Method and system for realizing all-optical double-hop transmission in Li-Fi network based on visible light

Abstract

The present invention belongs to the technical field of indoor visible light communication, and discloses a method and system for realizing all-optical dual-hop transmission in a Li-Fi network based on visible light. The method comprises: obtaining base station data, and transmitting signals on a backhaul link based on odd subcarrier mapping and a visible light line-of-sight link; relaying and caching the signals on the backhaul link based on an AP access point; obtaining the relay-cached signals, and transmitting downlink signals based on even subcarrier mapping and a visible light line-of-sight link; decoding and transmitting the signals on the downlink, and outputting the decoded signals to a user terminal, thereby completing the dual-hop transmission of the entire signal. In summary, the present invention has the effect of increasing the transmission capacity of the backhaul link and improving the user's service experience. The system comprises: a backhaul link structure and a downlink structure composed of a combination of an existing wired link and a visible light line-of-sight link, which can effectively reduce system costs.

Description

Technical Field

[0001] The present invention belongs to the field of indoor visible light communication technology, and specifically relates to a method and system for realizing all-optical double-hop transmission in a Li-Fi network based on visible light. Background Art

[0002] Visible light communication (VLC) uses light in the 400-700nm visible light band as an information carrier, transmitting optical signals directly through the air without the need for wired channels such as optical fiber. Compared to infrared, Bluetooth, Wi-Fi, and other radio frequency communication technologies, VLC offers advantages such as eye safety, abundant spectrum resources and the absence of radio spectrum licenses, high transmission power, low susceptibility to electromagnetic interference, and environmental friendliness. Therefore, it holds broad application prospects in the Internet of Things, smart cities (and homes), aviation, maritime transport, subways, high-speed rail, indoor navigation, and underground operations.

[0003] VLC-based Li-Fi wireless networks can serve as a zero-interference supplement to existing wireless access technologies (such as Wi-Fi and cellular wireless communication technologies), providing a high-speed and flexible access method for indoor short-range wireless communication networks.

[0004] In Li-Fi wireless network applications, transmission from the base station to the backbone network is called backhaul, while transmission from the base station or backbone network to the user terminal is called downlink. Numerous studies have shown that downlink capacity is significantly affected by backhaul capacity, which can easily cause interference between link information and impact the user experience. Furthermore, existing backhaul implementation methods in Li-Fi wireless networks rely on wired networks, such as power lines, single-mode fiber cables, and Fast Ethernet, which significantly limit their transmission capacity.

[0005] In the backhaul link based on single-mode fiber optic cable, the complexity of cable wiring will inevitably increase the implementation cost of Li-Fi wireless optical network. Summary of the Invention

[0006] In view of this, the present invention provides a method for realizing all-optical double-hop transmission in a Li-Fi network based on visible light, and a system for realizing the method.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A system for realizing all-optical dual-hop transmission in a Li-Fi network based on visible light is characterized by: a backhaul link structure formed by a base station, an access point (AP), a photodetector, and an LED combination; and a downlink link structure formed by a base station, an access point (AP), a photodetector, and a user terminal combination.

[0009] A method for implementing all-optical double-hop transmission in a Li-Fi network based on visible light includes the following steps:

[0010] Acquire base station data and transmit signals on the backhaul link based on odd subcarrier mapping and a visible light line-of-sight link; relay cache the signals on the backhaul link based on an AP access point; acquire the relay cached signals and transmit downlink signals based on even subcarrier mapping and a visible light line-of-sight link; decode and transmit the downlink signals, and output the decoded signals to the user terminal, completing the double-hop transmission of the entire signal.

[0011] Preferably, the transmission of the signal on the backhaul link includes the following steps:

[0012] The data buffered by the base station is decoded by a decoder to generate a binary bit stream; the binary bit stream is modulated by QAM to obtain a complex signal vector X D , and perform serial / parallel conversion on the complex signal vector; D Odd subcarrier mapping and conjugate symmetric mapping are performed to obtain a complex conjugate symmetric vector X; OFDM modulation is performed on the complex conjugate symmetric vector X based on IFFT transformation to obtain a time domain signal vector; parallel / serial conversion is performed on the time domain signal vector, and a DC bias is added to drive the LED to emit light to form a visible light line-of-sight link for optical signal transmission.

[0013] Preferably, the relay cache includes the following steps:

[0014] The optical signal transmitted on the backhaul link is acquired based on a photoelectric sensor, and optical / electrical conversion is completed, and then the resulting electrical signal is converted into serial / parallel. The converted electrical signal is demodulated using OFDM based on IFFT transformation to obtain a complex conjugate symmetric vector X. The complex conjugate symmetric vector X is demodulated using QAM to obtain a binary bit stream. The binary bit stream is cached in an AP access point.

[0015] Preferably, the transmission of the downlink signal includes the following steps:

[0016] The relay cache signal is output based on the AP output network port and amplified and forwarded; the amplified and forwarded signal is serial / parallel converted; the converted signal is even-numbered subcarrier mapped and conjugate symmetric mapped to obtain a complex conjugate symmetric vector Y; the complex conjugate symmetric vector Y is OFDM modulated based on IFFT transformation, and then parallel / serial converted, and a DC bias is added to drive the LED to emit light to form a visible light line-of-sight link for optical signal transmission.

[0017] Preferably, decoding and transmitting the signal on the downlink includes the following steps:

[0018] Based on the photoelectric sensor, the optical signal transmitted on the downlink is obtained, and the optical / electrical conversion is completed, and then the serial / parallel conversion is performed on the formed electrical signal; the converted electrical signal is OFDM demodulated based on the IFFT transformation to obtain a complex conjugate symmetric vector Y; the complex conjugate symmetric vector Y is QAM demodulated to obtain a binary bit stream; the binary bit stream is decoded and output to the user terminal through the wireless network port.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Improved transmission capacity of the backhaul link: The backhaul link uses the visible light band as the carrier, and the signal from the backbone network is loaded on the odd subcarriers for OFDM multi-carrier modulation before being transmitted to the access point. This improves the spectrum utilization of the limited bandwidth and greatly improves the transmission capacity compared to a single carrier.

[0021] (2) Improved user service experience: The downlink from the access point to the user also uses the visible light band as the carrier, and the signal from the backhaul link is loaded on the even subcarrier for OFDM multi-carrier modulation, which will not cause interference to the information on the backhaul link. This not only improves the spectrum utilization, but also greatly reduces the probability of user interruption, and the user experience will be greatly improved.

[0022] (3) Low system implementation complexity and cost: The transmission of the backhaul link is based on the cooperation of the existing power line link and the point-to-point visible light link, and no additional lighting light sources and wired channels are required in the corresponding link structure. It can be implemented based on existing indoor light sources and facilities, thereby greatly reducing the complexity and cost of the Li-Fi network system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the backhaul link in the system of the present invention;

[0024] Figure 2 Schematic diagram of the structure of the downlink in the system of the present invention;

[0025] Figure 3 This is a block diagram of information transmission for the backhaul link in the present invention;

[0026] Figure 4 This is a block diagram of downlink information transmission in the present invention;

[0027] Figure 5 A general flow chart of the method of the present invention;

[0028] Figure 6 is a detailed flow chart of the method of the present invention; DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1:

[0031] See also Figure 1-Figure 2 As shown, the present invention provides a system for realizing all-optical double-hop transmission in a Li-Fi network based on visible light, characterized by: comprising a backhaul link structure formed by a base station, an AP access point, a photodetector, and an LED combination; and also comprising a downlink structure formed by a base station, an AP access point, a photodetector, and a user terminal combination;

[0032] in:

[0033] like Figure 1 Figure 1 is a schematic diagram of the backhaul link structure. In the figure, 1 represents a base station (BS), 2-7 represent AP access points, and 1-7 all use HL2000 commercial white light LED light sources, 8-13 represent photodetectors, and their models are PDA10A-EC, 14-19 all represent LEDs, and use CreeQ5 white light LEDs, and 20-25 represent visible light line-of-sight links between LEDs and photodetectors;

[0034] like Figure 2 As shown in the figure, it is a structural diagram of the downlink. In the figure, 1-2 represent base stations (BS), 3-4 represent AP access points, and 1 and 4 both use HL2000 commercial white light LED light sources, 2 uses creeQ5 white light LED, 3 and 6 are both PDA10A-EC photodetectors, 7 represents a user terminal, 5 represents a point-to-point visible light line-of-sight link between the base station and the AP access point, 8 represents a visible light line-of-sight link between the base station and the user terminal, and 9 represents a visible light line-of-sight link between the access point and the user terminal.

[0035] The connection between the base station and the AP access point can be formed based on the existing wired link, while the connection between the AP access point and the photodetector can be realized based on the installed LED. The same effect also applies to the downlink structure. Therefore, when constructing the entire system, it can be realized based on existing indoor light sources and facilities, thereby greatly reducing the complexity and cost of implementing the Li-Fi network system.

[0036] Example 2:

[0037] See also Figure 3-Figure 6As shown, and based on the above system, the present invention also provides a method for realizing all-optical double-hop transmission in a Li-Fi network based on visible light, comprising the following steps:

[0038] Step 1: Decode the data cached by the base station through a decoder to generate a binary bit stream.

[0039] Step 2. Perform QAM modulation on the binary bit stream to obtain the complex signal vector X D , and perform serial / parallel conversion on the complex signal vector;

[0040] The specific complex signal vector X D for:

[0041] X D =[X1, X2, L, X k ], k = 1, 2, L, N / 4;

[0042] Where N is the length of the IFFT transform, and the complex signal vector X D The length of is N / 2-1.

[0043] Step 3. For the complex signal vector X D Perform odd subcarrier mapping and conjugate symmetric mapping to obtain a complex conjugate symmetric vector X;

[0044] Specifically, the length of the complex conjugate symmetric vector X is N, and the complex conjugate symmetric vector X is:

[0045]

[0046] Step 4. Perform OFDM modulation on the complex conjugate symmetric vector X based on IFFT transform to obtain a time domain signal vector;

[0047] The length of the specific time domain signal vector is N, and the time domain signal vector is:

[0048] x1, x2, Lx N .

[0049] Step 5. Perform parallel / serial conversion on the time domain signal vector and add a DC bias to drive the LED to emit light to form a visible light line-of-sight link for optical signal transmission.

[0050] Step 6. The optical signal transmitted on the backhaul link is acquired based on the photoelectric sensor, and optical / electrical conversion is completed, and then the formed electrical signal is converted into serial / parallel.

[0051] Step 7. Perform OFDM demodulation on the converted electrical signal based on IFFT transformation to obtain a complex conjugate symmetric vector X.

[0052] Step 8. Perform QAM demodulation on the complex conjugate symmetric vector X to obtain a binary bit stream.

[0053] Step 9: Cache the binary bit stream into the AP access point.

[0054] Step 10. Output the relay buffer signal based on the AP output network port and amplify and forward it.

[0055] Step 11: Perform serial / parallel conversion on the amplified and forwarded signal.

[0056] Step 12. Perform even subcarrier mapping and conjugate symmetric mapping on the converted signal to obtain a complex conjugate symmetric vector Y.

[0057] Specifically, the length of the complex conjugate symmetric vector Y is N, and the complex conjugate symmetric vector Y is:

[0058]

[0059] Step 13. Perform OFDM modulation on the complex conjugate symmetric vector Y based on IFFT transformation, then perform parallel / serial conversion, add a DC bias, drive the LED to emit light, form a visible light line-of-sight link, and transmit optical signals.

[0060] Step 14: The optical signal transmitted on the downlink is acquired based on the photoelectric sensor, and optical / electrical conversion is completed, and then the formed electrical signal is converted into serial / parallel.

[0061] Step 15. Perform OFDM demodulation on the converted electrical signal based on IFFT transformation to obtain a complex conjugate symmetric vector Y.

[0062] Step 16. Perform QAM demodulation on the complex conjugate symmetric vector Y to obtain a binary bit stream.

[0063] Step 17: Decode the binary bit stream and output it to the user terminal through the wireless network port.

[0064] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for realizing all-optical double-hop transmission in a Li-Fi network based on visible light, applied to a system, characterized in that: The steps include: Obtain base station data and transmit signals on the backhaul link based on odd subcarrier mapping and visible light line-of-sight links; Relaying and caching the signal on the backhaul link based on the AP access point; Obtain the relay buffer signal and transmit the downlink signal based on even subcarrier mapping and visible light line-of-sight link; Decode and transmit the signal on the downlink, and output the decoded signal to the user terminal, completing the double-hop transmission of the entire signal. The transmission of the signal on the backhaul link includes the following steps: The data buffered by the base station is decoded by a decoder to generate a binary bit stream; Perform QAM modulation on the binary bit stream to obtain a complex signal vector X D , and perform serial / parallel conversion on the complex signal vector; For the complex signal vector X D Perform odd subcarrier mapping and conjugate symmetric mapping to obtain a complex conjugate symmetric vector X; perform OFDM modulation on the complex conjugate symmetric vector X based on IFFT transformation to obtain a time domain signal vector; The time domain signal vector is converted into parallel / serial, and a DC bias is added to drive the LED to emit light to form a visible light line-of-sight link for optical signal transmission. The relay cache comprises the following steps: The optical signal transmitted on the backhaul link is acquired by a photoelectric sensor, and optical / electrical conversion is completed. The resulting electrical signal is then converted serially / parallel. Performing OFDM demodulation on the converted electrical signal based on IFFT transformation to obtain a complex conjugate symmetric vector X; performing QAM demodulation on the complex conjugate symmetric vector X to obtain a binary bit stream; Cache the binary bit stream into the AP access point, The transmission of the downlink signal comprises the following steps: Output the relay buffer signal based on the AP output network port and amplify and forward it; Amplify the forwarded signal and perform serial / parallel conversion; Performing even subcarrier mapping and conjugate symmetric mapping on the converted signal to obtain a complex conjugate symmetric vector Y; The complex conjugate symmetric vector Y is subjected to OFDM modulation based on IFFT transformation, and then parallel / serial conversion is performed, and a DC bias is added to drive the LED to emit light to form a visible light line-of-sight link for optical signal transmission. Decoding and transmitting the downlink signal includes the following steps: The optical signal transmitted on the downlink is acquired by a photoelectric sensor, and optical / electrical conversion is completed, and then the resulting electrical signal is converted into serial / parallel. Performing OFDM demodulation on the converted electrical signal based on IFFT transformation to obtain a complex conjugate symmetric vector Y; performing QAM demodulation on the complex conjugate symmetric vector Y to obtain a binary bit stream; Decode the binary bit stream and output it to the user terminal through the wireless network port, The complex signal vector X D for: X D =[X1,X2,L,X k ],k=1,2,L,N / 4, Where N is the length of the IFFT transform, and the complex signal vector X D The length of is N / 2-1, the length of the complex conjugate symmetric vector X is N, and the complex conjugate symmetric vector X is: The length of the time domain signal vector is N, and the time domain signal vector is: x1, x2, L x N 。

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