Browsing by Author "Robinson, Joshua"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    A performance study of deployment factors in wireless mesh networks
    (2007) Robinson, Joshua; Knightly, Edward W.
    This thesis presents a measurement-parameterized performance study of deployment factors in wireless mesh networks using four performance metrics: client coverage area, backhaul tier connectivity, protocol-dependent throughput, and per-user fair rates. For each metric, I identify and study deployment factors which strongly influence mesh performance via an extensive set of Monte Carlo simulations capturing realistic physical layer behavior. My findings include: (i) A random topology is unsuitable for a large-scale mesh deployment due to doubled node density requirements, yet a moderate level of perturbations from ideal grid placement has minor impact. (ii) Multiple backhaul radios per mesh node is a cost-effective deployment strategy as it leads to mesh deployments costing 50% less than with a single-radio architecture. This work adds to the understanding of mesh deployment factors and their general impact on performance, providing further insight into practical mesh deployments.
  • Thumbnail Image
    Item
    Deployment and assessment of wireless mesh networks
    (2009) Robinson, Joshua; Knightly, Edward W.
    Multi-tier wireless mesh network deployments are a popular, cost-effective means to provide wireless broadband connectivity to neighborhoods and cities. Client devices within the coverage area of a mesh network connect wirelessly to fixed mesh nodes, which then forward traffic directly or via multi-hop paths to capacity injection points. The small number of capacity points act as Internet gateways and reduce overall network cost by limiting the amount of costly wired infrastructure needed. Non-uniform wireless signal propagation and the contention caused by multi-hop traffic contribute the challenge of deploying mesh networks with both high performance and low cost. This dissertation presents and evaluates cost-efficient algorithms for deployment planning and measurement-based assessment of wireless mesh networks. The mesh node placement problem requires mesh nodes to provide ubiquitous network coverage to clients, as well as connectivity amongst mesh nodes. The first contribution of this thesis is to present a graph-theoretic formulation of the NP-hard mesh node placement problem. This is the first formulation which considers the case in outdoor networks where signal propagation is non-uniform and enables the design of graph-theoretic approximation algorithms in order to minimize the deployment size or average contention. Secondly, deployment planning must select locations for the placement of capacity points, as their locations determine the path lengths in the networks and the resulting capacity available to transmit data to and from the Internet. To choose capacity point locations, I first present a technique to efficiently calculate network capacity and then two local search algorithms adapted from solutions to the facility location problem. Third, this thesis presents a framework for the measurement-based verification of a deployed network's performance. To avoid relying on expensive and exhaustive measurement studies, I consider the assessment problem with a limited number of measurements. The framework uses terrain-informed estimation, per-node virtual sectorization, and measurement refinement to accurately predict the network's performance at any given location. I evaluate the presented algorithms on realistic network topologies and with a large-scale measurement study of two currently deployed mesh networks: the TFA network and GoogleWiFi network. The thesis results demonstrate the essential nature of incorporating measurements, realistic propagation, and wireless contention into mesh network planning and assessment techniques.
  • Thumbnail Image
    Item
    Measurement Driven Deployment of a Two-Tier Urban Mesh Access Network
    (ACM Press, 2006-06-01) Camp, Joseph; Robinson, Joshua; Steger, Christopher; Knightly, Edward; Center for Multimedia Communications (http://cmc.rice.edu/)
    Multihop wireless mesh networks can provide Internet access over a wide area with minimal infrastructure expenditure. In this work, we present a measurement driven deployment strategy and a data-driven model to study the impact of design and topology decisions on network-wide performance and cost. We perform extensive measurements in a two-tier urban scenario to characterize the propagation environment and correlate received signal strength with application layer throughput. We find that well-known estimates for pathloss produce either heavily overprovisioned networks resulting in an order of magnitude increase in cost for high pathloss estimates or completely disconnected networks for low pathloss estimates. Modeling throughput with wireless interface manufacturer specifications similarly results in severely underprovisioned networks. Further, we measure competing, multihop flow traffic matrices to empirically define achievable throughputs of fully backlogged, rate limited, and web-emulated traffic. We find that while fully backlogged flows produce starving nodes, rate-controlling flows to a fixed value yields fairness and high aggregate throughput. Likewise, transmission gaps occurring in statistically multiplexed web traffic, even under high offered load, remove starvation and yield high performance. In comparison, we find that well-known noncompeting flow models for mesh networks over-estimate network-wide throughput by a factor of 2. Finally, our placement study shows that a regular grid topology achieves up to 50 percent greater throughput than random node placement.