KR20200033627A - Apparatus and Method for Compensating Delay on Front-Hall Period of Distributed Node System - Google Patents

Abstract

Disclosed are an apparatus for measuring and correcting delay in a front haul section in a distributed base station system and a method thereof. The present invention relates to a method of exchanging preset data sequences between a central processing unit and a distribution unit of a distributed base station system which calculates and corrects a delay time in a front haul. Since the present invention measures delay by exchanging data sequences, not only can the delay time be measured and corrected automatically by the method even when a wire section forming the front haul is changed, but also can the method be used more effectively even when the distribution unit or the like cannot receive an absolute time like GPS.

Description

Apparatus and Method for Compensating Delay on Front-Hall Period of Distributed Node System in a distributed base station system

The present invention relates to a compensation device for easily and easily obtaining a frame synchronization of a signal by measuring and compensating for a signal delay occurring in a front haul section in a distributed base station system.

The distributed base station system includes a central processing unit (CU) and a distributed unit (DU), and the central processing unit and the distribution unit divide and perform wireless base station functions composed of various layers.

The central processing unit, except for functions allocated exclusively to the distributed unit, is a function of the radio resource control (RRC) and packet data convergence protocol (PDCP) layer, user data transmission, mobility control, wireless access network sharing, positioning, It is a logical node that performs base station functions such as session management. The central processing unit controls the operation of the distributed unit beyond the front hole. The distributed unit is a logical node that performs a physical layer, MAC, RLC function, and performs a subset of base station functions according to a functional split option, and the operation is controlled by the central processing unit. The base station system includes an integrated base station and a separate base station in which a central processing unit and a distribution unit are included together.

Front Haul is a wired transmission network connecting a central processing unit and a distribution unit in a distributed base station, and an optical cable is usually used. The CPG (Common Public Radio Interface) protocol is used in the 4G-based distributed base station system, and the CPRI or Enhanced CPRI protocol is used in the 5G system. The front hole plays an important role in transmitting a signal, and in 5G networks, the data capacity is large and a dense base station installation is necessary, which is more important.

At the base station system level, frame boundaries of radio frames, which are standards for transmission of radio signals to a terminal, must be synchronized between units. If the front-hole section becomes longer or longer, the delay of the radio wave signal will inevitably occur, and the signal delay becomes an obstacle to matching the time synchronization in the distributed unit. In particular, since the 5G network uses a TDD (Time Division Duplex) method, time synchronization between each distributed unit is most important.

[Related Prior Art]

Republic of Korea Patent Publication No. 10-2018-0007706 (Central unit configuration method and apparatus using a front-hole interface) It is an invention of a separate base station system in a 5G system.

An object of the present invention is to provide a correction device and a correction method capable of measuring and compensating for signal delay in a front hole section in a distributed base station system.

In order to solve the above problems, a method for correcting a delay in a front hole section of a distributed base station system according to the present invention comprises: setting an individual sequence unique to a distributed unit; A delay time-measurement step in which the central processing unit sends a control sequence to the distribution unit to request the sending of the individual sequences, and calculates a delay time in the front hole from the time from sending the control sequence to receiving the individual sequences; ; A delay time-transfer step of cyclically shifting the individual sequences by the delay time and transmitting them to the dispersion unit, and the dispersion unit correlates the cyclically shifted sequences with the individual sequences to confirm the delay time; And a synchronous correction step in which the distribution unit adjusts frame boundary by the delay time to synchronize with a reference time.

Since the central processing unit measures the delay time in the front hole in synchronization with the synchronization of the frame boundary, the central processing unit transmits the data defined in the wireless communication standard by the delay time to the distribution unit, so that the distribution unit The data may be received according to a frame boundary.

According to an embodiment, the central processing unit may correct the time synchronization in units of the adjustment cycle by repeating the delay time-measuring step, the delay time-delivery step, and the synchronous correction step every predetermined adjustment cycle.

According to another embodiment, in the case of a plurality of distribution units connected to the central processing unit, the setting step may set different individual sequences for each of the plurality of distribution units.

According to another embodiment, a control unit connected to the distribution unit through the central processing unit may perform the delay time-measuring step on behalf of the central processing unit.

The present invention also extends its rights to distributed base station systems. The distributed base station system of the present invention includes a central processing unit and a distributed unit. At this time, the central processing unit includes a sequence scheduling unit and a delay compensation unit.

The sequence scheduling unit sets individual sequences unique to the distribution unit. The delay compensation unit transmits a control sequence to the distribution unit to request the transmission of the individual sequences, and calculates the delay time in the front hole from the time required for the transmission of the control sequences and reception of the individual sequences. In addition, the delay compensator cyclically shifts the individual sequences by the delay time and transmits them to the distribution unit.

The dispersion unit includes a sequence processing unit that correlates the cyclically shifted sequence with the individual sequence to check the delay time and adjusts a frame boundary by the delay time to synchronize with a reference time. do.

On the other hand, the present invention is individually entitled to each central processing unit, distribution unit, or control unit that performs the above-described correction method.

According to the present invention, it is possible to measure and correct the delay in the front hole (Frant Haul), which may inevitably occur in a distributed base station system having a central processing unit and a distribution unit. In particular, in the case of a 5G system using a time division method, the time synchronization between the central processing unit and the distribution unit, which is most important, can be matched.

In the present invention, the delay can be measured and the measured delay time can be shared by exchanging a predetermined data sequence, and the measured delay time can be synchronized with the reference time.

In addition, since the method of the present invention measures the delay by exchanging data sequences, it is possible to automatically measure and correct the delay time even when the wire section constituting the front hole is changed. It can be used more effectively when the same absolute time cannot be received.

1 is a configuration diagram of a distributed base station system of the present invention,
2 is a block diagram of a central processing unit and a distribution unit according to the present invention,
Figure 3 is a flow chart provided in the description of the delay time correction method according to an embodiment of the present invention,
4 is a timing diagram exemplarily showing a sequence transmission and reception process of the central processing unit, and
5 is a configuration diagram of a distributed base station system according to another embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

Referring to Figure 1, the base station system 100 of the present invention includes a central processing unit (CU: Central Unit) 110 and at least one distributed unit (DU: Distributed Unit) (130, 150, 170), The front hole (Front Haul) 190 connects between the central processing unit 110 and the distribution units 130, 150, and 170. The base station system 100 of FIG. 1 shows a separated type in which the central processing unit 110 and the distribution units 130, 150, and 170 are separated, but the present invention shows the central processing unit 110 and the distribution units 130, 150. , 170) also applies to an integral type implemented as a single device.

The central processing unit 110, except for functions entirely allocated to the distribution units 130, 150, and 170, transmits user data, mobility control, which is a function of a Radio Resource Control (RRC) and a Packet Data Convergence Protocol (PDCP) layer, It is a logical node that performs base station functions such as wireless access network sharing, positioning, and session management. The central processing unit 110 controls the operation of the distribution units 130, 150, 170 connected through the front hole 190.

The distributed units 130, 150, and 170 are logical nodes that perform a physical layer, MAC, RLC function, and perform a subset of base station functions according to a functional split option. ).

Referring to FIG. 2, the central processing unit 110 not only performs the functions of the conventional central processing unit 110, but also measures and compensates for signal delay in the characteristic front hole 190 of the present invention. To this end, the central processing unit 110 includes a central unit function unit 111, a reference time generation unit 113, a sequence scheduling unit 115 and a delay compensation unit 117.

The central unit function unit 111 processes a function of the central processing unit between the distribution units 130, 150, and 170 or a higher network, and corresponds to a conventional central processing unit.

The reference time generating unit 113 uses the Global Positioning System (GPS) signal, IEEE 1588 Precision Time Protocol (PTP) or internal oscillator (Oscillator) to determine the absolute time as a criterion for compensating the delay time of the present invention. Generate time. The reference time is a reference for signal delay compensation in the front hole 190 of the present invention.

The sequence scheduling unit 115 sets unique sequences for the at least one distribution unit 130, 150, 170 included in the base station system 100 and the central processing unit 110.

Here, the sequence is a sequence of data of a plurality of bytes used to measure the front-hole time delay, and is identified by a sequence number. The sequence may be of any shape, but a correlation sequence having a large correlation value is preferable because correlation is performed in the variance unit as in the correction method below.

The sequence scheduling unit 115 sets a unique sequence for each of the distribution units 130, 150, and 170, along with the sequence for the central processing unit 110 itself (hereinafter, a control sequence). Hereinafter, the sequence assigned to each distributed unit is separated from the control sequence and is referred to as an 'individual sequence'. In the example of FIG. 1, the first sequence is set in the first dispersion unit 130, the second sequence in the second dispersion unit 150, and the third sequence in the third dispersion unit 170 as individual sequences.

The delay compensator 117 measures the delay time in the front hole 190 while exchanging sequences with the dispersing units 130, 150, and 170 periodically or periodically for each adjustment period described below. Time synchronization is provided by providing the measured delay time to the dispersion units 130, 150, and 170.

The operation of the reference time generation unit 113, the sequence scheduling unit 115, and the delay compensation unit 117 will be described again with reference to FIGS. 3 and 4 below.

The distribution units 130, 150, and 170 process the functions of the distribution unit, including the distribution unit function unit and the sequence processing unit, and perform delay correction by the front hole of the present invention. 2 shows the first dispersion unit 130 on behalf of the dispersion units 130, 150, and 170. The first dispersion unit 130 includes a dispersion unit function unit 131 and a sequence processing unit 133.

The distribution unit function unit 131 processes the function of the distribution unit between the central processing unit 110 or the terminal 10 and corresponds to a conventional distribution unit. The distribution unit function unit 131 transmits and receives a radio signal between the terminal 10 including an antenna.

Upon receiving the control sequence provided by the delay compensation unit 117, the sequence processing unit 133 transmits its own sequence to the delay compensation unit 117 of the central processing unit 110, thereby allowing the Delay time measurement process is performed. In addition, the sequence processing unit 133 receives the delay time from the delay compensation unit 117 in the method of the present invention, and completes correction to match the delayed time in the front hole 190 with the reference time.

Hereinafter, with reference to FIGS. 3 and 4, the reference time generation unit 113, the sequence scheduling unit 115 and the delay compensation unit 117 of the central processing unit 110 and the distribution units 130, 150, and 170 will be described. Focusing on the operation of the sequence processing unit 133, the method for correcting the front hole delay time according to the present invention will be described.

<Assignment of sequence and transmission time: S301>

The reference time generation unit 113 provides a reference time, and the sequence scheduling unit 115 designates individual sequences to constituent units of the base station system 100. For convenience of explanation, a control sequence is assigned to the central processing unit 110, a first sequence to the first distribution unit 130, a second sequence to the second distribution unit 150, and a third distribution unit 170 ) Is assumed to have been assigned a third sequence.

<Measurement of delay time at the front hole: S303 to S307>

The delay compensation unit 117 simultaneously transmits control sequences to the first distribution unit 130, the second distribution unit 150, and the third distribution unit 170 to measure the delay of the front hole (S303). The first distribution unit 130, the second distribution unit 150, and the third distribution unit 170 transmit their individual sequences to the central processing unit 110 upon receipt of the control sequence. Therefore, after transmitting the control sequence, the delay compensation unit 117 receives a separate sequence from each distribution unit. As described above, the sequence processing unit of each distribution unit performs this process (S305).

FIG. 4 is a diagram showing control sequences sent by the central processing unit 110 and individual sequences received by the central processing unit 110 in steps S303 and S305. Referring to FIG. 4, after the delay compensation unit 117 sends the control sequence SC in step S303, the first sequence S1 is received from the first distribution unit 130 through the step S305 and the second dispersion is performed. The second sequence S2 is received from the unit 150 and the third sequence S3 is received from the third distribution unit 170.

The delay compensation unit 117 calculates a delay time that exists between each distribution unit, that is, a time synchronization shift time, by using the time taken to receive the individual sequences in step S305. Until the delay compensation unit 117 sends control sequences and receives individual sequences from the distribution unit, a round trip delay due to the round trip of the front hole 190 between the central processing unit 110 and each distribution unit is performed. Is included. Therefore, the delay compensation unit 117 may calculate the delay time by dividing the time taken to receive the sequence from the distribution unit after sending the control sequence in half (S307).

In FIG. 4, if the control sequence SC is in the process of exchanging sequences with the first distribution unit 130, if it takes (2 × τ1) to receive the first sequence S1 from the first distribution unit 130 , The delay time between the central processing unit 110 and the first distribution unit 130 is τ1. Similarly, if the control sequence (SC) is in the process of exchanging the second dispersion unit 150 and the sequence, if it took (2 × τ2) to receive the second sequence (S2) from the second dispersion unit 150, the center The delay time between the processing unit 110 and the second distribution unit 150 is τ2. Similarly, the delay time between the central processing unit 110 and the third distribution unit 170 is τ3.

<Delay time is delivered to the dispersion unit: S309 to S313>

The delay compensator 117 generates a sequence of cyclically shifting individual sequences by the delay time calculated in step S307 to transmit the delay time for each distributed unit calculated in step S307 to the corresponding distributed unit ( S309).

The delay compensator 117 transmits the sequence in which the individual sequences are cyclically shifted by a delay time to the sequence processing unit of the corresponding distribution unit. In the example of FIG. 4, since the delay time between the first distribution units 130 is τ1, the delay compensation unit 117 transmits the sequence in which the first sequence is cyclically shifted by τ1 to the first distribution unit 130. Since the delay time between the second distribution units 150 is τ2, the delay compensation unit 117 cyclically shifts the second sequence by τ2 and transmits the second sequence to the second distribution unit 150. Similarly, the delay compensation unit 117 cyclically shifts the third sequence by τ3 and transmits it to the third distribution unit 170 (S311).

The sequence processing unit of each distribution unit checks the delay time by performing a correlation of the cyclically shifted sequence received from the delay compensation unit 117 with its own individual sequence. In the example of FIG. 4, the sequence processing unit 133 of the first dispersion unit 130 correlates the sequence shifted by τ1 with the first sequence, which is its own sequence, to obtain a correlation value. The sequence processing unit 133 may check the delay time τ1 from the correlation value. The second dispersion unit 150 can also check the delay time τ2 by correlating the second sequence (S2) and the sequence that is cyclically shifted by τ2, and the third dispersion unit 170 is also cyclically shifted by τ3 and the third sequence (S3) ) To confirm the delay time τ3 (S313).

<Correction of time synchronization: 315>

Each distributed unit synchronizes the frame boundary, which is the start point of the radio frame, with the reference time by the delay time checked through step S311.

Through the above method, the distributed base station system 100 of the present invention can measure and correct the delay time in the front hole between the central processing unit and the distributed unit.

The delay compensator 117 may repeat steps S303 to S313 for each preset adjustment period to measure the time delay with the distributed unit in units of the adjustment period and match the time synchronization between units. On the other hand, the adjustment period is an interval for adjusting the time delay irrespective of other normal transmission / reception periods of 4G or 5G. In the example of FIG. 4, the adjustment period is set to 1 second.

According to another embodiment, the delay compensation unit 117 may periodically perform steps S303 to S313 when necessary.

Data transmission of central processing unit

When the delay of each front hole 190 is measured through the process of FIG. 3, when the central unit function unit 111 of the central processing unit 110 transmits data defined in the wireless communication standard to the distributed unit, each front hole By transmitting in advance as much as the delay time, each of the distribution units is allowed to receive data in a frame boundary. For example, when the central unit function unit 111 transmits data defined in the wireless communication standard to the first distribution unit 130, the front hole delay time τ1 between the first distribution units 130 is transmitted in advance. do.

Example

According to an embodiment, a separate control unit related to delay measurement and correction of the present invention may be considered. Referring to FIG. 5, a distributed base station system 500 according to another embodiment of the present invention includes a central processing unit 510 and a control unit 530. Here, the central processing unit 510 and the control unit 530 are the same as the central processing unit 110 of FIG. 2 functionally separated. In this case, the central processing unit 510 is a device including the central unit function unit 111, and the control unit 530 is a reference time generation unit 501, a sequence scheduling unit 503, and a delay compensation unit 505. It becomes a device including. The reference time generation unit 501, the sequence scheduling unit 503, and the delay compensation unit 505 of FIG. 5 are the reference time generation unit 113, the sequence scheduling unit 115, and the delay compensation unit 117 of FIG. It performs the same operation and can be described identically.

However, the control sequence provided by the delay compensation unit 530 is provided to the distribution unit via the central processing unit 510 and the front hole 190, and individual sequences provided by the distribution unit are provided by the front hole 190 and the center. The delay compensation unit 530 is received via the processing unit 510.

If the delay between the central processing unit 510 and the control unit 530 is not considered, the delay time calculated by the delay compensation unit 505 through the method of FIG. 3 will be a delay in the front hole 190. The dispersion unit checks the delay time using the cyclically shifted sequence provided by the delay compensation unit 505.

Similarly, the central processing unit 510 transmits the data defined in the wireless communication standard to the distribution unit in advance by transmitting the delay time calculated and provided by the delay compensation unit 505, so that the distribution unit receives the data synchronized to the frame boundary. can do.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and is usually not limited to the technical field to which the present invention pertains without departing from the gist of the present invention claimed in the claims. It is of course possible to perform various modifications by a person having knowledge of, and these modifications should not be individually understood from the technical idea or prospect of the present invention.

Claims (10)

In the distributed base station system in which the central processing unit and the distribution unit are connected, in the method of correcting the delay of the front hole section,
Setting an individual sequence unique to the distribution unit;
Delay-measurement step in which the central processing unit transmits a control sequence to the distribution unit to request the transmission of the individual sequences, and calculates the delay time in the front hole from the time required until the reception of the individual sequences after the control sequence is sent ;
A delay time-transfer step of cyclically shifting the individual sequences by the delay time and transmitting them to the dispersion unit, and the dispersion unit correlates the cyclically shifted sequences with the individual sequences to confirm the delay time; And
The dispersion unit comprises a synchronization correction step of adjusting the frame boundary (Frame Boundry) by the delay time to synchronize with the reference time Delay correction method of the front hole section in a distributed base station system.
According to claim 1,
The central processing unit repeats the delay time-measurement step, delay time-delivery step and synchronous correction step every predetermined adjustment period to correct the time synchronization in units of the adjustment period, and thus the front hole in the distributed base station system Section delay correction method.
According to claim 1,
The setting step,
When there are a plurality of distributed units connected to the central processing unit, a method for correcting delay of a front hole section in a distributed base station system, characterized in that different individual sequences are set for each of the plurality of distributed units.
According to claim 1,
Delay correction method of a front-hole section in a distributed base station system, characterized in that the control unit connected to the distribution unit through the central processing unit performs the delay time-measuring step on behalf of the central processing unit.
The method according to any one of claims 1 to 4,
In the distributed base station system, characterized in that the distributed unit receives the data in a frame boundary by transmitting the data defined in the wireless communication standard by the delay time to the distributed unit. Delay correction method of front hole section.
In the distributed base station system in which the central processing unit and the distribution unit are connected,
The central processing unit,
A sequence scheduling unit that sets individual sequences unique to the distribution unit; And
And a delay compensator for requesting the transmission of the individual sequences by sending a control sequence to the distribution unit, and calculating the delay time at the front hole from the time required until the reception of the individual sequences after the control sequence is sent.
The delay compensator cyclically shifts the individual sequences by the delay time and transmits them to the distribution unit,
The dispersion unit,
And correlating the cyclically shifted sequence with the individual sequence to check the delay time and adjusting a frame boundary by the delay time to include a sequence processing unit that synchronizes with a reference time. Distributed base station system.
The method of claim 6,
The delay compensation unit repeats the process of measuring the delay time by transmitting the control sequence for each predetermined adjustment period, the distributed base station system, characterized in that for correcting the time synchronization in units of the adjustment period.
The method of claim 6,
The sequence scheduling unit,
A distributed base station system characterized in that different individual sequences are set for each of the plurality of distributed units when the plurality of distributed units are multiple.
The method of claim 6,
The sequence scheduling unit and the delay compensation unit,
Distributed base station system, characterized in that disposed in a control unit connected to the distribution unit through the central processing unit.
The method according to any one of claims 6 to 9,
A distributed base station system, characterized in that the distributed unit receives the data in a frame boundary by transmitting the data defined in the wireless communication standard by the delay time to the distributed unit.

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