We have previously introduced modulation and coding schemes that permit the simultaneous reception of a basic message stream by receivers with a wide range of capabilities and an additional message stream by more capable receivers. In a tactical military application, the basic message may represent a voice message, while the additional message may correspond to a digitized image. We investigate adaptive modulation and coding techniques based on our previous schemes, and we apply the adaptive techniques to a cellular communication system that employs direct-sequence spread-spectrum multiple access, also known as code-division multiple access (CDMA). In a cellular CDMA system each mobile terminal experiences variations in both the received signal strength and the interference. We show that by adapting the parameters of the modulation and coding to the signal-to-interference ratio, the throughput can be increased for the additional message while maintaining an acceptable error rate for the basic message.
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