A Strategy Based on Cooperative Transmission for Minimizing Delivery Delay in WSN

To achieve the purpose of energy conservation, various sleep scheduling approaches, such as duty cycle, are applied in wireless sensor networks (WSN). However, the duty-cycle mechanism results in data delivery latency, which is critical to monitor applications. To minimize the delay caused by sleeping nodes in the transmission path, we propose to “hop over†the sleeping nodes based on the range extension of cooperative transmission (CT). The transmission delay models for the random duty-cycled WSN and optimized fixed duty-cycled WSN under cooperative operation are formulated, and an algorithm named (delay-tolerant cooperative transmission DTCT) is presented for the selection of transmission modes to avoid waiting for the sleeping nodes to wake up. The energy consumption model under direct transmission (DT) and CT mode is also presented. Theoretical analysis shows that sleep latency can be greatly reduced in the cooperative scheme, and it is validated by simulations that it outperforms the traditional store-and-forward (DT) mode in delivery latency. Especially, CT reduces 67% and 14.3% of the transmission delay in random and optimized fixed low duty-cycled WSN, respectively, and DTCT algorithm saves energy by 11.29% in random low duty-cycled WSN.