Combined frequency-time domain power adaptation for CDMA communication systems

摘要

Practical transmission power adaptation in multicarrier code division multiple access (MC-CDMA) communications is using either a frequency domain technique or a time domain technique or a combined frequency and time domain technique in response to channel variations. With frequency domain power adaptation, the transmission power is allocated over the N' (1<=N'<=N) strongest subcarriers rather than over all possible N subcarriers, where the strongest subcarriers are understood to exhibit the highest channel gains. A substantially optimal N' can be chosen so that the average bit error rate (BER) is minimized. In the time domain power adaptation technique, transmission power is adapted so that the desired signal strength at the receiver output is maintained at a fixed level. In the combined time and frequency domain adaptation technique, the transmission power is first allocated over the N' (1<=N'<=N) strongest subcarriers rather than over all possible N subcarriers and then it is adapted so that the desired signal strength at the receiver output is maintained at a fixed level.