On the Age of Information in CR-NOMA Assisted Status Updating Systems with Random Arrivals

This paper aims to study the role of cognitive radio inspired non-orthogonal multiple access (CR-NOMA) in improving information freshness of status updating systems with random arrivals. Particularly, a time slotted multiuser scenario is considered, where each user transmits its status update to a receiver. Each user is allocated with a time slot. In CR-NOMA, each user can transmit signal as a primary user by using its own time slot, besides, it can also transmit signal as a secondary user by sharing the time slot of another user. Hence, more transmission opportunities are provided by CR-NOMA compared to conventional time division multiple access (TDMA) based schemes. In this paper, age of information (AoI) is utilized as the performance metric. For comparison purpose, exact expressions for the average AoIs achieved by CR-NOMA and benchmark TDMA are obtained. Numerical results are provided to validate the accuracy of the analytical results and also demonstrate the superior performance of CR-NOMA on reducing AoI. It is shown that the AoI can be significantly reduced by CR-NOMA compared to TDMA.