相干接收随机多码CDMA在多径衰落信道中的容量性能研究

本文研究采用ＢＰＳＫ调制、相干ＰＡＫＥ接收的随机访问多码ＣＤＭＡ）ＲＡＭＣ＿ＣＤＭＡ）在频率选择性Ｎａｋａｇａｍｉ多径衰落、噪声信道（ＭＦＮＣ）中的容量性能,建立系统模型后,推导出了多用户条件下接收机输出的条件概率分布及判决平均比特误码率,并以Ｒａｙｌｉｇｈ多径衰落、噪声信道为例,计算了系统容量的数值解,分析表明：ＲＡＭＣ－ＣＤＭＡ解决了普通ＤＳ－ＣＤＭＡ系统存在的用户可传信息速率受限的问题,能在     

时间色散信道中格形编码的正交频分复用(TC-OFDM)技术

本文提出了一种格形编码的正交频分复用（ＴＣ－ＯＦＤＭ）方案，研究把正交频分复用（ＯＦＤＭ）和格形编码（ＴＣＭ）有机地结合，来克服时间色散信道中的频率选择性和多径衰落。文中对码率２／３格形编码的８ＤＰＳＫ－ＯＦＤＭ在时间色散信道中的误码率性能进行了分析和模拟，并讨论了不同正交载波数情况下格形编码的设计。结果表明，在比特误码率ＢＥＲ为１０－３时采用ＴＣ－ＯＦＤＭ方案与未编码系统相比可以提供６ｄＢ的编码增益。     

广义多径信道MDPSK相位比较解调性能

本文提出了一种适合于广义多径信道多进制差分相移键控信号相位比较解调的性能分析方法，推导出符合平均错误率积分表达式。该表达式考虑了信号幅度衰落，时间选择性衰落和高斯白噪声对体制性能的影响。并针对几种形式的衰落功率谱分别对二进制，四进制和八进制的符号平均错误率进行了数值计算，讨论了衰落功率谱的形式对ＭＤＰＳＫ信号性能的影响，并给出了ＭＤＰＳＫ信号的“不可克服符号错误率”与衰落功率谱归一化带宽的关系曲线     

混合DS－SFH扩频多址通信系统采用RS码的性能界限的分析

本文推导了混合直接序列和慢跳频扩频多址通信系统，在Ｒｉｃｉａｎ和Ｒａｙｌｅｉｇｈ多径衰落信道中，采用ＲＳ编码和非相干ＤＰＳＫ、ＦＳＫ调制的系统性能界限，提出了利用探测多径干扰和多址干扰是否存在的信道信息的ＲＳ译码新算法。     

混合DS—SFH扩频多址通信系统采用RS码的性能界限的分析

本文推导了混合直接序列和慢跳频扩频多址通信系统，在Ｒｉｃｉａｎ和Ｒａｙｌｅｉｇｈ多径衰落信中，采用ＲＳ编码和非相干ＤＰＳＫ、ＦＳＫ调制的系统性能界限，提出了利用探测多径干扰和多址干扰是否存在的信道信息的ＲＳ译码新算法。     

网格编码MQAM直扩多址系统的性能分析

本文将非恒包络高效网格编码调制ＴＣ－ＭＱＡＭ应用于瑞利慢衰落信道下的直接序列扩频多址系统中。针对衰落信道和ＴＣ－ＭＱＡＭ的特点，提出了一种分析ＴＣ－ＭＱＡＭ用于衰落信道下ＤＳ／ＳＳＭＡ系统性能的方法，数值模拟表明在系统用户数、用户信源比特速率以及码相同的条件下，本文所构造的非恒包络１／４ＴＣ－１６ＱＡＭ性能优于同状态数３／４ＴＣ－１６ＱＡＭ和恒包络２／３ＴＣ－８ＰＳＫ。这说明通过增大最小分支数等适     

高效频谱调制方式在蜂窝移动通信系统中的性能分析

本文研究高效频谱调制方式ＭＰＳＫ及ＭＱＡＭ在蜂窝移动通信中的应用及其性能。在综合考虑共道干扰，Ｒａｙｌｅｉｇｈ衰落以及高斯噪声等影响因素的基础上，结合分集接收技术，我们给出了ＭＰＳＫ及ＭＱＡＭ应用于蜂窝移动通信时误码率计算的通用近似公式。蒙特－卡洛仿真表明文中给出的误码率近似公式能很好地吻合实际系统的仿真结果。     

数据在陆地移动卫星通信信道中传输性能的分析

本文阐述陆地移动卫星通信系统（ＬＭＳＳ）及其信道传输的性能和特点。文中引进信道衰落模型，就ＢＰＳＫ调制的数据包（Ｐａｃｋｅｔ）在传输中的误码率及其性能作了研究。对移动终端的速度、数据传输速率、地面环境及载波频率对信道传输效率的影响作了探讨。     

采用连续相位FSK调制方式π／2—TFSK的移动通信信道中的数字传输特性的改善

在移动通信信道中，建立数字无线电系统时，为了有效利用频率，必需要同时考虑频谱特性和差错率，选择适当的调制方式．尤其是高速传输时（起因于信道多径波干扰）传输特性恶化少，且频谱特性较好的调制方式的开发很有意义．本论文先求出我们最早提出的π／２—ＴＦＳＫ的频谱，阐明其特性．再求出检波器输出的眼孔，讨论１比特延迟检波、２比特延迟检波特性的分析．用平方余弦（ＲＣ）滤波器进行基带的带限时，π／２—ＴＦＳＫ（ＲＣ－π／２－ＴＦＳＫ）的眼孔的开度比ＭＳＫ（ＲＣ—ＭＳＫ）的大，表明本方式很适合移动通信信道．最后求出使用高斯形收信ＢＰＦ时的理想收信带宽．     

滑动窗快速横向滤波的自适应判决反馈均衡器算法

本文提出了一种基于滑动窗广义多路快速横向滤波（ＳＷＦＴＦ）的自适应判决反馈均衡器（ＤＦＦ）算法，它具有快速跟踪性能，故可用于快速时变多径衰落的信道。文中推导了ＳＷＦＴＦ－ＤＦＥ算法。在数字移动通信信道模型上，利用计算机模拟，在均方误差和误码率特性方面与其它均衡器算法进行了比较。     

相位调制的多用户OFDM-FH通信系统性能分析

 本文研究一种高效的通信方式,即相位调制的OFDM-FH通信系统。为了提高衰落信道下系统误码率性能,接收端采用最大比合并的分集接收技术。利用特征函数方法,推导该系统在加性高斯白噪声信道和瑞利衰落信道时系统误码率性能。给出误比特率与跳频频点数 ,OFDM子载波数N和用户数 等参数之间的关系。理论分析和仿真实验结果表明,在相同参数条件下,基于相位键控调制的OFDM-FH多址接入系统与其它OFDM-FH通信系统比较,具有系统频带宽度占用少、误比特率低等优势。     

Error performance of interleaved trellis-coded PSK modulations incorrelated Rayleigh fading channels

The authors derive an exact and easily computed expression for the pairwise error event probability of interleaved coded PSK modulations transmitted over channels with correlated Rayleigh flat fading and additive white Gaussian noise. Both coherent and differential detection are considered. In the case of coded DPSK, it is found that full interleaving does not necessarily provide the best error performance, especially when the fading is relatively fast and when the autocorrelation function of the channel fading process exhibits an oscillating behavior. For coherent detection or for differential detection in channels with relatively slow fading, increasing the interleaving depth always improves the error performance. In these cases, an interleaving depth equivalent to one-fifth to one-quarter the duration of a fade cycle is almost as good as full interleaving     

Sample size required in error-rate measurement on fading channels

This paper presents analytical and numerical results on the sample size required to achieve a specified root mean square (RMS) error in estimating the error rate for flat fading channels having complex Gaussian statistics. The analysis shows that for the large sample sizes normally used in estimating error rates, k, the required sample size normalized to the required sample size for independent symbol fading, can be expressed in the form k=1+dβ where d is the symbol rate normalized to the Doppler spread of the channel. For a given modem, β is a function of the error probability and the order of diversity. It is shown that if the Doppler spread measure used is proportional to the RMS Doppler spread, P will be relatively insensitive to the shape of the Doppler power spectrum. Numerical results are presented for Lth order diversity reception of binary phase shift keying (PSK), differential PSK, and frequency shift keying (FSK) signals and for five different Doppler power spectra. Ideal maximal ratio combining is assumed for the PSK modem, and square law combining is assumed for the DPSK and FSK modems     

Concatenated coding schemes and interleaving techniques over Rayleigh fading ionospheric channels

In this paper the performance of a concatenated coding scheme is evaluated over a slow Rayleigh fading HF ionospheric link with additive white Gaussian noise (AWGN). Well‐known Ungerboeck TCM techniques onto an 8‐PSK signal set are used as inner codes and Reed–Solomon block codes as outer codes. The coded/modulated signal is further differentially encoded before transmission to combat random phase changes. Block interleaving techniques are necessary to randomise long bursts of errors caused by the fading channel. The performance of the proposed concatenated coding system is investigated for various Doppler spreads. Significant coding gains are achieved over uncoded, diversity or other conventionally coded systems with a small bandwidth expansion. Finally the interesting effects of interleaving on the behaviour of the proposed systems are analysed. Copyright © 2001 John Wiley & Sons, Ltd.     

Error probability of M-ary FSK with differential phasedetection in satellite mobile channel

Formulas are derived for the error probability of M-ary frequency shift keying (FSK) with differential phase detection in a satellite mobile channel. The received signal in this channel is composed of a specular signal, a diffuse signal, and white Gaussian noise; hence, the composite signal is fading and has a Rician envelope. The error probability is shown to depend on the following system parameters: (1) the signal-to-noise ratio; (2) the ratio of powers in the specular and diffuse signal components; (3) the normalized frequency deviation; (4) the normalized Doppler frequency; (5) the maximum normalized Doppler frequency; (6) the correlation function of the diffuse component, which depends on the normalized Doppler frequency and the type of the antenna; (7) the number of symbols; and (8) the normalized time delay between the specular and diffuse component (t _d/T) where 1/T is the symbol rate. Except for T_d/T, all normalized parameters are the ratios of the parameter value and symbol rate. The Doppler frequency depends on the velocity of the vehicle and the carrier frequency. The error probability is computed as a function of the various parameters. The bit error probability is plotted as a function of signal-to-noise ratio per bit and other system parameters     

Prediction/cancellation techniques for fading broadcastingchannels. I. PSK signals

An approach for reducing the effects of multiplicative noise, such as fading, on the performance of mobile broadcasting transmission systems is introduced. The proposed method is based on a noise prediction/cancellation technique and is applied to phase-shift keyed (PSK) signals. By exploiting the statistical characteristics of the multipath fading signal and its strong correlation properties, a novel sequential receiver structure is derived that uses a detection algorithm which identifies the most probable transmitted sequence in the maximum-likelihood detection sense. The algorithm has been obtained for both Rayleigh and Rician fading channels. The proposed detection technique has been evaluated for various QPSK schemes operated in channels corrupted by a combination of additive white Gaussian noise (AWGN) and fading. The computer simulation results obtained show that by using a relatively simple receiver with a prediction algorithm of second order, considerable error floor reductions are achieved by the proposed receivers. As a direct result of these error floor reductions substantial bit error rate (BER) improvements of more than three orders of magnitude over conventionally detected schemes are obtained     

高频电离层通信中多径时延与多普勒频移分布

本文在瑞利衰落模型下，研究了高频电离层信道中多径时延与多普勒频移的随机特性，导出了它们的概率分布，并讨论了瞬时多径时延和瞬时多普勒频移与平均归一化功率之间的关系。     

Some new twists to problems involving the Gaussian probabilityintegral

Using an alternate form of the Gaussian probability integral discovered a number of years ago, it is shown that the solution to a number of previously considered communication problems can be simplified and, in some cases, made more accurate (i.e. exact rather than bounded). These problems include the evaluation of: (1) the bit-error probability of uncoded phase shift keying (PSK) with Costas loop tracking; (2) word-error probability of antipodal modulation in the presence of fading; (3) bit-error probability of coded M-ary PSK (MPSK) over the memoryless fading channel with given channel-state information; (4) conditional symbol-error probability of MPSK in the presence of carrier synchronization error; and (5) the average error probability for the binary additive white Gaussian noise (AWGN) intersymbol interference channel. Also obtained is a generalization of this new alternate form to the case of a two-dimensional Gaussian probability integral with arbitrary correlation which can be used to evaluate the symbol-error probability of MPSK with I-Q unbalance     

Double differential MPSK on the fast Rician fading channel

An analysis of adjacent and nonadjacent double differential M -ary PSK (M-ary D²PSK) on the fast Rician fading channel is presented. The probability density function (PDF) of the first-order phase error (FOPE) and the probability density functions of the second-order phase error (SOPE) for both adjacent and nonadjacent D²PSK on a fading channel have been derived. Asymptotic approximations for these PDFs are proposed in the case of channels with weak fading (including the additive white Gaussian noise (AWGN) channel) and high signal-to-noise ratio. For nonadjacent D²PSK with independent FOPEs a simplified PDF of SOPE has been obtained. The derived PDFs allow calculation of error performance of D²PSK, as well as of DPSK, on the Rician channel including the AWGN channel and the Rayleigh channel and verification of some results reported in the literature earlier. It is shown that nonadjacent D²PSK can be optimized by choosing a proper separation between the first-order phase differences     

Convolutionally interleaved PSK and DPSK trellis codes forshadowed, fast fading mobile satellite communication channels

Using a model from the literature, the performance of convolutionally interleaved phase-shift-keying (PSK) and differential phase-shift-keying (DPSK) trellis codes for digital speech transmission over shadowed mobile satellite communication channels is determined by computer simulation. First the characteristics of fading channels are examined and analyzed in terms of the probability distributions of amplitude, phase, and burst errors. A statistical method, using a histogram approach, is utilized along with the simulations of fading channels to generate these probability distributions. A test for channel burst error behavior is presented. A periodic convolutional interleaver/deinterleaver to be used with trellis coding to combat slow fading in digital, shadowed mobile satellite channels is designed. This interleaver ha less than half the time delay for the same bit error performance than a block interleaver. The results show that the periodic convolutional interleaver provides considerable improvement in the error and time delay performance of mobile satellite communication channels for up to average shadowing conditions as compared to other techniques