Asymmetry in optical wireless links

The bit error rate performance of IRDA (IR data association) links when influenced by physical layer and channel asymmetries are examined. Physical layer asymmetries are possible due to component variations, ambient noise variations, and third party interference. It is shown how such asymmetries cause differential link bit error rates, which in turn result in throughput degradation at the link and higher layers. A model is developed for the asymmetries incorporating PHY layer and LINK layer parameters. The condition for symmetry in optical wireless links is derived. It is demonstrated that link layer throughput asymmetries are possible as a result of physical layer parameter asymmetries. The magnitude of such throughput asymmetries is calculated. Examples are analysed based on some typical user model environments where asymmetries may take place. Results based on a model of the IRDA protocol stack are given