March 2011
Intermediate
680 pages
25h 12m
English
Chapter 10
Turbo Equalisation for Partial-Response Systems
The previous chapter introduced the basics of partial-response modulation techniques and channel equalisation using Soft-In/Soft-Out (SISO) algorithms, such as the Maximum A Posteriori (MAP) algorithm and the Log-MAP algorithm. With this background, in this chapter we embark on the study of their turbo equalisation. Hence a good background in turbo decoding and SISO algorithms constitutes the foundations required for the appreciation of this chapter, which were discussed in Chapters 4 and 9.
Turbo equalisation was first proposed by Douillard et al. in 1995 [127] for a serially concatenated convolutional-coded BPSK system, as shown in Figure 10.1. In this contribution turbo equalisation employing the structure illustrated in Figure 10.2 was shown to mitigate the effects of ISI when having perfect channel impulse response information. Instead of performing the equalisation and decoding independently, in order to overcome the channel’s frequency selectivity, better performance can be obtained by the turbo equaliser which considers the discrete channel’s memory and performs both the equalisation and decoding iteratively.
Figure 10.1: Serially concatenated convolutional-coded BPSK system using the turbo equaliser which performs the equalisation, demodulation and channel decoding iteratively.
The basic philosophy of the original ...
