F. de S. Chaves

Transmission Power Control for Opportunistic QoS Provision in Wireless Networks

This paper proposes an automatic control framework to address the problem of distributed and opportunistic transmission power control in wireless communication networks. The proposed framework allows high flexibility on the quality of service (QoS) provision by exploiting the link quality variation. It associates a standard target tracking algorithm with a dynamic target QoS determined by a linear quadratic regulator (LQR) controller that induces an opportunistic behavior. Strict QoS requirements can also be fulfilled by choosing appropriately the weighting parameters of the LQR synthesis. To prevent performance degradation due to measurement uncertainties, robust solutions are developed. The proposed mixed <i>H</i>₂/<i>H</i>_∞ distributed power control combines the optimal <i>H</i>₂ control and the robust <i>H</i>_∞ control to obtain trade-off solutions. All developed algorithms present low computational complexity, and the mixed <i>H</i>₂/<i>H</i>_∞ distributed power control can operate as the pure <i>H</i>₂ control if the robust constraint is relaxed according to the choice of a single parameter. The performance of proposed algorithms is assessed through computer simulations.

Opportunistic distributed power control with QOS guarantee in wireless communication systems

The decentralized power control problem in a generic wireless communication system can be seen as a competition between the communication nodes. In this paper, we formulate a new framework to the problem with the application of noncooperative game theory and opportunistic resource allocation concepts, where the satisfaction of Quality of Service (QoS) requirements is considered. Analytical and simulation results indicate the good performance of the proposed algorithm in terms of convergence, QoS satisfaction and energy efficiency.

Self-adaptive distributed power control for opportunistic QOS provision in wireless communication networks

Emerging wireless communication networks are required to provide data services which tolerate large variations of link quality. Such applications allow flexible power control procedures. In this paper, we approach the distributed power control problem from an automatic control point of view. A new framework for opportunistic power control is proposed, where the target quality of service at each link is determined by a linear quadratic regulator controller according to a given self-adaptive criterion. Stability and convergence of proposed framework are analytically guaranteed, while its performance is confronted with other algorithms through computer simulations.

Performance evaluation of access selection algorithms for VoIP on wireless multi-access networks

The tendency of wireless communication systems beyond 3G is the wireless multi-access (MA) environment, which is characterized by the integration of different radio access networks (RANs). Parallel to the wireless network evolution, Voice over Internet Protocol (VoIP) is one of the fastest growing Internet real-time applications. Implementation of VoIP over a multi-access network requires the incorporation of efficient resource allocation strategies, namely, common radio resource management (CRRM), in order to meet the optimum combined network performance. In this paper, we propose access selection (AS) algorithms for MA networks and evaluate their performance for VoIP service. Conventional AS algorithms are taken as reference.

Conception and evaluation of access selection algorithms for cooperative beyond 3G systems

As wireless technology evolve, we are seeing a tendency toward cooperative composite networks in which the diversity user demands can be properly met. The radio resource management (RRM) in such a network paradigm is a fascinating field of study and finding a cost-effective RRM solution is one of the greatest challenge faced by scientists today. This paper proposes an investigation of the access selection (AS) algorithms for the multi-access networks, aiming to indicate possible solutions based on actual radio resource consumptions and requirements. We assume that different radio access networks (RANs) are run by a single operator or a set of cooperative operators for which a proper inter-RAN signaling architecture is installed.

Distributed power control for QoS-flexible services in wireless communication networks

This paper proposes a distributed power control framework for wireless communication networks that is able to provide a flexible QoS with the introduction of a dynamic target QoS into a conventional (fixed) target tracking power control algorithm. The target QoS of individual terminals is automatically updated according to a given performance criterion. The distributed power control is formulated as a Linear Quadratic Regulator (LQR) problem, where system operating points are met according to channel quality and the choice of key parameters. Effectiveness of the LQR-based power control is analyzed and the influence of such parameters on the algorithms performance is investigated with the help of computer experiments.

Energy efficiency improved game-theoretic distributed power control algorithm for best effort services in wireless communications systems

Wireless communications systems have transmitter power control as an essential tool for managing radio resources. Decentralized power control is of special interest and may be characterized as a competition among the communication nodes. This indicates the adequacy of the application of noncooperative game theory concepts to the problem. In this work, we formulate a general framework to the distributed power control problem, derive a power control algorithm and use a simple prediction method to improve its performance.

Performance evaluation of adaptive H8 space-time equalizers for wireless communication systems with asynchronous interference

Packet-switched multi-access communication systems may have difficulties on detecting a user signal due to a momentary interference, which is caused by packet transmissions of a co-channel interferer user. Asynchronous co-channel interference impacts directly the performance of the reception process, specially in the uplink (mobile to base station transmission). In this work, the Hinfin filter is configured as an adaptive space-time equalizer and its performance is compared to that of the RLS- based space-time equalizer, in the presence of asynchronous interference. Computational simulations are performed for single- input multiple-output (SIMO) channels with spatial diversity.

Impact of intelligent access selection algorithms in cooperative wireless networks

Future generation of wireless networks will solicit the cooperation of heterogeneous Radio Access Networks (RANs) in order to provide multimedia traffic to different classes of users with varying Quality of Service (QoS) requirements over regions and time zones. The use of such RANs as subsystems of a larger wireless network, i.e, a multi-access network, claims for an Access Selection (AS) scheme to coordinate the load sharing so as to meet the optimum combined network performance. Depending on the individual subsystem capacities, the traffic load conditions and the subsystem channel quality, an intelligent AS algorithm can provide capacities beyond the sum of the subsystems capacities. This paper addresses the issue of the AS in the context of multi-access networks. We intend to provide an analytical formulation which indicates the suitable/unsuitable scenarios for employment of an intelligent AS strategy. The usability of the proposed qualitative studies are demonstrated by means of simulations.

performance of energy efficient game theoretical-based power control algorithm in a discrete power environment

Transmitter power control is an essential tool for managing the interference in a system constituted by a set of communications nodes. In the absence of a central controller, the decentralized power control is of special interest and may be characterized as a competition among the communication nodes. This indicates the adequacy of the application of noncooperative game theory concepts to the problem. The continuous domain for transmit power is usually assumed, although, in practice, digitally power controlled systems work with discrete power levels. In this work we evaluate the performance of a distributed power control algorithm which is derived from the formulation of the power control problem as a static multi-stage nonzero- sum noncooperative game. Continuous and discrete domains for transmit power are considered.