06-04-2011, 04:35 PM
Submitted By
N.UDAY KUMAR NAIDU
K. V. RAMANA REDDY
[attachment=11812]
ABSTRACT
First generation (1G) wireless telecommunications – the brick-like analog phones that are now collector’s items - introduced the cellular architecture that is still being offered by most wireless companies today. Second generation (2G) wireless supported more users within a cell by using digital technology, which allowed many callers to use the same multiplexed channel. But 2G was still primarily meant for voice communications, not data, except some very low data-rate features, like short messaging service (SMS). So-called 2.5G allowed carriers to increase data rates with a software upgrade at the base transceivers stations (BTS), as long as consumers purchased new phones too. Third generation (3G) wireless offers the promise of greater bandwidth, basically bigger data pipes to users, which will allow them to send and receive more information.
Fourth generation (4G) wireless was originally conceived by the Defense Advanced Research Projects Agency (DARPA). Although experts and policymakers have yet to agree on all the aspects of 4G wireless, two characteristics have emerged as all but certain components of 4G: end-to-end Internet Protocol (IP), and peer-to-peer networking. An all IP network makes sense because consumers will want to use the same data applications they are used to in wired networks. The final definition of “4G” will have to include something as simple as this: if a consumer can do it at home or in the office while wired to the Internet, that consumer must be able to do it wirelessly in a fully mobile environment.
INTRODUCTION
Let’s define “4G” as “wireless ad hoc peer-to-peer networking.” 4G technology is significant because users joining the network add mobile routers to the network infrastructure. Because users carry much of the network with them, network capacity and coverage is dynamically shifted to accommodate changing user patterns. As people congregate and create pockets of high demand, they also create additional routes for each other, thus enabling additional access to network capacity. Users will automatically hop away from congested routes to less congested routes. This permits the network to dynamically and automatically self-balance capacity, and increase network utilization. What may not be obvious is that when user devices act as routers, these devices are actually part of the network infrastructure. So instead of carriers subsidizing the cost of user devices (e.g., handsets, PDAs, of laptop computers), consumers actually subsidize and help deploy the network for the carrier.
With a cellular infrastructure, users contribute nothing to the network. They are just consumers competing for resources. But in wireless ad hoc peer-to-peer networks, users cooperate – rather than compete – for network resources. Thus, as the service gains popularity and the number of users increases, service likewise improves for all users.
There is also the 80/20 rule. With traditional wireless networks, about 80% of the cost is for site acquisition and installation, and just 20% is for the technology. Rising land and labor costs means installation costs tend to rise over time, subjecting the service providers’ business models to some challenging issues in the out years. With wireless peer-to-peer networking, however, about 80% of the cost is the technology and only 20% is the installation. Because technology costs tend to decline over time, a current viable business model should only become more profitable over time. The devices will get cheaper, and service providers will reach economies of scale sooner because they will be able to pass on the infrastructure savings to consumers, which will further increase the rate of penetration.
CURRENT TECHNOLOGY
Most modern cellular phones are based on one of two transmission technologies: time-division multiple access (TDMA) or code-division multiple access (CDMA) . These two technologies are collectively referred to as second-generation, or 2G. Both systems make eavesdropping more difficult by digitally encoding the voice data and compressing it, then splitting up the resulting data into chunks upon transmission
TDMA
TDMA, or Time Division Multiple Access, is a technique for dividing the time domain up into sub-channels for use by multiple devices. Each device gets a single time slot in a procession of devices on the network. During that particular time slot, one device
is allowed to utilize the entire bandwidth of the spectrum, and every other device is in the quiescent state.
The time is divided into frames in which each device on the network gets one timeslot. There are n timeslots in each frame, one each for n devices on the network. In practice, every device gets a timeslot in every frame. This makes the frame setup simpler and more
efficient because there is no time wasted on setting up the order of transmission. This has
the negative side effect of wasting bandwidth and capacity on devices that have nothing to send.
One optimization that makes TDMA much more efficient is the addition of a registration period at the beginning of the frame. During this period, each device indicates how much data it has to send. Through this registration period, devices with nothing to send waste no time by having a timeslot allocated to them, and devices with lots of pending data can have extra time with which to send it. This is called ETDMA (Extended TDMA) and can
increase the efficiency of TDMA to ten times the capacity of the original analog cellular phone network.
The benefit of using TDMA with this optimization for network access comes when data is “bursty.” That means, at an arbitrary time, it is not possible to predict the rate or amount of pending data from a particular host. This type of data is seen often in voice transmission, where the rate of speech, the volume of speech, and the amount of background noise are constantly varying. Thus, for this type of data, very little capacity is wasted by excessive allocation.
CDMA
CDMA, or Code Division Multiple Access, allows every device in a cell to transmit over the entire bandwidth at all times. Each mobile device has a unique and orthogonal code that is used to encode and recover the signal. The mobile phone digitizes the voice data as it is received, and encodes the data with the unique code for that phone. This is accomplished by taking each bit of the signal and multiplying it by all bits in the unique code for the phone. Thus, one data bit is transformed into a sequence of bits of the same length as the code for the mobile phone. This makes it possible to combine with other signals on the same frequency range and still recover the original signal from an arbitrary mobile phone as long as the code for that phone is known. Once encoded, the data is modulated for transmission over the bandwidth allocated for that transmission. A block diagram of the process is shown
By keeping security in mind while designing the new system, the creators of 2G wireless were able to produce a usable system that is still in use today. Unfortunately, 2G technology is beginning to feel its age. Consumers now demand more features, which in turn require higher data rates than 2G can handle. A new system is needed that merges voice and data into the same digital stream, conserving bandwidth to enable fast data access. By using advanced hardware and software at both ends of the transmission, 4G is the answer to this problem.
N.UDAY KUMAR NAIDU
K. V. RAMANA REDDY
[attachment=11812]
ABSTRACT
First generation (1G) wireless telecommunications – the brick-like analog phones that are now collector’s items - introduced the cellular architecture that is still being offered by most wireless companies today. Second generation (2G) wireless supported more users within a cell by using digital technology, which allowed many callers to use the same multiplexed channel. But 2G was still primarily meant for voice communications, not data, except some very low data-rate features, like short messaging service (SMS). So-called 2.5G allowed carriers to increase data rates with a software upgrade at the base transceivers stations (BTS), as long as consumers purchased new phones too. Third generation (3G) wireless offers the promise of greater bandwidth, basically bigger data pipes to users, which will allow them to send and receive more information.
Fourth generation (4G) wireless was originally conceived by the Defense Advanced Research Projects Agency (DARPA). Although experts and policymakers have yet to agree on all the aspects of 4G wireless, two characteristics have emerged as all but certain components of 4G: end-to-end Internet Protocol (IP), and peer-to-peer networking. An all IP network makes sense because consumers will want to use the same data applications they are used to in wired networks. The final definition of “4G” will have to include something as simple as this: if a consumer can do it at home or in the office while wired to the Internet, that consumer must be able to do it wirelessly in a fully mobile environment.
INTRODUCTION
Let’s define “4G” as “wireless ad hoc peer-to-peer networking.” 4G technology is significant because users joining the network add mobile routers to the network infrastructure. Because users carry much of the network with them, network capacity and coverage is dynamically shifted to accommodate changing user patterns. As people congregate and create pockets of high demand, they also create additional routes for each other, thus enabling additional access to network capacity. Users will automatically hop away from congested routes to less congested routes. This permits the network to dynamically and automatically self-balance capacity, and increase network utilization. What may not be obvious is that when user devices act as routers, these devices are actually part of the network infrastructure. So instead of carriers subsidizing the cost of user devices (e.g., handsets, PDAs, of laptop computers), consumers actually subsidize and help deploy the network for the carrier.
With a cellular infrastructure, users contribute nothing to the network. They are just consumers competing for resources. But in wireless ad hoc peer-to-peer networks, users cooperate – rather than compete – for network resources. Thus, as the service gains popularity and the number of users increases, service likewise improves for all users.
There is also the 80/20 rule. With traditional wireless networks, about 80% of the cost is for site acquisition and installation, and just 20% is for the technology. Rising land and labor costs means installation costs tend to rise over time, subjecting the service providers’ business models to some challenging issues in the out years. With wireless peer-to-peer networking, however, about 80% of the cost is the technology and only 20% is the installation. Because technology costs tend to decline over time, a current viable business model should only become more profitable over time. The devices will get cheaper, and service providers will reach economies of scale sooner because they will be able to pass on the infrastructure savings to consumers, which will further increase the rate of penetration.
CURRENT TECHNOLOGY
Most modern cellular phones are based on one of two transmission technologies: time-division multiple access (TDMA) or code-division multiple access (CDMA) . These two technologies are collectively referred to as second-generation, or 2G. Both systems make eavesdropping more difficult by digitally encoding the voice data and compressing it, then splitting up the resulting data into chunks upon transmission
TDMA
TDMA, or Time Division Multiple Access, is a technique for dividing the time domain up into sub-channels for use by multiple devices. Each device gets a single time slot in a procession of devices on the network. During that particular time slot, one device
is allowed to utilize the entire bandwidth of the spectrum, and every other device is in the quiescent state.
The time is divided into frames in which each device on the network gets one timeslot. There are n timeslots in each frame, one each for n devices on the network. In practice, every device gets a timeslot in every frame. This makes the frame setup simpler and more
efficient because there is no time wasted on setting up the order of transmission. This has
the negative side effect of wasting bandwidth and capacity on devices that have nothing to send.
One optimization that makes TDMA much more efficient is the addition of a registration period at the beginning of the frame. During this period, each device indicates how much data it has to send. Through this registration period, devices with nothing to send waste no time by having a timeslot allocated to them, and devices with lots of pending data can have extra time with which to send it. This is called ETDMA (Extended TDMA) and can
increase the efficiency of TDMA to ten times the capacity of the original analog cellular phone network.
The benefit of using TDMA with this optimization for network access comes when data is “bursty.” That means, at an arbitrary time, it is not possible to predict the rate or amount of pending data from a particular host. This type of data is seen often in voice transmission, where the rate of speech, the volume of speech, and the amount of background noise are constantly varying. Thus, for this type of data, very little capacity is wasted by excessive allocation.
CDMA
CDMA, or Code Division Multiple Access, allows every device in a cell to transmit over the entire bandwidth at all times. Each mobile device has a unique and orthogonal code that is used to encode and recover the signal. The mobile phone digitizes the voice data as it is received, and encodes the data with the unique code for that phone. This is accomplished by taking each bit of the signal and multiplying it by all bits in the unique code for the phone. Thus, one data bit is transformed into a sequence of bits of the same length as the code for the mobile phone. This makes it possible to combine with other signals on the same frequency range and still recover the original signal from an arbitrary mobile phone as long as the code for that phone is known. Once encoded, the data is modulated for transmission over the bandwidth allocated for that transmission. A block diagram of the process is shown
By keeping security in mind while designing the new system, the creators of 2G wireless were able to produce a usable system that is still in use today. Unfortunately, 2G technology is beginning to feel its age. Consumers now demand more features, which in turn require higher data rates than 2G can handle. A new system is needed that merges voice and data into the same digital stream, conserving bandwidth to enable fast data access. By using advanced hardware and software at both ends of the transmission, 4G is the answer to this problem.
