Batteryless Machine-Type Communications With Average Channel State Information Energy Beamforming

Machine-type communication (MTC) is a key component in 5G and beyond wireless networks, enabling important applications oriented to the industry. In such environments, the limited lifetime of battery-powered solutions becomes a relevant reliability issue. In this paper, we consider a sensor node powered wirelessly by a dedicated multi-antenna power beacon (PB). The harvested energy is directly used by the sensor to power its transceiver and send information to a destination node without storing it in a battery, which would demand non-negligible charging time and potentially compromise the MTC operation. Also, we leverage a packet replication mechanism during information transmission from the sensor to the destination in order to improve the system reliability. We derive the incident power statistics and the outage probability assuming Rician fading channels and only average channel state information at the PB. Then, we define an optimization problem aiming to minimize the energy required by the PB by properly tuning the number of replicated packets and the harvesting time. Results show the existence of an optimal harvesting time as well as an optimal number of replications for a given number of PB antennas, enabling batteryless MTC applications.