High-rate direct-sequence spread spectrum

Direct-sequence spread spectrum is popular for commercial wireless local-area networks, because license-free operation is permitted in certain frequency bands. The extensive development of equipment for such applications makes it attractive to investigate the use of the commercial technology for military communication networks. However, because of the small processing gain that is common in the signal designs for commercial direct-sequence spread spectrum, most commercial waveforms are not suitable for channels with interference, such as multiple-access channels. We investigate a class of proposed commercial high-rate spread-spectrum signal designs for which the spreading is derived primarily from nonbinary orthogonal or quasi-orthogonal data modulation. The multiple-access capability is evaluated as a function of the signal-to-interference ratio, and the effects of multipath interference are investigated.