Joint link rate allocation, routing and channel assignment in multi-rate multi-channel wireless networks

In this paper we address the issue of joint routing, channel assignment, scheduling and link rate allocation in multi-rate multi-channel wireless networks with the goal of increasing network capacity. Many wireless standards support a variety of modulation and coding schemes, which allow devices to choose from several transmission rates. Typically, the highest possible rate is used for transmission, but the potential for increased spatial reuse and capacity exists when using lower rates due to higher interference tolerance. This problem of selecting link rates is further complicated in a multi-channel network. Channel assignment affects the sets of interfering links, and as such also influences the optimal choice of link rates. And there is also an interdependency between routing and both rate and channel assignment. In this work we analyze the joint problem and, due to its hardness, propose a fast heuristic algorithm (JMR) to solve it. We evaluate this algorithm through numerical experiments in a wide variety of configurations, showing that potential for improved capacity via link rate allocation depends on a variety of factors which relate to the capability and need of exploiting spatial reuse, and which include the transmission power, the number of channels and the network architecture and topology. In this work we also propose an architecture for wireless mesh networks with increased capacity and under which optimized rate allocation is shown to notably increase performance. Finally, we evaluate the solutions found by JMR under the ns-3 simulator using the 802.11a protocol stack, where it is shown that physical and MAC layer limitations reduce the performance gain of JMR.