LTE中一种基于探测参考信号的信噪比估计算法

为了在上行链路支持频率选择性调度,长期演进(LTE)系统定义了探测参考信号(SRS)用于信道质量估计。该文主要研究SRS的信噪比估计方法,针对Boumard方法和传统DFT方法的缺点,提出一种改进的基于DFT的估计方法。该方法通过在时域修正噪声的估计区间,减小高信噪比时有用信号能量泄露对噪声估计的影响,从而获得更准确的信噪比估计。仿真结果表明,所提方法的估计性能优于Boumard方法和传统的DFT方法,提高了高信噪比时的估计精度,在高信噪比区域,平均估计性能提高了约6 dB以上。     

LTE—A基于DMRS的噪声估计算法研究

LTE—A上行参考信号主要包括DMRS（解调参考信号）和SRS（探测参考信号）,DMRS信号主要用于上行信道估计以及eNodeB端的相干检测和解调,以便接收端成功解调数据。信道估计的准确性对于LTE—A系统的性能是至关重要的,而在信道估计算法（MMSE）中,噪声估计的准确性将直接影响到信道估计的性能。因此,为了更加准确地进行信道估计,对噪声估计的研究是非常有必要的。     

LTE上行引入MIMO后的MLE信道估计算法

主要介绍LTE系统上行链路引入MIMO后的信道估计技术。首先介绍了基础的上行和下行信道估计的方法以及他们的区别,然后着重指出了在进行上行MIMO的信道估计时遇到的问题,并阐述了该问题的具体解决方法和详细的公式推导,最后通过对含有MIMO技术的上行LTE链路层的仿真,对在LTE上行MIMO系统中采用MLE算法进行信道估计的精确性进行了验证。     

一种基于LTE TDD系统上行同步控制算法

该文提出了一种LTE TDD系统上行同步控制算法,为移动台提供发送的定时提前量。首先介绍了上行同步控制的过程,分析了利用用户信道估计信息检测信道冲激响应的起始位置、峰值位置和结束位置的方法,并详细描述了上行同步控制算法。仿真结果表明,UE(用户终端)速度为低速或高速以及不同的工作信噪比时,该同步控制算法都能够较好地工作,避免定时不准确导致的ISI。     

针对SC-FDMA系统改进的LS算法

在移动通信系统中,LTE采用单载波频分多址接入(SC-FDMA)技术作为它的上行链路多址接入方案,而信道估计技术是其中的关键技术之一.根据LTE标准协议,基于SC-FDMA系统主要采用导频信道估计算法.其中,主要研究的导频信道估计算法有:LS算法、传统的基于DFT的LS算法、改进的基于DFT的LS算法.最后,理论分析和仿真结果表明:在低信噪比下,尽管改进的基于DFT的LS算法的计算复杂度略有增加,但它比传统的基于DFT的LS算法具有更加优越的估计性能.     

LTE上行信道估计算法研究

LTE（LongTermEvolution,长期演进）是3G与4G技术之间的一个过渡,是3．9G的全球标准,它改进并增强了3G的空中接入技术,采用OFDM和MIMO作为其无线网络演进的唯一标准。文中首先介绍了LTE系统的上行传输方案和基于导频信号的信道估计算法,然后针对LTE上行信道中的PUSCH信道（物理上行共享信道）提出了一套基于MMSE、线性插值以及基于判决反馈的信道跟踪算法的信道估计方案．并给出了该方案的性能仿真图。     

LTE上行块状导频的信道估计研究

继第三代（3G）移动通信之后,长期演进（LTE）作为3G的演进,将是未来通信领域的主流技术。信道估计性能一定程度上决定了通信系统的可靠性,LTE系统上行采用基于块状导频的信道估计。通过MATLAB仿真分析了不同信道估计方法、不同插值方法及不同导频间隔对估计性能的影响,仿真结果可用于指导实际工程应用中信道估计参数的选择。     

智能反射面辅助通信中的信道估计方法

信道信息对于智能反射面(Intelligent Reflecting Surface, IRS)辅助的通信系统十分关键。由于IRS反射单元的数量十分巨大,信道估计和信道反馈的开销一直制约着IRS辅助的通信系统的性能。为解决这一难题,介绍了IRS辅助的通信系统中信道的特性。不同用户共享同一基站(Base Station, BS)-IRS信道,而BS-IRS-用户串联信道具有很强的关联性。基于这一特有的信道特性,提出了IRS辅助的通信系统上行信道估计方法、下行信道估计和信道反馈方法;理论性地刻画了以上方法所需要的最小信道估计开销和信道反馈开销,以揭示所提方法在IRS辅助的通信系统中相对于传统信道信息获取方法的巨大优势。     

LTE上行链路中基于探测参考信号的信噪比估计

信噪比是衡量信道质量的一个重要参数,该文主要研究LTE(Long Term Evolution)系统中基于探测参考信号(Sounding Reference Signal, SRS)的信噪比估计方法。针对DASS(Difference of Adjacent Subcarrier Signal)算法在高信噪比下噪声估计误差较大的这一缺点,该文提出一种适用于SRS的改进DASS方法。该方法通过重新定义子载波的差分方式,减小了噪声估计的误差,并且由于对连续的3个SRS频点,仅需要估计一次噪声,使得该文方法的复杂度仅为原DASS方法的1/3。仿真结果表明,所提方法的估计性能优于其余的方法,特别是在低时延和中等时延信道下,高信噪比时的估计精度提高了约10倍。     

一种基于惩罚因子的LTE上行调度算法研究

针对LTE系统无线信道的复杂性和用户上行信道估计的不准确性,结合上行信道的实际情况,对经典PF调度算法进行改进,提出一种基于惩罚因子的LTE上行调度算法,并采用该算法对GBR业务进行上行调度仿真。实验结果表明,该算法在仿真网络环境下能有效提升LTE网络的上行业务量,提高网络资源的利用率。     

射频干扰环境下OFDM系统的盲信号干扰噪声比估计

基于OFDM信号的循环平稳特性,提出一种在射频干扰环境下OFDM系统的盲信号干扰噪声比估计方法。通过分析发送信号,射频干扰信号以及高斯白噪声的周期自相关函数能量分布规律,选取合适的延时变量和循环频率在功率谱域能有效分离信号功率和干扰加噪声功率分量,从而估计出信号干扰噪声比值。计算机仿真结果表明,和经典的二阶四阶矩(M2M4, second-order and fourth-order moments)盲信号干扰噪声比估计方法相比,新方法不仅能够有效估计射频干扰环境下OFDM系统的信号干扰噪声比值,而且无论是估计性能还是复杂度都优于M2M4方法;同时在快衰落Rayleigh信道下,新方法也能有效的估计出信号干扰噪声比值。进一步,所提方法具有对射频干扰信号密度不敏感的优点。     

TD-LTE系统中动态下行波束赋形算法性能分析

根据加权粒度的差别,介绍了per-RB-MRT算法和full-BW-EBB算法的原理,并对这两种算法的特点以及性能差异进行了理论分析.构建了符合3GPP规范定义的TD-LTE系统上下行仿真平台,对这两种算法在有信道估计误差(包括信道估计精准度和信道信息时延)的情况下的其性能进行了理论分析和仿真研究.仿真结果表明,per-RB-MRT算法在上行信道估计值和下行信道实际值契合较好的情况下能够趋于最佳理论性能,而full-BW-EBB算法由于利用了相对稳定的信道空间相关特性,因而能够在较差的信道环境中保持较高的性能鲁棒性.这些仿真结果对于实际场景中的算法选择提供了重要的参考依据.     

Unified framework for the analysis and design of linear uplink power control in CDMA systems

In this work, it is proposed a unified framework to design and analyze uplink distributed power control schemes over flat-fading channels from a control theory perspective. The effects of linear detectors and round trip delays are explicitly characterized in this study. First, the optimal solution to the power minimization problem under signal to interference-noise ratio (SINR) restrictions is reviewed, where sufficient conditions for its existence are presented that depends on the detection strategy. Four different linear detection schemes are studied in this work: Matched Filter, Decorrelator, MMSE and Projector. Specifically, two special cases are analyzed with respect to the spreading codes properties: uniform cross-correlation and orthogonal codes, and under both conditions an explicit expression for the central solution is obtained. Nevertheless, one drawback of the central solution is its lack of robustness against channel estimation errors, transport delays and noise. Hence, it is proposed closed-loop control laws with linear power assignment which are capable of provide robustness to these channel effects. It is then presented that under certain conditions, stable feedback loops can be obtained considering SINR quantification, transmission and processing delays, and the resulting closed-loop power solutions tend to the central ones. Finally, it is illustrated that the selection of the linear detectors does not affect the resulting closed-loop dynamics, but the uplink transmission power in steady-state. An exhaustive simulation evaluation is included to validate the mathematical analysis presented for open and closed-loop solutions.     

一种基于PN序列的OFDMA上行链路参数估计和信号检测方法

该文研究了OFDMA上行链路的频偏信道参数估计和信号检测问题,设计了一种OFDMA上行链路发射信号帧结构,信号帧的帧头由PN序列构成;提出了基于PN序列的频偏信道参数估计算法;并根据频偏信道参数采用时域最小均方误差检测算法进行信号检测。仿真表明：该文提出的频偏信道估计算法充分利用PN序列的相关特性,具有良好的抗噪特性、衰落信道适应性和高的估计精度;而时域最小均方误差信号检测算法也具有较好的误比特率性能。     

Interference alignment scheme for massive MIMO system

The performance of massive multiple-input multiple-output （MIMO） system is limited by pilot contamination. To reduce the pilot contamination, uplink and downlink precoding algorithms are put forward based on interference alignment criterion. In the uplink receiving processing, the target function aligns the pilot contamination and the interference signals to the same null space and acquires the maximal space degree of the desired signals. The uplink receiving precoding matrix is solved on maximal signal to interference plus noise ratio （SINR） criterion considering the impact of the pilot contamination on channel estimations. The uplink receiving precoding matrix is used as the downlink transmitting precoding matrix. Exploiting the channel reciprocity, it is proved that, if the uplink receiving precoding matrix achieves maximal S1NR, the identical precoding matrix can be used in the downlink transmission and acquires maximal signal to leakage plus noise ratio （SLNR）. Simulations show that the spectrum efficiency of the proposed algorithm can reach about 1.5 times higher than that of popular matched filtering （MF） precoding algorithm, and about 1.1 times higher than multi-cell minimum mean square error （MMSE） precoding algorithm. The performance of the proposed algorithm can be improved approximately linearly with the increasing of the number of antennas.     

LTE-A PUCCH多用户接收算法研究

LTE-A系统使用参考信号进行上行信道估计,而使用PUCCH format 2a/2b发送上行控制信息时,由于每个时隙只有一个SC-FDMA符号可以用于传输参考信号,所以此时接收端不能直接利用参考信号进行信道估计.给出了一种易实现且复杂度低的PUCCH 2a./2b的半盲检测接收算法,该算法利用ACK/NACK信息辅助信道估计.仿真结果表明,文中提出的方法能有效提高PUCCH 2a/2b的接收性能.     

MIMO-OFDM channel estimation method utilizing correlation in time domain for B3G-TDD uplink

This article proposes a simple pilot-aided channel estimation method based on correlation in time domain for multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Pilot symbols in all transmit antennas are generated from different circular shifting of a certain sequence. Through once correlation, the receiver can obtain time-domain pulse responses for channel fading from all transmit antennas to a certain receive antenna, from which channel estimation in frequency domain can be obtained. Beyond 3G time-division duplex (B3G-TDD) uplink is introduced, and the channel estimation method is used in it. Theoretical analysis and simulation are both carried out. Mean square error (MSE) performance shows that the method can exhibit precise estimation. Complexity analysis proves it requires very low complexity. System simulation result shows that it guarantees the performance of B3G-TDD uplink very well.     

Performance of personal access communications system-unlicensed B

The FCC has allocated the band between 1920 MHz and 1930 MHz for unlicensed personal communications services (UPCS) using isochronous or circuit operation. The UPCS spectrum is between the licensed PCS spectrum bands of 1850-1910 MHz and 1930-1990 MHz. Terminal interoperability in both the UPCS spectrum on private indoor wireless systems and the licensed spectrum on public PCS systems is desirable and encouraged by the FCC. This paper presents a port channel assignment process for the personal access communications system-unlicensed B (PACS-UB) which abides by the FCC etiquette for UPCS and discusses the corresponding uplink and downlink performance. Uplink power control is employed to improve the uplink performance. PACS-UB has a high degree of commonality with licensed PACS to permit economical licensed/unlicensed terminals and common network services. The results of our simulation show that, at 1% to 2% blocking probability, 99% of downlink local-mean signal-to-noise plus interference ratio (SINR) values are above 17 dB for a 10 to 20 m port separation. For a three-dimensional office environment, the uplink limits the SINR performance, however, with uplink power control, a 5.5 to 7 dB improvement in the uplink SINR can be achieved even for high traffic load     

TD-LTE非理想信道互易性下的下行单用户波束成形算法

在TD-LTE系统中由于上下行信道的时变特性、干扰非对称特性以及射频器件非对称特性会影响基于信道互易性的波束成形技术应用,降低系统增益。针对非理想信道互易性下的预编码矩阵设计问题,以最大化接收信号平均信干噪比做为目标函数,通过计算信道状态信息(CSI)估计值以及互易性误差的统计自相关矩阵,构造正则矩阵束,将最大化接收信干噪比的预编码矩阵求解问题转化为正则矩阵束的广义特征向量求解问题。计算机仿真验证了算法设计的预编码矩阵能有效增强系统的鲁棒特性。