WO2021203487A1 - 光纤使能光无线通信系统及方法 - Google Patents
光纤使能光无线通信系统及方法 Download PDFInfo
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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
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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
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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
- H04B10/40—Transceivers
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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
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
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- H—ELECTRICITY
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- 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
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- H04B10/516—Details of coding or modulation
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- H—ELECTRICITY
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- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
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Definitions
- the invention relates to an optical wireless communication technology, in particular to an optical antenna, a fiber-enabled optical wireless communication (FE-OWC, fiber enabled optical wireless communication) device, an FE-OWC system and a method, and belongs to the field of mobile communication technology.
- FE-OWC fiber-enabled optical wireless communication
- optical wireless communication uses optical bands to provide very rich spectrum resources and supports high-speed data transmission. It is a highly potential wireless communication method. Compared with high-frequency radio frequency wireless communication, optical wireless communication also has the advantages of low complexity of receiving and sending signals, and mature communication devices and equipment.
- Visible light communication is a research direction in optical wireless communication.
- the signal is modulated to the amplitude of visible light, and LEDs are used to provide illumination while transmitting data signals to user terminals.
- LEDs In order to meet the needs of lighting, LEDs generate wide beams to cover the entire communication area.
- the channel coefficients of optical wireless communication have a high degree of correlation.
- a single optical transmitting node transmits an omnidirectional signal, which is usually regarded as a single transmitting antenna, which can only transmit a single data signal, and the number of user terminals served by the system at the same time is limited.
- the modulation bandwidth of the LED is about 20MHz
- the abundant spectrum resources in optical wireless communication cannot be fully utilized, and the transmission rate of the system is low, which cannot meet the demand for ultra-high-speed data transmission.
- the current visible light wireless communication system only considers the downlink transmission from the base station to the user terminal, and cannot support two-way communication.
- infrared optical wireless communication By generating a directional narrow beam, the optical signal energy is concentrated to the user terminal, which greatly improves the receiving energy.
- the laser is used to generate optical signals to support a transmission rate of tens of Gbps.
- the infrared light beam generated by the laser has extremely strong directivity, the transceiver device needs to be accurately aligned, which greatly increases the complexity of the system in scenarios such as user movement, and most infrared optical wireless optical communication systems only Considering point-to-point single link transmission, it cannot support simultaneous communication of multiple or a large number of user terminals.
- the purpose of the present invention is to provide an optical antenna, and based on this
- the FE-OWC device, FE-OWC system and method of the optical antenna can make full use of the abundant spectrum resources of the optical band, realize the full coverage of the signal in the communication area and support the high-rate two-way communication of the terminal mobility, and meet the needs of future mobile communication applications .
- the optical antenna of the present invention includes an array of optical fiber transceiver ports and a lens or reflector; in the process of signal transmission, the light emitted by a single optical fiber transceiver port is refracted by the lens or reflected by the reflector. A light beam with a certain angle range is generated in a certain direction, and the light from different optical fiber transceiver ports is refracted or reflected to different directions; in the process of receiving signals, the received light from different directions is coupled into after being refracted by a lens or reflected by a mirror.
- Different optical fiber transceiver ports receive, and different optical fiber transceiver ports receive optical signals in different directions.
- the optical fiber transceiver port in the optical antenna includes an optical fiber port and a micro lens; in the process of transmitting a signal, the optical signal from a single optical fiber port is refracted by the micro lens to generate a light beam with a certain angle range; In the signal process, the micro lens couples the optical signal within a certain angle range into the fiber port.
- the optical antenna uses an array of optical fiber transceiving ports and lenses or mirrors to generate light beams in different directions. Different optical beams cover different areas. All optical beams generated by the optical fiber transceiving port array cover the entire communication area, realizing a full beam in the communication area. cover.
- the FE-OWC device of the present invention includes the above-mentioned optical antenna and an optical transceiver link; the optical antenna is used to send and receive optical signals in different directions; the optical antenna and the optical transceiver link are directly connected through optical fibers, or through optical switching Unit connection; the optical transceiver link is used to realize the mutual conversion between optical signals and electrical signals; a single FE-OWC device performs wireless communication with a single or a group of FE-OWC devices.
- the optical transceiver link is used to realize the mutual conversion between optical signals and electrical signals; in the process of sending signals, the electrical signals are added with a bias current to drive the laser to generate optical signals corresponding to the electrical signals, or use External modulator mode, the optical signal and electrical signal generated by the laser source are input to the external modulator to generate the corresponding optical signal.
- the optical signal is amplified by the optical amplifier and transmitted to the optical antenna through the optical fiber; in the process of receiving the signal, the optical antenna receives
- the signal is transmitted to the optical transceiver link through the optical fiber, and after being amplified by the optical amplifier, the optical signal is detected by the optical detector and converted into the corresponding electrical signal.
- each optical transceiver link corresponds to a fiber transceiver port, and the number of optical transceiver links is the same as the number of fiber transceiver ports; when the optical antenna and the optical transceiver link pass through When the optical switch unit is connected, the number of optical transceiver links is less than or equal to the number of fiber transceiver ports.
- the optical switch unit is used to switch the correspondence between the optical transceiver link and the fiber transceiver port, and generate the signal in the optical transceiver link with the optical antenna. Corresponding to the beams.
- the FE-OWC device on the base station side further includes a baseband signal processing unit, the baseband signal processing unit includes A/D and D/A modules and a digital baseband processing and control module; in the downlink transmission process, the digital baseband processing on the base station side
- the and control module is used to realize user scheduling and multi-user precoding transmission, and generate the transmission signal of each user terminal.
- the D/A module is used to convert the transmission signal generated by the digital baseband processing and control module into an analog signal and input into the optical transceiver link ;
- the A/D module is used to convert the electrical signal output by the optical transceiver link at the base station side into a digital signal, and the digital baseband processing and control module is used to detect the signals received by multiple users and restore each user terminal’s Send the signal.
- the user terminal side FE-OWC device further includes a baseband signal processing unit, the baseband signal processing unit includes A/D and D/A modules and a digital baseband processing and control module; in the downlink transmission process, the A/D module is used In order to convert the electrical signal output by the optical transceiver link on the user terminal side into a digital signal, the digital baseband processing and control module is used to detect the received signal and restore the transmission signal of the base station; in the uplink transmission process, the digital baseband processing on the user terminal side The and control module is used to realize precoding transmission, and the D/A module is used to convert the generated transmission signal into an analog signal and input the optical transceiver link.
- the FE-OWC device on the base station side further includes a baseband signal processing unit, the baseband signal processing unit includes a baseband modulation and baseband demodulation module and a digital baseband processing and control module; in the downlink transmission process, the baseband side digital baseband processing and The control module is used to allocate non-overlapping beam sets for different user terminals to generate digital baseband signals sent to each user terminal.
- the baseband modulation module is used to generate analog baseband signals sent to each user terminal and transmit them to the corresponding optical transceiver chain.
- the baseband demodulation module is used to demodulate the analog baseband received signal output by the optical transceiver link on the base station side to generate a digital baseband signal
- the digital baseband processing and control module It is used to restore the transmitted signal of each user terminal according to the result of beam allocation and the digital baseband signal on the corresponding beam of each user terminal.
- the user terminal side FE-OWC device further includes a baseband signal processing unit, the baseband signal processing unit includes a baseband modulation and baseband demodulation module and a digital baseband processing and control module; in the downlink transmission process, the user terminal side baseband demodulation The module is used to demodulate the analog signal output by the optical transceiver link to generate a digital baseband signal.
- the baseband signal processing unit includes a baseband modulation and baseband demodulation module and a digital baseband processing and control module; in the downlink transmission process, the user terminal side baseband demodulation The module is used to demodulate the analog signal output by the optical transceiver link to generate a digital baseband signal.
- the digital baseband processing and control module is used to select the corresponding fiber transceiver port of the base station, and restore the transmitted signal on the base station side according to the received digital baseband signal;
- the digital baseband processing and control module on the user terminal side is used to generate the uplink digital baseband transmission signal
- the baseband modulation module is used to generate the analog baseband transmission signal, which is transmitted to the optical transceiver link, using the fiber transceiver port corresponding to the base station Send it.
- the base station and user terminal configurations of the system are configured with the above-mentioned FE-OWC device.
- Multi-user MIMO or massive MIMO optical wireless communication or beam division multiple access BDMA optical wireless communication is realized between the base station and the user terminal.
- the FE-OWC method of the present invention is based on the FE-OWC system, which calculates the link budget of single link transmission and establishes the transmission channel model of the electrical signal at the transceiver end;
- the link budget includes the transmission end electrical-optical conversion, optical Wireless channel gain, receiving end photoelectric conversion, and receiving end electrical noise;
- the transmitting end electro-optical conversion part establishes the corresponding relationship between the optical power output by the transmitting end and the input electrical signal according to the photoelectric characteristics of the electro-optical conversion device;
- the optical wireless channel gain is the transmission The gain of the wireless channel between the optical fiber transceiver port at the receiving end and the optical transceiver port at the receiving end;
- the photoelectric conversion part at the receiving end considers the two processes of receiving optical signals through optical amplifier amplification and optical detector detection to establish the relationship between the input optical signal and the output electrical signal at the receiving end
- the electrical noise at the receiving end includes electrical noise introduced by optical amplifiers and photodetectors.
- the relationship between signal power and noise power in the received electrical signal of a single link is established; on the basis of a single link budget, a complete A channel model for electrical signal transmission from the sender to the receiver; based on this channel model, a multi-user MIMO or massive MIMO or beam division multiple access optical wireless communication method is implemented between the base station and the user terminal.
- the optical wireless channel gain describes the channel gain of optical wireless transmission from the transmitting end to the receiving end, including beam modeling at the transmitting end, free space transmission channel gain, the receiving power ratio of the optical fiber transceiver port at the receiving end, and the coupling efficiency of the optical fiber port.
- beam modeling at the transmitting end describes the light intensity distribution of a single beam after the light emitted by the fiber transceiver port is refracted by a lens or reflected by a reflector.
- a single fiber transceiver port is The light intensity of the user terminal is progressively orthogonal; the free space transmission channel gain considers the transmission process of the optical beam from the sender to the receiver through the free space, which is inversely proportional to the square of the transmission distance; the receive power ratio of the fiber transceiver port at the receiver describes a single fiber transceiver The ratio of the optical power received by the port to the total received power of the user is proportional to the common area of the received light projection on the receiving plane and the optical fiber transceiver port; the coupling efficiency of the optical fiber port is the ratio of the received light at the optical fiber port that can be coupled into the optical fiber, It is proportional to the common area of the angle range of the incident light at the fiber port and the acceptance angle of the fiber port.
- the FE-OWC method of the present invention is a multi-user MIMO or massive MIMO optical wireless communication method based on the FE-OWC system.
- the specific communication process includes the following steps:
- the base station broadcasts a downlink synchronization signal, and the user terminal uses the received signal to establish and maintain synchronization with the base station;
- Channel sounding the user terminal sends an uplink sounding signal, and the base station estimates the channel information of each user terminal according to the received sounding signal;
- Downlink transmission The base station uses the channel information of each user terminal and the low-rank characteristics of the channel for precoding transmission, and simultaneously sends all user terminal signals, including pilot signals and data signals, and each user terminal estimates channel information based on the received pilot signals , And use the channel information to recover the data signal;
- Uplink transmission The user terminal uses precoding transmission to simultaneously send signals to the base station, including pilot signals and data signals.
- the base station receives the signal superimposition of all user terminals, estimates the channel information of each user terminal based on the pilot signal, and uses the low channel
- the rank characteristic carries on the receiving processing, restores the data signal of each user terminal.
- the base station estimates the uplink channel from each user terminal to the base station through the uplink detection process, uses the channel reciprocity to obtain the downlink channel, decomposes the channel matrix into the product of the column vector and the row vector, and calculates each The received signal-to-interference-to-noise ratio and reachability and rate of the user terminal are designed to maximize the system and rate under the power constraints of a single fiber transceiver port to design the optimal linear precoding; or the base station uses the maximum line vector decomposed according to the channel matrix Compared with the transmission MRT or the regularized zero-forcing RZF precoding method, the precoding vector is used to simultaneously send all user terminal signals, including pilot signals and data signals; during the uplink transmission process, the base station receives the signal superimposition of all user terminals.
- the pilot signal estimates the uplink channel matrix of each user terminal and decomposes it into the product of the column vector and the row vector to design the optimal linear receiver with the goal of maximizing the system and rate; or the base station decomposes it according to the channel matrix of each user
- the column vector adopts the maximum ratio to combine the MRC receiver, and the linear receiver is used to detect the received data signal and restore the transmitted signal of each user terminal.
- each user terminal estimates the downlink transmission channel matrix according to the received pilot signal, and decomposes it into the product of the column vector and the row vector, designing the optimal linear receiver with the goal of maximizing the system and rate ,
- the user terminal uses the optimal linear receiver to detect the received data signal; in the uplink transmission process, each user terminal uses the reciprocity of the channel to obtain the uplink channel information according to the downlink channel estimation, and decomposes the channel matrix into column vectors and The product of the row vector, under the condition of total power constraint, design the optimal precoding vector with the goal of maximizing the system and rate, and the user terminal uses the precoding vector to simultaneously transmit uplink signals, including pilot signals and data signals.
- the FE-OWC method of the present invention is a beam division multiple access optical wireless communication method based on the FE-OWC system.
- the channel information for different user terminals allocates beams that do not overlap each other. Each beam sends and receives signals from at most one user terminal, and uses optical beams in different directions to communicate with the user terminal at the same time; the user terminal selects the corresponding direction of the base station according to the channel information Use a single beam to communicate with a single base station; the specific communication process includes the following steps:
- the base station broadcasts a downlink synchronization signal, and the user terminal uses the received signal to establish and maintain synchronization with the base station;
- Channel sounding user terminals send uplink sounding signals, and the base station allocates beams to each user terminal according to the received sounding signals. For users communicating with the base station on the same time-frequency resource, the allocated beams do not overlap each other and each user is allocated only one beam ;
- the base station sends an independent signal on the beam allocated by each user terminal according to the beam allocation result, and each user terminal selects the beam corresponding to the base station for reception detection according to the received signal;
- Each user terminal sends a signal on the beam corresponding to the base station, and the base station receives and detects the transmitted signal of each user terminal on the beam allocated by each user terminal according to the result of the beam allocation.
- the base station sends a signal to each user terminal on the beam allocated by the beam according to the result of the beam allocation.
- Different beams send signals from different user terminals, and the multi-user downlink transmission link is decomposed into multiple parallel ones.
- the base station uses baseband modulation to generate user analog baseband transmission signals; in the uplink transmission process, the base station receives and detects the transmitted signal of the user terminal on the beam allocated by each user terminal according to the result of beam allocation.
- the base station uses different The beam receives and detects signals from different user terminals, the multi-user uplink transmission link is decomposed into multiple parallel single-user links, and the base station uses baseband demodulation to generate digital baseband signals for each user terminal.
- each user terminal selects the beam corresponding to the base station according to the strength of the received signal, and uses the baseband demodulation method on the corresponding beam to generate a digital baseband signal; in the uplink transmission process, each user terminal corresponds to the base station On the beam, the baseband modulation method is used to generate the analog baseband signal.
- the base station uses optical antennas composed of optical fiber transceiver port arrays and lenses or mirrors to generate multiple or a large number of beams in different directions, different beams cover different areas, and the base station uses different beams to communicate with multiple or a large number of user terminals at the same time , Which greatly increases the number of user terminals supported by optical wireless communications.
- the present invention utilizes the ultra-high rate data transmission supported by optical fiber to significantly improve the transmission rate of each user terminal link and the system throughput.
- Base stations and user terminals use optical fiber transceiver ports to send and receive signals, which can realize two-way communication and solve the limitation of one-way transmission in optical wireless communication.
- the base station uses optical antennas to generate multiple or a large number of beams in different directions to achieve full beam coverage of the communication area.
- the base station only needs to switch the beam corresponding to the user terminal, and no complicated tracking system is required.
- the base station uses different beams to communicate with different user terminals, and decomposes the multi-user transmission link into multiple single-user transmission links.
- Each single-user transmission link can adopt optical modulation and optical demodulation (such as OOK modulation).
- OOK modulation optical demodulation
- A/D and D/A equipment may not be needed, which significantly reduces the complexity of implementing ultra-high-speed optical wireless communication systems.
- optical antenna and the optical transceiver link are connected by optical fiber. Due to the extremely low loss in the optical fiber transmission process, the optical antenna can be flexibly deployed, and the optical antenna is a passive system with low cost, which can greatly reduce the system construction cost.
- the optical antennas of the base station and the user terminal input the received optical signal into the optical fiber, and then use the optical fiber amplifier to amplify the optical receiving process, which can greatly improve the receiving capacity, thereby reducing the transmitting power of the transmitting end or increasing the communication distance.
- the proposed optical fiber-enabled optical wireless communication method can use mature optical fiber communication technology, devices and equipment to efficiently construct a high-speed optical wireless communication system to meet the needs of future mobile communication for transmission rates and system capacity orders of magnitude or more after 5G. Demand for a magnitude increase.
- the proposed optical fiber-enabled optical wireless communication system can also be conveniently docked with an optical fiber communication network to realize the extension of the optical fiber communication network to wireless coverage, thereby realizing mobile optical communication and all-optical communication supporting terminal mobility.
- Figure 1 is a schematic diagram of the architecture of a fiber-enabled optical wireless communication system
- Figure 2 is a schematic diagram of an optical transceiver link
- Figure 3 is a schematic diagram of the optical antenna structure
- Figure 4 is a schematic diagram of a beam pattern, (a) a single fiber transceiver port, (b) an array of fiber transceiver ports;
- Figure 5 is a schematic diagram of system throughput performance, (a) downlink transmission, (b) uplink transmission.
- the present invention discloses a fiber-enabled optical wireless communication (FE-OWC, fiber enabled optical wireless communication) system.
- the system architecture is shown in Figure 1.
- a single base station (BS, base station) simultaneously serves K user terminals (UT, user). terminal), both the base station and the user terminal are equipped with FE-OWC devices.
- the FE-OWC device includes an optical antenna, an optical transceiver link, and a baseband signal processing unit.
- the optical antenna and the optical transceiver link are connected by an optical fiber. Due to the extremely low loss during the optical fiber transmission process, the optical antenna can be flexibly deployed.
- Optical antennas are used to send and receive optical signals, including optical fiber transceiver port arrays and lenses or mirrors.
- the light emitted by a single fiber transceiver port is refracted by a lens or reflected by a mirror, and a light beam with a certain angle expansion is generated in a certain direction.
- the light emitted by different fiber transceiver ports is refracted or reflected to different directions.
- the optical fiber transceiver port array and lenses or mirrors are used to generate multiple optical beams in different directions to achieve full beam coverage of the communication area, that is, the optical beams corresponding to all optical fiber transceiver ports can cover the entire communication area.
- the received light rays in different directions are refracted by lenses or reflected by mirrors to different optical fiber transceiver ports, coupled into the optical fiber and transmitted to the optical transceiver link.
- the optical transceiver link realizes the mutual conversion between optical and electrical signals, and its system architecture is shown in Figure 2.
- the electric signal is added with a bias current to drive the laser diode (LD, laser diode) to generate an optical signal corresponding to the electric signal.
- An external modulator can also be used to combine the optical signal generated by the laser source with
- the electrical signal is input to the external modulator, and an optical signal corresponding to the electrical signal is generated.
- the optical signal passes through an optical amplifier, such as an erbium-doped fiber amplifier (EDFA, erbium-doped fiber amplifier), and is amplified and transmitted to an optical antenna for transmission through an optical fiber.
- EDFA erbium-doped fiber amplifier
- the optical signal received by the optical antenna is transmitted to the optical transceiver link through the optical fiber.
- the optical detector such as avalanche photodiode (APD, avalanche photodiode)
- APD avalanche photodiode
- the optical signal such as its intensity, Converted to the corresponding electrical signal.
- an optical circulator OC is used to separate optical signals in different directions.
- the optical antenna and the optical transceiver link are directly connected through an optical fiber, or through an optical switching unit.
- each optical transceiver link corresponds to a fiber transceiver port, and the number of optical transceiver links is the same as the number of fiber transceiver ports.
- the optical switching unit is used to switch the correspondence between the optical transceiver link and the optical fiber transceiver port, The signal in the link corresponds to the beam generated by the optical antenna.
- the baseband signal processing unit is used to implement functions including user scheduling and processing of receiving and sending signals.
- the embodiment of the present invention discloses two baseband signal processing methods.
- the baseband signal processing unit includes A/D and D/A modules and a digital baseband processing and control module.
- the base station and the user terminal implement multiple-input multiple-output or Massive MIMO optical wireless communication.
- the digital baseband processing and control module on the base station side is used to realize user scheduling and multi-user precoding transmission, and generate the transmission signal of each user terminal.
- the D/A module is used to generate the digital baseband processing and control module.
- the transmitted signal is converted into an analog signal and input into the optical transceiver link; the user terminal side A/D module is used to convert the electrical signal output by the optical transceiver link into a digital signal, and the digital baseband processing and control module is used to detect the received signal, Resume the transmission signal of the base station.
- the digital baseband processing and control module on the user terminal side is used to realize precoding transmission, the D/A module is used to convert the generated transmission signal into an analog signal and input into the optical transceiver link; the base station side A/D module is used In order to convert the electrical signal output by the optical transceiver link into a digital signal, the digital baseband processing and control module is used to detect the multi-user received signal and restore the transmitted signal of each user terminal.
- the baseband signal processing unit does not have A/D and D/A modules, and includes baseband modulation and baseband demodulation modules (such as OOK (on-off keying) modulation and demodulation) and digital baseband processing
- baseband modulation and baseband demodulation modules such as OOK (on-off keying) modulation and demodulation
- digital baseband processing With the control module, the base station and the user terminal realize the beam division multiple access (BDMA, multiple access) optical wireless communication of multiple users or a large number of users.
- BDMA beam division multiple access
- the digital baseband processing and control module on the base station side is used to allocate non-overlapping beam sets for different user terminals to generate digital baseband signals sent to each user terminal.
- the baseband modulation module is used to generate The sent analog baseband signal is transmitted to the corresponding optical transceiver link and sent using the corresponding optical transceiver port; the user terminal side baseband demodulation module is used to demodulate the analog signal output by the optical transceiver link to generate a digital baseband signal , The digital baseband processing and control module is used to select the fiber transceiver port corresponding to the base station, and restore the transmitted signal on the base station side according to the received digital baseband signal.
- the digital baseband processing and control module on the user terminal side is used to generate the uplink digital baseband transmission signal
- the baseband modulation module is used to generate the analog baseband transmission signal, which is transmitted to the optical transceiver link
- the optical fiber corresponding to the base station is used to transmit and receive
- the baseband demodulation module on the base station side is used to demodulate the analog baseband received signal output by the optical transceiver link to generate a digital baseband signal
- the digital baseband processing and control module is used for the result of beam allocation and each user terminal
- the digital baseband signal on the corresponding beam restores the transmitted signal of each user terminal.
- the optical antenna is composed of a fiber transceiver port array and a lens or a mirror.
- This embodiment takes the fiber transceiver port array and lens as an example.
- the structure is shown in FIG. 3, and an optical antenna equipped with a mirror can be similarly obtained.
- the corresponding design method can be applied to other fiber structures.
- the light intensity emitted by the single-mode fiber port approximately obeys the Gaussian distribution.
- the light intensity distribution can be modeled as
- I 0 (z) represents the strongest light intensity on the cross section at a distance of z
- ⁇ is the wavelength of light.
- the light emitted from the fiber port is mainly concentrated in the range of the light spot ⁇ 1 (z).
- a microlens is configured at the optical fiber port to form an optical fiber transceiver port.
- the focal length of the microlens is f and the distance between the microlens and the fiber port is d 1 , the intensity distribution of the light emitted by the fiber transceiver port can be expressed as
- ⁇ 2 (z) is the spot size of the light emitted by the optical fiber transceiver port at position z
- ⁇ C describes the angle range of the optical fiber transceiver port to send and receive light.
- the angle range of the optical fiber transceiver port to generate the beam can be changed.
- the distance d 1 should be reduced, that is, the micro lens is as close to the fiber port as possible.
- ⁇ is the polarization angle relative to the z-axis
- U( ⁇ ) is the unit step function
- the optical antenna includes a fiber optic transceiver port array and a lens.
- M optical fiber transceiver ports form a square array, a circular array, or a hexagonal array, etc.
- a single lens covers the entire fiber transceiver port array, or multiple lenses cover the entire fiber transceiver port array, and different lenses cover different fiber transceiver ports.
- the angle between the light emitted by the i-th optical fiber transceiver port and the vertical direction is After being refracted by the lens, the direction is
- F is the focal length of the lens.
- the light from a single optical fiber transceiver port can be refracted by a lens to generate a light beam with a certain angle range in a certain direction.
- ⁇ 1-d 2 /F
- the intensity distribution of the light with the angle (relative refraction angle) ⁇ i with the central light can be expressed as
- T lens represents the lens gain.
- the optical fiber transceiver port array and lens are used to design the horizontal and vertical positions of the optical fiber transceiver port array to generate multiple or a large number of optical beams in different directions to cover the entire communication area.
- the maximum angular range of the communication coverage area is ⁇ .
- the adjacent beams overlap at the position where the maximum power is attenuated by half, then the optical fiber transceiver port array and the lens The distance between
- ⁇ 1/2 is the angular position at which the maximum power is attenuated to half. From this, the coordinates of the i-th optical fiber transceiver port can be obtained as
- d a is the distance between adjacent ports optical transceivers, satisfying m 1 and m 2 represent the positions of m 1 row and m 2 column in the square array, satisfying
- the fiber optic transceiver ports can also be arranged in a circular array or a hexagonal array. When they are arranged in a circular array, the fiber optic transceiver ports are evenly arranged at the center of the circle and on the circle with a radius of r c , 2r c, etc., by adjusting the radius of the circle and the fiber
- the interval between the transceiver ports makes the light from the fiber optic transceiver ports refracted by the lens to achieve full beam coverage of the receiving plane; when arranged in a hexagonal array, at the center, and the hexagonal side length is rh, which is a honeycomb structure that expands outward
- the optical fiber transceiver ports are arranged in positions, and the light from the optical fiber transceiver ports is refracted by the lens to achieve full beam coverage by adjusting the side length of the hexagon.
- the full beam coverage of the communication area can also be achieved through an array of optical fiber transceiver ports and mirrors.
- a single reflector covers the entire optical fiber transceiver port array, or multiple reflectors collectively cover the entire optical fiber transceiver port array.
- the light intensity distribution model (6) of a single optical fiber transceiver port the light emitted from the optical fiber transceiver port at the position (x i , y i , z i ) established by geometric optics is reflected by the mirror to obtain The direction and angle range of the beam generated by the fiber optic transceiver ports at different positions after being reflected by the reflector.
- the position of the optical fiber transceiver port is designed so that the light emitted by the optical fiber transceiver port is reflected by the reflector and covers the entire communication area.
- the distance d 2 between the fiber transceiver port array and the lens tends to the focal length F of the lens, and the fiber transceiver port array is located at the focal plane of the lens.
- the light emitted from different optical fiber transceiver ports is refracted to different directions by the lens, and illuminates different areas.
- the light from a single optical fiber transceiver port reaches the asymptotically orthogonal light intensity to the two user terminals.
- a single fiber transceiver port can transmit signals from one user at most, and different user terminals receive optical signals from different fiber transceiver ports.
- Figure 4 shows the beam pattern generated by the 8 ⁇ 8 fiber optic transceiver port array on the receiving plane.
- the base station In a 5m ⁇ 5m communication scene with a height of 3m, the base station is located at the center of the scene.
- Figure 4 (a) shows the beam pattern generated by a single fiber transceiver port in the fiber transceiver port array, that is, the distribution of light intensity on the receiving plane. The light from a single fiber transceiver port is refracted by the lens and converges to a certain area to form A beam;
- Figure 4 (b) shows the beam pattern generated by the fiber optic transceiver port array. Different fiber optic transceiver ports generate beams in different directions, thereby using 8 ⁇ 8 beams to achieve full beam coverage of the entire communication area.
- the link budget of single link transmission is considered, and a complete channel model for downlink transmission and uplink transmission is established.
- First take the following transmission process as an example to calculate the link budget from the base station to the user terminal, including four parts: electrical-optical conversion at the transmitting end, optical wireless channel gain, photoelectric conversion at the receiving end, and electrical noise at the receiving end.
- electrical-optical conversion at the transmitting end including four parts: electrical-optical conversion at the transmitting end, optical wireless channel gain, photoelectric conversion at the receiving end, and electrical noise at the receiving end.
- the uplink transmission process is similar to the downlink transmission process, and the uplink transmission channel model can be similarly established.
- the electrical-optical conversion converts the electrical signal into the corresponding optical signal, which is achieved by directly changing the drive current of the laser, or by an external modulator.
- directly changing the drive current of the laser when the drive current is higher than the threshold I th , there is a linear correspondence between the output optical power and the input current. Therefore, adding a bias current I B (I B > I th ) to the electrical signal x carrying information and inputting the laser, the output light intensity in the linear range can be expressed as
- P LD,0 is the output optical power driven by the bias current
- m is the conversion coefficient between the optical intensity and the input current.
- the optical signal output by the laser is amplified by the optical amplifier and then sent. Let the gain of the optical amplifier be G, then the output light intensity is
- Optical wireless channel gain describes the gain of the wireless transmission channel from the fiber port on the base station side to the fiber port on the user terminal side, including beam modeling at the transmitter, free space transmission channel gain, the received power ratio of the fiber transceiver port at the receiver, and the coupling efficiency of the fiber port. Parts.
- the beam modeling of the transmitting end has been discussed in the optical antenna design.
- the k-th user terminal and the i-th optical fiber transceiver port of the base station have an angle of When the light intensity distribution of the optical fiber port light is given by (8) Given.
- Ak represents the area of the k-th user terminal side lens
- d k is the distance from the base station to the user terminal
- ⁇ d (d k ) describes the channel attenuation caused by the transmission distance d k , and can be calculated according to the law of conservation of light transmission energy
- the channel attenuation is inversely proportional to the square of the transmission distance, and also inversely proportional to ⁇ 2 , ⁇ describes the angular expansion change of the beam after being refracted by the lens.
- ⁇ is small, the beam is concentrated in a smaller angular range, and the channel gain is larger .
- the received light is refracted by the lens and then received by the optical fiber transceiver port.
- the incident angle of the incident light is The incident position is When it is refracted by the lens and transmitted in free space After the distance, the angle and position at the receiving plane are
- the power of the light received by a single optical fiber transceiver port is proportional to the irradiated area of the received light on the receiving plane and the common area of the optical fiber transceiver port. Let the area of the j-th optical fiber transceiver port be A j , then the j-th optical fiber transceiver port receives light The power ratio is
- the optical antenna includes a fiber optic transceiver port array and a reflector
- the power of the light received by a single fiber transceiver port and the irradiation area of the received light on the receiving plane are proportional to the common area of the fiber transceiver port.
- the fiber port is equipped with a microlens to expand the beam angle ⁇ C. According to the reversibility of light transmission, light within the angle ⁇ C can be coupled into the fiber for transmission, then the receiving angle of the fiber port is
- ⁇ represents the receiving angle in the horizontal direction
- ⁇ represents the receiving angle in the vertical direction
- Coupling coefficient I the ratio of the volume of the common area of ⁇ f and ⁇ s to the area of ⁇ s, which can be expressed as
- the gain of the wireless optical transmission channel from the i-th fiber port on the base station side to the j-th fiber port of the k-th user terminal can be obtained as
- the received optical signal is first amplified by an optical amplifier, and then a photodetector is used to convert the optical signal into a corresponding electrical signal.
- the received optical signal power is P 1 and the gain of the optical amplifier is G
- the output power of the optical amplifier is GP 1 .
- the optical signal output by the optical amplifier is converted into a corresponding electrical signal by a photodetector (such as an avalanche diode).
- the amplification factor of the photodetector is M p
- the responsivity of the photodetector is R
- the output electrical signal of the photodetector is M p RGP 1 .
- the electrical signal transmission channel gain between the i-th optical fiber transceiver port of the base station and the j-th optical fiber transceiver port of the k-th user terminal can be expressed as
- the i-th optical fiber transceiver port of the base station sends electrical signals
- the relationship between the electrical signal y kj received by the j-th optical fiber transceiver port to the k-th user terminal is
- n p is noise, which mainly includes the shot noise of the photodetector and the beat noise mixed with the amplified spontaneous emission noise.
- the variance can be approximately expressed as
- q is the electronic charge
- B e is the electrical signal bandwidth
- F(M p ) is the noise figure of the photodetector
- NF is the noise figure of the optical amplifier. Therefore, the received signal-to-noise ratio of a single link can be calculated as
- the complete channel model from the base station to the user terminal is considered below.
- the base station is configured with M fiber optic transceiver ports
- the user terminal is configured with N fiber optic transceiver ports
- the electrical signal transmission channel matrix from the base station to the k-th user terminal is Its (j,i)th element is By (23), the optical wireless transmission channel gain Can be decomposed into
- the channel matrix Can be decomposed into in [ ⁇ ] T represents the transposition operation, and the result shows that the rank of the channel matrix is 1, showing low-rank characteristics.
- the channel model of uplink transmission is similar to the channel model of downlink transmission.
- the electrical-optical conversion and photoelectric conversion processes of the uplink transmission and the downlink transmission are the same, only the transmission power of the user terminal and the gain of the optical wireless transmission channel are different .
- the transmit power on the user terminal side is
- the intensity distribution of light emitted by the j-th fiber optic transceiver port of the k-th user terminal can be similarly modeled as in Is the relative refraction angle from the user to the base station, then the channel gain from the j-th fiber transceiver port of the k-th user terminal to the base station side lens can be modeled as
- A is the area of the base station side lens
- ⁇ u (d k ) represents the channel attenuation caused by the transmission distance d k
- the channel path of uplink transmission and the channel path of downlink transmission are reciprocal, that is, the k-th user terminal in the downlink transmission receives the signal of the i-th optical fiber transceiver port of the base station.
- the i-th fiber transceiver port of the base station receives the transmitted signal of the k-th user terminal; also on the user terminal side, the user's j-th fiber transceiver port receives the signal from the base station in the downlink transmission, and the base station receives the j-th signal in the uplink transmission.
- the signal from the fiber optic transceiver port is not limited to the signal of the fiber optic transceiver port.
- a base station uses multiple (several to tens) or a large number (hundreds to thousands) of beams to communicate with multiple or a large number of user terminals in two directions.
- the transceiver end is configured with A/D and D/A modules corresponding to the optical transceiver link, its digital baseband processing can achieve uplink and downlink multi-user MIMO (MU-MIMO, multi-user MIMO) transmission, and then achieve Multi-user MIMO optical wireless communication.
- MU-MIMO multi-user MIMO
- the base station can communicate with a large number of user terminals at the same time to realize massive MIMO (massive MIMO) optical wireless communication.
- massive MIMO massive MIMO
- the multi-user MIMO/mass MIMO communication process includes the following four steps: synchronization, channel sounding, downlink transmission, and uplink transmission. 1)
- the base station broadcasts a downlink synchronization signal, and the user terminal uses the received signal to establish and maintain synchronization with the base station. 2)
- the user terminal sends an uplink sounding signal, and the base station estimates the channel information of each user terminal based on the received sounding signal.
- the base station uses the channel information of each user terminal and the low-rank characteristics of the channel to perform precoding transmission, and simultaneously transmits signals of all user terminals, including pilot signals and data signals. Each user terminal estimates channel information based on the received pilot signals. And use the channel information to recover the data signal. 4)
- the user terminal uses precoding transmission to simultaneously send signals to the base station, including pilot signals and data signals.
- the base station receives the signal superimposition of all user terminals, estimates the channel information of each user terminal based on the pilot signal, and uses the low rank of the channel
- the feature performs receiving processing and restores the data signal of each user terminal. The following will specifically introduce the downlink transmission and uplink transmission process.
- the base station sends signals from K user terminals at the same time, and the signal sent by the i-th optical fiber transceiver port to the k-th user terminal is recorded as Then the signal sent by the base station to the k-th user terminal is recorded as The received signal of the kth user terminal can be expressed as
- n k is Gaussian noise
- its mean value is 0
- the covariance matrix is a diagonal matrix ⁇ k
- the (j,j)th diagonal element is
- the base station estimates the uplink channel information according to the received sounding signal, and uses the reciprocity of the downlink channel and the uplink channel to obtain the downlink channel matrix.
- the rank of the channel matrix from the base station to a single user terminal is 1, and the channel matrix It can be decomposed into the form of the product of column vector and row vector, namely
- the signal sent by the base station to the k-th user terminal Is composed of independent and identically distributed data symbols Linearly precoded generate.
- the k-th user terminal adopts a linear receiver according to the received signal Detect the data signal, namely Then in downlink transmission, the received signal-to-interference and noise ratio of the k-th user terminal is
- e i [0,...,0,1,0,...,0] T is the unit vector, only the i-th element is 1, and the remaining elements are 0, p d is the base station side single fiber transceiver The power constraint of the port.
- the diagonal matrix D is an auxiliary matrix, so that the precoding vector satisfies the constraint condition.
- the optimal linear precoding can be obtained by the following algorithm:
- Step 2 Calculate the coefficients a j and b k according to formula (35).
- Step 3 Update the precoding vector according to formula (34) Calculate the sum rate (R d ) (i) .
- Step 4 Calculate the difference between the power constraint Among them, diag( ⁇ ) represents a column vector composed of diagonal elements.
- Step 5 If
- the base station uses the precoding vector Send a signal to the k-th user terminal, and the k-th user terminal uses a linear reception vector Detect the received signal and recover the data signal sent by the base station.
- the user terminal uses the channel reciprocity to obtain the uplink channel information through downlink channel estimation, and designs linear precoding to send independent signals, and the base station receives the superposition of the signals sent by the user terminal.
- the uplink signal sent for the kth user terminal can be expressed as in Is the user-side precoding vector, It is the transmission signal of the k-th user terminal.
- the received signal at the base station side can be expressed as
- I the gain of the uplink transmission electrical signal from the kth user terminal to the base station. Since the rank of the channel matrix is 1, it can be decomposed into the form of the product of the column vector and the row vector, namely z is the electrical signal noise on the base station side, its mean value is 0, the covariance matrix is a diagonal matrix ⁇ , and the (i,i)th element is
- the base station uses a linear receiver according to the received signal Detect the transmitted signal of the k-th user terminal, namely
- the uplink transmission system and rate are the uplink transmission system and rate.
- p u is the power constraint of each user terminal in uplink transmission.
- the optimal precoding vector for maximizing the uplink transmission system and rate is
- the optimal linear receiver is the optimal linear receiver.
- c k is an auxiliary variable related to the transmission power of the k-th user terminal.
- the optimal linear precoding and linear receiver can be obtained by the following algorithm:
- Step 2 Given the value of c i of other user terminals, calculate the value of c k according to formula (43), and update the precoding vector and receiver vector according to formulas (41) and (42), using formula (39) Calculate the uplink transmission and rate R (k) .
- the optimal c k value of each user terminal can be obtained, and the precoding vector can be calculated according to formulas (41) and (42) And the receiver vector
- the k-th user terminal uses the precoding vector Send a signal to the base station, the base station uses a linear reception vector Detect the signal of the k-th user terminal.
- the above designing the optimal linear precoding and optimal linear receiver with the goal of maximizing the system and rate is an example to illustrate.
- the base station can also use the maximum ratio transmission (MRT, maximum ratio transmission) or maximum ratio transmission according to the row vector of the channel matrix decomposition.
- MRT maximum ratio transmission
- Precoding methods such as regularized zero forcing (RZF, regularized zero forcing) are used for precoding design, and the maximum ratio combining (MRC, maximal ratio combining) receiver can also be used according to the column vector decomposed by the channel matrix of each user.
- RZF regularized zero forcing
- MRC maximal ratio combining
- BDMA Beam Division Multiple Access
- the transceiver end of the FE-OWC system may not be equipped with broadband A/D and broadband D/A modules corresponding to the optical transceiver link.
- the base station can share multiple user terminals or a large number of user terminals.
- BDMA beam division multiple access
- the fiber-enabled beam division multiple access optical wireless communication method is: the base station allocates non-overlapping beams to different user terminals according to the channel information of each user terminal, and each beam sends and receives signals from at most one user terminal, using different directions
- the optical beam communicates with the user terminal in both directions at the same time; the user terminal selects the beam in the corresponding direction of the base station according to the channel information, and uses a single beam to communicate with a single base station.
- the specific communication process includes the following four steps: synchronization, channel detection, downlink transmission, and uplink transmission. 1)
- the base station broadcasts a downlink synchronization signal, and the user terminal uses the received signal to establish and maintain synchronization with the base station.
- the user terminal sends an uplink sounding signal, and the base station allocates a beam to each user terminal according to the received sounding signal. For users communicating with the base station on the same time-frequency resource, the allocated beams do not overlap each other and each user is allocated only one beam.
- the base station sends an independent signal on the beam allocated by each user terminal according to the beam allocation result, and each user terminal selects the beam corresponding to the base station for reception detection based on the received signal.
- each user terminal sends a signal on the beam corresponding to the base station, and the base station receives and detects the transmitted signal of each user terminal in the beam allocated by each user terminal according to the result of beam allocation.
- the downlink transmission and uplink transmission process are specifically as follows:
- the base station allocates beams that do not overlap with each other for different user terminals, and uses different beams to send signals to different user terminals.
- the precoding vector of the signal sent by the k-th user terminal is Where e i is a unit vector, the i-th element is 1, and the remaining elements are 0. Since the beams allocated by the base station to different user terminals do not overlap each other, the precoding vectors of different user terminals are orthogonal to each other, that is, In this case, the base station in the first I k th beam, sends a signal to the power p to the k-th user terminal.
- the user terminal selects the beam corresponding to the base station to receive according to the received signal strength, that is, the receiving vector is Where j k represents the fiber transceiver port corresponding to the base station on the k-th user terminal side.
- the base station selects different transmitting beams to send signals from different user terminals, and the user terminal selects the corresponding beam to receive signals from the base station, so the multi-user downlink transmission link can be decomposed into multiple parallel single-user chains road.
- the base station can use baseband modulation (such as OOK modulation) to generate the user's analog baseband transmission signal.
- the user terminal selects the beam corresponding to the base station according to the received signal strength, and uses baseband demodulation (such as OOK demodulation) on the corresponding beam to generate the digital baseband Signal. Therefore, base stations and user terminals may not need to use A/D and D/A devices, which greatly reduces the implementation complexity of ultra-high-speed wireless transmission systems.
- the k-th user terminal uses the j k- th fiber port to send a signal, that is, the precoding vector for uplink transmission is
- the base station according to the received signals, on the second detector I k k-th beam signal receiving user terminal, i.e. the base station detects the received vector of the k th user terminal is Since the beams assigned by the base station to different user terminals do not overlap each other, the base station uses different fiber transceiver ports to receive and detect signals from different user terminals, so the multi-user uplink transmission link can also be decomposed into multiple parallel single-user links.
- Each user terminal uses baseband modulation (such as OOK modulation) to generate an analog baseband signal on the beam corresponding to the base station.
- the base station uses baseband demodulation (such as OOK demodulation) on the beam allocated by each user terminal according to the result of beam allocation. ) Method for demodulation to generate digital baseband signals for each user terminal, which can avoid the use of A/D and D/A devices and reduce the complexity of system implementation.
- Figure 5 shows a schematic diagram of the increase in system throughput with the number of fiber optic transceiver ports in a large-scale scene with an area of 16m ⁇ 16m and a height of 8m (such as a terminal and a gymnasium). There are 300 user terminals in this scene.
- the multi-user MIMO/massive MIMO transmission method (Optimal in the figure) and the performance of beam division multiple access (BDMA) transmission are combined with the maximum ratio transmission (MRT, maximum ratio transmission) and regularized zero-forcing precoding (RZF, regularized zeroforcing) is compared, the precoding vectors of maximum ratio transmission and regularized zero-forcing precoding are respectively
- FIG. 5 (a) is a schematic diagram of downlink transmission performance.
- the optimal design scheme and the performance of beam division multiple access (BDMA) transmission are compared with the maximum ratio combining (MRC, maximal ratio combining).
- the received vector of the maximum ratio combining is
- Figure 5 (b) shows a schematic diagram of uplink transmission performance. It can be seen that as the number of fiber optic transceiver ports increases, the performance of beam division multiple access transmission approaches the optimal transmission, which is better than that of MRC. In addition, when the number of optical fiber transceiver ports is large, the system implementation complexity of beam division multiple access downlink transmission and uplink transmission is very low.
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Abstract
Description
Claims (20)
- 一种光天线,其特征在于:包括光纤收发端口阵列以及透镜或反射镜;在发送信号的过程中,单个光纤收发端口发出的光经过透镜折射或反射镜反射后在某一方向生成具有一定角度范围的光波束,不同光纤收发端口发出的光折射或反射到不同方向;在接收信号的过程中,来自不同方向的接收光线经过透镜折射或反射镜反射后耦合进不同的光纤收发端口进行接收,不同光纤收发端口接收不同方向的光信号。
- 根据权利要求1所述的光天线,其特征在于:所述光天线中的光纤收发端口包括光纤端口和微透镜;在发送信号的过程中,单个光纤端口发出的光信号经过微透镜折射后,生成具有一定角度范围的光波束;在接收信号的过程中,微透镜将一定角度范围内的光信号耦合进光纤端口。
- 根据权利要求1所述的光天线,其特征在于:利用光纤收发端口阵列以及透镜或反射镜生成不同方向的光波束,不同光波束覆盖不同区域,光纤收发端口阵列生成的所有光波束覆盖整个通信区域,实现通信区域全波束覆盖。
- 光纤使能光无线通信FE-OWC装置,其特征在于:包括根据权利要求1所述的光天线以及光收发链路;光天线用于发送和接收不同方向的光信号;光天线与光收发链路通过光纤直接连接,或通过光交换单元连接;光收发链路用于实现光信号与电信号的相互转换;单个FE-OWC装置与单个或一组FE-OWC装置进行无线通信。
- 根据权利要求4所述的FE-OWC装置,其特征在于:所述光收发链路用于实现光信号与电信号的相互转换;在发送信号的过程中,电信号加上偏置电流后驱动激光器,生成与电信号对应的光信号,或采用外调制器方式,将激光源产生的光信号与电信号输入外调制器,生成对应的光信号,光信号经过光放大器放大后通过光纤传输到光天线;在接收信号的过程中,光天线接收的信号通过光纤传输到光收发链路,经过光放大器放大后,利用光探测器检测光信号,转换为对应的电信号。
- 根据权利要求4所述的FE-OWC装置,其特征在于:当光天线与光收发链路直接连接时,每个光收发链路对应一个光纤收发端口,光收发链路个数与光纤收发端口个数相同;当光天线与光收发链路通过光交换单元连接时,光收发链路个数小于等于光纤收发端口个数,光交换单元用于切换光收发链路与光纤收发端口的对应关系,将光收发链路中的信号与光天线生成的波束相对应。
- 根据权利要求4所述的FE-OWC装置,其特征在于:基站侧FE-OWC装置还包括基带信号处理单元,所述基带信号处理单元包含A/D和D/A模块以及数字基带处理与控制模块;下行传输过程中,基站侧的数字基带处理与控制模块用于实现用户调度以及多用户预编码传输,生成每个用户终端的发送信号,D/A模块用于将数字基带处理与控制模块生成的发送信号转化为模拟信号输入光收发链路;上行传输过程中,A/D模块用于将基站侧光收发链路输出的电信号转化为数字信号,数字基带处理与控制模块用于对多用户接收信号进行检测,恢复每个用户终端的发送信号。
- 根据权利要求4所述的FE-OWC装置,其特征在于:用户终端侧FE-OWC装置还包括基带信号处理单元,所述基带信号处理单元包含A/D和D/A模块以及数字基带处理与控制模块;下行传输过程中,A/D模块用于将用户终端侧光收发链路输出的电信号转化为数字信号,数字基带处理与控制模块用于对接收信号进行检测,恢复基站的发送信号;上行传输过程中,用户终端侧的数字基带处理与控制模块用于实现预编码传输,D/A模块用于将生成的发送信号转化为模拟信号输入光收发链路。
- 根据权利要求4所述的FE-OWC装置,其特征在于:基站侧FE-OWC装置还包括基带信号处理单元,所述基带信号处理单元包含基带调制与基带解调模块以及数字基带处理与控制模块;下行传输过程中,基站侧的数字基带处理与控制模块用于为不同用户终端分配互不重叠的波束集合,生成向各用户终端发送的数字基带信号,基带调制模块用于生成向各用 户终端发送的模拟基带信号,传输到对应的光收发链路,利用相应的光纤收发端口进行发送;上行传输过程中,基带解调模块用于将基站侧光收发链路输出的模拟基带接收信号进行解调,生成数字基带信号,数字基带处理与控制模块用于根据波束分配的结果以及每个用户终端对应波束上的数字基带信号恢复各用户终端的发送信号。
- 根据权利要求4所述的FE-OWC装置,其特征在于:用户终端侧FE-OWC装置还包括基带信号处理单元,所述基带信号处理单元包含基带调制与基带解调模块以及数字基带处理与控制模块;下行传输过程中,用户终端侧基带解调模块用于将光收发链路输出的模拟信号进行解调,生成数字基带信号,数字基带处理与控制模块用于挑选基站对应的光纤收发端口,根据其接收数字基带信号恢复基站侧的发送信号;上行传输过程中,用户终端侧的数字基带处理与控制模块用于生成上行数字基带发送信号,基带调制模块用于生成模拟基带发送信号,传输到光收发链路,利用与基站对应的光纤收发端口进行发送。
- 光纤使能光无线通信FE-OWC系统,其特征在于:所述FE-OWC系统的基站和用户终端配置均配置根据权利要求4-6任一项所述的FE-OWC装置;或者基站配置权利要求7所述的FE-OWC装置,用户终端配置根据权利要求8所述的FE-OWC装置;或者基站配置权利要求9所述的FE-OWC装置,用户终端配置根据权利要求10所述的FE-OWC装置。
- 光纤使能光无线通信FE-OWC系统,其特征在于:所述FE-OWC系统的基站配置根据权利要求4-7任一项所述的FE-OWC装置,用户终端配置根据权利要求4-6、8任一项所述的FE-OWC装置,基站与用户终端之间实现多用户MIMO或大规模MIMO光无线通信;或者基站配置根据权利要求4-6、9任一项所述的FE-OWC装置,用户终端配置根据权利要求4-6、10任一项所述的FE-OWC装置,基站与用户终端之间实现波束分多址BDMA光无线通信。
- 光纤使能光无线通信FE-OWC方法,其特征在于:所述通信方法基于根据权利要求12所述的FE-OWC系统,计算单链路传输的链路预算并建立收发端电信号传输信道模型;链路预算包括发送端电光转换、光无线信道增益、接收端光电转换以及接收端电噪声;发送端电光转换部分根据电光转换器件的光电特性,建立发送端输出的光功率与输入电信号之间的对应关系;光无线信道增益为发送端光纤收发端口到接收端光纤收发端口之间的无线信道增益;接收端光电转换部分考虑接收光信号经过光放大器放大以及光探测器检测两个过程,建立接收端输入光信号与输出电信号之间的转换关系;接收端电噪声包括光放大器和光探测器引入的电噪声,建立单个链路接收电信号中信号功率与噪声功率之间的关系;在单个链路预算的基础上,建立完整的从发送端到接收端电信号传输的信道模型;基于该信道模型,基站和用户终端之间实施多用户MIMO或大规模MIMO或波束分多址光无线通信方法。
- 根据权利要求13所述的FE-OWC方法,其特征在于:所述光无线信道增益描述从发送端到接收端光无线传输的信道增益,包括发送端的波束建模、自由空间传输信道增益、接收端光纤收发端口接收功率比率以及光纤端口的耦合效率四个部分;发送端的波束建模描述光纤收发端口发出的光线经过透镜折射或反射镜反射后生成单个波束的光强分布,随着发送端光纤收发端口个数的增加,单个光纤收发端口到不同用户终端的光强渐进正交;自由空间传输信道增益考虑光波束经过自由空间从发送端到接收端的传输过程,其与传输距离的平方成反比;接收端光纤收发端口接收功率比率描述单个光纤收发端口接收的光功率占用户总接收功率的比率,其与接收平面上接收光线投影和光纤收发端口的公共面积成正比;光纤端口的耦合效率为光纤端口处的接收光线能够耦合进入光纤的比率,其与入射光线在光纤端口处的角度范围和光纤端口的接收角的公共区域成正比。
- 光纤使能光无线通信FE-OWC方法,其特征在于:所述通信方法为基于根据权利要求12所述的FE-OWC系统实现的多用户MIMO或大规模MIMO光无线通信方法,具体通信过程包含如下步骤:同步:基站广播下行同步信号,用户终端利用接收信号建立并保持与基站同步;信道探测:用户终端发送上行探测信号,基站根据接收的探测信号估计各用户终端的信道信息;下行传输:基站利用各用户终端的信道信息以及信道的低秩特性进行预编码传输,同时发送所有用户终端的信号,包括导频信号和数据信号,各用户终端根据接收的导频信号估计信道信息,并利用信道信息恢复数据信号;上行传输:用户终端利用预编码传输同时向基站发送信号,包括导频信号和数据信号,基站接收到所有用户终端的信号叠加,根据导频信号估计各用户终端的信道信息,并利用信道的低秩特性进行接收处理,恢复各用户终端的数据信号。
- 根据权利要求13或15所述的FE-OWC方法,其特征在于:下行传输过程中,基站通过上行探测过程估计每个用户终端到基站的上行信道,利用信道的互易性获得下行信道,将信道矩阵分解为列向量与行向量的乘积,并计算各用户终端的接收信干噪比以及可达和速率,在单个光纤收发端口功率约束条件下,以最大化系统和速率为目标设计最优线性预编码;或者基站根据信道矩阵分解的行向量采用最大比发射MRT或正则化迫零RZF预编码方法,利用预编码向量同时发送所有用户终端的信号,包括导频信号和数据信号;上行传输过程中,基站接收到所有用户终端的信号叠加,根据接收的导频信号估计各用户终端的上行信道矩阵,并将其分解为列向量与行向量的乘积,以最大化系统和速率为目标设计最优线性接收机;或者基站根据各用户信道矩阵分解的列向量采用最大比合并MRC接收机,利用线性接收机对接收的数据信号进行检测,恢复各用户终端的发送信号。
- 根据权利要求13或15所述的FE-OWC方法,其特征在于:下行传输过程中,各用户终端根据接收的导频信号估计下行传输信道矩阵,并将其分解为列向量与行向量的乘积,以最大化系统和速率为目标设计最优线性接收机,用户终端利用最优线性接收机对接收的数据信号进行检测;上行传输过程中,各用户终端利用信道的互易性,根据下行信道估计获得上行信道信息,并将信道矩阵分解为列向量与行向量的乘积,在总功率约束的条件下,以最大化系统和速率为目标设计最优预编码向量,用户终端利用预编码向量同时发送上行信号,包括导频信号和数据信号。
- 光纤使能光无线通信FE-OWC方法,其特征在于:所述通信方法为基于根据权利要求12所述的FE-OWC系统实现的波束分多址光无线通信方法,所述波束分多址光无线通信方法为基站根据各用户终端的信道信息为不同的用户终端分配互不重叠的波束,每个波束发送和接收最多一个用户终端的信号,利用不同方向的光波束同时与用户终端双向通信;用户终端根据信道信息挑选基站对应方向的波束,利用单个波束与单个基站进行通信;具体通信过程包含如下步骤:同步:基站广播下行同步信号,用户终端利用接收信号建立并保持与基站同步;信道探测:用户终端发送上行探测信号,基站根据接收的探测信号为每个用户终端分配波束,同一时频资源上与基站通信的用户,所分配的波束互不重叠且每个用户仅分配一个波束;下行传输:基站根据波束分配结果,在每个用户终端分配的波束上发送独立信号,各用户终端根据接收到的信号,挑选与基站对应的波束进行接收检测;上行传输:各用户终端在基站对应的波束上发送信号,基站根据波束分配的结果,在每个用户终端分配的波束上接收检测各用户终端的发送信号。
- 根据权利要求13或18所述的FE-OWC方法,其特征在于:下行传输过程中,基站根据波束分配的结果,在每个用户终端分配的波束上向其发送信号,不同波束发送不同用户终端的信号,多用户下行传输链路分解为多个并行的单用户链路,基站采用基带调制方式生成用户模拟基带发送信号;上行传输过程中,基站根据波束分配的结果,在每个用户终端分配的波束上接收检测该用户终端的发送信号,基站利用不同的波束接收检测不同用户终端的信号,多用户上行传输链路分解为多个并行的单用户链路,基站采用基带解调方式生成各用 户终端的数字基带信号。
- 根据权利要求13或18所述的FE-OWC方法,其特征在于:下行传输过程中,各用户终端根据接收信号的强度,挑选基站对应的波束,在对应的波束上采用基带解调方式生成数字基带信号;上行传输过程中,每个用户终端在基站对应的波束上,采用基带调制方式生成模拟基带信号。
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