Hands on IRIS: Lessons learned from implementing a cross layer protocol stack for WSNs

This paper describes the challenges behind the implementation of a full cross-layer protocol stack for wireless sensor networks. Our solution, IRIS, integrates interest dissemination and convergecasting, adaptive duty cycle and data fusion. The interest dissemination protocol is used for task assignment and to build and maintain the network topology, while convergecasting implements data gathering at the network sink. Convergecasting heavily exploits cross layering in that MAC and routing operations are performed jointly and relay selection is based on flexible cost functions that take into account information from different layers. We have implemented and tested IRIS on two different testbeds, in a controlled lab scenario and in a building with Wi-Fi interference. The flexibility introduced by the IRIS cross layer approach results in higher robustness and reliability than that of well-known approaches such as BoX-MAC combined with the CTP protocol. IRIS delivers more than 95% of packets while other approaches have packet delivery ratios as low as 87% and are not as scalable with traffic. IRIS is also able to support timely and robust delivery of data with duty cycles as low as 5%.