WO2023220965A1 - Améliorations sur un réseau de liaison frontale - Google Patents

Améliorations sur un réseau de liaison frontale Download PDF

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Publication number
WO2023220965A1
WO2023220965A1 PCT/CN2022/093546 CN2022093546W WO2023220965A1 WO 2023220965 A1 WO2023220965 A1 WO 2023220965A1 CN 2022093546 W CN2022093546 W CN 2022093546W WO 2023220965 A1 WO2023220965 A1 WO 2023220965A1
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Prior art keywords
signal
cdm
orthogonal codes
group
code division
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PCT/CN2022/093546
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English (en)
Inventor
Xiaofeng Hu
Dongxu ZHANG
Kaibin Zhang
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Nokia Shanghai Bell Co., Ltd.
Nokia Solutions And Networks Oy
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Priority to PCT/CN2022/093546 priority Critical patent/WO2023220965A1/fr
Publication of WO2023220965A1 publication Critical patent/WO2023220965A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • 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

Definitions

  • Embodiments of the present disclosure generally relate to the field of telecommunication and in particular to devices, methods, apparatuses and computer readable storage media of the fronthaul communication.
  • the optical fronthaul link is critical for the current 4G and 5G wireless communication systems, and may be implemented by two approaches, digital radio-over-fiber (D-RoF) and analog radio-over-fiber (A-RoF) .
  • D-RoF directly quantizes the analog signals from RRHs and transmits the digitized data in on-off-keying (OOK) format with a low spectral efficiency and a high fidelity.
  • OOK on-off-keying
  • the data rate based on CPRI protocol for transmission of 20-MHz LTE signal and 100-MHz 5G signal are required to be about 1.2 Gbps and 5 Gbps, respectively, with 50 ⁇ 60x bandwidth expansion. This enormous bandwidth consumption greatly limits the application of D-RoF scheme in 5G systems.
  • A-RoF technology has been proposed and extensively investigated.
  • FDM frequency division multiplexing
  • Some other A-RoF schemes utilize DSP-based channel aggregation and de-aggregation method to realize the simultaneous transmission of plenty of radio signals from antennas.
  • A-RoF scheme usually stacks tens of analog OFDM signals up and has a high peak-to-average-ratio (PAPR) , it is susceptible to the imperfect optical channel during fiber transmission compared to D-RoF, resulting in a relatively poor system performance.
  • PAPR peak-to-average-ratio
  • Example embodiments of the present disclosure provide a code division multiplexing (CDM) based fronthaul scheme.
  • CDM code division multiplexing
  • an aggregator of a fronthaul network comprises a group of first analog-to-digital convertors (ADCs) , a code division multiplexer (CDM) and a first digital-to-analog (DAC) .
  • the group of first ADCs is coupled to the CDM, and configured to convert a group of first wireless signals to a group of first signals corresponding to respective wireless channels.
  • the CDM is coupled to a first digital-to-analog, DAC, and configured to apply code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; and aggregate the group of coded signals into a code division multiplexed, CDM, signal.
  • the first DAC is configured to convert the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link.
  • a BBU of a fronthaul network comprises an ADC, an equalizer and a code division de-multiplexer (CD-DM) .
  • the ADC is coupled to the equalizer, and configured to convert a second signal delivered in an optical fronthaul link to a digital CDM signal, the digital CDM signal is processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels.
  • the equalizer is coupled to the CD-DM, and configured to equalize the CDM signal in terms of at least one equalization performance.
  • the CD-DM is configured to apply code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • a fronthaul system comprises the aggregator according to the first aspect, the BBU according to the second aspect and the optical fronthaul link connecting the aggregator with the BBU.
  • a method comprises: converting, at an aggregator of a fronthaul network, a group of first wireless signals to a group of first signals corresponding to respective wireless channels; applying code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; aggregating the group of coded signals into a code division multiplexed, CDM, signal; and converting the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link of the fronthaul network.
  • a method comprises: converting, at a baseband unit, BBU, of a fronthaul network, a second signal delivered in an optical fronthaul link of the fronthaul network to a digital code division multiplexed, CDM, signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels; equalizing the CDM signal in terms of at least one equalization performance; and applying code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • a method comprises: applying, at a baseband unit, BBU, of a fronthaul network, code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; aggregating the group of coded signals into a code division multiplexed, CDM, signal; pre-equalizing the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal; and converting the equalized CDM signal to a third signal to be delivered in the optical fronthaul link.
  • BBU baseband unit
  • a method comprises: converting, at an aggregator of a fronthaul network, a third signal delivered in the optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels; applying code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; and converting the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fourth aspect.
  • a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fifth aspect.
  • a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the sixth aspect.
  • a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the seventh aspect.
  • an apparatus comprising means for converting, at an aggregator of a fronthaul network, a group of first wireless signals to a group of first signals corresponding to respective wireless channels; means for applying code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; means for aggregating the group of coded signals into a code division multiplexed, CDM, signal; and means for converting the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link.
  • an apparatus comprising means for converting, at a baseband unit, BBU, of a fronthaul network, a second signal delivered in an optical fronthaul link to a digital code division multiplexed, CDM, signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels; means for equalizing the CDM signal in terms of at least one equalization performance; and means for applying code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • BBU baseband unit
  • an apparatus comprising means for applying, at a baseband unit, BBU, of a fronthaul network, code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; means for aggregating the group of coded signals into a code division multiplexed, CDM, signal; means for pre-equalizing the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal; and means for converting the equalized CDM signal to a third signal to be delivered in an optical fronthaul link.
  • BBU baseband unit
  • an apparatus comprising means for converting, at an aggregator of a fronthaul network, a third signal delivered in an optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels; means for applying code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; means for converting the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • an apparatus comprising the aggregator of the first aspect.
  • an apparatus comprising the BBU of the second aspect.
  • FIGs. 1A and 1B illustrate schematic diagrams of FFT/IFFT-based channel aggregation and de-aggregation of an example aggregated 48 20MHz LTE signal
  • FIG. 1C illustrates an example spectrum of the example aggregated 48 20MHz LTE signal as shown in FIGs. 1A and 1B;
  • FIGs. 2A and 2B illustrate an example network environment in which example embodiments of the present disclosure can be implemented
  • FIG. 3 shows a signaling chart illustrating a training process for the fronthaul network according to some example embodiments of the present disclosure
  • FIG. 4 illustrates a simulation result of EVM performance versus the received optical power based on the fronthaul communication scheme according to some example embodiments of the present disclosure
  • FIG. 5 illustrates a flowchart of an example method of fronthaul communication according to some example embodiments of the present disclosure
  • FIG. 6 illustrates a flowchart of an example method of fronthaul communication according to some example embodiments of the present disclosure
  • FIG. 7 illustrates a flowchart of an example method of fronthaul communication according to some example embodiments of the present disclosure
  • FIG. 8 illustrates a flowchart of an example method of fronthaul communication according to some example embodiments of the present disclosure
  • FIG. 9 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure.
  • FIG. 10 shows a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.
  • references in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
  • circuitry may refer to one or more or all of the following:
  • circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware.
  • circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.
  • the term “communication network” refers to a network following any suitable communication standards, such as fifth generation (5G) or new radio (5G NR) or beyond 5G, e.g., 6G systems, Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) , Wi-Fi, the O-RAN (open RAN) or later developments of the communication systems and standards and so on.
  • 5G fifth generation
  • 5G NR new radio
  • 5G NR fifth generation
  • 6G systems Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) , Wi-Fi, the O-RAN (open RAN) or later developments of the communication systems and standards and
  • the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) new radio (NR) communication protocols, protocols as defined by the O-RAN alliance for the O-RAN standards, and/or any other protocols either currently known or to be developed in the future.
  • NR new radio
  • the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom.
  • the network device may refer to a base station (BS) , a base transceiver station (BTS) , or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR Next Generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio head (RH) , a radio unit (RU) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, a small cell, and so forth, depending on the applied terminology and technology.
  • BS base station
  • BTS base transceiver station
  • AP access point
  • NodeB or NB node B
  • eNodeB or eNB
  • a RAN split architecture may comprise a gNB-CU (Centralized unit, hosting e.g., RRC, SDAP and PDCP) controlling a plurality of gNB-DUs (Distributed unit, hosting e.g., RLC, MAC and PHY) .
  • a relay node may correspond to DU part of the integrated access and backhaul (IAB) node.
  • terminal device refers to any end device that may be capable of wireless communication.
  • a terminal device may also be referred to as a communication device, user equipment (UE) , a subscriber station (SS) , a portable subscriber station, a mobile station (MS) , or an access terminal (AT) .
  • UE user equipment
  • SS subscriber station
  • MS mobile station
  • AT access terminal
  • the terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/
  • the terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) .
  • MT Mobile Termination
  • IAB integrated access and backhaul
  • the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.
  • a user equipment apparatus such as a cell phone or tablet computer or laptop computer or desktop computer or mobile IoT device or fixed IoT device
  • This user equipment apparatus can, for example, be furnished with corresponding capabilities as described in connection with the fixed and/or the wireless network node (s) , as appropriate.
  • the user equipment apparatus may be the user equipment and/or or a control device, such as a chipset or processor, configured to control the user equipment when installed therein. Examples of such functionalities include the bootstrapping server function and/or the home subscriber server, which may be implemented in the user equipment apparatus by providing the user equipment apparatus with software configured to cause the user equipment apparatus to perform from the point of view of these functions/nodes.
  • CPRI is a widely used protocol to support optical fronthaul link for 4G/5G wireless communications, which digitizes the analog radio signals and transmits the digitized OOK signals over optical fibers.
  • 100-MHz 5G signal as an example, the recommended system parameters based on CPRI protocol are given in Table. 1.
  • CW control word
  • OH coding overhead
  • the CPRI protocol requires tremendous optical bandwidth for data transmission and is unsuitable to support 5G system which has a larger radio signal bandwidth and more antennas.
  • eCPRI protocol has been proposed and developed. Nevertheless, D-RoF scheme represented by CPRI and eCPRI still has relatively low spectral efficiency compared to A-RoF scheme. Thus, A-RoF has been intensively discussed and researched in industry and academia.
  • A-RoF transmission scheme is realized based on FFT/IFFT-based channel aggregation and de-aggregation technique.
  • the example 48 20-MHz radio signals from wireless channels are aggregated through N-point FFT and M-point IFFT operations.
  • the spectrum of the example aggregated signal is shown in FIG. 1C.
  • the A-RoF system can deliver 48 20-MHz LTE signals with 1.5-GHz RF bandwidth over a single wavelength, equivalent to an aggregated CPRI data rate of 59 Gbps.
  • the EVM Error Vector Magnitude
  • embodiments of the present disclosure provide an enhanced fronthaul mechanism.
  • A-RoF scheme is utilized to aggregate and transmit the wireless baseband signals by means of low-complexity CDM, leading to a low complexity, low cost and high capacity fronthaul system.
  • high performance gain can be brought to the fronthaul system by using powerful neural network (NN) -enabled equalizer.
  • NN neural network
  • FIG. 2A illustrates an example uplink transmission scenario 201 in the fronthaul system according to the example embodiments of the present disclosure.
  • FIG. 2B illustrates an example downlink transmission scenario 202 in the fronthaul system according to the example embodiments of the present disclosure.
  • the direction from the UE to the network refers to uplink (UL)
  • the direction from the network to the UE refers to downlink (DL) .
  • the example network environment is the fronthaul system that involves a plurality of RRHs 210-1 to 210-N (which may be collectively referred to as RRH 210 hereinafter) , an aggregator 220, an optical fronthaul link 230 and a BBU pool 240.
  • the aggregator 220 includes a group of first ADCs 221-1 to 221-n, a CDM 222 and a first DAC 223 for UL transmission.
  • the aggregator 220 includes a second ADC 224, a CD-DM (code division de-multiplexer) 225 and a group of second DACs 226-1 to 226-n for DL transmission.
  • the BBU 240 includes an ADC 241, an equalizer 242 and a CD-DM 243 for UL transmission.
  • the BBU 240 includes the equalizer 242, a CDM 244, and a DAC 245 for DL transmission.
  • the equalizer 242 may be a NN-based equalizer.
  • the BBU 240 may include, for example, a combination of a CU and a DU defined in O-RAN.
  • the CDM 222 in the aggregator 220 is configured to apply code division multiplexing on samples obtained from the group of first ADCs 221-1 based on Walsh codes.
  • the CD-DM 225 is configured to apply code division de-multiplexing on an equalized signal obtained from the equalizer 242 based on different Walsh codes.
  • the Walsh codes used for code division multiplexing are referred to as first Walsh codes
  • the Walsh codes used for code division de-multiplexing are referred to as second Walsh codes.
  • the first Walsh codes correspond to the second Walsh codes, and both of them are a set of mutually orthogonal sequences composed of ‘1’ and ‘-1’ .
  • the Walsh codes used for code division multiplexing are referred to as third Walsh codes
  • the Walsh codes used for code division de-multiplexing are referred to as fourth Walsh code
  • the third Walsh codes correspond to the fourth Walsh codes.
  • the third Walsh codes correspond to the fourth Walsh codes, and both of them are a set of mutually orthogonal sequences composed of ‘1’ and ‘-1’ .
  • the signals encoded based on the first Walsh codes may be transmitted by one of the aggregator 220 and BBU 240 to the other one, and the other one of the aggregator 220 and BBU 240 may decode based on the second Walsh codes to recover the signals.
  • the CDM aggregation/de-aggregation scheme can realize a large tolerance to power fading caused by chromatic dispersion (CD) in the fiber, i.e., the optical fronthaul link 230.
  • the aggregator 220 assigns the first Walsh codes dedicated to each of wireless signals corresponding to a respective wireless channel with the RRH 210 in code division multiplexing. Additionally, the aggregator 220 may provide a first code-channel comparison table to the BBU 240 through a control channel. With this table, in code division de-multiplexing, the BBU 240 is able to configure the second Walsh codes for decoding the signals encoded based on the first Walsh codes by the aggregator 220.
  • the BBU 240 assigns the third Walsh codes to data streams to be transmitted to the UEs via respective wireless channels in code division multiplexing.
  • the aggregator 220 may provide a second code-channel comparison table to the BBU 240 for DL transmission. Accordingly, in code division multiplexing, the BBU 240 is able to configure third Walsh codes for encoding the signals that is to be delivered in the optical fronthaul link 230. In code division de-multiplexing, the aggregator 220 configures the second Walsh codes for decoding the signals encoded based on the third Walsh codes by the BBU 240.
  • Different code division multiplexing schemes may be used in UL and DL transmissions.
  • the first code-channel comparison table used for UL transmissions may be different from the second code-channel comparison table used for DL transmissions.
  • the first orthogonal codes may be different from the third orthogonal codes, and accordingly, the second orthogonal codes are also different from the fourth orthogonal codes.
  • system parameters shown in Table. 2 are used to configure the fronthaul system.
  • the antennas at RRHs 210-1 to 210-n receive wireless signals from end users, i.e., UEs.
  • the RRHs 210-1 to 210-n then convert the received wireless signals from radio frequency (RF) band to intermedia frequency (IF) band by down-conversion units 212-1 to 212-n.
  • RF radio frequency
  • IF intermedia frequency
  • the number of wireless signals is 48, and the bandwidth of each wireless baseband signal is 100 MHz.
  • the wireless signals are orthogonal frequency division multiplexing (OFDM) modulated, and each of which has 256 subcarriers and a cyclic prefix (CP) of 4 symbols.
  • Copper cables are utilized to connect the RRH 210 and the aggregator 220.
  • the aggregator 220 is employed to aggregate the wireless baseband signals by using code division multiplexing, which is implemented at CDM 222.
  • the analog IF signals received via the copper cables are firstly down-converted to baseband by mixer and local oscillator (LO) .
  • the first ADCs 221-1 to 221-n with the sampling rate of 122.88 MHz and the effective sample bits of 15 sample the in-phase (I) and quadrature (Q) baseband signals in each channel.
  • the CDM 221 repeats each of the samples (which may be also referred to as a group of first signals hereinafter) by M times, where M is the code length of Walsh codes, and then multiplies each of the repeated samples by a corresponding set of first Walsh codes.
  • M is 64, that is, every sample is repeated by 64 times, and then multiply a corresponding set of first Walsh codes with a code length of 64 at the CDM 222.
  • each channel is assigned with a corresponding set of Walsh codes and all the 48 sets of Walsh codes are mutually orthogonal. After the code division multiplexing, the 48 coded signals are added together in time domain to form a CDM signal.
  • the CDM 222 may insert a training pilot sequence composed of ‘0’ and ‘1’ at the beginning of the CDM signal, which will be discussed in details later.
  • the DAC 223 with a sampling rate of 15.73 GHz is employed to convert the CDM signal to an analog CDM signal that is to be delivered in the optical fronthaul link 230.
  • the optical fronthaul link 230 may be a fiber connected to the BBU 240.
  • intensity modulation-direct detection (IM-DD) scheme may be applied in the optical fronthaul link 230.
  • the electrical signal is E/O converted by using a 1550-nm electro-absorption modulated laser (EML) .
  • EML electro-absorption modulated laser
  • the optical CDM signal is launched into a 20-km fiber.
  • PD photo detector converts the optical signal to an electrical signal.
  • the incoming signal into the BBU 240 is sampled by the ADC 241 at a sampling rate of 31.46 GHz, so as to obtain a digital CDM signal.
  • the equalizer 242 is configured for equalizing the digital CDM signal.
  • the equalizer 242 may be a NN-based equalizer that utilizes a NN with two layers.
  • NN training has been implemented to configure NN weights and biases of the NN.
  • the aggregator 220 may insert the training pilot at the beginning of the CDM signal, and the training pilot is used as the input of NN in the training phase.
  • the training of the NN may be stopped until a stop criterion is met.
  • the stop criterion may be at least one equalization performance of the equalizer 242 meeting a predetermined requirement, for example, exceeding a predetermined threshold and so on.
  • the stop criterion may be the training has been performed for a predetermined number of iterations. It should be understood that any other criterion for stopping the iteration can also be used for the example embodiments.
  • the present disclosure is not limited in this regard.
  • the NN weights and biases will be converged after several iterations (for example, about 1e3 iterations) , and the loss expressed by the MSE function may reach about 1e-8.
  • the NN is considered to be well-trained and can be used to equalize the CDM signal for the purpose of mitigation of the channel impairments induced in the optical fronthaul link 230. Since the equalized CDM signal has been repeated by 64 times, the CD-DM 243 applies code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels.
  • MIMO demodulation, OFDM demodulation and one-tap equalization may also be implemented one by one to recover the user data.
  • FIG. 3 shows a signaling chart illustrating a training process for the fronthaul network according to some example embodiments of the present disclosure.
  • the aggregator 220 transmits 305 a CDM signal inserted with a pilot sequence for training the NN-based equalizer 242 at the BBU 240.
  • the BBU 240 performs 310 the NN training on the equalizer 242 until the stop criterion is met.
  • the aggregator 220 then transmits 315 further CDM signals to the BBU 240.
  • the BBU 240 monitors 320 at least one equalization performance of the decoded signals. For example, the BBU 240 may determine whether at least one performance of interest meets a predetermined requirement (e.g., exceeding a predefined threshold and so on) .
  • the BBU 240 determines 325 the performance is below the predefined threshold, the BBU 240 transmits 330 a training pilot request for triggering NN training.
  • the aggregator 220 may generate 325 the CDM signals inserted with the training pilot sequence.
  • the aggregator 220 then transmits 340 the CDM signal to the BBU 240.
  • the BBU 240 may perform 345 the NN training on the equalizer 242 based on the pilot sequence in an iterative manner, until the stop criterion is met.
  • the stop criterion may be at least one equalization performance of the equalizer 242 meeting a predetermined requirement, for example, exceeding a predetermined threshold.
  • the stop criterion may be the training has been performed for a predetermined number of iterations.
  • FIG. 4 illustrates a simulation result of EVM performance versus the received optical power based on the fronthaul communication scheme according to some example embodiments of the present disclosure.
  • the NN-based equalizer according to the example embodiments can effectively mitigate the channel-incurred linear and nonlinear distortions and improve the receiving sensitivity by ⁇ 1 dB and ⁇ 3 dB at the EVM threshold of 8%and 6%.
  • FIG. 4 also shows the simulation results of two different kinds of signal as the training pilot, i.e., CDM signal and OOK signal. It can be found that no obvious performance difference is observed, which indicates the feasibility of OOK-formatted training pilot.
  • a group of data streams to be delivered to the UEs at RRHs 210-1 to 210-n may be transmitted from core network.
  • the group of data streams may be firstly up-converted to IF band.
  • the CDM 244 at the BBU 240 applies code division multiplexing on each of the group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel.
  • the CDM 244 repeats each of the samples by M times, where M is the code length of Walsh codes, and then multiplies each of the repeated samples by a corresponding set of first Walsh code. After the code division multiplexing, the CDM 244 aggregates the group of coded signals corresponding to the respective wireless channels into the CDM signal.
  • the equalizer 242 may pre-equalize the CDM signal in terms of at least one equalization performance of interest.
  • the equalizer 242 may have been well-trained based on the training data (e.g., the training pilot sequence) .
  • the equalized CDM signal is obtained.
  • the DAC 242 converts the equalized CDM signal to an analog CDM signal that is to be delivered in the optical fronthaul link 230 (which may be also referred to as a third signal hereinafter) .
  • the third signal is sampled by the second ADC 224 in the aggregator 220, so as to obtain a digital CDM signal.
  • the CD-DM 225 in the aggregator 220 applies code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels.
  • the fourth orthogonal codes correspond to the third orthogonal codes.
  • the CD-DM 225 may divide the digital CDM signal into the predetermined number of parts, and multiply each part of the digital CDM signal by the respective set of the fourth orthogonal codes to obtain the group of CD-DM signals.
  • the group of DACs 226-1 to 226-n then convert the group of CD-DM signals to a group of analog CD-DM signals to be delivered in the respective wireless channels.
  • the group of analog CD-DM signals may be then converted from the IF band to the RF band by down-conversion, and transmitted to the RRH 210 via coper cables.
  • the group of analog baseband signals received by the RRH 210 may be converted from the RF band to the IF band by up-conversion units 214-1 to 214-n. As a result, a group of second wireless signals are obtained and transmitted to the end users via antennas at the RRH 210.
  • the system parameters/configurations as well as the number of devices and units in the example embodiments described in connection with FIGs. 2A and 2B are given in illustrative purpose without any limitations of the scope of the present disclosure.
  • the fronthaul communication mechanism provided according to the example embodiments can be implemented by using any other system parameters or settings.
  • the network system of the example embodiments may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Address (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency-Division Multiple Access (OFDMA) network, a Single Carrier-Frequency Division Multiple Access (SC-FDMA) network, an O-RAN compliant network or any other.
  • CDMA Code Division Multiple Access
  • TDMA Time Division Multiple Address
  • FDMA Frequency Division Multiple Access
  • OFDMA Orthogonal Frequency-Division Multiple Access
  • SC-FDMA Single Carrier-Frequency Division Multiple Access
  • O-RAN Open RAN, or ORAN
  • Open RAN defines, for example, open interfaces between network elements.
  • O-RAN architecture for example enables baseband unit and radio unit components from different vendors to operate together.
  • Communications discussed in the network shown in FIG. 2A, that is, the UL transmission scenario 201 and in FIG. 2B, that is, the DL transmission scenario 202 may conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like.
  • NR New Radio Access
  • LTE Long Term Evolution
  • LTE-A LTE-Evolution
  • WCDMA Wideband Code Division Multiple Access
  • CDMA Code Division Multiple Access
  • GSM Global System for Mobile Communications
  • the communications may be performed according to any generation communication protocols either currently known or to be developed in the future.
  • Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) , a future sixth generation communication protocols.
  • the techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies.
  • a fronthaul communication mechanism enhanced by CDM and NN-based solutions.
  • A-RoF scheme is utilized for enabling high capacity, since it can converge tens of wireless baseband signals with high spectral efficiency.
  • the aggregator of the fronthaul system encodes the signals based on CDM, thus reducing the complexity and cost.
  • the CDM can provides a relatively large tolerance to power fading caused by chromatic dispersion (CD) in fiber and a high coding gain.
  • the equalizer at the BBU can be trained based on NN technique in advance or during operating. Accordingly, high performance gain is brought by NN-enabled equalizer. This provides an easy implementation and low cost, since complex computation is conducted by the BBU pool and only a length of NRZ data is inserted into the transmitted signal at the aggregator. Last but not least, since the fiber-based optical channel is very stable and the well-trained NN can be used for a long time, the proposed mechanism is benefit from low overhead.
  • FIG. 5 illustrates a flowchart of an example method 500 of fronthaul communication according to some example embodiments of the present disclosure.
  • the method 500 can be implemented at an aggregator, for example, the aggregator 220 as shown in FIG. 2A, or any other network device of the fronthaul network.
  • the process 500 relates the uplink transmissions in the fronthaul network, and may involve the RRHs 210, the aggregator 220, the optical fronthaul link 230, and the BBU pool 240.
  • the process 500 will be described with reference to FIG. 2A.
  • the aggregator 220 converts a group of first wireless signals to a group of first signals corresponding to respective wireless channels.
  • the aggregator 220 applies code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels.
  • the aggregator 220 aggregates the group of coded signals into a CDM signal.
  • the aggregator 220 may repeat each of the first signals by a predetermined number of times.
  • the predetermined number corresponds to a length of the respective set of first orthogonal codes.
  • the aggregator 220 may then multiply each repeated first signal by the respective set of the first orthogonal codes to obtain the group of coded signals.
  • the aggregator 220 may multiplex the group of coded signals into the CDM signal.
  • the aggregator 220 may insert a pilot sequence into the CDM signal for training the equalizer 242 in the BBU 240 configured for receiving an uplink signal (e.g., the second signal) or transmitting a downlink signal (e.g., a third signal) .
  • the pilot sequence may include, but not limited to, CDM pilot signals, NRZ-OOK signals and so on.
  • the pilot sequence may be inserted in response to a training pilot request from the BBU 240.
  • the BBU 240 may transmit the training pilot request to the aggregator 220.
  • the aggregator 220 may insert the training pilot sequence at the beginning of the CDM signals generated in the CDM 222.
  • the NN-based equalizer 242 at the BBU 240 will be trained based on the pilot sequence in an iterative manner, until a stop criterion is met.
  • the stop criterion may be at least one equalization performance of the equalizer 242 meeting a predetermined requirement, for example, exceeding a predetermined threshold.
  • the stop criterion may be the training has been performed for a predetermined number of iterations. It should be understood that any other criterion for stopping the iteration can also be used for the example embodiments. Hence, the present disclosure is not limited in this regard.
  • the aggregator 220 converts the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link.
  • the CDM signal may converted by the DAC 223 in the aggregator 220 to the second signal, and thus the second signal is the analog CDM signal.
  • the second signal is to be processed by the BBU 240 of the fronthaul network based on a code division de-multiplexing with second orthogonal codes corresponding to the first orthogonal codes.
  • the first orthogonal codes and the second orthogonal codes may be preconfigured at the aggregator 220.
  • the aggregator 220 may transmit a first code-channel comparison table to the BBU 240 for determining the first orthogonal codes and the second orthogonal codes.
  • the BBU 240 can perform the code division multiplexing and code division de-multiplexing based on the first and second orthogonal codes accordingly.
  • FIG. 6 illustrates a flowchart of an example method 600 of fronthaul communication according to some example embodiments of the present disclosure.
  • the method 600 can be implemented at a BBU, for example, the BBU pool 240 as shown in FIG. 2A, or any other network device of the fronthaul network.
  • the process 600 relates the uplink transmissions in the fronthaul network, and may involve the RRHs 210, the aggregator 220, the optical fronthaul link 230, and the BBU pool 240.
  • the process 600 will be described with reference to FIG. 2A.
  • the BBU 240 converts a second signal delivered in the optical fronthaul link 230 to a CDM signal.
  • the second signal received from the aggregator 220 may be an analog CDM signal, and it has been processed by the aggregator 220 of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels.
  • the incoming second signal may be converted by the ADC 241 in the BBU 240 to a digital CDM signal.
  • the code division multiplexing applied by the aggregator 220 is described in connection with FIG. 5.
  • the BBU 240 equalizes the CDM signal in terms of at least one equalization performance.
  • the CDM signal may be equalized by the NN-based equalizer 242 in the BBU 240.
  • the NN-based equalizer 242 may have been trained based on training pilot sequence.
  • a pilot sequence may be inserted into the CDM signal for training at least one equalization performance of the equalizer 242 in the BBU 240.
  • the equalizer may be a NN-based equalizer configured to be trained based on the pilot sequence in an iterative manner, until a stop criterion is met.
  • the stop criterion may be at least one equalization performance meeting a predetermined requirement, for example, a predetermined threshold.
  • the stop criterion may be the training has been performed for a predetermined number of iterations. It should be understood that any other criterion for stopping the iteration can also be used for the example embodiments. Hence, the present disclosure is not limited in this regard.
  • the NN training is implemented with the training data and the NN weights and biases are generated.
  • the NN is configured with the well-trained NN parameters and sequentially used to equalize the payload signal.
  • the BBU 240 may monitor the at least one equalization performance of the equalized CDM signal, which may be implemented by a controller of the BBU 240.
  • the BBU 240 may transmit a training pilot request to the aggregator 220.
  • the aggregator 220 may transmit the CDM signal inserted with a pilot sequence.
  • the pilot sequence may include, but not limited to, CDM pilot signals, NRZ-OOK signals and so on.
  • the BBU 240 will obtain the CDM signal inserted with the pilot sequence for training the equalizer 242 in terms of the at least one equalization performance.
  • the BBU 240 applies code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels.
  • the second orthogonal codes correspond to the first orthogonal codes.
  • the code division de-multiplexing may be implemented by the CD-DM 243 in the BBU 240.
  • the CD-DM 243 may divide the equalized CDM signal into a predetermined number of parts, and the predetermined number corresponds to a length of a respective set of second orthogonal codes.
  • the CD-DM 243 may then multiply each part of the equalized CDM signal by the respective set of the second orthogonal codes to obtain the group of CD-DM signals.
  • the first orthogonal codes and the second orthogonal codes may be preconfigured at the aggregator 220.
  • the BBU 240 may receive a first code-channel comparison table from the aggregator 220, and the code-channel comparison table is configured for determining the first orthogonal codes and the second orthogonal codes.
  • a fronthaul system may include the aggregator 220, the BBU 240 and the optical fronthaul link that connects the aggregator 220 and the BBU 240.
  • an enhanced communication mechanism for fronthaul link in 5G and beyond wireless communication systems CDM aggregation/de-aggregation can be employed by the aggregator and BBU of the fronthaul network.
  • the equalization in the BBU can be implemented by means of neural network. In this way, the proposed solution is able to provide the superiorities of high capacity, low cost, easy implementation and large tolerance to channel impairments.
  • FIG. 7 illustrates a flowchart of an example method 700 of fronthaul communication according to some example embodiments of the present disclosure.
  • the method 800 can be implemented at a BBU, for example, the BBU pool 240 as shown in FIG. 2B, or any other network device of the fronthaul network.
  • the process 700 relates to the downlink transmissions in the fronthaul network, and may involve the RRHs 210, the aggregator 220, the optical fronthaul link 230, and the BBU pool 240.
  • the process 700 will be described with reference to FIG. 2B.
  • the BBU 240 applies code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels.
  • the code division multiplexing may be implemented by the CDM 244 in the BBU 240.
  • the CDM 244 may repeat each of a group of data streams by a predetermined number of times, and the predetermined number corresponds to a length of the respective set of third orthogonal codes.
  • the CDM 244 may multiply each repeated data stream by the respective set of the third orthogonal codes to obtain the group of coded signals.
  • the CDM 244 may multiplex the group of coded signals into a CDM signal.
  • the BBU 240 aggregates the group of coded signals into a CDM signal.
  • the BBU 240 pre-equalizes the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal.
  • the BBU 240 converts the equalized CDM signal to a third signal to be delivered in the optical fronthaul link 230.
  • the third signal is to be processed by the aggregator 220 of the fronthaul network based on a code division de-multiplexing with fourth orthogonal codes corresponding to the third orthogonal codes.
  • the third orthogonal codes and the fourth orthogonal codes may be preconfigured at the aggregator 220.
  • the BBU 240 may receive a second code-channel comparison table from the aggregator 220, and second the code-channel comparison table is configured for determining the third orthogonal codes and the fourth orthogonal codes.
  • different code division multiplexing schemes are used in UL and DL transmissions.
  • the first code-channel comparison table used for UL transmissions may be different from the second code-channel comparison table used for DL transmissions.
  • the first orthogonal codes may be different from the third orthogonal codes, and accordingly, the second orthogonal codes are also different from the fourth orthogonal codes.
  • FIG. 8 illustrates a flowchart of an example method 800 of fronthaul communication according to some example embodiments of the present disclosure.
  • the method 800 can be implemented at an aggregator, for example, the aggregator 220 as shown in FIG. 2B, or any other network device of the fronthaul network.
  • the process 800 relates to the downlink transmission in the fronthaul network, and may involve the RRHs 210, the aggregator 220, the optical fronthaul link 230, and the BBU pool 240.
  • the process 800 will be described with reference to FIG. 2B.
  • the aggregator 220 converts a third signal delivered in the optical fronthaul link 230 to a digital CDM signal.
  • the third signal may have been processed by the BBU 240 of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels.
  • the code division multiplexing applied by the BBU 240 are described in connection with FIG. 7.
  • the aggregator 220 applies code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels.
  • the fourth orthogonal codes correspond to the third orthogonal codes.
  • the code division de-multiplexing may be implemented by the CD-DM 243 in the aggregator 220.
  • the CD-DM 243 may divide the digital CDM signal into a predetermined number of parts, and the predetermined number may correspond to a length of a respective set of fourth orthogonal codes.
  • the CD-DM 243 may multiply each part of the digital CDM signal by the respective set of the fourth orthogonal codes to obtain the group of CD-DM signals.
  • the aggregator 220 converts the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • the third orthogonal codes and the fourth orthogonal codes may be preconfigured at the aggregator 220.
  • the aggregator 220 may transmit a second code-channel comparison table to the BBU 240 for determining the third orthogonal codes and the fourth orthogonal codes.
  • the BBU 240 can perform the code division multiplexing and code division de-multiplexing based on the third and fourth orthogonal codes accordingly.
  • different code division multiplexing schemes are used in UL and DL transmissions.
  • the first code-channel comparison table used for UL transmissions may be different from the second code-channel comparison table used for DL transmissions.
  • the first orthogonal codes may be different from the third orthogonal codes, and accordingly, the second orthogonal codes are also different from the fourth orthogonal codes.
  • an enhanced communication mechanism for optical fronthaul link in 5G and beyond wireless communication systems the aggregator of the fronthaul network assigns dedicated Walsh codes to different wireless signals and sends the corresponding code-channel comparison table to the BBU through control channel.
  • the BBU can configure corresponding different Walsh codes for code division de-multiplexing.
  • the performance of received signal can be constantly monitored.
  • the BBU may transmit a training pilot request to the aggregator.
  • the aggregator can transmit the training sequence with CDM format or NRZ format.
  • the NN training is implemented at the equalizer of BBU with the training data, and the NN weights and biases are generated.
  • the NN will be configured with the well-trained NN parameters and sequentially used to equalize the payload signal. In this way, high performance gain can be brought by the NN-enabled equalizer.
  • only a length of NRZ data is inserted into the transmitted signal at aggregator, and relatively complex computations are performed by the BBU pool, thus the mechanism can be easily implemented with low cost.
  • FIG. 9 is a simplified block diagram of a device 900 that is suitable for implementing embodiments of the present disclosure.
  • the device 900 may be provided to implement the communication device, for example the aggregator 220, and the BBU 240 as shown in FIGs. 2A and 2B.
  • the device 900 includes one or more processors 910, one or more memories 920 coupled to the processor 910, and one or more transmitters and/or receivers (TX/RX) 940 coupled to the processor 910.
  • TX/RX transmitters and/or receivers
  • the TX/RX 940 may be configured for bidirectional communications.
  • the TX/RX 940 has at least one antenna to facilitate communication.
  • the communication interface may represent any interface that is necessary for communication with other network elements.
  • the processor 910 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples.
  • the device 900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.
  • the memory 920 may include one or more non-volatile memories and one or more volatile memories.
  • the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 924, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage media.
  • the volatile memories include, but are not limited to, a random access memory (RAM) 922 and other volatile memories that will not last in the power-down duration.
  • a computer program 930 includes computer executable instructions that may be executed by the associated processor 910.
  • the program 930 may be stored in the ROM 924.
  • the processor 910 may perform any suitable actions and processing by loading the program 930 into the RAM 922.
  • the embodiments of the present disclosure may be implemented by means of the program 930 so that the device 900 may perform any process of the disclosure as discussed with reference to FIG. 3.
  • the embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.
  • the program 930 may be tangibly contained in a computer readable medium which may be included in the device 900 (such as in the memory 920) or other storage devices that are accessible by the device 900.
  • the device 900 may load the program 930 from the computer readable medium to the RAM 922 for execution.
  • the computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like.
  • FIG. 10 shows an example of the computer readable medium 1000 in form of CD or DVD.
  • the computer readable medium has the program 1030 stored thereon.
  • Various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations. It is to be understood that the block, device, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
  • the present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium.
  • the computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 500, 600, 700 or 800 as described above with reference to FIGs. 5-8.
  • program modules may include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types.
  • the functionality of the program modules may be combined or split between program modules as desired in various embodiments.
  • Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.
  • Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing device, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented.
  • the program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.
  • the computer program codes or related data may be carried by any suitable carrier to enable the device, device or processor to perform various processes and operations as described above.
  • Examples of the carrier include a signal, computer readable medium, and the like.
  • the computer readable medium may be a computer readable signal medium or a computer readable storage medium.
  • a computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
  • an aggregator of a fronthaul network comprises a group of first analog-to-digital convertors (ADCs) , a code division multiplexer (CDM) and a first digital-to-analog (DAC) .
  • the group of first ADCs is coupled to the CDM, and configured to convert a group of first wireless signals to a group of first signals corresponding to respective wireless channels.
  • the CDM is coupled to a first digital-to-analog, DAC, and configured to apply code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; and aggregate the group of coded signals into a code division multiplexed, CDM, signal.
  • the first DAC is configured to convert the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link.
  • the CDM is configured to apply the code division multiplexing by: repeating each of the first signals by a predetermined number of times, the predetermined number corresponding to a length of the respective set of first orthogonal codes; and multiplying each repeated first signal by the respective set of the first orthogonal codes to obtain the group of coded signals; and multiplexing the group of coded signals into the CDM signal.
  • the second signal is to be processed by a base band unit, BBU, of the fronthaul network based on a code division de-multiplexing with second orthogonal codes corresponding to the first orthogonal codes.
  • BBU base band unit
  • the aggregator further comprises a second ADC coupled to a code division de-multiplexer, CD-DM, and configured to convert a third signal delivered in the optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels;
  • the CD-DM coupled to a group of second DACs, and configured to: apply code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; and the group of second DACs configured to convert the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • the CD-DM is configured to apply the code division de-multiplexing by: dividing the digital CDM signal into a predetermined number of parts, the predetermined number corresponding to a length of a respective set of fourth orthogonal codes; and multiplying each part of the digital CDM signal by the respective set of the fourth orthogonal codes to obtain the group of CD-DM signals.
  • the first and second orthogonal codes and the third and fourth orthogonal codes are preconfigured at the aggregator, and the aggregator is further configured to: transmit a first code-channel comparison table to the BBU for determining the first orthogonal codes and the second orthogonal codes; and transmit a second code-channel comparison table to the BBU for determining the third orthogonal codes and the fourth orthogonal codes.
  • the CDM is further configured to: insert a pilot sequence into the CDM signal for training an equalizer in a baseband unit, BBU of the fronthaul network, the BBU being configured for receiving the second signal or transmitting the third signal.
  • the aggregator further comprises a second ADC coupled to a code division de-multiplexer, CD-DM, and configured to convert a third signal delivered in the optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels;
  • the CD-DM coupled to a group of second DACs, and configured to: apply code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; and the group of second DACs configured to convert the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • the first and second orthogonal codes and the third and fourth orthogonal codes are preconfigured at the aggregator, and the aggregator is further configured to: transmit a first code-channel comparison table to the BBU for determining the first orthogonal codes and the second orthogonal codes; and transmit a second code-channel comparison table to the BBU for determining the third orthogonal codes and the fourth orthogonal codes.
  • the CDM is further configured to: insert a pilot sequence into the CDM signal for training an equalizer in a baseband unit, BBU of the fronthaul network, the BBU being configured for receiving the second signal or transmitting the third signal.
  • the pilot sequence comprises CDM pilot signals or non-return zero on-off keying, NRZ-OOK, signals.
  • the pilot sequence is inserted in response to a training pilot request from the BBU.
  • a BBU of a fronthaul network comprises an ADC, an equalizer and a code division de-multiplexer (CD-DM) .
  • the ADC is coupled to the equalizer, and configured to convert a second signal delivered in an optical fronthaul link to a digital CDM signal, the digital CDM signal is processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels.
  • the equalizer is coupled to the CD-DM, and configured to equalize the CDM signal in terms of at least one equalization performance.
  • the CD-DM is configured to apply code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • the CD-DM is configured to apply the code division de-multiplexing by: dividing the equalized CDM signal into a predetermined number of parts, the predetermined number corresponding to a length of a respective set of second orthogonal codes; and multiplying each part of the equalized CDM signal by the respective set of the second orthogonal codes to obtain the group of CD-DM signals.
  • the BBU further comprises: a code division multiplexer, CDM coupled to the equalizer, and configured to: apply code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; and aggregate the group of coded signals into a code division multiplexed, CDM, signal; and the equalizer is further configured to pre-equalize the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal; and a digital-to-analog convertor, DAC coupled to the equalizer, and configured to convert the equalized CDM signal to a third signal to be delivered in the optical fronthaul link.
  • CDM code division multiplexer
  • the CDM is configured to apply the code division multiplexing by: repeating each of a group of data streams by a predetermined number of times, the predetermined number corresponding to a length of the respective set of third orthogonal codes; multiplying each repeated data stream by the respective set of the third orthogonal codes to obtain the group of coded signals; and multiplexing the group of coded signals into a CDM signal.
  • the third signal is to be processed by an aggregator of the fronthaul network based on a code division de-multiplexing with fourth orthogonal codes corresponding to the third orthogonal codes.
  • the first and second orthogonal codes and the third and fourth orthogonal codes are preconfigured at the aggregator, and the BBU is further configured to: receive, from the aggregator, a first code-channel comparison table for determining the first orthogonal codes and the second orthogonal codes; and receive, from the aggregator, a second code-channel comparison table for determining the third orthogonal codes and the fourth orthogonal codes.
  • a pilot sequence is inserted into the CDM signal for training at least one equalization performance of the equalizer.
  • the equalizer comprises a neural network-based equalizer configured to be trained based on the pilot sequence in an iterative manner, until a stop criterion is met.
  • the stop criterion comprises: at least one equalization performance meets a predetermined requirement.
  • a controller configured to: in accordance with a determination that the at least one equalization performance of the equalized CDM signal is not meeting a predetermined requirement, transmit a training pilot request to the aggregator; and obtain a CDM signal inserted with a pilot sequence for training the equalizer in terms of the at least one equalization performance.
  • the pilot sequence comprises CDM pilot signals or non-return zero on-off keying, NRZ-OOK, signals.
  • the fronthaul system comprises the aggregator according to the first aspect, the BBU according to the second aspect and the optical fronthaul link connecting the aggregator with the BBU.
  • a method comprises: converting, at an aggregator of a fronthaul network, a group of first wireless signals to a group of first signals corresponding to respective wireless channels; applying code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; aggregating the group of coded signals into a code division multiplexed, CDM, signal; and converting the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link of the fronthaul network.
  • a method comprises: converting, at a baseband unit, BBU, of a fronthaul network, a second signal delivered in an optical fronthaul link of the fronthaul network to a digital code division multiplexed, CDM, signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels; equalizing the CDM signal in terms of at least one equalization performance; and applying code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • a method comprises: applying, at a baseband unit, BBU, of a fronthaul network, code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; aggregating the group of coded signals into a code division multiplexed, CDM, signal; pre-equalizing the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal; and converting the equalized CDM signal to a third signal to be delivered in the optical fronthaul link.
  • BBU baseband unit
  • a method comprises: converting, at an aggregator of a fronthaul network, a third signal delivered in the optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels; applying code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; and converting the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the above aspects.
  • an apparatus comprises means for converting, at an aggregator of a fronthaul network, a group of first wireless signals to a group of first signals corresponding to respective wireless channels; means for applying code division multiplexing on each of the first signals based on a corresponding set of first orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; means for aggregating the group of coded signals into a code division multiplexed, CDM, signal; and means for converting the CDM signal obtained from the CDM to a second signal for delivering in an optical fronthaul link.
  • an apparatus comprising means for converting, at a baseband unit, BBU, of a fronthaul network, a second signal delivered in an optical fronthaul link to a digital code division multiplexed, CDM, signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on a code division multiplexing with first orthogonal codes for respective wireless channels; means for equalizing the CDM signal in terms of at least one equalization performance; and means for applying code division de-multiplexing on the equalized CDM signal based on second orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the second orthogonal codes corresponding to the first orthogonal codes.
  • BBU baseband unit
  • an apparatus comprising means for applying, at a baseband unit, BBU, of a fronthaul network, code division multiplexing on each of a group of data streams based on a corresponding set of third orthogonal codes for a respective wireless channel, to obtain a group of coded signals corresponding to the respective wireless channels; means for aggregating the group of coded signals into a code division multiplexed, CDM, signal; means for pre-equalizing the CDM signal in terms of the at least one equalization performance to obtain an equalized CDM signal; and means for converting the equalized CDM signal to a third signal to be delivered in an optical fronthaul link.
  • BBU baseband unit
  • an apparatus comprises means for converting, at an aggregator of a fronthaul network, a third signal delivered in an optical fronthaul link to a digital CDM signal, the third signal being processed by a base band unit, BBU, of the fronthaul network based on a code division multiplexing with third orthogonal codes for respective wireless channels; means for applying code division de-multiplexing on the digital CDM signal based on fourth orthogonal codes to obtain a group of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal codes corresponding to the third orthogonal codes; means for converting the group of CD-DM signals to a group of second wireless signals to be delivered in the respective wireless channels.
  • an apparatus comprising the aggregator according to the embodiments of this disclosure.
  • the apparatus comprises the BBU according to the embodiments of this disclosure.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Des modes de réalisation de la présente divulgation se rapportent à un dispositif, un procédé, un appareil et un support de stockage lisible par ordinateur destinés à la communication de liaison frontale. Le procédé consiste : à convertir, au niveau d'un agrégateur d'un réseau de liaison frontale, un groupe de premiers signaux sans fil en un groupe de premiers signaux correspondant à des canaux sans fil respectifs ; à appliquer un multiplexage par répartition en code sur chacun des premiers signaux sur la base d'un ensemble correspondant de premiers codes orthogonaux pour un canal sans fil respectif, de manière à obtenir un groupe de signaux codés correspondant aux canaux sans fil respectifs ; à agréger le groupe de signaux codés en un signal multiplexé par répartition en code (MRC) ; et à convertir le signal MRC obtenu à partir du MRC en un second signal pour être émis dans une liaison de liaison frontale optique. Dans le mécanisme de liaison frontale, un schéma A-RoF est utilisé pour agréger et émettre les signaux de bande de base sans fil au moyen d'un MRC à faible complexité, conduisant à un système de liaison frontale à faible complexité, à faible coût et à capacité élevée. De plus, un gain haute performance peut être réalisé à l'aide de l'égaliseur activé par NN.
PCT/CN2022/093546 2022-05-18 2022-05-18 Améliorations sur un réseau de liaison frontale WO2023220965A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106788476A (zh) * 2016-12-12 2017-05-31 武汉邮电科学研究院 基于Walsh码信道聚合的移动前传装置及方法
US20200008125A1 (en) * 2018-07-02 2020-01-02 At&T Intellectual Property I, L.P. Cell site routing based on latency
CN113544976A (zh) * 2019-03-01 2021-10-22 华为技术有限公司 用于无线通信系统的并行序列噪声消除（PSiC）接收器架构
CN113574814A (zh) * 2019-04-02 2021-10-29 华为技术有限公司 用于无线通信的频谱高效正交码生成和实现方法和装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106788476A (zh) * 2016-12-12 2017-05-31 武汉邮电科学研究院 基于Walsh码信道聚合的移动前传装置及方法
US20200008125A1 (en) * 2018-07-02 2020-01-02 At&T Intellectual Property I, L.P. Cell site routing based on latency
CN113544976A (zh) * 2019-03-01 2021-10-22 华为技术有限公司 用于无线通信系统的并行序列噪声消除（PSiC）接收器架构
CN113574814A (zh) * 2019-04-02 2021-10-29 华为技术有限公司 用于无线通信的频谱高效正交码生成和实现方法和装置

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