L.F.W. van Hoesel

AI-LMAC: an adaptive, information-centric and lightweight MAC protocol for wireless sensor networks

We present a novel TDMA-based medium access control (MAC) protocol for wireless sensor networks. Unlike conventional MAC protocols, which function independently of the application, we introduce an adaptive, information-centric and lightweight MAC (AI-LMAC) protocol that adapts its operation depending on the requirements of the application. We also present a completely localised data management framework that helps capture information about traffic patterns in the network. This information is subsequently used by AI-LMAC to modify its operation. The data management-framework can additionally be used for efficient query dissemination and query optimisation. We present preliminary results showing how the MAC protocol efficiently manages the issues of fairness and latency.

Advantages of a TDMA based, energy-efficient, self-organizing MAC protocol for WSNs

The paper presents EMACs, a medium access protocol especially designed for wireless sensor networks. The medium access protocol consists of a fully distributed and self-organizing TDMA scheme, in which each active node periodically listens to the channel and broadcasts a short control message. This control message is needed for medium access operation and is also used to piggy back various types of information at low energy costs. Information in the control message is used to create a maximal independent set of nodes. This set of nodes creates a connected network and nodes in the set are active, while other nodes are passive and save energy by exploiting the infrastructure created by the connected network. The presented approach is compared in simulation with the SMAC protocol (a medium access protocol with coordinated adaptive sleeping) in a realistic multi-hop network setup where sensor readings are transported to a specific node and routes are established using the dynamic source routing protocol. The EMACs protocol is able to extend the network lifetime by 30% to 55% compared to SMAC in a static network topology, and in a dynamic network topology, EMACs prolongs the network lifetime by a factor of 2.9 to 4.2.

A TDMA-based MAC protocol for WSNs

This paper presents EMACs, a medium access protocol especially designed for wireless sensor networks. Wireless sensor networks differ greatly from traditional ad hoc wireless networks and therefore require the usage of new types of network protocols, which are energy-efficient to ensure a node lifetime of several years on a single battery and which can operate without assistance of central managers in a dynamic network topology.

Collision-free Time Slot Reuse in Multi-hop Wireless Sensor Networks

To ensure a long-lived network of wireless communicating sensors, we are in need of a medium access control protocol that is able to prevent energy-wasting effects like idle listening, hidden terminal problem or collision of packets. Schedule-based medium access protocols are in general robust against these effects, but require a mechanism to establish a non-conflicting schedule. In this paper, we present such a mechanism which allows wireless sensors to choose a time interval for transmission, which is not interfering or causing collisions with other transmissions. In our solution, we do not assume any hierarchical organization in the network and all operation is localized. We empirically show that our localized algorithm is successful within a factor 2 of the minimum necessary time slots in random networks; well in range of the expected (worst case) factor 3-approximation of known first-fit algorithms. Our algorithm assures similar minimum distance between simultaneous transmissions as CSMA(/CD)-based approaches.

On the design of an energy-efficient low-latency integrated protocol for distributed mobile sensor networks

Self organizing, wireless sensors networks are an emergent and challenging technology that is attracting large attention in the sensing and monitoring community. Impressive progress has been done in recent years even if we need to assume that an optimal protocol for every kind of sensor network applications can not exist. As a result it is necessary to optimize the protocol for certain scenarios. In many applications for instance latency is a crucial factor in addition to energy consumption. MERLIN performs its best in such WSNs where there is the need to reduce the latency while ensuring that energy consumption is kept to a minimum. By means of that, the low latency characteristic of MERLIN can be used as a trade off to extend node lifetimes. The performance in terms of energy consumption and latency is optimized by acting on the slot length. MERLIN is designed specifically to integrate routing, MAC and localization protocols together. Furthermore it can support data queries which is a typical application for WSNs. The MERLIN protocol eliminates the necessity to have any explicit handshake mechanism among nodes. Furthermore, the reliability is improved using multiple path message propagation in combination with an overhearing mechanism. The protocol divides the network into subsets where nodes are grouped in time zones. As a result MERLIN also shows a good scalability by utilizing an appropriate scheduling mechanism in combination with a contention period.

Ideas on node mobility support in schedule-based medium access

Typically, medium access control (MAC) protocols for wireless sensor networks implement synchronised periodic sleeping to conserve energy. We argue that (local) synchronisation between nodes is the main cause why MAC protocols do not efficiently support node mobility e.g. nodes waste valuable energy to resynchronise. In this paper, we present ideas on mobility support in schedule-based medium access control protocols for wireless sensor networks. The resulting MAC protocol is a hybrid protocol, which combines schedule-based access with contention-based access. The rationale is that the static part of the wireless sensor network can benefit from the high delivery ratio and support for high peak loads of schedule-based access, while mobile nodes can benefit from the natural self-organization of contention-based access. We try our protocol ideas by simulation and real-live experiments.

MAC support for high density wireless sensor networks

Large scale and high density networks of tiny sensor nodes offer promising solutions for event detection and actuating applications. In this paper we address the effect of high density of wireless sensor network performance with a specific MAC protocol, the lightweight medium access control (LMAC). We propose a power control support for the LMAC protocol to successfully cope with high density issue. Experimental results show that our power control support significantly increases the number of nodes that can control a timeslot, without affecting other performance metrics such as the latency.

Geo-casting of queries combined with coverage area reporting for wireless sensor networks

In order to efficiently deal with queries or other location dependent information, it is key that the wireless sensor network informs gateways what geographical area is serviced by which gateway. The gateways are then able to e.g. efficiently route queries which are only valid in particular regions of the deployment. The proposed algorithms combine coverage area reporting and geographical routing of queries which are injected by gateways. The combined solution is evaluated in terms of computational complexity and performance compared with existing geocasting protocols.