RT-SENMOS: Reliable transport for sensor networks with mobile sinks

Gathering information efficiently from a, possibly fragmented, sensor network presents a serious problem in disaster recovery applications. Unless a transmission control mechanism exists, a sink can be flooded with information sent by sensors, or sensor transmissions may be lost on their way to the sink. Consequently, there is a necessity for a reliable protocol that automatically and speedily adapts to losses, congestion and network changes due to sink mobility. This paper describes RT-SENMOS, a reliable transport protocol for controlling sensor transmissions based on sink-assigned rates. The sink decides how to share the available bandwidth among the sensors and also determines the reliability to be achieved in each case. Our protocol operates on top of UDP/IP, therefore it can be directly integrated into a disaster recovery application that will set its parameters depending on the situation. Moreover, as it is fully sink-controlled, it enables the use of simple and inexpensive fixed sensors, which offload all protocol intelligence to a more expensive but reusable mobile sink. We present the design of the protocol, comparing it with similar approaches, and evaluate its performance using a real implementation.