Improving the scalability of MAC protocols in wireless mesh network

Includes abstract.Includes bibliographical references (leaves 128-133).Efficient utilization of multi-channels is critical for the success of multi-channel MACprotocols. Unfortunately, current multi-channel MAC protocols are not efficient in the utilization of the multiple channels. The poor utilization of the available channels is also affected by the following: channel coordination, channel selection, and channel scheduling strategies, which do not lend themselves to scalability and the efficient use of the multiple channels. Good channel coordination and selection techniques are therefore required to improve the efficiency of the multi-channel MAC protocols. These techniques should be coupled with effective and scalable signalling techniques, which reduce substantial signalling overhead. A multi-channel Cyclical Scheduling Algorithm (CSA) is proposed to address these challenges

Integrated Scheduling and Beam Steering for Spatial Reuse

This document describes an approach to integrating antenna selection and control into a time-division MAC scheduling process. I argue that through such integration it is possible to achieve greater spatial reuse and interference mitigation than by solving the two problems separately. Without coupling between the MAC scheduling and physical antenna configuration processes, a \u22chicken-and-egg\u22 problem exists: If antenna decisions are made before scheduling, they cannot be optimized for the communication that will actually occur. If, on the other hand, the scheduling decisions are made first, the scheduler cannot know what the actual interference and communications properties of the network will be. This dissertation presents algorithms for optimal spatial reuse TDMA scheduling with reconfigurable antennas. I present and solve the joint beam steering and scheduling problem for spatial reuse TDMA and describe an implemented system based on the algorithms developed. The algorithms described achieve up to a 600% speedup over TDMA in the experiments performed. This is based on using an optimization decomposition approach to arrive at a working distributed protocol which is equivalent to the original problem statement while also producing optimal solutions in an amount of time that is at worst linear in the size of the input. This is, to the best of my knowledge, the first actually implemented STDMA scheduling system based on dual decomposition. This dissertation identifies and briefly address some of the challenges that arise in taking such a system from theory to reality

Design and implementation of a multi-channel multi-interface network

The use of multiple wireless channels has been advocated as one approach for enhancing network capacity. In many scenarios, hosts will be equipped with fewer radio interfaces than available channels. Under these scenarios, several protocols, which require interfaces to switch frequently, have been proposed. However, implementing protocols which require frequent interface switching in existing operating systems is non-trivial. In this paper, we identify the features needed in the operating system kernel for supporting frequent interface switching. We present a new channel abstraction module to support frequent interface switching. We identify modifications to interface device driver to reduce switching delay. The channel abstraction module, and an example multi-channel protocol that uses the module, have been implemented in a multi-channel multi-interface testbed. We also present results to quantify the overheads of frequent switching