Transmit power adaptation for CDMA communication systems using successive interference cancellation

摘要

Transmit power adaptation for DS/CDMA systems is disclosed for a CDMA system that utilizes a successive interference cancellation receiver on fading channels. The transmission power is adapted in response to channel variations to achieve an arbitrary power profile for received signal powers at the system base station. That is, the received signal powers are distributed with some factor x_i's given as:S_Rⁱ=S_R⁽¹⁾x_i, (i=2, 3, . . . , K and x₁=1)where K is the number of users and S_R⁽ⁱ⁾ is the received signal power of the user having the i^th strength, and wherein user strengths are ranked in the order of estimated channel gains. The factor x_i gives a measure of the disparity between the received power levels. The channel is estimated at both the transmitter and receiver. In one embodiment, the factors, x_i, for distributing the signal powers are selected such that the average BER for each user is minimized. In another embodiment, the factors, x_i, for distributing the signal powers are selected such that, after successive interference cancellation, an instantaneous BER for all users is equal.