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The development of digital land mobile communication techniques makes it possible to use most of the modulation techniques. This paper proposes an adaptive modulation/TDMA scheme to achieve high capacity personal multimedia communication systems. TDMA is used to cope with various bit rate for multimedia services, and the modulation scheme is selected from 1/4-rate QPSK, 1/2-rate QPSK, QPSK, 16QAM and 64QAM according to the received C/I/sub c/ (power ratio of the desired signal to the co-channel interference) and the delay spread. Computer simulation confirms that the proposed system can achieve 3.5 times higher spectral efficiency than that of the conventional QPSK systems at the outage probability of 10%, and the proposed system is also effective to improve the delay spread immunity.
Sampei et al. (Tue,) studied this question.