OFDM for Underwater Acoustic Communications

Chapter 14Distributed MIMO OFDM

Chapter 13 was concentrated on co-located MIMO OFDM where data streams arriving at the receiving element experience similar mobilities. This chapter considers an OFDM system with multiple distributed users as depicted in Figure 14.1, where different users could have significantly different mobility patterns. Via some coordination mechanisms, the signals from different users are assumed to be synchronized on the OFDM block level and the major challenge for receiver design lies on how to deal with the significantly different Doppler distortions on different data streams. In such scenarios, a single resampling operation at the receiver does not suffice to remove the main Doppler distortion of all data streams.

• Section 14.2 introduces a front-end processing module that consists of multiple resampling operations, as proposed in [390, 391].
• Section 14.3 presents one receiver termed as a multiuser detection (MUD) based iterative receiver 0183]. It adopts a frequency-domain oversampling approach to generate discrete samples, on which joint channel estimation and multiuser data detection are carried out in an iterative fashion.
• Section 14.4 presents another receiver termed as a single-user detection (SUD) based iterative receiver [183]. Adopting the front end with multiple resampling branches suggested in Section 14.2, it introduces to each branch a module for multiuser interference (MUI) reconstruction/cancellation prior to data decoding, thus leading ...