Next-generation indoor infrared LANs: Issues and approaches

In this article the design issues for the next-generation wireless infrared systems are discussed. An advanced infrared system is proposed to provide reliable high-speed short-range wireless communication throughout indoor en vironments. In the physical layer, the range of communication is extended f or L-PPM infrared links by using repetition rate coding, which greatly incr eases the symbol capture probability at the receiver. Repetition rate codin g is used in an adaptive way to update the data rate over a channel based o n the channel parameters. The receiver symbol capture characteristics and s ignal-to-noise ratio gain due to the use of a repetition rate scheme are pr esented. The infrared media access control layer must be designed to establ ish fair and robust communications over the proposed physical layer. The fa irness problem is described in detail, including the impact of the topology on the performance of the wireless system. Balanced media access methods a re presented as a solution to the fairness problem. The link access control layer uses retransmission to provide reliable connections over infrared li nks.