Performance evaluation of asynchronous DS/CDMA communications using unipolar codes

In CDMA communications with radio waves, binary spreading sequences are used as bipolar codes taking +1 or -1. On the other hand, in on-off keying modulation such as optical communications, spreading sequences are used as unipolar codes taking 1 or 0. In this paper, performances of asynchronous SIK (sequence inversion keyed) DS/CDMA systems using unipolar codes are evaluated and compared with normal CDMA systems using bipolar codes.