Delay Outage Probability of Multi-relay Selection for Mobile Relay Edge Computing System

In this paper, we deal with the problem of relay selection in mobile relay edge computing system, where a source node transmits a computation-intensive task to a destination node via the aid of multiple relay nodes. It differs from the traditional relay nodes in the way that each relay node is equipped with an edge computing server with different computing ability, and thus each relay node can execute the received task and forward the computed result to the destination. Accordingly, we define a delay outage probability to evaluate the impact of the relay computing ability on the link communication, and then propose a latency-best relay selection (LBRS) scheme which not only considers the communication capability but also considers the computing ability of relay nodes. The performance of the proposed relay selection scheme with the traditional communication-only relay selection (CORS) and computing-only selection (CPORS) schemes in terms of the delay outage probability and the diversity order are analyzed, compared with other relay selection schemes. The theoretical derivation points out that the proposed LBRS scheme reduces to the traditional CORS scheme under the high signal-to-noise ratio (SNR) region. We further reveal that the diversity order of both the proposed LBRS and CORS schemes are dependent on the computing ability of relay nodes.