Effective retransmission scheme for supporting Communication Reliability in sensor networks

Wireless sensor networks may be utilized for various application areas such as health, military, home, and so on. In the wireless sensor networks, data transmission typically relies on multi-hop communication with high packet loss rates on wireless links so that reliable end-to-end data transmission is desirable. Recently, in order to achieve desired Communication Reliability (CR) levels of the various sensor network applications, a flexible loss recovery mechanism, called Active Caching (AC) is proposed. With respect to a desired CR of an application, when the packet delivery rate during multi-hop transmission from a source to an intermediate node decreases below the CR, AC retransmits lost packets from the source to the intermediate node so that the intermediate node has all data packets just like the source node. Then, during the data transmission from the intermediate node to the destination, if the packet delivery rate at another intermediate node falls below the CR, the new intermediate node recovers the lost packets from the previous intermediate node, not from the source node. Namely, AC flexibly caches all data packets at some intermediate nodes on the routing path in order to achieve the CR. However, AC does not consider the loss rate of each wireless link on the multi-hop routing path in terms of the loss recovery. Since the lost packets are requested and retransmitted via the multi-hop routing path, AC may cause a lot of retransmissions of the lost packets and thus increasing the number of totally transmitted packets. Therefore, we propose a strategy to minimize the number of totally transmitted packets when all data packets from a source are delivered to a destination with a desired CR. In order to minimize the number of totally transmitted packets, the strategy allocates an optimized one-hop packet transmission rate per each wireless link calculated by geometric programming.