Side information for iterative demodulation and decoding of frequency-hopped PSK in partial-band jamming

Accurate side information, such as carrier phase or signal and noise levels, is necessary to attain optimal performance in iteratively decoded systems. It becomes even more crucial in the presence of partial-band jamming. This paper concentrates on two aspects of side information for iterative demodulation and decoding of the frequency-hop communications with partial-band jamming: the detection of the jamming signals in a dwell interval and the appropriate scaling of channel values for input to the decoder with and without jamming. The system model includes convolutional coding, interleaving and differentially encoded phase shift keying. A trellis-based iterative receiver is used to deal with the random, unknown phase offset experienced in each hop. The outputs of the demodulator are also used to detect the presence of jamming in each dwell. The detection scheme is shown to perform well with noticeable improvement in the probability of false alarm and probability of detection throughout iterations. Furthermore, for hops of sufficient length, performance approaches obtained perfect side information.