Written by leading authority Ramjee Prasad, this timely new work offers a complete understanding of OFDM technology and applications in wireless communications systems, placing emphasis on wireless LANs and PANs. OFDM is a key technology for beyond 3G communications, promising robust, high capacity, high speed wireless broadband multimedia networks. In this practical resource, established and new technologies are explained clearly and comprehensively, from OFDM basics to a detailed account of a new technique, hybrid OFDM CDMA slow frequency hopping. The book offers an in-depth treatment of the underlying technologies and applications of PANs and describes and evaluates a practical OFDM system concept. Invaluable for wireless engineers and researchers, this cutting edge new book is a must-have for anyone who needs to understand this critical technology and its implementation in WLANs and WPANs.

OFDM for Wireless Communications Systems

From the Publisher:
Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels at different frequencies.
CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimising the use of available bandwidth. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end.
Multi-Carrier (MC) CDMA is a combined technique of Direct Sequence (DS) CDMA (Code Division Multiple Access) and OFDM techniques. It applies spreading sequences in the frequency domain.
Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality.
This technical in-depth book is unique in its detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context.
Divided into three main parts:
Part I provides a detailed exposure of OFDM designed for employment in various applications
Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA
Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink
Portrays theentire body of knowledge currently available on OFDMProvides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMAConsiders the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examplesConverts the lessons of Shannon's information theory into design principles applicable to practical wireless systemsCombines the benefits of a textbook with a research monograph where the depth of discussions progressively increase throughout the book

This all-encompassing self-contained treatment will appeal to researchers, postgraduate students and academics, practising research and development engineers working for wireless communications and computer networking companies and senior undergraduate students and technical managers.

OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting

N-shift cross-orthogonal sequences and a complete complementary code derived from them are defined and discussed. A general method for generating this code is also discussed. A synchronous multiple-user spread-spectrum multiple system is proposed that uses N-shift cross-orthogonal sequences. >

N-shift cross-orthogonal sequences

Radar waveform diversity has received considerable attention in recent years due to increasing spectral congestion and the burgeoning capabilities of digital waveform generation. The promise of waveform diversity is far greater utilization of available degrees of freedom to enhance sensing performance and to even facilitate new operating modes. This tutorial provides an overview of this very broad topic, from the basic principles upon which it is founded to the myriad different areas being explored in research for practical sensing applications.

Overview of radar waveform diversity

Orthogonal frequency division multiplexing (OFDM) is a promising way to provide large data rates at reasonable complexity in wireless fading channels. However, a major disadvantage of OFDM is its large peak-to-average power ratio, which significantly decreases the efficiency of the transmitter power amplifier and hence forms a major obstacle to implementing OFDM in portable communication systems. This paper shows the possibility of using complementary codes for both decreasing the peak-to-average power (PAP) ratio and error correction. Set sizes and minimum distance properties of these codes are derived. It is shown that specific subsets of complementary codes have a minimum distance of up to half the code length, while their PAP ratio is only 3 dB. Simulation results demonstrate the viability of using these codes in multipath fading channels. It is currently planned to implement OFDM with complementary codes in the Wireless ATM Network Demonstrator (WAND), a joint European ACTS program.

OFDM codes for peak-to-average power reduction and error correction

Previous work on polyphase complementary codes is reviewed, and a number of new results are presented including additional kernels and lengths. Generating methods from other binary and polyphase sequences are given and negative results of other existence searches reported. Advantages of specialized forms for radar and Loran-C are discussed, including complementary Barker codes. A table of known lengths of pairs, triads and quads of sequences is given.

R. Frank

Papers

Polyphase complementary codes