Adaptive spreading and channel coding gain control and its experimental results in broadband DS-CDMA reverse link

Abstract

The paper proposes adaptive spreading and channel coding gain (ASCG) control with QPSK data modulation according to the instantaneous received signal-to-interference plus noise power ratio (SINR) of each packet duration, and presents experimental results using this scheme in broadband DS-CDMA wireless access in the reverse link. In the implemented broadband DS-CDMA transceiver with a 40 MHz bandwidth, a combination of turbo coding gain and the number of multiplexed codes for the spreading factor of SF = 4 (i.e., equivalent spreading gain) is adaptively changed based on the measured received SINR using a dedicated pilot channel over the packet duration of 0.5 msec to provide the maximum throughput according to the channel conditions in a multipath fading channel. Based on field experiments in real multipath fading channels, we observe a large number of multipath (i.e., more than 10 paths) components, which are approximated as an exponentially decayed power delay profile model in a 40 MHz bandwidth. In such multipath fading channels, we confirm that the proposed ASCG control properly operates according to the measured instantaneous received SINR, and, as a result, a throughput of greater than 20 Mbps is achieved at the average measured received SINR per antenna of approximately 5.5 dB.