MR数据支持下的农村FDD900覆盖规划策略探讨

FDD900在农村地区充分覆盖,能进一步突出FDD900核心技术优势。以MR数据技术为载体,结合对农村地区移动网络应用分析,并围绕FDD900技术优势开展一体化规划布局,对于提高FDD900在农村地区覆盖有效性有着一定帮助作用。     

Observer-Based Optimal Fault Detection and Diagnosis Using Conditional Probability Distributions

A new optimal fault detection and diagnosis (FDD) scheme is studied in this paper for the continuous-time stochastic dynamic systems with time delays, where the available information for the FDD is the input and the measured output probability density functions (pdf's) of the system. The square-root B-spline functional approximation technique is used to formulate the output pdf's with the dynamic weightings. As a result, the concerned FDD problem can be transformed into a robust FDD problem subjected to a continuous time uncertain nonlinear system with time delays. Feasible criteria to detect and diagnose the system fault are provided by using linear matrix inequality (LMI) techniques. In order to improve FDD performances, two optimization measures, namely guaranteed cost performance and$H_infty$performance, are applied to optimize the observer design. Simulations are given to demonstrate the efficiency of the proposed approach.     

基于压缩感知的大规模MIMO下行信道状态信息获取

信道状态信息（Channel State Information,CSI）对于大规模多输入多输出（Multiple-Input Multiple-Output,MIMO）发挥高性能至关重要。但在上下行传输信道不存在互易性的频分双工（Frequency Division Duplex,FDD）制式下,若采用传统的信道估计方法会给CSI的获取带来巨大的导频开销和计算量。考虑利用大规模 MIMO 信道的虚角域稀疏性来减少获取CSI所需开销,在此基础上进一步研究了大规模 MIMO 正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统中各子载波信道在虚角域的共同稀疏特性和稀疏支撑集的时间相关特性,达到降低信道维度的目的,则大大减少了基站对 CSI 获取所需的资源开销。同时,为了降低信道稀疏支撑集信息获取所需的导频开销和提高信息的时效性,利用压缩感知技术对支撑集进行估计。仿真结果验证了所提方案性能的优越性。     

Fault detection and diagnosis in asymmetric multilevel inverter using artificial neural network

The increased component requirement to realise multilevel inverter (MLI) fallout in a higher fault prospect due to power semiconductors. In this scenario, efficient fault detection and diagnosis (FDD) strategies to detect and locate the power semiconductor faults have to be incorporated in addition to the conventional protection systems. Even though a number of FDD methods have been introduced in the symmetrical cascaded H-bridge (CHB) MLIs, very few methods address the FDD in asymmetric CHB-MLIs. In this paper, the gate-open circuit FDD strategy in asymmetric CHB-MLI is presented. Here, a single artificial neural network (ANN) is used to detect and diagnose the fault in both binary and trinary configurations of the asymmetric CHB-MLIs. In this method, features of the output voltage of the MLIs are used as to train the ANN for FDD method. The results prove the validity of the proposed method in detecting and locating the fault in both asymmetric MLI configurations. Finally, the ANN response to the input parameter variation is also analysed to access the performance of the proposed ANN-based FDD strategy.     

An Overlaid Hybrid‐Division Duplex OFDMA System with Multihop Transmission

In this letter, we propose an overlaid hybrid division duplex (HDD) concept for cellular systems which divides a cell into inner and outer regions and utilizes the merits of both time division duplex (TDD) and frequency division duplex (FDD). The proposed system can take advantage of both TDD and FDD without handover between two duplex schemes. Moreover, it is shown that the proposed HDD system outperforms the conventional TDD or FDD system with mobile relay stations when the synchronization issue is considered in orthogonal frequency division multiple access systems. Thus, the proposed overlaid HDD can be considered as a new framework for future cellular systems.     

A RAKE receiver design for WCDMA FDD uplink with an RLS-based adaptive beamforming scheme

In this paper, we present a RAKE receiver design with adaptive antenna arrays for the wide-band code-division multiple-access (WCDMA) frequency-division duplexing (FDD) uplink. The RLS-based adaptive beamforming scheme is proposed and can be built with the existing one-dimensional RAKE receiver. We adaptively calculate the beamforming weight vector for each multipath of the desired user, and use maximum ratio combining (MRC) to combine each multipath signal in the demodulation process. Two matched filters based on the spreading waveforms are designed in our scheme for WCDMA FDD uplink application. The proposed scheme has the ability of suppressing strong multiuser access interference and the other types of interferers through spatial ing. The tracking capability of the proposed algorithm is demonstrated in the simulation results.     

Effective adaptive transmit power allocation algorithm considering dynamic channel allocation in reuse partitioning-based OFDMA system

This paper introduces an transmit power allocation (TPA) algorithm considering dynamic channel allocation (DCA) for a reuse-partitioning- based Orthogonal frequency division multiple access (OFDMA)/FDD cellular system. The proposed reuse partitioning-based DCA algorithm guarantees quality of service (QoS) by considering fairness among mobile stations in an OFDMA/FDD system. However, to improve the SINR values for users around the cell edge and increase the overall system throughput compared with the conventional OFDMA/FDD system of frequency reuse factor (FRF) 1, an effective TPA algorithm is also combined with the proposed DCA to adjust the transmit power per user according to the average received SINR value. Simulation results show that the proposed DCA algorithm increases the sector throughput by about 25% when compared with the conventional case that do not apply the proposed DCA algorithm. When the proposed TPA is combined with the proposed DCA algorithm, a further increase in the sector throughput of about 6% is achieved than when using just the proposed DCA algorithm.     

Channel Magnifying Limited Feedback Technique for FDD Massive MIMO Systems

A limited feedback system, so-called, channel magnifying (CM) is proposed for a downlink (DL) frequency-division duplex (FDD) massive multiple-input multiple-output (MIMO) system. Although massive MIMO system has received significant research interest as a key technology for beyond 4G wireless communications systems, it has a number of issues that needs to be technically addressed. Among such issues is the difficulty of acquiring channel state information at transmitter for an FDD massive MIMO system which cannot exploit channel reciprocity as in a time-division duplex system. The proposed CM technique makes it possible to support a few user equipments in DL FDD massive MIMO system by finding a balance between spatial resources and channel quantization error (CQE). By choosing a subchannel with low CQE, CM can secure multiplexing gain at high SNR based on a fixed size codebook. Two types of subchannel indicator alignment (SIA) schemes are introduced for efficient interference nulling for the proposed CM technique. Specifically, we discuss how to maximize the sumrate of CM through genie added SIA and minimum CQE based SIA. Simulation results show that the sum rate of the proposed CM has a higher multiplexing gain than that of random vector quantization, especially when the number of transmit antennas is sufficiently large.     

Fault Detection and Diagnosis for General Stochastic Systems Using B-Spline Expansions and Nonlinear Filters

This paper presents a new fault detection and diagnosis (FDD) algorithm for general stochastic systems. Different from the classical FDD design, the distribution of system output is supposed to be measured rather than the output signal itself. The task of such an FDD algorithm design is to use the measured output probability density functions (PDFs) and the input of the system to construct a stable filter-based residual generator such that the fault can be detected and diagnosed. For this purpose, square root B-spline expansions are applied to model the output PDFs and the concerned problem is transformed into a nonlinear FDD algorithm design subjected to a nonlinear weight dynamical system. A linear matrix inequality based solution is presented such that the estimation error system is stable and the fault can be detected through a threshold. Moreover, an adaptive fault diagnosis method is also provided to estimate the size of the fault. Simulations are provided to show the efficiency of the proposed approach.     

An assessment of alternative wireless access technologies for PCSapplications

The results of studies on three important wireless access technology issues in the personal communications services (PCS) arena are described. They are signal duplexing, multiplexing on the downlink, and channel frequency assignment. Each of these issues was addressed through the comparison of two competing technologies. In the area of duplexing, frequency division duplexing (FDD) was compared to time division duplexing (TDD) with the result that FDD is preferred if appropriate spectrum is available. Multiplexing on the downlink examined time division multiplexing (TDM) versus a burst downlink (TDMA). TDM is preferred for the wide-area local-exchange environment, but in certain indoor, office applications, TDMA may prove advantageous. The two methods of frequency channel assignment investigated are quasi-state autonomous frequency assignment (QSAFA) and dynamic channel assignment (DCA). QSFA is generally preferred, although indoor, multitenent environments with low port loading may benefit from the use of DCA. These analyses assume that the system uses time-division multiple access (TDMA)     

A new MAC protocol for broadband wireless communications and its performance evaluation

This paper presents a new Time Division Multiple Access/Frequency Division Duplexing (TDMA/FDD) based Medium Access Control (MAC) protocol for broadband wireless networks, supporting Quality of Service (QoS) for real-time multimedia applications. It also gives the Call Blocking Probability (CBP), packet end-to-end delay and utilization analysis of different service classes, as they are most essential performance criterions in broadband wireless network assessment. The Connection Admission Control (CAC) mechanism in the proposed MAC efficiently organizes the bandwidth allocation for different service classes by means of a fairness based scheduling algorithm. In addition, the simulation model of the proposed MAC scheme is realized by using OPNET Modeler network simulator. The results of the analytical calculations for the CBPs are compared to those of the simulation of the proposed MAC, thus validity of the MAC protocol is proved.     

5G NR FDD与WCDMA系统共存研究

为推动5G在中频段的重耕,研究了中频段NR FDD系统与WCDMA系统在相同地理区域邻频共存时的系统间干扰造成的性能损失,分析了在不同功率参数、不同拓扑结构、AAS/NON-AAS 2种天线模型下,4个干扰场景的仿真结果.最后给出NR FDD系统与WCDMA系统共存建议以及共存措施.     

Joint precoding and scheduling algorithm for massive MIMO in FDD multi-cell network

Massive multiple-input multiple-output (MIMO) systems, in which base stations are equipped with a large number of antennas in a two-dimensional antenna array, is one of the most promising technologies to improve the spectral efficiency of the fifth generation mobile communication systems (5G). Since there is no short-term channel reciprocity, the frequency-division duplexing (FDD) massive MIMO system has to obtain channel state information with the help of uplink feedback with acceptable overhead. To cope with this issue, we propose the design of joint precoding and scheduling algorithm in FDD multi-cell network. In the algorithm, all the users are firstly grouped by the statistics of channel correlation matrix, then the inter-group interference exiting among intra-cell and inter-cell is eliminated at the first precoding stage. Then users are adaptively scheduled and beamformed at the second precoding stage based on the low dimension effective channel. Finally, the effectiveness of the proposed algorithm is presented through simulations.

     

A Partial CSI Estimation Approach for Downlink FDD massive-MIMO System with Different Base Transceiver Station Topologies

Massive multiple-input multiple-output (massive-MIMO) is a promising technology for next generation wireless communications systems due to its capability to increase the data rate and meet the enormous ongoing data traffic explosion. However, in non-reciprocal channels, such as those encountered in frequency division duplex (FDD) systems, channel state information (CSI) estimation using downlink (DL) training sequence is to date very challenging issue, especially when the channel exhibits a shorter coherence time. In particular, the availability of sufficiently accurate CSI at the base transceiver station (BTS) allows an efficient precoding design in the DL transmission to be achieved, and thus, reliable communication systems can be obtained. In order to achieve the aforementioned objectives, this paper presents a feasible DL training sequence design based on a partial CSI estimation approach for an FDD massive-MIMO system with a shorter coherence time. To this end, a threshold-based approach is proposed for a suitable DL pilot selection by exploring the statistical information of the channel covariance matrix. The mean square error of the proposed design is derived, and the achievable sum rate and bit-error-rate for maximum ratio transmitter and regularized zero forcing precoding is investigated over different BTS topologies with uniform linear array and uniform rectangular array. The results show that a feasible performance in the DL FDD massive-MIMO systems can be achieved even when a large number of antenna elements are deployed by the BTS and a shorter coherence time is considered.

     

LTE FDD容量规划研究

重点分析了影响LTEFDD容量的相关因素：在此基础上,分析了LTEFDD系统的EpOCh、上下行链路信令开销占比、同时可调度用户数及VoIP用户数,给出了各项指标的具体计算模型及方法,针对15MHz的系统带宽,给出了LTEFDD的计算案例,以帮助LTEFDD无线网络系统容量规划设计。     

New methods for enhancing fine acquisition in dual folding algorithm of long pseudo noise codes

Long code Direct Sequence Spread Spectrum is a good choice for applications where security and antispoofing ability of a spread spectrum connection is concerned. Due to long period of spreading code, acquisition is a challenge for these systems because a trade‐off between detection probability and acquisition time must be made. For confronting this challenge, various algorithms were proposed in the literature but almost all of them focus on expediting the coarse acquisition. In this paper, we consider the efficient dual folding algorithm for coarse acquisition level and propose 3 methods for enhancing the fine acquisition level leading to faster execution of overall acquisition algorithm. The methods are based on estimations from coarse acquisition level that are not used in conventional algorithms for fine acquisition, ie, zero padding. Theoretical expressions of 2 main comparison criteria in acquisition algorithms, ie, detection probability and mean acquisition time, are derived for conventional zero padding and each of the proposed method. Besides, a coarse estimate of resource consumption is provided by the number of floating point operations for each algorithm to make a useful comparison. Considering these 3 parameters, in comparison, the proposed methods surpass zero padding in 1, 2, or all of the 3 aspects. Simulation agrees well with analytical results.     

FDD900M承载及语音质量提升技术研究

随着5G建设的开展,4G频段部分重耕作为5G使用导致4G可用频段减少,与此同时,用户对高速移动数据业务的需求持续增长,频谱资源有限问题性日益严峻.结合网络发展趋势,FDD900M作为后续将长期使用的4G频段,需重点提升其业务承载能力.本文探究FDD900M承载提升整体处理流程,主要着眼于参数优化和干扰优化,提出个性化优...     

Robust Non-linear Precoder for Multiuser MISO Systems Based on Delay and Channel Quantization

In multiuser multiple-input single-output (MISO) systems, non-linear precoder is able to achieve the theoretical sum capacity of downlink channel with perfect channel state information (CSI). However, the perfect CSI is not available at the transmitter in practical system, especially in frequency division duplex (FDD) system where the imperfect CSI is the delayed, quantized channel direction information relayed back from the receiver through a dedicated feedback channel. So the performance of conventional non-linear precoder degrades significantly. In this paper, a robust non-linear Tomlinson–Harashima precoding (THP) based on sum mean squared error (SMSE) minimization for the downlink of multiuser MISO FDD systems is proposed. The proposed precoder is robust to the channel uncertainties arising from channel delay and quantization error. Furthermore, an improved non-linear THP with channel magnitude information (CMI) consideration is introduced to compensate the instantaneous CMI shortage at the transmitter. Additionally, the computational complexity of both proposed precoders can be reduced remarkably by Cholesky factorization with symmetric permutation. Simulation results demonstrate the improvement in bit error ratio performance and illustrate the SMSE performance of the proposed algorithms compared with conventional THP with perfect CSI in the literature.     

FEXT cancellation for twisted-pair transmission

This paper discusses a far-end crosstalk (FEXT) canceller for twisted-pair transmission. Many twisted-pair systems such as fiber-to-the-curb, very high-speed digital subscriber line, and high-speed LAN systems, use frequency-division duplexing (FDD) for duplex transmission. It is shown that the maximum reach of FDD twisted-pair system is limited by the performance of its upstream channel, which is assumed to be located at higher frequencies than the downstream channel. In order to improve the performance of such an FDD transceiver, FEXT cancellation is introduced for the channel at higher frequencies. A system arrangement and its blind startup procedure are studied when the FEXT canceller and equalizer are jointly adapted to combat channel intersymbol interference, FEXT, and other additive noise. We investigate the initial convergence and the steady-state behavior of the proposed twisted-pair system without requiring transmission of an ideal training sequence. Measured characteristics as well as analytical model of the FEXT channel are used to estimate the time span needed for the FEXT canceller. It is also shown that the memory span for the FEXT canceller is almost independent of the channel, thus making our results useful for the twisted-pair system over all different channels     

Design of microstrip wide stopband quad-band bandpass filters for multi-service communication systems

This paper presents two planar high performance quad-channel bandpass filters, which are designed based on a novel circular multi-mode resonator. In this paper and for the first time, the proposed resonator is utilized to achieve quad passbands. It consists of diverged feeding lines that are coupled to etched circular cells. The first filter has quite close channels at 2.62, 2.88, 4.34 and 4.67 GHz, which make it appropriate for frequency division duplex (FDD) scheme. Meanwhile, the second filter is designed for WCDMA and WiMAX applications. Both filters are able to attenuate the harmonics up to 19 GHz with a maximum harmonic level of −20 dB. The insertion losses and return losses of both filters at all channels are better than 1.2 dB and 17.5 dB, respectively. The harmonic attenuation method is presented employing a LC equivalent circuit of the proposed resonator. In order to verify the designing methodology, the proposed filters are fabricated and measured where there are good agreements between the simulation and measurement results.