CONTENTION RESOLUTION MECHANISM FOR RECEIVER-DRIVEN TDMA-BASED WIRELESS SENSOR NETWORKS

TDMA-based protocols that have been proposed for wireless sensor networks (WSNs) use two opposite strategies of assigning slots to nodes. The transmitted-driven slot assignment schemes, which assign slots to nodes for message transmission, eliminate collisions of data messages, but waste energy due to message overhearing. The receiver-driven schemes, which assign slots to nodes for message reception, eliminate message overhearing, but the neighbors of slot owners have to contend for the medium. The existing proposals of the receiver-driven TDMA protocols employ CSMA-based contention resolution mechanisms, which suffer from both hidden- and exposed-terminal problem, thus limiting the applicability of the protocol to low traffic load conditions. In this paper, we propose a contention resolution mechanism, named TONE, specifically designed for receiver-driven TDMA protocols, which alleviates both the hidden- and exposed-terminal problem, given that a reception slot is not reused within a 2-hop neighborhood. TONE resolves contentions in successive elimination rounds by using a two-phase tone-based signaling mechanism in every round. We also propose a group splitting algorithm, which governs the elimination process in the manner that minimizes the number of tone transmissions, thereby improving the energy-efficiency. Our analysis, verified by simulation results, demonstrates that TONE outperforms the CSMA-based contention resolution mechanism and it can greatly improve the performance of receiver-driven TDMA-based WSNs under heavy traffic load. Also, our simulations show that the receiver-driven TDMA protocol with TONE outperforms transmitter-driven TDMA protocol in energy-efficiency, although with a limited drop in data throughput. Key words: wireless sensor network, MAC protocols, TDMA protocols, contention resolution mechanis