No abstract

In the fifth generation (5G) era, dense deployment of small cells and full-duplex (FD) technology applications are two key features of millimeter-wave (mmWave) wireless communication systems, which offer the opportunity to meet the explosive growth of data service requirements. It is the beamforming and advances in analog as well as digital self-interference (SI) cancellation schemes that improve the network capacity in mmWave wireless backhaul networks. To achieve power saving and further network performance optimization, we propose a FD concurrent transmission mechanism employed in a mmWave backhaul network. Contention graph is constructed in consideration of multiuser interference (MUI), SI, and FD transmission constraints. Then flow-grouping and power control algorithms are proposed based on the contention graph. We evaluate the performance of the proposed algorithm in terms of energy consumption, achievable network throughput, and energy efficiency. The impact of the interference threshold on the system performance is also investigated when the distribution of base stations (BSs), traffic loads, and maximum transmission powers change. Simulation results illustrate that with proper SI cancellation and interference threshold, the proposed concurrent mechanism outperforms time-division multiple access (TDMA), half-duplex (HD) concurrent transmission, and FD concurrent transmission without power control. INDEX TERMS Millimeter-wave, wireless backhaul networks, contention graph, full-duplex, concurrent transmission.

To deal with the explosive growth of mobile traffic, millimeter-wave (mmWave) communications with abundant bandwidth resources have been applied to vehicular networks. As mmWave signal is sensitive to blockage, we introduce the unmanned aerial vehicle (UAV)-aided two-way relaying system for vehicular connection enhancement and coverage expansion. How to improve transmission efficiency and to reduce latency time in such a dynamic scenario is a challenging problem. In this paper, we formulate the joint optimization problem of relay selection and transmission scheduling, aiming to reduce transmission time while meeting the throughput requirements. To solve this problem, two schemes are proposed. The first one is the random relay selection with concurrent scheduling (RCS), a lowcomplexity algorithm implemented in two steps. The second one is the joint relay selection with dynamic scheduling (JRDS), which fully avoids relay contentions and exploits potential concurrent ability, to obtain further performance enhancement over RCS. Through extensive simulations under different environments with various flow numbers and vehicle speeds, we demonstrate that both RCS and JRDS schemes outperform the existing schemes significantly in terms of transmission time and network throughput. We also analyze the impact of threshold selection on achievable performance.

In heterogeneous networks (HetNet) comprising high power Macro cells and low power small cells, cross-tier interference limits overall capacity with universal frequency reuse. Conventional fractional power control scheme can not effectively deal with interference between Macro cell and small cells. In this paper, we proposed a new uplink power control scheme,which sets the UL SINR target by considering the interference generated to neighboring cells. Furthermore, interference over thermal (IoT) status from neighboring cells is used to adaptively adjust the SINR target in order to avoid snow avalanche effects. Simulation results show that the proposed scheme outperforms traditional fractional power control scheme in terms of both edge performance and average performance.

An effective outage evaluation approach of asymmetric two-way amplify-and-forward relaying is presented. The proposed approach, characterised by generality, can be applicable to various realistic fading channels. The analytical and simulation results in Nakagamim fading demonstrate the accuracy of the approach.