Adaptive time and frequency resource assignment with COFDM for LMDS systems

In this letter, a wireless local multipoint distribution system (LMDS) at m illimeter waves for the last-mile broad-band distribution to users of inter active services is investigated. The system analyzed employs a coded orthog onal frequency-division multiplexing transmission scheme with frequency-div ision multiplexing (FDM) and/or time-division multiplexing techniques and a daptive carrier allocation to counteract the effects of the wireless commun ication channel, The idea of deploying the reverse channel (exploited by th e user for interactivity purposes) to provide channel information to the br oadcasting transmitter is introduced. System performance is evaluated for a n urban microcellular radio system in an actual propagation environment and the choices of the optimum multiplexing technique and carrier allocation a lgorithm are discussed in the case of ideal feedback. It is found that a pure FDM technique combined with an adaptive carrier all ocation algorithm giving priority to users having the largest path loss lea ds to the best performance.