Optical wireless systems, both indoor and outdoor, can offer data rates in excess of those available with RF systems. However, this is usually over a small area in the context of an indoor optical wireless, or over a small range of angular alignments for outdoor Free Space Optics (FSO) systems. Constant radiance considerations play a major part in these limitations, as do the receiver sensitivity for direct detection optical systems. In comparison radio channels operate close to the theoretical limits of channel capacity by using complex modulation, coding and high speed signal processing. In this paper an analysis of the performance of a cellular optical wireless system is undertaken, and opportunities to increase performance examined. More complex modulation schemes appear to offer significant benefits, mainly due to the reduction in channel bandwidth, and the attendant increase in allowable detector area.