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 nonlinear and nonconvex.
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: 1) joint design provides a significant throughput gain over a default configuration in slotted-ALOHA-based wireless networks; and 2) 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. Joint Routing and Medium Access Control in Fixed Random Access Wireless Multihop Networks
In a single-channel wireless network, during a transmission, the interference seen by a receiver is the additive interference from all the other simultaneous transmissions. As a consequence, it is essential to use a proper interference model when configuring the wireless network. The physical interference model based on signal-to-interference-plus-noise ratio (SINR) is the more realistic interference model for wireless networks. Simpler interference models such as primary interference model, protocol model, and capture threshold model can provide misleading insights about the optimal configuration of routing, medium access control (MAC), and physical-layer parameters as well as throughput improvements by joint design
In this paper, we first study the optimal joint configuration of routing, access probability, and transmission rate parameters in slotted ALOHA fixed wireless networks to maximize the minimum throughput of the flows under an interference model based on SINR.In this paper, we study a simple MAC protocol and a simple network coding scheme to keep the formulation tractable. Our objectives are to provide insights on: 1) the interaction of routing, access probability, network coding, and transmission rate; 2) the throughput gains obtained by a joint design over a default design; and 3) throughput gains obtained by simple network coding.