Age of information in wireless powered IoT networks: NOMA vs. TDMA

In this paper we consider a wireless IoT network with energy harvesting sensors and finite battery capacity which obtain their energy from a wireless power transmitter and communicates with a fusion center. We study a specific system model in which one of the sensors with higher battery capacity performs as a central node and obtains the main data from the environment while the other sensors observe the variations of data. Since, fusion center needs fresh data in real time applications and old useless data would be discarded, thus, the Age of Information (AoI) can be considered as one of the major parameters for such networks. In the present paper, we proposes a new protocol based on NOMA and we obtain a closed-form equation for the age of information for whole network. Then, we optimize the age of information on power schedule parameter. As well, the age of whole network is calculated for the same network under TDMA protocol and is optimized on time fraction parameter. Finally, the numerical results are obtained for several parameters and the optimized parameters are applied to compare the age under both protocols. The results show that using NOMA will improve AoI performance compared to TDMA scheme.