COPE: Improving Energy Efficiency With Coded Preambles in Low-Power Sensor Networks

Energy efficiency is one of the most important factors that affect the applicability of wireless sensor networks (WSNs) in many practical scenarios. Many low-power media access control (MAC) protocols have been proposed in the past decade to improve the energy efficiency of sensor nodes. In these low-power MAC protocols, preambles are widely used to wake up the receivers asynchronizely. However, the data delivery potential of these preambles has not been exploited. In this paper, we propose a coded preamble (COPE), which exploits the data delivery potential of preambles by encoding the preambles by network coding. COPE has two salient features. First, a passive receiver set selection scheme enables nodes to decide whether to receive the overheard preamble packets, without introducing extra communication overhead. Second, COPE supports multiple routing primitives, such as unicast and broadcast, making it be a versatile 2.5 layer between the low-power link layer (layer 2) and the network layer (layer 3). We analyze COPE by a novel analytical model. Results show that COPE is able to improve the energy efficiency of both unicast and broadcast significantly. We also implement COPE in TinyOS/TelosB platform and evaluate its energy efficiency. Results show that COPE significantly reduces the radio-on-time in practical network settings.