OFDM for Underwater Acoustic Communications

Chapter 8Data Detection

This chapter presents the data detection (a.k.a channel equalization) module of the OFDM receivers to be examined in later chapters. Due to the existence of channel coding in practical systems, the data detection module will compute the soft information as needed by the channel decoder. In a noniterative receiver as shown in Figure 8.1(a), the data detection module computes soft information based on the collected measurements only, and passes it to the channel decoder. In an iterative receiver as shown in Figure 8.1(b), the data detection module is coupled with the channel decoder with information exchange between the two modules, where the soft information from the channel decoder is used as prior information of data symbols in data detection. Such an iterative data detection and channel decoding is refereed to as turbo equalization.

Figure 8.1 Illustration of noniterative and turbo equalization, denotes the extrinsic information from the channel equalizer. represents the extrinsic information from channel decoder, which is used as the a priori information for channel equalization.

In the context of OFDM receiver design for underwater acoustic channels, ...