New Modulation And Digital Synchronization Techniques For Higher Capacity Mobile And Personal Communication Systems

In Time Division Multiple Access (TDMA), within a given time frame a particular user is allowed to transmit within a given time slot. This technique is used in most of the second-generation digital mobile communication systems. In Europe the system is known as GSM, in USA as DAMPS and in Japan as MPT. In Code Division Multiple Access (CDMA) every user is using a distinct code so that it can occupy the same frequency bandwidth at the same time with other users and still can be separated on the basis of low correlation between the codes. These systems like IS-95 in the USA are also developed and standardized within the second generation of the mobile communication systems. CDMA systems within a cellular network can provide higher capacity and for this reason they become more and more attractive. At this moment it seems that both TDMA and CDMA remain viable candidates for application in future systems. Wireless Communications: TDMA versus CDMA provides enough information for correct understanding of the arguments in favour of one or other multiple access technique. The final decision about which of the two techniques should be employed will depend not only on technical arguments but also on the amount of new investments needed and compatibility with previous systems and their infrastructures. Wireless Communications: TDMA versus CDMA comprises a collection of specially written contributions from the most prominent specialists in wireless communications in the world today and presents the major, up to date, issues in this field. The material is grouped into four chapters: Communication theory, covering coding and modulation, Wireless communications, Antenna & Propagation and Advanced Systems & Technology. The book describes clearly the issues and presents the information in such a way that informed decisions about third generation wireless systems can be taken. It is essential reading for all researchers, engineers and managers working in the field of Wireless Communications.

Synchronization is a critical function in digital communications; its failures may have catastrophic effects on the transmission system performance. Furthermore, synchronization circuits comprehend such a large part of the receiver hardware that their implementation has a substantial impact on the overall costs. For these reasons design engineers are particularly concerned with the development of new and more efficient synchronization structures. Unfortunately, the advent of digital VLSI technology has radically affected modem design rules, to a point that most analog techniques employed so far have become totally obsolete. Although digital synchronization methods are well established by now in the literature, they only appear in the form of technical papers, often concentrating on specific performance or implementation issues. As a consequence they are hardly useful to give a unified view of an otherwise seemingly heterogeneous field. It is widely recognized that a fundamental understanding of digital synchronization can only be reached by providing the designer with a solid theoretical framework, or else he will not know where to adjust his methods when he attempts to apply them to new situations. The task of the present book is just to develop such a framework.

FDMA, TDMA and CDMA are the well known multiplexing techniques used in wireless communication systems. While working with the wireless systems using these techniques various problems encountered are (1) multi-path fading (2) time dispersion which lead to intersymbol interference (ISI) (3) lower bit rate capacity (4) requirement of larger transmit power for high bit rate and (5) less spectral efficiency. In a typical terrestrial broadcasting, the transmitted signal arrives at the receiver using various paths of different lengths. Since multiple versions of the signal interfere with each other, it becomes difficult to extract the original information. The use of orthogonal frequency division multiplexing (OFDM) technique provides better solution for the above mentioned problems. OFDM technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the "orthogonality", which prevents the demodulator from seeing frequencies other than their own. The benefits of OFDM are high spectral efficiency, resiliency of RF interference, and lower multi-path distortion. OFDM is a powerful modulation technique that is capable of high data rate and is able to eliminate ISI. The use of FFT technique to implement modulation and demodulation functions makes it computationally more efficient. The OFDM based wireless communication system design includes the design of OFDM transmitter, and OFDM receiver. Using MATLAB, simulation of OFDM was done with different modulation techniques using different transform techniques. The digital modulation schemes such as BPSK and QPSK were From the simulation results, it is observed that the BPSK allows the BER to be improved in a noisy channel at the cost of maximum data transmission capacity. Use of QPSK allows higher transmission capacity, but at the cost of slight increase in the probability of error. From the results, use of OFDM with QPSK is beneficial for short distance transmissio.

Frequency spectrum is a limited and valuable resource for wireless communications. A good example can be observed among network operators in Europe for the prices to pay for UMTS-frequency bands. Therefore, the first goal when designing future wireless communication systems (e.g. 4G - fourth generation) has to be the increase in spectral efficiency. The development in digital communications in the past years has enabled efficient modulation and coding techniques for robust and spectral efficient data, speech, audio and video transmission. These are the multi-carrier modulation (e.g. OFDM) and the spread spectrum technique (e.g. DS-CDMA), where OFDM was chosen for broadcast applications (DVB, DAB) as well as for broadband wireless indoor standards (ETSI HIPERLAN-II, IEEE-802.11) and the DS-CDMA was selected in mobile communications (IS-95, third generation mobile radio systems world wide, UMTS/IMT 2000). Since 1993 various combinations of multi-carrier (MC) modulation and the spread spectrum (SS) technique have been introduced and the field of MC-SS communications has become an independent and important research topic with increasing activities. New application fields have been proposed such as high rate cellular mobile, high rate wireless indoor and LMDS. It has been shown that MC-SS offers the high spectral efficiency, robustness and flexibility that is required for the next generation systems. Meanwhile, different alternative hybrid schemes such as OFDM/OFDMA, MC-TDMA, etc. have been deeply analysed and adopted in different international standards (ETSI-BRAN, IEEE-802 & MMAC). Multi-Carrier & Spread-Spectrum: Analysis of Hybrid Air Interfaces draws together all of the above mentioned hybrid schemes therefore providing a greatly needed resource for system engineers, telecommunication designers and researchers in order to enable them to develop, build and deploy several schemes based on MC-transmission for the next generation systems (which will be an integration of broadband multimedia services covering both 4G mobile and fixed wireless systems). * Offers a complete treatment of multi-carrier, spread-spectrum (SS) and time division multiplexing (TDM) techniques * Provides an in-depth insight into hybrid multiple access techniques based on multi-carrier (MC) transmission * Presents numerous hybrid multiple access and air interface architectures including OFDM/CDMA, MC-CDMA, MC-DS-CDMA and MT-CDMA * Covers new techniques such as space-time coding and software radio Telecommunications engineers, hardware & software system designers and researchers as well as students, lecturers and technicians will all find this an invaluable addition to their bookshelf.

The Best of the Best: Fifty Years of Communications and Networking Research consists of a group of 50 papers selected as the best published by ComSoc in its various journals in the Society’s 50-year history. The editors of the collection have written an essay to introduce the papers and discuss the historical significance of the collection and how they were selected for the collection. The book divides the papers into two major categories (Communications and Networking) and groups them by decade within these major subdivisions.

This practical guide helps readers to learn how to develop and implement synchronization functions in digital communication systems.

This handbook covers the field of mobile communications, from principles of analog and digital communications to cordless telephones, wireless local area networks (LANs) and international technology standards. The scope of the handbook should ensure that it will be a primary reference.