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Chirp-spreaded ofdm-mfsk with differentially encoded phase for applications in low-power wide-area networks

COMPUTERS & ELECTRICAL ENGINEERING 2023年 105卷

作者： Thiasiriphet, Thanawat Teich, Werner G. Chiang Mai Univ Fac Engn Ctr Mechatron Syst & Innovat Dept Elect Engn Chiang Mai Thailand Ulm Univ Inst Commun Engn D-89069 Ulm Germany

For the unlicensed frequency bands, long-range wide-area networks (LoRaWAN) is a widespread solution for low-power wide-area networks. The physical layer of LoRaWAN is long range (LoRa) which uses a combination of chirp spread spectrum (CSS) and M-ary frequency-shift keying (M-FSK) for transmission. LoRa is known to be highly robust and well-suited for low-complexity implementation, but the weak aspect is its low spectral efficiency. Orthogonal frequency division multiplexing M-FSK (ofdm-mfsk) is a technique which combines M-FSK with ofdm. The bandwidth is divided into several parallel M-FSK transmissions, i.e., more than one sub-carrier is active at a time. This leads to an increased peak-to-average power ratio of the transmit signal. On the other hand, it allows to combine ofdm-mfsk with differential phase-shift keying (DPSK) to increase the data rate and thus the spectral efficiency. The reception of ofdm-mfsk as well as the DPSK demodulation can be done non-coherently. Therefore, they hold many similar design principles as LoRa. We propose a combination of ofdm-mfsk with differentially encoded phase and CSS. Simulation results show, that LoRa and ofdm-mfsk with CSS show similar performance with respect to power and bandwidth efficiency. Adding DPSK leads to an improved spectral as well as power efficiency.

关键词： ofdm-mfsk Chirp spread spectrum DPSK LoRa Non-coherent detection PAPR LPWAN IoT

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A Novel Weighted LLR Algorithm for Non-Coherent ofdm-mfsk System in Ionospheric Scatter Channel

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IEEE COMMUNICATIONS LETTERS 2022年第6期26卷 1383-1387页

作者： Ding, Jian Niu, Xiaoming Hao, Shuji Li, Qingliang Ren, Guangliang Xidian Univ State Key Lab Integrated Serv Networks Xian 710071 Peoples R China China Res Inst Radiowave Propagat Natl Key Lab Electromagnet Environm Qingdao 266107 Peoples R China

A novel weighted log likelihood ratio (LLR) algorithm is proposed for the non-coherent orthogonal frequency division multiplexing with M-ary frequency shift keying (ofdm-mfsk) system in an ionospheric scatter channel (ISC) with serious frequency-selective fading. In the algorithm, the bit LLR is derived according to the probability distribution of non-coherent received signals in the mfsk symbol and is approximately simplified to a concise expression, which reveals that lilts cannot indicate the effect of the frequency-selective fading channel on different mfsk symbols. The proposed weighted LLR algorithm maximizes the signal-to-noise ratio (SNR) of the metric combined with LLRs in channel decoding. The weighted factors were estimated blindly from the received mfsk signals. Simulation results show that the bit error rate (BER) of ofdm-mfsk systems with the proposed LLR-weighted algorithm is superior than that of conventional LLR algorithms, and has approximately 1.6 dB SNR gain when BER is 10(-4).

关键词： Ionospheric scatter channel LLR weighted ofdm-mfsk non-coherent detection

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Combining ofdm-mfsk and Chirp Spread Spectrum Modulation for Applications in Low-Power Wide-Area Networks 15

Combining OFDM-MFSK and Chirp Spread Spectrum Modulation for...

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15th International Conference on Signal Processing and Communication Systems (ICSPCS)

作者： Thiasiriphet, Thanawat Teich, Werner G. Chiang Mai Univ Dept Elect Engn Fac Engn Ctr Mechatron Syst & Innovat Chiang Mai Thailand Ulm Univ Inst Commun Engn D-89069 Ulm Germany

ISBN: (纸本)9781665436991

Chirp spread spectrum (CSS) has attracted a lot of interest in the last few years, especially in the field of low-power wide-area networks (LPWAN). One of the most commonly employed LPWANs solution is LoRaWAN, which has LoRa as its physical layer. The concept of LoRa is to use the combination of CSS and M-ary frequency shift keying (M-FSK) for transmission. LoRa is known to be highly robust and well-suited for low-complexity implementation but the weak aspect is in its low spectral efficiency. Orthogonal frequency division multiplexing M-FSK (ofdm-mfsk) is a technique which combine M-FSK with ofdm. For this method, the transmission bandwidth is divided to several parallel M-FSK transmission, i.e. more than one sub-carrier can be active at a time, for improving the spectral efficiency. The reception of ofdm-mfsk can be done non-coherently, therefore it holds many similar design principles as LoRa. The problematic scenarios for ofdm-mfsk are for the case with multipath-induced frequency selective channel and for the channel with presence of strong narrowband interference. We propose the combination of ofdm-mfsk and CSS in this paper. The weakness and strength of the two techniques complement each other well. The implementation of this combination is simple, since CSS can be viewed as special case of direct sequence spread spectrum and only chirp signal multiplication at the transmitter and the receiver are needed. Simulation results show that the proposed method provide improvement compared to ofdm-mfsk in both multipath-induced frequency selective channel and for the channel with presence of strong narrowband interference.

关键词： ofdm-mfsk chirp spread spectrum LPWAN IoT

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基于ofdm-mfsk的水下声通信技术研究

基于OFDM-MFSK的水下声通信技术研究

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作者：朱师琳武汉轻工大学

学位级别：硕士

水下声波通信技术作为水下唯一远程、高效的通信方式,是确保水下工作过程中信息传递的关键技术,在军事和民用领域应用广泛。正交频分复用(Orthogonal Frequency Division Multiplexing,ofdm)技术是一种多载波调制技术,具有频谱效率高、... 详细信息

水下声波通信技术作为水下唯一远程、高效的通信方式,是确保水下工作过程中信息传递的关键技术,在军事和民用领域应用广泛。正交频分复用(Orthogonal Frequency Division Multiplexing,ofdm)技术是一种多载波调制技术,具有频谱效率高、抗多径衰落等特点,是第四代移动通信的关键技术之一。因水声信道是时变、空变、频变的信道,严重的时延扩展、多普勒现象以及复杂的环境噪声给ofdm技术在水声信道中应用带来巨大挑战,研究复杂水声环境下的高速通信技术有重要意义和广阔应用前景。本文基于ofdm-mfsk通信体系,针对实际应用中的工程问题,对通信系统建模、信道估计技术以及峰均比抑制技术展开研究。论文首先研究了ofdm-mfsk水声通信系统。分析了水声信道特点并提出了简化模型;针对水声信道特点,结合多进制频移键控(Multiple Frequency Shift Keying,mfsk)调制,提出了ofdm-mfsk通信系统的模型;针对ofdm-mfsk系统频带利用率较低问题,提出了结合差分相位(Differential Phase Shift Keying,DPSK)调制的ofdm-mfsk-DPSK通信系统,仿真结果说明两系统在对应信道下性能优良。其次本文研究了水声ofdm-mfsk-DPSK系统中的信道估计技术。主要研究了基于插入导频符号进行信道估计这一非盲信道估计方法,在ofdm-mfsk-DPSK水声通信系统中,从导频形式、估计算法、插入导频间隔以及导频值四个方面通过仿真分析了信道估计性能。最后研究了ofdm-mfsk-DPSK水声通信系统中的峰均比抑制技术。研究了ofdm-mfsk-DPSK系统的峰均比与系统子载波总数、mfsk调制的进制数以及DPSK进制数的关系;基于选择性映射算法,提出了MG-SLM算法,仿真结果表明MG-SLM算法更好地降低了系统峰均比;提出了μ-MGSLM算法,该算法结合了MG-SLM算法与μ律压扩变换,能够进一步改进ofdm-mfsk-DPSK系统峰均比性能。结合信道估计从计算复杂度、峰均比抑制性能以及误码率性能三个方面对算法效果进行分析。

关键词： ofdm-mfsk 差分相位调制信道估计峰均比抑制

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基于ofdm-mfsk技术的水声语音通信系统及其实现

基于OFDM-MFSK技术的水声语音通信系统及其实现

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作者：郭晓晨江苏科技大学

学位级别：硕士

随着人类对海洋资源开发的日渐深入,人们依赖水声信道传递信息数据的需求量大大增加。由于水声信道的固有特性,使得水声语音通信技术在海洋科考、蛙人潜水以及潜艇舰船训练等军事和民用领域都得到了更加广泛的应用。因此,本文从提高系... 详细信息

随着人类对海洋资源开发的日渐深入,人们依赖水声信道传递信息数据的需求量大大增加。由于水声信道的固有特性,使得水声语音通信技术在海洋科考、蛙人潜水以及潜艇舰船训练等军事和民用领域都得到了更加广泛的应用。因此,本文从提高系统性能和降低系统复杂度出发,开展了基于ofdm-mfsk技术的水声语音通信系统的研究,通过设计基于ofdm-mfsk技术的数字通信算法从而实现水下远距离的数字语音通信,使得水下蛙人与水面甲板单元或与其他蛙人之间可以进行清晰的语音信息交流。针对高性能远距离数字语音通信MODEM的应用需求。本文对水声数字语音通信系统的硬件电路和软件算法两个方面开展了设计、实现以及验证研究。首先,依据技术指标的要求,开展了水声语音通信系统硬件相关的研究与设计,依据系统的工作指标以及相关参数对系统的硬件电路进行了设计,并选取了适合的数字处理芯片和语音压缩芯片,完成了接收、发射部分硬件电路的器件选型和电路图原理设计。其次,在软件算法方面采用ofdm-mfsk的通信技术,并添加了信道编译码、符号映射、多普勒估计与补偿等处理过程,并在此基础上开展了ofdm信号的基带和通带的通信性能仿真;由于ofdm-mfsk通信不需要进行信道估计与信道均衡,从而提高了系统通信的稳健性并降低了解调算法的复杂度;完成了系统接收部分和发射部分的程序设计,同时还确定了ofdm发射信号的帧结构,完成了语音信号收发的实现流程。然后,在以TI公司TMS320C6416T为核心的硬件平台上进行了水声语音通信算法的定点DSP实现,主要包括ofdm信号的接收和发射,以及与信号相关的调制解调、信道编译码等。在本次水声语音通信MODEM设计的最后,对系统各部分硬件电路进行关键设计参数和波形验证测试,并通过水池试验和外场试验验证了水声语音通信系统的通信性能。试验表明:本次设计实现的软件算法能够在硬件电路上稳定可靠地工作,各项软件及硬件技术指标均达到了系统的设计要求,设计的通信MODEM能够实现水下远距离的数字语音信号传输,语音信号可懂度良好,具有广阔的应用前景。

关键词：水声语音通信 ofdm-mfsk TMS320C6416T 语音压缩

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Feasibility Study of ofdm-mfsk Modulation Scheme for Smart Metering Technology

Feasibility Study of OFDM-MFSK Modulation Scheme for Smart M...

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IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe)

作者： Al-Juboori, Ghaith Doufexi, Angela Nix, Andrew R. Univ Bristol Dept Elect & Elect Engn Commun Syst & Networks Grp Bristol Avon England

ISBN: (纸本)9781538619537

The Orthogonal Frequency Division Multiplexing based M-ary Frequency Shift Keying (ofdm-mfsk) is a non-coherent modulation scheme which merges mfsk with the ofdm waveform. It is designed to improve the receiver sensitivity in the hard environments where channel estimation is very difficult to perform. In this paper, the ofdm-mfsk is suggested for the smart metering technology and its performance is measured and compared with the ordinary ofdm-BPSK. Our results show that, depending on the mfsk size value (M), the Packet Error Rate (PER) has dramatically improved for ofdm-mfsk. Additionally, the adaptive ofdm-mfsk, which selects the best M value that gives the minimum PER and higher throughput for each Smart Meter (SM), has better coverage than ofdm-BPSK. Although its throughput and capacity are lower than ofdm-BPSK, the connected SMs per sector are higher. Based on the smart metering technology requirements which imply the need for high coverage and low amount of data exchanged between the network and the SMs, The ofdm-mfsk can be efficiently used in this technology.

关键词： ofdm-mfsk Smart Meters Non-coherent detection IoT

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Symbol synchronization in the ofdm-mfsk-based multiple access system

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JOURNAL OF COMMUNICATIONS TECHNOLOGY AND ELECTRONICS 2016年第6期61卷 727-746页

作者： Potapov, V. G. Zigangirov, D. K. Zyablov, V. V. Russian Acad Sci Kharkevich Inst Informat Transmiss Problems Bolshoi Karetnyi Per 19Str 1 Moscow 127051 Russia

The dynamic range of the decentralized wideband code-division multiple access communications system based on ofdm-FSK modulation and noncoherent reception is studied depending on the clock oscillator accuracy and its jitter. The issues concerned with the symbol synchronization of the transmitter and receiver, as well as the dynamic range of the received signal, are investigated. The GOST 207 and GOST 231 unified standard radio wave propagation models, which are interpreted as communications channel models, are discussed.

关键词： synchronization ADC/DAC dynamic range channel model GLONASS/GPS ofdm-mfsk multiple access noncoherent reception

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基于ofdm-mfsk的水声通信技术研究

基于OFDM-MFSK的水声通信技术研究

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作者：王永恒哈尔滨工程大学

学位级别：博士

水声通信作为水下唯一远距离信息交互的技术途径是确保水下平台工作过程中信息传递的关键技术。水声信道是随机时-空-频变的无线信道,其严重的多途扩展、多普勒扩展以及复杂的环境噪声给高质量水声通信带来极大的困难,而水下移动平台工... 详细信息

水声通信作为水下唯一远距离信息交互的技术途径是确保水下平台工作过程中信息传递的关键技术。水声信道是随机时-空-频变的无线信道,其严重的多途扩展、多普勒扩展以及复杂的环境噪声给高质量水声通信带来极大的困难,而水下移动平台工作场景多变和随机的运动状态,则对水声通信技术提出了更大的挑战,因此研究复杂环境下稳健高速水声通信技术有着重要的现实意义和广阔的应用前景。本文采用多载波ofdm-mfsk作为通信体制,针对实际应用中面临的工程问题,对高精度信道估计技术、时频域联合处理技术、时变环境下宽带多普勒估计与补偿技术以及宽带高效低失真发射系统设计方法展开研究。ofdm-mfsk作为一种多载波技术,保留了ofdm系统中良好的抗多途、抗频率选择性衰落、高通信速率和实现简单的优点,并采用非相干的方式实现mfsk信号的检测,具有更好的抗多普勒和抗相位噪声的性能。本文从理论和仿真两方面,研究了定时同步偏差,循环前缀长度以及载波频率偏差对系统性能的影响,分析了系统的频带利用率,提出了一种ofdm-mfsk-DPSK高频带利用率的水声通信方案,并研究了概率类PAPR抑制技术在ofdm-mfsk系统中的应用性能。ofdm-mfsk调制方式灵活,可以很好地平衡通信速率和稳健性能,非常适合应用于复杂多变的水下环境。针对浅海水平信道严重的多途扩展和频率选择性衰落而导致水声通信系统受到符号间干扰(ISI)和部分子载波信噪比过低的问题,提出了一种时频域联合处理技术。该技术首先利用压缩感知(CS)技术对稀疏水声信道进行精确估计,由于OMP重构算法在使用中存在噪声环境下估计效果不佳以及求解最小二乘(LS)时矩阵求逆数值不稳定的问题,提出一种MMP-DCD算法,通过树形搜索和残差最小的原则获得最优支撑集,并采用DCD技术避免了数值不稳定的产生;然后采用信道短化技术实现信道均衡,有效压缩信道长度,抑制ISI,提高系统信噪比;最后利用频率分集技术来避免频率零点引起的子载波能量损失。论文对比分析了基于单阵元的被动时间反转镜、虚拟时间反转镜和频域MMSE信道短化技术的原理,研究了分集信号合并方法,并提出一种基于分组信噪比置信度的分集信号合并方式。仿真和湖试试验结果均证明,时频域联合处理技术可以有效抑制多途干扰,提高系统性能。水下移动平台的随机运动给ofdm-mfsk通信系统带来严重的多普勒,破坏了子载波间的正交性,造成载波间干扰。由于水声信道的超宽带特性,不同子载波的多普勒频偏是非一致的,给多普勒的估计带来困难。论文研究了采样率频偏和多普勒频展对系统性能的影响,对协方差谱矩技术和多普勒补偿技术进行了论述。针对目前常规多普勒估计与补偿算法由于时变多途环境影响导致稳定性差和精度低的问题,提出一种子载波能量的改进两阶段多普勒估计与补偿算法,先采用脉冲对实现多普勒的粗估计并完成初步补偿,并利用每个符号自身固有的子载波能量信息来高精度估计残余多普勒并完成精细补偿。本文结合ofdm-mfsk符号频谱的稀疏特性,又提出一种已知子载波频率的频域过采样逐块式多普勒估计与补偿算法,仅通过对符号的一次频域过采样处理即可完成多普勒的估计与补偿,在保证估计精度的同时降低了算法的运算量。仿真、水池和湖上试验证明了所提两种算法能够适应时变水声信道环境,具有较好的多普勒估计精度和稳定性能。针对目前水声通信系统中多谐振换能器宽带匹配效果不佳且不同方位发射波形失真度较大的问题,本文提出一种联合预均衡和实频数据技术的宽带通信发射系统设计方法。该方法在确保系统具有较高工作效率和较宽工作带宽的同时,有效改善了发射波形的失真度,提升了系统性能。论文分析了当前通信发射系统设计中面临的问题,重点研究了直接实频技术(RFDT)和简化实频数据技术(SRFT),详细给出了预均衡设计的核心思想,并对均衡器的实现方式进行了研究。仿真和水池试验结果均证明所提联合设计方法的有效性。实频数据技术作为计算机辅助技术,无需选定网络拓扑结构且避免了换能器等效模型的建立与参数分析,具有很好的应用前景。

关键词：水声通信 ofdm-mfsk 水声信道估计信道短化技术宽带多普勒估计实频数据技术

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基于过采样的ofdm-mfsk系统分集方法

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桂林电子科技大学学报 2017年第4期37卷 259-264页

作者：万杰谢跃雷郑兆飞欧阳缮桂林电子科技大学信息与通信学院广西桂林541004

为了提高ofdm-mfsk系统误比特率性能,提出一种基于过采样的ofdm-mfsk系统分集方法。该方法在发送端对ofdm子载波进行分组mfsk调制,在接收端时域进行过采样,接收端频域利用逐载波等增益合并相关子载波能量,进行非相干能量检测。仿真结果... 详细信息

为了提高ofdm-mfsk系统误比特率性能,提出一种基于过采样的ofdm-mfsk系统分集方法。该方法在发送端对ofdm子载波进行分组mfsk调制,在接收端时域进行过采样,接收端频域利用逐载波等增益合并相关子载波能量,进行非相干能量检测。仿真结果表明,该方法通过时域过采样获得了分集增益,过采样倍数越大,系统误比特率性能越好。相比于相干检测,不用信道估计,在高信噪比下,具有更好的系统性能,且对时变信道具有很强的鲁棒性。

关键词：非相干检测 ofdm-mfsk 过采样分集

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Underwater Acoustic Communication Algorithm Based on Turbo Code 3

Underwater Acoustic Communication Algorithm Based on Turbo C...

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2025 3rd International Conference on Communication Networks and Machine Learning, CNML 2025

作者： Qiao, Yang Zhang, Youwen Ocean College Jiangsu University of Science and Technology Jiangsu Zhenjiang China

ISBN: (纸本)9798400713231

Underwater acoustic communication is currently the only technological approach for long-distance information exchange underwater, and it is a key technology to ensure information transmission during the operation of underwater platforms. This article studies the underwater acoustic communication technology based on Turbo codes, aiming to solve the problem of high bit error rate caused by the complexity of underwater acoustic channels, improve the reliability and robustness of underwater communication systems, and have important theoretical significance and practical engineering value. Turbo coding has been widely used in wireless communication. Therefore, conducting research on underwater acoustic communication technology based on Turbo coding has important practical significance and broad application prospects. This paper proposes a design method for underwater acoustic communication system based on multi carrier ofdm-mfsk communication system and Turbo coding as source coding to address the high bit error rate problem in underwater acoustic communication. The simulation and experimental results show that this method significantly reduces the system error rate, and experiments were conducted on the canal, obtaining results with an error rate of less than. © 2025 Copyright held by the owner/author(s).

关键词： ofdm-mfsk Turbo code Underwater acoustic communication

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