Coding for frequency hopped spread spectrum satellite communications

A nonlinear diversity combining scheme using the Viterbi ratio threshold (RT) technique is discussed. Performances of the RT diversity combiner in fast frequency hop spread spectrum systems with M-ary frequency shift keying with and without additive white Gaussian noise (AWGN) are analyzed. Exact bit error probabilities are computed and relationships between system performance and parameters such as RT, diversity order, and thermal noise level are illustrated. Performances under band multitone jamming and partial band noise jamming are compared. Performance of M-ary differential phase shift keying (MDPSK) signalling in the presence of both tone jamming and AWGN is described. Larger signal sets than in a previous report are considered along with skewed differential phases with unequal decision regions. The error performance when a frequency offset exists between a jamming tone and a MDPSK carrier is also considered. Error correlation in DPSK demodulation is examined in terms of its effects on the block and decoded error probabilities, which are derived and computed for AWG and worst-case partial band noise. Comparisons are made with the approximate block and decoded error probabilities based on a memoryless model which ignores the error correlation. The effectiveness of interleaving in improving the error performance under various conditions is addressed.