March 2011
Intermediate
680 pages
25h 12m
English
Chapter 18
MLC/BICM Schemes for the Wireless Internet1
18.1 Introduction
In wireless communications, the achievable transmission quality and the time delay imposed are crucial in providing a Quality of Service (QoS) suitable for multimedia application. In line with the increasing tele-traffic there is an increasing demand for higher instantaneous transmission rates. Coded modulation constitutes an attractive transmission technique, since it is a bandwidth efficient scheme which incorporates both channel coding and modulation without any bandwidth expansion. Multilevel Coding (MLC) facilitates a flexible coding rate adjustment, while providing Unequal Error Protection (UEP) for diverse applications.
The Multistage Decoding (MSD) scheme of Figure 15.10 was advocated for decoding MLCs, since its performance approaches that of maximum-likelihood decoding, while having the benefit of reduced decoding complexity. However, due to its high time delay and owing to the potential error propagation across the multiple decoding stages, it is not readily suitable for delay-sensitive interactive audio/video applications. Alternatively, the Parallel Independent Decoding (PID) technique of Figure 15.8 [364] may also be employed, where there is no information exchange amongst the protection classes.
MLC schemes may be constructed using different component codes, for example convolutional codes, Bose-Chaudhuri-Hocquenghem (BCH) codes or turbo codes [384]. Classic Low-Density Parity Check (LDPC) ...
