Performance analysis of adaptive rate and power control for data service in DS-CDMA systems

We consider rate and power adaptations for homogeneous data traffic in the uplink of direct-sequence code-division multiple-access (DS-CDMA) cellular systems, where the transmission power and the transmission rate of each data user are adapted in accordance to the random activities of users and varying data traffic. The performances in terms of data throughput, average packet delay and average power consumption, are analyzed and compared between adaptive rate and power control schemes. In the rate-adaptive system, the received power of each data user is fixed while the transmission rate is dynamically adjusted to maintain a target bit energy-to-equivalent noise spectral density ratio (E/sub b//N/sub e/). On the other hand, in the power-adaptive system, the transmission rate is fixed and the received power is adapted to maintain the target E/sub b//N/sub e/. Analytical results show that the rate-adaptive scheme provides a significant power gain and lower average packet delay over the power-adaptive scheme for the data users to achieve the same throughput.