Distributed Power Control Scheme Research Articles

Pareto-Efficient and Goal-Driven Power Control in Wireless Networks: A Game-Theoretic Approach With a Novel Pricing Scheme

A Pareto-efficient, goal-driven, and distributed power control scheme for wireless networks is presented. We use a non-cooperative game-theoretic approach to propose a novel pricing scheme that is linearly proportional to the signal-to-interference ratio (SIR) and analytically show that with a proper choice of prices (proportionality constants), the outcome of the noncooperative power control game is a unique and Pareto-efficient Nash equilibrium (NE). This can be utilized for constrained-power control to satisfy specific goals (such as fairness, aggregate throughput optimization, or trading off between these two goals). For each one of the above goals, the dynamic price for each user is also analytically obtained. In a centralized (base station) price setting, users should inform the base station of their path gains and their maximum transmit-powers. In a distributed price setting, for each goal, an algorithm for users to update their transmit-powers is also presented that converges to a unique fixed-point in which the corresponding goal is satisfied. Simulation results confirm our analytical developments.

Hybrid power control scheme in hierarchical spectrum sharing network for cognitive radio

Recently, Hierarchical Spectrum Sharing Network (HSSN) has been proposed to efficiently and flexibly unitize available spectrum resource in cognitive radio context. In the HSSN, available spectrum bands are classified into two types to support both centralized and distributed communications simultaneously. A stable and efficient power control scheme is required to fully make use of the potential of HSSN. An effective power control scheme in the HSSN faces several challenges, such as low power emission, high level of quality of service (QoS), and suitability for the hybrid architecture of the HSSN. To effectively meet these requirements, a novel hybrid power control scheme is proposed in this paper. The proposed scheme is composed of three parts: a centralized power control scheme, a distributed power control scheme, and a coordination policy to coordinate these two types of power control schemes when both of them are exploited in the same channels. In the centralized power control design, we propose a Two-Step Fair Allocation (TSFA) scheme. In its first step, resources, such as channels and powers, are allocated by cognitive radio base station (CRBS) based on fairness and QoS requirements to obtain the maximum available resources of cognitive radio users (CRUs). In the second step, to get the final resource and reduce algorithm complexity, the allocation task is accomplished by each CRU simultaneously. In the distributed power control design, we propose Utility based Power Control algorithm combined with Admission Control (UPCAC). We also provide a protocol to effectively implement UPCAC. We formulate a utility function, i.e., payoff function minus price function, to measure the requirements of primary users (PUs) and CRUs. The payoff function represents CRUs’ signal-to-interference-plus-noise ratio (SINR) objectives, and the price function specifies protection for PUs and CRUs’ power consumptions. By analyzing the geometric characteristics of the payoff and price functions, we properly set the parameters of the utility function. Further, we propose coordination policy to combine centralized power control scheme with distributed power control scheme when they are exploited in the same channels. Simulation results show that the proposed hybrid power control scheme can meet the requirements of low emission power as well as high QoS level.

Distributed Correlative Power Control Schemes for MobileAd hocNetworks Using Directional Antennas

Medium access control (MAC) protocols simultaneously integrating transmission power (TP) control with directional antennas have the potential to enhance both energy savings and capacity throughput in wireless multihop Mobile Ad hoc NETworks (MANETs). In this paper, we present a model to calculate future interference in networks with directional antennas, and based on this model, we derive some relations that should exist between the required TP of RTS, CTS, DATA, and ACK frames for successful data packet delivery in MANETs based on the directional version of the IEEE 802.11 distributed coordination function. From these relations, we propose a distributed power control scheme. Furthermore, we show, via simulations, that the true potentials from the proposed control scheme cannot be shown due to the imperfection of the derived model. Based on these observations, we introduce another class of power control algorithm that instead deploys a prediction filter (Kalman or extended Kalman) to estimate future interference. Simulation experiments for different topologies are used to verify the significant throughput and energy gains that can be obtained by the proposed power control schemes.

Game theory and power control in ultrawideband networks

This paper describes a theoretical framework for the design and analysis of power control algorithms for high-throughput wireless networks using ultrawideband (UWB) technologies. The tools of game theory are shown to be expedient for deriving scalable, energy-efficient, distributed power control schemes to be applied to a population of battery-operated user terminals in a rich multipath environment. In particular, the power control issue is modeled as a dynamic noncooperative game in which each user chooses its transmit power so as to maximize its own utility, which is defined as the ratio of throughput to transmit power. Although distributed (noncooperative) control is known to be suboptimal with respect to the optimal centralized (cooperative) solution, it is shown via large-system analysis that the game-theoretic distributed algorithm based on Nash equilibrium exhibits negligible performance degradation with respect to the centralized socially optimal configuration. The framework described here is general enough to also encompass the analysis of code division multiple access (CDMA) systems and to show that UWB slightly outperforms CDMA in terms of achieved utility at the Nash equilibrium.

A Distributed Channel Access Protocol for Ad Hoc Networks with Feedback Power Control

Distributed power control schemes are extensively employed in the cellular networks and are capable of improving the capacity of the network. However, the power control schemes from the cellular networks suffer from performance degradation due to self and direct-interference and hidden-terminal problems when directly employed in ad hoc networks. Most of the existing channel reservation-based power control protocols for ad hoc networks employ incremental power allocation rather than global allocation of the power to the incoming links; thus, they may not effectively utilize the spatial frequency reuse in the network. This paper presents a distributed channel access protocol that couples the channel reservation and the iterative/global transmission power control schemes in ad hoc networks. The designed protocol considers the convergence problem of the global power control in ad hoc networks. The designed access criteria employ the local admission control based on the sufficient criteria for admissibility and global power control for balancing the SIR (signal to interference ratio) of the links. In the performance evaluation study of the designed protocol, an almost twofold increase in the throughput and capacity is observed compared to the existing power-controlled protocol for ad hoc networks.

Distributed interference compensation for wireless networks

We consider a distributed power control scheme for wireless ad hoc networks, in which each user announces a price that reflects compensation paid by other users for their interference. We present an asynchronous distributed algorithm for updating power levels and prices. By relating this algorithm to myopic best response updates in a fictitious game, we are able to characterize convergence using supermodular game theory. Extensions of this algorithm to a multichannel network are also presented, in which users can allocate their power across multiple frequency bands.

Distributed power control for cellular networks in the presence of channel uncertainties

In this paper, a novel distributed power control (DPC) scheme for cellular network in the presence of radio channel uncertainties such as path loss, shadowing, and Rayleigh fading is presented. Since these uncertainties can attenuate the received signal strength and can cause variations in the received signal-to-interference ratio (SIR), a new DPC scheme, which can estimate the slowly varying channel uncertainty, is proposed so that a target SIR at the receiver can be maintained. Further, the standard assumption of a constant interference during a link's power update used in other works in the literature is relaxed. A CDMA-based cellular network environment has been developed to compare the proposed scheme with earlier approaches. The results show that our DPC scheme can converge faster than others by adapting to the channel variations. In the presence of channel uncertainties, our DPC scheme renders lower outage probability while consuming significantly low power per active mobile user compared with other schemes that are available in the literature.

Open-loop power control performance in DS-CDMA networks with frequency selective fading and non-stationary base stations

In this paper, we study the performance of a simple and easy-to-implement distributed power control strategy applicable to direct sequence code division multiple access (DS-CDMA) networks. The scheme makes use of the received power measurements made on the forward link at individual mobile units to control the transmit powers on their reverse links. The algorithm, which effectively compensates for the slowly varying distance and shadow losses (due to their high correlation on both forward and reverse links), attempts to minimize the effect of fast multipath fading by averaging it out. We adopt a quasi-analytic approach to estimate the reverse link capacity performance of an open-loop power control scheme in both a single cell and a multi-cell environment, and we do this for both a fixed base station and a moving base station scenario. Non-stationary base stations are typical in tactical and emergency communications scenarios where the base stations could be mounted on moving platforms (e.g., tanks, jeeps, unmanned airborne vehicles). We estimate the capacity degradation, when base stations move relative to other cells, as a function of the amount of cell overlap and the standard deviation of the power control error. We also provide a comparison of the performance of the open-loop power control strategy with that of a closed-loop power control strategy.

Efficient distributed power control for cellular mobile systems

Various distributed carrier-to-interference (C/I) balancing procedures have been developed to cope with implementational drawbacks of centralized power-control schemes. However, it would be inevitable for these distributed schemes to lose some system performance compared to a centralized one since they control their power level based on only the local C/I measurements. An efficient distributed power-control (DPC) scheme is proposed to maximize the system performance. A distributed C/I balancing algorithm is suggested, which converges fast and is robust to C/I estimation errors. A simple instability detection rule is also suggested to accelerate the balancing phase of DPC schemes. Numerical results indicate that our algorithm achieves improvements in terms of the outage probability as well as the algorithm speed. Robustness to the C/I measurement errors is also explored.