Cluster-Based Fast Broadcast in Duty-Cycled Wireless Sensor Networks

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This paper proposes a cluster-based broadcast protocol to disseminate delay-sensitive information throughout a wireless sensor network. The protocol considers the use of duty-cycling at the MAC layer, which is essential to reduce energy dissipation. LEACH’s energy-efficiency approach is used for cluster construction. This approach shifts the total burden of energy consumption of a single cluster-head by rotating the cluster-head function among all nodes in the network. It also permits to switch the ordinary (member) nodes in a cluster into the sleep mode whenever they enter inactive TDMA slots. However, LEACH does not consider broadcast messages, and the member nodes scheduling is established as a sequence of TDMA without any common active period. A broadcast message should then be postponed to next TDMA schedule and transmitted a sequence of unicasts, which is inefficient in terms of latency, bandwidth occupation, and power consumption. The proposed protocol adds new common static and dynamic broadcast periods to support and accelerate broadcasting. The dynamic periods are scheduled following the past arrivals of messages, and using a Markov-chain model. To our knowledge, this work is the first that proposes the use of clustering to reduce broadcast latency. Taking advantage of LEACH’s clustering mechanism allow for simultaneous local broadcasts at several clusters in the WSN, and it also ensures scalability with the increase of the network size. This parallelism minimizes the end to-end broadcast latency compared to the current flat-topology solutions, where the end-to-end broadcast latency and the number of messages required to make a broadcast (message-count) are proportional to the network size. The protocol has been simulated, numerically analyzed, and compared with LEACH. The results show clear improvement over LEACH with regard to the latency, at a low energy cost.
Wireless sensor networks, Global broadcast, Duty-cycle MAC, QoS protocols