System Support for Cross-Layering in Sensor Network Stack

Wireless Sensor Networks are deployed in demanding environments, where application requirements as well as network conditions may change dynamically. Thus the protocol stack in each node of the sensor network has to be able to adapt to these changing conditions. Historically, protocol stacks have been designed with strict layering and strong interface between the layers leading to a robust design. However, cross-layer information sharing could help the protocol modules to make informed decisions and adapt to changing environmental conditions. There have been ad hoc approaches to facilitating cross-layer cooperation for adaptability. However, there has been no concerted effort at providing a uniform framework for cross-layer adaptability that preserves the modularity of a conventional protocol stack. This paper presents a novel service, information exchange service (IES), as a framework for cross-module information exchange. IES is a centrally controlled bulletin-board where different modules can post available data, or request for useful information, and get notified when the information becomes available. IES is integrated into the proposed SensorStack architecture that preserves the benefits of layering while facilitating adaptability. IES has been implemented in TinyOS and Linux, to show both the feasibility of the design as well as demonstrate the utility of cross-layering to increase application longevity.