Evaluating the Impact of User Behavior on D2D Communications in Millimeter-Wave Small Cells

Abstract

Abstract-Small cells in millimeter-wave (mmWave) band are able to provide multi-gigabit access data rates, and have emerged as a cost-efficient solution to offer interference-free deviceto-device (D2D) communications. In order to improve system performance and enhance user experience, direct transmissions between devices should be scheduled properly. We first propose a transmission scheduling scheme for radio access of small cells in mmWave band, termed directional D2D medium access control (D3MAC), whereby a path selection criterion is designed to enable D2D transmissions. Through extensive simulations, we demonstrate that D3MAC achieves near-optimal performance, and it outperforms other schemes significantly in terms of delay and throughput. Based on this near-optimal scheme, we then evaluate the impact of user behavior, including traffic mode and traffic load as well as user density, denseness and mobility, on the performance of D2D communications in mmWave small cells. Our study reveals that the performance of D2D communications is improved as the user density and denseness increase, but this effect is only obvious under heavy traffic loads. Furthermore, user mobility is shown to be another important factor that influences the performance of D2D communications in a complicated way. System performance is first improved as the average user speed increases from static, but performance is degraded significantly when the user speed becomes high.

A New Centralized Access Control Scheme for D2D-Enabled mmWave Networks

“…• By simulation, we benchmark our approach against the D3MAC scheme [16]. The comparative analysis shows that our control scheme outperforms the reference scheme in terms of throughput, end-to-end delay and fairness in any simulated traffic condition.…”

“…Unlike the approaches analyzed above, the authors of [6] and [13]- [16] adopt a variable-length frame structure, which depends on the user demands. The frame structure is shown in Fig.…”

“…The basic strategy adopted in their scheduling algorithm is to deliver all packets in a frame time, whether delivery occurs directly or via a multi-hop path. Gao et al [16] propose an improved D2DMAC scheme, termed directional D2D medium access control (D3MAC). Compared to the D2DMAC scheme, Gao et al [16] introduce a contention graph in order to depict the contention relationship between flows.…”

“…Gao et al [16] propose an improved D2DMAC scheme, termed directional D2D medium access control (D3MAC). Compared to the D2DMAC scheme, Gao et al [16] introduce a contention graph in order to depict the contention relationship between flows. It is constructed in the way that two vertices are connected with an edge only if the maximum interference between them is greater than or equal to a fixed threshold value.…”

“…1 On the basis of the described scenario and the adopted architectural solution, in addition to the interference between D2D communications, the interference between mmWave access and backhaul network arises. So, in order to efficiently manage these interferences, as in [16], we choose a centralized control approach, considering both radio access and backhaul networks jointly. More specifically, we assume a local Central Controller (CC), inside an AP, which is the one which reduces the average one-way latency between each pair of APs.…”