Reducing Age-of-Information for Computation-Intensive Messages via Packet Replacement

Freshness of data is an important performance metric for real-time applications, which can be measured by age-of-information. For computation-intensive messages, the embedded information is not available until being computed. In this paper, we study the age-of-information for computation-intensive messages, which are firstly transmitted to a mobile edge server, and then processed there to extract the embedded information. The packet generation follows zero-wait policy, by which a new packet is generated when the last one is just delivered to the edge server. The queue in front of the edge server adopts one-packet-buffer replacement policy, meaning that only the latest received packet is preserved. We derive the expression of average age-of-information for exponentially distributed transmission time and computing time. Numerical results show that the average age with packet replacement is smaller than that without packet replacement, especially when transmission rate is close to or greater than computing rate. In addition, the region where edge computing outperforms local computing is characterized.