Prioritized Throughput Maximization via Rate and Power Control for 3G CDMA: The 2 Terminal Scenario∗

Variable spreading gain (VSG) CDMA allows data terminals to operate at dissimilar transmission rates. With this technique, the chip rate is common to all users, but the spreading gains vary. Our work is relevant to the uplink of a single-cell VSG CDMA system, in which each terminal’s data throughput is weighted differently in calculating the network throughput. We seek for each active user a power level and transmission rate which will maximize the network’s aggregate weighted throughput. This paper focuses on the two-terminal, interference-limited scenario. The development is entirely analytical, based on optimization theory. One of the principal results is that the favorite terminal should always operate at the highest data rate. The optimal bit rate of the other terminal depends on the ratio of the minimum allowable spreading gain to the square root of the priority coefficient. Only when this ratio is large enough, is it optimal for both terminals to operate at the highest permissible data rate. In either case, we provide equations whose solutions lead to the optimal power ratios.