14-12-2012, 12:33 PM
4TH GENETATION
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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
INTRODUCTION
Consumers demand more from their technology. Whether it be a television, cellular phone, or refrigerator, the latest technology purchase must have new features. With the advent of the Internet, the most-wanted feature is better, faster access to information. Cellular
subscribers pay extra on top of their basic bills for such features as instant messaging, stock
quotes, and even Internet access right on their phones. But that is far from the limit of features; manufacturers entice customers to buy new phones with photo and even video capability. It is no longer a quantum leap to envision a time when access to all necessary information — the power of a personal computer — sits in the palm of one’s hand. To support such a powerful system, we need pervasive, high-speed wireless connectivity. A number of technologies currently exist to provide users with high-speed digital wireless connectivity; Bluetooth and 802.11 are examples. These two standards provide very high speed network connections over short distances, typically in the tens of meters. Mean while, cellular providers seek to increase speed on their long-range wireless networks. The goal is the same: long-range, high-speed wireless, which for the purposes of this report will be called 4G, for fourth-generation wireless system.
HISTORY
The original cellular phone network in the United States was called the Analog Mobile Phone System (AMPS). It was developed by AT&T and launched in 1983. AMPS operated in the 800 MHz range, from 824-849 MHz and 869-894 MHz. The lower band was used for transmissions from the phone to the base station, and the upper band was for the reverse direction (Leon-Garcia and Widjaja 2000). This allows full duplex conversation, which is desirable for voice communications. The bands were divided into 832 sub channels, and each connection required a pair: one each for sending and receiving data. Each sub channel was 30 KHz wide, which yielded voice quality comparable to wired telephones. The sub channels were set up so that every sub channel pair was exactly 45 MHz apart (Leon-Garcia and Widjaja 2000). Several of the channels were reserved exclusively for connection setup and teardown. The base station in a particular cell kept a record of which voice sub channel pairs were in use. Though usable, this system included a number of security flaws. Because each phone transmitted (like any radio transmitter) in the clear on its own frequency, the phones in this system “were almost comically vulnerable to security attacks” (Riezenman 2000, 40). The crime of service theft plagued cellular service providers, as individuals with radio scanners could “sniff” the cellular frequencies and obtain the phone identification numbers necessary to “clone” a phone (Riezenman 2000, 39).
ADVANTAGES
There are many advantages of packets and very few disadvantages. Packets are a proven method to transfer information. Packets are:
More Flexible :-
Current technologies require a direct path from one end of a communication to the other. This limits flexibility of the current network; it is more like a large number of direct communication paths than a network. When something happens to the path in the current system, information is lost, or the connection is terminated (e.g. a dropped call).
More Reliable :-
Packets know general things about the information they contain and can be checked for errors at their destination. Error correction data is encoded in the last part of the packet, so if the transmission garbles even one bit of the information, the receiving device will know and ask for the data to be retransmitted. Packets are also numbered so that if one goes missing, the device on the receiving end will know that something has gone wrong and can request that the packet(s) in question be sent again.
Proven Technology :-
Packets are the underlying technology in essentially all data based communication. Since the beginning of the Internet over 30 years ago, packets have been used for all data transmission. Technologies have evolved to ensure an almost 100% QoS for packet transmission across a network.
4G Software
4G will likely become a unification of different wireless networks, including wireless LAN technologies (e.g. IEEE 802.11), public cellular networks (2.5G, 3G), and even personal area networks. Under this umbrella, 4G needs to support a wide range of mobile devices that can roam across different types of networks (Cefriel ). These devices would have to support different networks, meaning that one device would have to have the capability of working on different networks. One solution to this “multi-network functional device” is a software
4G HARDWARE
Ultra Wide Band Networks :-
Ultra Wideband technology, or UWB, is an advanced transmission technology that can be used in the implementation of a 4G network. The secret to UWB is that it is typically detected as noise. This highly specific kind of noise does not cause interference with current radio frequency devices, but can be decoded by another device that recognizes UWB and can reassemble it back into a signal. Since the signal is disguised as noise, it can use any part of the frequency spectrum, which means that it can use frequencies that are currently in use by other radio frequency devices (Cravotta ). An Ultra Wideband device works by emitting a series of short, low powered electrical pulses that are not directed at one particular frequency but rather are spread across the entire spectrum (Butcher ). As seen in Figure 6, Ultra Wideband uses a frequency of between 3.1 to 10.6 GHz.