Power Control, Capacity, and Duality of Uplink and Downlink in Cellular CDMA Systems

Abstract

Abstract-Accurate power control is an essential requirement in the design of cellular code-division multiple-access (CDMA) systems. In this paper, we contribute three main themes to the power control problem. First, we derive an efficient algorithm for computing minimal power levels for large-scale networks within seconds. Nice and intuitive conditions for the existence of feasible power solutions follow from this approach. Second, we define the capacity region of a network by the set of effective spreading gains, or data rates, respectively, which can be supplied by the network. This is achieved by bounding the spectral radius of a certain matrix containing system parameters and mutual transmission gain information. It is shown that the capacity region is a convex set. Finally, we reveal an interesting duality between the uplink and downlink capacity region. In a clear-cut analytical way, it substantiates the fact that the uplink is the more restricting factor in cellular radio networks. The same methods carry over to certain models of soft handover. In the case that the channel gains are subject to log-normal shadowing, we introduce the concept of level-capacity regions. Despite the complicated structure, it can still be shown that this set is sandwiched by two convex sets coming arbitrarily close as variance decreases.Index Terms-Capacity region, cellular networks, code-division multiple access (CDMA), convexity, log-normal fading, soft handover.

Border Games in Cellular Networks

“…Baccelli et al [2] consider downlink power allocation and admission control in CDMA networks relying on stochastic geometry. Hanly and Tse [11] as well as Catrein et al [3] consider power control and capacity in CDMA networks. There is a very little literature about pilot power optimization, though [17], [30].…”

“…We first assume that one of the operators does not play and show that the other operator has an incentive to be strategic. Second, we consider the case in which both operators have the possibility to adjust their pilot power and show that they are better off by doing so 3 .…”

Optimal QoS tradeoff and power control in CDMA systems

“…Dynamic allocation of power is a popular strategy to combat detrimental effects of multipath fading [6]. This paper generalizes some of the results of [5] and [7] and also extends them to channels whose inputs are subject to power constraints. In communication networks like the uplink channel, there are individual power constraints on each user rather than the total power constraint.…”

“…Any such a power allocation (whether subject to (5) or not) is called a valid power allocation [12]. If a valid power allocation exists, we say that q :…”

“…The problem of power control has received much attention in recent years (see [4] and [5] for references). Power control is a central mechanism for resource allocation and interference management in wireless systems.…”