A Fast π/4-DQPSK Demodulation Arithmetic and Realization

The modulated signals of π /4-DQPSK can be demodulated with the differenced method,and the technology has been used in the communication. The traditional demodulated method needs a lot of calculation. In this paper, a new method based on fast arithmetic digital demodulation of DQPSK is presented. The new method only uses the sign of the modulated signal instead of digital signal through the A/D in the traditional method. With the new method, the system has higher speed, and can save some hardware in the FPGA. An experiment of the new method with the DQPSK is given in this paper.     

VLSI Implementation of Forward Error Control Technique for ATM Networks

In asynchronous transfer mode (ATM) networks, fixed length cells of 53 bytes are transmitted. A cell may be discarded during transmission due to buffer overflow or a detection of errors. Cell discarding seriously degrades transmission quality. The quality degradation can be reduced by employing efficient forward error control (FEC) to recover discarded cells. In this paper, we present the design and implementation of decoding equipment for FEC in ATM networks based on a single parity check (SPC) product code using very‐large‐scale integration (VLSI) technology. FEC allows the destination to reconstruct missing data cells by using redundant parity cells that the source adds to each block of data cells. The functionality of the design has been tested using the Model Sim 5.7cXE Simulation Package. The design has been implemented for a 5 ° 5 matrix of data cells in a Virtex‐E XCV 3200E FG1156 device. The simulation and synthesis results show that the decoding function can be completed in 81 clock cycles with an optimum clock of 56.8 MHz. A test bench was written to study the performance of the decoder, and the results are presented.     

Performance analysis and simulation of TH-PPM UWB system in image transmission

TH-PPM-UWB system of image transmission is presented in this paper. And then the performance analysis over an ideal AWGN （Additive White Gaussian Noise） channel is given. The studies indicate that the selection of parameters has a great influence on BER （Bit Error Rate） of the system, especially the number of pulses per information bit. The simulation results of image transmission demonstrate that a larger number of pulses per information bit will lead to better BER performance.     

Turbo码中快速交织器的设计

分析了交织器在Ｔｕｒｂｏ码中的重要作用，以及目前交织器存在的缺陷，介绍了一种快速交织器的设计方法。该交织器易于实现，具有交织时延低的突出优点。计算机仿真结果表明，该快速交织器可以获得优异的性能。     

SDH中泊松分布下误块率与误码率的关系分析

本文较详细地介绍了ＳＤＨ中的ＢＩＰ误码校验方式，推导了泊松分布下，ＢＩＰ误块率与误码率的一般关系式，给出了ＳＤＨ中几种典型的误块率与误码率的关系曲线，并做了计算机模拟验证     

迫零对Turbo码的性能影响

从距离谱的角度对迫零在Turbo码中的作用进行了理论分析。通过仿真，研究了迫零对Turbo码性能的影响。仿真结果表明，Turbo码编码器迫零处理有助于改善Turbo码的性能。     

相干OFDM系统中导引符号功率优化

在瑞利衰落信道下，本文研究了导引符号功率对相干OFDM系统性能的影响，计算了由于不精确信道估计引起的系统性能损失，优化分析了导引符号与数据符号功率比，并给出完整的最优功率分配数学表达式。理论分析和仿真结果给出了各种参数对最优功率比的影响，同时理论结果为系统设计提供了依据。     

参激随机共振及纠错码技术的应用

为了有效地降低数字信号传输过程中的比特误码率,提出了纠错编码与参数调节随机共振技术的结合.在经过噪声污染后,依据参数调节随机共振技术的性质,给出通过系统参数调节的二进制脉冲幅值调制（PAM）输入信号的渐近误码率公式,应用纠错码技术采用中间值估计的方法得到修正的比特误码率.数字仿真试验证实,理论计算结果与试验结果相吻合,纠错码技术与参激随机共振技术的结合应用于二进制基带信号传输,可以降低误码率,从而可以得到更好的效果,提高通信的可靠性和有效性.     

跳频通信系统的建模与仿真

在Matlab/Simulink仿真的平台上,利用跳频通信基本原理,在给定仿真条件下,建立了跳频通信系统模型,对系统进行了仿真,得到了宽带噪声干扰下的误码率信噪比曲线。通过跳频仿真图形前后对比,得出跳频通信系统的抗干扰能力优于传统的定频通信,在现代通信中有更高可靠性的结论。     

高速突发模式光接收机性能分析

针对无源光网络(PON)中上行突发信号的特点,从误码率、信噪比和信道利用率3个方面对直流耦合突发模式光接收机和交流耦合突发模式光接收机的性能作了对比分析.并给出了改善突发光接收机信噪比和信道利用率的实现方案,对高速突发接收方案的设计有较好的指导意义.