FEC Scheme for a TDM-OFDM Based Satellite Radio Broadcasting System

There are two licenses, 12.5 MHz each, in the S-band for subscription-based, digital satellite-to-vehicle radio broadcasting in the United States. The potential advantages of such a system is that a motorist can enjoy commercial-free music, digital-quality sound and seamless coast-to-coast coverage. One proposal for the broadcast system is to have two satellites covering the continental USA at any given time. 

There will also be terrestrial repeaters in cities where the mobiles cannot see the two satellites. The channels of these systems are largely Rician, Rayleigh and shadow fading. In this paper, we propose a Forward Error Correction (FEC) scheme that is not only robust against fading but also enables a low-delay tuning channel so that minimum tuning delay will occur when a user is switching and selecting programs. 

Our scheme uses multiple source coded bit streams employing different interleaver depths. Large interleavers are used to ensure good decoded signal quality while small interleavers are used to minimize tuning delay. The proposed scheme also ensures that a program will not be interrupted by momentary shadow fades frequently experienced by a motorist when, for example, a vehicle goes under a highway overpass. The impact of interleaver design on the real-time end-to-end delay and overpass problems are analyzed. Finally, the channel code performance in Rician and Rayleigh fading channels are also presented.