Language support for interoperable messaging in sensor networks

Development of network communication in a homogeneous sensor network environment is straightforward as the nodes can share message layouts simply by letting the compiler lay out messages in an arbitrary fashion and using the same executable code on all nodes. However, this simple approach does not usually work in a heterogeneous sensor network setting because different compilers may generate different message layouts, and different processors often have different basic type representations and alignments. The traditional solutions to this problem is to either require programmers to insert network-byte-order and host-byte-order conversions, or to use a compiler that automatically generates marshalling and unmarshalling routines. Unfortunately, these approaches are in-adequate for sensor networks because they are either error-prone and/or add significant overheads to already resource-constrained sensor motes. Instead, we propose a language extension --- network types --- which supports heterogeneous networking in a simple and efficient way. We have implemented network types in the nesC, the language of the TinyOS sensor network operating system and its applications. We have used network types to supports heterogeneous networking between micaz and telos motes (which have different alignment restrictions). We also show that our implementation introduces a negligible amount of overhead in runtime and code size. Network types have the additional benefit of requiring few changes to existing TinyOS code.