CN113285763A - Diversity receiving method in blue-green LED communication - Google Patents

Diversity receiving method in blue-green LED communication Download PDF

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CN113285763A
CN113285763A CN202110407332.1A CN202110407332A CN113285763A CN 113285763 A CN113285763 A CN 113285763A CN 202110407332 A CN202110407332 A CN 202110407332A CN 113285763 A CN113285763 A CN 113285763A
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diversity
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柯熙政
费少龙
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Xian University of Technology
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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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/69—Electrical arrangements in the receiver
    • 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
    • H04B10/80—Optical aspects relating to the use of optical transmission for specific applications, not provided for in groups H04B10/03 - H04B10/70, e.g. optical power feeding or optical transmission through water
    • 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

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

The invention discloses a diversity receiving method in blue-green LED communication, which is implemented according to the following steps: step 1, carrying out space diversity on the transmitted signals, and dividing the transmitted signals into k channels for transmission; step 2, diversity reception is carried out on the signals at the receiving end, and k paths of optical antennas are erected for reception; step 3, determining a channel weighting coefficient by using a maximum ratio combining mode, and superposing the signals; and 4, building a merging circuit, merging and outputting the multi-channel signals, and finally reaching a receiver. The invention solves the problems of instability of underwater LED communication channel parameters and serious multipath fading in the prior art.

Description

Diversity receiving method in blue-green LED communication
Technical Field
The invention belongs to the technical field of wireless laser communication, and particularly relates to a diversity receiving method in blue-green LED communication.
Background
Visible light communication is a wireless communication technology that has recently emerged and is receiving increasing attention from global scientists and marine engineers. The discovery of visible light communications has greatly expanded the increasingly tense wireless communications spectrum. The visible light communication technology utilizes the characteristic that the LED lamp can be modulated at high speed for carrying out high-speed communication between equipment terminals.
In optical Communication, the wavelength of blue-green light is located in the transmission window of water, and the absorption coefficient of water to blue-green light is small, so that the blue-green light Communication can be transmitted at a relatively long distance underwater, and a high transmission rate can be obtained. The laser communication power is high, the laser can be transmitted in a long distance underwater, but the problem of coherent flicker exists, accurate alignment is needed for realizing communication, and difficulty is caused to actual operation and application. The underwater visible light communication based on the blue-green light LED uses incoherent light, integrates the functions of illumination and communication, does not need strict alignment, and provides a scheme for realizing dynamic communication. Multipath fading is severe due to instability of channel parameters. Therefore, how to improve the performance of the LED communication system will be one of the cores of research on future high-speed underwater communication networks.
Disclosure of Invention
The invention aims to provide a diversity receiving method in blue-green LED communication, which solves the problems of instability of underwater LED communication channel parameters and serious multipath fading in the prior art.
The technical scheme adopted by the invention is that the diversity receiving method in blue-green LED communication is implemented according to the following steps:
step 1, carrying out space diversity on the transmitted signals, and dividing the transmitted signals into k channels for transmission;
step 2, diversity reception is carried out on the signals at the receiving end, and k paths of optical antennas are erected for reception;
step 3, determining a channel weighting coefficient by using a maximum ratio combining mode, and superposing the signals;
and 4, building a merging circuit, merging and outputting the multi-channel signals, and finally reaching a receiver.
The present invention is also characterized in that,
in the step 1, the optical signals with the same information are transmitted through different optical antennas and reach a receiving end through underwater channels in different ways, which is specifically as follows:
suppose that k channels transmit signals and each channel has the same underwater turbulence distribution characteristics, namely the kinetic energy dissipation ratio is 0.01 and the mean square temperature dissipation ratio is 10-10Temperature salinity contribution ratio of-4, andeach channel is independently uncorrelated. The signal source converts the electrical signals into optical signals through the transmitter and sends the optical signals to the antennas, the antennas are arranged at different vertical height positions in space, the optical signals with the same information are transmitted out through the plurality of optical antennas, and the optical signals are transmitted to the receiving end through the k underwater channels to be received.
The step 2 is as follows:
arranging a plurality of optical receiving antennas at different vertical heights of a receiving end space, wherein the distance between the receiving antennas is more than 0.6 times of the wavelength of light, receiving and coupling each light signal independently transmitted through an underwater channel into a corresponding optical fiber by the respective optical antenna, connecting an avalanche photodetector APD behind the optical fiber, converting the light signal into an electric signal, and then uniformly processing the electric signal, wherein k signal input voltages received by the avalanche photodetector APD at t moment are respectively represented as r1(t)、r2(t)、......、rk(t)，akThe gain coefficient of the kth signal is, the output voltage signals of the detector are respectively: a is1r1(t)、a2r2(t)、......、akrk(t)。
The step 3 is as follows:
using a maximum ratio mode for combination, wherein the noise of each channel is additive noise and is uncorrelated with the signal, and r is used for outputting the voltage signal in the step 2k(t)＝xk(t)+nk(t) represents, xk(t) represents the original signal, nk(t) represents noise, and a weighting factor a for each channelkAnd signal rk(t) is proportional to the noise power nK(t) is inversely proportional, i.e.
Figure BDA0003022805650000031
Therefore, the voltage signals output by the APDs of each avalanche photodetector are calculated by combining in a maximum ratio mode
Figure BDA0003022805650000032
The step 4 is as follows:
diversity receiving circuit built based on summing adderThe adder adopts an integrated operational amplifier summing operation circuit, the positive input end of the inverting operational amplifier is connected with a resistor R to be grounded, and the negative input end of the inverting operational amplifier is connected with a resistor R in parallel1,R2,...,RkA resistor R is connected between the output end and the negative input end of the operational amplifierfThe summing circuit adopts LM series high-speed inverting operational amplifier, RfFor the feedback resistance, R is the balance resistance, and the input resistance is R1,R2,...,RkOutputting a voltage signal U by each avalanche photodetector APD in the step 31,U2,...UkAs an input voltage, the output voltage after passing through the arithmetic circuit is:
Figure BDA0003022805650000033
then U is0Is the final output voltage signal value.
The method has the advantages that the diversity reception technology is applied to the underwater LED optical communication system, the diversity model of the underwater LED communication system is constructed, and the diversity reception method is realized according to the actual optical path of the underwater communication environment. In the wireless diversity communication system, the same information is respectively transmitted to a receiving end on different channels for combination, thereby providing diversity gain for the system and improving the system performance.
Drawings
Fig. 1 is a diagram of a spatial diversity system;
FIG. 2 is a linear summation schematic;
FIG. 3 is a maximum ratio combining block diagram;
fig. 4 is a schematic diagram of a combining circuit.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention discloses a diversity receiving method in blue-green LED communication, which is implemented according to the following steps:
step 1, carrying out space diversity on the transmitted signals, and dividing the transmitted signals into k channels for transmission;
in the step 1, the optical signals with the same information are transmitted through different optical antennas and reach a receiving end through underwater channels in different ways, which is specifically as follows:
suppose that k channels transmit signals and each channel has the same underwater turbulence distribution characteristics, namely the kinetic energy dissipation ratio is 0.01 and the mean square temperature dissipation ratio is 10-10The temperature and salinity contribution ratio is-4, and each channel is independent and irrelevant, the signal source converts the electric signal into an optical signal through the transmitter and sends the optical signal into the antenna, each antenna is arranged at a different vertical height position in space, the optical signal with the same information is transmitted out by a plurality of optical antennas, and the optical signal is transmitted to the receiving end through the k underwater channels to be received.
Step 2, diversity reception is carried out on the signals at the receiving end, and k paths of optical antennas are erected for reception;
the step 2 is as follows:
as shown in fig. 2, a plurality of optical receiving antennas are disposed at different vertical heights of a receiving end space, the distance between the receiving antennas is greater than 0.6 times of the wavelength of light, each optical signal independently transmitted through an underwater channel is received and coupled into a corresponding optical fiber by the respective optical antenna, an avalanche photodetector APD is connected behind the optical fiber to convert the optical signal into an electrical signal, and then the electrical signal is uniformly processed, assuming that k signal input voltages received by the avalanche photodetector APD at time t are respectively represented as r1(t)、r2(t)、......、rk(t)，akThe gain coefficient of the kth signal is, the output voltage signals of the detector are respectively: a is1r1(t)、a2r2(t)、......、akrk(t)。
Step 3, determining a channel weighting coefficient by using a maximum ratio combining mode, and superposing the signals;
the step 3 is as follows:
as shown in fig. 3, the maximum ratio combining is used, and the noise of each channel is additive noise and uncorrelated with the signal, then the output voltage signal in step 2 is rk(t)＝xk(t)+nk(t) represents, xk(t) represents the original signal, nk(t) represents noise, and a weighting factor a for each channelkAnd signal rk(t) is proportional to the noise power nK(t) is inversely proportional, i.e.
Figure BDA0003022805650000051
Therefore, the voltage signals output by the APDs of each avalanche photodetector are calculated by combining in a maximum ratio mode
Figure BDA0003022805650000052
And 4, building a merging circuit, merging and outputting the multi-channel signals, and finally reaching a receiver.
The step 4 is as follows:
a diversity receiving circuit is built based on a summing adder, as shown in figure 4, the summing adder adopts an integrated operational amplifier summing operational circuit, namely an inverting operational amplifier, the positive input end of the inverting operational amplifier is connected with a resistor R to be grounded, and the negative input end of the inverting operational amplifier is connected with a resistor R in parallel1,R2,...,RkA resistor R is connected between the output end and the negative input end of the operational amplifierfThe summing circuit adopts LM series high-speed inverting operational amplifier, RfFor the feedback resistance, R is the balance resistance, and the input resistance is R1,R2,...,RkOutputting a voltage signal U by each avalanche photodetector APD in the step 31,U2,...UkAs an input voltage, the output voltage after passing through the arithmetic circuit is:
Figure BDA0003022805650000053
then U is0Is the final output voltage signal value.
The invention applies the diversity reception technology to an underwater LED optical communication system, constructs a diversity model of the underwater LED communication system, and realizes a diversity reception method according to the actual light path of the underwater communication environment. In the wireless diversity communication system, the same information is respectively transmitted to a receiving end on different channels for combination, thereby providing diversity gain for the system and improving the system performance.

Claims (5)

1. A diversity receiving method in blue-green LED communication is characterized by comprising the following steps:
step 1, carrying out space diversity on the transmitted signals, and dividing the transmitted signals into k channels for transmission;
step 2, diversity reception is carried out on the signals at the receiving end, and k paths of optical antennas are erected for reception;
step 3, determining a channel weighting coefficient by using a maximum ratio combining mode, and superposing the signals;
and 4, building a merging circuit, merging and outputting the multi-channel signals, and finally reaching a receiver.
2. The method according to claim 1, wherein in step 1, the optical signals with the same information are transmitted through different optical antennas, pass through an underwater channel, and reach a receiving end in different ways, specifically as follows:
suppose that k channels transmit signals and each channel has the same underwater turbulence distribution characteristics, namely the kinetic energy dissipation ratio is 0.01 and the mean square temperature dissipation ratio is 10-10The temperature and salinity contribution ratio is-4, and each channel is independent and irrelevant, the signal source converts the electric signal into an optical signal through the transmitter and sends the optical signal into the antenna, each antenna is arranged at a different vertical height position in space, the optical signal with the same information is transmitted out by a plurality of optical antennas, and the optical signal is transmitted to the receiving end through the k underwater channels to be received.
3. The method of claim 2, wherein the step 2 is as follows:
multiple optical receiving antennas are arranged at different vertical heights of receiving end space, the distance between the receiving antennas is larger than 0.6 times of optical wavelength, and each optical signal independently transmitted through underwater channels is formed by each optical receiving antennaReceiving and coupling the optical antenna into a corresponding optical fiber, connecting the optical fiber to an Avalanche Photodetector (APD), converting optical signals into electric signals, and then uniformly processing the electric signals, wherein k signal input voltages received by the Avalanche Photodetector (APD) at t moment are respectively represented as r1(t)、r2(t)、......、rk(t)，akThe gain coefficient of the kth signal is, the output voltage signals of the detector are respectively: a is1r1(t)、a2r2(t)、......、akrk(t)。
4. The method of claim 3, wherein the step 3 is as follows:
using a maximum ratio mode for combination, wherein the noise of each channel is additive noise and is uncorrelated with the signal, and r is used for outputting the voltage signal in the step 2k(t)＝xk(t)+nk(t) represents, xk(t) represents the original signal, nk(t) represents noise, and a weighting factor a for each channelkAnd signal rk(t) is proportional to the noise power nK(t) is inversely proportional, i.e.
Figure FDA0003022805640000021
Therefore, the voltage signals output by the APDs of each avalanche photodetector are calculated by combining in a maximum ratio mode
Figure FDA0003022805640000022
5. The method of claim 4, wherein the step 4 is as follows:
a diversity receiving circuit is built based on a summing adder, the adder adopts an integrated operational amplifier summing operation circuit, the positive input end of an inverting operational amplifier is connected with a resistor R to be grounded, and the negative input end of the inverting operational amplifier is connected with the resistor R in parallel1,R2,...,RkOutput terminal and negative input terminal of operational amplifierIs connected with a resistor RfThe summing circuit adopts LM series high-speed inverting operational amplifier, RfFor the feedback resistance, R is the balance resistance, and the input resistance is R1,R2,...,RkOutputting a voltage signal U by each avalanche photodetector APD in the step 31,U2,...UkAs an input voltage, the output voltage after passing through the arithmetic circuit is:
Figure FDA0003022805640000023
then U is0Is the final output voltage signal value.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114465665A (en) * 2022-01-24 2022-05-10 桂林电子科技大学 Light beam forming method based on maximum ratio combination under strong turbulence channel

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CN103475402A (en) * 2013-07-29 2013-12-25 北京邮电大学 Visible-light diversity-reception method and system
CN103812559A (en) * 2013-10-22 2014-05-21 深圳光启创新技术有限公司 Visible light diversity transmitting and receiving device and visible light communication system
CN104601234A (en) * 2014-12-04 2015-05-06 复旦大学 High-speed weak signal obtaining circuit
CN105553570A (en) * 2016-01-25 2016-05-04 中国人民解放军信息工程大学 Transmission system based on underwater visible light communication
CN108683456A (en) * 2018-05-03 2018-10-19 内蒙古科技大学 Intelligent transportation system based on MIMO and visible light communication and communication means
CN111431624A (en) * 2020-06-09 2020-07-17 北京赛博融合信息技术有限公司 Underwater wireless optical communication system

Patent Citations (6)

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Publication number Priority date Publication date Assignee Title
CN103475402A (en) * 2013-07-29 2013-12-25 北京邮电大学 Visible-light diversity-reception method and system
CN103812559A (en) * 2013-10-22 2014-05-21 深圳光启创新技术有限公司 Visible light diversity transmitting and receiving device and visible light communication system
CN104601234A (en) * 2014-12-04 2015-05-06 复旦大学 High-speed weak signal obtaining circuit
CN105553570A (en) * 2016-01-25 2016-05-04 中国人民解放军信息工程大学 Transmission system based on underwater visible light communication
CN108683456A (en) * 2018-05-03 2018-10-19 内蒙古科技大学 Intelligent transportation system based on MIMO and visible light communication and communication means
CN111431624A (en) * 2020-06-09 2020-07-17 北京赛博融合信息技术有限公司 Underwater wireless optical communication system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114465665A (en) * 2022-01-24 2022-05-10 桂林电子科技大学 Light beam forming method based on maximum ratio combination under strong turbulence channel
CN114465665B (en) * 2022-01-24 2024-04-02 桂林电子科技大学 Beam forming method based on maximum ratio combination under strong turbulence channel

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