Convexity of some feasible QoS regions and asymptotic behavior of the minimum total power in CDMA systems

Dynamic power control and scheduling strategies provide efficient mechanisms for improving the performance of large wireless networks. In order to maximize throughput or minimize the total power consumption while satisfying different quality-of-service (QoS) requirements of the users, strategies must developed to optimally utilize scarce resources in such networks. This means that in each time slot, the network must be operated close to the boundary of the feasibility region, which is defined as a set of all QoS requirements that can be supported by the network. Consequently, when optimizing scheduling algorithms, a system designer is confronted with some fundamental problems. One of the main problems is that of the convexity of the feasibility region since this problem strongly influences the design of optimal strategies. Other problems are how the change of QoS requirements affects the total power consumption and what the optimal tradeoff between the QoS requirements is. In this paper, we address these problems and solve them completely in some important cases. The purpose of this paper is to explore the interrelationship between the QoS requirements and some basic parameters such as the power consumption. Although the results are obtained in the context of a power-controlled CDMA-based system, they apply to some other communication systems. A key assumption is that there is a monotonous relationship between a QoS parameter of interest and the signal-tointerferenceratio at the output of a linear receiver.