A dual-radio framework for MAC protocol implementation in wireless sensor networks

10.1109/icc.2011.5962415IEEE International Conference on Communication

Improving link quality by exploiting channel diversity in wireless sensor networks

10.1109/RTSS.2011.22Proceedings - Real-Time Systems Symposium159-169PRSY

Indriya: A low-cost, 3D wireless sensor network testbed

10.1007/978-3-642-29273-6_23Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering90 LNICST302-31

Opportunistic Routing in Low Duty-Cycle Wireless Sensor Networks

Opportunistic routing is widely known to have substantially better performance than unicast routing in wireless networks with lossy links. However, wireless sensor networks are heavily duty-cycled, i.e. they frequently enter sleep states to ensure long network life-time. This renders existing opportunistic routing schemes impractical, as they assume that nodes are always awake and can overhear other transmissions. In this paper we introduce ORW, a practical opportunistic routing scheme for wireless sensor networks. ORW uses a novel opportunistic routing metric, EDC, that reflects the expected number of duty-cycled wakeups that are required to successfully deliver a packet from source to destination. We devise distributed algorithms that find the EDC-optimal forwarding and demonstrate using analytical performance models and simulations that EDC-based opportunistic routing results in significantly reduced delay and improved energy efficiency compared to the traditional unicast routing. We compare the performance of the ORW protocol with other alternatives in both simulations and testbed-based experiments. Our results show that ORW reduces radio duty cycles on average by 50% (up to 90% on individual nodes) and delays by 30% to 90% when compared to the state of the art

DecTDMA: A Decentralized-TDMA with Link Quality Estimation for WSNs

In wireless sensor networks (WSNs), different motes may transmit packets concurrently, i.e., having overlapping transmission periods. As a result of this contention, there are no packet reception guarantees and significant bandwidth can be lost. This contention can have a strong impact on the performance together with other kinds of interference sources, e.g., ambient noise. As a result, WSN’s connectivity tends to have a very dynamic nature. In this paper, we devise DecTDMA (Decentralized-TDMA), a fully decentralized medium access controller (MAC) that significantly reduces contention. It is based on a self-stabilizing algorithm for time division multiple access (TDMA). This self-stabilizing TDMA algorithm uses no external assistance or external references, such as wireless access points (WAPs) and globally-synchronized clocks. We present the design and implementation of DecTDMA and report encouraging results: our Cooja simulations and Indriya testbed experiments show stable connectivity and high medium utilization in both single and multi-hop networks. Since DecTDMA has favorable characteristics with respect to connection stability, we show that common link quality estimation (LQE) techniques further improve the operation of DecTDMA in the dynamic environment of low-power wireless networks

DecTDMA: A Decentralized-TDMA with Link Quality Estimation for WSNs

In wireless sensor networks (WSNs), different motes may transmit packets concurrently, i.e., having overlapping transmission periods. As a result of this contention, there are no packet reception guarantees and significant bandwidth can be lost. This contention can have a strong impact on the performance together with other kinds of interference sources, e.g., ambient noise. As a result, WSN’s connectivity tends to have a very dynamic nature. In this paper, we devise DecTDMA (Decentralized-TDMA), a fully decentralized medium access controller (MAC) that significantly reduces contention. It is based on a self-stabilizing algorithm for time division multiple access (TDMA). This self-stabilizing TDMA algorithm uses no external assistance or external references, such as wireless access points (WAPs) and globally-synchronized clocks. We present the design and implementation of DecTDMA and report encouraging results: our Cooja simulations and Indriya testbed experiments show stable connectivity and high medium utilization in both single and multi-hop networks. Since DecTDMA has favorable characteristics with respect to connection stability, we show that common link quality estimation (LQE) techniques further improve the operation of DecTDMA in the dynamic environment of low-power wireless networks