Cyclic shifted-and-extended codes based on almost perfect autocorrelation sequences for CDM transmission scheme

For future cellular communication systems, we have developed a code-division-multiplexing (CDM) transmission scheme based on cyclic shifted-and-extended (CSE) codes generated from a basic code with superior autocorrelation characteristics in order to realize seamless communication in a high-speed mobile environment. In this paper, an almost perfect autocorrelation sequence is used as the basic code and its autocorrelation values are zero except at zero and middle shifts. Moreover, we propose an elimination technique for interference caused by the correlation value at the middle shift. The proposed technique can realize perfect correlation characteristics within the cyclical shifted chips by adding a simple calculation at a receiver. The proposed scheme is evaluated by computer simulations in terms of the bit-error-rate performance for various code lengths of the basic code.