Yuen, H. "Ad-Hoc Distributed Telephony"

Abstract

This thesis studies the challenges of providing load balancing and fault-tolerant external links between ad-hoc multicast mesh networks.

The work is the gateway component of a research platform called FluidVoice, a wireless audio communication system. This system consists of nodes forming a broadcast mesh based on 802.11. Some of these nodes called Stargates have the capability to communicate to the external world. The problem is that these gateways can fail or lose capacity unexpectedly. In this work we explore the ways to provide communications to the external world under unexpected gateway node failures, and variance of load.

We propose and evaluate a distributed algorithm designed to form this robust and balanced interconnection. The algorithm is designed with robustness in mind, and takes into account failures in the outbound links as well as between the gateways, and it is focused to support real-time applications running over it.

In this thesis we show that by adopting this algorithm, we can provide a reliable connection to the end-user even as gateways presence or capacity varies. The prototype version has about 20ms of additional transmission time in average, with an overhead of about 5% to 35% depending on the packet size, and a recovery time of 1 to 3 seconds. The redundant traffic generated in intermediate steps of the optimization problem can grow up proportionally to the number of participating gateway nodes, and reduces quickly to only the required amount of traffic.