One Stone Two Birds: A Joint Thing and Relay Selection for Diverse IoT Networks

For a diverse many-to-many-to-one (MMO) Internet of things (IoT) network, it is essential and significant to ensure the access fairness of things with limited cost of performance, i.e., each thing (denoted by sensor) has an identical probability to upload its information to support the intelligent decision making. Therefore, this paper investigates, how to balance the diversity gain and fairness issue of MMO IoT networks by designing joint thing and relay selection criteria (TRSCs). Based on cumulative distribution functions, a fairness optimal TRSC (FO-TRSC) and a fairness suboptimal TRSC (FSO-TRSC) are proposed, efficiently separating the joint selection process into two independent steps. A low-complexity distributed implementation method is presented, which has reduced the implementation complexity to O(1). A rigorous mathematical analysis for the outage probability is given and closed-form expressions are obtained. It has been shown that FO-TRSC can achieve the strict sensor fairness at the cost of relatively big performance loss. On the contrary, FO-TRSC can obtain the same diversity order as the conventional outage optimal TRSC while guaranteeing the approximate sensor fairness. As a result, the two birds are catch: diversity gain and fairness. Simulation results highlight the effectiveness of our criteria and verify our analytical results.