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KR20130038140A - Apparatus and method for time synchronization - Google Patents

Apparatus and method for time synchronization Download PDF

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Publication number
KR20130038140A
KR20130038140A KR1020120106637A KR20120106637A KR20130038140A KR 20130038140 A KR20130038140 A KR 20130038140A KR 1020120106637 A KR1020120106637 A KR 1020120106637A KR 20120106637 A KR20120106637 A KR 20120106637A KR 20130038140 A KR20130038140 A KR 20130038140A
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South Korea
Prior art keywords
base station
synchronization
time information
macrocell
time synchronization
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KR1020120106637A
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Korean (ko)
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유봉국
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한국전자통신연구원
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Priority to US13/646,119 priority Critical patent/US8879536B2/en
Publication of KR20130038140A publication Critical patent/KR20130038140A/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/001—Synchronization between nodes
    • H04W56/0015—Synchronization between nodes one node acting as a reference for the others

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

Abstract

The time synchronization device of a femtocell base station receives a timing packet generated by a timing server directly connected to an adjacent macrocell base station adjacent to one femtocell base station through the adjacent macrocell base station, and cannot synchronize time from a GPS satellite. In this case, time synchronization is performed by obtaining system time information from a timing packet received through a macrocell base station corresponding to a master base station among neighboring macrocell base stations.

Description

Vision synchronizer and method {APPARATUS AND METHOD FOR TIME SYNCHRONIZATION}

The present invention relates to a time synchronization device and method, and more particularly, to a time synchronization device and method of a femtocell base station.

The type of mobile communication service is rapidly changing from voice to data, and the increase in data call volume is expected to increase rapidly due to the spread of smart phones. As a result, a femtocell base station having a concept of installing a small base station in a house to increase service capacity has emerged as a method for efficiently using a limited frequency resource.

However, since femtocell base stations are generally installed in buildings, the reception performance of time information signals from existing GPS satellites is significantly reduced, causing synchronization problems with existing base stations (eg, macro cell base stations). It became.

In order to solve this synchronization problem, various synchronization acquisition schemes have been devised, and the secondary GPS (Assisted GPS) method, which receives information about GPS satellites such as Almanac data or ephemeris data through a wired network from a separate auxiliary server, There is a wireless access technology based method for receiving and using a synchronization radio signal, and a network based method using a network synchronization protocol such as PTP (Precision Time Protocol).

Among the various types of synchronization schemes, the secondary GPS scheme or the radio access technology based scheme is relatively high in terms of the femtocell base station. Therefore, a network based scheme that can be implemented at a relatively low cost is preferred.

 Existing network-based method is the IEEE 1588 standard of Precision Time Protocol (PTP), NTP (Federated) which is developed by the femtocell base station to synchronize asynchronous networks such as Ethernet in order to maintain time synchronization with the existing macrocell base station. Network Timing Protocol) is achieved by receiving time information provided by the protocol.

In this network-based method, a timing server connected to a wired internet network transmits a timing packet through a wired internet network, and a femtocell base station, a client, extracts a synchronization signal included in the received timing packet. .

However, the accuracy of synchronization in such a network-based scheme is largely determined by the imbalance of uplink and downlink packet delays of non-dedicated line services such as x-DSL and FTTH. That is, the delay of packet delivery is irregularly increased due to the increase of traffic volume on the asynchronous network through which timing packets are delivered. As the number of femtocells increases and the size of the network increases, the synchronization error increases proportionally.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a time synchronization device and a method for quickly synchronizing time with a macro cell base station without a delay caused by a traffic volume of a network in a femtocell base station.

According to an embodiment of the present invention, in a wireless communication system including a plurality of macrocell base stations and at least one femtocell base station located in a cell region of each macrocell base station, a time synchronization device of any one femtocell base station is provided. . The time synchronization device includes a neighbor list generator, a receiver, and a synchronizer. The neighbor list generating unit generates a neighbor macrocell base station list including information of a neighboring macrocell base station adjacent to any one femtocell base station. The receiver receives a timing packet generated by a timing server directly connected to the neighboring macrocell base station through the neighboring macrocell base station. When the time synchronization from the GPS satellites is impossible, the synchronization unit obtains system time information from the timing packet received through the macro cell base station corresponding to the master base station among the neighboring macro cell base stations to perform time synchronization.

The time synchronization device may further include a master base station setting unit. The master base station setting unit sets one of the neighboring macrocell base stations as the master base station, and sets the other of the neighboring macrocell base stations as candidate master base stations.

The synchronization unit may perform time synchronization by acquiring system time information from a timing packet received through a macro cell base station corresponding to the candidate master base station when a network synchronization failure occurs after the time synchronization.

The time synchronization device may further include a receiver configured to receive a time information signal from the GPS satellite, and the synchronizer may determine whether time synchronization from the GPS satellite is impossible based on the reception quality of the time information signal. .

When it is determined that time synchronization from the GPS satellite is possible, the synchronization unit may perform time synchronization by acquiring the system time information from the time information signal.

According to another embodiment of the present invention, in a wireless communication system including a plurality of macrocell base station and at least one femtocell base station located in the cell region of each macrocell base station, there is provided a time synchronization method of any one femtocell base station do. The time synchronization method determines whether time synchronization from a GPS satellite is impossible, and receives, through the neighboring macrocell base station, a timing packet generated by a timing server directly connected to an adjacent macrocell base station adjacent to any one femtocell base station. And if time synchronization from the GPS satellites is impossible, acquiring system time information from a timing packet received through a macrocell base station corresponding to a master base station among the neighboring macrocell base stations to perform time synchronization. Include. In this case, the timing packet may include system time information obtained from a GPS satellite by a macrocell base station corresponding to the master base station.

The time synchronization method may further include setting one of the neighboring macrocell base stations as the master base station and setting another one of the neighboring macrocell base stations as a candidate master base station.

The time synchronization method further includes the step of performing time synchronization by acquiring system time information from a timing packet received through a macro cell base station corresponding to the candidate master base station when a network synchronization failure occurs after performing the time synchronization. can do.

According to another embodiment of the present invention, in a wireless communication system including a plurality of macrocell base station and at least one femtocell base station located in the cell region of each macrocell base station, the time synchronization method of any one macrocell base station This is provided. The time synchronization method may include receiving a time information signal including system time information from a GPS satellite, performing time synchronization using the system time information, and transmitting the system time information to the one macrocell base station. Transmitting to a timing server that is directly connected, receiving a timing packet including the system time information from the timing server, and transmitting the timing packet to an adjacent femtocell base station.

The time synchronization method may further include generating a neighbor femtocell base station list including information of the adjacent femtocell. In this case, the neighbor femtocell base station list may include a femtocell base station in a cell region of the one macrocell base station and a femtocell base station in an adjacent macrocell region of a cell region of the one macrocell base station.

According to an embodiment of the present invention, the femtocell base station can obtain the time synchronization information of the macro cell base station quickly without delay according to the traffic volume of the network, and the GPS time of the adjacent macro cell base station to maintain the time synchronization with the macro cell base station. Since the synchronization information is used, the synchronization recovery time is fast.

In addition, it can be easily applied to the traffic capacity-distributed small base stations and repeaters, which are not femtocell base stations.

1 is a diagram illustrating an example of a wireless communication system according to an embodiment of the present invention.
2 is a diagram illustrating a time synchronization device of a femtocell base station according to an embodiment of the present invention.
3 is a flowchart illustrating a time synchronization method of a femtocell base station according to an embodiment of the present invention.
4 is a diagram illustrating a time synchronization device of a macro cell base station according to an embodiment of the present invention.
5 is a diagram illustrating a time synchronization method of a macro cell base station according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

The apparatus and method for synchronizing time according to an embodiment of the present invention will now be described in detail with reference to the drawings.

1 is a diagram illustrating an example of a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 1, a wireless communication system according to an exemplary embodiment of the present invention includes at least one femtocell 11, 12/21 in one macrocell 1/2.

The macrocells 1, 2 have a wide cell radius, for example, a radius of about 1 km, and the femtocells 11, 12, 21 have a radius smaller than the radius of the macrocells 1, 2. For example, the femtocells 11, 12, and 21 may include a micro cell having a radius of 50 to 100 m or a Wi-Fi hotspot.

The macrocells 1 and 2 include macrocell base stations 10 and 20 that manage the macrocells 1 and 2. The femtocells 11, 12, 21 also include femtocell base stations 110, 120, 210 that manage the femtocells 11, 12, 21.

Femtocell base stations (110, 120, 210) are generally installed in a shadow area or a user dense area in the building, it may be connected to the macro cell base station (10, 20) through a wired network (50).

These macrocell base stations 10, 20 and femtocell base stations 110, 120, 210 receive time information signals including system time information from the GPS satellites 60 and between the macrocell base stations 10, 20 and femtocells. Time synchronization is performed between the base stations 110, 120, and 210 and between the macro cell base stations 10 and 20 and the femtocell base stations 110, 120, and 210.

However, the femtocell base stations 110, 120, 210 have significantly lower reception performance of the time information signal from the GPS satellite 60 on the installation location than the macrocell base stations 10, 20. As a result, time synchronization between the macro cell base stations 10 and 20 and the femtocell base stations 110, 120, and 210 may not be properly performed.

For time synchronization between the macrocell base stations 10 and 20 and the femtocell base stations 110, 120 and 210, the macrocell base stations 10 and 20 receive system time information by receiving time information signals from the GPS satellites 60. The acquired system time information is transmitted to the timing servers 30 and 40 respectively connected to the macro cell base stations 10 and 20.

The timing server 30, 40 generates a timing packet including system time information received from the macrocell base station 10, 20, respectively, and the timing packet corresponds to the neighbor femtocell base station list of the macrocell base station 10, 20. Transmit to femtocell base station. The timing packet may be transmitted to the corresponding femtocell base station through the macrocell base stations 10 and 20 and the wired network 50.

When the femtocell base stations 110, 120, 210 are unable to synchronize time using the time information signal from the GPS satellite 60, the femtocell base stations 110, 120, 210 may be at least one of the macrocell base stations 10, 20. The system time information is obtained from the timing packet received through the A / S, and time synchronization is performed.

In particular, the femtocell base station (110, 120, 210) is obtained from the timing packet received through the master base station by setting one of the macro cell base station (10, 20) as a master base station, and the other as a candidate master base station If a network synchronization failure occurs in the system time information, time synchronization may be performed again using the system time information obtained from the timing packet received through the candidate mast base station.

That is, by providing a plurality of timing servers 30 and 40 for time synchronization of the femtocell base station, the time synchronization error can be reduced when the number of femtocells increases and the network size increases.

2 is a diagram illustrating a time synchronization device of a femtocell base station according to an embodiment of the present invention, and FIG. 3 is a flowchart illustrating a time synchronization method of a femtocell base station according to an embodiment of the present invention.

In FIG. 2, for convenience of description, the time synchronization device 200 of the femtocell base station 110 among the femtocell base stations 110, 120, and 210 shown in FIG. 1 will be described, and the time of the remaining femtocell base stations 120 and 210 will be described. The synchronization device may also be configured with the time synchronization device of the femtocell base station 110.

Referring to FIG. 2, the time synchronization device 200 includes a receiver 210, a neighbor list generator 220, a master base station setup unit 230, and a synchronizer 240.

Referring to FIG. 3, the receiver 210 receives a time information signal from the GPS satellite 60 (S302). In addition, the receiver 210 receives a timing packet from at least one macrocell base station 10, 20 corresponding to the neighboring macrocell base station list (S304).

The neighbor list generation unit 220 generates a neighbor macro cell base station list (S306). For example, the neighboring macrocell base station list may include macrocell base stations 10 and 20 that exceed a threshold for receiving Received Signal Strength Indication (RSSI).

The master base station setting unit 230 sets one of the neighboring macrocell base stations 10 and 20 corresponding to the neighboring macrocell base station list as the master base station and the other as the candidate master base station (S308). The master base station setting unit 230 sets a macro cell base station (eg, 10) having the largest RSSI among the neighboring macro cell base stations 10 and 20 corresponding to the neighboring macro cell base station list as the master base station, and the RSSI is set to the master base station. Next, a large macro cell base station (for example, 20) can be set as a candidate master base station.

The synchronizer 240 performs time synchronization with the macro cell base stations 10 and 20.

The synchronizer 240 measures the reception quality of the time information signal from the GPS satellite 60, and determines whether the reception quality of the time information signal is good (S310).

If it is determined that the reception quality of the time information signal is good (S310), the synchronization unit 240 performs time synchronization in the GPS mode. In this case, a predetermined threshold value may be set to determine whether the reception quality is good, and the threshold value may be set differently according to a method for measuring reception quality. This threshold may be set by an administrator of the wireless communication system and may be changed. For example, the RSSI of the time information signal may be used as a method for measuring the reception quality, and the synchronization unit 240 determines that the reception quality of the time information signal is good when the RSSI of the time information signal is greater than or equal to a set threshold. If not, it may be determined that the reception quality is not good.

The GPS mode means that time synchronization is performed using the time information signal of the GPS satellite 30, and the synchronization unit 240 acquires system time information from the time information signal in the GPS mode (S312), and the system time. Time synchronization is performed using the information (S314).

On the other hand, if it is determined that the reception quality of the time information signal is not good (S310), the synchronization unit 240 performs a time synchronization in the network-based mode by switching the synchronization mode from the GPS mode to the network-based mode.

The network-based mode means that time synchronization is performed using a timing packet received through the wired network 50. The synchronization unit 240 obtains system time information from the timing packet received from the master base station (S316). Time synchronization is performed using the acquired system time information (S318).

If a network synchronization failure occurs due to a failure of the master base station after performing time synchronization (S320), the synchronization unit 240 obtains system time information from the timing packet received from the candidate master base station (S322). Time synchronization is performed using the system time information (S324).

In this manner, time synchronization of the femtocell base station 110 may be performed.

As such, the timing packet is transmitted only to the femtocell base station in some macrocells, not the entire network, by the timing servers 30 and 40 connected to the macrocell base stations 10 and 20, respectively. It is possible to maintain the time synchronization of the entire system while minimizing the inconsistency of the system time information which increases proportionally with the amount.

4 is a diagram illustrating a time synchronization device of a macro cell base station according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating a time synchronization method of a macro cell base station according to an embodiment of the present invention.

In FIG. 4, the macro cell base station 10 of one of the macro cell base stations 10 and 20 illustrated in FIG. 1 is described. The macro cell base station 20 may also operate in the same manner as the macro cell base station 10. .

Referring to FIG. 4, the time synchronization device 400 of the macro cell base station 10 includes a receiver 410, a synchronizer 420, a neighbor list generator 430, and a transmitter 440.

5, the receiver 410 receives a time information signal from the GPS satellite 60 (S502).

The synchronizer 420 acquires system time information using the time information signal received from the GPS satellite 60 (S504), and performs time synchronization using the acquired system time information (S506).

The neighbor list generator 430 generates a neighbor femtocell base station list (S508). For example, the femtocell base station 210 of the neighboring macrocell 2 of the macrocell 1 as well as the femtocell base stations 110 and 120 of the macrocell 1 managed by the macrocell base station 10 are included in the neighboring femtocell base station list. ) May be included.

The transmitter 440 transmits the acquired system time information and the neighbor femtocell base station list to the timing server 30 (S510).

When the timing server 30 receives the system time information and the neighbor femtocell base station list from the time synchronization device 400 of the macrocell base station 10 (S512), it generates a timing packet including the received system time information (S512). In operation S514, the generated timing packet is transmitted to the femtocell base stations 110, 120, and 210 corresponding to the adjacent femtocell base station list through the time synchronization device 400 of the macrocell base station 10 (S516 to S518). In this case, the timing packet may be received through the receiver 410 and transmitted to the femtocell base stations 110, 120, and 210 corresponding to the neighbor femtocell base station list through the transmitter 440.

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such an implementation can be easily implemented by those skilled in the art to which the present invention pertains based on the description of the above-described embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (13)

In the wireless communication system comprising a plurality of macrocell base station and at least one femtocell base station located in the cell region of each macrocell base station, as a time synchronization device of any one femtocell base station,
A neighbor list generator for generating a neighbor macrocell base station list including information of neighbor macrocell base stations adjacent to any one femtocell base station;
A receiver for receiving a timing packet generated by a timing server directly connected to the neighboring macrocell base station through the neighboring macrocell base station; and
When the time synchronization from the GPS satellites is impossible, the synchronization unit for acquiring the system time information from the timing packet received through the macro cell base station corresponding to the master base station of the adjacent macro cell base station to perform time synchronization
Vision synchronizing device comprising a. In claim 1,
A master base station setting unit for setting one of the neighboring macrocell base stations as the master base station and setting the other one of the neighboring macrocell base stations as a candidate master base station;
A visual synchronization device further comprising. In claim 2,
And the synchronization unit obtains system time information from a timing packet received through a macrocell base station corresponding to the candidate master base station and performs time synchronization when a network synchronization failure occurs after the time synchronization. In claim 1,
Receiving unit for receiving the time information signal from the GPS satellites
Further comprising:
And the synchronization unit determines whether time synchronization from the GPS satellites is impossible based on the reception quality of the time information signal. 5. The method of claim 4,
And, when it is determined that time synchronization from the GPS satellite is possible, the synchronization unit obtains the system time information from the time information signal and performs time synchronization. In claim 1,
And the system time information is included in a time information signal received from a GPS satellite by a macrocell base station corresponding to the master base station. In a wireless communication system comprising a plurality of macrocell base station and at least one femtocell base station located in the cell region of each macrocell base station, as a time synchronization method of any one femtocell base station,
Determining whether time synchronization from the GPS satellites is impossible;
Receiving, through the neighboring macrocell base station, a timing packet generated by a timing server directly connected to an adjacent macrocell base station adjacent to any one femtocell base station; and
Performing time synchronization by acquiring system time information from a timing packet received through a macro cell base station corresponding to a master base station among the neighboring macro cell base stations when time synchronization from the GPS satellites is impossible;
Including;
And the timing packet includes system time information obtained from a GPS satellite by a macrocell base station corresponding to the master base station. In claim 7,
And setting one of the neighboring macrocell base stations as the master base station, and setting the other one of the neighboring macrocell base stations as a candidate master base station. 9. The method of claim 8,
Performing network synchronization by acquiring system time information from a timing packet received through a macrocell base station corresponding to the candidate master base station when a network synchronization failure occurs after performing the time synchronization.
The visual synchronization method further comprising. In claim 7,
The determining step
Receiving a time information signal from the GPS satellites, and
And determining whether time synchronization from the GPS satellites is impossible based on the reception quality of the time information signal. 11. The method of claim 10,
If time synchronization from the GPS satellites is possible, performing time synchronization using system time information included in the time information signal received from the GPS satellites;
The visual synchronization method further comprising. In a wireless communication system including a plurality of macrocell base station and at least one femtocell base station located in the cell region of each macrocell base station, as a time synchronization method of any one macrocell base station,
Receiving a time information signal containing system time information from a GPS satellite,
Performing time synchronization using the system time information;
Transmitting the system time information to a timing server directly connected to any one macrocell base station;
Receiving a timing packet including the system time information from the timing server, and
Transmitting the timing packet to an adjacent femtocell base station
Visual synchronization method comprising a. The method of claim 12,
Generating a neighbor femtocell base station list including information of the neighbor femtocell;
Further comprising:
The neighbor femtocell base station list includes a femtocell base station in a cell region of any one of the macrocell base station and a femtocell base station in an adjacent macrocell region of the cell region of the one macrocell base station.
KR1020120106637A 2011-10-07 2012-09-25 Apparatus and method for time synchronization KR20130038140A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20180024683A (en) * 2016-08-31 2018-03-08 주식회사 큐셀네트웍스 Method and Apparatus for Small Cell Synchronization
KR20180033496A (en) * 2018-03-28 2018-04-03 주식회사 큐셀네트웍스 Method and Apparatus for Clock Synchronization in a Small Cell
KR20190015004A (en) * 2017-08-04 2019-02-13 주식회사 큐셀네트웍스 Method and Apparatus for Synchronization Acquisition Between Small Cells
KR20190015088A (en) * 2018-06-12 2019-02-13 주식회사 큐셀네트웍스 Method and Apparatus for Synchronization Acquisition Between Small Cells
KR20190023465A (en) 2017-08-29 2019-03-08 한국항공우주연구원 Test System and Method for Synchronizing Time thereof
KR20200042741A (en) 2018-10-16 2020-04-24 한국항공우주연구원 Test system and Method for correction after time synchronization

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20180024683A (en) * 2016-08-31 2018-03-08 주식회사 큐셀네트웍스 Method and Apparatus for Small Cell Synchronization
KR20190015004A (en) * 2017-08-04 2019-02-13 주식회사 큐셀네트웍스 Method and Apparatus for Synchronization Acquisition Between Small Cells
KR20190023465A (en) 2017-08-29 2019-03-08 한국항공우주연구원 Test System and Method for Synchronizing Time thereof
KR20180033496A (en) * 2018-03-28 2018-04-03 주식회사 큐셀네트웍스 Method and Apparatus for Clock Synchronization in a Small Cell
KR20190015088A (en) * 2018-06-12 2019-02-13 주식회사 큐셀네트웍스 Method and Apparatus for Synchronization Acquisition Between Small Cells
KR20200042741A (en) 2018-10-16 2020-04-24 한국항공우주연구원 Test system and Method for correction after time synchronization

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