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.
Wednesday, March 31, 2010
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.
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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.
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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.
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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.
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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.
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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
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