Relay Station Placement in IEEE 802.16j Dual-Relay MMR Networks

Cooperative relaying is one of the most effective techniques in coverage extension and capacity enhancement by virtue of spatial diversity. To fully explore the benefits of adopting relay stations (RSs), a vital issue is the placement of RSs by jointly considering an advanced coding scheme. In this paper, we aim to provide a general framework for solving the minimum cost RS placement problem in 802.16J Mobile Multi-hop Relay (MMR) networks. We first introduce a novel dual-relay architecture, where all the users, i.e., the mobile stations (MSs) and the fixed subscriber stations (SSs), are connected to the BS via two active RSs through decoded-and-forwarding scheme. We will then demonstrate that the most significant advantages of the dual-relay architecture lie in the ability of achieving high throughput for the systems. In addition, the users can be subject to better fault tolerance, robustness, and power saving. We formulate the dual- relay RS placement problem, and solve it through a two-phase algorithm to deal with the NP-hardness. Numerical analysis is conducted to evaluate the performance gain due to cooperative RS placement in the proposed framework, and demonstrate that the proposed approach can lead to a well acceptable solution compared with that by exhaustively searching.