Joint power control and scheduling for minimizing broadcast delay in Wireless Mesh Networks

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.