Accurate Analysis of Double-Weight O-CDMA Scheme with the Same Bit-Power Assumption

The use of optical codes with variable weight has been considered as a desirable candidate to provide differential quality-of-service in optical code division multiple access (O-CDMA). It is because code weight plays a dominant role in determining the performance of O-CDMA codes as heavy-weight codes always outperform light-weight codes under the conventional assumption of identical power in every optical pulses (i.e., same chip power). In this paper, we assume the use of optical codes with same power in each bit duration (i.e., same bit power). In other words, heavy-weight codes have less power per chip than light-weight codes. For illustration, we focus our work on double-weight codes and compare the performance between heavy-weight and light-weight codes under both same-chip-power and same-bit-power assumptions. Most importantly, we develop a new and accurate analytical method to evaluate the performance of these double-weight codes. Validating with computer simulation, our results show that heavy-weight codes do not always perform better than light-weight codes under the same-bit-power assumption.