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Many efforts have been done to better exploit multiple radios and multiple channels to improve system performance in wireless mesh networks. However, in the case of the IEEE 802.11b/g/n family of standards, there are only three non-overlapping channel, the simple use of orthogonal channels cannot effectively eliminate the interference. The simultaneous use of multiple partially overlapping channels has been certified as an effective way to further eliminate interference and improve network performance in 802.11-based wireless mesh networks. Good network topological structure can lead to low interference, load balancing and high throughput. This research looks into the problem of topology control and partially overlapping channel assignment to improve the performance of multi-radio multi-channel multirate wireless mesh networks. We propose an optimal topology control algorithm and greedy channel assignment algorithm to maximize the network capacity (in term of each node’s traffic delivery ratio). Simulation results present that our topology control and partially overlapping channel assignment method can dramatically improve system throughput.

Due to the limited number of orthogonal channels in IEEE 802.11 b/g standards, the simple application of non-overlapping channels cannot completely eliminate the interference. POCs-based channel assignment has been identified as an emerging technology to further eliminate interference and improve system throughput. This research looks into the problem of partially overlapping channel assignment to improve the performance of multi-radio multi-channel multirate wireless mesh networks. Based on the analysis of the existing methods, we propose a greedy channel assignment method to maximize system throughput. Simulation results presents that our partially overlapping channel assignment method can be dramatically improved by fully exploiting partially overlapping channels as well as orthogonal channels.

Using directional antennas to reduce interference and improve throughput in multihop wireless networks has attracted much attention from the research community in recent years. In this paper, we consider the issue of minimum delay broadcast in multirate wireless mesh networks using directional antennas. We are given a set of mesh routers equipped with directional antennas, one of which is the gateway node and the source of the broadcast. Our objective is to minimize the total transmission delay for all the other nodes to receive a broadcast packet from the source, by determining the set of relay nodes and computing the number and orientations of beams formed by each relay node. We propose a heuristic solution with two steps. Firstly, we construct a broadcast routing tree by defining a new routing metric to select the relay nodes and compute the optimal antenna beams for each relay node. Then, we use a greedy method to make scheduling of concurrent transmissions without causing beam interference. Extensive simulations have demonstrated that our proposed method can reduce the broadcast delay significantly compared with the methods using omnidirectional antennas and single-rate transmission. In addition, the results also show that our method performs better than the method with fixed antenna beams. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we address the problem of joint power control and scheduling for minimizing broadcast delay in wireless mesh networks. Given a set of mesh routers and a routing tree rooted from the gateway node, our task is to assign power for each relay node and compute an optimal transmission schedule such that the longest delay for a packet broadcast from the root node to all the other routers is minimized. We consider rate adaption in our scheme. This is a difficult issue. On one hand, if we increase the transmission power, the packet can be transmitted out at a higher data rate, which leads to less delay; on the other hand, a high transmission power would have larger interference range, which makes less nodes that can transmit concurrently and thus cause longer delay to deliver the packet to farther routers. We study the tradeoff between the two parameters, data rate and concurrency, and propose a balanced method for power control and transmission scheduling. We introduce a metric called standard deviation of remaining broadcast time of nodes to determine the priority of the two parameters. When this standard deviation is above a threshold, the transmitting nodes will take the data-rate-first approach to increase the data rate; otherwise the concurrency-first approach will be used to increase the number of concurrent transmissions in the system. Extensive simulations have demonstrated that our proposed method can reduce the broadcast delay significantly compared with the methods using fixed transmission power. In addition, the results also show that our balanced method performs better than both pure data-rate-first method and concurrency-first method.

This paper discusses the QoS topology control problem with consideration of power control and rate adaptation in wireless mesh networks. Our task is to construct a routing forest (a set of trees rooted from the gateway nodes), configure the transmission power of each node, such that the constructed network topology can meet the delivery threshold for all nodes and the system throughput is maximized. We consider transmission rate adaptation in this paper, i.e., the data rate over a link depends on the signal strength at recipient node. Combining with power control and rate adaptation, we propose a collision-load balancing method to construct the routing trees. Our experiments show that power control and rate adaptation scheme can improve the system performance more effectively. Simulation results have also shown that our method can significantly improve the network throughput, compared with shortest path tree (SPT) method.