Combined power and rate adaptations in DS/CDMA communications over fading channels

We propose a combined power and rate adaptation scheme in direct-sequence code division multiple access (DS/CDMA) communications over Nakagami fading channels. The transmission power proportional to G_pⁱ is allocated to the data transmission of user i, where G_i is the channel gain for user i, and p is a real number, and the data rate (i.e. spreading gain) is jointly adapted so that a desired transmission quality is maintained. We analyze the average data rate of the proposed adaptation scheme subject to fixed average and peak transmission power constraints. Our results show that the proposed joint adaptation scheme has considerable performance improvements over power only adaptation and rate only adaptation for a range of system parameters.