It has been widely advocated that software architecture provides an effective set of abstractions for engineering (families of) complex software systems. However, architectural concepts are seldom supported directly at the level of system implementation. In embedded environments in particular, developers are often forced to rely on low-level programming languages. While this is conducive to fine-grain control over the system, it does not lend itself to addressing larger issues such as ensuring architectural integrity or managing an application family. In this paper we describe our experience with fundamentally altering the manner in which a family of embedded applications is designed, analyzed, implemented, deployed, and evolved using explicit architectural constructs. We discuss our strategy, the challenges we faced in the course of our project, the lessons learned in the process, and several open issues that remain unresolved.

In this paper we present a novel sequence-based RF localization algorithm called Ecolocation. Our algorithm determines the location of unknown nodes by examining the ordered sequence of received signal strength (RSS) measurements taken at multiple reference nodes. We employ a constraint-based approach that provides for robust location decoding even in the presence of random RSS fluctuations due to multi-path fading and shadowing. Through extensive systematic simulations, and a representative set of real mote experiments, we show that over a wide range of settings Ecolocation performs better than other state of the art approaches in terms of localization accuracy and precision.