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Abstract-We study cross-layer design in random access based fixed wireless multihop networks under a physical interference model. Due to the complexity of the problem, we consider a simple slotted ALOHA medium access control (MAC) protocol for link layer operation. We formulate a joint routing, access probability, and rate allocation optimization problem to determine the optimal max-min throughput of the flows and the optimal configuration of the routing, access probability, and transmission rate parameters in a slotted ALOHA system. We then also adapt this problem to include an XOR-like network coding without opportunistic listening. Both problems are complex non-linear and non-convex.We provide extensive numerical results for both problems for medium-size mesh networks using an iterated optimal search technique. Via numerical and simulation results, we show that (i) joint design provides a significant throughput gain over a default configuration in slotted ALOHA based wireless networks, and (ii) the throughput gain obtained by the simple network coding is significant, especially at low transmission power. We also propose simple heuristics to configure slotted ALOHA based wireless mesh networks. These heuristics are extensively evaluated via simulation and found to be very efficient.

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