Downlink Weight Control in Tdd/sdma Based on Prediction of Radio Channel Changes

A multibeam adaptive antenna at a basestation can separate spectrally and temporally overlapped signals in a TDMA mobile communication system. Thus, we can achieve space division multiple access (SDMA), which increases the channel capacity. For an uplink channel, weight vectors can be determined by applying a conventional method. In this paper, we consider the weight vectors for a downlink channel in a TDD system. Although the uplink and downlink channels have a common frequency band, we cannot neglect the changes in channel characteristics depending on the radio environment. We present two schemes to determine the downlink weight vectors.