Wi-Fi assisted 5G D2D communications in unlicensed spectrum

Abstract

Device-to-device (D2D) communication in the unlicensed spectrum (D2D-U) has been evolved as a promising approach to alleviate the limitation of licensed band spectrum crisis of the fifth generation (5G) cellular network. However, increased Wi-Fi deployment also calls for a need of appropriate resource management to avoid the interference conflicts when D2D users (DUs) operate with the existing Wi-Fi users (WUs) in the same unlicensed spectrum. In this paper, we have proposed an access point (AP) controlled D2D communications in the unlicensed spectrum to accommodate a suitable number of DUs that can opportunistically use the unlicensed frequency spectrum of the existing WUs. We have considered different interfering scenarios in the network and developed a Wi-Fi assisted D2D communication (WADC) model to maintain an amicable coexistence between the admitting DUs and the existing WUs. This is done through an efficient resource allocation with the joint approach of two existing methods known as listen before talk (LBT) and duty-cycle approach. A mathematical formulation of the problem has been presented and a greedy solution has also been developed. The proposed approach admits maximum number of DUs to use the unlicensed spectrum resource of the existing WUs without affecting their performance. Simulation results on different networking parameters show that the proposed approach can offer maximum D2D coverage with appropriate quality of service (QoS). Furthermore, it has also been established that the proposed approach is fairly comparable to the other existing approaches. Finally, a sensitivity analysis of the proposed WADC has been presented to show its robustness for varying input conditions.