WO2009074116A1 - Système de communication sans fil, station centrale, dispositif d'accès et procédé de communication - Google Patents

Système de communication sans fil, station centrale, dispositif d'accès et procédé de communication Download PDF

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Publication number
WO2009074116A1
WO2009074116A1 PCT/CN2008/073474 CN2008073474W WO2009074116A1 WO 2009074116 A1 WO2009074116 A1 WO 2009074116A1 CN 2008073474 W CN2008073474 W CN 2008073474W WO 2009074116 A1 WO2009074116 A1 WO 2009074116A1
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WO
WIPO (PCT)
Prior art keywords
signal
radio frequency
optical
central station
access device
Prior art date
Application number
PCT/CN2008/073474
Other languages
English (en)
French (fr)
Inventor
Yichuan Yu
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to EP08858969A priority Critical patent/EP2221995A4/en
Publication of WO2009074116A1 publication Critical patent/WO2009074116A1/zh
Priority to US12/814,089 priority patent/US20100247105A1/en

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Classifications

    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
    • H04B10/25759—Details of the reception of RF signal or the optical conversion before the optical fibre
    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/085—Access point devices with remote components
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/04—Interfaces between hierarchically different network devices
    • H04W92/12—Interfaces between hierarchically different network devices between access points and access point controllers

Definitions

  • Wireless communication system central station, access device and communication method
  • the present invention relates to wireless communication technologies, and more particularly to wireless communication systems.
  • a base station controller (BSC) 11 controls a plurality of base stations (BS, Base Station) 12, and the base station controller 11 and the base station 12 pass optical fibers or data.
  • BSC base station controller
  • all base stations 12 controlled by the base station controller 11 share control signals of the base station controller 11, and each base station 12 includes a baseband processing section, an intermediate frequency processing section, and a radio frequency processing section.
  • base stations are usually added within a certain range. .
  • the inventors have found that in practice, some areas have complex wireless environments and many buildings, and these buildings have reflection and shielding effects on electromagnetic waves. If base stations are deployed in these areas, the implementation is high. The transmission of quality wireless signals, the coverage of high quality wireless signals, and system networking can be difficult.
  • Embodiments of the present invention provide a wireless communication system, a central station, an access device, and a communication method, which are used to implement high-quality wireless signal transmission, achieve high-quality wireless signal coverage, and implement a simple networking manner.
  • Embodiments of the present invention provide an embodiment of a wireless communication system, including a central station (CS, Central Station) having a base station controller function, and at least one access device controlled by the central station, the central station and access The devices are connected by a wired connection; the access device is configured to demodulate the wired signal sent by the central station into a radio frequency signal, transmit the radio frequency signal to the destination wireless user, and modulate the uplink radio frequency signal sent by the wireless user.
  • CS Central Station
  • the access device is configured to demodulate the wired signal sent by the central station into a radio frequency signal, transmit the radio frequency signal to the destination wireless user, and modulate the uplink radio frequency signal sent by the wireless user.
  • the central station is configured to perform baseband processing, intermediate frequency processing, and radio frequency processing on data provided by the core network, obtain a radio frequency signal, modulate the radio frequency signal into a wired signal, and then send the wired signal to the
  • the purpose of the data corresponds to the wireless user
  • the access device demodulates the wired signal sent by the access device into a radio frequency signal, performs radio frequency processing, intermediate frequency processing, and baseband processing on the radio frequency signal, obtains data sent by the wireless user, and provides the data to the Core Network.
  • An embodiment of the present invention provides a central station, including a modem unit, a baseband processing unit, an intermediate frequency processing unit, and a radio frequency processing unit.
  • the baseband processing unit is configured to convert data provided by a core network into a baseband signal, and the intermediate frequency processing
  • the unit is configured to convert the baseband signal into an intermediate frequency signal
  • the radio frequency processing unit is configured to convert the intermediate frequency signal into a radio frequency signal
  • the modem unit is configured to modulate the radio frequency signal into a wired signal; Demodulating the wired signal into a radio frequency signal
  • the radio frequency processing unit is configured to convert the radio frequency signal into an intermediate frequency signal
  • the intermediate frequency processing unit is configured to convert the intermediate frequency signal into a baseband signal
  • the baseband processing unit is configured to convert the baseband signal into To provide data to the core network.
  • An embodiment of the present invention provides an access device, including: a modem unit, configured to modulate a radio frequency signal provided by a wireless user into a wired signal, and demodulate the obtained wired signal into a radio frequency signal sent to a wireless user.
  • An embodiment of the present invention provides a communication method, including: receiving, by a central station, data provided by a core network, and converting the data into a wired signal; and transmitting, by the central station, a wired signal to a destination wireless user of the data by using a wired transmission medium Access device; the access device demodulates the wired signal into a radio frequency signal, and transmits the radio frequency signal to the destination wireless user.
  • the embodiment of the present invention further provides a communication method, including the following steps: the access device obtains a radio frequency signal provided by a wireless user, and modulates the radio frequency signal into a wired signal; the access device sends the wired signal to the central station by using a wired transmission medium; After the central station converts the wired signal into data provided to the core network, the data is provided to the core network.
  • the functions of the conventional base station controller and the main functions of the baseband processing, the intermediate frequency processing, and the radio frequency processing of the base station are all set in the central station, and one central station can utilize the function control of the traditional base station controller it has.
  • a plurality of access devices with signal conversion functions enable transparent transmission of data at different rates and formats, thereby realizing dynamic management and optimal allocation of network and frequency resources. It can be seen that when the network of the embodiment of the present invention is applied, it is not necessary to deploy multiple base station controllers and base stations in certain areas, and only one central station and several access devices controlled by the central station need to be deployed.
  • the networking mode is simple and cost-effective compared to the current networking mode.
  • the access device does not have the functions of baseband processing, intermediate frequency processing, and radio frequency processing of the conventional base station, and the device is relatively small, it is easy to be deployed in an indoor or outdoor area where the conventional base station is inconvenient to deploy, thereby improving the coverage of the signal.
  • the access device does not have the functions of baseband processing, intermediate frequency processing, and radio frequency processing of the conventional base station, it is easy to deploy in an area closer to the wireless user, and since the access device and the central station are wired, the signal Most of them are wired, which avoids the shielding or reflection of electromagnetic waves in buildings and improves the quality of signal transmission.
  • FIG. 1 is a schematic structural diagram of a conventional wireless communication system
  • FIG. 2 is a schematic structural diagram of a wireless communication system according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a first embodiment of a wireless communication system according to an embodiment of the present invention
  • FIG. 4 is a schematic structural diagram of a second embodiment of a wireless communication system according to an embodiment of the present invention
  • FIG. 6 is a schematic structural diagram of a fourth embodiment of a wireless communication system according to an embodiment of the present invention
  • FIG. 7 is a flowchart of a communication method according to an embodiment of the present invention.
  • FIG. 8 is a flowchart of a communication method according to an embodiment of the present invention.
  • a wireless communication system embodiment may include a central station having a base station controller function and at least one access device controlled by the central station, the central station performing unified resource scheduling on the access device, between the central station and the access device ⁇ Connected by wire; the access device is used to demodulate the wired signal sent by the central station into a radio frequency signal, send the radio frequency signal to the destination wireless user, and modulate the uplink RF signal sent by the wireless user into a wired signal and send it to the central station.
  • the central station is configured to perform baseband processing, intermediate frequency processing, and radio frequency processing on the data provided by the core network, obtain a radio frequency signal, modulate the radio frequency signal into a wired signal, and then send the wired signal to the access device corresponding to the destination wireless user of the data,
  • the cable signal sent by the access device is demodulated into a radio frequency signal, and the radio frequency signal is subjected to radio frequency processing, intermediate frequency processing, and baseband processing to obtain data sent by the wireless user, and then the data is provided to the core network.
  • the wireless subscriber referred to in the embodiments of the present invention may refer to a wireless subscriber terminal.
  • the central station and the access device are connected by optical fibers, so that the central station and the access device
  • the optical signal transmitted between the optical links is the optical signal.
  • the central station can perform unified resource scheduling on the access device, or a plurality of access devices can share one central station, and one central station performs centralized control.
  • the central station is able to grasp the air interface resources of all access devices under its control. For example, if the coverage of the three access devices under the control of a central station is partially overlapped, the air interface resource usage of one of the access devices is relatively large. To alleviate the pressure on the air interface resources of the access device, the central station may overlap. Some wireless users in the coverage communicating with this access device are adjusted to the other two access devices, that is, some wireless users communicate with the other two access devices.
  • the central station can perform unified resource scheduling on the access device, and other implementation manners can be used.
  • the central station may include an optical modulator for modulating the radio frequency signals obtained by the baseband processing, the intermediate frequency processing, and the radio frequency processing into optical signals transmitted to the access device, and the access device may also include an optical modulator for the wireless user.
  • the transmitted RF signal is modulated into an optical signal that is sent to the central station.
  • the light modulator may include an EOM (Electro-Optic Modulator) or a Direct Modulated Laser (LD, Laser Diode).
  • the optical modulator may be a lithium niobate electro-optic modulator or an Electro-Absorption Modulator (EAM) (hereinafter referred to as an electroabsorption optical modulator), and the direct modulation laser may be a direct modulation semiconductor laser.
  • EAM Electro-Absorption Modulator
  • the light modulator can be an electro-absorption optical transceiver that has both signal modulation and signal demodulation functions. If the optical modulator of the central station is an electrically absorbing optical transceiver, the electrically absorbing optical transceiver can also demodulate the optical signal emitted by the access device into a radio frequency signal in the central station. If the optical modulator of the access device is an electrically absorbing optical transceiver, the electrically absorbing optical transceiver demodulates the optical signal emitted by the central station into a radio frequency signal in the access device.
  • the optical carrier used to modulate the downlink RF signal into an optical signal is different from the optical carrier used to modulate the upstream RF signal into an optical signal, and specifically may be issued by one multi-wavelength laser or two single-wavelength lasers. Different optical carrier implementations. It should be understood that the optical carriers used in the downlink and uplink may also be the same, and may be implemented by a multi-wavelength laser or a single-wavelength laser to emit an optical carrier.
  • An optical amplifier may be included in the central station and/or the downstream fiber link for amplifying the downstream optical signal.
  • An optical amplifier may also be included in the access device and/or the upstream fiber link for uplinking
  • a dispersion compensation device for performing dispersion compensation on an optical signal.
  • the wireless communication system of the embodiment of the present invention includes a central station 21 and a plurality of base stations 22 controlled thereby, and the base station herein is an access device, and the following embodiments are the same.
  • the central station 21 and the multi-network are mainly composed of optical fibers, so it can be said that the central station 21 and the plurality of base stations 22 are connected by optical fibers.
  • the central station 21 also has the functions of baseband processing, intermediate frequency processing and radio frequency processing of the conventional base station, and the base station 22 is substantially not a base station of the conventional meaning, and its main function is the radio frequency signal and the optical signal. Inter-conversion and antenna feeding and reception of radio frequency signals.
  • the central station 21 After obtaining the data provided by the core network, the central station 21 performs baseband processing, intermediate frequency processing, and radio frequency processing to obtain a radio frequency signal, and modulates the radio frequency signal onto the optical carrier to form an optical signal, and the optical signal passes through the optical fiber (also That is, the optical fiber feeding network transmits the data to the base station 22 corresponding to the customer unit (Customer Units) 23, and the base station 22 demodulates the optical signal to obtain a radio frequency signal, and finally transmits the radio frequency signal to the destination subscriber unit 23.
  • the optical fiber feeding network transmits the data to the base station 22 corresponding to the customer unit (Customer Units) 23, and the base station 22 demodulates the optical signal to obtain a radio frequency signal, and finally transmits the radio frequency signal to the destination subscriber unit 23.
  • the source subscriber unit 23 transmits a radio frequency signal to the corresponding base station 22, and the base station 22 modulates the radio frequency signal onto the optical carrier to form an optical signal, and the optical signal is transmitted to the central station 21 via the optical fiber, and the central station 21 solves the optical signal.
  • the radio frequency signal is obtained, and the radio frequency signal is subjected to radio frequency processing, intermediate frequency processing and baseband processing to obtain data transmitted to the core network, and finally the data is sent to the core network.
  • the central station 21 and the base station 22 can perform the conversion of the radio frequency signal to the optical signal using an optical external modulator or a direct modulation semiconductor laser, respectively.
  • the optical modulator can be a lithium niobate electro-optic modulator or a semiconductor electro-absorption optical modulator with high -3dB bandwidth, high electro-optic conversion efficiency, adjustable ⁇ characteristics and nonlinear control, which is suitable for high bandwidth and high performance.
  • Wireless communication system is Among them, the semiconductor electroabsorption modulator has the advantages of low power consumption, high extinction ratio, small device size, and the like, and since the semiconductor electroabsorption modulator uses the III-V semiconductor material, a small-volume semiconductor electroabsorption modulator can be realized.
  • the central station 21 and the base station 22 can perform conversion of the optical signal to the radio frequency signal using a photodetector (PD, Photo-Detector), respectively.
  • the central station and the base station can each have various forms of internal structure, and FIG. 3 is one of them.
  • the central station 31 includes an optical external modulator 311, a laser 312, a photodetector 313, a radio frequency mixer 314, a radio frequency mixer 314', a radio frequency local oscillator 315, an intermediate frequency mixer 316, and an intermediate frequency.
  • the wireless modem 318 For downlink information, after the data provided by the core network 33 arrives at the wireless modem 318, the wireless modem 318 performs baseband processing on the data to obtain a baseband signal, and transmits the baseband signal to the intermediate frequency mixer 316; the intermediate frequency mixer 316 baseband the signal and The signal generated by the intermediate frequency signal generator 317 is processed to obtain an intermediate frequency signal, and the intermediate frequency signal is sent to the RF mixer 314.
  • the RF mixer 314 processes the intermediate frequency signal and the RF signal generated by the RF local oscillator 315 to obtain an RF.
  • the signal, and the radio frequency signal is sent to the optical modulator 311; the optical modulator 311 modulates the radio frequency signal onto the optical carrier emitted by the laser 312 to form an optical signal, which is passed through the optical fiber (that is, the downlink in FIG. 3).
  • the optical signal is sent to the base station 32.
  • the photodetector 313 receives the optical signal sent by the base station 32 through the optical fiber (that is, the uplink in FIG. 3), demodulates the optical signal, obtains the radio frequency signal, and transmits the radio frequency signal to the radio frequency mixture.
  • the frequency converter 314' processes the RF signal and the signal generated by the RF local oscillator 315 to obtain an intermediate frequency signal, and sends the intermediate frequency signal to the intermediate frequency mixer 316'; the intermediate frequency mixer 316,
  • the signals generated by the intermediate frequency signal and the intermediate frequency signal generator 317 are processed to obtain a baseband signal, and the baseband signal is transmitted to the wireless modem 318; the wireless modem 318 processes the baseband signal to obtain data transmitted to the core network 33, and transmits the data. Give the core network 33.
  • the base station 32 includes an optical external modulator 321, a laser 322, a photodetector 323, an amplification filtering unit 324, and an amplification filtering unit 324'.
  • the photodetector 323 demodulates the optical signal to obtain a radio frequency signal, and the radio frequency signal is amplified and filtered by the amplification filtering unit 324, and then transmitted to the destination subscriber unit through the antenna.
  • the RF signal After receiving the RF signal, the RF signal is amplified by the amplification filtering unit 324', and reaches the optical modulator 321.
  • the optical modulator 321 modulates the amplified RF signal to the optical carrier of the laser 322. Above, an optical signal is formed, and the optical signal is transmitted to the central station 31.
  • the base station 32 Since the central station 31 needs to modulate the downlink radio frequency signal into the optical carrier, the base station 32 needs to uplink.
  • the radio frequency signal is modulated into the optical carrier, so in Figure 3, the central station 31 and the base station 32 are each provided with a laser for emitting an optical carrier.
  • a multi-wavelength laser or two single-wavelength lasers may be provided only at the central station 31 or only at the base station 32.
  • the multi-wavelength laser or two single-wavelength lasers may emit two different optical carriers, one of which is light.
  • the carrier is used to carry the RF signal, and the other optical carrier does not carry any RF signal. Instead, it directly carries the RF signal sent by the other party to the local photodetector after directly reaching the optical modulator of the other party.
  • information can be transmitted by two different optical carriers that are provided by one multi-wavelength laser or two single-wavelength lasers of the central station 31 or the base station 32.
  • the central station 41 includes an electro-absorption optical modulator 411, a laser 412, a laser 412', a photodetector 413, a radio frequency mixer 414, a radio frequency mixer 414', and a radio frequency local oscillator 415.
  • the amplification filtering unit 419 and the amplification filtering unit 419' of course, the central station 41 further includes an intermediate frequency processing and a baseband processing portion. Since the intermediate frequency processing and the baseband processing are not described in detail in this embodiment, they are not shown in the figure.
  • the base station 42 includes an electro-absorption optical modulator 421, a photodetector 423, an amplification filtering unit 424, and an amplification filtering unit 424'.
  • the solid line with an arrow in the figure indicates the path through which the optical signal passes
  • the dotted line with an arrow indicates the path through which the electrical signal passes.
  • the radio frequency signal generated by the mixing by the RF mixer 414 is subjected to the amplification filtering process of the amplification filtering unit 419, and then reaches the electro-absorption optical modulator 411.
  • the electro-absorption optical modulator 411 modulates the radio frequency signal to the laser 412.
  • On the optical carrier ⁇ an optical signal is formed, and the optical signal is transmitted to the base station 42 through the optical fiber (that is, the downlink in FIG. 4); the laser 412' emits the optical carrier ⁇ 2, and the optical carrier ⁇ 2 does not pass through the electric absorption light modulator 411.
  • the optical carrier ⁇ and the optical carrier ⁇ 2 arrive at the base station 42 and are separated from each other.
  • the optical carrier ⁇ is transmitted to the photodetector 423, and the optical carrier ⁇ 2 is transmitted to the electro-absorption optical modulator 421.
  • the photodetector 423 After receiving the optical signal, the optical signal is demodulated to obtain a radio frequency signal, and the radio frequency signal is amplified and filtered by the amplification filtering unit 424, and then transmitted to the destination subscriber unit through the antenna.
  • the RF signal is received by the antenna, it is amplified and filtered by the amplification filtering unit 424', and then reaches the electro-absorption optical modulator 421 (a type of the optical modulator), and the electro-absorption optical modulator 421 is subjected to amplification filtering.
  • the processed RF signal is modulated onto the optical carrier ⁇ 2 to form an optical signal, and the optical signal is transmitted to the central station 41 through the optical fiber (that is, the uplink in FIG. 4); the photodetector 413 of the central station 41 performs the optical signal.
  • Demodulation, get RF signal, RF signal is amplified
  • the RF mixer 414 is reached. The subsequent process is the same as the corresponding description of the embodiment shown in FIG. 3, and details are not described herein again.
  • the transmission distance of the RF signal in the fiber is mainly limited by the energy loss of the RF signal during the fiber transmission, the carrier suppression effect caused by the fiber dispersion, and the distortion caused by the nonlinear effect of the fiber.
  • an optical amplifier can be provided to increase the gain of the radio frequency signal, and a fiber Bragg grating (FBG, Fiber Bragg Grating) can be disposed on the fiber link between the central station 41 and the base station 42 in FIG.
  • FBG Fiber Bragg Grating
  • FIG. 4 although two lasers 412, 412 are disposed in the central station 41, in practice, only one multi-wavelength laser may be disposed in the central station 41. It should be understood that It is also possible to arrange two lasers or a multi-wavelength laser in the base station 42. The operation of the laser in the base station 42 is exactly the same as that in the central station 41, and will not be described again here.
  • an electric absorption light modulator is used to modulate the radio frequency signal onto the optical carrier, and a photodetector is used to demodulate the optical signal.
  • the signal can be modulated and demodulated using a special electro-absorption optical transceiver (EAT, Electro-Absorption Transceiver), since the electro-absorption optical transceiver has both modulation and solution.
  • EAT Electro-Absorption Transceiver
  • the function is adjusted, so that the electroabsorption optical modulator and the photodetector of Fig. 4 can be replaced at the same time by using the electro-absorption optical transceiver, so that the structure of the central station 41 and/or the base station 42 in Fig. 4 can be simplified.
  • the central station 51 includes an electro-absorption optical modulator 511, a laser 512, a laser 512', a photodetector 513, a radio frequency mixer 514, a radio frequency mixer 514', and a radio frequency local oscillator 515.
  • the central station 51 further includes an intermediate frequency processing and a baseband processing portion. Since the intermediate frequency processing and the baseband processing are not emphasized in this embodiment, the figure is not depicted. Show.
  • the base station 52 includes an electro-absorption optical transceiver 521, a radio frequency amplifier 524, a radio frequency amplifier 524, a band pass filter 526, and an optical amplifier 527.
  • the solid line with an arrow in the figure indicates the path through which the optical signal passes
  • the dotted line with an arrow indicates the path through which the electrical signal passes.
  • the radio frequency signal generated by the mixing of the RF mixer 514 is sent to the electro-absorption optical modulator 511; the electro-absorption optical modulator 511 modulates the downlink radio frequency signal onto the optical carrier ⁇ emitted by the laser 512 to form an optical signal. And pass the optical signal through the fiber (that is, the downlink in Figure 5)
  • the optical signal is sent to the base station 52, wherein the optical signal is subjected to amplification processing by the optical amplifier 517 during transmission; the laser 512' emits the optical carrier ⁇ 2, and the optical carrier ⁇ 2 does not pass through the electric absorption light modulator 511, but directly reaches the base station 52 through the optical fiber.
  • the electrical absorption optical transceiver 521 in the base station 52 demodulates the downlink radio frequency signal carried by the optical carrier ⁇ to obtain a radio frequency signal, and the radio frequency signal is filtered by the band pass filter 526. After being amplified by the amplifier 524, it is transmitted to the destination subscriber unit through the antenna; after the optical carrier ⁇ 2 reaches the electrical absorption optical transceiver 521, it is used for transmission of uplink information.
  • the radio frequency signal is received by the antenna, it is amplified and filtered by the amplifier 524', and reaches the electric absorption optical transceiver 521.
  • the electric absorption optical transceiver 521 modulates the radio frequency signal subjected to the amplification and filtering processing onto the optical carrier ⁇ 2 to form
  • the optical signal is transmitted to the central station 51 through the optical fiber (i.e., the uplink in FIG.
  • the optical signal is amplified by the optical amplifier 527 during transmission; the photodetector 513 of the central station 51
  • the optical signal is demodulated to obtain a radio frequency signal, and the radio frequency signal is subjected to filtering processing by the band pass filter 516 and amplification processing by the radio frequency amplifier 519, and then reaches the radio frequency mixer 514'.
  • the subsequent process is the same as the corresponding description of the embodiment shown in FIG. 3, and details are not described herein again.
  • the electro-absorption optical transceiver is disposed in the base station 52, in practical applications, the electro-absorption optical transceiver can be completely disposed in the central station 51.
  • the central station 51 and the base station 52 can also be provided with an electro-absorption optical transceiver.
  • the operation of the electro-absorption optical transceiver in the central station 51 is exactly the same as that in the base station 52, and will not be described herein.
  • uplink information and downlink information are respectively transmitted on optical carriers of different wavelengths.
  • uplink information and downlink information may also be transmitted on the same optical carrier, thereby improving optical carrier resources. Use efficiency to increase system capacity.
  • the central station 61 includes an electro-absorption optical modulator 611, a laser 612, a photodetector 613, a radio frequency mixer 614, a radio frequency mixer 614', a radio frequency local oscillator 615, and band pass filtering.
  • the 616, the optical amplifier 617 and the radio frequency amplifier 619 of course, the central station 61 further includes an intermediate frequency processing and a baseband processing portion. Since the intermediate frequency processing and the baseband processing are not described in detail in this embodiment, they are not shown.
  • Base station 62 includes an electrically absorbing optical transceiver 621, a radio frequency amplifier 624, a radio frequency amplifier 624, a bandpass filter 626, and an optical amplifier 627.
  • the radio frequency signal generated by the mixing of the RF mixer 614 is sent to the electro-absorption optical modulator 611; the electro-absorption optical modulator 611 modulates the radio frequency signal onto the optical carrier ⁇ emitted by the laser 612 to form an optical signal, and The optical signal is transmitted to the base station 62 through the optical fiber (that is, the downlink in FIG.
  • the optical signal is subjected to amplification processing by the optical amplifier 617 during transmission; after the optical carrier ⁇ arrives at the base station 62, the base station 62
  • the electro-absorption optical transceiver 621 demodulates the optical signal to obtain a radio frequency signal.
  • the radio frequency signal is filtered by the bandpass filter 626 and amplified by the radio frequency amplifier 624, and then transmitted to the destination subscriber unit through the antenna.
  • the radio frequency signal After receiving the radio frequency signal, the radio frequency signal is amplified by the radio frequency amplifier 624', and reaches the electric absorption optical transceiver 621.
  • the electric absorption optical transceiver 621 modulates the amplified radio frequency signal onto the optical carrier ⁇ to form an optical signal. And transmitting the optical signal to the central station 61 through the optical fiber (that is, the uplink in FIG.
  • the optical signal is amplified by the optical amplifier 627 during transmission; the photodetector 613 of the central station 61 is facing the light
  • the signal is demodulated to obtain a radio frequency signal, and the radio frequency signal is subjected to filtering processing by the band pass filter 616 and amplification processing by the radio frequency amplifier 619 to the radio frequency mixer 614'.
  • the subsequent process is the same as the corresponding description of the embodiment shown in FIG. 3, and will not be described again here.
  • the laser is disposed in the central station 61, in practical applications, the laser may be disposed only in the base station 62, and the working mode of the laser in the base station 62 is in the central station 61. The way of working is the same, so I won't go into details here.
  • the embodiment of the present invention provides two communication methods, and both communication methods can be applied to a wireless communication system including a central station and at least one access device controlled by the central station, the central station A wired connection with at least one access device, the access device communicating with the wireless user via the radio frequency signal.
  • S701 The central station obtains data provided by the core network, and converts the data into a wired signal;
  • S702 the central station sends the wired signal to the access device corresponding to the destination wireless user of the data by using a wired transmission medium;
  • the access device demodulates the wired signal into a radio frequency signal, and sends the radio frequency signal to the destination wireless user.
  • the wired signal may be an optical signal
  • the wired transmission medium may be an optical fiber.
  • Figure 8 Another communication method is shown in Figure 8, which includes the following steps:
  • the access device obtains a radio frequency signal provided by a wireless user, and modulates the radio frequency signal into a wired signal;
  • the access device sends the wired signal to the central station by using a wired transmission medium
  • the central station provides the data to the core network after converting the wired signal into data provided to the core network.
  • the wired signal may be an optical signal
  • the wired transmission medium may be an optical fiber
  • the embodiment of the present invention further provides a central station, which includes a modem unit, a baseband processing unit, an intermediate frequency processing unit, and a radio frequency processing unit.
  • the baseband processing unit is configured to convert data provided by the core network into a baseband signal.
  • the intermediate frequency processing unit is configured to convert the baseband signal into an intermediate frequency signal
  • the radio frequency processing unit is configured to convert the intermediate frequency signal into a radio frequency signal
  • the modem unit is configured to modulate the radio frequency signal into a wired signal
  • the modem unit is further configured to use the wired signal Demodulated into a radio frequency signal
  • the radio frequency processing unit is further configured to convert the radio frequency signal into an intermediate frequency signal
  • the intermediate frequency processing unit is further configured to convert the intermediate frequency signal into a baseband signal
  • the baseband processing unit is further configured to convert the baseband signal into a core network. data.
  • the wired signal can be an optical signal.
  • the modem unit may include an optical modulator and a photodetector; the optical modulator is configured to modulate the radio frequency signal obtained by the radio frequency processing unit into an optical signal, and the photodetector is configured to demodulate the optical signal into a radio frequency signal transmitted to the radio frequency processing unit.
  • the light modulator can include an optical modulator or a direct modulation laser.
  • the optical external modulator can be a lithium niobate electro-optic modulator or a semiconductor electro-absorption optical modulator.
  • the modem unit can also be an electrically absorbing optical transceiver.
  • the central station may also include a laser for generating an optical carrier.
  • the central station may further include an amplification filtering unit for performing amplification filtering processing on the modulated radio frequency signal and/or the radio frequency signal before demodulation.
  • the amplification filter unit may include an amplifier and a band pass filter.
  • the central station can also have other structural forms. For details, refer to the structure of the central station and the corresponding description shown in Figure 3-6, and details are not described herein.
  • An embodiment of the present invention further provides an access device (hereinafter, the base station is taken as an example), including: a modem unit, configured to modulate a radio frequency signal provided by a wireless user into a wired signal, and demodulate the obtained wired signal. A radio frequency signal that is sent to a wireless user.
  • an access device hereinafter, the base station is taken as an example
  • a modem unit configured to modulate a radio frequency signal provided by a wireless user into a wired signal, and demodulate the obtained wired signal.
  • a radio frequency signal that is sent to a wireless user.
  • the wired signal can be an optical signal.
  • the modem unit may include a light modulator and photodetection A light modulator is used to modulate a radio frequency signal provided by a wireless user into an optical signal, and the photodetector is used to demodulate the optical signal into a radio frequency signal transmitted to a wireless user.
  • the modem unit can be an electrically absorbing optical transceiver.
  • the base station may also include a laser for generating an optical carrier.
  • the base station may further include an amplification filtering unit configured to perform amplification filtering processing on the modulated radio frequency signal and/or the pre-demodulation radio frequency signal.
  • the amplification filtering unit may include an amplifier and a band pass filter.
  • the optical carrier wavelength and optical power of the laser output can be adjusted; if the linearity of the optical modulator transfer function needs to be optimized, the optical modulator can be adjusted.
  • Working conditions If you need to optimize the demodulation results of the photodetector, you can adjust the working conditions of the photodetector to optimize the detection rate.
  • the access device mainly has the functions of electro-optical and/or photoelectric conversion, has a simple structure, and has low power consumption, so the deployment cost is relatively low, so that it can be conveniently deployed in most Areas, especially in broadband wireless communication systems, are inconvenient to deploy areas of conventional base stations, such as indoors, due to cost, power, and the like.
  • the access device and the central station are connected by wire, and the access device can be closer to the wireless user, the loss of the signal in the transmission process is relatively small, thereby improving Signal quality and transmission distance.
  • a plurality of compact access devices share the resources of the central station and are centrally controlled by the central station, so that transparent transmission of data of different rates and different formats can be realized, and the network and Dynamic management and optimized allocation of frequency resources is also easy for network upgrades, reducing installation and maintenance costs.
  • multiplexing/demultiplexing techniques can be used to increase the amount of information that a wireless communication system can support, since signals can be multiplexed and decomposed.
  • the electro-absorption optical transceiver is used to perform modulation and demodulation between the optical signal and the electrical signal, and the optical carrier transmitted by one laser is used for signal modulation, the structure of the central station and the access device can be simplified, and the structure can be further reduced. Deployment costs.
  • an amplifier is used on the fiber link, the gain of the signal, the transmission distance and quality of the signal can be further improved; if the compensation of the signal is compensated by using the dispersion compensation device, the transmission distance and quality of the signal can be further improved.
  • an optical signal is modulated by an optical modulator such as a lithium niobate electro-optic modulator or a semiconductor electro-absorption optical modulator, due to the advantages of high electro-optical conversion efficiency, ⁇ characteristics, and nonlinear control of these devices, The overall performance of the wireless communication system can be further improved.
  • Embodiments of the present invention are fully applicable to future Pico-cell structures or Femto-cell structures.
  • the base station with simple structure and easy deployment is used as an access device in the embodiment of the present invention, it is easy to deploy a large number of access devices in the city, thereby realizing a small coverage area cellular structure, and also because the access device and the central station
  • the use of wired connections between them greatly reduces the impact of multipath fading on the system and inter-symbol interference caused by multipath effects. Therefore, embodiments of the present invention are fully applicable to future picocellular structures or picocellular structures.
  • Embodiments of the present invention fully meet the requirements of Millimeter-wave wireless communication.
  • first- and second-generation mobile communication systems are only tens of Kb/s to several hundred Kb/s, and the transmission of third-generation mobile communication systems (3G) based on code division multiple access (CDMA) technology The rate is also only on the order of Mbit/s.
  • third-generation mobile communication systems 3G
  • CDMA code division multiple access
  • the fourth generation mobile communication system utilizes a new wireless transmission technology, supporting the order of magnitude at 100Mb/s and even
  • the information transmission rate above Gb/s such an ultra-wideband wireless communication system can simultaneously support telephone services, massive data services, and broadband multimedia services represented by high-definition television, etc., which can fully satisfy the future mobile broadband access. demand.
  • the 7 GHz spectrum bandwidth in the millimeter band is an unlicensed spectrum resource.
  • the spectrum ranges from 57-64 GHz, while in Japan it is 59-66 GHz.
  • the millimeter wave integration technology with a working frequency of 94 GHz has been successfully applied in special fields such as all-weather defense, high-resolution millimeter wave passive imaging, and precise positioning in national defense.
  • the millimeter wave band such as 60 GHz is not the transmission window of electromagnetic waves in the atmosphere, its application prospects in short-range wireless communication are unquestionable, including high-speed Gb/s point-to-point data transmission, ultra-large-capacity wireless local area networks, and individuals. Short-distance high-speed data transmission network, millimeter-wave vehicle anti-collision radar and so on.
  • researchers in all countries of the world regard wireless communication based on the millimeter wave band as an important research direction for future wireless communication.
  • millimeter wave communication technology also has a drawback, that is, a millimeter wave signal has considerable loss due to absorption and reflection when it propagates in the atmosphere.
  • the embodiment of the present invention uses a base station with a simple structure and easy deployment as an access device, and a wired connection between the access device and the central station, the millimeter wave signal is greatly reduced in the atmosphere. Time loss, even if the access device is deployed properly, can even achieve near zero loss. Therefore, the embodiment of the present invention can be applied to millimeter wave wireless communication, which fully satisfies the requirements of the future millimeter wave wireless communication technology.
  • the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

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Description

无线通信系统、 中心站、 接入设备及通信方法
本申请要求于 2007 年 12 月 12 日提交中国专利局、 申请号为 200710198769.9、 发明名称为"无线通信系统、 中心站、 接入设备及通信方法" 的中国专利申请的优先权， 其全部内容通过引用结合在本申请中。
技术领域
本发明涉及无线通信技术， 尤其涉及无线通信系统。
背景技术
目前的无线通信系统的结构如图 1 所示， 一个基站控制器 （BSC, Base Station Controller ) 11控制多个基站 （BS, Base Station ) 12, 基站控制器 11 与基站 12之间通过光纤或数据线连接， 受基站控制器 11控制的所有的基站 12共享基站控制器 11的控制信号， 每个基站 12都包括基带处理部分、 中频 处理部分以及射频处理部分。
由于无线通信的数据传输速率不断提高，同时需求无线通信服务的用户越 来越多， 地域范围越来越广， 所以， 为增加无线信号的覆盖质量和覆盖范围， 通常都会在一定范围内增加基站。但发明人在实现本发明的过程中发现，在实 际中， 有些地区的无线环境复杂、 建筑物较多， 而这些建筑物对电磁波具有反 射和屏蔽作用，如果在这些地区部署基站，那么实现高质量的无线信号的传输、 实现高质量的无线信号的覆盖范围以及系统组网都会很困难。
发明内容
本发明实施例提供了一种无线通信系统、 中心站、 接入设备及通信方法， 用以实现高质量的无线信号的传输、实现高质量的无线信号的覆盖范围以及实 现简约的组网方式。
本发明实施例提供一种无线通信系统实施例，包括一个具有基站控制器功 能的中心站（CS, Central Station )和受所述中心站控制的至少一个接入设备， 所述中心站和接入设备之间釆用有线方式连接；所述接入设备用于将所述中心 站发出的有线信号解调为射频信号，将射频信号发送给目的无线用户， 并将无 线用户发出的上行射频信号调制为有线信号发送给所述中心站；所述中心站用 于对核心网提供的数据进行基带处理、中频处理以及射频处理，得到射频信号， 将射频信号调制为有线信号，再将有线信号发送给数据的目的无线用户对应的 所述接入设备， 并将所述接入设备发出的有线信号解调为射频信号，对射频信 号进行射频处理、 中频处理以及基带处理， 得到无线用户发送的数据， 再将所 述数据提供给核心网。
本发明实施例提供一种中心站， 包括调制解调单元、基带处理单元、 中频 处理单元以及射频处理单元；所述基带处理单元用于将核心网提供的数据转换 为基带信号， 所述中频处理单元用于将基带信号转换为中频信号， 所述射频处 理单元用于将中频信号转换为射频信号，所述调制解调单元用于将射频信号调 制为有线信号； 所述调制解调单元用于将有线信号解调为射频信号， 所述射频 处理单元用于将射频信号转换为中频信号，所述中频处理单元用于将中频信号 转换为基带信号，所述基带处理单元用于将基带信号转换为提供给核心网的数 据。
本发明实施例提供一种接入设备， 包括： 调制解调单元， 用于将无线用户 提供的射频信号调制为有线信号，并将获得的有线信号解调为发送给无线用户 的射频信号。
本发明实施例提供一种通信方法， 包括： 中心站获得核心网提供的数据， 并将所述数据转换为有线信号；中心站通过有线传输介质将有线信号发送给所 述数据的目的无线用户对应的接入设备；所述接入设备将有线信号解调为射频 信号， 并将射频信号发送给所述目的无线用户。
本发明实施例还提供一种通信方法， 包括以下步骤： 接入设备获得无线用 户提供的射频信号， 并将射频信号调制为有线信号； 接入设备通过有线传输介 质将有线信号发送给中心站； 中心站将有线信号转换为提供给核心网的数据 后， 将数据提供给核心网。
在本发明的实施例中，传统基站控制器的功能以及基站的基带处理、 中频 处理和射频处理等主要功能都设置在中心站中，一个中心站可以利用其具有的 传统基站控制器的功能控制多个具有信号转换功能的接入设备，实现对不同速 率、不同格式的数据透明传输，实现对网络和频率资源的动态管理和优化分配。 由此可见， 在应用本发明的实施例组网时， 可以不必在某些区域部署多个基站 控制器和基站， 只需要部署一个中心站和其控制的几个接入设备即可， 这样的 组网方式相对于目前的组网方式简单且节约成本。 由于接入设备不具有传统基站的基带处理、 中频处理以及射频处理等功 能， 器件相对较少， 所以很容易部署在室内或室外中传统基站不方便部署的区 域， 从而提高了信号覆盖的范围。
由于接入设备不具有传统基站的基带处理、 中频处理以及射频处理等功 能， 所以很容易部署在离无线用户较近的区域， 又由于接入设备与中心站之间 是有线连接的， 所以信号大部分都是有线传输的，避免了建筑物对电磁波的屏 蔽或反射， 提高了信号传输的质量。
附图说明
图 1为现有的无线通信系统的结构示意图；
图 2为本发明实施例的无线通信系统的结构示意图；
图 3为本发明实施例的无线通信系统第一实施例的具体结构示意图； 图 4为本发明实施例的无线通信系统第二实施例的具体结构示意图； 图 5为本发明实施例的无线通信系统第三实施例的具体结构示意图； 图 6为本发明实施例的无线通信系统第四实施例的具体结构示意图； 图 7为本发明实施例的通信方法的流程图；
图 8为本发明实施例的通信方法的流程图。
具体实施方式
首先对本发明实施例的无线通信系统实施例的整体技术方案进行说明。一 种无线通信系统实施例可以包括一个具有基站控制器功能的中心站和受中心 站控制的至少一个接入设备， 中心站对接入设备进行统一的资源调度， 中心站 和接入设备之间釆用有线方式连接；接入设备用于将中心站发出的有线信号解 调为射频信号，将射频信号发送给目的无线用户， 并将无线用户发出的上行射 频信号调制为有线信号发送给中心站；中心站用于对核心网提供的数据进行基 带处理、中频处理以及射频处理，得到射频信号，将射频信号调制为有线信号， 再将有线信号发送给数据的目的无线用户对应的接入设备，并将接入设备发出 的有线信号解调为射频信号，对射频信号进行射频处理、 中频处理以及基带处 理， 得到无线用户发送的数据， 再将数据提供给核心网。 应当理解的是， 本发 明实施例提及的无线用户可以是指无线用户终端。
其中， 中心站和接入设备之间釆用光纤连接， 这样， 中心站和接入设备之 间的光纤链路中传输的就是光信号。
中心站可以对接入设备进行统一的资源调度， 或者说， 多个接入设备可以 共享一个中心站， 由一个中心站进行集中控制。 中心站能够掌握其控制下的所 有接入设备的空口资源情况。例如，假设一个中心站控制下的三个接入设备的 覆盖范围部分重叠， 其中的一个接入设备的空口资源占用比较大， 为緩解接入 设备的空口资源占用压力，这个中心站可以将重叠覆盖范围内的与这个接入设 备通信的部分无线用户调整到其他两个接入设备上， 即，使部分无线用户与其 他两个接入设备通信。 当然， 中心站可以对接入设备进行统一的资源调度还可 以有其他实现方式， 这里不再——举例说明。
中心站可以包括光调制器， 用于将经过基带处理、 中频处理以及射频处理 得到的射频信号调制为发送给接入设备的光信号，接入设备也可以包括光调制 器， 用于将无线用户发送的射频信号调制为发送给中心站的光信号。 光调制器 可以包括光外调制器（ EOM, Electro-Optic Modulator )或直接调制激光器（ LD, Laser Diode )。 光外调制器可以是铌酸锂电光调制器或半导体电吸收光调制器 ( EAM , Electro-Absorption Modulator ) (以下简称电吸收光调制器）等， 直接 调制激光器可以是直接调制半导体激光器。特别的， 光调制器可以是电吸收光 收发器，这种电吸收光收发器既具有信号调制的功能，又具有信号解调的功能。 如果中心站的光调制器为电吸收光收发器，则电吸收光收发器在中心站中还可 以将接入设备发出的光信号解调为射频信号。如果接入设备的光调制器为电吸 收光收发器，则电吸收光收发器在接入设备中还将中心站发出的光信号解调为 射频信号。
一般来说，将下行射频信号调制为光信号所使用的光载波与将上行射频信 号调制为光信号所使用的光载波不相同，具体可以由一个多波长激光器或两个 单波长激光器发出两个不同的光载波实现。应当理解的是， 下行和上行使用的 光载波也可以相同，具体可以由一个多波长激光器或一个单波长激光器发出一 个光载波实现。
中心站和 /或下行光纤链路中可以包括光放大器， 用于将下行光信号进行 放大处理。 接入设备和 /或上行光纤链路中也可以包括光放大器， 用于将上行 色散补偿装置， 用于对光信号进行色散补偿。
下面结合几个附图， 对本发明实施例的无线通信系统实施例进行详细说 明。
如图 2所示， 本发明实施例的无线通信系统包括中心站 21及其控制的多 个基站 22 , 这里的基站即为一种接入设备， 以下实施例相同。 中心站 21与多 网络主要是由光纤组成的， 所以也可以说， 中心站 21与多个基站 22之间通过 光纤连接。 中心站 21除具有基站控制器的功能外， 还具有传统基站的基带处 理、 中频处理及射频处理等功能， 而基站 22实质上已经不是传统意义的基站， 其主要作用就是射频信号与光信号之间的转换以及射频信号的天线馈送与接 收。
对于下行信息， 中心站 21获得核心网提供的数据后， 将数据进行基带处 理、 中频处理及射频处理， 得到射频信号， 将射频信号调制到光载波上， 形成 光信号， 光信号经过光纤（也就是光纤馈送网络）传输到数据的目的用户单元 ( Customer Units ) 23对应的基站 22, 基站 22对光信号进行解调， 得到射频 信号， 最后将射频信号发给目的用户单元 23。 对于上行信息， 源用户单元 23 向对应的基站 22发送射频信号，基站 22将射频信号调制到光载波上， 形成光 信号， 光信号经过光纤传输到中心站 21 , 中心站 21对光信号进行解调， 得到 射频信号， 将射频信号进行射频处理、 中频处理及基带处理， 得到发送给核心 网的数据， 最后将数据发给核心网。
中心站 21和基站 22可以分别使用光外调制器或直接调制半导体激光器进 行射频信号到光信号的转换。光外调制器可以是铌酸锂电光调制器或半导体电 吸收光调制器， 它们具有高 -3dB 带宽、 高电光转换效率、 啁啾特性可调和非 线性受控等优点， 非常适合大带宽高性能的无线通信系统。 其中， 半导体电吸 收调制器更具有低功耗、 高消光比、 器件体积小等优点， 同时， 由于半导体电 吸收调制器使用 III-V族半导体材料， 所以小体积的半导体电吸收调制器可以 实现与射频发射前端的放大器等功率型微波器件以及半导体激光器的单片集 成。另夕卜，中心站 21和基站 22可以分别使用光电探测器（PD, Photo-Detector ) 进行光信号到射频信号的转换。 中心站和基站可以分别有多种形式的内部结构， 图 3 即是其中的一种形 式。 如图 3所示， 中心站 31 包括光外调制器 311、 激光器 312、 光电探测器 313、 射频混频器 314、 射频混频器 314'、 射频本地振荡器 315、 中频混频器 316、中频混频器 316，、中频信号发生器 317及无线调制解调器（ Radio Modem ) 318。
对于下行信息， 核心网 33提供的数据到达无线调制解调器 318后， 无线 调制解调器 318将数据进行基带处理，得到基带信号， 并将基带信号发送到中 频混频器 316; 中频混频器 316将基带信号和中频信号发生器 317产生的信号 进行处理， 得到中频信号， 并将中频信号发送给射频混频器 314; 射频混频器 314将中频信号和射频本地振荡器 315产生的射频信号进行处理， 得到射频信 号， 并将射频信号发送到光外调制器 311 ; 光外调制器 311将射频信号调制到 激光器 312发出的光载波上， 形成光信号， 通过光纤（也就是图 3中的下行链 路）将光信号发送到基站 32。
对于上行信息， 光电探测器 313接收到基站 32通过光纤 (也就是图 3中 的上行链路）发送的光信号后， 对光信号进行解调， 得到射频信号， 并将射频 信号发送到射频混频器 314' ; 射频混频器 314'将射频信号和射频本地振荡器 315 产生的信号进行处理， 得到中频信号， 并将中频信号发送到中频混频器 316' ;中频混频器 316，将中频信号和中频信号发生器 317产生的信号进行处理， 得到基带信号，并将基带信号发送到无线调制解调器 318;无线调制解调器 318 对基带信号进行处理， 得到发送给核心网 33的数据， 并将数据发送给核心网 33。
请再参见图 3 ,基站 32包括光外调制器 321、激光器 322、光电探测器 323、 放大滤波单元 324和放大滤波单元 324'。对于下行信息，光电探测器 323接收 到中心站 31发送的光信号后， 对光信号进行解调， 得到射频信号， 射频信号 经过放大滤波单元 324的放大滤波处理后，通过天线发送到目的用户单元。对 于上行信息，射频信号经过天线接收后，经过放大滤波单元 324'的放大滤波处 理， 到达光外调制器 321 , 光外调制器 321将经过放大滤波处理的射频信号调 制到激光器 322发出的光载波上， 形成光信号， 并将光信号发送到中心站 31。
由于中心站 31需要将下行射频信号调制到光载波中，基站 32需要将上行 射频信号调制到光载波中， 所以在图 3中， 中心站 31和基站 32分别都设置一 个激光器用于发出光载波。 但在实际应用中， 可以仅在中心站 31或仅在基站 32设置一个多波长激光器或两个单波长激光器， 多波长激光器或两个单波长 激光器可发出两个不同的光载波， 其中一个光载波用于携带射频信号， 而另一 个光载波不携带任何射频信号， 而是在直接到达对方的光外调制器后，携带对 方发送的射频信号到达本地的光电探测器。这样， 无论是上行信息还是下行信 息，通过设置在中心站 31或基站 32的一个多波长激光器或两个单波长激光器 发出的两个不同的光载波就可以完成信息的传递。
具体的， 如图 4所示， 中心站 41包括电吸收光调制器 411、 激光器 412、 激光器 412'、 光电探测器 413、 射频混频器 414、 射频混频器 414'、 射频本地 振荡器 415、 放大滤波单元 419及放大滤波单元 419' , 当然， 中心站 41还包 括中频处理和基带处理部分，由于中频处理和基带处理在本实施例中不做重点 说明， 所以图中未绘示。 基站 42包括电吸收光调制器 421、 光电探测器 423、 放大滤波单元 424及放大滤波单元 424'。另外， 图中带有箭头的实线表示光信 号经过的路径， 带有箭头的虚线表示电信号经过的路径。
对于下行信息，经过射频混频器 414混频产生的射频信号经过放大滤波单 元 419的放大滤波处理后， 到达电吸收光调制器 411 ; 电吸收光调制器 411将 射频信号调制到激光器 412发出的光载波 λΐ上， 形成光信号， 并将光信号通 过光纤（也就是图 4中的下行链路)发送到基站 42;激光器 412'发出光载波 λ2, 光载波 λ2不经过电吸收光调制器 411 , 而是直接通过光纤到达基站 42; 光载 波 λΐ和光载波 λ2到达基站 42后， 相互分离， 光载波 λΐ传输到光电探测器 423 ,光载波 λ2传输到电吸收光调制器 421 ;光电探测器 423接收到光信号后， 对光信号进行解调，得到射频信号，射频信号经过放大滤波单元 424的放大滤 波处理后， 通过天线发送到目的用户单元。
对于上行信息 ,射频信号经过天线接收后，经过放大滤波单元 424'进行放 大滤波处理后， 到达电吸收光调制器 421 (光外调制器的一种）， 电吸收光调 制器 421将经过放大滤波处理的射频信号调制到光载波 λ2上， 形成光信号， 并将光信号通过光纤 （也就是图 4中的上行链路）发送到中心站 41 ; 中心站 41 的光电探测器 413对光信号进行解调， 得到射频信号， 射频信号经过放大 滤波单元 419，的放大滤波处理后， 到达射频混频器 414，。 后续过程同图 3所 示的实施例的对应描述相同， 这里不再赘述。
此外，射频信号在光纤中的传输距离主要受限于射频信号在光纤传输过程 中的能量损耗、由光纤色散引起的载波抑制效应和光纤非线性效应所产生的失 真。 对此， 可以设置光放大器来提高射频信号的增益， 可以在图 4中的中心站 41 和基站 42 之间的光纤链路上设置光纤布喇格光栅（FBG, Fiber Bragg Grating ) 43、 43'作为补偿器件来对信号损伤进行补偿。
需要说明的是， 在图 4中， 虽然是在中心站 41设置了两个激光器 412、 412，， 但在实际应用中， 可以在中心站 41 中仅设置一个多波长激光器， 应当 理解的是， 也完全可以将两个激光器或一个多波长激光器设置在基站 42中， 激光器在基站 42中的工作方式与在中心站 41中的工作方式完全相同，这里不 再赘述。
在图 4中，将射频信号调制到光载波上所使用的是电吸收光调制器，对光 信号进行解调所使用的是光电探测器。在实际应用中，还可以使用特殊的电吸 收光调制器 电吸收光收发器（EAT, Electro-Absorption Transceiver )对信 号进行调制和解调， 由于电吸收光收发器既具有调制功能， 又具有解调功能， 所以使用电吸收光收发器可以同时替代图 4 中的电吸收光调制器和光电探测 器， 从而可以简化图 4中的中心站 41和 /或基站 42的结构。
具体的， 如图 5所示， 中心站 51包括电吸收光调制器 511、 激光器 512、 激光器 512'、 光电探测器 513、 射频混频器 514、 射频混频器 514'、 射频本地 振荡器 515、 带通滤波器 516、 光放大器 517及射频放大器 519, 当然， 中心 站 51还包括中频处理和基带处理部分， 由于中频处理和基带处理在本实施例 中不做重点说明， 所以图中未绘示。 基站 52 包括电吸收光收发器 521、 射频 放大器 524、 射频放大器 524，、 带通滤波器 526及光放大器 527。 另外， 图中 带有箭头的实线表示光信号经过的路径，带有箭头的虚线表示电信号经过的路 径。
对于下行信息，经过射频混频器 514混频产生的射频信号发送至电吸收光 调制器 511 ; 电吸收光调制器 511将下行射频信号调制到激光器 512发出的光 载波 λΐ上， 形成光信号， 并将光信号通过光纤 （也就是图 5中的下行链路） 发送到基站 52, 其中， 光信号在传输过程中要经过光放大器 517的放大处理； 激光器 512'发出光载波 λ2 , 光载波 λ2不经过电吸收光调制器 511 , 而是直接 通过光纤到达基站 52; 光载波 λΐ和光载波 λ2到达基站 52后， 基站 52中的 电吸收光收发器 521对光载波 λΐ承载的下行射频信号进行解调， 得到射频信 号，射频信号经过带通滤波器 526的滤波处理和放大器 524的放大处理后，通 过天线发送到目的用户单元； 光载波 λ2到达电吸收光收发器 521后， 用于上 行信息的传输。
对于上行信息，射频信号经过天线接收后，经过放大器 524'的放大滤波处 理， 到达电吸收光收发器 521 , 电吸收光收发器 521将经过放大滤波处理的射 频信号调制到光载波 λ2上， 形成光信号， 并将光信号通过光纤 （也就是图 5 中的上行链路）发送到中心站 51 , 其中， 光信号在传输过程中经过光放大器 527的放大处理； 中心站 51的光电探测器 513对光信号进行解调， 得到射频 信号，射频信号经过带通滤波器 516的滤波处理和射频放大器 519的放大处理 后， 到达射频混频器 514'。后续过程同图 3所示的实施例的对应描述相同， 这 里不再赘述。
需要说明的是， 在图 5中， 虽然电吸收光收发器设置在基站 52中， 但在 实际应用中， 完全可以将电吸收光收发器设置在中心站 51 中， 当然， 中心站 51和基站 52也可以同时设置有电吸收光收发器，电吸收光收发器在中心站 51 中的工作方式与在基站 52中的工作方式完全相同， 这里不再赘述。
在图 4和图 5中， 上行信息和下行信息分别在不同波长的光载波上传输， 在实际应用中， 上行信息和下行信息也可以在相同的光载波上传输， 这样可以 提高光载波资源的利用效率， 提高系统容量。
具体的， 如图 6所示， 中心站 61包括电吸收光调制器 611、 激光器 612、 光电探测器 613、 射频混频器 614、 射频混频器 614'、 射频本地振荡器 615、 带通滤波器 616、 光放大器 617及射频放大器 619, 当然， 中心站 61还包括中 频处理和基带处理部分， 由于中频处理和基带处理在本实施例中不做重点说 明， 所以图中未绘示。 基站 62包括电吸收光收发器 621、 射频放大器 624、 射 频放大器 624，、 带通滤波器 626及光放大器 627。 另外， 图中带有箭头的实线 表示光信号经过的路径， 带有箭头的虚线表示电信号经过的路径。 对于下行信息，经过射频混频器 614混频产生的射频信号发送至电吸收光 调制器 611 ; 电吸收光调制器 611将射频信号调制到激光器 612发出的光载波 λΐ上， 形成光信号， 并将光信号通过光纤 （也就是图 6中的下行链路）发送 到基站 62, 其中， 光信号在传输过程中要经过光放大器 617的放大处理； 光 载波 λΐ到达基站 62后，基站 62中的电吸收光收发器 621对光信号进行解调， 得到射频信号， 射频信号经过带通滤波器 626 的滤波处理和射频放大器 624 的放大处理后， 通过天线发送到目的用户单元。
对于上行信息，射频信号经过天线接收后，经过射频放大器 624'放大处理， 到达电吸收光收发器 621 , 电吸收光收发器 621将经过放大处理的射频信号调 制到光载波 λΐ上， 形成光信号， 并将光信号通过光纤 （也就是图 6中的上行 链路）发送到中心站 61 , 其中， 光信号在传输过程中经过光放大器 627的放 大处理； 中心站 61的光电探测器 613对光信号进行解调， 得到射频信号， 射 频信号经过带通滤波器 616的滤波处理和射频放大器 619的放大处理后，到达 射频混频器 614'。后续过程同图 3所示的实施例的对应描述相同，这里不再赘 述。
需要说明的是， 在图 6中， 激光器虽然设置在中心站 61中， 但在实际应 用中， 激光器也可以只设置在基站 62中， 激光器在基站 62中的工作方式与在 中心站 61中的工作方式相同， 这里不再赘述。
本发明实施例除提供了上述无线通信系统外，还提供了两种通信方法， 两 种通信方法都可以应用于包括中心站及受中心站控制的至少一个接入设备的 无线通信系统， 中心站与至少一个接入设备之间有线连接，接入设备通过射频 信号与无线用户通信。
其中的一种通信方法如图 7所示， 包括以下步骤：
S701 : 中心站获得核心网提供的数据， 并将所述数据转换为有线信号； S702:中心站通过有线传输介质将所述有线信号发送给所述数据的目的无 线用户对应的接入设备；
S703: 所述接入设备将有线信号解调为射频信号，并将射频信号发送给所 述目的无线用户。
其中， 有线信号可以为光信号， 有线传输介质可以为光纤。 另外的一种通信方法如图 8所示， 包括以下步骤：
S801 :接入设备获得无线用户提供的射频信号， 并将射频信号调制为有线 信号；
S802: 接入设备通过有线传输介质将有线信号发送给中心站；
S803 : 中心站将有线信号转换为提供给核心网的数据后，将数据提供给核 心网。
其中， 有线信号可以为光信号， 有线传输介质可以为光纤。
上述两种通信方法的具体实施方式可以参见图 2-图 6对应的实施例，这里 不再赘述。
本发明实施例还提供了一种中心站， 这种中心站包括调制解调单元、基带 处理单元、 中频处理单元以及射频处理单元； 基带处理单元用于将核心网提供 的数据转换为基带信号， 中频处理单元用于将基带信号转换为中频信号，射频 处理单元用于将中频信号转换为射频信号，调制解调单元用于将射频信号调制 为有线信号； 调制解调单元还用于将有线信号解调为射频信号，射频处理单元 还用于将射频信号转换为中频信号，中频处理单元还用于将中频信号转换为基 带信号， 基带处理单元还用于将基带信号转换为提供给核心网的数据。
其中，有线信号可以是光信号。调制解调单元可以包括光调制器及光电探 测器； 光调制器用于将射频处理单元得到的射频信号调制为光信号， 光电探测 器用于将光信号解调为发送给射频处理单元的射频信号。光调制器可以包括光 外调制器或直接调制激光器。光外调制器可以为铌酸锂电光调制器或半导体电 吸收光调制器。调制解调单元也可以为电吸收光收发器。 中心站还可以包括激 光器， 用于产生光载波。 中心站还可以包括放大滤波单元， 用于将调制后的射 频信号和 /或解调前的射频信号进行放大滤波处理。 放大滤波单元可以包括放 大器及带通滤波器。 当然， 中心站还可以有其他结构形式， 具体可以参见图 3-6所示的中心站的结构以及相应的说明， 这里不再赘述。
本发明实施例还提供一种接入设备（下文以基站为例进行说明）， 包括： 调制解调单元， 用于将无线用户提供的射频信号调制为有线信号， 并将获得的 有线信号解调为发送给无线用户的射频信号。
其中，有线信号可以为光信号。调制解调单元可以包括光调制器及光电探 测器； 光调制器用于将无线用户提供的射频信号调制为光信号， 光电探测器用 于将光信号解调为发送给无线用户的射频信号。调制解调单元可以为电吸收光 收发器。 基站还可以包括激光器， 用于产生光载波。 基站还可以包括放大滤波 单元， 用于将调制后的射频信号和 /或解调前的射频信号进行放大滤波处理。 放大滤波单元可以包括放大器及带通滤波器。 当然，基站还可以有其他结构形 式， 具体可以参见图 3-6所示的基站的结构以及相应的说明， 这里不再赘述。
在上述所有的实施例中， 如果需要优化射频信号的链路增益， 则可以调整 激光器输出的光载波波长和光功率； 如果需要优化光调制器传递函数的线性 度， 则可以调整与光调制器有关的工作条件； 如果需要优化光电探测器的解调 结果， 则可以调整光电探测器的工作条件， 优化探测率。
在本发明实施例的通信系统及接入设备中， 接入设备主要具有电光和 /或 光电转换的功能， 结构简单， 功耗低， 所以部署成本相对较低， 从而可以方便 的部署在大多数区域， 尤其是在宽带无线通信系统中由于成本、 功率等原因不 方便部署传统基站的区域， 例如室内。
在本发明实施例的通信系统中，由于接入设备和中心站之间釆用有线方式 连接， 而且接入设备可以更接近于无线用户， 所以信号在传输过程中的损耗相 对较小， 从而提高了信号质量和传输距离。
在本发明实施例的通信系统中， 多个紧凑型接入设备共享中心站的资源， 同时受到中心站的集中控制， 这样可以实现对不同速率、 不同格式的数据的透 明传输， 实现对网络和频率资源的动态管理和优化分配， 也易于网络升级， 降 低了安装和维护成本。
在本发明的所有实施例中， 由于可以对信号进行多路的合成和分解， 所以 可以使用多种复用 /解复用技术来提高无线通信系统可以支持的信息容量。
进一步的， 如果使用电吸收光收发器进行光信号和电信号之间的调制解 调，使用一个激光器发出的光载波进行信号的调制， 则可以简化中心站和接入 设备的结构， 进一步的降低部署成本。
进一步的，如果在光纤链路上使用放大器，则可以进一步提高信号的增益、 信号的传输距离和质量； 如果使用色散补偿器件对信号损伤进行补偿， 则也可 以进一步提高信号的传输距离和质量。 进一步的，如果使用铌酸锂电光调制器或半导体电吸收光调制器等光外调 制器对光信号进行调制， 则由于这些器件高电光转换效率、啁啾特性可调和非 线性受控等优点， 可以进一步提高无线通信系统的整体性能。
最后需要说明的是：
1.本发明的实施例完全可以应用于未来的微微蜂窝 （Pico-cell ) 结构或甚 微蜂窝 （Femto-cell ) 结构。
在城市环境中，由于多个建筑物对电磁波的反射以及建筑物和地下建筑本 身对电磁波的屏蔽作用，使得在城市内进行高带宽高质量的无线信号传输和实 现高质量的无线信号室内覆盖变得更加困难，城市宽带无线网络的组网极其复 杂。 针对以上超宽带无线通信系统在室内覆盖和在城市环境中应用存在的问 题，在未来超宽带无线接入系统组网中将釆用小覆盖面积的微微蜂窝结构或甚 微蜂窝结构，蜂窝覆盖面积的减小可以为系统组网带来了灵活性， 同时也减少 了移动环境的复杂性，极大的降低了多径衰落对系统的影响以及多径效应引起 的码间干扰。
由于本发明实施例釆用结构简单、容易部署的基站作为接入设备， 所以很 容易在城市中部署大量的接入设备，从而实现了小覆盖面积的蜂窝结构， 又由 于接入设备与中心站之间釆用有线连接，所以极大的降低了多径衰落对系统的 影响以及多径效应引起的码间干扰。 因此， 本发明的实施例完全可以应用于未 来的微微蜂窝结构或甚微蜂窝结构。
2.本发明的实施例完全可以满足毫米波无线通信（ Millimeter-wave wireless communication ) 的要求。
目前， 第一代和第二代移动通信系统的传输速率只有几十 Kb/s 到几百 Kb/s, 而基于码分多址（CDMA )技术的第三代移动通信系统（3G )的传输速 率也只有 Mbit/s数量级。为了实现未来超宽带的无线通信，又提出和研究了第 四代移动通信系统（4G, 也被称作 B3G ), 第四代移动通信系统利用全新的无 线传输技术， 支持数量级在 100Mb/s乃至 Gb/s以上的信息传输速率， 这样的 超宽带无线通信系统可以同时支持电话业务、海量的数据业务、 高清晰度电视 为代表的宽带多媒体业务等， 可以充分满足未来人们对移动宽带接入的需求。
随着无线通信数据传输速率的提高，未来必须要提高无线载波的工作频率 以提高无线通信系统的容量。 然而， 目前的大多数无线通信业务的工作频率都 集中在 5GHz以下， 现有的低频段频率资源几乎都已经被分配完毕。 正如人们 对计算机中央处理器（CPU )和内存的需求那样， 无线通信领域对无线频谱的 需求日益增加，具有更高工作频率的集成通信系统会拥有更强的抗干扰能力和 更可靠的保密通信功能。
最近几年， 毫米波段例如 60GHz附近的 7GHz频谱带宽是不经授权即可 使用的频谱资源。在美国，该频谱范围是 57-64GHZ,而在日本则是 59-66GHz。 另外， 国外工作频率为 94GHz的毫米波集成技术已成功地应用于国防中全天 候、 高分辨率毫米波被动成像、 精确定位等特殊领域。 尽管如 60GHz等毫米 波频段不是电磁波在大气中的传输窗口，但它在短距离无线通信中的应用前景 是毋庸质疑的， 这包括在高速 Gb/s点对点数据传输、 超大容量无线局域网络、 个人短距离高速数据传输网络、 毫米波车载防撞雷达等方面。 目前， 世界各国 的科研人员都把基于毫米波频段的无线通信作为未来无线通信的一个重要研 方向。
但是， 毫米波通信技术也有缺陷， 即， 毫米波信号在大气中传播时会由于 吸收和反射而有相当多的损耗。 不过， 由于本发明实施例釆用结构简单、 容易 部署的基站作为接入设备， 而且接入设备与中心站之间釆用有线连接， 所以在 极大程度上降低了毫米波信号在大气中传播时的损耗， 如果接入设备部署合 理， 甚至可以实现接近零损耗。 因此， 本发明的实施例可以应用于毫米波无线 通信中， 完全满足未来的毫米波无线通信技术的要求。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分流程 , 是可以通过计算机程序来指令相关的硬件来完成，所述的程序可存储于一计算 机可读取存储介质中，该程序在执行时，可包括如上述各方法的实施例的流程。 其中，所述的存储介质可为磁碟、光盘、只读存储记忆体（Read-Only Memory, ROM )或随机存储记忆体（Random Access Memory, RAM )等。
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通 技术人员来说， 在不脱离本发明原理的前提下， 还可以做出若干改进和润饰， 这些改进和润饰也应视为本发明的保护范围。

Claims

权 利 要 求
1.一种无线通信系统， 其特征在于：
包括一个具有基站控制器功能的中心站和受所述中心站控制的至少一个 接入设备， 所述中心站和接入设备之间釆用有线方式连接；
所述接入设备用于将所述中心站发出的有线信号解调为射频信号，将射频 信号发送给目的无线用户，并将无线用户发出的上行射频信号调制为有线信号 发送给所述中心站；
所述中心站用于对核心网提供的数据进行基带处理、中频处理以及射频处 理， 得到射频信号， 将射频信号调制为有线信号， 再将有线信号发送给数据的 目的无线用户对应的所述接入设备，并将所述接入设备发出的有线信号解调为 射频信号， 对射频信号进行射频处理、 中频处理以及基带处理， 得到无线用户 发送的数据， 再将所述数据提供给核心网。
2.如权利要求 1所述的无线通信系统， 其特征在于： 所述中心站和接入设 备之间釆用光纤连接， 所述有线信号为光信号。
3.如权利要求 2所述的无线通信系统， 其特征在于： 所述中心站将射频信 号调制为光信号所使用的光载波与所述接入设备将射频信号调制为光信号所 使用的光载波相同。
4.如权利要求 2所述的无线通信系统，其特征在于： 所述中心站和 /或下行 光纤链路中包括光放大器， 用于将下行光信号进行放大处理。
5.如权利要求 2所述的无线通信系统，其特征在于： 所述接入设备和 /或上 行光纤链路中包括光放大器， 用于将上行光信号进行放大处理。
6.如权利要求 2所述的无线通信系统， 其特征在于： 所述下行光纤链路中 和 /或上行光纤链路中包括色散补偿装置， 用于对光信号进行色散补偿。
7一种中心站， 其特征在于：
包括调制解调单元、 基带处理单元、 中频处理单元以及射频处理单元； 所述基带处理单元用于将核心网提供的数据转换为基带信号，所述中频处 理单元用于将基带信号转换为中频信号，所述射频处理单元用于将中频信号转 换为射频信号， 所述调制解调单元用于将射频信号调制为有线信号；
所述调制解调单元还用于将有线信号解调为射频信号，所述射频处理单元 还用于将射频信号转换为中频信号，所述中频处理单元还用于将中频信号转换 为基带信号， 所述基带处理单元还用于将基带信号转换为提供给核心网的数 据。
8.如权利要求 7所述的中心站， 其特征在于： 所述有线信号为光信号。 9.如权利要求 8所述的中心站， 其特征在于：
所述调制解调单元包括光调制器及光电探测器；
所述光调制器用于将所述射频处理单元得到的射频信号调制为光信号，所 述光电探测器用于将光信号解调为发送给所述射频处理单元的射频信号。
10.如权利要求 9所述的中心站， 其特征在于： 所述光调制器包括光外调 制器 EOM或直接调制激光器 LD。
11.如权利要求 10所述的中心站， 其特征在于： 所述光外调制器为铌酸锂 电光调制器或半导体电吸收光调制器。
12.如权利要求 8所述所述的中心站， 其特征在于： 所述调制解调单元为 电吸收光收发器。
13.—种接入设备， 其特征在于， 包括：
调制解调单元， 用于将无线用户提供的射频信号调制为有线信号， 并将获 得的有线信号解调为发送给无线用户的射频信号。
14.如权利要求 13所述的接入设备，其特征在于，所述有线信号为光信号。
15.如权利要求 14所述的接入设备， 其特征在于， 所述调制解调单元包括 光调制器及光电探测器；
所述光调制器用于将无线用户提供的射频信号调制为光信号，所述光电探 测器用于将光信号解调为发送给无线用户的射频信号。
16.如权利要求 14所述的接入设备， 其特征在于， 所述调制解调单元为电 吸收光收发器。
17.如权利要求 14所述的接入设备， 其特征在于，还包括：放大滤波单元， 用于将调制后的射频信号和 /或解调前的射频信号进行放大滤波处理。
18.如权利要求 17所述的接入设备， 其特征在于， 所述放大滤波单元包括 放大器及带通滤波器。
19.一种通信方法， 其特征在于， 包括以下步骤： 中心站获得核心网提供的数据， 并将所述数据转换为有线信号； 中心站通过有线传输介质将所述有线信号发送给所述数据的目的无线用 户对应的接入设备；
所述接入设备将有线信号解调为射频信号，并将射频信号发送给所述目的 无线用户。
20.如权利要求 19所述的通信方法，其特征在于，所述有线信号为光信号， 所述有线传输介质为光纤。
21.—种通信方法， 其特征在于， 包括以下步骤：
接入设备获得无线用户提供的射频信号 ,并将所述射频信号调制为有线信 号；
接入设备通过有线传输介质将所述有线信号发送给中心站；
所述中心站将有线信号转换为提供给核心网的数据后，将所述数据提供给 所述核心网。
22.如权利要求 19所述的通信方法，其特征在于，所述有线信号为光信号， 所述有线传输介质为光纤。
PCT/CN2008/073474 2007-12-12 2008-12-12 Système de communication sans fil, station centrale, dispositif d'accès et procédé de communication WO2009074116A1 (fr)

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