André M. Barroso

The development of a novel minaturized modular platform for wireless sensor networks

Wireless sensor networks are collections of autonomous devices with computational, sensing and wireless communication capabilities. Research in this area has been growing in the past few years given the wide range of applications that can benefit from such a technology. In this paper, the development of a highly modular and miniaturized wireless platform for sensor networks is described. The system incorporates a radio transceiver (in the 2.4 GHz ISM Band) with embedded protocol software to minimize power consumption and maximize data throughput. Additional input capability for sensor and actuator integration can be incorporated seamlessly due to the modular nature of the system. The total system is packaged in a modular 25 mm cubed form factor. A smaller, (10 mm cubed), prototype is currently under development. Ongoing development of highly miniaturized nodes is discussed.

/spl mu/-MAC: an energy-efficient medium access control for wireless sensor networks

For the long-term deployment of wireless sensor networks, energy efficient MAC protocols are necessary. The transceiver of a sensor node should only consume energy while actively taking part in communication. Energy consumption in idle mode should be avoided as much as possible. In this paper it is shown how application layer knowledge in the form of flow specifications can be used to improve the energy properties of a MAC protocol. A new protocol, named /spl mu/-MAC, is proposed and evaluated through simulations.

A Novel MAC Protocol for Throughput Sensitive Applications in Vehicular Environments

The current medium access control (MAC) protocol of the wireless access in vehicular environments (WAVE) system is based on IEEE 802.11 distributed coordination function (DCF) and enhanced distributed channel access (EDCA), which have drawbacks in supporting throughput-sensitive applications in high density networks, e.g. future vehicular ad-hoc networks (VANET). In order to address the problem, we propose a novel MAC protocol, namely vehicular MESH network (VMESH), which is specifically designed for the control channel (CCH) and multiple service channels (SCHs) architecture of WAVE system. A synchronized and distributed beaconing scheme is employed by the VMESH protocol for the purposes of neighborhood awareness and dynamic channel resource reservation. In this paper, we present the advantage of VMESH protocol under saturated traffic load condition through theoretical analysis. For more realistic scenarios with mobility and unsaturated traffic loads, through the simulative study, we can also show that the VMESH protocol outperforms the WAVE protocol when the traffic load is heavy.

f-MAC: a deterministic media access control protocol without time synchronization

Nodes in a wireless network transmit messages through a shared medium. Thus, a Media Access Control (MAC) protocol is necessary to regulate and coordinate medium access. For some application areas it is necessary to have a deterministic MAC protocol which can give guarantees on message delay and channel throughput. Schedule based MAC protocols, based on time synchronization among nodes, are currently used to implement deterministic MAC protocols. Time synchronization is difficult and costly, especially in energy constrained sensor networks. In this paper the f-MAC protocol is presented which can give guarantees regarding message delay and channel throughput without the requirement of time synchronization among nodes. The various trade-offs of f-MAC are analysed and discussed and application areas that would benefit from f-MAC are presented.

Determination of aggregation points in wireless sensor networks

A primary goal in the design of wireless sensor networks is lifetime maximization, constrained by the energy capacity of batteries. One well known method to reduce energy consumption in such networks is message aggregation. This method reduces the number of messages transmitted in the network, thus extending its lifetime. In order to be effective, aggregation requires messages to be delayed in their path throughout the network. This technique, therefore, must define where and for how long a message should be delayed. This work shows how aggregation points and corresponding aggregation delays can be determined so that the overall energy efficiency of the system is improved. An algorithm is presented which allows the efficient computation of aggregation points and delays. The benefits of the algorithm are verified through simulation experiments.

The DSYS25 sensor platform

In this demonstration, a new sensor platform named DSYS25 is presented. The platform has a unique hardware design and runs a customized version of the TinyOS operating system. Transceiver hardware and packaging distinguish the D-Systems platform from other available designs.

On the Effects of Aggregation on Reliability in Sensor Networks

Data collected in a sensor network is transported hop-by-hop to a sink for further analysis. The quality of the analysis depends on the amount of data reaching the sink. Hence, data transport reliability influences the quality of the analysis. Data aggregation is a common method used in sensor networks to reduce the amount of messages transported. By aggregating, the data contained in several messages is fused into one single message. Therefore, data aggregation significantly influences the overall data transport reliability observed at the sink. This influence is analyzed and described analytically and by experiment within this paper. Furthermore it is shown how the influence of data aggregation on data transport reliability can be controlled for a particular class of data gathering application

Use of Framelets for Efficient Transmitter-Receiviver rendezvous in Wireless Sensor Networks

A basic problem introduced by the use of radio duty cycles as an energy saving technique is needed to establish rendezvous between transmitter and receiver. Since communication can only take place when the receivers radio is active, the transmission of frames needs to somehow overlap with this active period. This paper investigates the use of framelets - small, fixed sized frames - to achieve transmitter-receiver rendezvous and contrasts this technique with the use of long frames. The benefits of applying framelets is assessed analytically and an implementation of the concept for the DSYS25 sensor platform is presented and evaluated. The results show that substantial energy savings can be achieved with framelets as well as an increase in communication throughput

Maintenance efficient routing in wireless sensor networks

This paper presents an analysis framework of routing protocols that can be applied to produce sensor fields that are much less expensive to maintain. The framework is based on a maintenance model that is simple, yet flexible enough to capture real world deployment scenarios of sensor networks. As an illustration, the framework is used to assess the impact of different forwarding techniques for a known geographical routing protocol on the overall maintenance costs of different sensor fields. The results obtained indicate that a one-size-fits-all approach for the design of maintenance efficient routing protocols does not hold in large deployments of wireless sensor networks. However, savings of up to 50% in maintenance cost were observed through simple modifications of the forwarding strategy.