Blind Channel Estimation for Multi-Rate Multicarrier DS/CDMA Communications

Multi-rate multicarrier DS/CDMA is a potentially attractive multiple access method for future wireless communications networks that must support multimedia, and thus multi-rate, traffic. Several receiver structures exist for single-rate multicarrier systems, but little has been reported on multi-rate multicarrier systems. Considering that high-performance detection such as coherent demodulation needs the explicit knowledge of the channel, based on the finite-length chip waveform truncation, this paper proposes a subspace-based scheme for timing and channel estimation in multi-rate multicarrier DS/CDMA systems, which is applicable to both multicode and variable spreading factor systems. The performance of the proposed scheme for these two multi-rate systems is validated via numerical simulations. The effects of the finite-length chip waveform truncation on the performance of the proposed scheme is also analyzed theoretically.     

Multi-rate sensor fusion-based adaptive discrete finite-time synergetic control for flexible-joint mechanical systems

This paper proposes an adaptive discrete finite-time synergetic control （ADFTSC） scheme based on a multi-rate sensor fusion estimator for flexible-joint mechanical systems in the presence of unmeasured states and dynamic uncertainties. Multi-rate sensors are employed to observe the system states which cannot be directly obtained by encoders due to the existence of joint flexibilities. By using an extended Kalman filter （EKF）, the finite-time synergetic controller is designed based on a sensor fusion estimator which estimates states and parameters of the mechanical system with multi-rate measurements. The proposed controller can guarantee the finite-time convergence of tracking errors by the theoretical derivation. Simulation and experimental studies are included to validate the effectiveness of the proposed approach.     

LTE系统中多速率采样滤波器的设计

在LTE（long term evolution）系统中对OFDM基带信号采样进行数字化处理时,随着系统带宽变化,采样速率也随之变化,但是根据协议,发送端采样速率固定,此时需要对信号进行过采样。通过对滤波器的分析比较以及仿真设计,得出结论,LTE系统中可以使用半带滤波器实现信号的过采样。     

软件无线电接收机多速率信号的多段处理方法研究

在软件无线电数字接收机中，为了支持多种速率的信号处理，通常采用分数倍重采样，在硬件实现时，非常耗时和耗资源，这也成为软件无线电数字接收机的难点。在分析传统实现模型的基础上，提出一种基于整数倍重采样的新方法，即按照一定的分段方法，实现多速率的多段动态处理，可以避免分数倍重采样，节省运算时间和硬件资源。通过Matlab仿真证明，该方法性能良好，实用可行，可以用于数字接收机的多速率处理系统，在其工程实现上有较大的参考意义。     

米波雷达射频数字化接收机抗干扰设计

米波雷达由于其频段反隐身以及不在反辐射导弹制导频段内等优势近年来得到了飞速发展和广泛应用,但是由于米波频段内充斥作广播电视等通信干扰信号,因此接收机抗干扰设计是米波雷达面临的一个巨大挑战。文中给出了基于频域的多级滤波技术以及基于射频数字化采样时钟优化选择的接收机外界干扰抑制方法,该方法可有效地抑制米波雷达接收机工作频带外以及频带内的干扰信号,并可应用于米波雷达射频数字化接收机的设计中。     

流媒体文件多码率自适应处理系统研究

为了应付流媒体系统应用网络带宽不足问题,设计了基于多码率文件传输技术和可变编解码参数Filters播放链路动态重连机制的自适应流媒体传输系统。该系统在网络带宽发生波动的条件下,能够自适应地选择与可用带宽相匹配码率的视频数据进行动态传输,进而减少视频数据缓冲等待次数和等待时间,有效提高网络带宽利用率和媒体内容服务质量,同时采用"最短"的链路进行媒体内容的动态重连,避免Filters动态重连中出现"卡塞感",有效提高流媒体系统的服务质量。     

Impact of Polarization Mode Dispersion in Multi-Hop and Multi-Rate WDM Rings

Fiber polarization mode dispersion (PMD) is perhaps the most critical transmission impairment in optical networks at transmission rates of 10 Gb/s and higher. Since the bandwidth-distance product, or transparency,of the optical circuit is limited by PMD, the overall network design and cost may be significantly altered by the actual fiber PMD values. The paper has three objectives. First, an accurate model for evaluating the PMD effects is presented and verified experimentally. Second, the cost increase of WDM rings due to PMD in a number of design scenarios—first generation, single-hop,multi-hop, and multi-rate networks—is assessed. Third, the polynomial-time algorithm proposed in Cerutti et al. [1] is modified to provide sub-optimal solutions for the above WDM rings, taking into account the limited bandwidth-distance product imposed by PMD. Presented results reveal that at high transmission rates, the cost of the multi-hop ring is less affected by PMD than the costs of first generation and single-hop rings.     

多码率多边类型LDPC码译码器的设计与实现

提出了一种固定码长的多码率多边LDPC码译码器,该译码器采用对校验比特信息进行间隔删余的算法实现其多码率译码,并设计了一种适合多码率多边LDPC码的部分并行译码结构。基于该结构在FPGA平台上实现了码长为640 bit,码率为0.5～0.8的多边LDPC码译码器。     

ATSC标准中8-VSB调制器的算法改进及FPGA设计实现

重点介绍了ATSC标准的8-VSB系统构架以及FPGA系统的具体实现方案.根据具体标准的参数要求,分析了ATSC标准.基于改进的维弗法,提出了频率范围可变的低中频数字信号输出解决方案,给出了系统硬件的设计步骤,并给出实测结果.     

基于TMS320F2812的多通道实时语音编解码

介绍了自适应多码率语音编解码算法及其基于TMS320F2812定点DSP芯片的实现方案。利用TMS320F2812芯片集成的多路ADC和PWM,对方案进行了多通道的扩展。分析了在DSP芯片上实现实时语音编解码及多通道扩展的关键技术。最后分析了此多通道实时语音编解码方案所需的存储空间和计算复杂度。