10-03-2011, 12:21 PM
wirelessccc
10-03-2011, 12:21 PM
wirelessccc
12-03-2011, 04:20 PM
4G. 2003doc.doc (Size: 280 KB / Downloads: 98) ABSTRACT:- The approaching 4G (fourth generation) mobile communication systems are projected to solve still-remaining problems of 3G (third generation) systems and to provide a wide variety of new services, from high-quality voice to high-definition video to high-data-rate wireless channels. The term 4G is used broadly to include several types of broadband wireless access communication systems, not only cellular telephone systems. One of the terms used to describe 4G is MAGIC—Mobile multimedia, anytime anywhere, Global mobility support, integrated wireless solution, and customized personal service. As a promise for the future, 4G systems, that is, cellular broadband wireless access systems have been attracting much interest in the mobile communication arena. The 4G systems not only will support the next generation of mobile service, but also will support the fixed wireless networks. This paper presents an overall vision of the 4G features, framework, and integration of mobile communication. The features of 4G systems might be summarized with one word—integration. The 4G systems are about seamlessly integrating terminals, networks, and applications to satisfy increasing user demands. The continuous expansion of mobile communication and wireless networks shows evidence of exceptional growth in the areas of mobile subscriber, wireless network access, mobile services, and applications. DEFINITION:-4G is the short term for fourth-generation wireless, the stage of broadband mobile communications that will supercede the third generation (3G). it is expected that end-to-end IP and high-quality streaming video will be among 4G's distinguishing features. Fourth generation networks are likely to use a combination of WiMAX and WiFi. 4G technologies are sometimes referred to by the acronym "MAGIC," which stands for Mobile multimedia, Anytime/any-where, Global mobility support, Integrated wireless and Customized personal service. Although 3G networks were really about the technology, 4G networks are both a technology and a business transformation. 4G will potentially reshape not just the wireless industry, but also cable, wireline and handset companies. It will also simultaneously provide the media and entertainment industries another avenue for content delivery. 4G HISTORY:- At the end of the 1940’s, the first radio telephone service was introduced, and was designed to users in cars to the public land-line based telephone network. Then, in the 60s, a system launched by Bell Systems, called IMTS, or, “Improved Mobile Telephone Service", brought quite a few improvements such as direct dialling and more bandwidth. The very first analog systems were based upon IMTS and were created in the late 60s and early 70s. The systems were called "cellular" because large coverage areas were split into smaller areas or "cells", each cell is served by a low power transmitter and receiver. The 1G, or First Generation. 1G was an analog system, and was developed in the 70s, 1G had two major improvements, this was the invention of the microprocessor, and the digital transform of the control link between the phone and the cell site. 1G analog system for mobile communications saw two key improvements during the 1970s: the invention of the microprocessor and the digitization of the control link between the mobilephone and the cell site. Advance mobile phone system (AMPS) was first launched by the US and is a 1G mobile system. Based on FDMA, it allows users to make voice calls in 1 country 2G, OR SECOND GENERATION: 2G first appeared around the end of the 1980’s, the 2G system digitized the voice signal, as well as the control link. This new digital system gave a lot better quality and much more capacity (i.e. more people could use there phones at the same time), all at a lower cost to the end consumer. Based on TDMA, the first commercial network for use by the public was the Global system for mobile communication (GSM). 3G, or THIRD GENERATION:- 3G systems promise faster communications services, entailing voice, fax and Internet data transfer capabilities, the aim of 3G is to provide these services any time, anywhere throughout the globe, with seamless roaming between standards. ITU’s IMT-2000 is a global standard for 3G and has opened new doors to enabling innovative services and application for instance, multimedia entertainment, and location-based services, as well as a whole lot more. In 2001, Japan saw the first 3G network launched. 3G technology supports around 144 Kbps, with high speed movement, i.e. in a vehicle. 384 Kbps locally, and up to 2Mbps for fixed stations, i.e. in a building. 4G, or FOURTH GENERATION:- For 1 and 2G standards, bandwidth maximum is 9.6 kbit/sec, This is approximately 6 times slower than an ISDN (Integrated services digital network). Rates did increase by a factor of 3 with newer handsets to 28.8kbps. This is rarely the speed though, as in crowded areas, when the network is busy, rates do drop dramatically. Third generation mobile, data rates are 384 kbps (download) maximum, typically around 200kbps, and 64kbps upload. These are comparable to home broadband connections. Fourth generation mobile communications will have higher data transmission rates than 3G. 4G mobile data transmission rates are planned to be up to 100 megabits per second on the move and 1000gigbits per second stationary, this is a phenomenal amount of bandwidth, only comparable to the bandwidth workstations get connected directly to a LAN. Motivation for 4G Research Before 3G Has Not Been Deployed? • 3G performance may not be sufficient to meet needs of future high-performance applications like multi-media, full-motion video, wireless teleconferencing. We need a network technology that extends 3G capacity by an order of magnitude. • There are multiple standards for 3G making it difficult to roam and interoperate across networks. we need global mobility and service portability • 3G is based on primarily a wide-area concept. We need hybrid networks that utilize both wireless LAN (hot spot) concept and cell or base-station wide area network design. • We need wider bandwidth • Researchers have come up with spectrally more efficient modulation schemes that can not be retrofitted into 3G infrastructure • We need all digital packet network that utilizes IP in its fullest form with converged voice and data capability.
13-03-2011, 09:45 PM
15-03-2011, 12:05 PM
Submitted by:
Himanshu Pareek 4G Technology Introduction: 4G stands for the fourth generation of cellular wireless standards. It is a successor to 3G and 2G families of standards. Speed requirements for 4G service set the peak download speed at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users). A 4G system is expected to provide a comprehensive and secure all-IP based mobile broadband solution to smart phones, laptop computer wireless modems and other mobile devices. Facilities such as ultra-broadband Internet access, IP telephony, gaming services, and streamed multimedia may be provided to users. The technologies that fall in the 4G categories are UMTS, OFDM, SDR, TD-SCDMA, MIMO and WiMAX to the some extent. 4G Technology offers high data rates that will generate new trends for the market and prospects for established as well as for new telecommunication businesses. 4G networks, when tied together with mobile phones with in-built higher resolution digital cameras and also High Definition capabilities will facilitate video blogs. Some key features (primarily from users' points of view) of 4G mobile networks are as follows: High usability: anytime, anywhere, and with any technology Support for multimedia services at low transmission cost Personalization Integrated services open Internet platform
26-03-2011, 02:04 PM
Presented by:
Pravin Rasal New Microsoft PowerPoint Presentation.ppt (Size: 308 KB / Downloads: 70) Introduction • 4G usually refers to the successor of the 3G and 2G standards. • 4G is a broader term and could include standards outside IMT-Advanced. • A 4G system may upgrade existing communication networks and is expected to provide a secure IP based solution where facilities such as voice, data and streamed multimedia will be provided to users on an "Anytime, Anywhere" basis and at much higher data rates compared to previous generations. What is 4G ? 4G, fourth-generation, is a technology that will transform wireless communications in a completely new way. It is also known as “beyond 3G," It is also known as “beyond 3G," since it provides a secure IP (Internet Protocol) solution. History of 4G • At the end of the 1940’s, the first radio telephone service was introduced, and was designed to users in cars to the public land-line based telephone network. • Then, in the sixties, a system launched by Bell Systems, called IMTS, or, “Improved Mobile Telephone Service", brought quite a few improvements such as direct dialling and more bandwidth.
27-03-2011, 04:38 PM
hi,
can u tell me how to download full report
28-03-2011, 03:43 PM
Presentated by:
A.HARIHARAN P.THIRUVADISAMY HARI.ppt (Size: 1.43 MB / Downloads: 91) ABSTRACT to the third generation of mobile telephony (that is, cellular) technology. The third generation, as the name suggests, follows two earlier s. Evolution of Mobile Network First generation (1G): Analog voice systems Second Generation (2G): Digital voice systems Second Generation – advanced (2.5G): Combining voice and data communications Third Generation (3G): Digital voice and data communications – Developing a more general mobile network • Handling Internet access, email, messaging, multimedia • Access to any services (voice, video, data, etc.) – Requires high quality transmission Fourth Generation (4G): All-IP mobile networks – Ubiquitous wireless communications – Transparent to any services – Integrating multi-networks • IG 2G • 3G 4G 4G NETWORK ARCHITECTURE - The number of access networks in public, private business and home areas is increasing. - Service providers will need access to specific network characteristics to be able to enhance their services, and may have certain requirements such as minimum delay guarantees. - Another aspect is that the user needs to control the usage of the available networks, especially when this usage comes with a price. • HOW 4G WORKS - 4G is being developed to accommodate the quality of service (QoS). - Objectives: * A spectrally efficient * High network capacity * Data rate: 100 Mbit/s between any two points in the world * Smooth handoff * Seamless connectivity * High quality of service for next generation * Interoperability with existing wireless standards * Packet switched network. 4G SYSTEM - It should dynamically share and utilize network resources to meet the minimal requirements. - Stands for fourth generation of cellular wireless standard. - Successor to 3G and 2G families. - Download speed: high mobility communication:100 Mbit/s low mobility communication:1 Gbit/s - Provide a comprehensive and secure all-IP based mobile broadband solution. FEATURES OF 4G Spontaneous self organization of networks of devices. Not necessarily connected to internet. 4G will create hybrid wireless networks using Ad Hoc networks. Form of mesh networking–Very reliable. • 4G HARDWARE • Ultra Wide Band Networks • Smart Antennas • 4G SOFTWARE • Software Defined Radio • Interactive media Plat-form 4G HARDWARE Ultra Wide Band Networks: - Advanced transmission technology. - Used in implementation of 4G. - It is typically detected as noise. - Noise does not cause interference with current radio frequency devices. - But it can reassemble the noise back into a signal. - Works by emitting a series of short, low powered electrical pulses. - The pulse can be called “shaped noise” because it is not flat, but curves across the spectrum. - Frequency : between 3.1 to 10.6 GHz. - Bandwidth : 60 megabits per second. Smart Antennas: - Multiple “smart antennas” can be employed to help find, tune, and turn up signal information. - The antennas can both “listen” and “talk”. - A smart antenna can send signals backing the same direction that they came from. - Two Types: Switched Beam Antennas Adaptive Array Antennas Uses: • Optimize available power • Increase base station range and coverage • Reuse available spectrum • Increase bandwidth • Lengthen battery life of wireless devices Switched Beam Antennas: - It have fixed beams of transmission. - It can switch from one predefined beam to another when the user with the phone moves throughout the sector. Adaptive Array Antenna: - It is needed to process data on both the sending and receiving side. - This software should be flexible, as the future wireless world will likely be a heterogeneous mix of technologies. - Minimize interference. - Maximize intended signal reception. • Smart Antennas 4G SOFTWARE - 4G needs to support a wide range of mobile devices . - These devices would have to support different networks. - Solution : “software defined radio”. Software Defined Radio: - It can be configured to any radio or frequency standard through the use of software. - Advantages: Flexibility for wireless standards. Dynamically updated with new software Roaming is not an issue. - In order to be able to download software at any location, the data must be formatted to some standard. - This is the job of the packet layer, which will split the data into small “packets.” Interactive media Plat-form: - Software platform for mobilestreaming applications. - Designed as an end-to-end solution, the system consists of , Dedicated content creation machines. Player application runs on widely used operating systems. Content servers hold newly created multimedia content. Proxy builds interface between the player application and other platform. WIMAX Worldwide Inter operability for Microwave Access. "mobile WiMAX", "802.16d" and "802.16e" are frequently used incorrectly. Correct definitions are the following: • 802.16-2004 is often called 802.16d, since that was the working party that developed the standard. It is also frequently referred to as "fixed WiMAX" since it has no support for mobility. • 802.16e-2005 is an amendment to 802.16-2004 and is often referred to in shortened form as 802.16e. It introduced support for mobility, among other things and is therefore also known as "Mobile WiMAX". Living 4G in a 3G World Currently the 4G network is not supporting voice services in its simplest form. The 4G wireless network works on a different frequency than the 3G wireless network. Many of the new 4G wireless network phones available now will be a hybrid of both 4G and 3G networks. The 4G to handle data services and the 3G to handle voice calls. TRAFFIC CONTROL DURING DISASTER APPLICATION Virtual Navigation Tele-Medicine Crisis Management Applications ADVANTAGES • High usability: anytime, anywhere, and with any technology. • Support for multimedia services at low transmission cost. •Higher bandwidth, tight network security. DISADVANTAGES • The equipment required to implement a next generation network is still very expensive. • Carriers and providers have to plan carefully to make sure that expenses are kept realistic. CONCLUSION Low cost high speed data will drive forward the fourth generation (4G) as short- range communication emerges. It is probable that the radio access network will evolve from a centralized architecture to a distributed one. 4G is likely to enable the download of full length songs or music pieces which may change the market response dramatically. Innovations in network technology will provide an environment in which virtually anything is available, anywhere, at any time, via any connected device.
31-03-2011, 10:00 AM
Abstract
Currently 2G Technology (GSM), or second generation technology, is widely used worldwide for cell phone networks. The problem with 2G technology is that the data rates are limited. This makes it inefficient for data transfer applications such as video conferencing, music or video downloads. To increase the speed, various new technologies have been in development. One of these, 4G technology, is mainly made up of high-speed wireless networks designed to carry data, rather than voice or a mixture of the two. 4G transfers data to and from mobile devices at broadband speeds – up to100 Mbps moving and 1Gbps while the phone is stationary. In addition to high speeds, the technology is more robust against interference and tapping guaranteeing higher security. This innovative technology functions with the aid of VoIP, IPv6, and Orthogonal frequency division multiplexing (OFDM). To cater the growing needs of 4G, mobile data communication providers will deploy multiple antennas at transmitters to increase the data rate. Unlike the 3G networks, which are a mix of circuit switched and packet switched networks, 4G will be based on packet switching only (TCP/IP). This will allow low-latency data transmission. Furthermore, the use of IP to transfer information will require IPv6 to facilitate the use of more cell phone devices. During the presentation, an overview of the various generations of mobile device technologies preceding 4G would be followed by technical aspects of 4G and how it functions, as well as the way it can lead to future innovations in cellular and communication technology.
31-03-2011, 03:42 PM
shweta2.pptx (Size: 120.95 KB / Downloads: 62) Welcome to the 4G The term 4G is used broadly to include several types of broadband wirelessaccess communication systems, not only cellular telephone systems.One of the term used to describe 4G is MAGIC-Mobile multimedia Anytime anywhere Global mobility support Integrated wireless solution & Customized personal service The 4th generation of mobile networks will truly turn the current mobilephone networks, in to end to end IP based networks. If 4G is implementedcorrectly, it will truly harmonize global warming. Before 1G 0G refers to pre-cellular mobile telephony technology…. The system were called “cellular” because large coverage areas were split intosmaller areas or “cells", each cell is served by a low power transmitter &receiver. At the end of the 1940’s the first radio telephone service was introduced,&was designed to users in cars to the public land-line based telephoneNetworks In the sixties, a system launched by Bell systems called IMTS, or “ImprovedMobile Telephone Service", brought quite a few improvements such as directdialing & more bandwidth 1G or First generation The 1G,or First generation. It was an analogous system & was developed in theseventies.1G had two major improvements, this was the invention of the microprocessor.& the digital transform of the control link between the phone and the cell site.”AMPS” was first launched by USA & is 1G system. It was based on FDMA used to make voice calls in one country. 2G, or Second generation 2G phones using global system for mobile communication(GSM)were first used in the early 1990s in Europe.GSM provide voice and limited data services, and uses digital modulation for improved audio quality. Digital AMPS,SDMA were some of the 2G systems. 3G,or Third Generation The 3G technology adds multimedia facilities to 2G phone by allowing audio, video & graphics application. The idea behind the 3G is to have single network standard instead of the different types used in US, Europe & Asia. Telecommunication systems(UMTS)or IMT 2000,will sustain higher data rates & open to door to many Internet style application. DRAWBACKS BY GENERATION 1G Poor voice quality Poor battery life Large phone size No security Frequent call drops Limited capacity & poor handoff reliability 2G The GSM is circuit switched, connection oriented technology, were end system are dedicated for the entire call session This causes inefficiency in usage of bandwidth & resources. The GSM-enabled system do not support high data rates. They are unable to handle complex data such as video. 3G High bandwidth requirement High spectrum licensing fees Huge capital Comparison of 3G with 4G 4G or Fourth generation Some possible standards of the 4G system are 802.20, WiMax(802.16) HSPDA, UMTS,TDD UMTS & future version of UMTS & proprietary network form ArryComm Inc., NaviniNetworks, Flarion Technologies, and 4G effort in India, China & Japan The design is that 4G will be based on OFDM, which is the key enabler of the 4G technology. Other technological aspects of the 4g technology are adaptive processing & smart antennas, both of which will be used in 3G networks & enhance rates when used with OFDM FEATURES Faster & more reliable 100 Mb/s(802.11g wireless=54 Mb/s,3G=2 Mb/s) Lower cost than previous generation. Multi-standard wireless system Bluetooth, wired, wireless(802.11x) Ad Hoc networking IPv6 core OFDM used instead of CDMA Different access technology FDMA:-It is a method were the spectrum is cut up in to different frequencies & then this chunk given to the users. At one time only one user is assigned to a frequency because of this the frequency is closed, until the call is ended, or it is passed on to another frequency. TDMA:-It makes use of the whole available spectrum, unlike FDMA. Instead of splitting the slot of frequency. It split them by time, over all of the frequency. Each subscriber is given a time slot as opposed to a frequency therefore many uses can sit on one frequency & have different time slots, because the time slots are switched so rapidly TDMA is used for 2G networks. CDMA:-Uses the spread spectrum method, the way it works means its highly encrypted, so its was no surprise it was developed & used by the military. Unlike FDMA,CDMA allows the user to sit on all the available frequencies at the same time, & hop between then. Each call is identified by its unique code, hence the term code division. HOW OFDM WORKS Orthogonal FDM’s spread spectrum technique spreads the data over a lot of carriers that are spread apart at precise frequencies. This spacing provides the “orthogonality” in this method which prevent the receivers/demodulators from seeing frequencies other than their own specific one. MIMO It uses signal multiplexing between multiple transmitting antennas(space multiplex) and time or frequency. It is well suited to OFDM, as it is possible to process independent time symbol as soon as the OFDM waveform is correctly designed for the channel. This aspect of OFDM greatly simplifies processing. The signal transmitted by m antennas is received by n antennas. In principle, MIMO is more efficient when many multiple signals are received. 4G technologies Smart Antennas Beam radio signals directly at a user to follow the user as they move Allow the same radio frequency to be used for other users without worry of interference Can’t keep up transmission speeds whiole device is moving fast(i.e. in car) only 32Mbps at 62Mph(vs100Mb/s) Smart antenna technology Seamless handoff between towers/access points One transmit antenna, two receive antennas Allow connection to two access points at once IPv6 support IPv6 support is essential in order to support a large, number of wireless-enabled devices. By increasing the number of IP addresses, IPv6 removes the need for Network Address Translation(NAT), a method of sharing a limited number of addresses among a larger group of devices, although NAT will still be required to communicate with devices that are on existing IPv4 networks. As of June 2009,version has posted specifications that require any 4g devices on its network to support IPv6 APPLICATION VIRTUAL PRESENCE 4G system gives mobile users a “virtual presence” (for ex, always on connection to keep people on event)video conferencing VIRTUAL NAVIGATION a remote database contains the graphical representation of streets, buildings, and physical characteristics of a large metropolis. Blocks of this database are transmitted on rapid sequences to a vehicle. TELE-GEOPROCESSING queries dependent on location information of several users in addition to temporal aspects have many application e.g. GIS,GPS The news about 4G First step towards the full range of Wimax/4G Applications. This successful implementation of the OFDM waveform is the first step in military technologies plan to implement the complete IEEE.802.16 family of wireless data application The new Wi-Fi gels with 4G More robust standard for high-speed broadband wireless delivery to laptops and desktops will augment the burgeoning Wi-Fi market beginning in late 2004
06-04-2011, 04:35 PM
Submitted By N.UDAY KUMAR NAIDU K. V. RAMANA REDDY 4TH GENERATION COMMUNICATIONS.doc (Size: 726.5 KB / Downloads: 63) 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.
08-04-2011, 06:53 AM
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08-04-2011, 07:44 AM
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08-04-2011, 12:16 PM
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13-04-2011, 04:54 PM
i want a full seminar on 4G wireless systems.
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