A Lightweight Medium Access Protocol (LMAC) for Wireless Sensor Networks: Reducing Preamble Transmissions and Transceiver State Switches

In this paper, we present an energy-efficient medium access protocol designed for wireless sensor networks. Although the protocol uses TDMA to give nodes in the WSN the opportunity to communicate collision-free, the network is self-organizing in terms of time slot assignment and synchronization. The main goal of the medium access protocol is to minimize overhead of the physical layer. The protocol reduces the number of transceiver state switches and hence the energy wasted in preamble transmissions. The protocol is compared to SMAC and EMACs by simulation. The LMAC protocol is able to extend the network lifetime by a factor 2.4 and 3.8, compared to EMACs and SMAC respectively

Design Aspects of An Energy-Efficient, Lightweight Medium Access Control Protocol for Wireless Sensor Networks

This document gives an overview of the most relevant design aspects of the lightweight medium access control (LMAC) protocol [16] for wireless sensor networks (WSNs). These aspects include selfconfiguring and localized operation of the protocol, time synchronization in multi-hop networks, network setup and strategies to reduce latency.\ud The main goal in designing a MAC protocol for WSNs is to minimize energy waste - due to collisions of messages and idle listening - , while limiting latency and loss of data throughput. It is shown that the LMAC protocol performs well on energy-efficiency and delivery ratio [19] and can\ud ensure a long-lived, self-configuring network of battery-powered wireless sensors.\ud The protocol is based upon scheduled access, in which each node periodically gets a time slot, during which it is allowed to transmit. The protocol does not depend on central managers to assign time slots to nodes.\ud WSNs are assumed to be multi-hop networks, which allows for spatial reuse of time slots, just like frequency reuse in GSM cells. In this document, we present a distributed algorithm that allows nodes to find unoccupied time slots, which can be used without causing collision or interference to other nodes. Each node takes one time slot in control to\ud carry out its data transmissions. Latency is affected by the actual choice of controlled time slot. We present time slot choosing strategies, which ensure a low latency for the most common data traffic in WSNs: reporting of sensor readings to central sinks

Distributed Coverage Area Reporting for Wireless Sensor Networks

In order to efficiently deal with subscriptions or other location dependent information, it is key that the wireless sensor network informs the gateways what geographical area is serviced by which gateway. The gateways are then able to e.g. efficiently route subscriptions which are only valid in particular regions of the deployment. \ud \ud In our distributed approach of establishing a description of WSN coverage area per gateway, we let nodes keep track of the convex hull of the coverage area. In this way, gateways are efficiently informed of the service areas, while we limit the amount of information each node needs to store, transmit and receive

Design of Combined Coverage Area Reporting and Geo-casting of Queries 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.\u

An Application-Tailored MAC Protocol for Wireless Sensor Networks

We describe a data management framework suitable for wireless sensor networks that can be used to adapt the performance of a medium access control (MAC) protocol depending on the query injected into the network. The framework has a\ud completely distributed architecture and only makes use of information available locally to capture information about network traffic patterns. It allows\ud nodes not servicing a query to enter a dormant mode which minimizes transmissions and yet maintain an updated view of the network. We then introduce an Adaptive, Information-centric and Lightweight MAC\ud (AI-LMAC) protocol that adapts its operation depending on the information presented by the framework. Our results demonstrate how transmissions are greatly reduced during the dormant mode. During the active mode, the MAC\ud protocol adjusts fairness to match the expected requirements of the query thus reducing latency. Thus such a data management framework allows the MAC to operate more efficiently by tailoring its needs to suit the requirements of the application

Analysis of a Self-organizing Algorithm for Time Slot Selection in Schedule-based Medium Access

To ensure a long-lived network of wireless communicating sensors, it is necessary to have a medium access control protocol that is able to prevent energy-wasting behaviour 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 non-conflicting schedules. We present such a scheduling mechanism, which allows wireless sensors to choose a time interval for transmission, which is not interfering or causing collisions with other transmissions. We analyze the scheduling mechanism in the case that many nodes enter the time interval selection procedure simultaneously and potentially multiple selection rounds are required before each node has a non-conflicting schedule. In our proposed solution, we do not assume any hierarchical organization in the network and all operation is localized, making the network self-con��?guring

A Low-Latency, Information-Centric Medium Access Protocol for Wireless Sensor Networks

In this paper 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 traf��?c patterns in the network. This information is subsequently used by AI-LMAC to modify its operation accordingly. We present preliminary results showing how the MAC protocol ef��?ciently manages the issues of fairness, latency and message buffer management

Impact of Network Density on Bandwidth Resource Management in WSN

We describe a self-organizing, clustering protocol for bandwidth resource management in Wireless Sensor Networks. The proposed protocol allows the sensor nodes to communicate by a time-slotted, scheduled MAC algorithm. When the nodes are densely deployed, i.e., the connectivity is very high, the MAC algorithm may not provide access for all of the nodes due to the limited number of time-slots, consequently the network capacity degrades. To overcome this drawback, we extend the time-slotted MAC algorithm by clustering the nodes into direrent frequency domains while they can use the same time domain. The idea is basically to multiplex the time domain with the frequency domain. As a result, the number of nodes that are granted access to the wireless medium is increased by the number of frequency channels available. By using simulations, we evaluate the performance of the protocol. The results reveal that frequency multiplexing has the erect of increasing the capacity up to 100%