Optimization of Mapping Rule of Bit-Interleaved Turbo Coded Modulation with 16QAM

Optimization of mapping rule of bit-interleaved Turbo coded modulation with 16 quadrature amplitude modulation (QAM) is investigated based on different impacts of various encoded bits sequence on Turbo decoding performance. Furthermore, bit-interleaved in-phase and quadrature phase (I-Q) Turbo coded modulation scheme are designed similarly with I-Q trellis coded modulation (TCM). Through performance evaluation and analysis, it can be seen that the novel mapping rule outperforms traditional one and the I-Q Turbo coded modulation can not achieve good performance as expected. Therefore, there is not obvious advantage in using I-Q method in bit-interleaved Turbo coded modulation.     

基于第三代移动通信系统的自适应多速率链路适配方案

针对第三代移动通信系统的特点,提出了一种新的自适应多速率链路适配方案.该方案综合考虑了自适应多速率编码器和功率控制对业务质量的影响.综合比较接收端的信号干扰比与切换门限值和发射功率与发射信号门限值,无线资源管理器能够根据跟踪具体链路的信道变化情况,选择合适的编码模式,提供可靠的业务质量并提高系统容量.基于WCDMA系统FDD模式上行链路仿真平台,构造了AMR链路适配平台并进行了实现方案及算法性能的仿真.仿真结果表明,该方案能够跟踪信道快速变化,实现编码模式的平滑切换,AMR合成语音质量优于单一编码模式,为AMR编码技术提供了适用于第三代移动通信系统的链路适配方案.     

JTIDS网络建模与仿真平台设计

基于对JTIDS网络的研究,建立了符合OSI分层标准的端机模型和毁伤加载节点模型,仿真平台实现了基本网络功能,并重点解决了功能端机退出带来的网络拓朴结构变化问题和链路仿真和网络仿真跨平台间的接口问题.针对不同设置,仿真实验将获得各种情况下的网络和端机性能指标,有效地指导了网络设计和优化.     

基于Turbo-TCM与时空分组码的级联系统的次优译码算法

针对瑞利信道中存在的严重的多径衰落,本文实现了Turbo-TCM方案与时空分组码的级联系统,以期利用空间分集改善系统的误码率性能。针对级联系统的译码,本文给出了一种具有低译码时延的次优译码算法,该算法的特点是各模块独立译码,先算比特对数似然比再进行二进制Turbo码译码。最后通过计算机仿真给出了使用该次优译码算法的Turbo－TCM方案与时空分组码的级联系统的译码性能。仿真结果说明,当发射天线数目一定时,随着接收天线数目的增加,译码性能的增益随之增加而帧长对译码性能的影响则随之减小。     

Performance Analysis of Wireless Mobile Radio Hybrid（DS／FH） Spread Spectrum Network

By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-collision probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultaneous transmission number threshold and is discussed in synchronous and asynchronous circumstances respectively. And then, the network throughput based on the packet correct reception probability is analyzed. Two models which have finite and infinite population respectively is discussed. At last, the numerical results are given.     

深化教育改革,提高教育质量

北京理工大学电子工程系始建于1952年,是我国首批建立的从事雷达遥控遥测专业教学与科研工作的单位之一.1987年设立了无线电电子学研究所,该系有一支较强的师资队伍,全系有14名教授,30多年来除为国家培养了一批高级工程技术人才外,还为国家输送了5500余名本科生,207名硕士研究生,20余名博士研究生.现在全系设有无线电技术、通信工程、电磁场与微波技术及微电子电路与系统4个专业,1980年被批准建立硕士点,设有通信与电子系统、信号与信息处理、电磁场与微波技术、微电子技术及电路与系统5个硕士点.1984年被批准建立博士点,目前全系有通信与电子系统、信号与信息处理及电磁场与微波技术三个博士点.1987年通信与电子系统被评为国家级重点学科,电磁场与微波技术评为部级重点学科.     

Channel Coding Techniques for VHF-Mobile Radio System and Its DSP Implementation

Forastronglyvaryingtransmissionenviron ment,anadaptivemulti rate(AMR)speechcodec hasbeenadoptedforsourcecodingonVHF mobile radiosystem,justasin3GPPsystem.TheAMRen codedbitsofthespeechcoderarecomposedofbits withvaryingimportanceforthereconstructionof originalspeech.Duetothedifferenceofeachbitson sourcesignificantinformation,unequalerrorprotec tion(UEP)adoptedinthechannelprotectionof speechcoderhasbeenextensivelystudied[1,2].Theapplicationofrate compatiblepunctured convolutional(RCPC)for…     

串行级联码的改进译码设计和SOVA算法

为了提高采用短交织器的串行级联卷积码在低级迭代译码时的性能 ,将对数最大似然算法的译码结构引入传统的SOVA中以增强其在短交织时延时的性能 .由于对数最大似然算法和SOVA算法的结合避免了对最大路径中每步度量的更新 ,该算法也对低时延要求有所贡献 .对几种串行级联卷积码仿真的结果表明改进的译码器能在短帧交织时获得满意的性能 .改进的串行级联卷积码的译码算法和设计适用于高比特率低时延的通信系统 .     

卫星通信Modem中可编程RS编译码模块的设计与实现

研究并实现了一种卫星通信modem中可编程RS编译码模块.本模块以FPGA为实现核心,以ASIC为辅助,整个模块包括RS编译码单元、交织解交织单元、扰码解扰单元和帧同步单元.成功实现了可编程RS编译码模块,它可以通过在线编程实现IESS 308/309/310标准中所规定的多种业务类型和数据速率.FPGA与ASIC相结合使整个电路具有体积小、灵活性高、稳定性强的特点,本模块具有软件无线电概念,可以很容易地集成到整个的卫星通信modem中.     

Improved Spectral Representation for Birdcall Based on Fractional Fourier Transform

A novel spectral representation based on fractional Fourier transform (FrFT) is proposed and applied to birdcall analysis. The FrFT-based spectrogram of a signal is derived and compared with its FT-based counterpart,and the spectrum gathering method is used to show the energy distribution related to the pitch frequency. The fixed transform order and adaptive orders for FrFT are tested. The fixed order can be obtained empirically or calculated according to the known chirp rate. The adaptive optimal orders are determined by using ambiguity function. Experimental results with birdcalls show that the FrFT-based spectrogram with an optimal transform order has higher resolution than its STFT-based counterpart,and the better performance can be achieved if adaptive orders are used.