DS-CDMA and adaptive modulation based TDMA dual mode scheme for high speed data transmission service in wireless multimedia communication systems

This paper proposes a direct sequence-code division multiple access (DS-CDMA) and adaptive modulation based time division multiple access (TDMA) dual mode system to achieve high speed data transmission services in wireless multimedia communication systems. In the proposed system, the TDMA sub-frame is employed to increase the maximum bit rate only for data terminals of which modulation parameters are adaptively updated according to the received CIR so as to sufficiently utilize the spectral resource. Moreover, dynamic channel assignment (DCA) and multilevel transmit power control (MLTPC) are also employed to mitigate interference power in the cellular environment. Computer simulation confirms that the proposed system can reduce average normalized delay time by about 1/25 compared with the CDMA systems with its data rate of 64 kbps without so much decreasing voice capacity