A Compact Self-Isolated MIMO Antenna System for 5G Mobile Terminals

A compact self-isolated Multi Input Multi Output (MIMO) antennaarray is presented for 5G mobile phone devices. The proposed antenna systemis operating at the 3.5 GHz band (3400–3600 MHz) and consists of eight antennaelements placed along two side edges of a mobile device, which meets the currenttrend requirements of full-screen smartphone devices. Each antenna element isdivided into two parts, a front part and back part. The front part consists of anI-shaped feeding line and a modified Hilbert fractal monopole antenna, whereasthe back part is an L-shaped element shorted to the system ground by a0.5 mm short stub. A desirable compactness can be obtained by utilizing the Hilbert space-filling property where the antenna element’s overall planar size printedon the side-edge frame is just (9.57 mm × 5.99 mm). The proposed MIMO antenna system has been simulated, analyzed, fabricated and tested. Based on the selfisolated property, good isolation (better than 15 dB) is attained without employingadditional decoupling elements and/or isolation techniques, which increases system complexity and reduces the antenna efficiency. The scattering parameters,antenna efficiencies, antenna gains, and antenna radiation characteristics areinvestigated to assess the proposed antenna performance. For evaluating the proposed antenna array system performance, the Envelope Correlation Coefficients(ECCs), Mean Effective Gains (MEGs) and channel capacity are calculated.Desirable antenna and MIMO performances are evaluated to confirm the suitability of the proposed MIMO antenna system for 5G mobile terminals.

Design of Six Element MIMO Antenna with Enhanced Gain for 28/38 GHz mm-Wave 5G Wireless Application

The fifth-generation(5G)wireless technology is the most recent standardization in communication services of interest across the globe.The concept of Multiple-Input-Multiple-Output antenna(MIMO)systems has recently been incorporated to operate at higher frequencies without limitations.This paper addresses,design of a high-gain MIMO antenna that offers a bandwidth of 400 MHz and 2.58 GHz by resonating at 28 and 38 GHz,respectively for 5G millimeter(mm)-wave applications.The proposed design is developed on a RT Duroid 5880 substrate with a single elemental dimension of 9.53×7.85×0.8 mm^(3).The patch antenna is fully grounded and is fed with a 50-ohm stepped impedance microstrip line.It also has an I-shaped slot and two electromagnetically coupled parasitic slotted components.This design is initially constructed as a single-element structure and proceeded to a six-element MIMO antenna configuration with overall dimensions of 50×35×0.8 mm^(3).The simulated prototype is fabricated and measured for analyzing its performance characteristics,along with MIMO antenna diversity performance factors making the proposed antenna suitable for 5G mm-wave and 5G-operated handheld devices.

4-Port Octagonal Shaped MIMO Antenna with Low Mutual Coupling for UWB Applications

A4-port multiple-input multiple-output(MIMO)antenna exhibiting lowmutual coupling andUWBperformance is developed.The octagonal-shaped four-antenna elements are connected with a 50microstrip feed line that is arranged rotationally to achieve the orthogonal polarization for improving the MIMO system performance.The antenna has a wideband impedance bandwidth of 7.5GHz with S11<−10 dB from(103.44%)3.5–11GHz and inter-element isolation higher than 20 dB.Antenna validation is carried out by verifying the simulated and measured results after fabricating the antenna.The results in the form of omnidirectional radiation patterns,peak gain(≥4 dBi),and Envelope Correlation Coefficient(ECC)(≤0.01)are extracted to validate the suggested antenna performance.Aswell,time-domain analysis was investigated to demonstrate the operation of the suggested antenna in wideband applications.Finally,the simulated and experimental outcomes have almost similar tendenciesmaking the antenna suitable for its use in UWBMIMOapplications.

Joint User Scheduling and Antenna Selection in Distributed Massive MIMO Systems with Limited Backhaul Capacity

Massive MIMO systems offer a high spatial resolution that can drastically increase the spectral and/or energy efficiency by employing a large number of antennas at the base station(BS).In a distributed massive MIMO system,the capacity of fiber backhaul that links base station and remote radio heads is usually limited,which becomes a bottleneck for realizing the potential performance gain of both downlink and uplink.To solve this problem,we propose a joint antenna selection and user scheduling which is able to achieve a large portion of the potential gain provided by the massive MIMO array with only limited backhaul capacity.Three sub-optimal iterative algorithms with the objective of sumrate maximization are proposed for the joint optimization of antenna selection and user scheduling,either based on greedy fashion or Frobenius-norm criteria.Convergence and complexity analysis are presented for the algorithms.The provided Monte Carlo simulations show that,one of our algorithms achieves a good tradeoff between complexity and performance and thus is especially fit for massive MIMO systems.

Study of Radio over Fiber Transmission with a Single Line in Ring Topology for Deployment of MIMO Antenna Access Points in a Cell-less Network

The massive growth of wireless traffic goes hand in hand with the deployment of advanced radio interfaces as well as network densification. This growth has a direct impact on the radio access architecture, which today is moving from centralized to distributed deployments through the use of a large number of access points (APs). This paper verifies the feasibility of deploying multiple APs in series on a single line in a ring topology in a cell-less network. On the one hand, this technique will further improve the communication capacity and flexibility of a Radio-over-Fiber (RoF) based mobile communication system and will reduce its construction cost. And on the other hand, this deployment topology is a solution to achieve a massive cell-free Multiple-Input Multiple-Output (MIMO) architecture and a cost-effective fronthaul solution. First, a passive optical add/drop multiplexer (OADM) is used to extract and add downlink and uplink signals from the remote access points of one kilometer. Then, a deployment model is developed with version 17 Optisystem software. The results obtained showed that the quadrature amplitude modulation (QAM) does not adapt to this multi-carrier transmission to deploy several AP in series on a single line. Thus, the performance degradation increases when the number of APs integrated on the line increases.

Invited Paper: Antenna Selection in Energy Efficient MIMO Systems: A Survey

With the explosive growth and need for high-speed wireless communications, more and more energy is consumed to support the required quality of service. Therefore, energy efficient or green communication has become a very hot topic under the ground of limited energy resource and environmentally friendly transmission schemes. MIMO technique is capable of reducing the transmission power thanks to its diversity and multiplexing gain. Moreover, antenna selection(AS) is an alternative to extract many of the benefits in MIMO systems with a reduced cost of complexity and power. Although many works including several survey papers have investigated AS in MIMO systems, the goal of these works is only the capacity maximization or error rate minimization, which fails to guarantee the optimality of the energy efficiency in MIMO systems. In this paper, we overview the state of the art in the AS schemes in energy efficient MIMO systems, the goal of which is to optimize the energy efficiency of the whole system. Specifically, we introduce energy efficient AS in point-to-point MIMO, cooperative MIMO, multiuser MIMO and largescale MIMO systems, respectively. Several challenging and practical issues in this area are also addressed.

A Tri-Port MIMO Antenna Designed for Micro/Pico Cell Applications with Self-Decoupled Structure

A tri-port MIMO antenna designed for Micro/Pico-Cell application is proposed.It is based on printed elements with X-shaped arms,which are oriented to 0°,120° and240° in the azimuth plane.The arms of these elements are connected,with which a selfdecoupled structure is formed.The mutual coupling between adjacent elements is below-15 dB.Meanwhile,it size is compact and bidirectional radiation patterns with around 4dBi Gain and 92° 3dB beam width is achieved,which can provide good pattern diversity and full azimuth coverage in real applications.

Capacity and Spatial Correlation Measurements of Compact MIMO Antennas

The dual-port compact multiple-input multiple-output(MIMO)dipole antennas with close spacing d of 0.5λand 0.3λare designed,and some electromagnetic band gap(EBG)structures are inserted between them to reduce mutual coupling.Those MIMO antennas with d=0.5λand 0.3λ,and with different mutual couplings are fabricated and measured,the channel capacity and correlation coefficient(CC)are analyzed and compared in a rich multipath reverberation chamber(RC),an office and a conference room.Results show that if d is reduced from 0.5λto 0.3λ,in the RCs,channel capacities of all the antennas are very close to that of the i.i.d.Rayleigh channel,although the average CCs are increased from 0.168 in the nonlossy RC to 0.269 in the lossy RC.In the office and conference rooms,compared with the RC,the average capacities of those antennas get a slight reduction,however,in most cases,the capacity of d=0.5λis larger than that of d=0.3λ,and the antennas with EBG have a larger capacity compared with the antennas without EBG,with a corresponding reduction of CC.A non-line-of-sight(NLOS)scenario of through-the-wall is also investigated.

互耦效应对超大规模MIMO天线系统信道容量的影响

超大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)天线系统是6G的关键技术,由于天线单元间距很小,多个天线单元的互耦效应是影响其性能的因素之一。建立了基于石墨烯基贴片天线阵列-子阵列架构的超大规模MIMO天线系统,推导出了互耦效应影响下的信道容量表达式。通过电磁场数值计算仿真了超大规模MIMO天线系统的信道容量,结果表明,在不考虑互耦效应时,超大规模MIMO天线系统的信道容量与子阵列天线单元数、子阵列数以及发射机功率正相关;在互耦效应的影响下,系统的信道容量降低,互耦效应的强弱与子阵列天线单元的间距有关,天线单元间间距越小,相邻天线间的互耦效应越明显,系统的信道容量越小。该仿真结果可以为6G中超大规模MIMO天线系统的设计提供参考。

MIMO Antenna for UWB Communications

Design of ultra-wideband antennas is challenging in the stringent requirements that are often conflicting to achieve a wide impedance bandwidth while maintaining high radiation efficiency, uniform gain and compact size. A Multiple-Input Multiple-Output (MIMO) antenna system can enhance the overall antenna performance but at having to overcome new challenges such as reducing the mutual coupling and the correlation between the elements. A printed circular disc compact planar antenna is selected in this work due to its UWB performance and compact size for the MIMO antenna system. A parametric analysis is carried out to achieve an optimal design. The system developed consists of two elements with an overall size of 59 × 27 mm. The designed antenna system operates over the whole of the UWB bandwidth from 3.1 to 10.6 GHz with radiation efficiency up to 85% and reflection coefficients less that ?10 dB. The envelope correlation is less than ?60 dB throughout the UWB band while the diversity gain approaches 10 throughout the entire UWB bandwidth and Total Active Reflection Coefficient (TARC) between the antenna elements is less ?11 dB. Thus the proposed MIMO antenna outperforms similar antenna systems reported in the literature.

A Compact UWB MIMO Antenna for Portable Applications

A novel compact multiple-input-multiple-output (MIMO) antenna for portable ul-trawideband (UWB) applications is presented. This antenna consists of two modified planar-monopole antenna elements with coplanar waveguides-fed printed on one side of the substrate. To enhance isolation and increase impedance bandwidth, a tree like stubs is placed on the ground plane at the 45&deg;axis. The measured results show that the MIMO antenna operates from 2.3 GHz to 13 GHz, covering WLAN, WiMAX, and UWB. The low mutual coupling and low envelope correlation coefficient of less than 0.2 across the whole frequency band proved that this antenna was suitable for MIMO/diversity systems. Also, good performance of radiation patterns and the antenna’s compact size make it a good candidate for portable devices.

Dynamic Relay Selection Method for Distributed MIMO Relay System

The research on distributed MIMO relay system has been attracting much attention. In this paper, a decode-and-forward scheme distributed MIMO relay system is examined. For upper bound of channel capacity, the distance between transceivers is optimized when the propagation loss is brought close to actuality. Additionally, the number of relay is optimized whether total antenna element is fixed or not. When the number of relay is assumed to be infinite, the dynamic relay selection method based on the transmission rate is proposed. We represent that with the proposed method, the transmit power and the number of relays are saving.

基于特征空间的MIMO天线选择算法

多输入多输出(MIMO)系统中多天线阵元(MEA)的使用增加了硬件成本和信号处理负担,而天线选择技术能够在损失MIMO性能很小的条件下大幅度降低硬件需求。在最大化信道容量的准则下,提出了一种基于信道状态信息(CSI)特征空间的渐消算法及相应的启发式简化算法,并说明了简化算法等价于特征空间矩阵上的基于范数的选择(NBS)算法。仿真实验表明,在接收天线选择个数大于发送天线个数的条件下,两种算法达到的中断容量接近最优选择算法,且计算时间较小。

分布式天线系统MIMO信道容量分析

结合了分布式天线系统和MIMO信道特点的分布式MIMO系统可以改善覆盖特性,提高系统容量。提出了包含路径损耗、快衰落和阴影衰落的两层分集分布式MIMO系统。对MIMO信道容量的分析表明,分布式MIMO系统具有良好的信道容量均匀覆盖特性。与传统集中式天线系统相比,分布式MIMO系统可以获得更好的小区平均信道容量。对下行信道容量的数值分析表明,由于“充水”方式功率分配可以充分利用MIMO信道信息,此时的分布式MIMO系统可以比等功率分配条件下的分布式天线系统多获得0.25bit/(s·Hz)每发送天线的信道容量增量。

一种分布式多入多出(MIMO)信道的容量研究

分布式MIMO系统结合了点对点MIMO信道与分布式天线系统两者的特点,能改善链路的质量,提高覆盖面积。本文提出了一种包含路径损耗、阴影衰落与小尺度衰落的分布式MIMO信道模型,分析推导了采用该模型时的分布式MIMO信道容量。通过计算机仿真,研究分析了阴影衰落、Rice信道因子K等因素对分布式MIMO上行信道容量的影响,得出了分布式MIMO信道容量空间分布的特点。

分布式MIMO-OFDM系统帧同步性能分析

多入多出-正交频分复用(MIMO-OFDM)技术是下一代宽带无线通信系统的核心技术之一,它对定时同步(包含帧同步和符号同步)性能非常敏感,而分布式天线系统是未来通信系统的开放式架构,这种架构使得帧同步的实现更加困难,且算法更加复杂,因此,急需提出性能分析方法来指导帧同步算法的设计.本文为分布式MIMO-OFDM系统的帧同步提出了一种准确的性能分析方法,从帧同步度量函数的统计特征出发,将信号在主信号方向角上进行正交分解,提出了高斯性能分析方法,利用正态分布的3R原则,推导出了正确帧同步概率的求解方法.最后将提出的性能分析方法应用到不同发射天线数目以及目前已经提出的几种算法进行分析和对比,验证了该方法的准确性和有效性.

大规模MIMO系统中的双向搜索天线选择算法

大规模MIMO(Massive MIMO)拥有众多天线,如果按照传统的方式配备等量的射频链路,势必会大幅度增加硬件成本及系统复杂度.天线选择技术能够在不损害多天线系统优势的前提下,使射频链路成本明显下降.天线选择的主要方法其思想是在全部天线中选出部分天线传输数据,从而使射频链路成本不再成为限制因素,在实际的无线信道中,信道状态变化多样,为了达到所需性能指标,通信系统需要选择不同数目的天线进行数据传输,而现有的天线选择算法往往只适用于固定天线数的场景.本文针对多变的信道状态,基于递增选择算法与递减选择算法提出了双向搜索天线选择算法,能够灵活应对不同的天线数需求,并且保持了较低的计算复杂度.

MIMO-OFDM分布式天线系统的定时同步算法

针对现有MIMO-OFDM分布式天线系统的定时同步算法不能准确估计精确符号定时的局限性,提出了一种MIMO-OFDM分布式天线系统的定时同步算法,新算法设计了一个正交变周期训练序列(OVP)集,每根发射天线的前导符号由此集合中的一种训练序列构成,利用天线间训练序列的正交性和变周期性,在接收端定义了相应的帧头捕获度量函数和精确符号定时度量函数,能准确地估计出分布式天线系统的时延矩阵。仿真结果显示:无论在AWGN信道还是多径衰落信道下,各天线时延和天线间时延(ITD)的估计性能都要优于传统算法,有效地解决了MIMO-OFDM分布式天线系统的精确符号定时同步问题。

一种快速的MIMO系统联合收发端天线选择算法

基于MIMO系统发射端和接收端的多天线配置使信道容量和传输可靠性成倍提高,天线选择算法能保持系统优点的同时降低实现复杂度和硬件成本,为在信道环境实时变化条件下快速选择出最优的天线子集,提出一种新的MIMO系统联合收发端天线选择算法。基于二进制粒子群算法思想,通过对MIMO系统信道容量公式的分析,导出采用二进制编码字符串表示的信道容量,以此作为粒子群算法的适应度函数简化计算量;同时采用循环移位种群初始化以提高搜索效率,提高信道容量。仿真结果表明:新算法在降低计算复杂度的同时,获得的信道容量比其他几种次优算法的更高。

一种多用户MIMO-OFDM系统中的天线与子载波分配算法

天线与子载波分配是多用户MIMO-OFDM系统无线资源管理中的重要内容。在分析了多用户MIMO-OFDM系统下行链路中最优天线与子载波分配算法的基础上,提出了一种次优的低复杂度天线与子载波分配算法。该算法通过先选择天线再选择用户从而避免了最优算法中的遍历搜索。仿真结果表明,在运算量大大降低的情况下,所提算法获得的系统最大容量和最优算法所获得的最大容量相比相差不大,而且空间和频率联合优化的结果使其性能远远优于仅在MIMO环境下进行子载波分配的算法。