within an overlapping spatial environment with minimum interference, thus allowing a number of other WUSB clusters to be present within the same radio cell.
Topology will support a dual role model where a device can also support limited host capabilities. This model allows mobile devices to access services with a central host supporting the services (i.e., printers and viewers). This model also allows a device to access data outside an existing cluster it may currently be connected to by creating a second cluster as a limited host.
Additionally, high spatial capacity in small areas is needed to enable multiple device access to high bandwidth concurrently. Multiple channel activities may take place within a given area. The topology will support multiple clusters in the same area. The number of clusters to be supported is still being determined.
5.3 Performance
WUSB performance at launch will provide adequate bandwidth to meet the requirements of a typical user experience with wired connections. The 480 Mbps initial target bandwidth of WUSB is comparable to the current wired USB 2.0 standard. With 480 Mbps being the initial target, WUSB specifications will allow for generation steps of data throughput as the ultra wideband radio evolves and with future process technologies, exceeding limits of 1 Gbps.
The specification is intended for WUSB to operate as a wire replacement with targeted usage models for cluster connectivity to the host and device-to-device connectivity at less than 10 meters. The interface will support quality delivery of rich digital multimedia formats, including audio and video, and will be capable of high rate streaming (isochronous transfers
Figure 2 -- Consumer Usage Models
Imagine if all the devices in a home office -- such as printer, scanner, external hard drive, and digital camera -- could be connected to your PC without any wires. Imagine if all the components for an entire home entertainment center could be set up and connected without a single wire. Imagine if digital pictures could be transferred to a photo print kiosk for instant printing without the need for a cable. These are just some of the possible scenarios for high-speed wireless USB (WUSB) connectivity, the latest technology developed to bring even greater convenience and mobility to devices.
Universal serial bus (USB) technology has been a popular connection type for PCs and it's migrating into consumer electronic (CE) and mobile devices. Now this high-speed and effective connection interface is unwiring to provide the functionality of wired USB without the burden of cables. This next iteration of USB technology is the focus of the new Wireless USB Promoter Group, which will define the specifications that will eventually provide standards for the technology.
5.2 WUSB Topology
The fundamental relationship in WUSB is a hub and spoke topology, as shown in Figure 1. In this topology, the host initiates all the data traffic among the devices connected to it, allotting time slots and data bandwidth to each device connected. These relationships are referred to as clusters. The connections are point-to-point and directed between the WUSB host and WUSB device.
.png)
Figure 1 -- WUSB topology
The WUSB host can logically connect to a maximum of 127 WUSB devices, considered an informal WUSB cluster. WUSB clusters coexist within an overlapping spatial environment with minimum interference, thus allowing a number of other WUSB clusters to be present within the same radio cell.
Topology will support a dual role model where a device can also support limited host capabilities. This model allows mobile devices to access services with a central host supporting the services (i.e., printers and viewers). This model also allows a device to access data outside an existing cluster it may currently be connected to by creating a second cluster as a limited host.
Additionally, high spatial capacity in small areas is needed to enable multiple device access to high bandwidth concurrently. Multiple channel activities may take place within a given area. The topology will support multiple clusters in the same area. The number of clusters to be supported is still being determined.
5.3 Performance
WUSB performance at launch will provide adequate bandwidth to meet the requirements of a typical user experience with wired connections. The 480 Mbps initial target bandwidth of WUSB is comparable to the current wired USB 2.0 standard. With 480 Mbps being the initial target, WUSB specifications will allow for generation steps of data throughput as the ultra wideband radio evolves and with future process technologies, exceeding limits of 1 Gbps.
The specification is intended for WUSB to operate as a wire replacement with targeted usage models for cluster connectivity to the host and device-to-device connectivity at less than 10 meters. The interface will support quality delivery of rich digital multimedia formats, including audio and video, and will be capable of high rate streaming (isochronous transfers
Figure 2 -- Consumer Usage Models
BLUETOOTH
Bluetooth is a simple type of wireless networking that allows the formation of a small network with up to eight devices being connected at once. Such devices would include PDAs, Laptops, Mobile Phones and Personal Computers. However, Bluetooth may also be found in keyboards, mice, headsets and mobile phone hands-free kits, amongst others. It was originally invented by Ericsson in 1994. In 1998 the Bluetooth SIG (Special Interest Group) was formed by a small number of major companies – Ericsson, Nokia, Intel and Toshiba – to help each other develop and promote the technology. Bluetooth falls under personal area networking since it is has a very short range – 30 to 300 feet. This sort of range adds to the security of such a technology in that if someone wanted to sniff your connection they would not only need special equipment but they would have to be fairly close to you. The main features of Bluetooth are that unlike Infra Red, the signal is not affected by walls it uses radio technology, it is not very expensive, and has little power consumption.
WWANS: Wireless Wide Area Networks
These types of networks can be maintained over large areas, such as cities or countries, via multiple satellite systems or antenna sites looked after by an ISP. These types of systems are referred to as 2G (2nd Generation) systems.
NETWORK METRES
Personal Area Network 0-10
Local Area Network 0-100
Wide Area Network 0-10 000
Table 1:-type of wireless asnd it range
NETWORK METRES
Personal Area Network 0-10
Local Area Network 0-100
Wide Area Network 0-10 000
Table 1:-type of wireless asnd it range
WMANS: Wireless Metropolitan Area Networks
This technology allows the connection of multiple networks in a metropolitan area such as different buildings in a city, which can be an alternative or backup to laying copper or fibre cabling.
WPANS: Wireless Personal Area Networks
The two current technologies for wireless personal area networks are Infra Red (IR) and Bluetooth (IEEE 802.15). These will allow the connectivity of personal devices within an area of about 30 feet. However, IR requires a direct line of site and the range is less.
WLANS: Wireless Local Area Networks
WLANS allow users in a local area, such as a university campus or library, to form a network or gain access to the internet. A temporary network can be formed by a small number of users without the need of an access point; given that they do not need access to network resources.
introduction to wireless
Whether it’s because you have made a call using a mobile phone, received a message on your pager, checked your email from a PDA or even just seen an advert related to it, we have all come across a wireless data or voice network!
If a user, application or company wishes to make data portable, mobile and accessible then wireless networking is the answer. A wireless networking system would rid of the downtime you would normally have in a wired network due to cable problems. It would also save time and money due to the fact that you would spare the expense of installing a lot of cables. Also, if a client computer needs to relocate to another part of the office then all you need to do is move the machine with the wireless network card.
Wireless networking can prove to be very useful in public places – libraries, guest houses, hotels, cafeterias, and schools are all places where one might find wireless access to the Internet. From a financial point of view, this is beneficial to both the provider and the client. The provider would offer the service for a charge – probably on a pay per use system, and the client would be able to take advantage of this service in a convenient location; away from the office or home. A drawback of wireless Internet is that the QoS (Quality of Service) is not guaranteed and if there is any interference with the link then the connection may be dropped.
A wireless network is a flexible data communications system, which uses wireless media such as radio frequency technology to transmit and receive data over the air, minimizing the need for wired connections .Wireless networks are used to augment rather than replace wired networks and are most commonly used to provide last few stages of connectivity between a mobile user and a wired network.
Wireless networks use electromagnetic waves to communicate information from one point to another without relying on any physical connection. Radio waves are often referred to as radio carriers because they simply perform the function of delivering energy to a remote receiver. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at the receiving end. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier. Multiple radio carriers can exist in the same space at the same time without interfering with each other if the radio waves are transmitted on different radio frequencies. To extract data, a radio receiver tunes in one radio frequency while rejecting all other frequencies. The modulated signal thus received is then demodulated and the data is extracted from the signal.
Subscribe to:
Comments (Atom)