Slot‐hitting ratio‐based TDMA schedule for hybrid energy‐harvesting wireless sensor networks

Abstract

In the energy-harvesting wireless sensor networks (EH-WSNs) with Time division multiple access (TDMA), it is challenging to assign time slots to the nodes because energy shortage causes some nodes unable to transmit in their time slots, resulting in the inefficiency in slot usage and the increase of the data packet delay. To overcome this problem, the slot assignment in TDMA is required to consider energy packet arrivals, where an energy packet is defined as the amount of energy that suffices for one transmission. In this study, the authors investigate the EH-WSN with hybrid energy sources, in which the nodes harvest energy from the fixed inter-arrival time (FIAT) and the random inter-arrival time (RIAT) energy sources. After deriving the slot-hitting ratios (SHRs) of energy packet arrivals for both FIAT and RIAT energy sources, they propose the SHR-based TDMA (SHR-TDMA) scheme. Then, they derive the delay arising from the awaiting slot (DAFAS) and formulate the DAFAS minimisation problem for the SHR-TDMA. Solution to the DAFAS minimisation problem makes the slots optimally assigned according to the characteristics of the energy packet arrivals at the nodes. The simulation results show that the SHR-TDMA outperforms the existing TDMA schemes in terms of DAFAS.