Comparison of WDM/pulse-position-modulation (WDM/PPM) with code/pulse-position-swapping (C/PPS) based on wavelength/time codes

C/PPS is a flexible multibit per symbol modulation format. It has the same architecture as PPM, but has greater bandwidth efficiency. It can utilize a code set to maximize the data rate of a particular user or distribute its codes to various users at different data rates. In the latter case, it is important to consider the associated effects on QoS. C/PPS is less sensitive to synchronization than PPM because the code defines the slot, independent of time-of-arrival. More research on virtual quadrants and multiuser detection is needed for C/PPS because the C/PPS transmission is broadcast-like and all decoders have signals.