Tiny15four: A portable, yet efficient 802.15.4 stack

Hardware heterogeneity is there to stay in the context of sensor motes. Hardware producers compete with different products, and hardware trends lead to new generations of processor and radios every year or so. Software embedded on motes must be portable while leveraging the resources available on a given platform. This problem is particularly acute at the MAC layer. It should be possible to adapt the low-level network stack to the hardware characteristics of a given platform without compromising performance. In this paper, we focus on the design of a a modular, efficient and portable of Tiny15four: a 802.15.4 stack in TinyOS. We report the lessons we learnt. In particular, we experienced the wide gap that exists between standard specification and real implementation. We point out the problems that new versions of the 802.15.4 standard should address. We describe the layers and abstractions that we introduced to achieve our design goals while dealing with the complexity of the standard. Our stack is now implemented on four different platforms. We present here the implementation and experiments performed on an 8-bit platform equipped with a Motorola HCS08 microcontroller and Freescale MC13192 show that Tiny15four allows up to a 30% decrease in memory footprint compared to the native Freescale stack depending on the configuration, with no penalty in terms of execution time.