A CHANNEL EQUALIZATION TECHNIQUE ON A TIME-DIVISION DUPLEX CDMA TDMA SYSTEM FOR WIRELESS MULTIMEDIA NETWORKS

A channel equalization technique on a time division duplex CDMA/TDMA s ystem for wireless multimedia networks is investigated, and the bit er ror rate performance of the system is theoretically analyzed. The assu med network connects mobile terminals to a node of ATM based high spee d LAN through a radio central unit. Only human interface facilities ar e implemented into the terminal so that users access integrated servic es through the node of the network. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit human inte rface signals and the downlink employs a TDMA scheme to transmit displ ay interface signals. Both the CDMA and the TDMA signals occupy the sa me frequency band. To mitigate bit error rate degradation due to fadin g, the radio central unit estimates the impulse response of the channe l from the received CDMA signals and subtracts the replica signal to c ancel the major intersymbol interference (ISI) component. Numerical re sults using the Nakagami-m fading model and recent propagation measure ments show that the proposed TPC technique compensates the fading atte nuation and the proposed CEQ cancels the major ISI component. The bit error rate performance of the downlink with the proposed CEQ is superi or to that with the DFE by 12 dB of the symbol SNR at the BER = 10(-6) over a specular channel, and the system with the proposedCEQ achieves a BER = 10(-6) at the symbol SNR = 12 dB. Furthermore, the channel eq ualizer is implemented without increases in complexity of the terminal because all the processing on the equalization is carried out only in the radio central unit.