Abstract-We study the delay performance of a sensor network, whose nodes access the medium by using the unslotted MAC protocol specified by the IEEE 802.15.4 standard. Unlike previous works which focus on the average throughput and delay analysis, we develop a detailed model that allows us to obtain the delivery delay distribution of messages sent by concurrently contending sensors toward a central controller. We carry out a transient analysis, which is of particular interest when sensor networks are deployed to provide k-coverage for real-time applications, and validate our analytical results against simulation results obtained through ns2. Wireless sensor networks (WSN) are often used for realtime applications, such as environment surveillance, medical care, and vehicle traffic control [1] . In these contexts, in spite of the severe resource limitations that characterize the sensor nodes, WSNs have to provide a reliable coverage of the area of interest as well as to meet severe timing constraints. In this work, we focus on WSNs for event detection, where each spatial point of the controlled area is covered by k sensors. Upon an event occurrence, each of the k nodes generate a detection report and try to transmit it to a central controller. At the MAC layer, we assume that the sensor nodes implement the IEEE 802.15.4 contention-based scheme, i.e., the emerging standard for low-rate, low-power wireless personal area networks. Furthermore, we consider that the central controller detects an event if it receives m positive detection reports from different sensors (with m ≤ k), within a time interval of t d seconds from the arrival of the first positive report. Note that, when m > 1, this corresponds to considering group-based detection -a widely used technique in real WSN applications to avoid false positive alarms [2], [4] . Under this scenario, we pose the following questions: i) What is the delay distribution of the detection reports transmitted by the sensors, conditioned on their order of arrival at the central controller? ii) Given that the central controller needs to receive m ≤ k reports to perform reliable detection, what is a good value for k, considering that the larger the value of k, the higher the contention on the radio channel? iii) Given k and the value of t d imposed by the application, how many reports one can hope to receive at the central controller by the given time constraint? While the problem of providing k-coverage in a connected communication topology has been widely addressed,
Gribaudo et al REF built a detailed model to obtain the delivery delay distribution of events sent by concurrently contending sensors toward a central controller and carried out a transient analysis for delay performance.
Analysis of IEEE 802.15.4 Sensor Networks for Event Detection
GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference
GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference
Computer Science