Investigation into adaptive-rate modems for meteor burst communication

Current meteor burst communication systems operate at constant bit rates of 4 kbit/s and are limited to average throughputs of 50 bit/s. The paper documents the design and implementation of an adaptive-bit-rate modem for optimising the throughput. A novel extension of differentially encoded binary phase shift keying is proposed so that two frequency division multiplexed baseband channels can be transmitted: a main channel for the data and an auxiliary channel for conveying bit rate change information. In this way, two modems, one at each end of the link, can automatically adapt to a new operating speed without the intervention of a host computer. The results prove that the two channels can operate independently with minimal mutual interference. A theoretical improvement in bit rate of 18 times over the fixed-bit-rate modem is possible