Performance of Diversity Combining Techniques for FH/MFSK in Worst Case Partial Band Noise and Multi-Tone Jamming

Diversity combining techniques to be used in frequency hopped MFSK spread spectrum communication systems with explicit redundant transmission are examined. Expressions are given for the conventional linear noncoherent combining technique to compute the BER performance under worst case partial band noise jamming. Results obtained indicate that the conventional linear combining is far from optimum in the jamming environment. In order to combat the worst case jammer, several non-linear algorithms have been examined through computer simulation to obtain the BER performance for comparison. A practical anti-jam combining algorithm is recommended. When binary convolutional code is used in conjunction with M-ary FSK modulation (M ≫ 2), soft decision decoding can be accomplished by means of a M-ary to binary metric conversion algorithm. Modem BER performance based on this algorithm has been obtained for the 8-FSK waveform through computer simulation and is presented in this paper.