Title :
2.4 kbit/s adaptive serial modems for HF skywave paths
Author :
Whittemore, M.J. ; Currie, J.C. ; Mays, L. ; Gilliver, J.P.
Abstract :
It is only recently that the processing power required by adaptive modems of this type has been available from digital signal processors (DSPs) suitable for use in modems. This is especially true in the case of a channel estimating modem of the type described, where a near-maximum likelihood detector (NMLD) is employed. Prototype 2.4 kbit/s modems have been developed with the aim of achieving the best possible performance on HF skywave paths subject to multipath, fast fading and interference. Of particular interest are paths subject to high auroral absorption effects, where fade rates of 5 to 10 Hz are not uncommon. The channel estimator plus near-maximum likelihood detector system proposed and developed by Clark, Asghar and McVerry (1981) was chosen as the structure best able to cope with fast fading conditions.<>
Keywords :
digital communication systems; ionospheric electromagnetic wave propagation; modems; radio equipment; radiowave propagation; 2.4 kbit/s; DSPs; HF communication; HF skywave paths; adaptive serial modems; auroral absorption effects; channel estimating modem; digital signal processors; digitally encoded speech; fast fading; interference; multipath; near-maximum likelihood detector; Digital communication; Ionospheric electromagnetic propagation; Modems; Radio communication equipment; Radio propagation;
Conference_Titel :
HF Radio Systems and Techniques, 1988., Fourth International Conference on
Conference_Location :
London, UK
Print_ISBN :
0-85296-358-0
