共查询到20条相似文献,搜索用时 0 毫秒
1.
Xiangbin Yu Xiaodong Zhang Dazhuan Xu Guangguo Bi 《Wireless Personal Communications》2007,41(2):193-206
In this paper, the multiband complex wavelet used as multi-carrier basis function is optimized. On the basis of analyzing
the principle of multi-carrier code division multiple access (MC-CDMA), a new multiband complex wavelet based MC-CDMA (MBCW-MC-CDMA)
system model is proposed, and space diversity combining (SDC) technique is employed to improve the system performance further.
The uplink performance of proposed MBCW-MC-CDMA system with SDC technique is investigated in Rayleigh fading channel, and
corresponding bit error rate (BER) analysis is given in detail. Without any cyclic prefix (CP), the system can avoid the decrease
of spectrum efficiency and data rate of conventional MC-CDMA with CP. By comparison, our scheme outperforms real wavelet packet
based MC-CDMA and slightly outperforms conventional MC-CDMA with CP via utilizing superior properties of the optimized multiband
complex wavelet. Theoretical analysis and simulation result show that the application of SDC technique can improve the proposed
system ability to combat spatial fading and various interferences effectively. Moreover, the proposed system based on SDC
technique has superior BER performance over conventional DFT and SDC based MC-CDMA system and real wavelet packet and SDC
based MC-CDMA system.
Xiangbin Yu received the M.S degrees in Communication and Information Systems from Hohai University, Nanjing, China, in 2001; and his
Ph.D. in Communication and Information Systems in 2004 from National Mobile Communications Research Laboratory at Southeast
University, China. Now he is working as a Postdoctoral Researcher in Information and Communication Engineering Postdoctoral
Research Station at Nanjing University of Aeronautics and Astronautics, Nanjing, China. His research interests include multi-carrier
digital communication, space-time coding and digital signal processing in modern communications.
Xiaodong Zhang received the M.S degrees from Nanjing University of Posts and Telecommunications, Nanjing, China, in 1998. In 2002, he received
the Ph.D. degree from Southeast University, Nanjing, China. His research interests include contemporary signal processing
and digital communications.
DaZhuan Xu received the M.S degrees and Ph.D. in Communication and Information Systems from Nanjing University of Aeronautics and Astronautics
in 1986 and 2001, respectively. He is now a full professor in Nanjing University of Aeronautics and Astronautics, Nanjing,
China. Prof.Xu is a Senior Member of China Institute of Electronics (CIE). His research interests include digital communications,
soft radio, coding theory, medical signal processing.
Guangguo BI was graduated from Nanjing Institute of Technology, Nanjing, China, in 1960. He is now a professor in the Department of Radio
Engineering of Southeast University, Nanjing, China. Prof.Bi is a fellow and a member of the board of Director of the China
Institute of Communications, and a senior member of IEEE. His research interests include digital communications, personal
communications network, spread spectrum communications, and intelligent information processing. He has published more than
200 papers in above areas. 相似文献
2.
3.
要:建立了室内可见光通信系统模型,针对其信道冲击响应,分别采用最小二乘(LS)估计方法和最小均方差(MMSE)估计方法对信道进行了理论分析,并且通过计算机仿真,对两种不同的估计方法性能进行了比较,最后在此基础上,分别对抽头长度和训练序列长度对信道估计的性能影响进行了仿真验证。实验结果表明:在相同信噪比下,MMSE方法的性能优于LS方法,但是计算量比LS方法复杂,而且LS方法性能依赖于噪声的影响,信噪比越高,LS估计方法的性能越好。同时抽头数越多,训练序列越长,信道估计的性能越好,但也会增加计算的复杂度。 相似文献
4.
多速率超宽带通信系统中天线传输性能的研究 总被引:1,自引:0,他引:1
利用实验测量结合数值仿真的方法,研究了特定室内环境中,不同形状超宽带单极子天线对不同速率多带正交频分(MB-OFDM)超宽带通信系统传输性能的影响.仿真与实验中,MB-OFDM平台采用MATLAB的simulink工具实现,天线与传播环境构成的广义信道特性则通过矢量网络分析仪进行测量.结果表明,单极子天线形状对不同速率MB-OFDM系统的传输误比特率性能有显著影响,文章的方法可用于多速率超宽带通信系统收发天线的优选和性能评价. 相似文献
5.
Performance Analysis of Multiuser Detectors for Uplink Quasi-synchronous MC-CDMA Systems 总被引:1,自引:1,他引:1
Felip Riera-Palou Guillem Femenias Jaume Ramis 《Wireless Personal Communications》2007,43(4):1511-1521
This paper analyses and compares the average bit error rate (BER) of different multiuser detectors (MUD) in the uplink of
a multicarrier code- division multiple access (MC-CDMA) system. In particular, maximum likelihood, zero-forcing, minimum mean-square
error and interference cancellation-based multiuser detectors have been analysed for the special case of uncorrelated subcarriers.
The derived BER expressions are based upon previous results on diversity combining and also on recent findings on multiple
input multiple output (MIMO) architectures. The subcarrier correlation is considered in the context of physical parameters
currently under discussion for future wireless systems to give an indication up to what extent the assumption of uncorrelated
subcarrier fading is plausible. 相似文献
6.
7.
8.
We consider the problem of downlink traffic control in Multi-code Code Division Multiple Access (MC-CDMA) systems, which support
multiple classes of services with diverse QoS requirements. Prior solutions proposed for this problem have largely focused
on call admission control at the connection level while neglecting the stochastic behavior of mobile subscribers and channel
conditions. We quantitatively demonstrate that these statistical factors, in particular log-normal shadowing in propagation
and voice activity factors, have a significant impact on the connection-level performance. Furthermore, we show that conventional
data services can be best handled at the packet level as background transmissions by taking advantage of these statistical
variations, which leads to significantly better utilization of the scarce wireless spectrum.
The research was supported in part by grants from RGC under the contracts HKUST6104/04E and HKUST6165/05E, a grant from NSFC/RGC
under the contract N_HKUST605/02, a grant from NSF China under the contract 60429202. Jihui Zhang’s work was partially supported
by Microsoft fellowship.
Jihui Zhang (S’02) received her B.S. degree from Fudan University, China in 2001, and the Ph.D. degree from the Hong Kong University
of Science and Technology in 2005, both in the Computer Science. Her research interests include CDMA cellular networks and
wireless ad-hoc networks.
Bo Li (S’89-M’92-SM’99) received his B. Eng. and M. Eng. degrees in the Computer Science from Tsinghua University, Beijing in 1987
and 1989, respectively, and the Ph.D. degree in the Electrical and Computer Engineering from University of Massachusetts at
Amherst in 1993. Between 1993 and 1996, he worked on high performance routers and ATM switches in IBM Networking System Division,
Research Triangle Park, North Carolina. Since 1996, he has been with the Department of Computer Science, Hong Kong University
of Science and Technology, where he is now an associated professor and Co-Director for the ATM/IP Cooperate Research Center,
a government sponsored research center. He also holds an adjunct researcher position at the Microsoft Research Asia (MSRA),
Beijing, China, and adjunct professorship in several universities.
His recent research interests are on adaptive video multicast, packet scheduling and dynamic routing in optical networks,
resource management in mobile wireless systems, scheduling and energy efficient routing in ad hoc networks, across layer design
for sensor networks, and content distribution and replication. He has published 150 papers and held several patents in above
areas. He has been on editorial board for 16 journals, mainly in IEEE and ACM. He has been involved in organizing over 40
conferences, esp. IEEE Infocom since 1996. He was the Co-TPC Chair for IEEE Infocom 2004. 相似文献
9.
本文介绍了一种将正交频分复用(OFDM)技术和码分多址(CDMA)技术相结合的多载波CDMA (MC-CDMA)系统,分析了MC-CDMA系统的发射端和接收端的结构,建立了MC-CDMA系统的信号模型,详细分析了MC-CDMA中的多址干扰形式,以及针对MC-CDMA系统的多用户检测原理,提出了一种基于最小误码率准则的多用户检测算法。理想的基于最小误码率准则的多用户检测算法在实际中难于实现,本文采用估计概率密度函数的方法,推导出了一种自适应实现的最小误码率多用户检测算法。仿真结果表明,该算法能够有效抑制多址干扰,降低误码率,同时,该算法还具有比基于最小均方误差准则的多用户检测器更低的误码率的优点。 相似文献
10.
相干光OFDM系统中MMSE信道估计研究 总被引:1,自引:1,他引:0
信道估计作为相干光正交频分复用(CO-OFDM)的 一种关键技术对系统的性能有着十分重要的影响。本文重点对系统信道估计的实现进行了数 学 分析,搭建起了CO-OFDM系统仿真平台,并在此平台上将提出的最小均方误差(MMSE)及其改进算法应用到CO- OFDM系统中进行信道估计。结果表明,MMSE及其改进算法能够很 好地提高CO-OFDM 系统的传输性能,在误码率(BER)为10-3时,与最小 二乘(LS)算法相比有约2dB的光信噪比(OSNR)增益,且改进型MMSE算 法的复杂度要比MMSE算法低2个数量级。 相似文献
11.
Performance of the Adaptive Cod- ing and Modulation (ACM) strongly depends on the retrieved Channel State Information (CSI), which can be obtained using the chan- nel estimation techniques relying on pilot sy- mbol transmission. Earlier analysis of methods of pilot-aided channel estimation for ACM systems were relatively little. In this paper, we investigate the performance of CSI prediction using the Minimum Mean Square Error (MMSE) channel estimator for an ACM system. To solve the two problems of MMSE: high compu- tational operations and oversimplified assum- ption, we then propose the Low-Complexity schemes (LC-MMSE and Recursion LC-MMSE (R-LC-MMSE)). Computational complexity and Mean Square Error (MSE) are presented to evaluate the efficiency of the proposed algo- rithm. Both analysis and numerical results sh- ow that LC-MMSE performs close to the well- known MMSE estimator with much lower com- plexity and R-LC-MMSE improves the appli- cation of MMSE estimation to specific cir- cumstances. 相似文献
12.
13.
14.
15.
Multi Carrier Code Division Multiple Access (MC-CDMA) is an appropriate modulation technique for high data rates. In this modulation scheme, employing of combining techniques are unavoidable for restoring orthogonality between different user signals. In this paper, the combining techniques of a MC-CDMA based on wavelet transform are studied. The partial combining of the wavelet based MC-CDMA system is suggested and its performance is compared with the maximum ratio combining (MRC), equal gain combining (EGC), orthogonality restoring combining (ORC) and the minimum mean square error (MMSE) techniques. Orthogonal filter banks of the wavelet transforms provide orthogonality between the wavelets and scaling functions, subcarriers and spreading sequences. Therefore, they provide new dimensions in combatting multipath fading, inter carrier interference (ICI) and narrowband interference in MC-CDMA systems. Furthermore, analysis of partial combining shows that coefficients of this technique can be computed in a simple manner. Simulations results indicate that the bit error rate (BER) performance of the proposed scheme is almost comparable with the MMSE combining scheme and the proposed system has a proper performance in terms of BER versus the signal to noise ratio (SNR) in frequency selective fading channels. 相似文献
16.
SVD-based MIMO Precoding and Equalization Schemes for Realistic Channel Knowledge: Design Criteria and Performance Evaluation 总被引:1,自引:0,他引:1
Multiple-input multiple-output (MIMO) based communication systems with precoding, bit-loading and equalization procedures
are considered in this paper. Applications of precoding schemes, which are based on Singular Value Decomposition (SVD) of
the channel matrix H assume almost always ideal channel knowledge at the transmitter and/or receiver site. This paper investigates an SVD based
MIMO approach considering non ideal radio channel estimation results. In any case the MIMO channel matrix H is decomposed into Eigenmodes. In case of an ideal radio channel knowledge the SVD based precoding procedure, which is applied
at the transmitter site, is going to consider all possible Eigenmodes which results in a perfect separation of all signals
at the receive antenna output and into a minimum bit-error-rate (BER). It will be shown in this paper that in case of non
ideal channel knowledge and a limited accuracy in the channel matrix H estimation a reduced number of Eigenmodes in the precoding process will become an optimum and will lead into an increased
BER performance.
相似文献
Hermann RohlingEmail: |
17.
18.
Wei Yang Junshi Chen Zhenhui Tan Shixin Cheng 《Wireless Personal Communications》2007,43(4):1351-1361
In this paper, a multicarrier code-division multiple-access (MC-CDMA) system employing antenna array at base station with
quaternary phase shift keying (QPSK) modulation is proposed. This receiver adopts a space-frequency two-dimensional (2-D)
Rake receiver structure. Based on the detailed analysis of the interference characteristics of the proposed system, the bit
error rate (BER) performance of the system is provided. With regard to spatial domain combining, the optimum and suboptimum
combining weight is derived, while the suboptimum set of weights is simplified on sense of that only the knowledge of array
vector of desired user alone is sufficient for the combining. Simulation results verify the analysis and show that better
performance is achieved for the proposed antenna array MC-CDMA system than the corresponding single antenna approach. 相似文献
19.
基于Chebyshev混沌扩谱序列的MC-CDMA系统的峰均功率比研究 总被引:1,自引:0,他引:1
峰均功率比(PAPR)是多载波码分多址 (MC-CDMA)系统的一个重要指标, OFDM多载波调制技术虽然可以提高MC-CDMA系统的数据传输率和抗干扰能力, 但是在系统的峰均功率比方面则存在着亟待解决的问题。本文利用Chebyshev混沌扩谱序列的伪随机、非周期、数量大和良好的相关特性,作为MC-CDMA系统上行信道的扩谱序列,以改善输出信号的峰均功率比。分析和仿真结果表明在保持较低多址接入干扰的同时,还可以大大降低发射信号的峰均功率比。 相似文献
20.
Least mean square (LMS)-based adaptive filters are widely deployed for removing artefacts in electrocardiogram (ECG) due to less number of computations. But they posses high mean square error (MSE) under noisy environment. The transform domain variable step-size LMS algorithm reduces the MSE at the cost of computational complexity. In this paper, a variable step-size delayed LMS adaptive filter is used to remove the artefacts from the ECG signal for improved feature extraction. The dedicated digital Signal processors provide fast processing, but they are not flexible. By using field programmable gate arrays, the pipelined architectures can be used to enhance the system performance. The pipelined architecture can enhance the operation efficiency of the adaptive filter and save the power consumption. This technique provides high signal-to-noise ratio and low MSE with reduced computational complexity; hence, it is a useful method for monitoring patients with heart-related problem. 相似文献