A multiple-sequence spread spectrum system for powerline communications

By using a multiple-sequence spread spectrum technique employing sequences generated by linear feedback shift registers, relatively high data rates over powerlines together with low error rates and robustness can be achieved. The method admits easy incorporation of a threshold decision scheme whereby erasures as well as errors are declared, enabling detection of poor channel conditions. By incorporating an informationless sequence of the same period in quadrature with the information-bearing sequence, carrier recovery, spreading sequence synchronization and block code synchronization can all be achieved jointly. Individual symbols can be detected using Hadamard Transforms, which can be efficiently implemented in either software or hardware. Also, the system is "downward compatible" with "conventional" direct sequence spread spectrum schemes in which a narrowband binary signal is mixed with an informationless linear spreading code.