ORAN system and its RU, and time synchronization method between RU and DU in ORAN system

Abstract

To provide an ORAN system capable of reducing at least one defect of a conventional technology.SOLUTION: The ORAN RU includes a GNSS module that generates a PPS signal every second, a crystal oscillator in which a reference oscillation frequency is set, a clock generator, and a digital counter. The clock generator defines one second with reference to the reference oscillation frequency of the crystal oscillator, and generates a drive signal and a clock pulse signal based on the defined one second. The digital counter adds 1 to a count value in response to receiving each of the clock pulse signals, reads the count value when receiving the PPS signal, determines whether the count value is equal to a value of a reference oscillation frequency and resets the count value to zero, and sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency when determining that the count value is not equal to the value of the reference oscillation frequency.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a radio access network (RAN) system and a time synchronization method in the RAN system, and more particularly to an open radio access network (open RAN, ORAN) system and a time synchronization method between radio units (RUs) and distributed units (DUs) in the ORAN system. [Background technology]

[0002] A traditional open radio access network (ORAN) basically includes radio units (RUs), distributed units (DUs), and central units (CUs). Currently, the Precision Time Protocol (PTP) defined in IEEE 1588 is commonly used to synchronize the time of various network units in an ORAN system and prevent packet loss or network interruptions.

[0003] Referring to Figure 1, taking a conventional ORAN system with an existing LLS-C1 (Lower Layer Split Type 1 Control Plane) architecture as an example, the DU91 reads a satellite synchronization signal from the telecom grandmaster (T-GM) 90 via a network interface card (NIC) 910, which conforms to the IEEE 1588 standard, by periodic request or polling. Upon receiving the satellite synchronization signal, the high-physical layer 911 of the DU91 must execute an IEEE 1588 algorithm to estimate time and frequency using network packets. The fronthaul switch 92 for data transmission and routing between the DU91 and the RU93 must perform network packet delay calculations, while the RU93 must execute other IEEE 1588 algorithms to fine-tune the frequency of its crystal oscillator (e.g., an oven-controlled crystal oscillator (OCXO)) to ensure accurate time synchronization. These components work together to ensure clock synchronization between the DU91 and the RU93. Furthermore, the High-PHY layer 911 and the Medium Access Control (MAC) layer 912 of the DU91 must each read the timestamp from the NIC 910 and each allocate a logical core to generate synchronized network packets, thereby facilitating task scheduling in a time-synchronized state.

[0004] Although the above architecture can achieve the purpose of timing and time synchronization, both the T-GM90 and the fronthaul switch 92 are very expensive, and the NIC910 of the DU91 must comply with the standard defined in IEEE 1588. In other words, all hardware components and software applications in the ORAN system must comply with the standard defined in IEEE 1588, which results in limitations and high costs for network products such as small cell base stations. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Chinese Patent Publication No. 1207616 Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide an Open Radio Access Network (ORAN) system that can alleviate at least one of the drawbacks of the prior art. [Means for solving the problem]

[0007] According to the present invention, the ORAN system includes a Radio Unit (RU) and a Distributed Unit (DU).

[0008] The RU includes a Global Navigation Satellite System (GNSS) module that generates a pulse per second (PPS) signal every second, a quartz crystal oscillator that sets the reference oscillation frequency, a clock generator, a digital counter, and a slot tick module.

[0009] The clock generator defines one second based on the reference oscillation frequency of the crystal oscillator, generates a drive signal with a drive frequency based on the defined one second, and repeatedly generates a clock pulse signal with the reference oscillation frequency.

[0010] The digital counter receives clock pulse signals from the clock generator, and adds 1 to the count value in response to receiving each clock pulse signal; receives a PPS signal from the GNSS module every second; upon receiving the PPS signal, reads the count value, determines whether the read count value is equal to the value of the reference oscillation frequency, and resets the count value to zero; if it determines that the read count value is not equal to the value of the reference oscillation frequency, it sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency.

[0011] The slot tick module receives the driving signal and transmits slot tick packets of the driving frequency. The DU performs task scheduling according to the slot tick packets.

[0012] Another object of the present invention is to provide a RU for the above ORAN system.

[0013] It is yet another object of the present invention to provide a method for time synchronization between an RU and a DU in an ORAN system, which is executed by the ORAN system.

[0014] The ORAN system includes a RU and a DU. The RU includes a GNSS module, a crystal oscillator, a clock generator, a digital counter, and a slot tick module.

[0015] The time synchronization method between RU and DU in the ORAN system is that the GNSS module sends PPS (pulse per second) every second. the digital counter receives a PPS signal from the GNSS module every second, and upon receiving the PPS signal, reads the count value, determines whether the read count value is equal to the value of the reference oscillation frequency, and resets the count value to zero; if the digital counter determines that the read count value is not equal to the value of the reference oscillation frequency, sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency; the slot tick module receives the drive signal and sends a slot tick packet of the drive frequency; and the DU performs task scheduling according to the slot tick packet. [Effects of the Invention]

[0016] The structure disclosed in this invention uses a GNSS module instead of an expensive Telecom Grandmaster (T-GM), eliminating the need to comply with the standards defined by IEEE 1588, and instead uses a digital counter and clock generator to perform specific processing and achieve time synchronization.

[0017] Other features and advantages of the present invention will become apparent from the following detailed description of the embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 1 is a block diagram illustrating a conventional Open Radio Access Network (ORAN) system that performs synchronization of Distributed Units (DUs) and Radio Units (RUs) by reading radio satellite signals from a Telecom Grand Master (T-GM). [Figure 2] FIG. 1 is a block diagram illustrating an ORAN system according to an embodiment of the present invention. [Figure 3] FIG. 2 is a block diagram illustrating a RU in an ORAN system. [Figure 4] 1 is a flowchart of a method for time synchronization between an RU and a DU in an ORAN system according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Before describing the present invention in more detail, it should be noted that, where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or similar elements that may have similar characteristics.

[0020] Referring to Figure 2, an open radio access network (ORAN) system 100 according to one embodiment of the present invention includes a radio unit (RU) 2 and a central / distributed unit (CDU) 1 that integrates a central unit (CU) and a distributed unit (DU). The CDU 1 and RU 2 are housed together in a box and form a small cell. In some embodiments, the CDU 1 and RU 2 are located in different locations and transmit data to each other, for example, via an evolved Common Public Radio Interface (eCPRI) over Ethernet. In some embodiments, the CU and DU are independent devices.

[0021] In this embodiment, the CDU 1 includes a medium access control (MAC) layer 11 for medium access control, a High-PHY layer 12, and a network interface card (NIC) 13.

[0022] 3, in addition to the antenna (not shown) and radio frequency (RF) unit 21 that an RU typically includes, the RU 2 of this embodiment further includes a global navigation satellite system (GNSS) module and a field programmable gate array (FPGA) module 23. In this embodiment, the GNSS module is a global positioning system (GPS) module 22 that receives GPS satellite signals for use as a precise reference clock. In some embodiments, the GNSS module may be a GLONASS module, a Galileo module, a BeiDou satellite navigation system module, or a NavIC navigation satellite system module.

[0023] The FPGA module 23, which was customized and developed using FPGA technology, includes a Low-PHY layer 231 used to collect in-phase and quadrature-phase data (IQ data) from the RF module 21, a high-speed Ethernet interface 232 that receives the IQ data from the Low-PHY layer 231, a digital counter 233, and a slot tick module 234 used to synchronize time slots using network packets. The high-speed Ethernet interface 232 is compliant with, but not limited to, 10 Gigabit Ethernet. In this embodiment, the FPGA module 23 is designed and implemented using FPGA technology. FPGA technology enables the designed module functions (described in detail below) to be executed in parallel and at high speed, thereby controlling timing more precisely.

[0024] According to this embodiment, RU2 further includes a crystal oscillator 24 and a clock generator 25. The crystal oscillator 24 and the clock generator 25, in cooperation with the GPS module 22 and the FPGA module 23, jointly perform time synchronization between CDU1 and RU2 in the ORAN system 100. The crystal oscillator 24 is, for example, a voltage-controlled temperature-compensated crystal oscillator (VCTCXO), but is not limited to this, and may be other crystal oscillators such as a voltage-controlled crystal oscillator (VCXO) or an oven-controlled crystal oscillator (OCXO).

[0025] 3 and 4, a method for time synchronization between an RU and a DU in an ORAN system according to one embodiment of the present invention is performed by the aforementioned ORAN system 100. The present invention mainly uses a GPS module 22 instead of the T-GM90 (see FIG. 1) of the conventional ORAN system, eliminating the need to comply with the standard defined by IEEE 1588, and achieves time synchronization by working with an RU2 and a CDU1 to perform the following steps:

[0026] In step S11, the GPS module 22 generates a PPS (pulse per second) signal every second in accordance with the received GPS satellite signal. Furthermore, a reference oscillation frequency is set in the crystal oscillator 24 (step S12). Here, the value of the reference oscillation frequency is a default value V, which is, for example, 52×10 6 However, the present invention is not limited to this.

[0027] In step S13, the clock generator 25 defines one second based on the reference oscillation frequency of the crystal oscillator 24 (in this example, 52×10 6 Based on the defined 1 second, a drive signal with a drive frequency of V0 Hz is generated, and the drive signal serves as a reference clock for the entire ORAN system 100. In this example, V0 is 2 n where n is a positive integer. That is, the driving frequency is 2 n Hz. The following is shown for the case where n is 2, which means that the oscillation frequency is equal to 4 Hz and the clock generator 25 generates a drive signal every 0.25 seconds. In other embodiments, V may be 2, 8, etc. Furthermore, the clock generator 25 repeatedly generates a clock pulse signal at the reference oscillation frequency of the quartz oscillator 24 (step S14).

[0028] In step S15, the digital counter 233 receives clock pulse signals from the clock generator 25, and adds 1 to the count value in response to each received clock pulse signal. Specifically, the digital counter 233 adds 1 to the count value when detecting each rising edge of the clock pulse signal. Furthermore, the digital counter 233 receives a PPS signal from the GPS module 22 every second, and upon receiving the PPS signal, reads the count value (step S16), determines whether the read count value is equal to the value of the reference vibration frequency (step S18), and resets the count value to zero (step S17).

[0029] In step S19, if the read count value is not equal to the value of the reference vibration frequency, the digital counter 233 sends a vibration frequency adjustment signal to the crystal oscillator 24 to adjust the reference vibration frequency. Specifically, if the value of the reference vibration frequency is 52×10 6 For example, if the count value is 52 x 10 6 If the count value is greater than 52×10, the digital counter 233 sends an oscillation frequency adjustment signal to the crystal oscillator 24 to lower the reference oscillation frequency by, for example, 1 Hz. 6 If the count value is smaller than 52×10, the digital counter 233 sends an oscillation frequency adjustment signal to the crystal oscillator 24 to increase the reference oscillation frequency by, for example, 1 Hz. 6 , the digital counter 233 does not send an oscillation frequency adjustment signal, and the crystal oscillator 24 does not need to adjust the reference oscillation frequency.

[0030] When the crystal oscillator 24 receives the oscillation frequency adjustment signal, the flow returns to step S12, and the reference oscillation frequency is set in the crystal oscillator 24. For example, if the current value of the reference oscillation frequency is V1, and the oscillation frequency adjustment signal is received, the value of the reference oscillation frequency is adjusted from V1 to V2, which is different from V1. For example, the value V1 of the reference oscillation frequency is 52×10 of the default value V. 6The count value read by the digital counter 233 is 52×10 6 In the larger case, the crystal oscillator 24 has a reference oscillation frequency of 52×10 6 From 52 x 10 6 The count value read by the digital counter 233 is adjusted to 52×10 6 In the smaller case, the crystal oscillator 24 has a reference oscillation frequency of 52×10 6 From 52 x 10 6 The clock generator 25 generates a drive signal and a clock pulse signal in accordance with the adjusted reference oscillation frequency.

[0031] This allows RU2 to synchronize with GPS satellite signals. Even if the GPS module 22 cannot receive GPS signals due to bad weather, RU2 can independently correct its time and maintain accuracy for a certain period of time.

[0032] In step S21, the slot tick module 234 receives a drive signal with a drive frequency of V0 Hz and transmits a slot tick packet with a drive frequency of V0 Hz to the high-speed Ethernet interface 232. The slot tick packet is a network packet transmitted during each time slot and includes frame slot information, which indicates, for example, how time slots are allocated for data reception or transmission. In step S22, the high-speed Ethernet interface 232 transmits the IQ data from the low-PHY layer 231 and the slot tick packet from the slot tick module to the CDU1. Specifically, the NIC 13 receives the IQ data and the slot tick packet from the high-speed Ethernet interface 232 of the RU2. In step S23, the high-PHY layer 12 of the CDU1 performs task scheduling according to the slot tick packet. Specifically, the high-PHY layer 12 generates ticks based on the slot tick packet to perform task scheduling.

[0033] Regarding slot tick packets, taking the DDDSU (downlink, downlink, downlink, special, uplink) frame structure as an example, the frame has 20 slots, and five consecutive slots form one cycle, with four cycles in the frame. The five consecutive slots in each cycle are three downlink slots, one pending slot, and one uplink slot. According to this structure, the CDU1 performs uplink and downlink transmission under precise timing control.

[0034] Since RU2 is time-synchronized via GPS satellite signals as described above (steps S11 to S19), the clock generator 25 generates a drive signal with a drive frequency of V0 Hz based on the accurate time for the slot tick module 234 to execute step S21, thereby achieving time synchronization between RU2 and CDU1.

[0035] In summary, the structure disclosed in this invention eliminates the need for an expensive telecom grandmaster (T-GM), eliminates the need for the NIC 13 of the CDU 1 to comply with the IEEE 1588 standard, and eliminates the need for the MAC layer 11 and High-PHY layer 12 of the CDU 1 to allocate dedicated logic cores for time synchronization. Instead, the GPS module 22 is integrated into the RU 2, and the digital counter 233 and clock generator 25 perform specific processing to achieve time synchronization.

[0036] In the above description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that one or more other embodiments may be practiced without these specific details. Furthermore, in the description of "one embodiment" or "an embodiment" herein, all references to an ordinal number or other designation should be understood to include specific aspects, structures, and features of the present invention. Furthermore, although multiple variations may be incorporated into a single embodiment, drawing, or description thereof, this is for the purpose of streamlining the description and for the purpose of understanding the multifaceted aspects of the present invention. Furthermore, one or more features or specific embodiments of one embodiment may, where appropriate, be combined with one or more features or specific embodiments of other embodiments in the practice of the present invention.

[0037] Although the embodiments and variations of the present invention have been described above, the present invention is not limited to these and encompasses all modifications and equivalent configurations as various configurations falling within the spirit and scope of the broadest interpretation. [Explanation of symbols]

[0038] 100 Open Radio Access Network (ORAN) Systems 1 Central Distributed Unit (CDU) 11 Medium Access Control (MAC) Layer 12 High-PHY Layer 13 Network Interface Card (NIC) 2 Radio Units (RU) 21 RF Module 22 GPS module 23 FPGA modules 231 Low-PHY Layer 232 high-speed Ethernet interface 233 Digital Counter 234 Slottic Module 24 crystal oscillator 25 Clock Generator S11~S19 steps S21~S23 steps

Claims

1. a radio unit (RU) and a distributed unit (DU); The RU is a Global Navigation Satellite System (GNSS) module that generates a pulse per second (PPS) signal every second; a quartz crystal unit for setting a reference oscillation frequency; a clock generator that defines one second based on the reference oscillation frequency of the crystal oscillator, generates a drive signal with a drive frequency based on the defined one second, and repeatedly generates a clock pulse signal with the reference oscillation frequency; a digital counter that receives the clock pulse signal from the clock generator, adds 1 to a count value in response to receiving each of the clock pulse signals, receives the PPS signal from the GNSS module every second, reads the count value upon receiving the PPS signal, determines whether the read count value is equal to the value of the reference oscillation frequency, and resets the count value to zero, and sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency if it determines that the read count value is not equal to the value of the reference oscillation frequency; a slot tick module receiving the drive signal and transmitting slot tick packets of the drive frequency; The DU performs task scheduling according to the slot tick packet. Open Radio Access Network (ORAN) system.

2. When the count value read by the digital counter is greater than the value of the reference vibration frequency, the digital counter sends the vibration frequency adjustment signal to the crystal oscillator to lower the reference vibration frequency by 1 Hz. The ORAN system of claim 1 .

3. When the read count value is smaller than the value of the reference vibration frequency, the digital counter sends the vibration frequency adjustment signal to the crystal oscillator to increase the reference vibration frequency by 1 Hz. The ORAN system of claim 1 .

4. the digital counter increments the count value by one upon detecting each rising edge of the clock pulse signal; The ORAN system of claim 1 .

5. The driving frequency is 2 n Hz, and n is a positive integer. The ORAN system of claim 1 .

6. The RU further includes a radio frequency (RF) module and a low-PHY layer; The Low-PHY layer is used to collect in-phase and quadrature data (IQ data) from the RF module; The ORAN system of claim 1 .

7. the RU further includes a high-speed Ethernet interface; The high-speed Ethernet interface transmits the IQ data from the Low-PHY layer and the slot tick packet from the slot tick module to the DU; The ORAN system of claim 6.

8. The DU is a network interface card (NIC) that receives the IQ data and the slot tick packets from the fast Ethernet interface of the RU; a High-PHY layer that generates ticks based on the slot tick packets to perform the task scheduling; The ORAN system of claim 7.

9. Implemented by an open radio access network (ORAN) system including a radio unit (RU) and a distributed unit (DU); the RU includes a Global Navigation Satellite System (GNSS) module, a quartz crystal oscillator, a clock generator, a digital counter, and a slot tick module; the GNSS module generating a pulse per second (PPS) signal every second; a step of setting a reference oscillation frequency in the crystal oscillator; a step in which the clock generator defines one second based on the reference oscillation frequency of the crystal oscillator; The clock generator generates a drive signal at a drive frequency based on a defined one second interval; the clock generator repeatedly generating a clock pulse signal of the reference oscillation frequency; the digital counter receiving the clock pulse signals from the clock generator and incrementing a count value by one in response to receiving each of the clock pulse signals; The digital counter receives the PPS signal from the GNSS module every second, and upon receiving the PPS signal, reads the count value, determines whether the read count value is equal to the reference vibration frequency value, and resets the count value to zero; When the digital counter determines that the count value is not equal to the reference oscillation frequency, the digital counter sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency; the slot tick module receiving the drive signal and transmitting slot tick packets at the drive frequency; The DU performs task scheduling according to the slot tick packet. A method for time synchronization between RU and DU in an ORAN system.

10. a Global Navigation Satellite System (GNSS) module that generates a pulse per second (PPS) signal every second; a quartz crystal unit for setting a reference oscillation frequency; a clock generator that defines one second based on the reference oscillation frequency of the crystal oscillator, generates a drive signal with a drive frequency based on the defined one second, and repeatedly generates a clock pulse signal with the reference oscillation frequency; a digital counter that receives the clock pulse signal from the clock generator, adds 1 to a count value in response to receiving each of the clock pulse signals, receives the PPS signal from the GNSS module every second, reads the count value upon receiving the PPS signal, determines whether the read count value is equal to the value of the reference oscillation frequency, and resets the count value to zero, and sends an oscillation frequency adjustment signal to the crystal oscillator to adjust the reference oscillation frequency if it determines that the read count value is not equal to the value of the reference oscillation frequency; a slot tick module that receives the drive signal and transmits slot tick packets of the drive frequency to a distribution unit (DU). Radio Unit (RU).

11. When the count value read by the digital counter is greater than the value of the reference vibration frequency, the digital counter sends the vibration frequency adjustment signal to the crystal oscillator to lower the reference vibration frequency by 1 Hz. The RU of claim 10.

12. When the read count value is smaller than the value of the reference vibration frequency, the digital counter sends the vibration frequency adjustment signal to the crystal oscillator to increase the reference vibration frequency by 1 Hz. The RU of claim 10.

13. the digital counter increments the count value by one upon detecting each rising edge of the clock pulse signal; The RU of claim 10.

14. The driving frequency is 2 n Hz, and n is a positive integer. The RU of claim 10.

15. further comprising a radio frequency (RF) module and a low-PHY layer; The Low-PHY layer is used to collect in-phase and quadrature data (IQ data) from the RF module; The RU of claim 10.

16. Further comprising a high-speed Ethernet interface for transmitting the IQ data from the low-PHY layer and the slot tick packets from the slot tick module to the distribution unit (DU).

16. The RU of claim 15.

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