Asymmetry in optical wireless links

The bit error rate performance of IrDA links when influenced by physical la yer and channel asymmetries are examined. Physical layer asymmetries are po ssible due to component variations, ambient noise variations, and third par ty interference. It is shown how such asymmetries cause differential link b it error rates, which in turn result in throughput degradation at the link and higher layers. A model is developed for the asymmetries incorporating P HY layer and LINK layer parameters. The condition for symmetry in optical w ireless links is derived. It is demonstrated that link layer throughput asy mmetries are possible as a result of physical layer parameter asymmetries. The magnitude of such throughput asymmetries is calculated. Examples are an alysed based on some typical user model environments where asymmetries may take place. Results based on a model of the IrDA protocol stack are given.