Quasi-Walsh PN sequences and their applications in robust CDMA communication systems

Abstract

Systems of quasi-Walsh functions are developed which simultaneously enable multiple access as well as secure communication and jamming resistance. In this system, a pseudo random sequence of diagonal isometries post multiplies a Hadamard matrix, thereby generating the orthogonal direct spreading sequences. Minimal mutual interference is a consequence of the resulting orthogonal spreading. Utilizing bit-by-bit distinct orthogonal codes gives the added benefit of high signal hiding capability and jamming resistance. An encoding scheme is presented which uniquely determines the actual quasi-Walsh system in use.