23 January 1998 High-capacity burst communications modem for LMDS and VSAT applications
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Proceedings Volume 3232, Wireless Technologies and Systems: Millimeter-Wave and Optical; (1998) https://doi.org/10.1117/12.301029
Event: Voice, Video, and Data Communications, 1997, Dallas, TX, United States
Abstract
Emerging wireless telecommunication systems, including the terrestrial LMDS (Local Multipoint Distribution System) and next-generation communication satellite systems (e.g., SpacewaySM, et al.) are driven by economics to require a burst-transmission protocol for their return links (i.e., subscriber-to-hub or subscriber-to-satellite links). Limited spectral bandwidth to support these return links demands that they achieve high spectrum efficiency, measured in terms of bps/Hz (bits-per-second-per-Hertz). High-order modulations offer practical spectrum-efficient solutions for continuous links, but technical difficulties associated with phase- coherent demodulation of high-order burst signals have previously precluded these modulations as a viable option. In fact, state-of-art burst signal demodulation is currently limited to differentially-detected QPSK (DQPSK). Although so- called block-coherent demodulators generate acceptable symbol- error rates, they introduce such strong symbol-to symbol correlation as to preclude efficient soft-decision decoding. In summary, new wireless links demand burst modems with bandwidth-efficiency and power-efficiency superior to currently available technology. SiCOM research has developed a practical burst demodulator compatible with both high-order modulations and soft-decision maximum-likelihood decoding. This paper describes the capabilities and characterizes the performance of this revolutionary demodulator. In particular, detailed performance comparisons are provided between the current state-of-art burst demodulator/decoder, using DQPSK and Reed-Solomon FEC (forward error correction), and SiCOM's new burst demodulator using 8PSK with concatenated TCM (trellis-coded modulation) and Reed-Solomon FEC. For ATM (asynchronous transfer mode) cell transfer, with identical link constraints, (i.e., signal-to-noise ratio, bandwidth, and bit-error rate), the new modem supports fully 25% higher information transfer rates. For message traffic with less- critical latency constraints, message-specific interleaving easily provides orders-of-magnitude improvement in data quality over the DQPSK/RS approach, with identical bandwidth and SNR (signal-to-noise ratio).
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John M. Liebetreu, John M. Liebetreu, Bruce A. Cochran, Bruce A. Cochran, Rene Savalle, Rene Savalle, "High-capacity burst communications modem for LMDS and VSAT applications", Proc. SPIE 3232, Wireless Technologies and Systems: Millimeter-Wave and Optical, (23 January 1998); doi: 10.1117/12.301029; https://doi.org/10.1117/12.301029
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