Orthogonal Code Hopping Multiplexing for Downlink in Spread Spectrum Communications

A statistical multiplexing scheme in orthogonal downlinks is proposed to accommodate more downlink orthogonal channels than orthogonal codewords for mobile stations. The number of allocable downlink orthogonal channels depends on the average burstiness of the channels. The statistical multiplexing scheme is called here as the orthogonal code hopping multiplexing (OCHM). Since the OCHM uses a pre-allocated independent hopping pattern for each mobile station (MS), the number of transactions for channel allocation and de-allocation can be smaller than the conventional downlink orthogonal multiplexing scheme. Since the number of available codewords in orthogonal code for OCHM is limited (for cdmaOne, it is 64) and the hopping patterns are mutually independent, the hopping patterns for two or more synchronous downlink channels may collide. In this case all the encoded symbols colliding in the downlink channels are not transmitted (punctured) except when all the encoded symbols are the same. The punctured (not transmitted) encoded symbols are recovered at the receiver by channel decoding.