Lodewijk van Hoesel

MC-LMAC: A multi-channel MAC protocol for wireless sensor networks

In traditional wireless sensor network (WSN) applications, energy efficiency may be considered to be the most important concern whereas utilizing bandwidth and maximizing throughput are of secondary importance. However, recent applications, such as structural health monitoring, require high amounts of data to be collected at a faster rate. We present a multi-channel MAC protocol, MC-LMAC, designed with the objective of maximizing the throughput of WSNs by coordinating transmissions over multiple frequency channels. MC-LMAC takes advantage of interference and contention-free parallel transmissions on different channels. It is based on scheduled access which eases the coordination of nodes, dynamically switching their interfaces between channels and makes the protocol operate effectively with no collisions during peak traffic. Time is slotted and each node is assigned the control over a time slot to transmit on a particular channel. We analyze the performance of MC-LMAC with extensive simulations in Glomosim. MC-LMAC exhibits significant bandwidth utilization and high throughput while ensuring an energy-efficient operation. Moreover, MC-LMAC outperforms the contention-based multi-channel MMSN protocol, a cluster-based channel assignment method, and the single-channel CSMA in terms of data delivery ratio and throughput for high data rate, moderate-size networks of 100 nodes at different densities.

Energy-efficient link-layer jamming attacks against wireless sensor network MAC protocols

A typical wireless sensor node has little protection against radio jamming. The situation becomes worse if energy-efficient jamming can be achieved by exploiting knowledge of the data link layer. Encrypting the packets may help to prevent the jammer from taking actions based on the content of the packets, but the temporal arrangement of the packets induced by the nature of the protocol might unravel patterns that the jammer can take advantage of, even when the packets are encrypted. By looking at the packet interarrival times in three representative MAC protocols, S-MAC, LMAC, and B-MAC, we derive several jamming attacks that allow the jammer to jam S-MAC, LMAC, and B-MAC energy efficiently. The jamming attacks are based on realistic assumptions. The algorithms are described in detail and simulated. The effectiveness and efficiency of the attacks are examined. In addition, we validate our simulation model by comparing its results with measurements obtained from actual implementation on our sensor node prototypes. We show that it takes little effort to implement such effective jammers, making them a realistic threat. Careful analysis of other protocols belonging to the respective categories of S-MAC, LMAC, and B-MAC reveals that those protocols are, to some extent, also susceptible to our attacks. The result of this investigation provides new insights into the security considerations of MAC protocols.

Modelling and verification of the LMAC protocol for wireless sensor networks

In this paper we report on modelling and verification of a medium access control protocol for wireless sensor networks, the LMAC protocol. Our approach is to systematically investigate all possible connected topologies consisting of four and of five nodes. The analysis is performed by timed automaton model checking using Uppaal. The property of main interest is detecting and resolving collision. Evaluation of this property for all connected topologies requires more than 8000 model checking runs. Increasing the number of nodes would not only lead increase the state space, but to a greater extent cause an instance explosion problem. Despite the small number of nodes this approach gave valuable insight in the protocol and the scenarios that lead to collisions not detected by the protocol, and it increased the confidence in the adequacy of the protocol.

Enabling mobility in heterogeneous wireless sensor networks cooperating with UAVs for mission-critical management

Wireless sensor networks have the promise of revolutionizing the capture, processing, and communication of mission-critical data for the use of first operational forces. Their low cost, low power, and size make it feasible to embed them into environment monitoring tags in critical care regions, first responders uniform gear, and data collector sinks attached to unmanned aerial vehicles. The ability to actively change the location of sensors can be used to mitigate some of the traditional problems associated with static sensor networks. On the other hand, sensor mobility brings its own challenges. These include challenges associated with in-network aggregation of sensor data, routing, and activity monitoring of responders. Moreover, all different mobility patterns (e.g., sink mobility, sensor mobility) have their special properties, so that each mobile device class needs its own approach. In this article, we present a platform which benefits from both static and mobile sensors and addresses these challenges. The system integrates WSNs, UAVs, and actuators into a disaster response setting, and provides facilities for event detection, autonomous network repair by UAVs, and quick response by integrated operational forces.

Collaborative algorithms for communication in wireless sensor networks

In this paper, we present the design of the communication in a wireless sensor network. The resource limitations of a wireless sensor network, especially in terms of energy, require an integrated, and collaborative approach for the different layers of communication. In particular, energy-efficient solutions for medium access control, clusterbased routing, and multipath creation and exploitation are discussed. The proposed MAC protocol is autonomous, decentralized and designed to minimize power consumption. Scheduling of operations, e.g. for the MAC protocol, is naturally supported by a clustered structure of the network. The multipath on-demand routing algorithm improves the reliability of data routing. The approaches taken and presented are designed to work together and support each other.

A cross-layered communication protocol for load balancing in large scale multi-sink wireless sensor networks

One of the fundamental operations in sensor networks is convergecast which refers to the communication pattern in which data is collected from a set of sensor nodes and forwarded to a common end-point gateway, namely sink node, in the network. In case of multiple sinks within the network, the total load of the network has to be balanced among these sinks to minimize the problem of packet loss in the convergecast process in wireless sensor networks (WSNs) due to congestion and collisions near the sinks. In this paper, we present a novel cross-layered communication protocol for efficient data dissemination in multi-sink WSNs which is under consideration of SENSEI project. It basically combines network wide load balancing, clustering techniques and local routing optimizations with SENSEI architecture which make it efficient on both global and local level. The performance evaluation of the proposed technique shows how our routing protocol can balance the network load without additional control packets for routing tree maintenance.

On Mobility Management in Multi-Sink Sensor Networks for Geocasting of Queries

In order to efficiently deal with location dependent messages in multi-sink wireless sensor networks (WSNs), it is key that the network informs sinks what geographical area is covered by which sink. The sinks are then able to efficiently route messages which are only valid in particular regions of the deployment. In our previous work (see the 5th and 6th cited documents), we proposed a combined coverage area reporting and geographical routing protocol for location dependent messages, for example, queries that are injected by sinks. In this paper, we study the case where we have static sinks and mobile sensor nodes in the network. To provide up-to-date coverage areas to sinks, we focus on handling node mobility in the network. We discuss what is a better method for updating the routing structure (i.e., routing trees and coverage areas) to handle mobility efficiently: periodic global updates initiated from sinks or local updates triggered by mobile sensors. Simulation results show that local updating perform very well in terms of query delivery ratio. Local updating has a better scalability to increasing network size. It is also more energy efficient than our previously proposed approach, where global updating in networks have medium mobility rate and speed.