Mitigation Techniques against Ionospheric Scintillation on UHF Satellite Links

The effects of ionospheric scintillation on the performance of a UHF (240 MHz) satellite communications link are deduced from experimental data. Scintillation data from the polar cap region and the auroral oval region taken during the 1980-81 period are presented. The performance of the Air Force Satellite Communications (AFSATCOM) digital data satellite link is described for two high latitude sites. The AFSATCOM system uses noncoherent binary frequency shift keying (FSK) modulation at 75 b/s and matched filter detection. Performance is described in terms of bit-error-rate (BER), character-error-rate (CER), and message-error-rate (MER). The recorded bit stream of the experimental data was used as the basis for the evaluation of several scintillation fading mitigation techniques. These techniques, which do not involve coding and interleaving, are shown to improve link performance significantly for the mitigated messages. The penalty paid in reduced channel throughput rate is moderate.