高铁基于毫米波的自适应波束分合传输方案

向拥有较宽连续频谱的高频频段扩展带宽成为未来高铁无线通信系统提升容量的有力手段,不过,需要采用大规模天线波束赋形技术克服高频频段路径损耗严重的缺陷。在高铁双车载台方案中,可以通过大规模天线阵列形成双波束传输提高系统容量。在对其传输性能进行分析后发现,双波束传输优化配置与列车的位置有关。基于此,论文提出自适应波束分合传输方案,当列车距离基站较远时,为了避免波束间的严重干扰,双波束合成为一个波束来覆盖两个接收端,实现接收分集,提高接收信号质量;当列车距离基站较近时,分裂成双波束,实现空间复用,提高系统容量及传输可靠性。数值仿真结果表明,所提方案可以适应列车运行位置,提升传输性能。     

LTE-Advanced异构网中载波选择与波束成形联合算法

为解决LTE-Advanced异构网内宏小区及微小区间的相互干扰问题,提出了载波选择与波束成形联合算法.在高密度、多低功率微基站节点的异构网中,通过关闭部分基站的部分载波,并在开启载波的基站天线上进行波束成形,使接收端受到的干扰大幅度降低.另外,基于效用函数的约束,对载波、波束分别计算,使原本二维联合优化问题变成两个一维优化问题,降低了算法复杂度.仿真结果表明该方案增加了异构网中边缘用户及整个系统的吞吐量.     

一种新的基于3D有源天线组网的干扰协调方案

传统2D有源天线仅能进行水平维的波束调整,而3D有源天线能够结合垂直维的波束调整,提升系统的吞吐量.由于3D有源天线组网的干扰情况与2D完全不同,需要研究新的干扰协调方案,本文提出一种基于3D有源天线组网的干扰协调方案,通过相邻基站间交互各自对系统资源的使用信息,使得基站间可协调分配系统资源,降低了系统整体干扰水平.仿真结果表明,提出的方案可有效地抑制小区间干扰,提升边缘用户的性能乃至整个小区的平均吞吐量.     

一种基于自适应资源分配的干扰协调方案

在宏基站和微微基站(Macro-Pico)的异构网络中,资源分配可以有效地抑制基站间的干扰。基于降低用户的干扰和提高系统的吞吐量,提出一种自适应的频率资源分配方案。考虑分配给宏基站的每个资源块,如果距离宏基站较近的微微基站用户所受到的干扰高于最高限,采用不给宏基站分配这个资源块的方法,从而降低其对邻近微微基站用户的干扰,保证微微基站用户一定Qo S(Quality-of-Service)。系统仿真结果表明,与正交频率资源分配方案和共信道频率资源分配方案相比较,所提出的自适应频率资源分配方案降低了干扰和提高了系统的吞吐量。     

基于有限反馈的数据流数自适应SDMA

针对目前绝大部分有限反馈自适应SDMA由于使用固定满波束发送策略而导致在稀疏网络中严重的用户间干扰的问题,该文提出了一种基于有限反馈的数据流数自适应SDMA,该方案能通过自适应地选择并行发送波束的数目来达到有效控制用户间干扰的目的。具体实现如下:通过用户的有限反馈信息,以及信道的二阶统计信息,基站端使用约束最大似然估计的方法估计出使用不同数目发送波束的发送模式所支持的最大和吞吐量,从而自适应地选择最优的发送模式。仿真结果表明:该文提出的方案能在增加很少反馈量的前提下显著改善现有SDMA方案的性能。     

针对非理想定时同步的多模协作多点传输

针对非理想定时同步对协作多点传输的负面影响,提出了多模协作多点传输算法。通过推导协作波束成形模式和联合处理模式在非理想定时同步条件下的平均可达速率,得到模式选择变量和模式选择门限。在多模协作多点传输算法中,用户首先对定时同步误差进行估计,并计算其模式选择变量和模式选择门限。然后用户选择协作多点传输的下行传输模式,并将其选择结果反馈给协作基站。最后,根据各用户的反馈,协作基站以最大化平均可达传输速率为准则,自适应地在协作波束成形模式和联合处理模式之间切换。仿真结果表明多模协作多点传输算法在定时同步误差较小时,采用联合处理模式,以保持空间复用增益,在定时同步误差较大时,采用协作波束成形模式,以避免用户间的额外干扰。因此,在非理想定时同步误差条件下,多模协作多点传输算法比仅采用协作波束成形模式或联合处理模式的传统协作多点传输算法具有更好的性能。     

多点传输系统的联合调度方案

在下行蜂窝网络中,多点传输计划因可以大幅度提高扇区平均吞吐量和小区边缘用户速率而越来越受到关注。传统的独立调度算法中参与多点传输的扇区分别调度各自的用户,这种独立调度算法限制了系统性能的进一步提高。文章提出了一种针对SF-DCHSDPA系统新的联合调度方案,基站间通过交换信息选择适合的传输方案。可更好地调度用户。通过系统级仿真结果可以看出,新提出的联合调度算法可以获得更好的扇区平均吞吐量和边缘用户体验。     

基于多点协作联合传输的超密集组网性能分析

超密集组网的基站高密度特性会带来严重的小区间干扰,多点协作联合传输应用于超密集组网进行干扰管理是目前的研究热点,该文对多点协作联合传输时基站密度对网络性能的影响进行了分析。首先采用随机几何方法推导了3维空间基站与用户距离的概率密度函数,为选取距离用户最近的多个基站联合传输的协作机制提供了基础;然后结合有界双斜率路径损耗模型,进行用户下行链路的干扰建模,进一步推导出用户下行链路覆盖率和网络区域频谱效率的表达式,并分析了协作基站数、基站密度等参数对网络性能的影响。数值仿真表明:协作基站数为2时就可使下行链路覆盖率增加10%,且实现2到3倍的频谱效率的增益,当协作基站数为3时,费效比更优,同时可得到多点协作下的基站密度极限使区域频谱效率最高。该文工作可为下一代移动通信网络的基站部署提供理论支持。     

毫米波通信中的波束管理标准化现状和发展趋势

Massive MIMO是5G系统中实现多千兆吞吐量、提升频谱效率和网络性能最有前景的技术之一。在5G新空口(New Radio,NR)系统中,采用大规模天线阵列的混合波束赋形技术已成为解决高频传播损耗、提升高频通信频谱效率的常见方法。文章根据5G NR标准化进展,对现有波束管理流程进行系统综述,介绍Rel-15和Rel-16版本下波束管理的演进过程,并结合未来5G-Advanced标准演进方向,提出针对UE多面板配置的传输增强方案,基于干扰感知和AI预测的波束管理技术以及多站点协作传输场景下TRP快速切换的波束管理流程。     

基于信道相关统计及有限反馈的多基站协作波束成型

为减少多基站协作波束成形系统中基站间的信息交换量和用户信道信息反馈量,提出一种基站联合利用有限反馈信道参数和信道空间相关矩阵估计信道矢量函数的方法;基于所估计的信道矢量函数,提出一种多基站协作扩展迫零波束成形算法。相比已有的多基站协作波束成形方案,所提算法能在反馈/回程开销和系统性能之间取得更合理的折中,计算仿真验证了所提算法的有效性。     

Optimal Beam Subset and User Selection for Orthogonal Random Beamforming

The throughput performance of orthogonal random beamforming (ORBF) with a finite number of users is limited due to the increasing amount of residual interference. In this letter, we find the optimal beam subset, the optimal user set, and the optimal number of random beams to maximize the sum throughput of the ORBF. The proposed scheme provides the best trade-off between the multiplexing gain and the multiuser interference by the determination of the optimal number of random beams as well as the beam selection diversity gain due to the selection of the optimal beam subset. In addition, two efficient suboptimal schemes are presented to reduce the computational complexity and the feedback overhead of the optimal method.     

Adaptive Beamforming in CR-MIMO System Exploiting Multi-Channel and Eigenmode Diversity

In this paper, a space division multiplexing (SDM) based joint adaptive beamforming downlink transmission scheme for infrastructured cognitive radio multi-input multi-output system is proposed. When spectrum holes exist traditional opportunistic spectrum access is employed. While there is no idle spectrum available, cognitive base station and cognitive user firstly evaluate spatial correlation between cognitive transmission and inter-system interference based on the preprocessed channel information. Incorporated with transmission gain, authorized frequency channel and eigenmode are jointly selected. Then on the premise that no interference is imposed on the primary, cognitive transmission is carried out adopting SDM. The proposed scheme exploits selection diversity of both authorized channel and cognitive eigenmode, thus achieves better spatio-frequency resource management and near-optimal cognitive throughput performance.     

Adaptive beamforming of massive MIMO based on DoA in high mobility scenarios

A direction of arrival based (DoA-based) beamforming of massive MIMO was proposed for high-speed railway scenarios.In order to guarantee that the optimal system capacity can be obtained during traveling,an iterative multi-beams scheme was proposed.It aimed to design different beams for different mobile carriage terminals (MCT) respectively.The proposal adaptively selected the number of antennas for each beam,and adaptively designed the number of beams according to system capacity.Moreover,the scheme didn’t need channel state information (CSI) that can reduce system implementation complexity and cost.Numerical results indicate that the proposed scheme is suitable for high-speed scenarios,the system performance can be improved more efficiently compared to conventional methods.     

AMC-based resource allocation in adaptive frequency reused OFDMA-relay networks

In orthogonal frequency division multiple access (OFDMA) relay system, for supporting relay transmission, the base station (BS)-the relay station (RS) link must consume an extra part of resource, which may result in serious resource shortage. In oxder to improve resource utilization, this paper proposes a dynamic resource allocation scheme in adaptive frequency reused OFDMA-relay system based on adaptive modulation and coding (AMC) technology. In this scheme, relay nodes have two independent antennas and operate in decode-and-forward (DF) and full-duplex mode. Then the BS and RSs share the same subcarriers by spatial multiplexing by two independent antennas. The resource allocation problem is formulated for system downlink throughput maximization. Since the optimal solution couldn't be obtained easily, a sub-optimal algorithm is proposed.The adaptive frequency reused algorithm with two independent antennas RS improves the system throughput about 24.3 %compared with the orthogonal frequency allocation with single-antenna model, and increases the system throughput 10.4%compared with adaptive frequency reused algorithms with single-antenna RS. It is proved that both of the RS with two-antenna model and adaptive frequency reused scheme can improve the system throughput significantly.     

A high-speed adaptive antenna array with simultaneous multibeam-forming capability

A new type of adaptive beamforming antenna system architecture is proposed for multichannel wireless communications. Multibeam communication with high data throughput is accomplished using the proposed beamformer architecture. The system consists of analog mixers, a multitone direct digital synthesizer (DDS), and a digital signal processor (DSP) controller. The essential idea of multibeam forming is based on a multitone weighting scheme combined with analog-digital hybrid signal processing. While the real-time multibeam construction is realized by the analog mixer circuits and a DDS, the complicated adaptive beamforming and direction-of-arrival estimation algorithms are carried out by the DSP. In this architecture, only one beamformer circuit is required to handle multiple beams, leading to significant reduction in hardware counts. A 5.8-GHz eight-element adaptive beamforming array successfully demonstrates two-beam simultaneous beamforming with less than three degrees of peak and steering errors and more than 20-dB interference suppression. The test-bed exhibits successful two-channel data recovery at 25-Mb/s data throughput in each channel with binary phase-shift keying modulation, for simultaneous dual-beam reception. The bit-error-rate measurement validates the robustness of the communication quality under strong interferences.     

Adaptive Radio Resource Allocation for a Mobile Packet Service in Multibeam Satellite Systems

In this paper, we introduce an adaptive radio resource allocation for IP‐based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka‐band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system‐level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user‐level adaptation.     

高速铁路无线通信中基于正交空时码的格型正交重构算法

分析了基于正交空时码的开环和闭环MIMO系统,并着重研究了高铁场景下速度对正交空时码的影响：高速移动导致的快时变信道将会破环正交空时码的正交结构,降低由此获得的分集增益,从而引起了误码率性能的降低。提出了格型正交重构算法,通过givens变换对正交空时码进行码内正交重构;算法在恢复码内正交性的同时,也改变了发射端波束成形方向。因此,在高速移动场景下,所提算法使发射端获得了波束成形的阵列增益以及与用户静止时相同的分集增益。从系统性能仿真中看出,所提算法提升了高铁场景下基于正交空时码MIMO系统的误码性能。     

用于MIMO广播信道的带多波束选择的正交随机波束成形算法

本文提出一种基于有限反馈的波束和用户选择方案,在这种方案中,用户端利用一个随机正交码本对其信道方向信息(CDI)进行量化,计算其最大信号与干扰加噪声功率比(SINR),并把这些信息反馈给基站;基站根据接收到的这些反馈信息,按照和容量最大的准则选择出多个正交波束以及相应的多个用户.和sharif等人最近提出的方案相比,我们提出的方案能根据系统参数,如用户数和信噪比(SNR),对选择的波束成形矢量及其对应的用户的数量和集合进行调整,当用户数量较小时,和容量性能得到了很大的提升,同时避免了选择波束成形矢量时的用户冲突,另外,基站也不需要广播波束成形矢量给各个用户.     

Joint Opportunistic Spectrum Sharing and Dynamic Full Frequency Reuse in OFDMA Cellular Relay Networks

This paper considers the problem of spectrum sharing in orthogonal frequency division multiple access cellular relay networks. Firstly, a novel dynamic full frequency reuse scheme is proposed to improve the spectral efficiency. Different from the conventional full frequency reuse scheme which only allows the base station (BS) reusing the subcarriers in the specific regions, an improved full frequency reuse scheme is proposed to allow the BS reusing all the subcarriers in the whole BS coverage region to exploit additional multiuser diversity gain. In order to dynamically reuse the frequency resource among the BS and relay stations (RSs) to further improve the spectral efficiency, the adaptive subcarrier scheduling is introduced into the improved full frequency reuse scheme to obtain more multi-user diversity gain, which forms the proposed novel dynamic full frequency reuse scheme. Secondly, in order to further increase the system throughput, the opportunistic spectrum sharing scheme is introduced to allow the RSs selectively reusing the subcarriers among each other, which joint with the proposed dynamic full frequency reuse scheme to intelligently allocates the subcarriers originally reused by the BS and a RS to another suitable RS which can best improve the system performance after considering the additional interference. Thirdly, in order to select The optimal reusing combination scheme of BS and RSs to exploit more potential system performance, a heuristic approach based on genetic algorithm is proposed to search the optimal BS and RSs combination to opportunistically share the frequency resource. Simulation results show that the proposed dynamic full frequency reuse scheme can obtain high spectral efficiency, fine fairness and low outage probability compared to the conventional full frequency reuse scheme. Furthermore, the system performance can be improved when considering the opportunistic spectrum sharing among RSs. Finally, after adopting the genetic algorithm, the system performance can be greatly improved by the frequency reusing among the optimal BS and RSs combination.