Communications to the home via Star QAM

The authors consider a modem capable of delivering 32 Mb/s. In order to minimise the bandwidth requirements a multilevel modulation scheme is used. Due to the likelihood of traffic movement in the vicinity of the microwave paths, the modem must be able to cope with signal fading. The authors describe the principles of the Star QAM modulation scheme, a system which would appear to be well suited to this application, and discuss its features to combat the effects of signal fading. They also detail some of the problems that have been encountered in building a 32 Mb/s Star QAM modem, and present results of simulations. Practical equipment trials at bit rates of up to 4 Mb/s and at a carrier frequency of 1.8 GHz are presented. They also briefly consider issues of frequency reuse and spectrum requirements