Optical CDMA random access protocols

The link layer of an optical direct-detection code-division-multiple access packet network is considered. Two of them need pretransmission coordination, whereas the third one does not. Both system throughput and average packet delay are derived and investigated for two different receiver models, namely the correlation and chip-level receivers. Both multiple-access interference and photodetector´s shot noise are taken into account in the analysis. The case where the number of users exceeds the available number of CDMA codes is numerically investigated. Our results reveal that the proposed protocols yield competitive system throughputs when used with the correlation receivers. Further, significant improvement in the throughput is achieved when using chip-level receivers along with the second or third protocol.