Optical synchronous PPM/CDMA systems using co-channel interference cancellation

The performance of direct-detection optical synchronous code-division multiple-access (CDMA) systems with pulse position modulation (PPM) signaling (PPM/CDMA) using modified prime sequence codes as signature sequence codes with co-channel interference canceller is analyzed under the assumption of number-state light field where the background noise is negligible. Modified prime sequence codes that exhibit a grouping characteristic are employed for optical synchronous CDMA systems. The upper bound on the bit error probability of optical synchronous PPM/CDMA systems with co-channel interference canceller is derived, and the bit error probability of optical synchronous PPM/CDMA systems are evaluated. We compare the optical synchronous PPM/CDMA systems with co-channel interference canceller to that of the optical synchronous PPM/CDMA systems without co-channel interference canceller and to those of optical synchronous OOK/CDMA systems with and without co-channel interference canceller. We show that optical synchronous PPM/CDMA systems with co-channel interference canceller have better bit error probability performance than other optical synchronous CDMA systems.