Interleaving scheme for multicarrier CDMA system

In MultiCarrier Code-Division Multiple-Access (MC-CDMA) system,the received signals scattered in the frequency domain are combined to get frequency diversity gain.However,the frequency diversity gain is limited because of correlation between subcarriers.A novel interleaving scheme for MC-CDMA system is proposed in this paper.A circular shifting register is introduced into each subcarrier branch to decrease the correlation between subcarriers.By using interleaving,frequency diversity gain of system is increased.System structure and model with interleaver are discussed.In the case of multiple users,Parallel Interference Cancellation (PIC) technique is also introduced.Computer simulations demonstrate the performance of proposed scheme,and the performance comparison of MC-CDMA with interleaver and conventional MC-CDMA system is shown as well.     

Single tone jamming elimination scheme of multicarrier spread spectrum system

The proposed scheme is based on Discrete Fourier Transform (DFT) domain processing. The key technology of this scheme is jamming parameters‘ accurate estimation and jamming reconstruction. Compared with the “threshold exciser”scheme.the proposed scheme can eliminate more jamming energy on the whole frequency band with the minimum loss of useful signal energy. As shown in the research and simulation, the proposed scheme is much better than the “threshold exciser” scheme, especially in the case of high power jamming whereas the “threshold exciser” scheme might be invalid.     

Transmit power allocation in SVD equalized multicarrier systems

Transmit power allocation and bit loading are important issues in multicarrier transmission via frequency-selective channels. In this contribution, transmit power allocation schemes for BER performance improvements in a wavelet-based multicarrier transmission system with Singular-value decomposition (SVD) equalization are investigated under the constraint of a limited total transmit power. Contrary to other contributions, here the transmit power is not only adapted to the subchannels but rather to each symbol of the SVD equalized data block individually. Based on the Lagrange multiplier method, different solutions are investigated, whereby optimal but complex and suboptimal but efficient schemes are analyzed. In order to obtain numerical results, the schemes are exemplarily applicated to a time-invariant and to different time-variant channels with Rayleigh and Rice distributed path coefficients, respectively.     

Simple method for intermodulation products counting in multicarrier systems

This paper presents a novel algorithm for intermodulation products counting in multicarrier systems. Intermodulation products are caused by the nonlinearity of the amplifiers’ transfer characteristic. Along the transmission network, broadband amplifiers are needed to boost up the signal level and compensate the signal attenuation. When the number of carriers increases, the number of intermodulation products also increases extremely fast. In our approach, selective counting procedure by grouping intermodulation products was introduced. The presented solution shows considerable reduction in computational effort in counting the number of intermodulation products in the individual channel, especially if the number of products is very large.     

MC-CDMA系统的可视化仿真研究

基于多载波并行传输的CDMA技术以其具有诸多的优点正受到人们的广泛关注，已成为移动通信系统研究中的一个热门课题，该文基于交互式图形建模技术，针对多载波传输机理，研究了MC－CDMA系统的图形建模及可视化仿真问题，并给出了系统仿真结果。     

Performance of Multicarrier CDMA Rake System over Rayleigh Fading Channel

Based on the theory of multicarrier (MC) technique and the Rake receiver, a multicarrier DS-CDMA Rake system is proposed, where a data sequence multiplied by a spreading sequence modulates multiple carriers. The receiver provides a Rake for each subcarrier, and the outputs of the Rakes are combined by a maximal-ratio combiner. The average probability of error of the system is derived from an uncorrelated subcarrier and frequency-selective fading channel model. The system performances are evaluated over Rayleigh fading channel with an exponential multipath intensity profile(MIP) and with a rectangular MIP, respectively, when multipath interference is present. It is found that this kind of model has larger superiority in an exponential MIP than in a rectangular MIP.     

AD6654在cdma2000多载波数字中频接收机中的应用

建立多信道软件无线电接收机数学模型,介绍了ADI公司的高性能宽带多载波数字中频接收芯片AD6654电路结构和主要特性。在此基础上提出一种数字中频在cdma2000多载波接收系统的设计及应用方案,并给出了系统各个单元的设计和性能参数,最后仿真验证了方案的可行性。     

一种基于多载波的多播系统物理层安全方案

受限于发送方天线数目,无线多播系统整体信道通常不存在零空间,无法利用传统的物理层安全技术保证其安全传输。针对这一问题,该文提出一种基于多载波的多播系统物理层安全方案。首先,建立了多载波多播系统物理层安全通信模型;之后,通过分配载波产生合法用户的信道零空间,在零空间内引入人工噪声保证系统的安全传输;最后,以最大化保密传输速率为目标,在系统总功率受限情况下,利用Kuhn-Tucher条件对各子载波功率进行了优化。仿真结果表明:该方案不受限于发送方天线数目,并且所提功率分配方法的系统保密传输速率比等功率分配方法提升约2 bit/(s Hz)。     

一种新的正交多载波CDMA系统

该文提出了一种新的多载波码分多址(MC-CDMA)系统。与传统的MC-CDMA系统相比,其主要区别是要发送的数据比特先串并转换为多个并行分支,每一个分支用一组正交子载波进行调制。在每个分支上,使用相同扩频序列的不同码片调制子载波。这种系统能更有效地利用传输带宽,实现频率分集。由于该系统降低了每个子载波上的数据速率,扩频序列更容易同步。最后给出了在瑞利衰落信道下的性能分析。