WO2015149553A1 - Procédé de transmission optique sans fil à faible rapport crête sur moyenne fondé sur un réglage scalaire dynamique - Google Patents

Procédé de transmission optique sans fil à faible rapport crête sur moyenne fondé sur un réglage scalaire dynamique Download PDF

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Publication number
WO2015149553A1
WO2015149553A1 PCT/CN2014/095249 CN2014095249W WO2015149553A1 WO 2015149553 A1 WO2015149553 A1 WO 2015149553A1 CN 2014095249 W CN2014095249 W CN 2014095249W WO 2015149553 A1 WO2015149553 A1 WO 2015149553A1
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signal
ofdm
symbol
time domain
received
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Chinese (zh)
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张华�
袁颖
许威
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Southeast University
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Southeast University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H04L27/2623—Reduction thereof by clipping
    • H04L27/2624—Reduction thereof by clipping by soft clipping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only

Definitions

  • the invention relates to a low peak-to-average ratio wireless optical transmission method based on dynamic scalar adjustment, belonging to a wireless optical communication technology.
  • wireless optical communication Due to its rich spectrum resources, good communication security, large transmission power, and low electromagnetic radiation, wireless optical communication has become a hot research topic in the field of communication in recent years.
  • ISI inter-symbol interference
  • OFDM modulation in wireless optical communication
  • Fight multipath effects In order to realize high-speed data transmission of wireless optical communication, reduce inter-symbol interference (ISI), introduce OFDM modulation in wireless optical communication, and provide high-speed data transmission by transmitting modulated symbols in parallel on orthogonal subcarriers. Fight multipath effects.
  • Intensity modulation/direct detection is often used in wireless optical communication, so the time domain transmission signal after OFDM modulation needs to be a positive signal that is guaranteed to be a real value.
  • OFDM DC biased optical OFDM
  • ACO-OFDM asymmetric peaked optical OFDM
  • ACO-OFDM only transmits modulation symbols on odd subcarriers, and even subcarriers do not transmit symbols, discarding the negative part of the time domain signal obtained by IFFT, leaving only the positive part. This can ensure that the transmitted time domain signal is a positive real signal, and can reduce the transmission power and save resources, but the frequency utilization is low, and N subcarriers can only transmit N/4 symbols.
  • DCO-OFDM adds a DC offset to the OFDM-modulated signal, making the signal positive. This method is simple to implement and has high frequency utilization, but increases DC power consumption.
  • the OFDM system in wireless optical communication Similar to the OFDM system in radio frequency communication, the OFDM system in wireless optical communication also has a problem that the signal peak-to-average power ratio is too high.
  • the high PAPR puts high demands on the linearity of the power amplifier at the transmitter end.
  • the PAPR is too high, in addition to the power amplifier, it also puts higher requirements on the linearity of the LED lamp, due to the power amplifier and the LED lamp.
  • Nonlinear characteristics can cause nonlinear distortion, which can seriously degrade the overall performance of the system.
  • high PAPR can also result in an increase in the required DC offset, thereby increasing system power consumption.
  • a variety of methods for reducing PAPR in OFDM systems have been proposed in radio frequency communication, such as limiting, dynamic constellation extension (ACE), coding, partial transmission sequence (PTS), selective mapping (SLM), reserved subcarriers ( TR) and so on.
  • ACE dynamic constellation extension
  • PTS partial transmission sequence
  • SLM selective mapping
  • TR reserved subcarriers
  • the present invention provides a low-peak-to-average ratio wireless optical transmission method based on dynamic scalar adjustment, which is a very simple method for reducing PAPR of wireless optical communication, according to each method.
  • the time domain peak of one OFDM symbol is used to select different scalar adjustment coefficients, so that the symbols with particularly large peaks are compressed to a certain extent, thereby reducing the PAPR of the entire frame signal, thereby improving the transmission performance; only receiving and receiving by measurement at the receiving end
  • the average power of the symbol is used to estimate the scalar coefficient multiplied at the transmitting end, which is simple to implement.
  • the improvement of PAPR reduces the linearity requirements of the system for the power amplifier and the LED lamp, and reduces the nonlinear distortion of the signal in the electric and optical domains.
  • the system receives performance; the PAPR drop also reduces the DC offset required at the transmitter, reducing system power consumption.
  • the system At the transmitting end, first, the system generates a frequency domain symbol through which the bit information stream is modulated by constellation point mapping modulation; secondly, the frequency domain signal is conjugate symmetrically mapped on the system subcarrier and passed an inverse fast Fourier transform (IFFT) Generating a real-valued baseband time-domain orthogonal frequency division multiplexing (OFDM) transmission signal; then, multiplying each symbol by a corresponding scalar adjustment coefficient according to the time domain peak of each OFDM symbol; finally, the time domain transmission signal is added
  • IFFT inverse fast Fourier transform
  • OFDM orthogonal frequency division multiplexing
  • the photodiode converts the received optical signal into an electrical signal
  • the receiver estimates the scalar adjustment coefficient at which the signal is multiplied at the transmitting end according to the received average power of each OFDM symbol; then, it will receive
  • the time domain OFDM symbol is divided by the estimated adjustment coefficient and then subjected to Fast Fourier Transform (FFT) conversion to the frequency domain symbol, and the conjugate symmetric portion is removed; finally, the received symbol is obtained by demodulation.
  • FFT Fast Fourier Transform
  • the invention is simple to implement, can effectively reduce the peak-to-average power ratio of the wireless optical communication OFDM system, reduce the system power consumption, and reduces the nonlinearity of the signal in the electric and optical domains by reducing the linearity requirements of the power amplifier and the LED lamp. Distortion, which improves system reception performance.
  • the above method specifically includes the following steps:
  • the transmitting end :
  • the number of subcarriers in the OFDM system of the wireless optical communication is set to N, and the signal transmitted in each frame has M OFDM symbols; the binary data source generated by the source is subjected to multi-ary quadrature amplitude modulation (M-QAM) ), forming a frequency domain signal to be transmitted
  • M-QAM multi-ary quadrature amplitude modulation
  • the subcarrier mapping in OFDM is performed according to the following formula, which satisfies the conjugate symmetry: (in the case of no confusion, the superscript (m) is omitted for simplicity of explanation)
  • the frequency domain signal is converted to a real value time domain OFDM signal after N point IFFT as follows:
  • the photodiode converts the optical signal into a time domain electrical signal by calculating each received OFDM symbol Average power using the maximum a posteriori (MAP) criterion to estimate the modulation factor of the symbol Detecting received signals based on estimated adjustment factors which is among them Time domain OFDM transmission symbols estimated for the receiving end;
  • MAP maximum a posteriori
  • the low peak-to-average ratio wireless optical transmission method based on dynamic scalar adjustment provided by the invention has the following advantages: 1. No additional sideband information needs to be transmitted, and the peak-to-average power ratio of the system can be effectively reduced without wasting frequency resources. 2, whether it is the implementation of the transmitter or receiver is very simple; 3, low PAPR can reduce the system's linearity requirements for power amplifiers and LED lights, reduce the implementation of the transmitter, and reduce the nonlinear characteristics of the power amplifier and LED lights The resulting nonlinear distortion improves the reception performance of the system. 4. The low PAPR also reduces the size of the DC component that must be added to the transmission, reducing the system power consumption.
  • FIG. 1 is a system block diagram of a low peak-to-average ratio wireless optical transmission method based on dynamic scalar adjustment according to the present invention
  • 2 is a schematic diagram of time-domain OFDM symbols for wireless optical communication without adjustment of scalar coefficients and adjustment;
  • 3 is a PAPR complementary cumulative probability distribution graph of the present invention and a generally unconditioned optical communication OFDM.
  • a low-peak-to-average ratio wireless optical transmission method based on dynamic scalar adjustment is performed as follows: At the transmitting end, first, the system generates a bit information stream and modulates it into a frequency domain symbol to be transmitted through constellation point mapping. Secondly, the frequency domain signal is symmetrically mapped symmetrically on the system subcarrier, and the real value baseband time domain transmission signal is generated by the inverse fast Fourier transform; then, according to the time domain peak of each OFDM symbol, for each The symbol is multiplied by the corresponding scalar adjustment factor; finally, the time domain transmit signal plus the DC bias drives the LED to transmit.
  • the photodiode converts the received optical signal into an electrical signal, and based on the received average power of each OFDM symbol, the scalar adjustment coefficient multiplied at the transmitting end; and then, the received time domain
  • the OFDM symbol is divided by the estimated adjustment coefficient and then converted into a frequency domain symbol by a fast Fourier transform, and the conjugate symmetric portion is removed.
  • the received symbol is obtained by demodulation.
  • the transmitting end :
  • the number of subcarriers in the OFDM system of the wireless optical communication is set to N, and the signal transmitted in each frame has M OFDM symbols; the binary data source generated by the source is subjected to multi-ary quadrature amplitude modulation (M-QAM) ), forming a frequency domain signal to be transmitted
  • M-QAM multi-ary quadrature amplitude modulation
  • the subcarrier mapping in OFDM is performed according to the following formula, which satisfies the conjugate symmetry: (in the case of no confusion, the superscript (m) is omitted for simplicity of explanation)
  • the frequency domain signal is converted to a real value time domain OFDM signal after N point IFFT as follows:
  • the photodiode converts the optical signal into a time domain electrical signal by calculating each received OFDM symbol Average power using the maximum a posteriori (MAP) criterion to estimate the modulation factor of the symbol Detecting received signals based on estimated adjustment factors which is among them Time domain OFDM transmission symbols estimated for the receiving end;
  • MAP maximum a posteriori
  • each symbol is multiplied by a corresponding scalar adjustment coefficient according to the time domain peak of each OFDM, and the entire OFDM symbol is compressed by multiplying the excessively large symbol by the adjustment coefficient ⁇ ( ⁇ 1). Thereby reducing the PAPR of the entire frame signal.
  • Figure 3 shows the optical communication OFDM system without coefficient adjustment and the PAPR complementary cumulative distribution curve of the system after using the method.
  • the system adopts 16-QAM modulation.
  • the adjustment coefficient is adopted.
  • the adjustment coefficient is According to the frame statistics system PAPR, namely:
  • the method can effectively reduce the PAPR of the system, thereby reducing the linearity requirement of the device at the transmitting end, reducing the nonlinear distortion of the signal in the electric and optical domains, and improving the overall receiving performance of the system.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optical Communication System (AREA)

Abstract

La présente invention concerne un procédé de transmission optique sans fil à faible rapport crête sur moyenne fondé sur un réglage scalaire dynamique. Différents coefficients de réglage scalaire sont sélectionnés en fonction de la valeur de crête dans le domaine temporel de chaque symbole OFDM, et les symboles ayant une valeur de crête très élevée sont compressés dans une certaine mesure, de manière à réduire le rapport puissance crête sur puissance moyenne (PAPR) des signaux d'une trame entière et à améliorer les performances de transmission. Le procédé est facile à mettre en œuvre du fait que l'extrémité réceptrice a seulement besoin d'estimer le coefficient scalaire multiplié au niveau de l'extrémité émettrice par mesure de puissance moyenne des symboles reçus. L'amélioration du PAPR réduit les exigences du système en termes d'amplification et de linéarité de lumière DEL, réduit la distorsion non linéaire des signaux dans le domaine électrique et le domaine optique, et améliore l'efficacité de réception du système. La diminution du PAPR réduit également la polarisation en courant continu nécessaire au niveau de l'extrémité émettrice, et réduit le gaspillage de puissance du système.
PCT/CN2014/095249 2014-04-02 2014-12-29 Procédé de transmission optique sans fil à faible rapport crête sur moyenne fondé sur un réglage scalaire dynamique Ceased WO2015149553A1 (fr)

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Cited By (8)

* Cited by examiner, † Cited by third party
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CN108896961A (zh) * 2018-06-29 2018-11-27 天津大学 一种基于信号功率估计的提高可见光定位精度的方法
CN109547381A (zh) * 2019-01-17 2019-03-29 山东建筑大学 一种基于自编码器的dco-ofdm系统papr抑制方法及系统
CN114465665A (zh) * 2022-01-24 2022-05-10 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法
CN114513256A (zh) * 2022-02-02 2022-05-17 复旦大学 一种基于aco-fbmc调制的光子计数通信方法
CN114650083A (zh) * 2022-03-25 2022-06-21 深圳市力合微电子股份有限公司 一种hplc双模高速无线系统的峰均比优化方法
CN114679361A (zh) * 2022-03-09 2022-06-28 恒玄科技(上海)股份有限公司 一种ofdm调制方法及通信装置
CN115941414A (zh) * 2022-10-26 2023-04-07 珠海中慧微电子有限公司 一种ofdm信号的降峰均比值方法、装置及存储介质
CN120301513A (zh) * 2025-06-12 2025-07-11 甘肃省公安厅 一种基于动态调制的可见光通信数据传输方法

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CN103916356B (zh) * 2014-04-02 2017-02-15 东南大学 一种基于动态标量调节的低峰均比无线光传输方法
CN104184693B (zh) * 2014-09-09 2017-07-07 东南大学 一种适用于可见光通信的dco‑ofdm系统直流偏置设置方法
CN104796195B (zh) * 2015-03-25 2017-05-10 东南大学 一种采用乘性削波的可见光多载波传输方法
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CN107370707B (zh) * 2016-05-13 2020-06-16 华为技术有限公司 一种信号处理方法及装置
CN105915291B (zh) * 2016-05-27 2018-04-17 哈尔滨工程大学 非对称限幅直流偏置光ofdm系统峰均比抑制方法
CN108206800B (zh) * 2016-12-19 2020-11-03 上海诺基亚贝尔股份有限公司 一种光正交频分复用系统中降低峰均功率比的方法及装置
EP3591861A1 (fr) * 2018-07-06 2020-01-08 Signify Holding B.V. Système et procédé de transmission optique de données
CN109787685B (zh) * 2019-03-21 2022-02-15 东南大学 基于子载波预留的可见光ofdm系统自适应低峰比方法
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1588938A (zh) * 2004-09-16 2005-03-02 西安电子科技大学 Ofdm通信系统及降低峰均功率比的方法
CN102859957A (zh) * 2010-03-19 2013-01-02 奥菲迪乌姆有限公司 用于光纤非线性减轻的方法和装置
CN103618687A (zh) * 2013-12-03 2014-03-05 东南大学 一种拥有低峰均功率比的无线光正交多载波通信方法
CN103916356A (zh) * 2014-04-02 2014-07-09 东南大学 一种基于动态标量调节的低峰均比无线光传输方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101888361A (zh) * 2009-05-13 2010-11-17 中兴通讯股份有限公司 峰均比处理方法和装置
JP5712957B2 (ja) * 2012-03-23 2015-05-07 アイコム株式会社 通信機および通信方法
CN102624669B (zh) * 2012-04-23 2014-04-16 西安电子科技大学 基于混合分布优化的ofdm信号峰平比抑制方法
CN103532900A (zh) * 2013-09-27 2014-01-22 中国人民解放军信息工程大学 降低可见光Flip-OFDM通信系统LED非线性失真的动态补偿方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1588938A (zh) * 2004-09-16 2005-03-02 西安电子科技大学 Ofdm通信系统及降低峰均功率比的方法
CN102859957A (zh) * 2010-03-19 2013-01-02 奥菲迪乌姆有限公司 用于光纤非线性减轻的方法和装置
CN103618687A (zh) * 2013-12-03 2014-03-05 东南大学 一种拥有低峰均功率比的无线光正交多载波通信方法
CN103916356A (zh) * 2014-04-02 2014-07-09 东南大学 一种基于动态标量调节的低峰均比无线光传输方法

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CN108896961A (zh) * 2018-06-29 2018-11-27 天津大学 一种基于信号功率估计的提高可见光定位精度的方法
CN108896961B (zh) * 2018-06-29 2022-03-01 天津大学 一种基于信号功率估计的提高可见光定位精度的方法
CN109547381A (zh) * 2019-01-17 2019-03-29 山东建筑大学 一种基于自编码器的dco-ofdm系统papr抑制方法及系统
CN109547381B (zh) * 2019-01-17 2021-06-01 山东建筑大学 一种基于自编码器的dco-ofdm系统papr抑制方法及系统
CN114465665A (zh) * 2022-01-24 2022-05-10 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法
CN114465665B (zh) * 2022-01-24 2024-04-02 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法
CN114513256B (zh) * 2022-02-02 2023-06-27 复旦大学 一种基于aco-fbmc调制的光子计数通信方法
CN114513256A (zh) * 2022-02-02 2022-05-17 复旦大学 一种基于aco-fbmc调制的光子计数通信方法
CN114679361A (zh) * 2022-03-09 2022-06-28 恒玄科技(上海)股份有限公司 一种ofdm调制方法及通信装置
CN114679361B (zh) * 2022-03-09 2023-11-21 恒玄科技(上海)股份有限公司 一种ofdm调制方法及通信装置
CN114650083A (zh) * 2022-03-25 2022-06-21 深圳市力合微电子股份有限公司 一种hplc双模高速无线系统的峰均比优化方法
CN114650083B (zh) * 2022-03-25 2023-11-07 深圳市力合微电子股份有限公司 一种hplc双模高速无线系统的峰均比优化方法
CN115941414A (zh) * 2022-10-26 2023-04-07 珠海中慧微电子有限公司 一种ofdm信号的降峰均比值方法、装置及存储介质
CN120301513A (zh) * 2025-06-12 2025-07-11 甘肃省公安厅 一种基于动态调制的可见光通信数据传输方法

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