Diego G. Passos

A joint approach to routing metrics and rate adaptation in wireless mesh networks

This paper presents MARA, a joint mechanism for automatic rate selection and route quality evaluation in wireless mesh networks. This mechanism targets at avoiding the problems of lack of synchronization between metric and rate selection decisions and inaccurate link quality estimates, common to main existing proposals of multihop wireless routing metrics and automatic rate adaptation. In this proposal, the statistics collected by the routing protocol are used by the rate adaptation algorithm to compute the best rate for each wireless link. This coordinated decision aims at providing better routing and rate choices. In addition to the basic MARA algorithm, two variations are proposed: MARA-P and MARA-RP. The first considers the size of each packet in the transmission rate decision. The second variation considers the packet size also for the routing choices. For evaluation purposes, experiments were conducted on both real and simulated environments. In these experiments, MARA was compared to a number of rate adaptation algorithms and routing metrics. Results from both environments indicate that MARA may lead to an overall network performance improvement.

On the impact of user mobility on peer-to-peer video streaming

Wireless mesh networks are emerging as a promising solution for ubiquitous Internet access with mobility support. In such networks, user mobility may lead to Internet gateway changes and consequently, impact the performance of continuous media applications. In this article, we investigate the impact of user mobility on the performance of peer-to-peer video applications over wireless mesh networks. Peer-to-peer video streaming applications rely on the collaborative behavior of peers to assist the source in delivering multimedia content, reduce costs, and increase the scalability of video distribution. We identify practical issues related to mobility for P2P video streaming implementation in WMNs, such as addressing and forwarding strategies. Furthermore, we evaluate the performance of different P2P streaming applications as the user walks in our WMN testbed. Results indicate mobile users benefit from the frequent shortlived connections established in modern P2P video sessions.

Minimum loss multiplicative routing metrics for wireless mesh networks

Wireless mesh networks are low-cost self-configurable multihop networks. This work presents a study about the main routing metrics used in this kind of network, pointing out their virtues and limitations. It also proposes, implements, and analyzes alternative multiplicative metrics. To evaluate the performance of the proposed metrics, comparative measurements over real mesh testbeds were conducted. A case study of a production mesh network using a multiplicative routing metric is also evaluated. Results show that, in various scenarios, the network performance with the proposed multiplicative routing metrics has been improved in terms of routing stability, packet loss rate, end-to-end delay, and throughput.

Mesh Topology Viewer (MTV): an SVG-based interactive mesh network topology visualization tool

This paper discusses wireless mesh network topology visualization tools and their requirements. It presents an interactive tool for visualizing mesh network topologies. The proposed tool uses the SVG - scalable vector graphics - web standard, which is based on XML, to build the network map. In a wireless mesh network, link quality varies quite often, therefore the visualization tool dynamically displays the quality metric of each link, in addition to presenting router configuration information and other network statistics. This work also introduces a configuration tool designed to adapt the topology view to different wireless mesh environments.

Management Issues on Wireless Mesh Networks

Wireless mesh networks (WMN) are emerging as a flexible and low-cost alternative to provide digital inclusion through multi-hop communications, supporting applications from last-mile Internet delivery, search and rescue, home networking to distributed gaming. Managing increasingly large and unplanned WMNs has many challenges. This paper has the primary goal of raising management issues in wireless mesh networks. Furthermore this work documents the management solutions deployed by the ReMesh project 1 in terms of network configuration, topology view, access control, performance measurement and statistics.

A comprehensive analysis on the use of schedule-based asynchronous duty cycling in wireless sensor networks

Duty cycling is a fundamental mechanism for battery-operated ad hoc networks, such as Wireless Sensor Networks, Delay Tolerant Networks, and solar-powered Wireless Mesh Networks. Because of its utter importance, it has been proposed in a wide variety of flavors, one of the most prominent being that of the asynchronous mechanisms. In particular, schedule-based duty cycling has earned attention due to its low requirements and simplicity of implementation. Despite its potential, a comprehensive and realistic study on the neighbor discovery latency that results from schedule-based asynchronous duty cycling is still missing. This paper fills in this gap, by providing accurate models for major schedule-based mechanisms: Block Designs, Quorum systems and Disco. The provided models consider message loss probability and yield more precise estimations than traditional models. Based on this improved accuracy, the relative latency, a new metric for studying the trade off between latency and power, is proposed as a substitute to the power-latency product. Finally, a practical mapping of which schedule is more adequate for given requirements of latency, energy savings and link reliability is presented.

Modelling the Data Aggregator Positioning Problem in Smart Grids

Smart meters are responsible for keeping track of user energy consumption in a smart grid infrastructure. This data is periodically sent to one or more data aggregation points (DAPs), typically via wireless communication. Efficiently choosing the best positions for installing DAPs is an NP-Complete problem and therefore a difficult task, specially in big cities that may contain thousands of smart meters in a single neighborhood. Nevertheless, network planning has a major impact on network performance. This work proposes a reduction of the DAP positioning problem to a problem in the optimization area known as the Set Covering and a heuristic to solve it. This reduction considers a pre-processed subset of reliable links estimated based on the neighborhood characteristics, devices communication technology, antenna heights and transmission rate. The obtained solution corresponds to the least number of DAPs, and its positions, necessary to cover an entire neighborhood. Our heuristic divides the problem in smaller independent sets that are solved separately and united afterwards. A post-optimization method is also applied in order to improve the heuristics solution. Heuristic and linear programming techniques are compared and results show that our heuristic is capable of obtaining solutions 0.05% close to the optimal while reducing both the execution time and the memory consumption by 2.27 and 8.14 times, respectively. Additionally, our heuristic was able to obtain results for large instances where the optimal solution failed due to insufficient memory.

Nested block designs

In schedule-based asynchronous duty cycling, nodes activate and deactivate their radio interfaces according to a specially designed wakeup schedule, which guarantees overlapping active time between nodes, irrespective of their synchronization offsets. When compared to synchronous duty cycling, such an approach has the advantage of being simple to implement, eliminating the need for synchronization protocols, complex computations or extra hardware. However, among published proposals, there is no single schedule-based mechanism that provides the lowest latency in all scenarios, when considering duty cycling symmetry, frame delivery probability and duty cycling rate. This paper introduces nested block designs, a new schedule that extends the use of block designs to application scenarios for which they were previously not possible or not as efficient as other schedules. Nested block designs provide the lowest latency among known schedule-based asynchronous duty cycling mechanisms for a wide range of applications, as confirmed by analytical models and real implementations on WSN motes.

A Joint Approach to Routing Metrics and Rate Adaptation in Wireless Mesh Networks

This work proposes MARA, a joint method for automatic rate selection and route quality evaluation in Wireless Mesh Networks. This method targets at avoiding the problem of inaccurate link quality estimates, common to main existing proposals of multi-hop wireless routing metrics. In this proposal, the statistics collected by the routing protocol are used by the rate adaptation algorithm to compute the best rate for each wireless link. This coordinated decision aims at providing better routing and rate choices. Simulation results indicate that MARA leads to an overall improvement in network performance.

MOSKOU: A Heuristic for Data Aggregator Positioning in Smart Grids

Smart grids represent a revolution in efficient energy distribution, requiring a series of new devices that communicate with each other. Thus, in addition to energy, smart grids also induce an information flow. The advanced metering infrastructure (AMI) is a middle-range communication network which provides communication between clients’ smart meters and data aggregation points (DAPs). This paper focuses on determining the minimum number of DAPs and their positions such that every smart meter is covered and able to communicate through good quality wireless links. In our proposal, the AMI planning is seen as an instance of the set covering problem. This instance is built by determining all good quality wireless links between smart meters and potential DAP installation sites. The proposal is further extended to consider the possibility of multi-hop communication and to find solutions with a given minimum coverage redundancy for each meter. We solve the problem by applying a heuristic, named memory oriented split using