Cross-layer caching based optimization for wireless multimedia sensor networks

Traditional transport layer protocols have been designed to perform end-to-end error control transparently to the intermediate nodes (e.g., TCP). However, the resource constraints featured by Wireless Sensor Network (WSN) require a different paradigm where intermediate nodes are able to cache packets and if possible retransmit them on-demand to avoid incurring costly end-to-end retransmissions. Lately, wireless multimedia sensor network (WMSN) is being considered as a new research area whereby WSNs are targeted for the delivery of multimedia traffic. In this paper, we propose a NACK-based repair mechanism coupled with an adaptive MAC layer retransmission scheme in order to improve the performance of the transport protocols. Specifically, our goal is to be able to reduce real-time end-to-end delay while maintaining reliability and energy efficiency in the presence of high channel error rates. Our simulation results show that the ensemble of both mechanisms provides better good-put performance while simultaneously improving energy efficiency. Furthermore, the improved protocol also achieves lower deadline miss ratios which makes it suitable for multimedia transport. While we demonstrate the effectiveness of the mechanisms by incorporating them into the basic Distributed Transport for Sensor Networks (DTSN) protocol, they are generic enough to be applicable to other WSN transport protocols.