Error and congestion control for wireless sensor networks

Abstract

In the wireless sensors network (WSN) field, a wide variety of sensors produce a heterogeneous traffic mix, targeting diverse applications with different reliability requirements. We focus on emergency response scenarios, where a mobile rescuer moves through a, possibly disconnected, network, trying to talk to diverse sensors. We assume two types of sensors, event sensors triggered by an event and periodic sensors activated at predefined time intervals, as well as two types of transmission, either using the highest bit rate available or using predefined bit rates. Our reliable transport protocol for sensor networks with mobile sinks (RT-SENMOS) takes into account all these parameters and tries to provide the best possible user experience under the current circumstances of the network, using a sink-driven approach where an application-specific sink is combined with generic sensors. RT-SENMOS was implemented and tested over a real network with emulated losses and compared against rate-controlled reliable transport (RCRT), a well-known sink-driven protocol. The results show that RT-SENMOS fully exploits the available bandwidth in all cases, while RCRT only manages to exploit 60% to 90% of it. Furthermore, RT-SENMOS adapts much faster to prevailing network conditions, while its protocol overhead, in terms of control messages exchanged, is much lower than that of RCRT.