Beamforming and Interference Cancellation for D2D Communication Assisted by Two-Way Decode-and-Forward Relay Node

This paper investigates the device-to-device(D2D) communication underlaying cellular network assisted by a two-way decode-and-forward relay node. We assume the base station(BS) is equipped with M-antenna and serves its own cellular user while the D2D users communicate via a two-way decode-and-forward relay node. Both beamforming(BF) and interference cancellation(IC) strategies at the BS are considered to improve the performance for the cellular link and D2D link, respectively. We first analyze the received signal-to-interference-plus-noise for the cellular link under BF and IC strategies and then derive the exact closed-form expressions for the cellular link. Asymmetric and symmetric cases are discussed for various locations of each user. Finally, the approximations for high signal-to-noise regime are also presented. Numerical results demonstrate the accuracy of the analytical and asymptotic results.

INTERCARRIER INTERFERENCE ALLEVIATION BEAMFORMING FOR OFDM WITH SPACE DIVERSITY

Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from performance deterioration when the length of Cyclic Prefix (CP) is shorter than the Channel Impulse Response (CIR). The fundamental reason of this impairment is the InterCarrier Interference (ICI) and Inter- Symbol Interference (ISI) introduced by the excessive multipath delay. Specifically, Multiple Input Multiple Output (MIMO) beamforming is helpful in cancelling such interference since it can spatially suppress some of the multipath. In this paper, we propose an ICI eliminating beamforming scheme employing a per-tone processing approach, thus with moderate computational complexity. The ISI is removed by using a simple decision feedback equalizer, while the optimal steering and combining vectors are then derived to maximize the Signal to Interference plus Noise Ratio (SINR). This method not only achieves the beamforming benefit, but also significantly alleviates the ICI. Simulation results show that the proposed algorithm can effectively reduce the system Symbol Error Rate (SER), per- mitting good performance for multipath delay profiles that would break conventional links.

Admission control based on beamforming and interference alignment for D2D communication underlaying cellular networks

An admission control algorithm based on beamforming and interference alignment for device-to-device( D2D) communication underlaying cellular networks is proposed. First, some portion of D2D pairs that are the farthest away from the base station( BS) is selected to perform joint zero-forcing beamforming together with the cellular user equipments( UEs) and is admitted to the cellular network. The interference of the BS transmitting signal to the cellular UEs and the portion of D2D pair is eliminated completely at the same time. Secondly,based on the idea of interference alignment,the definition of channel parallelism is given. The channel parallelism of the remaining D2D pairs which are not involved in joint zero-forcing beamforming is computed by using the channel state information from the BS to the D2D devices. The higher the channel parallelism,the less interference the D2D pair suffers from the BS. Finally,in a descending order of channel parallelism,the remaining D2D pairs are reviewed in succession to determine admission to the cellular network. The algorithm stops when the admission of a D2D pair decreases the system sum rate. Simulation results show that the proposed algorithm can effectively reduce the interference of the BS transmitting signal for D2D pairs and significantly improve system capacity. Furthermore, D2D communication is more applicable to short-range links.

Self-Interference Elimination by Physical Feedback Channel in CCFD for 3-D Beamforming Communication

The 3-D beamforming scheme has elite as evolving interest because of its efficiency to empower assorted techniques such as vertical and horizontal domains and emanation beamforming according to subscriber's provisions. Usually, 3-D beamforming communication is set up on FDD/TDD approach those effects on the performance of spectrum and energy efficiency. Co-frequency and CoTime Full Duplex(CCFD) is an effective solution to improve the spectrum and energy efficiency by transmitting and receiving simultaneously in frequency and time domain. While, CCFD communication often face the self-interference issue when communication occurs, simultaneously. Consequently, in this paper a self-interference elimination by physical feedback channel in CCFD for 3-D Beamforming communication scheme is proposed to improve the over-all system performance in terms of energy and spectrum efficiency. The simulation and analytical outcomes demonstrated that the proposed system is superior than the traditional one.

On Broadband Adaptive Beamforming in the Presence of Correlated Interferences

A novel approach of unitarily interpolated array MVDR （UIA-MVDR） is proposed, aiming at avoiding the signal cancellation caused by broadband signal-correlated interferences. UIA-MVDR belongs to the classic approaches of spectral averaging. However, it is distinguished from the conventional interpolated array MVDR （IA-MVDR） by two points： 1） It imposes a unitary constraint on the transform matrices. 2） It only optimizes the worst-case performance of array manifold approximation. As a result, the restriction on the order of Bessel function expansion is released, so that very accurate approximation can be achieved even in the case of small or middle arrays. Compared with many related approaches, UIA-MVDR destroys the correlation more completely and then achieves better performance. Its excellent performance in both correlated and uncorrelated broadband interferences suppression is confirmed via a n umber of numerical examples.

Combination of interference alignment and beamforming in cellular networks

In this paper, we propose two joint transmit-receive iterative algorithms without the cooperation between different base stations based on the idea of interference alignment (IA) to improve the throughput of relay backhaul links in cellular networks for the case of imperfect channel knowledge,which can be implemented with small changes to existing TD-LTE standards. Unlike the previous interference alignment algorithms' only reducing the sum interference to the other receivers at the transmitter or the sum received Multi-user interference (MUI) at the receiver, our algorithm shapes the transmission of each data stream at transmitters in order not only to minimize interference to the other users, but also to minimize the interference between different streams objected to the same user, suppressing the MUI and Multi-stream interference (MSI) at receivers. The proposed algorithm I is to maximize the SINR at receivers. But the complexity is relatively high. Algorithm II only needs linear operations and sacrifices a little performance for much lower complexity compared to the Maximize SINR iterative algorithm which needs the inversion operation of matrix. It is also proved that the algorithm converges monotonically. The simulation results show that the techniques have considerable performance gain compared with the previous algorithms. Further research about power allocation is also discussed.

Estimation of co-channel interference between cities caused by ducting and turbulence

With the rapid development of the fifth-generation(5 G)mobile communication technology,the application of each frequency band has reached the extreme,causing mutual interference between different modules.Hence,there is a requirement for detecting filtering and preventing interference.In the troposphere,over-the-horizon propagation occurs in atmospheric ducts and turbulent media.The effects of both ducting and turbulence can increase the probability of occurrence of long-distance co-channel interference(CCI),in turn,severely affecting the key performance indicators such as system access,handover and drop.In the 5 G era,to ensure communication channels and information security,CCI must be reduced.This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries.It combines Hitney’s radio physical optical model and Wagner’s nonuniform turbulent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct.The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments.Finally,as a specific case,the topographical boundaries between several cities in the East China Plain were considered,and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments.The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.

TDOA estimation of dual-satellites interference localization based on blind separation

The time difference of arrival(TDOA)estimation plays a crucial role in the accurate localization of the satellite interference source.In the dual-satellites interference source localization system,the target signal from the adjacent satellite is likely to be interfered by the normal communication signal with the same frequency.Therefore,the signal to noise ratio(SNR)of the target signal would become too low,and the TDOA estimation through cross-correlation processing would be unreliable or even unattainable.This paper proposes a technique based on blind separation to solve the co-channel interference problem,where separation of the mixed signal can be carried out by the particle filter(PF)algorithm.The experimental results show that the proposed method could achieve more accurate TDOA estimation.The measured data obtained by using the software radio platform at 915 MHz and 2 GHz respectively verify the effectiveness of the proposed method.

Cluster-Based Interference-Free MAC Protocol with Load Aware in Software Defined VANET

In order to reduce the interference,a novel,cluster-based medium access control(MAC)protocol with load aware for VANETs is proposed in this paper.First,all vehicles on roads are grouped into stable clusters in the light of their direction,number of neighbors,link reliability,and traffic load.By utilizing the advantages of centralized control in software defined VANETs(SDVN),cluster stability can be maintained in real-time.Second,a contention-free MAC mechanism composed of inter-cluster multi-channel allocation and intra-cluster dynamic TDMA frame allocation is proposed to prevent co-channel interference and hidden terminal interference.Simulation results show that the proposed protocol outperforms some existing protocols in cluster stability,delivery ratio,throughput and delay performance.

Interference Coordination for FD-MIMO Cellular Network with D2D Communications Underlaying

In this paper, we investigate the interference coordination for downlink full-dimension multiple-input multiple-output(FD-MIMO) systems with device-to-device(D2 D) communications underlaying. With three-dimensional(3 D) beamforming transmission applied for cellular users(CUEs), an approximation of the interference to signal ratio for CUEs is derived, and a coordination strategy is proposed to mitigate the interference from D2 D pairs to CUEs. Based on the lower bound of the interference to signal ratio for D2 D pairs, we propose coordination strategies for D2 D pairs to mitigate the interference caused by base station(BS) and the interference between D2 D pairs. The proposed strategies require only some statistical channel state information(CSI) of each user and the reduced-dimensional effective CSI of a few CUEs and D2 D pairs. Simulation results show that the proposed coordination strategy performs well in terms of achieving good tradeoff between the achievable rate of CUEs and D2 D pairs.

Codebook selected beamforming algorithm for multiuser MIMO systems

For reducing the inter-user interference in multi-user multiple-input multiple-output（MU-MIMO） wireless communication systems,e.g.,MIMO-orthogonal frequency division multiplexing（MIMO-OFDM） systems,it is often desirable to the complex preprocessing at the transmitter.This paper proposes a multi-user beamforming algorithm with sub-codebook selection.Based on the minimal leakage criterion,the codebook selection,limited feed-forward and minimum mean square error（MMSE） detection are combined in the proposed algorithm.This avoids the complex channel matrix decomposition and inversion.Consequently,the computational complexity at the transmitter is significantly reduced.Simulation results show that the proposed algorithm performs better than existing beamforming algorithms.

Component Carrier Selection and Beamforming on Carrier Aggregated Channels in Heterogeneous Networks

In this paper, component carrier selection and beamforming on carrier aggregated channels in Heterogeneous Networks are proposed. The scheme jointly selects the component carrier and precoding (i.e. beamforming) vectors with the cooperation of the other cells to deal with the interference between Macro cell and Pico cell. The component carrier selection and beamforming is achieved by optimizing the multi-cell downlink throughput. This optimization results in shutting down a subset of the component carrier in order to allow for a perfect interference removal at the receive side in the dense low power node deployment scenario. Additionally, algorithm based on Branch and Bound Method is used to reduce the search complexity of the algorithm. Simulation results show that the proposed scheme can achieve high cell-average and cell-edge throughput for the Pico cell in the Heterogeneous Networks.

Coverage probability of cellular networks using interference alignment under imperfect CSI

Interference alignment （IA） is well understood to approach the capacity of interference channels, and believed to be crucial in cellular networks in which the ability to control and exploit interference is key. However, the achievable performance of IA in cellular networks depends on the quality of channel state information （CSI） and how effective IA is in practical settings is not known. This paper studies the use of IA to mitigate inter-cell interference of cellular networks under imperfect CSI conditions. Our analysis is based on stochastic geometry where the structure of the base station （BS） locations is considered by a Poisson point process （PPP）. Our main contribution is the coverage probability of the network and simulation results confirm the accuracy.

Distributed Multi-Cell Multi-User MISO Downlink Beamforming via Deep Reinforcement Learning

The sum rate maximization beamforming problem for a multi-cell multi-user multiple-input single-output interference channel(MISO-IC)system is considered.Conventionally,the centralized and distributed beamforming solutions to the MISO-IC system have high computational complexity and bear a heavy burden of channel state information exchange between base stations(BSs),which becomes even much worse in a large-scale antenna system.To address this,we propose a distributed deep reinforcement learning(DRL)based approach with lim⁃ited information exchange.Specifically,the original beamforming problem is decomposed of the problems of beam direction design and power allocation and the costs of information exchange between BSs are significantly reduced.In particular,each BS is provided with an inde⁃pendent deep deterministic policy gradient network that can learn to choose the beam direction scheme and simultaneously allocate power to users.Simulation results illustrate that the proposed DRL-based approach has comparable sum rate performance with much less information exchange over the conventional distributed beamforming solutions.

LOW-COMPLEXITY JOINT BEAMFORMING AND POWER ALLOCA-TION FOR SINR BALANCING IN COGNITIVE RADIO NETWORKS

We consider the Signal-to-Interference plus Noise Ratio(SINR) balancing problem in-volving joint beamfoming and power allocation in the Cognitive Radio(CR) network,wherein the Single-Input Multi-Output Multiple Access Channels(SIMO-MAC) are assumed.Subject to two sets of constraints:the interference temperature constraints of Primary Users(PUs) and the peak power constraints of Cognitive Users(CUs),a low-complexity joint beamforming and power allocation algo-rithm called Semi-Decoupled Multi-Constraint Power Allocation with Constraints Preselection(SDMCPA-CP) for SINR balancing is proposed.Compared with the existing algorithm,the proposed SDMCPA-CP can reduce the number of matrix inversions and matrix eigen decompositions signifi-cantly,especially when large numbers of PUs and CUs are active,while still providing the optimal balanced SINR level for all the CUs.

Performance Analysis on Output SINR of Robust Two-Stage Beamforming

In this paper, we present a theoretical analysis of the output signal-to-interference-plus-noise ratio (SINR) for eigen-space beamformers so as to investigate the performance degradation caused by large pointing errors. For the sake of reducing such performance loss, a robust scheme, which consists of two cascaded signal processors, is proposed for adaptive beamformers. In the first stage, an algorithm possessing time efficiency is developed to adjust the direc-tion-of-arrival (DOA) estimate of the desired source. Based the achieved DOA estimate, the second stage provides an eigenspace beamformer combined with the spatial derivative constraints (SDC) to further mitigate the cancellation of the desired signal. Analysis and numerical results have been conducted to verify that the proposed scheme yields a better robustness against pointing errors than the conventional approaches.

一种基于变参考电平的零点凹口双重可控方向图综合改进方法

为了解决基于变参考电平的自适应波束形成方法无法同时控制方向图零点和凹口的问题,研究了基于最大信噪比准则的任意阵列方向图综合方法,重点对主瓣宽度固定条件下能够实现最低等副瓣电平的方向图综合方法进行了理论分析,并对前人提出的可变参考电平参量进行了重新定义,新定义的变参考电平能够在波束主瓣宽度固定的前提下,同时产生等副瓣电平、可控凹口宽度和深度和可控零点深度的抗干扰波束,并通过计算机仿真验证了算法的有效性.该方法对于提升相控阵雷达对抗杂波和干扰性能具有较高的应用价值.

一种基于SIC-CDM的低复杂度混合波束赋形方案

为了平衡毫米波大规模多输入多输出系统的性能和硬件开销,降低系统功耗,以频谱效率为优化目标,在部分连接结构下提出了一种收发端联合设计的低复杂度混合波束赋形方案。首先,基于连续干扰消除将原始优化问题转化为多个子阵的速率优化问题;然后,利用坐标下降法完成模拟波束赋形矩阵设计;最后,引入等效信道矩阵大幅降低矩阵维度,再对其进行奇异值分解获得数字波束赋形矩阵。仿真结果表明,与其他算法相比,所提算法在系统功耗降低的同时保持了较优的性能,且性能逼近部分连接结构的最优方案。

相位感知的水下平台背景宽带噪声干扰抑制

针对水下航行器等平台存在宽带背景噪声干扰导致目标检测能力下降问题,提出一种适用于多通道水听器阵列的深度学习宽带背景噪声干扰抑制方法。该方法通过含干扰信号的多通道频域特征级联保留了相位信息,使用深度复数神经网络建立了一个估计纯净目标信号频谱特征的学习模型实现干扰抑制,再利用常规波束形成方法实现目标检测与跟踪。仿真结果表明,在信干比为-15 dB,-20 dB,-25 dB的双目标信号条件下,所提干扰抑制方法可以有效减少近场干扰影响,提高了常规波束形成的检测能力。湖试结果表明,该方法能够自适应地实现平台宽带背景噪声干扰抑制,有效提升目标检测和跟踪性能。

多维阵列张量模型的鲁棒波束成形方法

传统波束成形算法在应对维数较高的多维阵列时,训练快拍数难以满足远大于信号维数这一要求,从而导致波束成形器性能急剧下降。针对这一问题,本文给出了多维阵列输出数据的张量模型,基于多维阵列子维度的可分离性,引入张量波束成形方法,分析了其在训练快拍数需求上具有的优势。然后,基于张量波束成形中子维度干扰协方差矩阵的模型,通过直接估计干扰协方差矩阵实现了一种鲁棒张量波束成形方法。分析表明:该方法可更好地应对非均匀杂波环境以及相干干扰,并得到更高的输出信干噪比,以给出的二维极化敏感阵列为例,所提方法的训练快拍数需求为传统方法的1/3,相干干扰下输出信干噪比提高了约2.5 dB,仿真验证了分析的有效性。