一种新的应用于多载波码分多址系统的干扰对消算法

本文提出了一种适用于多载波直扩码分多址系统(MC-DS-CDMA)上行信道的低复杂度部分并行干扰对消(LC-PPIC)算法.该算法充分利用MC-DS-CDMA系统的信道估计与子载波分集,在各个子载波上将用户分为可靠,普通和无效三类,对可靠用户进行干扰对消处理并消去后,再对普通用户进行相同操作,并放弃无效用户,最后将各个子载波上的结果通过最大比合并(MRC)输出.这样,在降低运算复杂度的同时,更好地抑制了多址干扰(MAI).通过仿真比较,可以看出LC-PPIC算法的误码率(BER)性能明显优于置于载波合并前后的两种部分并行干扰对消(PPIC)算法,特别是在系统负载较重和信噪比较高的情况下,这种优势十分显著.     

一种新的多用户多速率自适应MC-DS-CDMA传输方案

从有效利用网络资源的角度出发,结合OFDMA的动态资源分配策略,提出了一种灵活支持多用户多速率业务的改进MC-DS-CDMA传输方案--自适应MC-DS-CDMA系统。仿真结果表明,自适应MC-DS-CDMA系统由于采用了多用户自适应的子载波分配策略,不仅可灵活支持多速率业务,而且能降低系统的发射总功率,进一步改善了系统性能。     

基于导频的MC-DS-CDMA系统载波频偏估计

针对多载波直扩码分多址(MC-DS-CDMA)系统上行链路提出一种基于导频的多用户载波频偏估计算法:利用频偏向量的低通特性设计了一种新的梳状导频传输方案,从而在接收端的各用户的导频子载波上近似获得单用户信号,利用相位角平均法对该信号前后相邻两项的商的幅角取平均值,得到了效果较好的多载波频偏估计值;并进一步采用了傅立叶变换法来进行多载波频偏估计,提高了算法的抗干扰性能.仿真实验结果表明:相位角平均法在用户数较少(<3)和信噪比较高(>15dB)时的频偏估计误差均值能达到1%以下;而傅立叶变换法在多用户情形和较低信噪比(<5dB)下对较大归一化频偏范围(-0.5,0.5)内的频偏估计误差均值仍能保持在0.1%.提出的算法适合于在频率选择性衰落的慢变信道中对细频偏进行估计.     

一种白适应比特分配的多速率MC—DS—CDMA

文中从充分利用信道分集特性的角度出发,给出了自适应调制技术在MC—DS-CDMA系统中的应用,提出了一种支持多速率业务的改进的MC-DS-CDMA传输方案。并在预知信道状态的前提下,对固定调制方式和采用了自适应调制的两种方案的误比特性能进行了仿真和比较,结果表明该算法与传统系统相比系统误比特性能有很大提高。     

DFT-SV-OFDM based adaptive multi-rate DFT scrambling vector code division multiple access

Multipath interference would degrade the performance of multi-rate systems based on OFDM and CDMA,which spectrum efficiency was also lower relatively.To improve the performance and spectrum efficiency,a novel adaptive multi-rate DFT scrambling vector multi-carrier CDMA (AMR-DFT-VMC-CDMA) was proposed based on the theory of matrix permutation and r-cyclical matrix decomposition characteristics.Meanwhile,by theoretical analysis,the parameters of the system could be adaptively adjusted to ensure frame length long enough to break the restriction between channel bit error rate and data frame length on a certain channel utilization condition.The simulation results show that compared with the traditional multi-rate,multi-subcarrier and spreading system,the new system could achieve multi-rate and multi-user information transmission flexibly with better performance and better spectrum efficiency in fading channels.Moreover,it can satisfy the requirement of frame length under certain channel utilization by adjusting the parameters.     

The Impact on Channel Correlation for MC-DS-CDMA System in Small-Scale Fading Environments

In this research, the performance of an multi-carrier direct-sequence coded-division multiple-access (MC-DS-CDMA) system working in Nakagami fading channels with correlation characteristics is studied. In order to avoid the difficulty of explicitly obtaining the probability density function (pdf) for the signal-to-noise ratio (SNR) at the output of RAKE receiver, there is a pdf with the sum of Gamma will be varieties is applied in the derivative for bit error rate (BER) performance. Two cases, single- and multiple-user will be exemplified for validating the fact that the performance degradation of the MC-DS-CDMA is sensitive to the correlation coefficient of the fading channels. Besides, the assumption of partial band interference (PBI) between the subcarriers is considered in this evaluation.     

一种新型UWB信号的抗干扰性能研究

着眼于抗干扰通信的军事应用研究,通过对UWB MC-DS-CDMA的分析改进,得到了一种新型应用于超短波的UWB信号,分析了该信号的抗干扰性能,并与UWB MC-DS-CDMA信号进行了比较,然后使用安捷伦公司的ADS仿真软件进行了仿真验证,得出了该新型UWB信号具有极强的抗干扰性能的结论。     

Rayleigh衰落信道下天线阵MC-DS-CDMA系统的 空频盲自适应接收算法

讨论了天线阵多载波直接序列码分多址(MC-DS-CDMA)系统的信号接收.提出了一种基于最大信噪比准则的空频盲自适应算法(SFBA),对其性能进行了分析.该算法无需信道先验信息和训练序列,而是利用CDMA信号自身的结构特点实现频域和空域的联合接收,有效抑制干扰和噪声,提高信噪比,实现最佳接收.在AWGN和Rayleigh衰落信道下的仿真结果表明,该算法简单有效,且具有抗远近效应的能力.     

汉明码在多载波CDMA系统中的应用

本文讨论了GMC-CDMA技术。GMC-CDMA提供了全数字、统一的结构，包含了单载波和多载波CDMA系统。然后，本文用信道编码对GMC-CDMA技术改进，采用在GMC-CDMA系统前先进行蝙码采确保低误码率。仿真结果会表明：经过编码后的系统能取得更低的误码率。图像在编码的GMC-CDMA和未编码的GMC—CDMA两个系统中的不同传输效果进一步验证了这一结论。     

Zero intermediate frequency receiver for multicarrier mode of cdma2000

This paper proposes a novel zero Intermediate Frequency (IF) receiver for MultiCarrier (MC) Direct-Sequence Code-Division Multiple Access (DS-CDMA) based on multicartier mode of cdma2000 system.The proposed receiver employs direct RF-to-baseband downconversion,sampling at a rate equal to the bandwidth of the baseband multicarrier signal and complex-valued coefficient FIR filters.This receiver avoids the need for arrays of high Q analog bandpass filters,has a much lower sampling rate half of that of conventional receiver and offers significant savings in hardware implementation.Analytic and simulation results show that the presented receiver performs well for both the AWGN channel and Rayleigh fading channel.