Video image transmission over mobile satellite channels

Abstract

Abstract This paper addresses the transmission of low bit-rate video image sequences through mobile satellite channels to provide portable communications services to remote areas. The particularly challenging aspects of this transmission channel include (1) rapid fading and log-normal shadowing, (2) low signal-to-noise ratio (SNR) due to the noise-limited channel, (3) the satellite's geostationary orbit which incurs a large 250 ms roundtrip propagation delay, (4) limited existing bandwidth near 2 GHz; the video service is to overlay existing Mobile Satellite (MSAT) voice service using a minimum number of 6 kHz (analog bandwidth) channels, and (5) the use of travelling-wave-tube amplifiers which preclude the bandwidth-efficient quadrature amplitude modulation (QAM) proposed for terrestrial high-definition TV (HDTV) broadcast. In the proposed concatenated system, the inner codec is compatible with both voice as well as future-oriented error-resilient, scalable video compression schemes. The key issues are the joint design of on-line channel estimation, soft-decision decoding, trellis-coded modulation (TCM), interleaving depths, and error correcting codes. We have shown through end-to-end bit-level simulation, that highly reliable transmission of 24 and 64 kbps video (H.263) can be realized at 15 and 40.5 kBd, respectively, with low delay, power and modest overall system complexity.