Effects of Additive Noise on the Throughput of CDMA Data Communications

this paper considers maximizing the aggregate throughput of a CDMA base station. In earlier work on this problem, Ulukus and Greenstein [9] adjust data rates and transmitter power levels in order to maximize network throughput. Lee, Mazumdar, and Shroff [10] adapt data rates and power allocation for the downlink, and provide a sub-optimal algorithmic solution based on pricing. Sung and Wong [11] assume that the terminals data rates are different but fixed, and maximize a capacity function. Our recent work [4-7] adjusts the power and rate of each terminal to maximize i i T i , the aggregate weighted throughput of a base station. T i b/s denotes the throughput of terminal i and the weight i admits various interpretations, such as priority, utility per bit, or a monetary price paid by the terminal. This research assumes that the number of active terminals is fixed, their data rates are continuous variables to be optimized, and that the system is interference limited (noise is negligible). In the present paper, we set all the =1 and take the data rates to be identical and fixed, but we view the number of active terminals as a key variable to be optimized. We also consider additive noise to be non-negligible, which is essential when out-of-cell interference is significant, and included in the noise term. The research reported in [8] dealt specifically with the case when noise and out-of-cell interference * are negligible, and found that the transmitter power levels should be controlled to achieve power balancing. With power balancing, all signals arrive at the base station with equal power. By contrast, the results in the present paper pertain to the case when noise and interference from other cells are not negligible. We show..