In this paper, we investigate a communication relay placement problem to optimize the network throughput in a content-centric wireless mesh networks (WMN), in which the WMN is enhanced by including a small set of communication relays and a subset of wireless mesh routers serving as storage nodes. Specifically, we first define the communication relay placement problem in content-centric WMNs. We then model the problem as a mathematical programming and propose a linear programming approach for calculating the achievable network throughput when the positions of communication relays are fixed. Next, to optimally placing the communication relays, we formulate an integer linear programming problem and we develop an efficient near-optimal approximation algorithm based on linear programming relaxation. Finally, extensive simulation experiments have been conducted, and the results demonstrate the effectiveness of the proposed algorithms.
AN EFFICIENT RELAY PLACEMENT ALGORITHM FOR CONTENT-CENTRIC WMNS
263For the peer-to-peer traffic, it has been shown that the maximal throughput in large-scale two- 11,12], where W is the wireless channel capacity and n is the number of nodes in the network. Intuitively, such a capacity is because of the fact that the dominating traffic (in the scale of ‚.n/) has to be routed, via multihop paths, through a certain subset of mesh routers (in the scale of ‚. p n//. In other words, the subset of mesh routers is the bottleneck of the whole WMN.For the Internet access scenario, which is the most common one today, all traffic has to pass through a limited number of Internet gateways. Consequently, the network capacity is limited by the wireless channels of the gateways. For instance, if there is only one gateway, then the capacity of a large-scale two-dimensional WMN is ‚ W n [13]. To improve the performance of WMN, in this paper we consider a content-centric WMN design, in which the WMN is enhanced by including a small set of communication relays and a subset of wireless mesh routers serving as storage nodes.In the past, relays or local gateways have been discussed in many hybrid WMN architectures [14][15][16][17][18][19][20], as shown in Figure 1(a). The advantages of using relays are as the follows. Firstly, additional communication relays can improve the connectivity of the WMN, because they can interconnect clients in different areas and can also cover areas disconnected with each other. For example, in the traditional WMN, client m 1 cannot communicate with client m 3 because they are in different communication areas and the two areas are not connected. On the other hand, in the hybrid WMN shown in Figure 1 (b), client m 1 can communicate with client m 3 because their communication areas are connected by communication relays.Secondly, additional communication relays can decrease communication delay and increase network throughput. Communication relays are usually more powerful than regular node in that they can be equipped with multiple interfaces, directional antenna, improved transceivers...