Power allocation in wireless multi-user relay networks

Abstract

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.

Performance Analysis of Distributed Spatial Multiplexing with Multi-hop Amplify and Forward Relaying in Cellular Networks

“…However, most existing work focuses on relay selection in a centralized fashion. There is already a lot of works related to cluster formation [4], [7], capacity improvement [9] and energy efficient cooperative communication [3], [10], but little attention has been given to cooperative relay selection on the basis of their location in clusters to improve the energy efficiency and reliability.…”

Adaptive Power Allocation for Bidirectional Amplify-and-Forward Multiple-Relay Multiple-User Networks

“…Being the simplest and easiest form of relaying, power allocation for AaF protocol has been extensively studied in unidirectional relay networks [4], [6], [7], [10], [11]. Power allocation based on both signal-to-noise ratio (SNR) maximization and outage probability minimization is considered in [10], and that for symbol error rate (SER) minimization is considered [4] for a single-relay network under Rayleigh fading.…”

Joint bandwidth and power allocation in wireless multi-user decode-and-forward relay networks

“…Power allocation aiming at optimizing the sum capacity of multiple users for four different relay transmission strategies has been studied in [31], while an AF based strategy in which multiple sources share multiple relays using power control has been developed in [32], [33].…”

“…System throughput maximization and the worst user throughput maximization are studied using convex optimization in [15]. Sum capacity maximization is taken as an objective for power allocation in [31], while max-min SNR, power minimization, and throughput maximization are used as power allocation criteria in [32].…”