Adaptive Forward Error Control and Time-Frequency Resource Sharing Techniques for Digital Satellite Systems

Two hybrid schemes of time-frequency resource sharing to increase the rain margin of Ku and Ka-band satellite systems are proposed. Scheme 1 requires sharing a small pool of bandwidth for adaptive forward error control coding, small pool of time-frame for rate reduction and a portion of low frequency TDMA back-up frame for downlink transmission to the rain affected stations. Scheme 2 utilizes variable rate modulation and forward error correction, shares a small pool of time frame for rate reduction and a portion of low frequency TDMA back-up frame. Effective usable capacities of the system using these schemes are calculated The results obtained are compared with other adaptive schemes. Preliminary analysis shows that the utilized capacity of scheme 1 exceeds 99% of the effective usable capacity possible if it never rains for an outage of 0.05% and fade margin of 2.5 dB. For scheme 2 similar performance is achievable at a fade margin of 1.5 dB.