Adaptive coding for joint power control and beamforming over wireless networks

Abstract

Co-channel interference and time varying nature of channel are two main impairments that degrade the performance of a wireless link. Power control, antenna beamforming and adaptive coding are the approaches for improving the performance in wireless networks by appropriately allocating resources such as energy in time and space domains. It is hard for traditional joint power control and beamforming with fix coding to guarantee each users' quality of service (QoS) during the deep fading. In this work, we introduce adaptive coding for joint power control and beamforming. We use the theory of "water filling" in time domain. When the channels are bad, we use lower coding rates and lower source rates to guarantee the Bit Error Rate (BER). When the channels are good, we use higher coding rates and higher source rates to increase the overall network throughput. We use the rate compatible punctured convolutional (RCPC) codes for adapative coding, because lower rate codes of RCPC codes are compatible with higher rate code and only one RCPC code transceiver is needed for the different rates. At each time, the network throughput is a constant to keep the system performance. For each user, the time average throughput is maintained as a constant to ensure the fairness. From the simulation results, it is shown that our schemes reduce up to 90% of overall transmitted power and increase the network throughput about 40% at BER equal to 10^-3 and 10^-6. We also introduce a sub-optimal algorithm that has the complexity of only <i>O</i>(<i>N</i>²<i>logN</i>) with relative good performance.