Performance of terahertz channel with multiple input multiple output techniques

Terahertz(THz) communication is being considered as a potential solution to mitigate the demand for high bandwidth. The characteristic of THz band is relatively different from present wireless channel and imposes technical challenges in the design and development of communication systems. Due to the high path loss in THz band,wireless THz communication can be used for relatively short distances. Even,for a distance of few meters( > 5 m),the absorption coefficient is very high and hence the performance of the system is poor. The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last two decades.Multiple Input Multiple Output( MIMO) Spatial diversity technique has been exploited in this paper to improve the performance in terahertz band. The results show that the Bit Error Rate( BER) is considerably improved for short distance( < 5 m) with MIMO. However,as the distance increases,the improvement in the error performance is not significant even with increase in the order of diversity. This is because,as distance increases,in some frequency bands the signal gets absorbed by water vapor and results in poor transmission. Adaptive modulation scheme is implemented to avoid these error prone frequencies. Adaptive modulation with receiver diversity is proposed in this work and has improved the BER performance of the channel for distance greater than 5 m.

Orthogonal frequency division multiplexing for improving the performance of terahertz channel

Terahertz( THz) communication is considered to be one of the demanding technology for the upcoming 5G standards. The incredible demand for high rate through wireless channel necessitates the use of THz frequency for communication. The development of communication systems in this frequency band possess technical challenges as the characteristic of THz band is very different from the present wireless channel. However,the advancements in the development of transceiver and antenna systems are rapidly bringing the THz communication into reality. The high path loss in THz band limits the communication range of this channel. Even,for a distance of few meters( >5 m),the absorption coefficient is very high and hence the performance of the system is poor. Performance over this frequency channel can be enhanced by considering transmission windows over this band instead of the entire band. The transmission windows are the frequencies over which the absorption is relatively low. Though there is an improvement in the performance with this adaptive modulation scheme,but not sufficient for longer distance. Apart from path loss,the frequency selective nature of this high bandwidth channel is also a major reason for the poor performance of THz channel. Orthogonal Frequency Division Multiplexing( OFDM) is a promising solution to mitigate the effects of frequency selective nature of the wireless channel. OFDM has been exploited in this paper to improve the performance of terahertz channel. The results show that the Bit Error Rate( BER) of the terahertz channel is considerably improved with OFDM.

Performance analysis of LDPC codes on OOK terahertz wireless channels

Atmospheric absorption, scattering, and scintillation are the major causes to deteriorate the transmission quality of terahertz（THz） wireless communications. An error control coding scheme based on low density parity check（LDPC） codes with soft decision decoding algorithm is proposed to improve the bit-error-rate（BER） performance of an on-off keying（OOK） modulated THz signal through atmospheric channel. The THz wave propagation characteristics and channel model in atmosphere is set up. Numerical simulations validate the great performance of LDPC codes against the atmospheric fading and demonstrate the huge potential in future ultra-high speed beyond Gbps THz communications.

面向太赫兹通信覆盖增强的确定性信道建模分析

作为6G网络关键候选技术之一的太赫兹通信,其严重的路径损耗和阻塞敏感性对太赫兹信号覆盖范围造成了极大限制。一系列的太赫兹通信覆盖增强技术被提出。为了更好地在实际环境中对覆盖增强技术进行个性化的设计与部署,针对相应太赫兹无线信道展开建模分析。介绍了太赫兹通信的确定性信道建模方法,针对射线追踪(Ray Tracing, RT)方法进行了探讨,阐述了辅助太赫兹通信覆盖增强的相关技术。基于RT方法构建了面向太赫兹通信覆盖增强的确定性信道模型实例,验证了相关技术对太赫兹通信覆盖具有增强的效果,并对建模的相应挑战展开了讨论。对RT方法在未来太赫兹通信技术的应用进行了展望。

基于机器学习的太赫兹信道预测建模研究

针对6G移动通信的通信场景复杂化、数据海量化,以及传统信道建模方法带来的测量成本昂贵、建模复杂度高等挑战,将机器学习中的反向传播神经网络(Back Propagation Neural Network,BPNN)应用到室内太赫兹信道建模中,有效降低了建模复杂度,提高了建模效率。建立了基于遗传算法(Genetic Algorithm,GA)和蚁群算法(Ant Colony Optimization,ACO)混合优化的BPNN信道参数预测模型,对太赫兹无线信道的大小尺度特性进行了学习与预测,并与传统的BPNN模型、GA-BP和ACO-BP的预测结果进行了比较,验证了所建立模型的准确性和有效性。结果表明,遗传蚁群反向传播(Genetic Algorithm-Ant Colony Optimization-Back Propagation,GA-ACO-BP)模型的预测值和实际值间的误差更小、拟合度更高,该模型的预测性能相较于其他3种模型更优。基于GA-ACO混合优化的BPNN能够在小数据量的情况下对信道参数进行学习和预测,可用于未来基于测量的无线信道建模分析中。

太赫兹近场通信信道特性研究综述

为满足不断提高的数据传输需求,未来的通信技术会向更高的载波频率发展,基于太赫兹频段的通信可实现高稳定性和高数据速率通信。本文综述了太赫兹近场信道特性及信道建模的研究进展,介绍了太赫兹频段下对近场信道分析的必要性,对比了远近场信道的区别;针对太赫兹近场通信信道,介绍了球面波前建模与基于电磁波理论的模型;结合信道建模技术与近场信道特点,介绍了可用于近场信道建模的方法论;最后对太赫兹近场信道特性研究进行了总结并对未来发展方向进行了展望。

太赫兹通信发展概述

第6代移动通信(6G)预计在未来提供低延迟、低功耗、高容量和大规模的通信服务,太赫兹通信具有大带宽、高速率和低延迟的特点,被视为6G时代的关键技术路线。文章介绍了太赫兹通信系统信号产生技术路线、信号接收技术、信号传输特性和信道建模,并分析了超大规模多输入多输出技术、智能反射面和关键太赫兹器件等技术问题的进展与挑战。此外,还探讨了太赫兹通信在短距离超高速通信、空间通信、微尺度通信和高保密通信领域的潜在应用。尽管存在一些技术障碍,但随着研究的深入,太赫兹通信相关难题定会逐步解决,6G时代的到来预计将不再遥远。

太赫兹频段室内场景空-时域信道特性测量与建模研究

掌握太赫兹频段室内信道特性及模型,是太赫兹室内通信系统设计和技术评估的前提。为了解太赫兹频段室内空-时域的信道特性,选取典型室内办公室场景,分别完成视距(Line of Sight, LoS)和非视距(Non Line of Sight, NLoS)场景下100 GHz频段、带宽为1.2 GHz的信道测量。通过分析结果,发现两场景的均方根时延扩展值和均方根角度扩展值都服从正态分布,且NLoS场景的两种参数值都比LoS场景大。此外,由于太赫兹频段多径信号分量较少,且测量场景尺寸较小,使得实测的均方根时延扩展值的测量结果比3GPP标准值约小12 ns。通过建立对数距离模型探讨测量距离对两种参数的影响,发现均方根角度扩展值在NLoS场景中随距离的增加有上升趋势,而均方根时延扩展值在两场景中变化趋势相反。

室内太赫兹无线信道模型研究现状

室内太赫兹无线信道模型研究是无线通信领域的热门课题之一。随着物联网、5G和未来通信技术的快速发展,太赫兹频段因其大带宽和高数据传输速率的潜力引起了广泛关注。对室内太赫兹无线信道模型及建模方法的研究现状进行了综述。介绍了太赫兹频谱特性、大小尺度衰落等太赫兹信道传播特性。对太赫兹信道中路径损失、信道冲击响应(Channel Impulse Response,CIR)/信道传递函数(Channel Transfer Function,CTF)、功率时延谱(Power Delay Profile,PDP)、时延扩展(Delay Spread,DS)、到达时间(Time of Arrival,ToA)、角度扩展(Angular Spread,AS)和到达角度(Angle of Arrival,AoA)等重点参数的研究现状进行了梳理,并在此基础上将信道建模方法归纳为三大类,分别为确定性信道建模、统计性信道建模和混合信道建模。针对每种建模方法,分析了现有相关研究路线的优势及现状。对太赫兹无线信道建模的未来发展进行了展望。

Channel characterization at 120 GHz for future indoor communication systems

We present a simulation on the spatial and temporal characteristics of the indoor propagation channel at 120 GHz. The simulation, applied to a dynamic scenario with randomly placed objects and moving people in a room, is based on a three-dimensional ray-tracing method. Propagation and reflection mechanisms of electromagnetic waves are discussed in the channel model. The received power in a 0.95-m-height plane is obtained. Comparison between walls and ceiling covered with dielectric mirrors and those with three common wall and ceiling materials are presented. The result shows that the holistic received power level with dielectric mirrors is about 10 dB higher than with other materials.

A Survey on Terahertz Communications

With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.

60 GHz与300 GHz频段航天器舱内通信信道特性

太赫兹(THz)技术有望在航天器舱体轻质化和舱内高容量传输需求方面发挥重要作用.本文构建了典型航天器舱内毫米波60 GHz与太赫兹300 GHz频段信道三维仿真模型,基于射线追踪法获取了两种典型发射机部署位置下的无线信道特性,提取并分析了路径损耗指数、阴影衰落因子、莱斯K因子、均方根时延扩展和角度扩展等关键信道参数,研究了发射机的部署位置对特定频段舱内信道的影响.结果表明:相同环境下,频率越高、路径损耗与莱斯K因子越大而时延扩展越小;相同频率下,发射机部署于舱内角落的信道特性优于部署于舱内上壁中央.本文所研究的无线信道特性将为未来复杂舱内环境下的太赫兹通信系统设计和部署提供启示.

太赫兹通信中MIMO信道建模与容量分析

随着纳米技术的不断发展与新型纳米材料石墨烯研究的不断深入,作为纳米网络通信技术的太赫兹通信成为无线通信的研究热点,然而现阶段对太赫兹通信中多输入多输出(MIMO)机制的研究较少。为此,采用离散化的数学方法,以接收端获取信道信息的遍历容量模型为基础,结合太赫兹信道的分子吸收噪声与传输路径损失,提出一种适用于太赫兹通信的MIMO信道模型。对建立的MIMO信道模型进行仿真与分析,结果表明,与单一太赫兹信道相比,太赫兹通信中的MIMO信道具有更高的信道容量与传输比特率。

太赫兹通信技术综述

太赫兹频段(0.1~10 THz)信号在空气中传播衰减大、传输距离短,在太赫兹通信技术得到广泛应用之前,这些关键问题需要攻克。首先,介绍了当前太赫兹信道的研究进展,包括信道建模、信道测量及信道估计。在此基础上,分析了单用户基本通信场景和多用户复杂通信场景,并针对各个场景中存在的问题列举了可能的解决方案。最后,展望了太赫兹通信未来可行的研究方向。

太赫兹通信关键技术及挑战分析

太赫兹通信支持超大工作带宽和超高通信速率,是具备高应用潜力和影响因子6G关键候选技术。文章分析探讨太赫兹通信面向未来应用的关键技术方向及问题挑战,包括关键器件/芯片/天线、太赫兹波传播特性及信道建模,以及太赫兹通信空口设计等,并提出发展建议。

太赫兹频段星地通信信道建模与仿真

太赫兹频段作为至今尚未被完全开发的超高通信频段,具有超大带宽等优点,将其应用于第五代(the 5th Generation,5G)、后五代(Beyond 5G,B5G)移动通信系统,除实现更高速率传输外,还可实现地面移动网络与卫星网络频谱资源的共享,有利于推动新一代空天地一体化通信网络建设.文章提出了一种适用于星地通信系统的太赫兹信道建模与仿真方法,分析了自由空间损耗、分子吸收损耗、云雾衰减、雨衰减及多普勒频移等太赫兹信道的影响因素,构建了星地太赫兹通信信道建模流程,并给出了分步骤信道参数的生成方法.通过数值仿真,对不同天气状况下传输距离和频率对传输信号的影响进行了分析,并基于所生成的信道响应对误码率进行评估,从而验证了所提出模型和方法的可用性.所提建模方法能够提供不同传输条件下的动态太赫兹信道响应数据,从而为今后太赫兹频段无线通信系统的设计与开发提供评估与测试依据.

面向6G的太赫兹信道特性与建模研究的综述

综述了太赫兹信道特性与建模的研究进展。首先,对比分析了太赫兹与低频段信道不同的传播特性,例如分子吸收特性,障碍物表面粗糙度对折射、反射系数的影响特性以及太赫兹波的物理特性等。其次,介绍了两种常用信道建模方法,即统计性和确定性信道建模。最后,总结了基于两种建模方法的太赫兹信道建模的近期研究进展。

太赫兹无线信道的测量、建模和分析

太赫兹通信有望成为第六代移动通信网络的关键技术之一。为实现太赫兹通信,对太赫兹无线传播信道的研究不可或缺。首先,介绍了3种主要的太赫兹信道测量方法,包括基于矢量网络分析仪的频域信道测量、基于滑动相关的时域信道测量和基于太赫兹脉冲的时域信道测量;其次,对现有的信道建模方法进行了介绍和分析,包括确定性建模、随机建模和混合建模方法;然后,基于现有的太赫兹信道测量结果,分析总结了太赫兹频段的信道特性;最后,阐述了太赫兹无线信道领域潜在的研究方向。

空间太赫兹通信信道建模技术

近年来,太赫兹频段成为下一代卫星通信频率拓展的重要方向。随着太赫兹器件的发展,空间太赫兹通信系统的研究与设计引起了许多研究人员的兴趣,而空间太赫兹通信信道建模是研究与设计空间太赫兹通信系统的基础。本文对空间太赫兹通信信道建模技术的相关研究进行综述。首先介绍空间太赫兹通信频段的传播特点;其次讨论空间太赫兹通信信道模型的分类以及不同场景下信道建模需要考虑的因素,回顾各个因素的研究进展;最后对目前的研究成果进行总结,同时对未来的研究方向进行展望,为未来太赫兹技术在卫星通信领域的应用提供理论依据。