SYMBOL RATE AND MODULATION LEVEL-CONTROLLED ADAPTIVE MODULATION TDMA TDD SYSTEM FOR HIGH-BIT-RATE WIRELESS DATA-TRANSMISSION

This paper proposes a time-division multiple-access/time-division dupl ex (TDMA/TDD)-based symbol rate and modulation level-controlled adapti ve modulation system for high-bit-rate data transmission. The proposed system controls both the symbol rate and modulation level for the nex t transmission time slot according to the estimated carrier power to n oise spectral density ratio (C/N-0) and delay spread for the time slot to achieve higher bit rate and higher transmission quality as well as higher delay-spread immunity. It is demonstrated by computer simulati on and laboratory experiments that the proposed system can achieve a h igher average bit rate with higher transmission quality in comparison with the fixed-rate quaternary phase-shift keying (QPSK) system and mo dulation level controlled adaptive modulation system in both flat Rayl eigh and frequency-selective fading environments. The simulated and ex perimental results also show that the proposed adaptive modulation tec hniques can be applied to 1-2-Mb/s indoor and outdoor microcellular sy stems with its delay spread of up to 250 ns and its terminal mobility of up to pedestrian speed without employing any special antifrequency- selective fading techniques, such as the adaptive equalizer and space diversity.