Abstract
Cooperative relaying is an important feature for the fourth generation wireless system to upgrade system performance. Mobile relays can offer better results than fixed relays without any additional infrastructure cost. However, efficient cooperation decision as well as resource allocation are critical to satisfy model constraints as required quality of service (QoS). In this work, simple mobile users with advantageous channels can act as potential relays for cell edge users for an uplink transmission. They multiplex, in the frequency domain, their own data to that of the relayed sources, with the objective for both relay and sources to reach a target data rate. An optimal joint resource blocks (RB) allocation and power allocation scheme under a required data rate constraint per user is proposed. The optimization problem is formulated to minimize the total system power. Dual decomposition and subgradient method are used to solve the optimization problem after dividing it into independent subproblems with less complexity to find the optimal solution. The cooperation decision and the sources-relays association is either performed as a first step of resource allocation, or jointly optimized with RB and power allocation. Simulation results show that these proposed algorithms both reduce system’s power consumption while ensuring the required QoS. Joint optimization of relay selection, RB and power allocation provides a higher power consumption decrease, but requires higher complexity and overhead.
Highlights
Replying to quality of service requirement with always greedy data application is still an important challenge for wireless cellular networks
Compared to previous published results, our system model considers mobile relays that have to multiplex their own data to the relayed data, so that the relay as well as the relayed sources all achieve the same target data rate
Two strategies have been proposed for relay selection: it is either performed as an initialization phase by the Base Station (BS), based on average channel gains, or it is jointly optimized with resource blocks (RB) and power allocation
Summary
Replying to quality of service requirement with always greedy data application is still an important challenge for wireless cellular networks. In [16], resource allocation considering an uplink relaying system with one destination, several sources, and several fixed relays are studied to maximize system throughput using AF and DF schemes with a minimum data rate constraint per user. In [17], joint power allocation, relay selection, and subcarrier assignment with a minimal data rate per user is discussed for a downlink system model with fixed relays. 1.2 Contributions In this work, we propose a new resource allocation algorithm for an uplink multiuser OFDMA relay network in the context of green communications where we aim to save battery life by minimizing the consumed transmit power. Two different strategies are studied regarding relay selection: it is either performed before resource allocation, depending on average channel gains In this case, relayed sources are cell edge users, and a relayed source chooses only one relay. Algorithm 1 Proposed Sub-Optimal algorithm for Resource Block and Power Allocation (Problem (3))
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