Age of transmission-optimal scheduling for state update of multi-antenna cellular Internet of Things

Abstract

Timely information updates are critical for real-time monitoring and control applications in the Internet of Things (IoT). In this paper, we consider a multi-antenna cellular IoT for state update where a base station (BS) collects information from randomly distributed IoT nodes through time-varying channel. Specifically, multiple IoT nodes are allowed to transmit their state update simultaneously in a spatial multiplex manner. Inspired by age of information (AoI), we introduce a novel concept of age of transmission (AoT) for the sceneries in which BS cannot obtain the generation time of the packets waiting to be transmitted. The deadline-constrained AoT-optimal scheduling problem is formulated as a restless multi-armed bandit (RMAB) problem. Firstly, we prove the indexability of the scheduling problem and derive the closed-form of the Whittle index. Then, the interference graph and complementary graph are constructed to illustrate the interference between two nodes. The complete subgraphs are detected in the complementary graph to avoid inter-node interference. Next, an AoT-optimal scheduling strategy based on the Whittle index and complete subgraph detection is proposed. Finally, numerous simulations are conducted to verify the performance of the proposed strategy.