Age of Information for Joint Sensing, Transmission and Computation in Mobile Edge Computing

Peak age of information (PAoI) is an important performance metric for mobile edge computing (MEC) systems to characterize the freshness of information. This paper addresses MEC systems with joint sensing, transmission and computation, where sensors sense and transmit computationally intensive packets to local and edge servers. Three computation scenarios are considered: (1) a local computation scenario in which all computation tasks are handled by the local server, (2) an edge computation scenario in which all computation tasks are handled by the edge server, and (3) a partial computation scenario in which some of the computation tasks are handled at the local server, and the rest is handled by the edge server. Considering the exponential distribution of transmission and computation times and using a first-come-first-served queuing policy, a closed expression for the average PAoI is derived. Numerical simulation results show that a reasonable packet sensing rate can reduce the PAoI of the system. In addition, the PAoI of the system can be reduced by adjusting the server computation rate and offloading ratio, so that the MEC system can achieve better performance.