Reduction Scheme of SS for D2D Relay-Path Selection to Achieve Guaranteed Throughput for 5G systems

Abstract

In the fifth generation (5G) systems, millimeter wave (mmW) small cells are deployed in order to increase the system capacity. In order to extend the limited coverage of the mmW small cells, network-assisted relay involving device-to-device (D2D) communication is one of the key promising techniques. However, in the crowded area, which is a typical deployment scenario of 5G systems, conventional relay-path selection schemes are not applicable due to intense collisions of D2D synchronization signals (SSs). In addition, when selecting the relay-path, conventional schemes do not consider the backhaul quality to connect the Internet, which is necessary to guarantee end-to-end throughput for some Guaranteed Bit Rate (GBR) type services like conversational video. To solve these problems, the proposed scheme reduces the number of candidate relay users transmitting D2D SSs by applying several constraints such as requested throughput to exclude the relay users unable to satisfy the constraint. As an example of simulation results, it is observed that the proposed scheme reduces the number of D2D SSs by 96%, comparing with conventional schemes, in the case that a requested throughput from a remote user is set to 13.6 Mbps.