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Distributed Systems

Power allocation in wireless multi-user relay networks

Profile image of Khoa PhanKhoa Phan

2009, … IEEE Transactions on

https://doi.org/10.1109/TWC.2009.080485
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11 pages

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Abstract

In this paper, we consider an amplify-and-forward wireless relay system where multiple source nodes communicate with their corresponding destination nodes with the help of relay nodes. Conventionally, each relay equally distributes the available resources to its relayed sources. This approach is clearly sub-optimal since each user 1 experiences dissimilar channel conditions, and thus, demands different amount of allocated resources to meet its quality-of-service (QoS) request. Therefore, this paper presents novel power allocation schemes to i) maximize the minimum signal-to-noise ratio among all users; ii) minimize the maximum transmit power over all sources; iii) maximize the network throughput. Moreover, due to limited power, it may be impossible to satisfy the QoS requirement for every user. Consequently, an admission control algorithm should first be carried out to maximize the number of users possibly served. Then, optimal power allocation is performed. Although the joint optimal admission control and power allocation problem is combinatorially hard, we develop an effective heuristic algorithm with significantly reduced complexity. Even though theoretically sub-optimal, it performs remarkably well. The proposed power allocation problems are formulated using geometric programming (GP), a well-studied class of nonlinear and nonconvex optimization. Since a GP problem is readily transformed into an equivalent convex optimization problem, optimal solution can be obtained efficiently. Numerical results demonstrate the effectiveness of our proposed approach.

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Optimal Relay Assignment and Power Allocation for Cooperative Communications
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Joint Bandwidth and Power Allocation with Admission Control in Wireless Multi-User Networks With and Without Relaying
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Equal allocation of bandwidth and/or power may not be efficient for wireless multi-user networks with limited bandwidth and power resources. Joint bandwidth and power allocation strategies for wireless multi-user networks with and without relaying are proposed in this paper for (i) the maximization of the sum capacity of all users; (ii) the maximization of the worst user capacity; and (iii) the minimization of the total power consumption of all users. It is shown that the proposed allocation problems are convex and, therefore, can be solved efficiently. Moreover, the admission control based joint bandwidth and power allocation is considered. A suboptimal greedy search algorithm is developed to solve the admission control problem efficiently. The conditions under which the greedy search is optimal are derived and shown to be mild. The performance improvements offered by the proposed joint bandwidth and power allocation are demonstrated by simulations. The advantages of the suboptimal...

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References (24)

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1 In this paper, we consider an amplify-and-forward (AF) wireless relay system where multiple source nodes communicate with their corresponding destination nodes with the help of relay nodes. While each user 2 is assisted by one relay, one relay can assist many users. Conventionally, each relay node is assumed to equally distribute the available bandwidth and power resources to all sources for which it helps to relay information. Realizing the sub-optimality of this approach, in this paper, we present efficient power allocation schemes to i) maximize the minimum end-to-end signal-to-noise ratio among all users; ii) minimize the total transmit power over all sources; iii) maximize the system throughput. Our approach is based on geometric programming (GP), a well-studied class of nonlinear and nonconvex optimization. Since a GP problem is readily transformed into an equivalent convex optimization problem, optimal power allocation can be obtained efficiently. Numerical results demonstrate the effectiveness of our proposed approach.

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This article studies optimal power allocation schemes in a multi-relay cooperating network employing amplify-andforward (AF) protocol with multiple source-destination pairs. It is assumed that full channel state information is available at the relays. As such, distributed beamforming is employed in forwarding signals to the destinations. In this context, the authors extend recent works on distributed beamforming for a single source-destination pair to the scenario where multiple source-destination pairs are competing for the power resource at the relays. Under orthogonal transmissions of each sourcedestination pair, considered are the two following power allocation problems: (i) minimise the sum relay power with guaranteed quality of service (QoS) in terms of signal-to-noise ratio (SNR) at the destinations, and (ii) jointly maximise the SNR margin at the destinations subject to individual power constraints at the relays. Although these optimisation problems can be formulated as second-order conic programs (SOCP), the main contribution of this work are proposals of simple and fast converging numerical algorithms, based on the fixed point iteration framework, to efficiently solve these two problems.

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Related topics

  • Distributed Computing
  • Convex Optimization
  • Cellular Networks
  • Amplify and Forward
  • Power allocation
  • Information Rate
  • Admission Control
  • Electrical and Electronic Engine...
  • Relay Network
  • Nonconvex optimization
  • Heuristic algorithm

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