Power control by interference prediction for broadband wireless packet networks

A Kalman-filter method for power control is proposed for broadband, packet-switched time division multiple access wireless networks. By exploiting the temporal correlation of co-channel interference, a Kalman filter is used to predict future interference power. Based on the predicted interference and estimated path gain between the transmitter and receiver, transmission power is determined to achieve a desired signal-to-interference-plus-noise ratio (SINR). A condition to ensure power stability in the packet-switched environment is established and proven for a special case of the Kalman-filter method. The condition generalizes the existing one for a fixed path-gain matrix, as for circuit-switched networks. Performance results reveal that the Kalman-filter method for power control provides a significant performance improvement. Specifically, when messages consist of ten packets on average, the 90th and 95th percentile of the SINR by the new method are 3.79 dB and 5.46 dB above those when no power control is in use, and lie just 0.9% dB and 1.14 dB below the upper-bound performance of the optimal power control, respectively, in a system with four-sector cells and an interleaved frequency assignment of a reuse factor of 2/8. In addition, the new method performs noticeably better than the delta-modulation method and a simple scheme that uses the last measurement as predicted interference power. In an example of 8-PSK modulation and average message length of 20 packets, the SINR performance gain by the new method improves the network throughput by about 150% and 70%, relative to no power control and the simple scheme, respectively.