A D2D Group Communication Scheme Using Bidirectional and InCremental A-Star Search to Configure Paths

The Device-to-Device (D2D) communication introduced in 3GPP's Release 12 is a promising option for the accommodation of increasing traffic demand and the alleviation of core networks' loading. The D2D communication mode prevails in scenarios where mobile users in proximity form a communication group sharing the same interest in digital content. A user can download intended content from peers in the same communication group rather than from the Internet via the base station. This article addresses the routing issue within D2D communication groups. It is, in effect, a path selection problem. We define a utility function considering both delay and throughput. The path selection problem can be formulated as an NP-hard optimization problem. A Bidirectional and InCremental A-star (BICA*) algorithm incorporating the concept of bidirectional search and lifelong planning is developed to tackle the NP-hard optimization problem. Simulations reveal that the proposed approach outperforms existing ones in terms of less delay, higher throughput, and higher satisfaction ratio. The Greedy approach, Two-Stage Relay Selection (TSRS), and the standard A* algorithm were included in the comparative study. The throughput improvements of the proposed scheme are up to 23% and 46.5% compared to TSRS and Greedy, respectively. The proposed scheme possesses the lowest delay and the highest satisfaction rate, among others. With less computational time, the proposed BICA* is more responsive than the standard A* in dynamic environments.