Power control for multicell CDMA wireless networks: A team optimization approach (original) (raw)

A passivity approach to game-theoretic CDMA power control

Automatica, 2006

This paper follows a game-theoretical formulation of the CDMA power control problem and develops new decentralized control algorithms that globally stabilize the desired Nash equilibrium. The novel approach is to exploit the passivity properties of the feedback loop comprising the mobiles and the base station. We first reveal an inherent passivity property in an existing gradient-type algorithm, and prove stability from the Passivity Theorem. We then exploit this passivity property to develop two new designs. In the first design, we extend the base station algorithm with Zames-Falb multipliers which preserve its passivity properties. In the second design, we broaden the mobile power update laws with more general, dynamic, passive controllers. These new designs may be exploited to enhance robustness and performance, as illustrated with a realistic simulation study. We then proceed to show robustness of these algorithms against time-varying channel gains. ᭧

Power Control in Wireless Cellular Networks

Transmit power in wireless cellular networks is a key degree of freedom in the management of interference, energy, and connectivity. Power control in both uplink and downlink of a cellular network has been extensively studied, especially over the last 15 years, and some of the results have enabled the continuous evolution and significant impact of the digital cellular technology.

Decentralized dynamic nonlinear controllers to minimize transmit power in cellular networks, Part I

2010

We consider the problem of synthesizing decentralized transmit power control for finite-gain stable cellular code division multiple access (CDMA) networks subject to saturation constraints on the mobile transmit powers. We show that the passivity theorem and an extension of the Zames-Falb multipliers can be used to synthesize the required distributed decentralized nonlinear dynamic controllers, to be implemented at the base station and at the mobile users, including a multi-input-multi-output (MIMO) anti-windup controller that can be implemented on the mobile hand-sets.

Optimal linear and bilinear algorithms for power control in 3G wireless CDMA networks

European Transactions on Telecommunications, 2007

In this paper we present two power control algorithms that potentially can be used as efficient techniques for power updates in 3G wireless CDMA communication networks. The algorithms are obtained by optimising the signal-to-interference-ratio (SIR) error. The control laws are distributed, respectively linear and bilinear, and either requires estimation of the channel interference (or the quantity inversely proportional to the signal interference, known as the channel variation) or the development of efficient numerical algorithms for solving a set of obtained algebraic equations. Simulation results show superiority of the proposed algorithm over the distributed constrained power control (DCPC) algorithm.

Optimal power control in CDMA mobile networks

Code Division Multiple Access (CDMA) is interference limited multiple access system. Because all users transmit on the same frequency, internal interference generated by the system is the most significant factor in determining system capacity and call quality. The transmit power for each user must be reduced to limit interference, however, the power should be enough to maintain the required signal energy per bit to noise power spectral density ratio (Eb/No) for a satisfactory call quality. Maximum capacity is achieved when Eb/No of every user is at the minimum level needed for the acceptable channel performance. As the mobile station (MS) moves around, the radio frequency (RF) environment continuously changes due to fast and slow fading, external interference, shadowing, and other factors. The aim of the dynamic power control is to limit transmitted power on both the links while maintaining link quality under all conditions. Additional advantages are longer mobile battery life and l...

Multiobjective Distributed Power Control Algorithm for CDMA Wireless Communication Systems

Vehicular Technology, IEEE …, 2007

Although power control has been explored since the early 1990s, there still remains the need for further research. Most of the algorithms so far consider either the problem of minimizing the sum of transmitted power under quality of service (QoS) constraints given in terms of minimum signal-to-interference-plusnoise ratio (SINR) in a static channel or the problem of mitigating fast fading in a single dynamic link. In this paper, we suggest a new approach to the power control by treating the QoS requirement as another objective for the power control and a fully distributed method for solving the multiobjective power optimization problem. The obtained solution is parameterized so that a tradeoff can be made between power consumption and QoS. In the limit case, when only QoS is weighted, the algorithm reduces to the well-known distributed power control algorithm (IEEE Trans. Commun., vol. 42, no. 2/3/4, pt. 1, Feb./Mar./Apr. 1994). In the other limit, the algorithm reduces to transmission with fixed minimum power. The convergence properties of the proposed algorithm are studied both theoretically and with numerical simulations. Although we only consider SINR and power sum, our algorithm could be easily modified to take other objectives, such as throughput, into account.

Loss of continuity in cellular networks under stabilizing transmit power control

2009 47th Annual Allerton Conference on Communication, Control, and Computing (Allerton), 2009

Recently, passivity-based techniques to control the transmit power of mobile nodes have been proposed to ensure the finite gain stability of a class of cellular CDMA networks. These techniques implement the Zames-Falb multipliers at the mobile node and at the base stations. The finite gain stability of such a cellular network follows as a consequence of the fact that the Zames-Falb multipliers preserve positivity of monotone memoryless nonlinearities. In this note, we show that such a cellular network may not be a continuous system. Hence, the following undesirable scenarios may occur if the set-point is varied with time: (i) the Nash equilibrium may cease to exist, and (ii) vanishingly small changes in set-points (such as the target SINR values) may cause the system trajectory to jump from one equilibrium point to another, leading to nonvanishingly small variations in the mobile transmit powers and the actual SINR values across such networks.

A Distributed Dynamic Target-SIR-Tracking Power Control Algorithm for Wireless Cellular Networks

IEEE Transactions on Vehicular Technology, 2000

The well-known fixed-target-signal-to-interferenceratio (SIR)-tracking power control (TPC) algorithm provides all users with their given feasible fixed target SIRs but cannot improve the system throughput, even if additional resources are available. The opportunistic power control (OPC) algorithm significantly improves the system throughput but cannot guarantee the minimum acceptable SIR for all users (unfairness). To optimize the system throughput subject to a given lower bound for the users' SIRs, we present a distributed dynamic target-SIR tracking power control algorithm (DTPC) for wireless cellular networks by using TPC and OPC in a selective manner. In the proposed DTPC, when the effective interference (the ratio of the received interference to the path gain) is less than a given threshold for a given user, that user opportunistically sets its target SIR (which is a decreasing function of the effective interference) to a value higher than its minimum acceptable target SIR; otherwise, it keeps its target SIR fixed at its minimum acceptable level. We show that the proposed algorithm converges to a unique fixed point starting from any initial transmit power level in both synchronous and asynchronous power-updating cases. We also show that our proposed algorithm not only guarantees the (feasible) minimum acceptable target SIRs for all users (in contrast to the OPC) but also significantly improves the system throughput, compared with the TPC. Furthermore, we demonstrate that DTPC, along with TPC and OPC, can be utilized to apply different priorities of transmission and service requirements among users. Finally, when users are selfish, we provide a game-theoretic analysis of our DTPC algorithm via a noncooperative power control game with a new pricing function.