载波误差对MC-CDMA系统性能的影响

该文对下行无线通信信道中MC-CDMA系统的载波误差性能进行了研究。对接收判决器的输入信噪比(SNR)和判决误码率(BER)进行了详细的理论分析和数值模拟。结果表明,MC-CDMA对载波频率偏移十分敏感,系统性能随载波数量的增加而迅速下降;在最大载荷下,载波相位抖动导致的性能下降与载波数无关。     

长线电缆数字基带传输中自适应均衡器的设计

长线电缆受实际工作环境的影响非常大.各种因素都会引起传输信号的幅度和相位失真,采用自适应均衡技术可解决信道失真的问题.采用RLS算法求解均衡器的系数.最后通过仿真和测试结果,分析了均衡性能.     

一种改进的MC／CDMA系统的性能分析

多载波扩展频谱码分多址系统（MC／CDMA）是一种消除符号间干扰的有效技术。在多径传输信道下,考虑到各用户服务指标（QoS）的不同,本文提出多用户MC／CDMA系统可采用自适用最佳子载波分配方案。理论分析和仿结果表明,采用本文所提出的方案时,传统的MC／CDMA系统的性能将得到明显的改善。     

Performance Investigation of Space‐Time Block Coded Multicarrier DS‐CDMA in Time‐Varying Channels

In this letter, we evaluate the system performance of a space‐time block coded (STBC) multicarrier (MC) DS‐CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS‐CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS‐CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.     

宽带无线TDMA系统的自适应调制技术

无线多媒体业务的快速增长促进了宽带无线ＴＤＭＡ通信系统的研究和开发,宽带无线ＴＤＭＡ通信系统方面出现了一些新的技术和系统设计概念。讨论宽带无线ＴＤＭＡ系统中采用的自适应调制技术。     

广义多载波CDMA技术研究

本文描述了几种不同的多载波CDMA技术 ,并将这几种技术统一成一种格式 ,这被称为广义多载波CD MA ,并给出了仿真结果     

判决反馈均衡器结构及LMS算法研究

数字通信系统中多径衰落的无线信道环境通常会使接收信号受到严重的码间干扰。自适应均衡可以校正信道产生的畸变。文中介绍了基于LMS算法的自适应均衡器的原理和结构,在给定的信道模型下利用MAT- LAB工具对其收敛速度和精度进行仿真,结果表明在无线通信中,判决反馈均衡器比线性均衡器有更好的效果。     

CDMA2000下行接收技术研究--一种改进的带自适应存储的RLS算法

在下行链路中,接收机必须克服多径衰落等信道环境的负面影响,同时收端只想解调所期望用户的信号,抑制由其他用户引起的干扰,此外接收机也需要较低的运算量.本文对Rake接收和两种次优线性多用户检测（DD和MMSE）算法进行了研究和性能比较.在综合考虑了各种接收算法优缺点的基础上提出了一种改进的带自适应存储的RLS多用户接收算法,并对这种算法做了分析和性能仿真.仿真结果表明在相同指标和减少运算量的情况下,该算法可以得到比次优MMSE算法近2 dB左右的增益,系统的性能得到了提高.     

无线宽带数据传输中多载波CDMA系统的性能

在分析同步多载波CDMA系统基带发射、接收模型和多径衰落信道模型的基础上,提出一种新颖的误码率分析方法。对系统在瑞利(Rayleigh)衰落信道中的误码性能进行了理论研究,得到了BPSK调制条件下的系统误码率表达式。数值分析结果表明:多载波CDMA在无线宽带数据传输中性能大大优于CDMA,具有良好的应用前景。     

基站阵列接收方案的一种盲自适应算法

本文主要叙述了一种基站阵列接收方案中的盲自适应算法。在此算法中,我们使用一般的信息位作为训练信号来实现智能天线权值的更新。本方法的贡献在于,和导频位辅助LMS—DRMTA算法一样比传统的LS—DRMTA算法大大降低了运算量,同时该算法比导频位辅助LMS—DRMTA算法获得了更好的误码率、系统容量以及更好的波束图。     

BER Performance of Wireless BPSK Communication System in Tunnels With and Without Traffic

The bit error rate (BER) performance for high-speed personal communication service in tunnels with and without traffic is investigated. The impulse responses of tunnels for any transmitter–receiver location are computed by shooting and bouncing ray/image techniques. By using the impulse responses of these multipath channels, the BER performance of BPSK (binary phase shift keying) system with phase and timing recovery circuits are calculated. Numerical results have shown that the multipath effect by the vehicles in the tunnel is an important factor for BER performance. In addition, the effect of space diversity techniques and decision feedback equalizer on mitigating the multipath fading is also investigated.Chien-Hung Chen was born in Kaohsiung, Taiwan, Republic of China, on 8 March 1971. He received the MSEE degree from Tamkang University in 1999. He is studying for Ph.D. degree in the Department of Electrical Engineering, Tamkang University. His current research interests include indoor wireless communications and numerical techniques in electromagnetics.Chien-Ching Chiu was born in Taoyuan, Taiwan, Republic of China, on 23 January 1963. He received the BSCE degree from National Chiao Tung University, Hsinchu, Taiwan, in 1985 and MSEE and PhD degrees from National Taiwan University, Taipei, Taiwan, in 1987 and 1991, respectively. From 1987 to1989, he served in the ROC Army Force as a communication officer. In 1992 he joined the faculty of the Department of Electrical Engineering, Tamkang University, where he is now an Professor. He was a visiting scholar at the MIT and University of Illinois, Urbana from 1998 to 1999. His current research interests include microwave imaging, numerical techniques in electromagnetics and indoor wireless communications.Shi-Cheng Hung received the MSEE degree from Tamkang University in 1998. He is now a RF engineer. His current research interests include indoor wireless communications and numerical techniques in electromagnetics.Chien-Hung Lin received the MSEE degree from Tamkang University in 2001. He is now a RF engineer. His current research interests include indoor wireless communications and numerical techniques in electromagnetics.     

基于DDLMS算法的信道均衡器的FPGA实现

无线通信系统中均衡技术是改善信道特性解决码间干扰的有效方法.从分析判决引导最小均方误差算法(DDLMS)算法出发,研究了其在信道均衡技术上的应用,并通过Matlab仿真和软件(Xilinx System Generator for DSP)开发软件在FPGA上实现了一个基于DDLMS算法的基带均衡器.从仿真测试结果可以...     

Low‐Power‐Adaptive MC‐CDMA Receiver Architecture

This paper proposes a novel concept of adjusting the hardware size in a multi‐carrier code division multiple access (MC‐CDMA) receiver in real time as per the channel parameters such as delay spread, signal‐to‐noise ratio, transmission rate, and Doppler frequency. The fast Fourier transform (FFT) or inverse FFT (IFFT) size in orthogonal frequency division multiplexing (OFDM)/MC‐CDMA transceivers varies from 1024 points to 16 points. Two low‐power reconfigurable radix‐4 256‐point FFT processor architectures are proposed that can also be dynamically configured as 64‐point and 16‐point as per the channel parameters to prove the concept. By tailoring the clock of the higher FFT stages for longer FFTs and switching to shorter FFTs from longer FFTs, significant power saving is achieved. In addition, two 256 sub‐carrier MC‐CDMA receiver architectures are proposed which can also be configured for 64 sub‐carriers in real time to prove the feasibility of the concept over the whole receiver.