Dual-Mode Path Selection for In-Band Full-Duplex Multi-Hop CR-IoT Networks

Cognitive radio (CR) and in-band full-duplex (IBFD) are two technologies that are essential in addressing major challenges arising in Internet of Things (IoT). The former addresses frequency spectrum shortage, while the latter aims at satisfying the high data rate requirements. In this paper, we address path selection in multi-hop IoT networks equipped with CR and IBFD capabilities. The main challenge is to jointly select a path and to assign CR channels over the hops of the path in a way that effectively enables utilizing the IBFD capabilities of nodes. The approach followed by most research works in the literature is to formulate the problem as a mathematical program with constraints designed to enable utilizing the IBFD capabilities. Unfortunately, under stringent network conditions, it becomes more likely for the mathematical program to be infeasible; i.e., to fail in satisfying the IBFD constraints, and hence to fail in establishing a path, resulting in a zero end-to-end throughput. In this paper, we propose a novel path selection algorithm employing a mathematical programming formulation that is novel in that it gives higher priority to a solution that satisfies the IBFD constraints. However, in case of infeasibility, the mathematical program is able to detect the hops causing infeasibility, and to provide an alternative lower-priority dual-mode solution that allows half-duplex (HD) transmissions at the detected hops, and IBFD simultaneous transmissions at the remaining hops. Through simulation experiments, we demonstrate significant performance gains achieved by the proposed dual-mode algorithm compared to existing algorithms in the literature.