从电磁场观点审视宽频带的无线通信

指出移动网络的数据流量无法一直依靠增加基地台的数组天线个数提升,认为电磁波在复杂的立体空间传播所产生各种穿透与反射的波传递现象深深影响了数据流量。提出了可能的有效物理方法或路径,用以克服高速移动、多媒体宽频带通信的诸多困难。     

New transmit schemes and simplified receivers for MIMO wireless communication systems

In this paper, optimized transmit schemes for multiple-input multiple-output (MIMO) systems with simplified receivers are proposed for the downlink of high-speed wireless communication systems. In these systems, MIMO signal preprocessing is performed at the transmitter or base station with the receiver at the mobile station having a simplified structure that requires only limited signal processing. An important potential application for our transmit MIMO techniques is in the downlink of high-speed wireless communication systems with Vertical Bell Laboratories Layered Space-Time (V-BLAST) or a similar technique utilized in the uplink, creating a high-speed duplex system with a simplified mobile station transceiver structure. Two approaches are introduced and these depend on whether or not receive diversity is employed at the receiver. Both methods require that channel state information be available at the transmitter. In addition, some important associated issues such as peak-to-average power ratio requirements at the transmitter and robustness to downlink channel errors are also investigated and various solutions are proposed. Simulation results are provided and these show that performance improvement can be achieved when compared with other MIMO transmit schemes.     

Energy efficiency of massive MIMO wireless communication systems with antenna selection

Massive multiple-input multiple-output (MIMO) requires a large number (tens or hundreds) of base station antennas serving for much smaller number of terminals, with large gains in energy efficiency and spectral efficiency compared with traditional MIMO technology. Large scale antennas mean large scale radio frequency (RF) chains. Considering the plenty of power consumption and high cost of RF chains, antenna selection is necessary for Massive MIMO wireless communication systems in both transmitting end and receiving end. An energy efficient antenna selection algorithm based on convex optimization was proposed for Massive MIMO wireless communication systems. On the condition that the channel capacity of the cell is larger than a certain threshold, the number of transmit antenna, the subset of transmit antenna and servable mobile terminals (MTs) were jointly optimized to maximize energy efficiency. The joint optimization problem was proved in detail. The proposed algorithm is verified by analysis and numerical simulations. Good performance gain of energy efficiency is obtained comparing with no antenna selection.     

Hybrid TDOA/AOA mobile user location for wideband CDMA cellularsystems

This paper proposes a mobile user location scheme for wideband code-division multiple-access (CDMA) wireless communication systems. To achieve high location accuracy and low cost of the mobile receiver, the location scheme combines the time difference of arrival (TDOA) measurements from the forward link pilot signals with the angle of arrival (AOA) measurement from the reverse link pilot signal. High chip rates in wideband CDMA systems facilitate accurate TDOA measurements, and a smart antenna used at the home base station (BS) can provide accurate AOA measurement in a macrocell environment. A two-step least square location estimator is developed based on a linear form of the AOA equation in the small error region. Numerical results demonstrate that the proposed hybrid TDOA/AOA location scheme gives a much higher location accuracy than TDOA only location, when the number of base stations is small and/or when the TDOA measurements have a relatively poor accuracy     

A fourth-generation MIMO-OFDM broadband wireless system: design,performance, and field trial results

Increasing demand for high-performance 4G broadband wireless is enabled by the use of multiple antennas at both base station and subscriber ends. Multiple antenna technologies enable high capacities suited for Internet and multimedia services, and also dramatically increase range and reliability. In this article we describe a multiple-input multiple-output OFDM wireless communication system, lab test results, and field test results obtained in San Jose, California. These are the first MIMO system field tests to establish the performance of MIMO communication systems. Increased capacity, coverage, and reliability are clearly evident from the test results presented in this article     

宽带基站天线中反射板对方向图影响的性能分析

采用基于有限元法的数值仿真方法对五单元线阵进行了分析,计算了几种常用的反射板对天线方位面波瓣宽度及前后比的影响,总结了反射板对辐射方向图影响的规律。最后利用得出的结论设计了一款3G频段宽带双极化基站天线,并给出了方向图实测结果,结果与理论值吻合较好。     

MISO CDMA transmission with simplified receiver for wirelesscommunication handsets

The next-generation wireless personal and mobile communication systems are expected to accommodate not only high-quality voice services, but also a broad range of other multirate services. Of the various multiaccess techniques, wide-band code-division multiple access (CDMA) has been regarded as an important part of the third-generation wireless communication systems because of its high frequency utilization efficiency and suitability for handling multimedia and multirate services. In this paper, we consider a system with a simplified receiver structure for direct-sequence CDMA (DS/CDMA) wireless communication handsets, in which improved performance is demonstrated when compared to a conventional DS/CDMA system with a RAKE receiver at the mobile station. We arrive at this system by finding the optimal solution to a general multiple-input single-output (MISO) DS/CDMA smart antenna system. We find that this solution reduces to a pre-RAKE with space transmit diversity system under the assumption that a simple one-finger matched filter is used at the receiver. This system combines the advantages of pre-RAKE diversity and transmit antenna diversity. It is shown that significant system performance and capacity improvements are possible. The numerical results also reveal that this system is not too sensitive to channel estimation errors     

一种空中智能移动通信网络架构的研讨

为了解决移动通信网络发展过程中,高密度建站面临的无法获取足够最优站址的问题,本文通过将无线通信技术、无人机技术、智能控制技术等相结合,提出在空中布设智能运动型基站,构建空中智能移动通信网络的思路。文章在详细阐述空中智能移动通信网络中智能运动型基站、基站蜂巢、智能云平台等组成部分的基础上,进一步提出了该网络架构的通信流程,并对关键技术以及下一步研究方向进行了阐述。     

AoA-Based Channel Estimation for Massive MIMO OFDM Communication Systems on High Speed Rails

Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies.     

载频智能节电技术在TD-LTE通信网络中的应用

在移动通信网络的能耗中,基站的能耗超过了整个通信系统能耗的70%,为了能够实现移动运营商的节能目标,对于无线基站节能减耗技术的研究将是一个非常重要的方面。首先从移动通信基站节能的现状出发,分析了TD-LTE系统中基站主设备智能节电系统设计的必要性。在分析无线网络话务时间规律的基础上,针对移动通信网络话务潮汐的特点,根据TD-LTE系统基站主设备的运行原理,分析了载频关断技术在TD-LTE基站系统中实现节能降耗的方法,提出了载频智能关断技术在TD-LTE基站系统中设计原则和技术方案,并且通过测试验证得出了载频智能关断技术在TD-LTE网络中运行的可行性。最后,对此项技术规模性应用所取得的节能效果进行了总结并提出应用建议。     

Adaptive arrays for narrowband CDMA base stations

Base station antenna arrays are a promising method for providing significant capacity increases in cellular mobile radio systems. This paper examines receiver structures and algorithms to assess the potential capacity gains from the employment of multiple receiver antenna elements, of different sizes, for code division multiple access (CDMA) systems. It considers antenna arrays for the mobile to-base station or reverse link of a CDMA cellular system such as the IS-95 standard. It begins with an introduction to CDMA communication systems and also addresses the general topic of antenna array receivers. Channel modelling is then discussed, as this will influence the design of CDMA receivers. The specific form of receiver array processing algorithms is then discussed and some performance comparisons provided. Finally, the most important reason for implementing antenna array systems, the capacity gains which are achievable, is indicated     

Experimental studies of direction of arrivals using a smart antenna testbed in wireless communication systems

This paper presents some preliminary results from experimental studies on space‐division‐multiple‐access (SDMA) for wireless communications. A smart antenna system utilizing direction‐of‐arrival (DOA)‐based beamforming techniques can enhance signal quality by reducing co‐channel interference from mobiles located at angles spatially distinct from the base station. Adopting both smart uplink and downlink beamforming, a communication system with an antenna array can increase the cell coverage of a base station and significantly boost capacity compared with conventional antenna systems. However, successful implementation of DOA‐based beamforming techniques depends on the DOA characteristics. This paper presented the feasibility of direction finding and DOA variation with respect to frequency. Furthermore, the angle spread was studied for selected environments. The results demonstrate the feasibility of applying proposed smart antenna system utilizing DOA‐based beamforming algorithm for increasing channel capacity and improving system performance in frequency‐division‐duplex (FDD) wireless communication systems. Copyright © 2003 John Wiley & Sons, Ltd.     

基于矢量网络远场测量的移动通信基站天线测试

介绍了一种基于矢量网络远场测量的移动通信基站天线测试方法,该方法具有扫频测量、有效抑制场地反射信号和场外干扰信号等特点,保证了被测天线的测量准确性和可靠性,同时大幅提高了测试效率,较好地满足了移动通信基站天线的测试需求,并进行了验证。     

基于微蜂窝基站应用的小型化多频段内置天线

一种应用于微蜂窝基站的覆盖5个频段的新型多频段小型化内置天线被提出。该天线的体积为26×16×25mm3,可以工作于以下无线通信系统:GSM850/GSM900/DCS/PCS/UMTS。将该天线与微蜂窝基站模型安装在一起之后的测试结果和仿真结果都已给出并予以讨论。     

A novel channel-identification method for wireless communication systems

We present a novel dual-channel identification approach for mobile wireless communication systems. Unlike traditional channel-estimation methods that rely on training symbols, we propose a bent-pipe feedback mechanism which requires the mobile station (MS) to send portions of its received signal back to the base station (BS) for wireless channel identification. Using a filter-bank decomposition concept, we introduce an effective algorithm that can identify both the forward and the reverse channels based only on this feedback information. This new method permits transfer of computational burden from the MS to the resource-rich BS, and leads to significant savings in bandwidth-consuming training signals.     

Reverse Link Performance of DS-CDMA Cellular Systems through Closed-Loop Power Control, Base Station Assignment, and Antenna Arrays in 2D Urban Environment

The interference reduction capability of antenna arrays, base station assignment, and the power control algorithms have been considered separately as means to increase the capacity in wireless communication networks. In this paper, we propose smart step closed-loop power control (SSPC) algorithm and base station assignment method based on minimizing the transmitter power (BSA-MTP) technique for direct sequence-code division multiple access (DS-CDMA) receiver in a 2D urban environment. This receiver consists of conjugate gradient adaptive beamforming and matched filter in two stages using antenna arrays. In addition, we study an analytical approach for the evaluation of the impact of power control error (PCE) on the DS-CDMA cellular systems. The simulation results indicate that the SSPC algorithm and the BSA-MTP technique can significantly improve the network bit error rate in comparison with conventional methods. Our proposed methods can also significantly save total transmit power and extend battery life in mobile units. In addition, we show that the convergence speed of the SSPC algorithm is faster than that of conventional algorithms. Finally, we discuss two parameters of PCE and channel propagation conditions (path-loss parameter and variance of shadowing) and their effects on the capacity of the system via some computer simulations.     

Proposal of a Fixed Communication System Sharing the Bandwidth of an Existing Personal Communication Network

This paper deals with the proposal and performance evaluation of a fixed microwave communication (FMC) system that shares the same bandwidth with a wireless personal communication network. In particular, the focus here is on the case of an existing universal mobile telecommunication system (UMTS) network for which an FMC system is considered to provide a wireless connection between a remote base station not having the possibility of a wired connection to the core network and a base station having this possibility (a core network access point). This facility is of special interest in a dense urban environment or whenever a wired connection is prohibitive for service providers due to its implementation cost or lack of frequency spectrum. The mutual interference effects between the FMC systems and the existing UMTSs are investigated by focusing on typical application scenarios. A receiving scheme where interference signals are first detected and then canceled from the other received signals is proposed. The performance of the two interfering systems has been evaluated in terms of bit error rates (BERs) both by means of an analytical approach and computer simulations. The obtained results clearly demonstrate the effectiveness of the proposed method, in particular, by allowing efficient bandwidth sharing between the FMC system and the existing UMTS network.     

On uplink CDMA cell capacity: mutual coupling and scattering effects on beamforming

It has been shown that code-division multiple-access (CDMA) systems that employ digital beamforming and base station antenna arrays have the potential to increase capacity significantly. Therefore, accurate performance prediction of such systems is important. We propose to take the electromagnetic behavior of the base station antenna array into account, as well as its impact on wireless channel propagation. Specifically, the wideband channel introduces scattering, while the mobile environment causes Doppler fading, which in turn degrades power controllability. We develop a more accurate performance analysis of antenna arrays, where the performance degradation in digital beamforming, due to the combination of mutual coupling, scatter and imperfect power control, and its impact on uplink CDMA system capacity is quantified. A Rayleigh fading amplitude with varying angle-of-arrival spread is assumed, and maximum signal-to-noise ratio beamforming weights are used. These weights are further correlated with mutual coupling at the base station array. Despite the degradation due to the combination of mutual coupling, scattering, and imperfect power control, significant capacity increases are possible.     

卫星移动通信车载站应用性能研究

在对各类卫星移动通信系统性能分析比较的基础上,从系统造价和可实现程度的角度考虑,同步静止轨道(GEO)系统更适合于区域覆盖卫星移动通信系统,卫星移动通信车载站(简称动中通)是实现地面卫星移动通信系统的关键设备。给出了动中通系统设计中卫星转发器带宽占用率和功率占用率的计算,对动中通站型能力和天线口径的选取进行了分析和讨论,并结合相关计算给出了动中通站型和天线选取的建议。     

一种新型多层PCB多频段电场测量传感天线

移动通信基站电磁辐射信号的监测是移动通信正常工作的重要保证,也是保障电磁环境安全的必要手段.文章针对监测设备核心部件——电场测量传感天线的需求,设计了一种新型的介质埋藏式多频段振子天线.利用多层印制电路板（printed circuit board,PCB）布板技术,将三个串馈微带印刷振子天线埋藏在介质基板中,可有效减小天线尺寸.通过仿真和优化实现电场测量传感天线的设计,并制作了天线实物,同时进行了参数测量,结果表明:天线工作的频段基本覆盖2G、3G、4G网络的工作频率范围,分别为0.850~0.950 GHz,1.670~2.740 GHz,方向图全向性好,大小为72.0 mm×48.0 mm×6.0 mm,可以达到测量移动通信基站电磁辐射的电场测量传感天线的专用性、多频段、灵敏度、各向同性和便携性要求.可以使用本文设计的电场测量传感天线来测量基站周围空间电场强度.