Scheduling in Wireless Networks with Physical Interference Constraints

This thesis studies the wireless link scheduling problem under the physical interference model. Such problem is more realistic than the widely studied wireless scheduling problem under the protocol interference model. However, it is a challenging problem because the physical interference model considers the cumulative effect of the interference powers from all the other concurrent transmitters. This thesis covers the complexity analysis and algorithm design (both centralized and distributed) for such a challenging problem.;We first give a rigorous NP-completeness proof for the power-controlled scheduling with consecutive transmission constraint under the physical interference model. We then present a centralized scheduling algorithm based on a column generation method which finds the optimal schedules and transmit powers. We further consider an integer constraint that requires the number of time slots allocated to a link to be an integer. Building upon the column generation method, we propose a branch-and-price method which can find the optimal integer solution. By simplifying the pricing problem and designing a new branching rule, we significantly improve the efficiency of both the column generation and the branch-and-price methods. For example, the average runtime is reduced by 99.86% in 18-link networks compared with the traditional column generation method.;Due to the inherent complexity of the power-controlled scheduling problem, finding optimal schedules and power allocations for large-size networks will still consume extraordinary large amounts of time despite the performance of our method. We therefore propose an approximation algorithm, called the Guaranteed and Greedy Scheduling (GGS), which can find near optimal solutions within a short runtime. GGS is a polynomial time algorithm with a provable upper bound for the approximation ratio relative to the optimal solution.;For the distributed scheduling algorithm design, we focus on the CSMA (Carrier-Sense Multiple-Access) network, which is the most widely used distributed wireless network in practice. We establish a rigorous conceptual framework, upon which effective solutions to interference-safe transmissions can be constructed under the physical interference model. Specifically, we propose to use the concept of "safe carrier sensing range", which guarantees interference-safe transmissions under the physical interference model. We further propose a novel carrier-sensing mechanism, called Incremental-Power Carrier-Sensing (IPCS), which implements the safe carrier-sensing range concept in a simple way. Extensive simulation results show that IPCS can boost spatial reuse and network throughput by more than 60% relative to the conventional carrier-sensing mechanism.