可见光通信极性索引正交频分复用技术研究

为了抑制可见光通信(VLC)正交频分复用(OFDM)系 统发光二极管(LED)非线性限幅失真,提出了一种极性 索引OFDM(PIM-OFDM)调制方式。PIM-OFDM通过两个模块分别传输直流偏置 光OFDM(DCO-OFDM)双极性信号的极性信息和幅度信息。在第1模块中,对双极性信号的正 负极性编码并使用 OOK信号传输。在第2模块中,对双极性信号取绝对值得到幅度信息。在相同条件下,PIM- OFDM系统 性能比非对称限幅OFDM(ACO-OFDM)系统提升了接近 3dB。在光功率约束 条件下,在最 大有效(SNR)原则下得到了直流偏置和输入信号的最优功率分配。 仿真结果表明:光功率约束较小时,有 效SNR随着直流偏置增大而变小;光功率约束较大时,有效SNR随着直流 偏置增大会先增大后减小。 实验结果表明:在相同传输速率的情况下,PIM-OFDM误码率(BE R)性能要比ACO-OFDM提升1个数量级。     

Effects of Direct Current Bias-Drifting on Radio on Fiber Link

The effects of direct current (dc) bias-drifting on radio on fiber (RoF) links are quantitative investigated and simulated. Single sideband (SSB) modulation and carrier suppressed double sideband (CS-DSB) modulation RoF links are considered, power variation of targeted signal and harmonic suppression on account for bias-drifting are calculated and evaluated. Our results suggest that power variation can be maintained within 1.1 dB with dc bias drift ε less than 5% in the SSB modulation RoF link and the degradation of harmonic suppression is evident with ε exceed 2% in the CS-DSB modulation RoF link.     

Constellation design and performance analysis of the parallel spatial modulation

Spatial modulation (SM) is a relatively recent multiple‐input multiple‐output (MIMO) system in which information is carried by the index of the antenna used for transmission as well as by the conventional signal symbols. Several systems that build upon SM have since been proposed including the generalized SM (GSM), a variant of GSM with multiple active antennas (MA‐SM), quadrature SM (QSM), and parallel SM (PSM), among others. The PSM system can increase the spectral efficiency by splitting the antenna set into groups and applying SM independently in each group using the same signal symbol. In this paper, we first derive the upper bound on the error probability of the PSM. The search of the optimal constellation set is then formulated as a multi‐objective optimization problem, where the obtained constellation minimizes the asymptotic error probability. We conclude that as the number of antenna groups increases, the proposed constellation converges to the conventional phase‐shift keying at relatively low number of transmit antennas. The simulation results show that the proposed constellation outperforms conventional constellations by as much as 5 dB, for high‐modulation orders. Since the multi‐objective optimization is independent of the channel matrix, it can be easily done off‐line. This implies that these gains come at no complexity or delay cost.     

基于MIMO信道估计误差模型的功率分配与自适应调制算法

该文分析了瑞利平坦衰落信道下,信道估计误差对采用迫零接收的MIMO系统性能的影响,提出了一种以系统有效吞吐量最大化为目标的功率分配与自适应调制算法。为了减少信道估计误差对实际系统性能的影响,该算法对发送端估计的信噪比进行修正,并以此作为功率分配和自适应调制的依据。在系统总功率受限的条件下,对发端多天线的功率分配结合了空域注水定理和比特分配,并尽量保证调制阶数高的数据符号所在天线的功率。仿真结果表明,该算法实现较简单,获得的系统有效吞吐量接近于最优值,适用于实际系统。     

基于单MZM和FBG的10倍频抑制载波RoF系统

为优化光载无线通信系统(RoF)结构,提出了一种基于单马赫曾德尔外调制器(MZM)和光纤布拉格光栅(FBG)的10倍频抑制载波RoF系统实现方案。通过设置射频驱动信号幅度和MZM偏置电压抑制主载波和偶数阶边带,结合FBG滤波功能,最终实现10倍频RoF毫米波信号。理论推导了10倍频毫米波信号实现机理,优化了FBG带宽及反射率,实验结果表明该新型RoF系统传输20 km后功率代价为1.66 dB。     

A 60-GHz-Band Analog Optical System-on-Package Transmitter for Fiber-Radio Communications

We developed an analog optical system-on-package (SoP) transmitter for a 60-GHz-band radio-over-fiber (RoF) link. The SoP transmitter consisted of an electroabsorption modulator, radio frequency amplifiers, and a bandpass filter. The 60-GHz RoF wireless link was prepared to measure the performance of the SoP transmitter. The transmission characteristics of 64-quadrature amplitude modulation (64-QAM) data of the 60-GHz RoF wireless link, including the SoP transmitter, were investigated by measuring the error vector magnitude (EVM) and signal-to-noise ratio (SNR) with a baseband frequency. The EVM of the 60-GHz RoF wireless link was between 2.25% and 2.80%, and the SNR was between 27.36 and 29.31 dB from 140 and 770 MHz, at input baseband power of -9 dBm. The noise figure had the minimum of 8.44 dB at 500 MHz. We successfully transmitted digital community antenna television (CATV) system signals through the 60-GHz RoF wireless link, including the SoP transmitter. Digital CATV signals of 86 channels could be transmitted through the 60-GHz RoF wireless link, and the total throughput was found to be 2.61 Gb/s.     

Resource allocation for sum-rate maximization in NOMA-based generalized spatial modulation

The Multiple-Input Multiple-Output (MIMO) Non-Orthogonal Multiple Access (NOMA) based on Spatial Modulation (SM-MIMO-NOMA) system has been proposed to achieve better spectral efficiency with reduced radio frequency chains comparing to the traditional MIMO-NOMA system. To improve the performance of SM-MIMO-NOMA systems, we extend them to generalized spatial modulation scenarios while maintaining moderate complexity and fairness. In this paper, system spectral efficiency and transmission quality improvements are proposed by investigating a sum-rate maximization resource allocation problem that is subject to the total transmitted power, user grouping, and resource block constraints. To solve this non-convex and difficult problem, a graph-based user grouping strategy is proposed initially to maximize the mutual gains of intragroup users. An auxiliary-variable approach is then adopted to transform the power allocation subproblem into a convex one. Simulation results demonstrate that the proposed algorithm has better performance in terms of bit error rate and sum rates.     

一种适用多种空时编码方案的MIMO自编码器通信系统

为提升现有端到端通信系统的适应性与信道估计的准确性,提出了一种适用于多种空时编码方案的多输入多输出(Multiple-Input Multiple-Output,MIMO)自编码器通信系统.该系统将基于卷积神经网络的自编码器引入到MIMO系统中,并结合信道估计网络实现信道均衡,通过端到端的学习方式实现各种空时编码方案下...     

非限幅QPSK类正弦调制大气激光通信系统的性能研究

提出了一种非限幅四相相移键控(QPSK)类正弦调制技术,并将其运用到大气激光通信系统中。介绍了大气激光通信信道模型,给出了非限幅QPSK类正弦调制的大气激光通信系统模型。在此基础上,对采用非限幅QPSK类正弦调制和采用直流偏置副载波强度调制的大气激光通信系统在无湍流和弱湍流信道下的功率利用率、误码率、中断概率和信道容量进行了分析和比较。结果表明,非限幅QPSK类正弦调制具有更好的抗噪声性能、更高的功率利用率、较低的中断概率及较高的信道容量,提高了大气激光通信系统的性能,可满足大气激光通信系统的需要。     

60 GHz RoF系统功率设计及分配

文章以Matlab为编程、分析工具,运用上、下行链路分离正序法对60 GHz射频光纤(RoF)系统进行功率设计、计算及分配,其中包括对RoF系统中光器件光功率的设计、无线传输部分电功率的估计以及对上行链路重要接收点的信噪比分析.通过系统的功率分配设计,对RoF系统的可实现性、合理性和稳定性做出必要的分析.最后,依据设计方案和功率计算结果,建立实际、可行的60 GHz RoF系统.     

On the design considerations of solid-state power amplifiers for satellite communications: A systems perspective

Conventional solid-state power amplifier (SSPA) design approach isolates radio frequency (RF) design from communication theory. In this paper, a unified SSPA design approach is proposed, which optimizes SSPA parameters (bias voltage and input RF signal power) to minimize total DC power consumption while satisfying received SNR constraint specified by the link budget. The effect of SSPA nonlinearity is quantified by the error vector magnitude measured at its output and the corresponding received SNR degradation is analyzed. Using the quantitative metrics for received SNR, it is possible to evaluate highly nonlinear SSPA classes such as Class-B or deep-Class AB, which are normally not considered in conventional SSPA design approach to be used in satellite communication applications.     

MIMO System Optimization Using STTC Based STBC with Channel Estimation

We propose a new architecture involving space time trellis code (STTC) concatenated with space time block code (STBC) using modified sphere decoder (MSD-1) at the receiver for improving system performance in the multi-antenna environment. With the aim of increasing the ??Diversity Order?? of signal set, rotated versions of quadrature amplitude modulation (QAM) constellation have been used in multidimensional space and the associated design parameters required to search an effective signal constellation have been optimized. The limitations on account of complexity owing to multiple copies of data being received after experiencing various channel effects in the multi input multi output (MIMO) systems have been looked into. Accordingly, MSD-1 algorithm has been proposed with lower complexity, which in turn would give rise to a system with high spectral efficiency. The system gains have been verified with channel state information (CSI) errors.     

基于双平行MZM调制器的矢量毫米波信号传输性能分析北大核心CSCD

提出了一种基于双平行马赫-曾德尔调制器(dual parallel Mach-Zehnder modulators,DP-MZM)的单边带矢量毫米波信号产生和传输方案,在MATLAB和VPI联合仿真环境下分析了90 GHz波段不同调制格式信号的产生和传输性能。仿真中,DP-MZM工作在光载波抑制(optical carrier suppression,OCS)模式时,小信号驱动的两个子调制器输出的单边带信号相互叠加后,无需使用滤波器,可以实现完全抑制中心载波的效果。结果表明:经过该系统传输后,各调制信号的误码率(bit error rate,BER)均可达到硬判决前向纠错(hard judgment forward error currection,HD-FEC)阈值。概率整形后正交幅度调制信号的误码性能明显优于均匀正交幅度调制信号,其中,7 bit/symbol概率整形256阶正交幅度调制(probability shaping 256 quadrature amlitude modulation,PS-256QAM)信号经过系统传输后功率增益最为明显,经过50 km光纤传输后,提升了2.94 dB的功率增益。与目前存在的载波抑制毫米波产生方案相比,该系统结构相对简单,可调节度高,信号传输增益明显,因此具有一定的应用价值。     

大规模MIMO系统多用户PSK调制方案的优化

针对超可靠低时延通信短包传输特征,在大规模多输入多输出( Multiple-Input Multiple-Output,MIMO)上行链路系统中,利用较低导频开销来设计相移键控( Phase Shift Keying,PSK)调制方案,并对该方案进行优化兼顾无线链路传输的可靠性.首先,在接收端构建基于最小欧式距离的非相...     

Adaptive modulation with constrained variable power for space–time coded MIMO systems

Practically, the maximum transmission power of transmission systems is limited. This power constraint causes the variable power control derived from no maximum power limitation suffering from performance degradation. In this paper, a constrained variable‐power adaptive M‐ary quadrature amplitude modulation scheme for MIMO systems with space–time coding is developed. Convex optimization is used to derive the switching thresholds of the instantaneous signal‐to‐noise ratio for power control (PC) and adaptive modulation under the constraints of maximum power, average power, and target BER. In the derivation of the relation between modulation and power, the exact BER expression of binary phase shift keying modulation and a tight bound for higher order quadrature amplitude modulation are used to make the PC scheme fulfill the target BER even at low signal‐to‐noise ratio where the previous PC schemes fail to meet the target BER. Numerical results show that the derived control scheme under the power constraints can obtain the spectrum efficiency and BER performance close to the previous control scheme without power limitation. Moreover, it can satisfy the requirements of power limitation and target BER and can effectively avoid the excessive power consumption of previous PC scheme in poor channel condition. Copyright © 2012 John Wiley & Sons, Ltd.     

广义正交码索引调制系统的性能分析

摘 要：为了提高码索引调制（code index modulation，CIM）系统的传输效率，提出了一种具有更低复杂度的单输入单输出（single input single output，SISO）的广义正交码索引调制（generalized orthogonal code index modulation，GQCIM）系统。CIM 系统使用扩频码和星座符号传输信息，但只能激活两个扩频码索引和一个调制符号。而 GQCIM 系统以一种新颖的方式克服了只激活一个调制符号的限制，同时充分利用了调制符号的正交性，增加扩频码索引以传输更多的额外信息位，提高了系统的传输效率。此外，分析了GQCIM系统的理论性能，推导了误码率性能的上界。通过蒙特卡罗仿真验证了GQCIM系统的性能，对比发现GQCIM系统的理论和仿真性能一致。而且在相同的传输效率下，结果显示GQCIM系统的性能优于同样具有正交性的调制系统，如广义码索引调制（generalized code index modulation，GCIM）系统、CIM系统、码索引调制-正交空间调制（code index modulation aided quadrature spatial modulation，CIM-QSM）系统、码索引调制-正交空间调制（code index modulation aided spatial modulation，CIM-SM）系统、脉冲索引调制（pulse index modulation，PIM）系统。     

A novel turbo GFDM-IM receiver for MIMO communications

Generalized frequency-division multiplexing (GFDM) is a candidate waveform for the fifth generation (5G) wireless communication systems. However, the carrier frequency offset (CFO) causing synchronization problem is very important for GFDM system. In this paper, we propose a turbo receiver with channel estimation, equalization and CFO compensation for MIMO (multiple input multiple output) GFDM system with index modulation (IM). So far, no related researches exist. This paper proposes a novel receiver to solve CFO compensation with two-path transmission and proposes a modified phase rotated conjugate cancellation (PRCC) algorithm for the receiver. On the other hand, GFDM with index modulation (GFDM-IM) can achieve better performance and lower peak-to-average power ratio (PAPR) than those of GFDM by using active index subcarrier. To reduce the system complexity, the log-likelihood ratio (LLR) criteria is also employed to search which subcarrier is active. Moreover, the Kalman filter is employed to trace the time-varying channels. The initial channel estimation is performed by the sparse pilot signals. In the simulations, we compare the proposed receiver with several existing schemes in different time-varying channels and modulations. The proposed scheme outperforms the existing schemes.     

一种载边比可调单边带全双工光载无线系统

理论分析了一种基于双平行马赫曾德尔调制器(MZM)的2 倍频光单边带调制方案,仿真研究了基于 该方案的载波重用全双工光载无线(RoF)通信系统性能。合理设置射频驱动信号相移及双平行MZM 主调制器偏置 电压产生单边带信号,再调整调制指数以实现光载边比ROCS 的连续可调谐。讨论了射频信号相移、主调制器偏置电 压、双平行MZM 消光比RE 和调制指数对ROCS 的影响,理论分析与仿真结果较为一致。结果表明经20 km 光纤传输 后,在误码率BER 为10-9 时0 dB 和10. 33 dB 载边比系统的功率代价分别为2.5 dB 和3.4 dB,在背靠背(BtB)传输 中当载边比从10. 33 dB 降低至0 dB 后,接收机灵敏度提高了2.6 dB。     

一种新的高效自适应的联合编码调制分集的多入多出系统

为满足未来移动通信对高数据传输速率迅速增长的需求,本文提出了高频谱效率的联合编码调制分集(Joint Coding Modulation Diversity,JCMD)的多输入多输出(Multiple-Input Multiple-Output,MIMO)方案.从全局的角度,该方案通过空时分量交织器和旋转调制对Turbo编码,正交幅度调制(Quadrature Amplitude Modulation,QAM)和MIMO技术进行联合优化.本文首次证明了JCMD-MIM的可达速率大于等功率分配的BICM-MIMO系统.基于以上理论分析,提出了一种最佳空间分量交织器以及自适应层数选择方案以最大化系统的可达速率.仿真结果表明新方案与传统的BICM-MIMO方案相比可以获得明显的信噪比增益.     

基于调制边带法的高次倍频光毫米波产生

提出了利用外调制技术的调制边带法的六倍频和八倍频光毫米波产生方案。方案仅采用一个马赫曾德尔调制器,并利用其非线性传输特性,通过调节MZM 的偏置电压和调制电压,控制边带的强度,仅保留三阶边带或四阶边带,从而实现六倍频及八倍频光毫米波的产生。采用将基带数据信号仅调制在一个三阶边带或四阶边带分量的方式,有效防止走离。数值分析结果表明,提出的方案仅需10 GHz 及7.5 GHz 的调制信号频率就能得到60 GHz 毫米波,大大减小了调制信号频率,增加了上变频系数,传输距离可达160 km,而功率代价变化不大。与提出的其他高倍频技术相比,由于系统仅采用一个马赫曾德尔调制器,提出的方案系统结构更为简单,且此方案色散影响较小,传输距离更长。