A Comparison of Frequency-Domain Block MIMO Transmission Systems

Block transmission techniques, with appropriate cyclic prefix and frequency-domain processing schemes, have been shown to be excellent candidates for digital transmission over severely time-dispersive channels, allowing good performance with implementation complexity that is much lower than traditional time-domain processing schemes. Orthogonal frequency-division multiplexing (OFDM) modulation is the most popular block transmission technique. Single-carrier (SC) modulation using frequency-domain equalization (FDE) is an attractive alternative approach based on this principle. In this paper, we propose two new receiver structures for multiple-input-multiple-output (MIMO) channels employing SC (MIMO-SC) modulation and FDE schemes. These receivers have a hybrid structure with frequency-domain feedforward and time-domain feedback filters for intersymbol interference (ISI) and interference cancellation. The proposed schemes are compared with different MIMO systems employing OFDM modulation (MIMO-OFDM) receivers in terms of performance [bit error rate (BER) and throughput] and complexity. Our performance results show the superiority of MIMO-SC approaches relative to MIMO-OFDM in terms of the BER performance for the simulated scenarios. Also, the simulation results show that the proposed hybrid MIMO-SC receivers yield a higher throughput than a MIMO-OFDM system.     

超宽带波形和调制技术研究

研究了几种不同的脉冲成形和调制技术,并对其性能进行了分析。仿真结果表明,在AWGN信道和瑞利衰落信道下,不同的脉冲形状对脉冲位置调制（PPM）的性能影响较大,而对二进制相移键控调制（BPSK）和开关键控调制（OOK）影响较小,且当采用RZ-Manchester脉冲时,BPSK调制技术下的误比特率（BER）性能在两种信道下均达到最好。     

Performance Evaluation of the Physical Layer of the DSRC Operating in 5.8 GHz Frequency Band

In this paper, the theoretical as well as experimental results of BER characteristics of three different modulation schemes, ASK, FSK and BPSK, in a multi‐path Rician channel are addressed. These BER characteristics are analyzed as a function of E_b / N_o and the power ratio of the line of sight (LOS) component to the Rayleigh scattered component. The theoretical as well as computer simulation results shows the ASK is the most suitable modulation scheme for the dedicated short range communication (DSRC) in terms of implemental cost and system complexity. The decision feedback equalizer is proved to be very effective in canceling the multi‐path interference in the DSRC channel environment. The simulation result of the equalized ASK, reveals the performance enhancement achievable with decision feedback (DFE) equalizer for the first generation DSRC system. The multi‐ray DSRC channel model is also provided to predict the received carrier power and fluctuation, which are quite dependent on the surroundings of a cell.     

Performance Analysis of Rate-Adaptive Modulation with Imperfect Estimation in Space?CTime Coded MIMO System

Based on the imperfect estimation information, the performance analysis of multi-input multi-out (MIMO) systems with rate-adaptive modulation and space?Ctime coding over flat Rayleigh fading channels is presented in this paper. The fading gain value is partitioned into a number of regions by which the modulation is adapted according to the region the fading gain falls in. Under a target bit error rate (BER) and constant power constraint, the fading gain region boundaries are given. By utilizing the minimum mean squared error estimation, the correlation between the channel gains and their estimates, which contributes to imperfect channel information, is evaluated. With this correlation, the probability density function of fading gain is obtained. Based on these results, the closed-form expressions for the SE and average BER are derived in detail, respectively. The theoretical expressions will be more accurate than the existing schemes, and they include perfect estimation as a special case. Numerical results show that the SE and BER of the system with imperfect estimation are worse than those with perfect estimation due to the estimation error. Moreover, the simulation results for SE and BER are in good agreement with the theoretical analysis.     

一种改进的混沌键控调制解调技术

随着混沌理论和通信技术的发展,各种通信调制方案的性能也逐渐被人们所研究并掌握。文中通过对现有混沌调制解调方式的分析和研究,将调幅、调频、正交相结合提出了一种改进的混沌调制方案——调幅调频正交混沌键控技术（AF-QCSK）。并对其误码率性能和传输速率进行仿真,结果表明这种改进的调试方案明显提高了系统的通信效率。     

Accurate evaluation of multiple-access performance in TH-PPM and TH-BPSK UWB systems

A characteristic function method is proposed for precisely calculating the bit-error probability of time-hopping (TH) ultra-wideband (UWB) systems with multiple-access interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation. The Gaussian approximation is shown to be inaccurate for predicting bit-error rates (BERs) for medium and large signal-to-noise ratio (SNR) values. The performances of TH pulse position modulation (PPM) and binary phase-shift keying (BPSK) modulation schemes are accurately compared in terms of the BER. It is shown that the BPSK system outperforms the binary PPM system for all values of SNR. The sensitivity of the performance of the modulation schemes to the system parameters is also addressed through numerical examples.     

基于QC-LDPC的水下激光通信编码技术

针对水下蓝绿激光远距离可靠通信的需求,文中提出了PPM与QC-LDPC相结合的调制编码通信方法.通过对不同码长、码率与PPM调制阶数的组合方案进行仿真,找出在不同SNR条件下的最优QC-LDPC编码与PPM调制的组合方案.文中介绍了经典PPM信号的原理与QC-LDPC码的基本结构,并通过MATLAB软件模拟实现PPM信...     

Modulation methods for PCNs

The interference levels that may be expected for a range of conventional cellular and microcellular clusters used in personal communication networks (PCNs) and personal communication systems (PCSs) are discussed. Simulation results show that for conventional size cells, 32- and 64-level quadrature amplitude modulation (QAM) schemes are preferred for bit error rates (BER) above 1×10^-2, while 4PSK or variable-rate QAM schemes are better for lower BER. For microcells with communications at both 900 MHz and 1.8 GHz, four- or six-cell clusters are advocated, depending on the SNR expected. Based on the expected signal-to-noise ratio (SNR) and interference levels, it is argued that variable-rate QAM schemes are superior to the other modulation schemes considered. For low BERs 4PSK may often provide the best performance, whereas for high BERs, particularly when the SNR is high, 32- and 64-level star QAM are the most suitable     

64DAPSK-OFDM与64QAM-OFDM系统性能比较

针对OFDM系统中的MQAM和MDAPSK两种子载波高阶调制技术,介绍了64QAM和64DAPSK信号的比特软输出解调方法,比较了64DAPSK-OFDM和64QAM-OFDM系统的误码性能。仿真结果表明,在频率选择性和时间选择性衰落信道下,若信道相邻子载波或相邻OFDM符号的相关性能得到保证,采用64DAPSK调制可以用较少的信噪比损失换取OFDM系统复杂度的大大降低。     

Bandwidth‐efficient turbo coding over Rayleigh fading channels

Introduced in 1993, turbo codes can achieve high coding gains close to the Shannon limit. In order to design power and bandwidth‐efficient coding schemes, several approaches have been introduced to combine high coding rate turbo codes with multilevel modulations. The coding systems thus obtained have been shown to display near‐capacity performance over additive white Gaussian noise (AWGN) channels. For communications over fading channels requiring large coding gain and high bandwidth efficiency, it is also interesting to study bit error rate (BER) performance of turbo codes combined with high order rectangular QAM modulations. To this end, we investigate, in this paper, error performance of several bandwidth‐efficient schemes designed using the bit‐interleaved coded modulation approach that has proven potentially very attractive when powerful codes, such as turbo codes, are employed. The structure of these coding schemes, termed ‘bit‐interleaved turbo‐coded modulations’ (BITCMs), is presented in a detailed manner and their BER performance is investigated for spectral efficiencies ranging from 2 to 7 bit/s/Hz. Computer simulation results indicate that BITCMs can achieve near‐capacity performance over Rayleigh fading channels, for all spectral efficiencies considered throughout the paper. It is also shown that the combination of turbo coding and rectangular QAM modulation with Gray mapping constitutes inherently a very powerful association, since coding and modulation functions are both optimized for operation in the same signal‐to‐noise ratio region. This means that no BER improvement is obtainable by employing any other signal constellation in place of the rectangular ones. Finally, the actual influence of the interleaving and mapping functions on error performance of BITCM schemes is discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

An Introduction to Adaptive QAM Modulation Schemes for Known and Predicted Channels

A major disadvantage with fixed modulation (nonadaptive) on channels with varying signal-to-noise ratio (SNR) is that the bit-error-rate (BER) probability performance is changing with the channel quality. Most applications require a certain maximum BER and there is normally no reason for providing a smaller BER than required. An adaptive modulation scheme, on the contrary, can be designed to have a BER which is constant for all channel SNRs. The spectral efficiency of the fixed modulation is constant, while it, in general, will increase with increasing channel SNRs for the adaptive scheme. This in effect means that the average spectral efficiency of the adaptive scheme is improved, while at the same time the BER is better suited to the requirement of the application. Thus, the adaptive link becomes much more efficient for data transmission. The major disadvantage is that the transmitter needs to know the channel SNR such that the best suitable modulation is chosen and the receiver must be informed on the used modulation in order to decode the information. This leads to an increased overhead in the system as compared with a fixed modulation system. In this paper, we introduce adaptive modulation systems by presenting some of the simpler adaptive quadrature amplitude modulation schemes and their performance for both perfectly known and predicted channels.     

Degrees of freedom in adaptive modulation: a unified view

We examine adaptive modulation schemes for flat-fading channels where the data rate, transmit power, and instantaneous BER are varied to maximize spectral efficiency, subject to an average power and BER constraint. Both continuous-rate and discrete-rate adaptation are considered, as well as average and instantaneous BER constraints. We find the general form of power, BER and data rate adaptation that maximizes spectral efficiency for a large class of modulation techniques and fading distributions. The optimal adaptation of these parameters is to increase the power and data rate and decrease the BER as the channel quality improves. Surprisingly, little spectral efficiency is lost when the power or rate is constrained to be constant. Hence, the spectral efficiency of adaptive modulation is relatively insensitive to which degrees of freedom are adapted     

Examples of Continuous Phase Modulation Using Discriminator Detection

Continuous phase modulation (CPM) techniques for digital communication have been proposed to achieve narrow bandwidth and good bit error rate (BER) performance in coherent systems. These modulation schemes may also be used with noncoherent discriminator detection. However, in this case, the CPM schemes should be designed for noncoherent detection. Using a receiver proposed by Chung for GTFM and "modified GTFM" signals, we show that it is possible to slightly improve BER performance over that of previous GTFM noncoherent schemes. We also show that a form of GMSK can achieve discriminator detectability performance almost equal to that of classical binary FSK (modulation index = 0.7) but with a much narrower bandwidth.     

Differential spatial modulation scheme based on orthogonal space-time block coded

Focusing on the problem that differential spatial modulation (DSM) couldn’t obtain transmit diversity and has high decoding complexity,a new differential spatial modulation scheme based on the orthogonal space-time block code was proposed and the proposed scheme is called OSTBC-DSM.There were two matrices in this scheme:the spatial modulation matrix and the symbol matrix.The former was aimed to activate different transmit antennas by setting the position of nonzero elements,and the latter structured symbolic matrix by using orthogonal space-time block codes (OSTBC) as the basic code block.The proposed scheme could obtain full transmit diversity and higher spectral efficiency compared with the conventional DSM schemes.Moreover,the OSTBC-DSM supported linear maximum likelihood (ML) decoding.The simulation results show that under different spectral efficiencies,the proposed OSTBC-DSM scheme has better bit error rate (BER) performance than other schemes.     

采用MSK调制的物理层网络编码信号检测

针对双向中继信道,提出一种采用最小频移键控（MSK）调制的物理层网络编码（PNC）方案,即MSK-PNC。与采用BPSK、QPSK等线性调制技术的物理层网络编码方案相比,MSK-PNC具有更高的频谱效率和功率效率。本文对MSK-PNC方案中的物理层网络编码信号检测进行研究,提出了两种检测方法。第1种方法采用正交解调映射,第2种方法采用最大似然序列检测。分析和仿真结果表明,正交解调映射方案使得MSK-PNC误比特率性能等于QPSK-PNC,最大似然序列检测算法在实现复杂度上相对较高,但是其误比特率性能更优,并且同样适用于检测采用CPFSK调制方式的物理层网络编码信号。      

Performance analysis of M‐APSK generalised spatial modulation with constellation reassignment

Generalised spatial modulation (GSM) is a recently developed multiple‐input multiple‐output (MIMO) technique aimed at improving data rates over conventional spatial modulation (SM) systems. However, for identical antenna array size and configurations (AASC), the bit error rate (BER) of GSM systems in comparison with SM systems is degraded. Recently, a GSM system with constellation reassignment (GSM‐CR) was proposed in order to improve the BER of traditional GSM systems. However, this study focused on M‐ary quadrature amplitude modulation (M‐QAM) schemes. The focus of this paper is the application of a circular constellations scheme, in particular, amplitude phase shift keying (APSK) modulation, to GSM and GSM‐CR systems. An analytical bound for the average BER of the proposed M‐APSK GSM and M‐APSK GSM‐CR systems over fading channels is derived. The accuracy of this bound is verified using Monte Carlo simulation results. A 4 × 4 16‐APSK GSM‐CR system achieves a gain of 2.5 dB at BER of 10^?5 over the traditional 16‐APSK GSM system with similar AASC. Similarly, a 6 × 4 32‐APSK GSM‐CR system achieves a gain of 2 dB at BER of 10^?5 over equivalent 32‐APSK GSM system.     

Improved NSGA-II optimizing coding-link cost trade-offs for multicast routing in WDM networks

The present study proposed a high-data-rate underwater optical wireless communication (UOWC) system to propagate the laser blue–green waves through water. The presented study not only focuses on analysis of challenges in UOWC link including attenuation, absorption, scattering and turbulence model, but also investigates the performance of the proposed system using two different methods of balanced modulation schemes. Spectrum efficiency of the system can be improved by using appropriate modulation formats. Return-to-zero differential phase shift keying (RZ-DPSK) and non-return-to-zero differential phase shift keying (NRZ-DPSK) schemes are two modulation formats that we investigate them to improve the characteristics of the proposed UOWC system. The paper explains a real model and exhaustive analysis for advanced UOWC works by using channel model and modulation formats for presented underwater link. Performance of the proposed system under different modulation schemes and physical aspects of UOWC is studied with several parameters like max quality factor, min bit error rate (BER) and eye diagram. For clear ocean, the performance of the proposed system is good and min BER less than 10^?90 for two modulation formats. Generally, results at different condition show that the operation of NRZ-DPSK modulation has better performance than RZ-DPSK scheme.     

More accurate simulation of dynamic transparent optical wavelength division multiplex networks

Novel modulation schemes and higher bit rates as well as dynamically switched networks make it necessary to consider effects, which could be neglected in system simulations so far. In this paper, we present simulation methodologies needed for the accurate characterisation of the signal quality in such transparent optical networks.The combined effects of polarisation mode dispersion (PMD) and polarisation-dependent loss (PDL) are investigated, and a more accurate method for the BER estimation based on histograms is described. Furthermore, dynamical transient effects in the physical layer require extending the regarded time scale to the millisecond range. An efficient way how to simulate the effects on different time scales is presented.     

基于脉冲调制的GSM语音信道数据传输方法

针对全球移动通信系统 (GSM) 的安全机制不能实现端到端安全通信问题,提出了一种低复杂度基于脉冲调制的数据传输方案及优化方法。分别设计了基于脉冲位置调制及脉位结合极性调制的类语音信号,给出了基于跳时脉冲的帧同步方法。搭建了基于脉冲调制的GSM语音信道数据传输仿真平台,分析比较了不同调制阶数和不同自适应多速率编码 (AMR) 码率下系统的性能。为了提高系统可靠性,引入卷积码进一步降低了系统误码率。仿真结果表明,4阶脉冲调制最适用于语音信道,所提脉冲调制方法与传统低复杂度频移键控 (FSK) 调制方式误码率近似,但传输速率高,且提出的脉位结合极性调制进一步提高了传输速率,总提高比例达到36%。     

高斯白噪声信道中MQAM误码性能——移动通信中多电平正交振幅调制方案的优化考虑(一)

对白噪声信道中MPSK、矩形星座图MQAM与圆形星座图MQAM的传输误码性能作了详细的分析比较,给出相应的误码率计算公式与计算机数值分析结果,为MQAM调制方案的选择提供了理论分析依据。