QPSK仿真系统的设计与实现

本文简介了QPSK技术的研究背景,构建了QPSK调制解调系统,将仿真进行的时候对噪声进行高效分析,研究了相关误码率及仿真结果。     

OFDM系统16QAM和QPSK调制仿真分析

以研究OFDM系统中使用的最佳数字调制方式为目的,分析了OFDM系统的原理、信号处理流程,以及一般使用的数字调制方式,利用matlab对系统进行了仿真,对比了系统分别采用16QAM和QPSK进行调制时的误码率,根据仿真曲线分析了二者的性能,得出系统在设定参数下特定信噪比时使用QPSK调制比16QAM调制误码率更低。     

MC法与QA法在通信系统仿真中的应用比较

研究MC(蒙特卡罗)仿真法和QA(准解析)仿真法的基本思想.为了验证这两种方法在通信系统仿真中的适用性与一致性,根据仿真原理,提出了相应的应用分析,首先建立二进制通信系统模型,然后利用Simulink软件,在相同的运行条件下,通过设置不同的信噪比,对模型的误码率进行了仿真.仿真结果表明这两种方法都能获得同样精确的仿真结果,而准解析法由于其解析的特性,仅需仿真整个系统中的非线性部分,因而相比于蒙特卡罗法所需的仿真运行时间更短,效率更高.     

采样频率偏差对QPSK OFDM系统误码率的影响分析

研究了采样频率偏差在加性高斯白噪声信道、瑞利平坦衰落信道和瑞利频率选择衰落信道下对QPSK OFDM系统误码率的影响。通过分析发现,采样频率偏差引起的OFDM系统子载波间的邻道干扰（ICI）不仅与子载波间的间隔有关,而且还与子载波的位置有关,其不能等效为载波频率偏差引起的ICI。通过对OFDM系统子载波间的ICI进行分析,求得上述三种信道条件下接收信号的特征函数;在基带调制方式为QPSK调制时得到了OFDM系统误码率的理论解析解。计算机仿真结果验证了该误码率理论解的正确性。     

蒙特卡洛仿真在移动通信中的应用研究

蒙特卡洛法的实质是利用服从某种分布的随机数来模拟现实系统中可能出现的随机现象。该文首先给出了如何利用蒙特卡洛(Monte-Carlo，简称MC)法来近似地描述研究对象的概率分布的一般方法；然后利用这一工具重点地研究如何模拟移动通信中的高斯(正态)、Reyleigll、Rice和Nakagami-m等四种常见的随机分布。在此基础上，该文详细地介绍了如何利用蒙特卡洛法对AWGN信道上的QPSK通信系统的传输特性进行仿真，同时也给出了16PSK系统的仿真结果。由于MC法是一种随机计算机模拟试验，其仿真精度与仿真次数有关。论文以AWGN信道的QPSK通信系统为例，用MC法仿真QPSK比特误码率BER随仿真次数变化曲线，并与理论值曲线做比较。仿真结果表明：在通信系统中，若仿真次数(或系统发送符号序列数)大于5000，MC仿真精度能基本满足工程上的要求。该文提供的方法对那些缺乏通信仿真软件的通信工作人员有一定的参考作用。     

基于蒙特卡罗仿真的LDPC解码器功耗分析方法

精确评估LDPC解码器在不同信噪比下的功耗需要在门级仿真大量的随机输入向量,以致耗费大量时间。通过对解码算法进行定点化的蒙特卡罗仿真可以方便地得到不同信噪比下的误码率和平均迭代次数。该文结合门级仿真与蒙特卡罗仿真,方便快速地得到LDPC解码器在不同信噪比下较为精确的功耗。通过对IEEE802．16e中一个LDPC码的实验,证明了该方法的可行性和有效性。     

QPSK信号IQ不平衡的角度统计盲补偿方法

针对直接变频接收机四相相移键控( QPSK) 信号的 IQ 不平衡问题,提出了一种角度统计的盲补偿方法。首先利用仿射坐标变换理论建立了实际的 IQ 信号与理想 IQ 信号的坐标旋转以及伸缩关系,然后通过坐标旋转的角度统计方法进行 IQ 不平衡系数的估计,从而实现 QPSK 信号的 IQ 不平衡补偿。仿真实验表明,相比其他的 IQ 不平衡盲补偿算法,该方法在降低误码率( BER) 的同时,减少了计算复杂度。     

基于傅里叶系数映射的OFDM系统性能分析

针对正交频分复用(OFDM)系统存在较高峰均比的问题,通过分析OFDM调制系统与周期信号傅里叶级数展开的关系,提出一种基于傅里叶系数映射的OFDM技术方案。该方案将待传输的数据调制为周期性信号,取该信号的部分傅里叶系数进行OFDM调制,替代传统的QPSK或MQAM映射方式。仿真结果表明,该技术方案在和QPSK映射相同频带利用率的情况下,其峰均比可下降3 dB,误码率与QPSK映射基本相当。     

蒙特卡罗法在调制解调中的应用

在加性高斯噪声干扰条件下的2FSK和16QAM调制解调方法基础上,根据蒙特卡罗仿真方法基本思想,建立在加性噪声干扰下的相关检测系统蒙特卡罗仿真模型。模型通过Matlab软件方法实现,最终仿真结果与对应系统的理论误码率基本符合。     

QPSK解调器性能参数测试仿真研究

本文首先对QPSK调制方式下,频率偏移和相位偏移对调制信号的影响进行了理论推导,利用matlab建立simulink仿真模型,讨论了符号采样数m,频率偏移△f和相位偏移△Φ对解调器误码率、入锁门限、捕捉带宽和同步带宽等测试/性能参数的影响,对QPSK方式解调器的设计、测试和维修等各方面都具有一定的借鉴作用.     

Further performance analysis of the generalized MC DS-CDMA system in Nakagami-m fading channels

The generalized multicarrier direct sequence code-division multiple-access (MC DS-CDMA) is a well known model that can be extended to different MC DS-CDMA schemes by simply varying a single parameter called as normalized subcarrier spacing. In this paper, the effect of the rate of average power decay on the bit error rate (BER) performance of the generalized MC DS-CDMA system is presented. Two specific schemes known as multitone DS-CDMA and orthogonal MC DS-CDMA are considered for the BER performance analysis. Simulation results show that the rate of average power decay has an important effect on the BER performance comparisons between the multitone DS-CDMA system and the orthogonal MC DS-CDMA system.     

一种接近于Shannon限的级联BCM码

给出一种新的级联分组调制（ＢＣＭ）码,其中内码选用带宽有效的ＢＣＭ码,外码采用ＲＳ码,在高斯信道中的仿真结果表明,这种码字在误码率为１０＾－６时较近乎相同带宽利用率下的未编码ＱＰＳＫ系统有５．３ｄＢ的编码增益,距离Ｓｈａｎｎｏｎ限只有０．５ｄＢ;在Ｒａｙｌｅｉｇｈ衰落信道中,误码率为１０＾－５时较未编码ＱＰＳＫ系统的编码增益可达到２０ｄＢ,距离无信道状态信息时的信道截止速率Ｒ０限为４．２ｄＢ,且译     

Throughput improvement of STS-based MC DS-CDMA system with adaptive modulation

The throughput enhancement of space-time spreading (STS)-based multicarrier direct sequence code division multiple access (MC DS-CDMA) system is investigated in this paper. Adaptive modulation is performed to improve the data throughput of the system in Rayleigh fading channel. In this contribution, an analytical approach is proposed to compute a new expression for the bit error rate (BER) performance of the STS-based MC DS-CDMA system for QAM data. The other contribution of the paper is deriving a new analytical expression for the throughput enhancement and the BER performance of the adaptive modulated STS-based MC DS-CDMA system over Rayleigh fading channel. The novel expressions presented in this paper bring out the facility of evaluation of the proposed system with no need for more calculations and simulations.     

Performance evaluation for PCC-OFDM systems impaired by carrier frequency offset over AWGN channels

Orthogonal frequency division multiplexing （OFDM） is sensitive to carrier frequency offset （CFO）, which destroys the orthogonality and causes inter-carrier interference （ICI）. ICI self-cancellation schemes based on polynomial cancellation coding （PCC-OFDM） can evidently reduce the sensitivity to CFO. In this paper, we analyze the performance of PCC-OFDM systems impaired by CFO over additive white gaussian noise （AWGN） channels. Two criteria are used to evaluate the effect of CFO on performance degradations. Firstly, the closed-form expressions of the average carrier-to-interference power ratio （CIR） and the statistical average ICI power, both of which reflect the desired power loss, are presented. Simulation and analytical results show that the theoretical expressions depend crucially on the normalized frequency offset and are hardly relevant to the number of subcarriers. Secondly, by exploiting the properties of the Beaulieu series, the effect of CFO on symbol error rate （SER） and bit error rate （BER） performance for PCC-OFDM systems are exactly expressed as the sum of an infinite series in terms of the charac- teristic function （CHF） of ICI. We consider the systems modulated with binary phase shift keying （BPSK）, quadrature PSK （QPSK）, 8-ary PSK （8-PSK）, and 16-ary quadrature amplitude modulation （16-QAM）, and all above modulation schemes are mapped with Gray codes for the evaluations of BER.     

基于多带正交频分复用的超宽带信号压缩传感

针对超宽带(UWB)信号在采样率过高时难以采样的问题,提出了改进的并行分段式压缩传感（MPSCS）方法,并且在多带正交频分复用超宽带通信系统中,利用MPSCS中基于正交匹配追踪（OMP）的重构算法进行了压缩采样与信号重构。在CM1信道下,通过仿真分析比较了MPSCS方法和并行分段式压缩传感（PSCS）方法、奈奎斯特方法的误码率、采样率性能。仿真结果显示,MPSCS在误码率、采样率方面有很大优势,而且在采样率仅为奈奎斯特速率6.06%的情况下,MPSCS能精确重构超宽带信号。     

An adaptive symbol-spaced equalizer to compensate analog imperfections

This paper presents an adaptive symbol-spaced equalizer solution to compensate for analog imperfections in a single carrier communication systems operating at very high symbol rates up to 500 Msym/s. Pass-band variations in the analog domain are typical at these high data rates, where the required bandwidth is approximately 1 GHz. Non-ideal analog filter responses and phase distortion produce Inter Symbol Interference (ISI) which increases modem implementation loss. This paper presents modeling of the modem?s analog imperfections, an overview of the equalizer algorithm and FPGA architecture, plus analysis and simulation of the expected performance gain. Pre and post equalization results from the real time tests, including BER performance with different modulation schemes such as BPSK, QPSK and 8PSK are also shown.     

Performance analysis of peak cancellation in OFDM systems

Peak cancellation is a class of peak-to-average power ratio (PAPR) reduction techniques for orthogo-nal frequency division multiplexing (OFDM).It can control the PAPR and out-of-band radiation simultaneously at the cost of additional interference.In this paper,the interference of peak cancellation is modeled and an-alyzed so as to evaluate the degradation of system performance.Furthermore,through theoretical analysis,a closed form of the BER performance is derived for OFDM with popular modulation schemes such as QPSK and 16QAM.Finally,the analytical results are verified by simulations.