Luis Villasenor-Gonzalez

Reliable Freestanding Position-Based Routing in Highway Scenarios

Vehicular Ad Hoc Networks (VANETs) are considered by car manufacturers and the research community as the enabling technology to radically improve the safety, efficiency and comfort of everyday driving. However, before VANET technology can fulfill all its expected potential, several difficulties must be addressed. One key issue arising when working with VANETs is the complexity of the networking protocols compared to those used by traditional infrastructure networks. Therefore, proper design of the routing strategy becomes a main issue for the effective deployment of VANETs. In this paper, a reliable freestanding position-based routing algorithm (FPBR) for highway scenarios is proposed. For this scenario, several important issues such as the high mobility of vehicles and the propagation conditions may affect the performance of the routing strategy. These constraints have only been partially addressed in previous proposals. In contrast, the design approach used for developing FPBR considered the constraints imposed by a highway scenario and implements mechanisms to overcome them. FPBR performance is compared to one of the leading protocols for highway scenarios. Performance metrics show that FPBR yields similar results when considering freespace propagation conditions, and outperforms the leading protocol when considering a realistic highway path loss model.

QUATTRO: QoS-Capable Cross-Layer MAC Protocol for Wireless Sensor Networks

As the wireless sensor network (WSN) technology evolves towards higher transmission rates, it makes sense to start considering sensing and transmission of real-time information, such as audio and video. These applications require quality of service (QoS) guarantees, not offered by current networks. The multi-hop nature of WSN makes QoS a challenging task. In addition, researchers have recently realized that cross-layer protocols achieve a far better performance than protocol layers working in isolation. These two ingredients are the focus of our work. In this paper we propose an architecture in which the MAC and routing protocols collaborate to discover and reserve routes, to organize nodes into clusters and to schedule the access to the transmission medium in a coordinated timeshared fashion. As a consequence, not only QoS is achieved but also great energy savings by eliminating collisions and considerably reducing idle listening. The resulting protocol is called QUATTRO: QUAlity-of-service-capable clusTer-based Timeshared ROuting-assisted MAC protocol. We evaluate our proposal using simulations by examining multiple scenarios in which different numbers and densities of nodes are considered. Our results show that the protocol overhead is reasonable.

Cooperation Mechanism Taxonomy for Wireless Sensor and Actor Networks

A Wireless Sensor and Actor Network (WSAN) is composed of sensor and actor nodes distributed in a geographic area of interest; the sensors are involved in monitoring the physical environment, while the actors can execute a designated task in accordance to the data collected and reported by the sensors during an event. To achieve a balanced performance, a WSAN architecture must implement an efficient cooperative communication strategy to allow the nodes to collaborate in the optimal assignment of resources and to execute tasks with the lowest possible delay. Such collaboration must take place by exchanging information and generating negotiated decisions while trying to extend the WSAN lifetime. The main contribution of this work is the proposal of a coordination mechanism taxonomy for WSANs; this taxonomy provides a framework for the classification of coordination mechanisms designed for WSAN environments. Based on this taxonomy, a comparative analysis is presented to study some of the most representative coordination mechanisms proposed in the area of WSANs up to this date.

Cross-layer medium access control protocol with quality-of-service guarantees for wireless sensor networks

There is increasing demand for wireless sensor networks (WSN) to be able to carry real-time information. However, current WSN technologies are not yet capable of offering quality-of-service (QoS) guarantees, which are required to support these types of applications. Achieving QoS is especially challenging in WSNs due to their multi-hop nature and their processing-power, memory, and energy constraints. In this article, we propose a cross-layer architecture in which the medium access control (MAC) and routing protocols collaborate to organize nodes into clusters and to achieve a coordinated time-shared access to the transmission medium. The resulting protocol is called QUAlity-of-service-capable clusTer-based Time-shared ROuting (QUATTRO)-assisted MAC protocol. Our performance evaluation results show that the protocol overhead observed in terms of configuration time, transmitted control messages, and consumed energy is very reasonable and that not only QoS is achieved but also great energy savings by eliminating collisions and considerably reducing idle listening.

Design Issues and Considerations for Coordination Mechanisms in Wireless Sensor and Actuator Networks

A wireless sensor and actuator network (WSAN) is commonly integrated by a large quantity of sensor nodes and a lower number of actuator nodes which communicate throughout the wireless medium providing distributed sensing and executing specific tasks according to the events monitored in a specific area of interest. The sensors are involved in monitoring the physical environment, while the actuators execute specific actions in response to the data provided by the sensors. In this way, sensors and actuators coordinate in an efficient way while trying to respond within the comply with the requirements of the application; to achieve this a coordination mechanism is implemented to allow the sensor and actuator nodes to make an optimum assignment of resources, while enabling a response with the lowest possible delay. This work presents the basic design considerations to take into account in the design of a coordination mechanism for WSANs; it also presents a brief comparative analysis among the most representative coordination mechanisms proposed in the area of WSANs.

Routing Strategies for Wireless Sensor Networks

This paper evaluates three routing strategies for wireless sensor networks: source, shortest path, and hierarchical-geographical, which are the three most commonly employed by wireless ad-hoc and sensor networks algorithms. Source routing was selected because it does not require costly topology maintenance, while shortest path routing was chosen because of its simple discovery routing approach and hierarchical-geographical routing was elected because it uses location information via Global Positioning System (GPS). The performance of these three routing strategies is evaluated by simulation using OPNET, in terms of latency, End to End Delay (EED), packet delivery ratio, routing overhead, overhead and routing load.

Macromobility support for mobile ad hoc networks using IPv6 and the OLSR routing protocol

Mobile ad hoc networks (MANETs) make use of a distributed routing mechanism to support connectivity between nodes within the ad hoc network. A wireless ad hoc network can be deployed for multiple applications, for example, it can be used to extend the coverage of wire-based networks through the use of a wireless access router. However, the implementation of a hybrid (i.e. wired and wireless) network is not a straight forward process and several issues must be solved for this type of topologies to become a reality. One concern is related to terminal mobility while preserving ongoing communication sessions; as a mobile node moves from one subnetwork to a new subnetwork a mobility protocol must be introduce to allow the mobile node to preserve communication sessions without having to reestablish the session with a correspondent node; this issue becomes more complex in a hybrid network where the wireless domain is composed by a mobile ad hoc network (MANET). For instance, MANET routing protocols usually do not account for the connectivity toward a wired network, such as the Internet. As a result there are multiple routing issues that must be taken into consideration for the support of interconnectivity between nodes located in a hybrid network. In this work we assume that a hybrid network has been deployed and the optimized link state routing (OLSR) protocol is implemented in the ad hoc network; in addition, we consider the implementation of a macromobility mechanism under IPv6. The support of macromobility is achieved via Mobile IPv6, while OLSR provides the routing capabilities within the MANET. The main contribution of this work is the proposal of diverse strategies to improve the layer 3 handoff latency, as a mobile node roams between foreign networks.