低压电力线通信网络特性模型与组网算法

由于低压电力线载波通信网络具有物理拓扑复杂和电力线信道时变的特征,在实际应用中存在着通信可靠性较低的问题。为了提高低压配电网电力线载波通信系统可靠性,在总结前人提高电力线通信可靠性的研究基础上,分析电力线通信网络的拓扑结构和组网模型,并提出组网的优化目标函数;进而提出一种基于信道状态和服务需求的电力线通信组网算法。分析了网络拓扑结构,信道特性和通信误码率、传输延时之间的关系,并提出估算方法。仿真试验结果表明,所提算法可根据信道和通信链路的动态变化以及不同的服务需求而动态地建立并优化电力线通信网络路由,保证通信网络的有效性,为后续的工程应用提供参考。     

OFDM中一种改进的SVD信道估计算法

电力线信道高噪声、大衰减等特性使得信道估计在基于OFDM的宽带电力线通信中尤为重要.本文针对OFDM中传统SVD信道估计算法以循环前缀长度为界来截取特征值会引入较大信道噪声的问题,提出了一种改进的SVD算法,该算法通过对信道最大多径时延进行估计并利用该估计值截取特征值,以此来减少噪声影响,仿真表明该算法可有效提高原算法性能,估计效果接近于最小均方误差算法(LMMSE).     

一种基于OFDM的正交通道信道估计算法

文章详细介绍了信道估计在OFDM中的应用，提出了一种在电力线通信环境下的信道估计方法——CEOC（Channel Estimation by using Orthogonal Channels）算法。这种信道估计方法能既保留OFDM系统原有的优点，同时又能跟踪信道变化、降低计算复杂度。与其他方法比较，结果表明这种信道估计算法可以有效克服电力线信道快衰落的影响。     

利用马尔可夫链建模PLC系统中的信道噪声

分析了PLC信道的特点,提出了利用马尔可夫模型对低压电力线通信信道建模。同时讨论了适用于马尔可夫模型参数估算的Baum_Welch算法,提出了消除其上、下溢问题的一种改进方法。在应用Baum_Welch算法对提出的马尔可夫模型进行参数估计和仿真后,文章还对电力线通信系统的2种典型应用环境实测了4种典型调制方式下信道的无误串分布,分析了4种典型调制方式下低压电力线通信信道的特性,所得到的结论与其他研究者的结论相一致,验证了文章提出的观点以及方法理论是切实可行的,其符合实际低压电力线通信信道情况。     

低压电力线通信组网性能优化方法

低压电力线载波通信介质访问控制(MAC)接入协议是影响组网性能的重要因素之一。针对低压电力线通信信道非对称性导致组网性能相对较低的问题,提出面向低压电力线通信改进人工蛛网荷载受限的改进型自适应p-坚持载波侦听多路访问(CSMA)优化方法。详叙了低压配电网物理拓扑映射为改进人工蛛网逻辑拓扑的组网过程;运用所提方法对改进人工蛛网的吞吐量、分组传输时延进行优化,即根据已知参与信道竞争的活跃节点数,动态调整接入概率,控制节点发送数据分组行为,使信道处于最佳传输状态,保证了组网性能。仿真结果验证了所提方法的有效性。     

用于电力线通信系统的OFDM定时同步算法

为了提高电力线通信在恶劣的电力线信道下通信的可靠性,提出了一种新的正交频分复用(OFDM)定时同步算法。该算法在本地相关法的基础上,对Schmidl算法和Park算法的定时函数的计算过程进行改进,实现信号的定时同步。基于MATLAB软件的仿真结果表明,与Park算法相比,所提算法在低信噪比的加性高斯白噪声信道和电力线信道下,都能获得更加精确的定时同步结果,并且所提算法的计算量更小。并在实验室220 V交流电力线的环境下,验证了所提算法的可行性。     

Optimal energy management for industrialmicrogrids with high-penetrationrenewables

Determination of the output power of wind generators is always associated with some uncertainties due to wind speed and other weather parameters variation, and accurate short-term forecasts are essential for their efficient operation. This can efficiently support transmission and distribution system operators and schedulers to improve the power network control and management. In this paper, we propose a double stage hierarchical adaptive neuro-fuzzy inference system (double-stage hybrid ANFIS) for short-term wind power prediction of a microgrid wind farm in Beijing, China. The approach has two hierarchical stages. The first ANFIS stage employs numerical weather prediction (NWP) meteorological parameters to forecast wind speed at the wind farm exact site and turbine hub height. The second stage models the actual wind speed and power relationships. Then, the predicted next day’s wind speed by the first stage is applied to the second stage to forecast next day’s wind power. The influence of input data dependency on prediction accuracy has also been analyzed by dividing the input data into five subsets. The presented approach has resulted in considerable forecasting accuracy enhancements. The accuracy of the proposed approach is compared with other three forecasting approaches and achieved the best accuracy enhancement than all.     

低压电力线通信分簇路由算法及网络重构

低压配电网具有物理拓扑未知和电力线信道时变性特征。为提高低压配电网窄带电力线载波通信系统可靠性,提出并讨论一种基于非交叠分簇算法的电力线通信组网及路由重构方法。该算法可以根据信道质量的变化动态地建立、维护、优化电力线通信网络路由,保证通信网络的有效性。在此基础上,进一步提出并比较两种组网时间序列分配算法,完善了该路由算法。仿真试验表明,该路由算法具有很大的灵活性、实用性和有效性。     

宽带电力线载波OFDM信道估计

正交频分复用（OFDM）是电力线高速数据传输的有效调制技术.而电力线信道的时频双选择性造成OFDM系统的频率偏移,导致载波间干扰（inter-carrier interference,ICI）.为准确掌握信道特性,提出了基于离散长球序列-基扩展模型（DPSS-BEM）的宽带电力线载波OFDM信道估计方法.采用二维DPSS-BEM对电力线信道进行建模,将电力线信道视为二维正交分量的线性加权,并利用导频位置的训练信息和最小二乘法估计权值.仿真表明,该方法能有效地跟踪电力线信道变化,改善信道的归一化均方误差和误码率性能,以便有针对性地采取措施,减少载波间的相互干扰.     

基于局部反射理论的中压配电网电力线通信信道建模法

链路衰减是衡量载波通路传输质量的一项重要指标,为实现对信道衰减特性的预测,提出一种基于局部反射理论的中压配电网电力线通信(PLC)信道建模方法。利用电力线传输理论及局部反射理论,推导端接负载的传输线、不同特性参数的传输线级联情况下的电压传输规律。在此基础上,分别搭建中压配电网无分支线路、带分支线路及带负荷配电变压器线路的PLC信道数学模型。然后根据中压配电网拓扑结构,从配电网末端将所搭模型依次级联至载波信源处,得到末端节点与信源节点间的PLC信道模型,进而分析各节点处载波信号的传输特性。该方法原理简单,计算速度快,可移植性强。仿真及RLC电路实测结果表明了所提建模方法的正确性。     

基于多层感知器的低压电力线时变信道非线性均衡方法

通过添加适当的循环前缀(CP)的正交频分复用(OFDM)技术是一种去除高速通信中符号间干扰的有效方法，但低压电力线作为载波通信通道使用时是一种时变多径信道，采用OFDM技术进行高速载波通信时信号的正交性会因此而受到一定程度的破坏，产生子载波间干扰（ICI）。该文采用基于多层感知器（MLP）的均方差(MSE)准则实现了一种时变信道的非线性均衡。为了验证所提出的非线性均衡方法的有效性，选取具有宽带耦合放大器的实际低压电力线通信(PLC)信道作为实验用非线性信道模型。对比了基于MSE准则的线性和非线性均衡器对系统性能的影响，表明该文采用的非线性均衡方法可以更有效地补偿信道的多径性和时变性造成的影响和改善电力线载波通信系统的性能。     

水下FBMC系统的离散导频信道估计技术研究

水下环境的复杂性对水声通信带来挑战,一般通过优化信道估计技术来实现水下通信的高速率、可靠性传输.将滤波器组多载波/交错正交幅度调制(filter bank based multicarrier/offset quadrature amplitude modulation,FBMC/OQAM)技术引入水下,研究FBMC/...     

基于递归最小二乘的单通道混合信号时延估计算法

针对单通道混合信号的时延估计问题,提出了一种基于递归最小二乘(recursive least squares,RLS)的算法,将时延估计分为了基于循环统计量的粗估计和基于RLS的细估计过程,用二乘方的时间平均准则,对时延粗估计值进行迭代更新,完成整个估计过程.该算法结构简单,收敛速度快,估计精度提升明显,但较依赖于两路...     

Indoor Power-Line Communications Channel Characterization Up to 100 MHz—Part I: One-Parameter Deterministic Model

Advanced communication technologies have allowed the power-line-communication (PLC) channel to be a transmission medium that enables the transfer of high-speed digital data over the classical indoor electrical wires. The development of PLC systems for Internet, voice, and data services requires measurement-based models of the transfer characteristics of the mains network suitable for performance analysis by simulation. This paper presents a deterministic model describing the magnitude and phase of complex transfer functions of power-line networks using only one parameter. First, a PLC channel classification is realized, and an average magnitude and phase channel model by class is proposed. Second, the multipath characteristic of PLC channels is introduced. A statistical-based channel magnitude generator is built, and a group delay-based phase model is suggested.     

一种应用于配电网电力线通信的快速比特分配算法

自适应正交频分复用是一种适用于高速电力线数据通信的技术,比特分配算法是这一技术的重要组成部分。文章针对电力线通信信道的实际条件,探讨了适用于电力线通信的优化模型,并提出了一种新的应用速率自适应准则的动态带宽优化算法,该算法通过对子信道的划分,采用贪婪法原理快速实现子信道的比特分配。理论分析和仿真结果表明该算法具有较低的复杂度,并且能得到令人满意的分配结果。     

低压电力线通信信道的马尔柯夫特性研究

低压电力线通信(PLC)信道具有异常丰富的脉冲噪声，因而呈现出有限记忆性，亦即Markov性。分析了PLC信道脉冲噪声特点后，提出利用分群Markov链对PLC通信信道建模。根据信道脉冲噪声所具有的特点，建立合理假设，给出了分群Markov链的无误串分布公式；明确了由无误串分布确定基本转移概率矩阵的条件以及对应的模型；给出了基于非线性拟合方法的转移概率表达式。论文还对FSK，DPSK，QPSK以及8PSK调制方式下的PLC信道的无误串分布进行了实际测量，并利用所分群Markov链确定了Markov模型基本转移矩阵。对基本转移矩阵的分析表明，8PSK的性能最优，其结论与已有的结论完全吻合，从侧面佐证了信道Markov模型的有效性。     

A nonlinear equalization method based on multilayer perceptron for OFDM power-line communication

A high-speed data-communication over low-voltage power line is currently an active field of broad application. Power-line communication (PLC), based on orthogonal frequency-division multiplexing (OFDM), is developing rapidly. OFDM with an appropriately selected guard interval is considered as one of the most effective ways to eliminate the intersymbol interference of high-rate signal transmission. However, it is unable to deal with the orthogonality degradation between the subchannels due to the time-variant characteristics of the multipath power-line channels, which are known as the interchannel interference problem. It is, therefore, necessary to introduce a nonlinear channel equalizer. In this paper, a multilayer perceptron scheme trained with a mean square error (MSE) criterion is proposed for the design of the nonlinear channel equalizer. The performances of the traditional linear equalizer and the proposed nonlinear one are compared. In order to evaluate the robustness of the proposed approach against the channel distortion, experimental measurements are made in a real PLC network. The effectiveness of the proposed approach is verified via the experiments on the test system.     

A method of ICI cancellation for OFDM with delay diversity

In orthogonal frequency division multiplexing (OFDM) system, the time variation of a wireless channel destroys orthogonality among the sub-carriers, and this induces inter-carriers interference (ICI) and degrades system performance severely in mobile environment. In this paper, a new method of ICI cancellation based on delay diversity (DD) was proposed, which provides a way to mitigate the negative effect from the time variation of the wireless paths, thus improve the system performance greatly. The new method was called time-domain self-interference cancellation (TDSIC) algorithm, which is different from other existing methods, such as frequency-domain method. In a cyclically extended OFDM system, the fading characteristics of extended OFDM symbols with different cyclic delay are different with each other, so in our TDSIC method, a new diversity collection scheme at the receiver end is proposed, which can be used to improve the system performance by suppressing ICI through selecting appropriate parameters. Moreover, the cyclically extended OFDM symbol at the transmitter side and diversity collection with different delay added OFDM symbols at the receiver side are used in the TDSIC method with the tradeoff of time-expense, so the well-known fixed delay for symbol at the transmitter side may be detected by the receiver side through estimating several parameters of wireless channels. In summary, the key of the TDSIC method is to improve the system performance with the cost of time. Based on performance analysis, simulation has proved that TDSIC may effectively improve the performance of the time-variant wireless channel.     

OFDM系统中基于DCT的信道估计迭代算法

提出了一种基于离散余弦变换(DCT)的正交频分复用系统(OFDM)的信道估计算法。该算法是一个迭代过程,首先计算导频子载波处的信道响应,然后通过DCT变换域的低通滤波器有效地抑制了加性高斯白噪声(AWGN)和载波间干扰(ICI)的影响,全部子载波上的信道估计由扩展的离散余弦逆变换(EIDCT)得到。利用DCT的特性,该算法消除了基于离散傅里叶变换(DFT)的信道估计方法中的混叠效应,使得OFDM系统在移动条件下能够很好地工作。仿真结果表明了基于DCT的信道估计迭代算法的有效性。     

Iterative channel estimation and decoding of turbo-coded OFDM symbols in selective Rayleigh channel

This work deals with the detection of turbo-coded symbols in orthogonal frequency-division multiplexed (OFDM) systems. OFDM symbol detection requires channel estimation, which is often carried out using known pilots. In this paper, an iterative detector composed of a turbo decoder and a channel estimator is proposed. These modules perform jointly and exchange soft information through an iterative process. The decoder consists of the maximum a posteriori Bahl-Cocke-Jelinek-Raviv (MAP-BCJR) algorithm, and the channel estimator is based on the minimum mean-square error (MMSE) criterion. The proposed approach allows for the use of all available information, increases the quality of channel estimation, and improves the system performance. This paper also proposes a new expression of the channel reliability factor used by the MAP-BCJR decoding algorithm. This metric depends on signal-to-noise ratio and the channel estimation error variance. The effect of the channel reliability factor and of the channel estimation error are investigated.