Next-generation indoor infrared LANs: issues and approaches

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 environments. In the physical layer, the range of communication is extended for L-PPM infrared links by using repetition rate coding, which greatly increases the symbol capture probability at the receiver. Repetition rate coding is used in an adaptive way to update the data rate over a channel based on the channel parameters. The receiver symbol capture characteristics and signal-to-noise ratio gain due to the use of a repetition rate scheme are presented. The infrared media access control layer must be designed to establish fair and robust communications over the proposed physical layer. The fairness problem is described in detail, including the impact of the topology on the performance of the wireless system. Balanced media access methods are presented as a solution to the fairness problem. The link access control layer uses retransmission to provide reliable connections over infrared links.