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S.Ram kumar
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4G MAGIC COMMUNICATION
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.
Service Evolution
The evolution from 3G to 4G will be driven by services that offer better quality (e.g. video and sound) thanks to greater bandwidth, more sophistication in the association of a large quantity of information, and improved personalization. Convergence with other network (enterprise, fixed) services will come about through the high session data rate. Machine-to-machine transmission will involve two basic equipment types: sensors (which measure arameters) and tags (which are generally read/write equipment). It is expected that users will require high data rates, similar to those on fixed networks, for data and streaming applications. Mobile terminal usage (laptops, Personal digital assistants, handhelds) is expected to Grow rapidly as they become more users friendly. Fluid high quality video and network creactivity are important user requirements. Key infrastructure design requirements include: fast response, high session rate, high capacity, low user charges, rapid return on investment for operators, investment that is in line with the growth in demand, and simple autonomous terminals.
Dimensioning targets
A simple calculation illustrates the order of magnitude. The design target in terms of radio performance is to achieve a scalable capacity from 50 to 500 bit/s/Hz/km2 (including capacity for indoor use), as shown in Figure 2.Gebit/s/km2)0000
As a comparison, the expected best performance of 3G is around 10 bit/s/Hz/km2 using High Speed Downlink Packet Access (HSDPA), Multiple-Input Multiple-Output (MIMO), etc. No current technology is capable of such performance.
Multi-technology Approach
Many technologies are competing on the road to 4G, as can be seen in Figure 3. Three paths are possible, even if they are more or less specialized. The first is the 3G-centric path, in which Code Division Multiple Access (CDMA) will be progressively pushed to the point at which terminal manufacturers will give up. When this point is reached, another technology will be needed to realize the required increases in capacity and data by Voice over Wireless LAN (VoWLAN). However, it is not clear what the next successful technology will be. Reaching a consensus on a 200 Mbit/s (and more) technology will be a lengthy task, with too many proprietary solutions on offer third path is IEEE 802.16e and 802.20, which are simpler than 3G for the equivalent performance. A core network evolution towards a broadband Next Generation Network (NGN) will facilitate the introduction of new access network technologies through standard access gateways, based on ETSI-TISPAN, ITU-T, 3GPP, China Communication Standards Association (CCSA) and other standards. How can an operator provide a large number of users with high session data rates using its existing infrastructure? At least two technologies are needed. The first (called “parent coverage”) is dedicated to large coverage and real-time services. Legacy technologies, such as 2G/3G and their evolutions will be complemented by Wi-Fi and WiMAX. A second set of technologies is needed to increase capacity, and can be designed without any constraints on coverage continuity. This is known as Pico-cell coverage. Only the use of both technologies can achieve both targets (Figure 4). Handover between parent coverage and Pico cell coverage is different from a classical roaming process, but similar to classical handover. Parent coverage can also be used as a back-up when service delivery in the Pico cell becomes too difficult.
Key 4G Technologies
Some of the key technologies required for 4G are briefly described below:
OFDMA
Orthogonal Frequency Division Multiplexing (OFDM) not only provides clear advantages for physical layer performance, but also a framework for improving layer 2 performance by proposing an additional degree of free-dom. Using ODFM, it is possible to exploit the time domain, the space domain, the frequency domain and even the code domain to optimize radio channel usage. It ensures very robust transmission in multi-path environments with reduced receiver complexity. As shown in Figure 5, the signal is split into orthogonal subcarriers, on each of which the signal is “narrowband” (a few kHz) and therefore immune to multi-path effects, provided a guard interval is inserted between