Reducing Age of Extra Data by Free Riding on Coded Transmission in Multiaccess Networks

This paper focuses on the real-time status update in a multiaccess vehicular network, in which multiple vehicles transmit not only the payload data (e.g., monitoring data) but also the extra data (e.g., driving intention) to a road side unit for scheduling vehicles to improve traffic efficiency and safety. A free-ride code is implemented, where the extra data is encoded by a random but fixed generator matrix and is delivered by superposition on the low-density parity-check (LDPC) coded payload data, consuming neither extra bandwidth nor extra transmit power. Considering the time slotted ALOHA random access protocol, we derive the closed-form expression for average age of information (AoI), and evaluate the AoI for both payload data and extra data. Numerical simulations demonstrate that free-ride codes can not only transmit extra data without extra transmit power, but also reduce the average AoI of extra data without affecting the average AoI of payload data.