IEEE 802.16J Relay- based wireless access networks: An overview.

Multihop wireless systems have the potential to offer improved coverage and capacity over single-hop radio access systems. Standards development organizations are considering how to incorporate such techniques into new standards. One such initiative is the IEEE 802.16j standardization activity, adding relay capabilities to IEEE 802.16 systems. This article provides an overview of this relay-based technology, focusing on some of the most pertinent aspects. In particular, the different modes of operation (transparent and non-transparent), framing structures, and network entry procedures are described. Some consideration of the issues in designing such systems is then given, which highlights when different features within the standard are most appropriate. As these systems are very new, many open issues remain to be resolved.European Community´s Seventh Framework ProgramPublicad

Network Planning for IEEE 802.16j Relay Networks

In this chapter, a problem formulation for determining the optimal node location for base stations (BSs) and relay stations (RSs) in relay-based 802.16 networks is developed. A number of techniques are proposed to solve the resulting integer programming (IP) problem—these are compared in terms of the time taken to find a solution and the quality of the solution obtained. Finally, there is some analysis of the impact of the ratio of BS/RS costs on the solutions obtained. Three techniques are studied to solve the IP problem: (1) a standard branch and bound mechanism, (2) an approach in which state space reduction techniques are applied in advance of the branch and bound algorithm, and (3) a clustering approach in which the problem is divided into a number of subproblems which are solved separately, followed by a final overall optimization step. These different approaches were used to solve the problem. The results show that the more basic approach can be used to solve problems for small metropolitan areas; the state space reduction technique reduces the time taken to find a solution by about 50 percent. Finally, the clustering approach can be used to find solutions of approximately equivalent quality in about 30 percent of the time required in the first case. After scalability tests were performed, some rudimentary experiments were performed in which the ratio of BS/RS cost was varied. The initial results show that for the scenarios studied, reducing the RS costs results in more RSs in the solution, while also decreasing the power required to communicate from the mobile device to its closest infrastructure node (BS or RS)

An Interference-Aware Analytical Model for Performance Analysis of Transparent Mode 802.16j Systems

Abstract — In this paper, an interference-aware analytical model of IEEE 802.16j systems operating in transparent mode is described. The model can be used to determine the throughput gain that can be achieved by 802.16j relay- based systems under a max-min fairness constraint in which the difference between the data rate delivered to all subscribers is minimized. Two variants of the model are considered – one in which there is no spatial reuse and one in which there is spatial reuse. The study finds that this variant of 802.16j system can deliver significant gains over traditional single-hop access systems: 40 % in the case in which there is no spatial reuse and up to 80 % when spatial reuse is realised. Index Terms — IEEE 802.16j, optimisation problem, performance gain, transparent multihop relay. I

Analysis of transparent mode IEEE 802.16j system performance with varying numbers of relays and associated transmit power

Abstract — In this paper, the system capacity of IEEE 802.16j systems operating in transparent mode is investigated under varying numbers of relays and associated transmit power. The study is based on an extended variant of an analytical model defined in previous work and used to determine the throughput gain that can be achieved under a max-min fairness constraint. The study finds that significant overall throughput gains can be achieved over 802.16e systems: 125 % and 55 % gain with and without spatial reuse, respectively. However, the overall throughput gain drops as the transmit power at the relays (RSs) decreases despite the fact that a greater number of concurrent transmissions can be achieved due to less interference among the RSs ’ transmissions. Decreasing the transmit power at the RSs eventually leads to a significant reduction of the achievable throughput gain even though a large number of RSs are deployed in scenarios with or without spatial reuse