Channel measurement decoding for troposcatter communications

The object of this program is to theoretically investigate and experimentally verify the performance improvement possible by the use of channel-measurement (soft-decision) information when decoding an interleaved (24,12) Golay code. The experimental results obtained during this effort indicate that under certain conditions, such as pulse jamming, significant gains can be achieved by the use of channel measurement decoding. For typical multipath profiles, coding gains in the 5 to 10 dB range have been achieved by fairly simple binary decoding techniques. Unfortunately, the predicted theoretical gains due to the use of channel measurement decoding have not been achieved by the experimental results. While channel measurement decoding did offer a 3-dB gain over binary decoding for flat fading, this gain is well below the theoretical prediction of 7.2 dB. The discrepancy between the theoretical and experimental results is still an open question which may be resolved by future work in this area. Nevertheless, in the presence of pulse jamming, channel measurement decoding doubled the effective pulse duration that can be handled by the Golay code. This result is in agreement with theory and a strong indication of the importance of optimum decoding techniques in an ECCM environment.