A combined rate/power/cell control scheme for delay insensitive applications in CDMA systems

Abstract

A novel combined rate, power and cell (R/P/C) control scheme that gracefully implements congestion control, is proposed and studied. We consider the reverse link in a CDMA network with a high degree of traffic fluctuations spatially with time, as would be the case in future wireless systems. Our scheme attempts to reduce the high interference power variations among cell-site antennas that can exist in a real network. The transmission rates of those users in the congested (non-congested) cells are decreased (increased) providing the required average throughput among users; hence, the proposed scheme is appropriate for delay insensitive applications. We consider the minimization of the average transmit bit energy (/spl Theta/) subject to maintaining individual target E/sub b//I/sub 0/ for each user. Two algorithms, one directly minimizing /spl Theta/ and the other indirectly using measured pilot power, are given. Both algorithms select the optimal cell-site if forward and reverse link gains are equal; however, the latter is decentralized and uses only local measurements and amenable for practical implementation. Simulation results show that a 20% reduction in transmit bit energy can be achieved on average using our schemes over the scheme with no rate control.