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.     

一种用于BICM-ID系统的新颖8APSK映射方案

为了能够通过高阶调制信号增加信道容量,提高编码增益和频谱效率,对8阶振幅移相键控(APSK)星座映射方案进行优化.基于欧氏距离设计准则提出一种新颖(2,6)-scheme 8APSK映射方案,并应用于联合准循环构造法构造的低密度奇偶校验(LDPC)(4599,4307)码的比特交织编码调制迭代译码(BICM-ID)系统中.信道容量仿真表明,所提方案在高、低信噪比区域都具有非常优越的互信息性能.误码率(BER)性能仿真表明,在BER为10-7时,联合LDPC(4599,4307)码的(2,6)-scheme 8APSK映射方案较(4,4)-scheme 8APSK映射方案、8PSK调制的格雷(Gray)映射、集分割(SP)映射、半集分割(SSP)映射分别提高了约0.45 dB、1.10 dB、1.62 dB、2.13 dB的编码增益.外附信息转移(EXIT)图仿真说明,所提方案能够更早地打开译码通道,从而更早地通过迭代来实现无错译码.     

Performance analysis of APSK modulation for DVB‐S2 transmission over nonlinear channels

For increased bandwidth efficiency and receiver performance, standards for satellite broadcasting systems are evolving by utilizing efficient transmission techniques. The second‐generation digital video broadcasting for satellites (DVB‐S2) adopts the amplitude phase shift keying (APSK) modulation for enhanced performance over nonlinear channels. In this paper, we derive error rate bounds for APSK modulated symbols and generalize the bounds to the case of distorted constellation, which occurs when the maximum transmission amplitude is saturated by the soft‐limiter type channel. The derived bound is shown to significantly improve the previously known result, to accurately predict both the symbol error rate and bit error rate in the entire signal‐to‐noise ratio (SNR) region of interest. Using the derived formula, the optimal input power level for the soft‐limiter channel is determined, and the corresponding minimal error rates for 16‐ and 32‐APSK are quantified. The result is also interpreted in terms of optimal input back‐off (IBO) for nonlinear power amplifiers by evaluating the performance degradation as a function of IBO. Copyright © 2009 John Wiley & Sons, Ltd.     

On the performance of BICM with mapping diversity in hybrid ARQ

Hybrid ARQ with packet combining for high‐order modulations (such as 16‐QAM) may be significantly enhanced if the bits‐to‐symbols mappings are appropriately changed throughout the transmissions. In this paper, we analyze the relationship between such mapping diversity and channel coding. We calculate the capacity of the popular bit‐interleaved‐coded modulation (BICM) to draw qualitative and approximate quantitative conclusions that are valid for strong codes approaching the capacity limits. We conclude that the choice/design of the appropriate mapping depends on the targeted spectral efficiency and we demonstrate that certain forms of mapping diversity may be counterproductive. We also show that iterative demapping may be successfully applied to significantly reduce (by more than 1 dB) the gap between the BICM and coded modulations (CM) capacities. The analysis is illustrated with results obtained when the mapping diversity is combined with practical turbo codes. Copyright © 2007 John Wiley & Sons, Ltd.     

一种8VSB Turbo格状编码调制方案

本文阐述这了一种适用于带限信道的８ＶＳＢ Ｔｕｒｂｏ格状编码制方案,它把纠错极强的Ｔｕｒｔｏ码和频带效率极高的格状编码调制结合,具有极强的信道传输能力。同时给出了相应的迭代译码算法及其误码率曲线。     

无线信道中网格编码调制技术研究

网格编码调制技术（TCM）是一种将编码与调制有机结合起来的技术,可使系统的频带利用率和功率资源同时得到有效利用。在对TCM原理和结构分析的基础上,研究了网格编码调制技术中的几个关键技术,主要包括集分割原理和无线信道下TCM误码率的分析,最后对无编码的QPSK与8PSK—TCM进行了仿真比较。仿真结果表明,在无线信道相同的误码率下,采用网格编码调制技术比未编码QPSK获得2dB的编码增益。     

A high‐speed long‐haul wavelength division multiplexing–based inter‐satellite optical wireless communication link using spectral‐efficient 2‐D orthogonal modulation scheme

In this work, we propose a novel multi‐bit/symbol spectral‐efficient optical orthogonal modulation scheme based on simultaneously modulating differential quadrature phase shift keying (DQPSK)‐polarization shift keying (PolSK) in a 16‐channel wavelength division multiplexing (WDM)‐based inter‐satellite optical wireless communication (IsOWC) system. Through numerical simulations, we demonstrate a reliable transportation of 16 × 100 Gbps information over 25 000 km of transmission range with acceptable bit error rate (BER) using the proposed system. Further, the impact of space turbulences (ie, pointing error losses) on the BER performance of the proposed IsOWC link has been evaluated using numerical simulations. The simulation results report a successful transportation of information up to 2.7 μrad receiver pointing error angle with acceptable performance.     

Novel Trellis‐Coded Spatial Modulation over Generalized Rician Fading Channels

In this paper, a novel trellis‐coded spatial modulation (TCSM) design method is presented and analyzed. Inspired by the key idea of trellis‐coded modulation (TCM), the detailed analysis is firstly provided on the unequal error protection performance of spatial modulation constellation. Subsequently, the Ungerboeck set partitioning rule is proposed and applied to develop a general method to design the novel TCSM schemes. Different from the conventional TCSM approaches, the novel one based on the Ungerboeck set partitioning rule has similar properties as the classic TCM, which has simple but effective code design criteria. Moreover, the novel designed schemes are robust and adaptive to the generalized Rician fading channels, which outperform the traditional TCSM ones. For examples, the novel 4‐, 8‐, and 16‐state TCSM schemes are constructed by employing different transmit antennas and different modulation schemes in different channel conditions. Simulation results clearly demonstrate the advantages of the novel TCSM schemes over the conventional ones.     

Rayleigh衰落信道中多级编码调制的不等错误保护

本文研究了Rayleigh衰落信道中以信道容量规则为设计准则的多级编码调制系统的不等错误保护性能的实现及其改进.在详细分析了多级编码调制的不等错误保护原理的基础上,设计了一种针对8ASK调制的非均匀信号星座.理论分析与计算机仿真均表明,非均匀信号星座的设计能够增强多级编码调制系统的不等错误保护能力,在不展宽频带的前提下有效地提高Rayleigh衰落环境下数字通信系统的传输质量.     

A QUASI-CONSTANT ENVELOPE QUADRATURE OVERLAPPED MODULATION AND ITS PERFORMANCE OVER NON-LINEAR BAND LIMITED SATELLITE CHANNELS

A new quadrature-overlapped modulation (QOTRC modulation) with a quasi-constant envelope is proposed in this paper. The new modulation possesses fast-decayed spectral side lobes. Bandwidth efficiency and detection efficiency of the new modulation under coherent detection over a band-limited non-linear satellite channel are studied and compared with those of MSK (a constant-envelope modulation) and SQORC (staggered quadrature-overlapped raised-cosine) modulations. The results obtained in this paper show that the new modulation can offer a satisfactory bit error rate (BER), which is comparable to or even better than that of MSK and much better than that of SQORC (a previously reported quadrature-overlapped modulation), depending on the signal-to-noise ratios (SNRs) and system bandwidth.     

基于非编码信息匹配的自适应Turbo TCM编码调制方案

本文提出了一种通过调整非编码信息量,并与信号映射相结合来改变编码、调制模式的自适应Turbo TCM编码调制方案,称之为基于非编码信息匹配的自适应Turbo TCM编码调制方案.由于将Turbo码和TCM编码调制技术相结合得到的Turbo TCM编码调制方案的带宽效率高,所以,在慢时变无线衰落信道中,自适应Turbo TCM编码调制的平均频谱效率也将很高.给出了该方案的工作原理、设计方法,并通过蒙特卡洛(Monte Carlo)仿真研究了该方案的性能.与现有编码调制方案相比,该方案具有频谱效率高、易于设计和实现的优点.     

基于TPC码的TPC-PPM编码调制及其在湍流下的仿真分析

针对大气光通信脉冲位置调制(PPM)调制方式与普通纠错编码结合有效性差的问题,在分析大气无线光通信信道特性和PPM符号形式的基础上,提出了具有良好抗衰落性能和高功率利用率的Turbo乘积码(TPC)-PPM编码调制机制.研究了该机制下比特交织离散连续错误能力,并导出了适合软输入输出(SISO)迭代译码的PPM软解调置信...     

Odd clipping optical orthogonal frequency division multiplexing for VLC system

The Orthogonal Frequency Division Multiplexing (OFDM) has emerged as one of the promising techniques because of its robustness to multipath fading with high‐speed data transmission. Classical bipolar OFDM cannot be used in intensity modulated with direct detection (IM/DD) optical communication systems, as visible light communication (VLC), so many optical modulation techniques as asymmetrical clipped optical OFDM (ACO‐OFDM) and DC‐Clipped OFDM (DCO‐OFDM) have been investigated. In this paper, we introduce a novel optical modulation scheme that meets the optical communications requirements. The proposed odd clipping optical OFDM technique (OCO‐OFDM) is based on the Fourier transform symmetry properties in which the imaginary and odd signal is converted to odd and real valued signal. As a result of this work, the proposed OCO‐OFDM and its modified version have several benefits over ACO‐OFDM and DCO‐OFDM. By introducing a better bit error rate, with the same spectral efficiency as DCO‐OFDM and the same power efficiency as ACO‐OFDM for real valued modulation technique as Binary Phase‐Shift Keying (BPSK), and with the same spectral efficiency and power efficiency as ACO‐OFDM for complex valued modulation technique as Quadrature Phase‐Shift Keying (QPSK) and Eight Phase‐Shift Keying (8PSK).     

Binary‐offset‐carrier modulation techniques with applications in satellite navigation systems

An important aspect in designing the modulation scheme for various satellite systems, such as the modernized GPS and Galileo, is to obtain good spectral properties and suitable spectral shaping. For example, in the future satellite navigation systems, some of the main goals are: low interference with the existing GPS signals, good root‐mean‐square (RMS) bandwidth, good time resolution (in order to allow the separation between channel paths and to decrease the synchronization errors) etc. Starting from the recently proposed cosine‐ and sine‐BOC modulation families for GPS and Galileo systems, we introduce a new, generalized family, denoted here by double‐BOC (DBOC) modulation. We derive and analyze the properties of the power spectral densities (PSD) and autocorrelation functions (ACF) of the DBOC modulation with various orders, we show its relationship with BPSK, sine‐ and cosine‐BOC modulations, and we illustrate via several examples how to choose optimally the parameters of this new modulation family, according to different optimization criteria. The examples are targeting at applications such as the design of suitable modulations for Galileo open service (OS) and public regulated service (PRS) signals, but the authors believe that the DBOC concept might be useful to other satellite‐based applications, when the available bandwidth is large enough. Copyright © 2006 John Wiley & Sons, Ltd.     

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.     

Low‐complexity de‐mapping algorithms for 64‐APSK signals

Due to its high spectrum efficiency, 64‐amplitude phase‐shift keying (64‐APSK) is one of the primary technologies used in deep space communications and digital video broadcasting through satellite‐second generation. However, 64‐APSK suffers from considerable computational complexity because of the de‐mapping method that it employs. In this study, a low‐complexity de‐mapping method for (4 + 12 + 20 + 28) 64‐APSK is proposed in which we take full advantage of the symmetric characteristics of each symbol mapping. Moreover, we map the detected symbol to the first quadrant and then divide the region in this first quadrant into several partitions to simplify the formula. Theoretical analysis shows that the proposed method requires no operation of exponents and logarithms and involves only multiplication, addition, subtraction, and judgment. Simulation results validate that the time consumption is dramatically decreased with limited degradation of bit error rate performance.     

Adaptive modulation and combining for bandwidth and power efficient communication over fading channels

Traditional fading mitigation techniques are designed relative to the worst‐case channel conditions, resulting in a poor utilization of the spectrum and the available power a good percentage of the time. In contrast, we introduce and investigate in this paper new adaptive modulation and diversity combining techniques that jointly select the most appropriate constellation size and the most suitable diversity branches in response to the channel variation and given a desired bit error rate (BER) requirement. Numerical results show that these newly proposed adaptive modulation and combining schemes can reduce considerably the average receiver channel estimation complexity as well as the power drain from the battery while offering high spectral efficiency and satisfying the desired outage probability and BER requirements. Copyright © 2006 John Wiley & Sons, Ltd.     

基于BICM的高效编码协作方案及性能分析

 提出一种基于比特交织编码调制(BICM)的高效编码协作(CC)方案,该方案中协作用户编码比特分为两帧,每一帧都通过BICM调制发送,通过结合比特交织器满足高阶调制星座符号的不同比特经历的衰落独立。一方面,论文分析了该协作方案在不同信道下的成对错误概率,并进一步推导了错误比特概率上界。理论分析以及仿真结果都表明：准静态衰落信道下,基于BICM的高谱效率编码协作方案仍然可以获得完全分集;而快衰落信道下,编码协作没有分集。另一方面,论文针对提出CC方案中映射方式以及交织器的设计进行研究,得出GRAY映射仍然是协作用户采用的最佳映射,且两帧的交织器不同更利于提高性能。     

基于互信息分析的编码调制方案选择

在数字通信系统中,将信道编码和调制技术结合在一起可以得到许多编码调制方案。有些编码调制方案可以达到相同的频谱效率,但传输可靠性并不相同。提出了一种基于互信息分析的编码调制方案选择方法,通过计算星座受限条件下的信道容量,根据给定的信道条件,选择合适的编码调制方案。     

Classification of linear and non-linear modulations using the Baum–Welch algorithm and MCMC methods

Satellite transmissions classically use constant amplitude linear modulation schemes, such as M-state phase shift keying (M-PSK), because of their high robustness to amplifier non-linearities. However, other modulation formats are interesting in a satellite transmission context. For instance, non-linear modulations such as Gaussian minimum shift keying (GMSK) present a higher spectral efficiency and appear in new standards for telemetry/telecommand satellite links. Another example is offset-QPSK (OQPSK) modulation that allows one to decrease the out-of-band interference due to band limiting and the non-linearity of the amplifier. To get a compromise between the robustness to amplifier non-linearities provided by MPSK modulation and the spectral efficiency given by QAM modulation, the recent broadcasting satellite standard (DVB-S2) proposes new modulation schemes called APSK. Obviously, all satellite systems that use various modulation schemes will have to co-exist. In this context, modulation recognition using the received communication signal is essential. In that context, this paper studies two Bayesian classifiers to recognize linear and non-linear modulations. These classifiers estimate the posterior probabilities of the received signal, given each possible modulation, and plug them into the optimal Bayes decision rule. Two algorithms are used for that purpose. The first one generates samples distributed according to the posterior distributions of the possible modulations using Markov chain Monte Carlo (MCMC) methods. The second algorithm estimates the posterior distribution of the possible modulations using the Baum–Welch (BW) algorithm. The performance of the resulting classifiers is assessed through several simulation results.