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).