Underwater acoustic communication channels are prone to external interference from various sources, such as the interference from marine animals, human activities and sonar operations. Malicious jammers could also inject interfering signals into the communication channel to destroy the communication link. External interference could incur significant performance degradation if not accounted for.
This chapter focuses on explicit mitigation of an external interference with a certain time duration and bandwidth. One example of the type of interference under consideration is the waveform from sonar users, as depicted in Figure 12.1. Exploiting the prior information on the time duration and frequency band of the interference, a parameterized interference cancellation approach will model the interference explicitly via a number of parameters, where the number of parameters is equal to the time-frequency-product of the interference. With the parameterized interference model, an iterative OFDM receiver with interference cancellation is designed to perform data processing and interference estimation/cancellation iteratively. The chapter is organized as follows.