Data transmission over HF radio channels using complementary sequences sets

The paper describes an investigation of the system performances of a wide range of adaptive modem architectures based upon uncorrelated sets of complementary sequences (CSs). The aim of the study is to develop an optimum system configuration for the high frequency (HF) mobile radio channel with emphasis being laid upon robust data transmission. M-ary phase shift keying (MPSK) is the modulation scheme employed, although other modulation types are also appropriate. CS sets are shown to be an efficient means of designing modems by. putting their correlation properties to good use. It is concluded that, at baseband, uniform quantisation results in a degradation in the performance of the modem as expected. However at bandpass, an improvement in the performance of the modem at the expense of higher E_b/N₀ values is observed when quantising. Under non-Gaussian and Rayleigh fading conditions, which are more realistic models for the severe conditions on the HF channel, considerable system performance is achieved by using CS sets with larger dimensions (i.e. increased sequence length and/or number of sequences per set). Such a benefit is obtained at the expense of increased redundancy. HF was chosen as a convenient and challenging demonstrator medium; however, in principle, the techniques can be applied readily to other frequency bands.