TSTP MAC: A Foundation for the Trustful Space-Time Protocol
Davi Resner, Antônio Augusto Fröhlich · 2016
The Trustful Space-Time Protocol (TSTP) is an application-oriented protocol designed to resource-efficiently deliver authenticated, encrypted, timed, georeferenced, SI-compliant data communication support to IoT devices interacting with an IoT gateway, effectively defining a new API and paradigm for programming WSNs and the IoT. In this work, we describe TSTP's MAC in detail and show how it is a fundamental part of TSTP's design, orchestrating the interaction between several integrated components across the network. TSTP MAC is derived from RB-MAC, handling collision avoidance, duty cycling and greedy, fully-reactive geographic routing without any exchange of control messages, enabling receivers to achieve ultra-low duty cycles (e.g. 0.5% for 265ms per-hop delay), but taking the toll on senders, which must occupy the channel with a relatively long packetized preamble before each transmission. We also show how TSTP MAC itself can leverage clock synchronization it makes possible to TSTP to make senders only transmit critical portions of the preamble by predicting when there will possibly be receivers awake. We show that this optimization can achieve a 70% reduction in preamble transmission even in a non-ideal case, while not introducing any control messages and not affecting receiver duty cycle.