干扰抵消技术在多码CDMA系统中的应用

介绍了干扰抵消技术的在多码CDMA系统中的应用背景,工作原理。简述了干扰抵消技术不同的应用形式,如硬干扰抵消、软干扰抵消、联合干扰抵消和部分干扰抵消,并分析了这几种方案各自的优缺点和实现复杂度。最后,展望了干扰抵消技术在未来通信系统中的应用前景。     

干扰抵消技术在多码CDMA系统中的应用

介绍了干扰抵消技术的在多码CDMA系统中的应用背景，工作原理。简述了干扰抵消技术不同的应用形式，如硬干扰抵消、软干扰抵消、联合干扰抵消和部分干扰抵消，并分析了这几种方案各自的优缺点和实现复杂度。最后，展望了干扰抵消技术在未来通信系统中的应用前景。     

OFDM系统基于导频的联合信道估计与干扰抵消算法

对OFDM(orthogonal frequency-division multiplexing)系统中由于时频双选信道产生的载波间干扰进行了分析,并在此基础上提出了一种新的OFDM导频符号结构及信道估计方法,从而实现了在一个OFDM符号内时域信道估计和干扰抵消。仿真结果表明:提出的信道估计与干扰抵消相结合的联合算法不仅可以给出精度较高的信道信息,而且可以明显提高系统的性能。     

MC-CDMA系统中并行干扰抵消的改进

在CDMA系统中,多址干扰是影响系统性能的主要因素。为此,人们提出了并行干扰抵消的检测方法。针对并行干扰抵消中存在的误判问题,本文应用模糊数学中的基本原理,在MC—CDMA系统模型中提出了一种新的部分并行干扰抵消算法——基于估计干信比的模糊并行干扰抵消,并对其原理作了简要阐述。     

MC-CDMA系统迭代检测中的一种信道估计算法

在DS—CDMA系统中，联合译码的迭代多用户检测是克服多址干扰增加系统容量的有效方法。本文将多用户检测和译码相结合的迭代检测技术应用于MC—CDMA系统，其中，多用户检测器由串行干扰消除和其后的MMSE滤波器组成。文中提出一种时域信道估计作为迭代初始值的频域信道估计算法，比单纯的频域信道估计方法节约导频符号数量，并且由于信道估计性能的改善，加快了迭代检测的收敛速度。     

CDMA系统的导频干扰抵消

CDMA蜂窝移动通信系统是一种采用多址技术的通信系统,即采用不同的地址码来区分用户、基站和信道.然而由于其在多径衰落信道中的自相关和互相关特性的不理想造成了码道之间的多址干扰.在扩频通信系统中,有效地抵消导频信道引入的多址干扰是进一步改善系统性能和提高系统容量的重要途径.     

带迭代信道估计的并行多级干扰抑制算法

针对WCDMA反向键路信道结构,提出了一种带迭代信道估计的并行多级干扰抑制算法,详细描述了算法原理和结构。通过计算机仿真,给出了算法中涉及的干扰抑制控制权值、信道估计的迭代次数以及干扰抑制的级数等参数最佳取值,并进行了算法性能比较。仿真结果验证了该算法的有效性。     

OFDM系统中的迭代并行子载波间干扰消除技术

由于实际信道的时变性，OFDM系统中每一子载波上的接收信号受到其它子载波上所传输信号的影响，形成载波间干扰(ICI)并造成误码性能降低。本文提出了适用于OFDM系统的迭代并行子载波间干扰消除接收技术，分析和仿真结果表明此方法可以有效地消除载波间干扰，在归一化多普勒频移为0．1和0．001时，分别提高接收机的性能0.8dB和0．5dB。     

CDMA系统下行链路的干扰抵消

CDMA蜂窝移动通信系统是一种采用多址技术的通信系统，即采用不同的地址码来区分用户、基站和信道。然而由于其在多径衰落信道中的自相关和互相关特性的不理想造成了多址干扰。在扩频通信系统的下行链路中，有效地抵消多址干扰是进一步改善系统性能和提高系统容量的重要途径。本文提出一种应用于CDMA下行链路的干扰抵消算法，分析了下行链路接收机的实现原理及过程，并对其中的关键算法进行了详细地分析，仿真结果表明，所选取的下行接收算法能改善系统的性能。     

同信道干扰对多载波CDMA蜂窝系统下行信道的影响

该文主要讨论多载波CDMA蜂窝系统在下行信道中的同信道干扰问题,理论分析了同信道干扰的解析表达式,并通过计算机仿真得出了在一定的传播损耗下多载波CDMA蜂窝系统下行信道的性能。通过仿真发现,即使在有小区间同信道干扰情况下,通过简单的小区布置,多载波CDMA蜂窝系统下行信道就可以有很大的信道容量。     

Iterative interference cancellation and channel estimation in multibeam satellite systems

This paper deals with the use of non‐linear multiuser detection techniques to mitigate co‐channel interference on the reverse link of multibeam satellite systems. These techniques allow more capacity efficient frequency reuse strategies than classical ones, as they make possible to cope with lower C/I. The considered system takes as a starting point the DVB‐RCS standard, with the use of convolutional coding, and the use of the Ka‐band. We propose different iterative interference cancellation schemes, which operate at the beamformer outputs, and which use information from decoders. The proposed receivers assume an initial single‐user synchronization step: frame synchronization and timing recovery, and then perform channel estimation: beamformer coefficients; signal carrier phases and signal amplitudes. In a first step, these receivers are evaluated by simulation in terms of bit error rate and of channel estimation error on two interference configurations. For one of these receivers, sensitivity to imperfect timing recovery and to low‐frequency offsets from user terminals is evaluated. In a second step, since the receiver performances highly depend on the interference configuration, we propose an approach to evaluate performances on a multibeam coverage (by taking into account the variability of interference configurations on the coverage). This method is used to compare different receivers on an example based on a coverage designed on a digital focal array feed reflector antenna. Copyright © 2007 John Wiley & Sons, Ltd.     

Robust blind PIC with adaptive despreader and improved interference estimator

An effective design of multistage parallel interference cancellation (PIC) receiver using blind adaptive (BA) despreader and pre‐respreader interference estimator for uplink CDMA is proposed and analysed. A novel algorithm is designed, which exploits constant modulus (CM) property of the users' transmitted signals and inherent channel condition to perform adaptive despreading based on minimum error variance criteria. This is carried out by BA weighting of each chip signal for accurate tracking of the desired user's signal power and hence for more improved data detection at the output of each stage of PIC. Furthermore, the despreader weights are used within the adaptive pre‐respreader interference estimation and cancellation to obtain online scaling factors during every symbol period, without any knowledge of users' channels or the use of training sequences. It is found that this way of estimation is optimal in minimum mean squared error sense, and hence, significant reduction in interference and noise variance is observed in detection and estimation of the desired users' signals compared with conventional PIC. Bit error probability of the proposed PIC is obtained using Gaussian Approximation method. Extensive simulation results are shown, which demonstrate impressive performance advantage in fading environments, high system loading, and severe near far conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

MIMO系统中基于混合干扰消除的低复杂度迭代接收

针对MIMO(多输入多输出)通信系统中传统的基于软干扰消除和MMSE(最少均方误差)滤波器的迭代接收方案对信道相关性较敏感的问题。提出了一种基于混合干扰消除(软干扰消除和硬干扰消除)以及MMSE滤波器的检测算法,并引入一个确信机制来控制错误传播问题。仿真结果表明,新算法相比传统的算法在相关信道环境下有明显的性能增益。定性的计算复杂度分析表明新算法在恰当的系统配置下比传统算法具有更低的计算复杂度。     

联合均衡块迭代软判决反馈干扰抵消接收机

CDMA扩频通信系统在低扩频比时,路径间干扰(IPI, inter-path interference)变得非常严重。本文将块迭代干扰抵消同MMSE均衡器相结合,提出了一种适用于CDMA扩频通信系统低扩频比情况下的联合均衡块迭代软判决反馈干扰抵消(MMSE-BIIC)接收机结构。理论分析与计算机仿真表明,本文提出的MMSE-BIIC接收机同传统的Rake接收机、线性MMSE均衡器以及多级干扰抵消接收机相比在性能上有较大改善。     

基于加权的FBMC系统信道估计新算法

具有高频谱效率和低带外衰减的滤波器组多载波传输/偏移正交幅度调制(FBMC/OQAM)系统由于仅满足实数域正交条件,在实际应用中固有干扰严重影响信道估计(CE)性能.基于干扰消除的算法可以通过设计合理的导频结构消除导频周围固有干扰的影响,该类方法简单,但是信道估计的性能容易受到噪声的影响.块状导频结构的子载波之间具有比较强的相关性,导致信道估计结果中存在冗余信息.为了利用这些冗余信息,提出一种估计值加权的新算法,以提高信道估计的性能.仿真结果表明,新算法的误码率性能明显优于传统算法.     

Channel estimation and interference suppression for uplink CDMA mobile communication systems

Wireless communications for mobile telephone and data transmission is currently undergoing very rapid development. Code division multiple‐access (CDMA) implemented with direct sequence spread spectrum signaling is among the most promising multiplexing technologies for cellular telecommunications services. In this paper, jointly period inserted pilot symbols assisted recursive (PIPSAR) channel estimation and interference suppression techniques are proposed for uplink CDMA mobile communication systems. The uplink CDMA mobile communication system model is described in the form of space‐time domain through antenna array and multipath expression. Interference suppression is achieved by using adaptive minimum mean squared error (MMSE) digital filters that span several successive received chip oversampling vectors of a symbol interval. PIPSAR techniques are used to estimate channel parameters. The correlation between the successive periods is considered to further improve the performance of the proposed scheme. Analysis and simulations are used to evaluate the performance of the proposed scheme. Copyright © 2004 John Wiley & Sons, Ltd.     

Narrow‐band interference suppression in wavelet packets based multicarrier multicode CDMA overlay system

The wavelet packets based multicarrier (MC) multicode (MCD) code‐division multiple‐access (CDMA) transceiver consists of the MCD part, which ensures the transmission for high speed and flexible data rate; the MC part contributing to robustness to frequency‐selective fading and flexibility for handling multiple data rates; and wavelet packets (WPs) modulation technique, which contributes to the mitigation of the interference problems. As WPs have lower sidelobes compared with sinusoidal carriers, this system is very effective in reducing the problem of inter‐carrier interference. Of course, like any CDMA system, the system can suppress a given amount of interference. This paper considers an interference suppression scheme which will enhance the performance of the system. The receiver employs suppression filters to mitigate the effect of narrow‐band jammer interference. The framework for the system and the performance evaluation are presented in terms of the bit error rate and the outage probability over a Nakagami fading channel. Also, we investigate how the performance is influenced by various parameters, such as the number of taps of the suppression filter and the ratio of narrow‐band interference bandwidth to the spread‐spectrum bandwidth. Finally, the performance of the system is compared with the performance of sinusoidal based MC/MCD‐CDMA system denoted Sin‐MC/MCD‐CDMA. Copyright © 2012 John Wiley & Sons, Ltd.     

一种低复杂性的自适应干扰消除接收机方案

本文提出一种适用于码分多址系统的低复杂度自适应干扰消除接收机。 在此接收机中，我们首先基于第i个用户的第m个比特的输出引入一组可靠度因子 ，然后根据这组可靠度因子估算出多址干扰，最后通过执行干扰消除可得到符号判决值。通过在加性高斯白噪声信道和多径衰落信道中进行仿真。结果表明，本文提出的这种接收机方案的性能优越于传统检测器和一些已经存在的干扰消除算法，同时保持有较低的算法复杂度。     

Interference cancellation for a multicellular CDMA environment

This paper considers the performance of adaptive interference cancellation applied to a CDMA microcellular environment, by employing a circular cell geometry and a closed form expression for the Bit Error Rate of a CDMA system with interference cancellation to analyze the effect of out-of-cell interference. Results are presented which indicate that out-of-cell interference will severely limit the benefits of interference cancellation in a multicellular system. Attempts to cancel all out-of-cell interference will further degrade performance. However, the use of selective interference cancellation in which only the strongest out-of-cell interferers are cancelled may result in significant performance enhancement. These results agree closely with those obtained using a hexagonal geometry.Portions of this paper have been presented at the PIMRC'95 conference in Toronto, Canada.