THE LABORATORY PERFORMANCE OF THE ANDEFT/SC-320 MODEM WITH AN HF MULTIPATH FADING CHANNEL SIMULATOR
GENERAL DYNAMICS/ELECTRONICS ROCHESTER NY
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A laboratory test program to evaluate the performance of the ANDEFT SC-320 frequency-differential PSK HF modem operating with a HF Multipath Fading Channel Simulator is described. The modem was operated in six modes 4800 bps, 2400 bps4-phase, and 2400 bps2-phase diversity and nondiversity and performance was measured for simulated HF path conditions for four multipath delay spreads 0.5, 1, 2, and 5 ms, three fading bandwidths 0.2, 0.5, and 2.0 Hz, and three bit-energy-to-noise-density ratios 10, 20, and 40 db. The resulting data shows bit error rate performance at 4800 bps with diversity between 0.00001 and 0.001 for multipath delay spreads between 0.5 and 2.0 ms, respectively, and a fading bandwidth of 0.2 Hz. Increasing multipath delay spread causes a much larger degradation in bit error rate than increasing fading bandwidth. Dual signal source reception diversity and dual inband frequency diversity are effective in producing improved bit error rates, especially at the smaller multipath delay spreads, i.e., 2 ms or less. Operation at 2400 bps4- phase which includes both diversity techniques for 4-way diversity produced the best results. The multipath-limited error rate was so low for some channel parameters that it could not be established in 10 to the 7th power bits. For multipath-limited conditions, this mode out performed the 2400 bps2-phase mode which does not include the inband diversity feature.
- Radio Communications