Turbo Code Performance over Aeronautical Channel for High Rate Mobile Satellite Communications

This paper presents results from analysis into the performance of Turbo Codes over the aeronautical satellite channel. Currently, only limited services (voice, fax, low rate data) are available for aeronautical travelers. A major constraint is the cost of providing an aircraft qualiied antenna with high gain. This limits the data transmission rates that can be supported. In the future, more powerful spot beam satellites with greater EIRP and G/T will provide high rate data services to ground based users and similar services will become feasible for air travelers. In parallel with developments of satellite technology, turbo coding has been proven to be a major advance in power eecient transmission for satellite communications. A key problem arises for high rate transmissions over the aeronautical channel due to the diierential delay between the line of sight path and the reeected diiuse component gives rise to frequency selective fading. The bit error rate performance is found to degrade signii-cantly over the aeronautical channel due to inter-symbol-interference. The eeect of equalization is considered as a technique to reduce inter-symbol-interference (ISI). The potential beneets of equalisation are discussed and some results presented which indicate that Turbo Coding greatly reduces sensitivity to frequency selective fading and hence shows that equalisation is not necessarily required. The channel interleaving is known to produce signiicant improvements by utilizing time diversity to mitigate the eeects of fading. Turbo coding has an in-terleaver built in to its structure which provides good under fading conditions.