KR20110034315A - Method for micro base station synchronization and system therof - Google Patents

Abstract

PURPOSE: A method for synchronizing a micro base station and a system thereof are provided to obtain accurate time synchronization through the construction of a wireless link for transmitting synchronization even though an uplink and downlink of a backhaul are asymmetry to each other. CONSTITUTION: A base station(110) is synchronized with a core network(100), and a wireless AP(Access Point)(130) is connected to the base station. The wireless AP transfers a beacon through the synchronization with the core network, and a wireless access terminal(140) restores clock information from the beacon after receiving the beacon. The wireless access terminal creates synchronization information which performs the synchronization with the core network. A micro BS(Base Station)(150) is connected to the wireless access terminal, and performs the synchronization with the core network through the synchronization information.

Description

Synchronization method of small base station and system using same {METHOD FOR MICRO BASE STATION SYNCHRONIZATION AND SYSTEM THEROF}

The present invention relates to a small base station synchronization system and a method for synchronizing a small base station, and to a method for providing synchronization between a macro base station and a small base station for mobile communication using a beacon transmission of a wireless access point (AP).

Recently, small base stations, such as femtocells or picocells, have received a lot of attention in terms of coverage of mobile communication networks, service quality improvement, and integration of wired and wireless communication services. The small base station is largely classified into a fixed mobile convergence (FMC) using a dual mode terminal and a fixed mobile substitution (FMS) method using an existing mobile communication terminal as it is, and in the present invention, a femtocell is generally used. Or consider an FMS method called a picocell (picocell).

In general, a femtocell refers to a small base station that is very small compared to a macro base station in the size of a digital subscriber line router or a cable modem. The femtocell can operate in the authorized frequency band or unapproved frequency band (ISM band, etc.) assigned to the mobile operator, the output voltage covers 10 ~ 200mW, the communication distance is about 50-100m, and within 10 users You can connect at the same time. It can be installed by the network operator or the user, and is connected to the core network by using a separate communication network or by using a high speed internet network.

In the case of picocell, it is a middle concept between femtocell and macro base station, which is somewhat larger than femtocell and can be accessed by less than 30 users at the same time.

In the case of the repeater, since the signal received from the macro base station is transmitted as it is, base station coverage is expanded but capacity does not increase. Small base stations, on the other hand, perform the same functions as existing macro base stations, increasing coverage and increasing wireless network capacity. In particular, in the case of a mobile communication system that has been commercialized or standardized recently, the coverage of the macro base station is narrower than that of the existing mobile communication system because the carrier frequency used is high and the bandwidth is wide. In other words, when the network is built with only macro base stations, the number of required base stations increases and the network construction cost increases. As an alternative, it is being studied as a viable alternative to provide a wireless communication service by installing a low-cost small base station in an office or home where people mainly use wireless communication.

Meanwhile, in order to simultaneously operate an existing macro base station and a small base station in a mobile communication network, the carrier frequency and signal transmission time of the small base station must be synchronized with the macro base station. In particular, in case of using time division duplex method such as Mobile WiMax, the uplink / downlink signal of the macro base station and the small base station if the signal transmission time of the macro base station and the small base station are out of order. Since interference occurs between downlink and uplink signals, it is very important to synchronize the time between the macro base station and the small base station.

In the case of the existing macro base station, since the transmitting and receiving antenna is installed outdoors, it receives global positioning system (GPS) information from the satellite and synchronizes the core network with the macro base station. However, in the case of a small base station, the GPS signal cannot be used for synchronizing because it is installed in a room, such as an office, a school, an apartment, a house, etc., which is generally difficult to receive the GPS signal. In addition, even if the GPS signal can be received, there is a disadvantage that the price of the small base station is expensive because a separate device for receiving the GPS signal must be attached to the small base station.

Accordingly, when a small base station cannot receive a GPS signal, a method of acquiring synchronization using a pilot signal transmitted from a macro base station has been proposed. However, this method has a disadvantage that it can be applied only when the downlink pilot signal of the macro base station can be received in the region where the small base station is installed. The small base station is installed in an area where the macro base station signal is not transmitted, and its main purpose is to expand the wireless communication service area and expand its capacity. However, if the small base station is to be installed in the coverage of the macro base station, the utility of the small base station is significantly reduced.

Recently, when a small base station and a core network are connected by wire using a high speed internet, a method of acquiring synchronization of a small base station using the IEEE1588 standard has been studied.

1 is a diagram illustrating a system for synchronization between a core network and a small base station using a conventional IEEE1588. In the case of using IEEE1588, the core network and the small base station are wired by an internet protocol (IP) network as shown in FIG.

In the core network, synchronization is acquired using GPS and the like, and this information is transmitted to the small base station by wire. The IEEE 1588 master is used for the core network to transmit the synchronization information, and the IEEE 1588 slave is used in the small base station. In IEEE1588, a data packet recording the synchronization information of the core network is periodically transmitted to the IEEE1588 slave. The IEEE 1588 slave estimates time synchronization in consideration of the synchronization information recorded in the received packet and the transmission delay, and uses this value to correct the time synchronization of the small base station so that the synchronization between the core network and the small base station is matched. On the other hand, since the macro base station is synchronized with the core network using GPS signals, the macro base station and the small base station are also synchronized with each other.

When the core network and the small base station are wired in this way, the synchronization of the small base station can be obtained using the IEEE1588 as described above. However, IEEE1588 is applicable only when the transmission delay of the uplink transmitting data from the small base station to the core network is the same as the downlink transmitting data from the core network to the small base station. That is, when the uplink and downlink transmission speeds are the same as in Ethernet, accurate synchronization can be obtained using IEEE1588. However, when using a digital subscriber line network such as high-speed Internet, there is a significant difference in the transmission speed of downlink and uplink, and when the IEEE1588 standard is applied as it is, a synchronization estimation error occurs due to a difference in transmission delay.

According to the actual data conducted by KT, the synchronization estimation error due to the asymmetry of uplink and downlink is measured from several hundred microseconds to several milliseconds. However, the mobile WiMAX standard stipulates that the time synchronization error of all base stations, including small base stations, is less than 20 microseconds. Since most offices and homes in Korea use high-speed Internet to access the Internet, it is natural to connect small base stations to high-speed Internet. However, when using a conventional IEEE1588 transmission method, there is a problem that it is difficult to obtain accurate time synchronization information when a small base station is connected to a high-speed Internet network.

Meanwhile, to use a small base station in an office or home, a network connecting the core network and the small base station is required. One method is to connect by wire using high speed internet as in the prior art. However, as described above, there is a problem that it is difficult to obtain synchronization information, and when a small base station is installed in a large building, the wired network is not built or the capacity of the existing wired network is saturated, so that a separate wired network for the small base station needs to be separately constructed. Occurs. In this case, a considerable amount of money is required for the construction of the wired network, and the landlord is often reluctant to perform the wired construction for reasons of building management and aesthetics.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a synchronization method between a core network or a macro base station and a small base station.

In addition, unlike the conventional method, there is no restriction on the installation position, and also provides a method for obtaining accurate time synchronization even when the uplink and the downlink are asymmetric.

Small base station synchronization system according to the present invention for achieving the above object is a base station synchronized with the core network; A wireless access point (ACCESS POINT) connected to the base station and transmitting beacons in synchronization with the core network; A radio access terminal (ACCESS TERMINAL) for generating synchronization information for performing synchronization with the core network by restoring clock information from the beacon after receiving the beacon; And a small base station connected to the wireless access terminal and performing synchronization with the core network using the synchronization information.

The wireless access point is a GPS module for receiving a GPS signal for synchronization with the core network; And a transmission module synchronized with the GPS signal to periodically transmit a beacon.

In addition, the transmission module is preferably synchronized with the GPS signal to drive the built-in timer, and linked to the timer to periodically generate and transmit the beacon.

The wireless access point further includes a multiplexer (MUX) module for combining the beacon and the data packet, and the transmission module preferably transmits the combined packet.

Meanwhile, after receiving a beacon from the outside, the wireless access terminal device according to an embodiment of the present invention restores time information of the core network using the beacon, and synchronizes with the core network using the restored time information. It is characterized in that for transmitting the synchronization information to the small base station.

After receiving the beacon, the wireless access terminal device restores time information of the core network using the received beacon, and generates synchronization information for synchronizing with the core network using the restored time information. Information restoration module; And a synchronization information transmission module for transmitting the generated synchronization information to the small base station.

The time information restoration module may further include a time error calculation module for calculating a time error from a difference between an expected reception time and an actual reception time of the beacon; A time error correction module for correcting the time error by calculating a transmission delay time of a beacon; A time error average module for estimating an average of the corrected time error; And a beacon time synchronization module for feeding back the estimated average time error to a local clock generator, such that the local clock is synchronized to the reception time of the beacon.

When the beacon is received, the time error calculating module measures a beacon actual reception time of measuring the time when the beacon is received using a local clock, and estimates the beacon expected reception time using the period information of the beacon. It is preferable to measure and calculate a time error using the difference between the actual beacon reception time and the expected beacon reception time.

The wireless access terminal device may further include a demultiplexer (DEMUX) module configured to receive a packet from the outside and classify the received packet into a beacon and a data packet; And a data decoder module for processing the received data packet and transmitting the processed data packet to a small base station.

Meanwhile, after receiving a beacon from the outside, the small base station for synchronization according to an embodiment of the present invention restores time information of the core network using the beacon, and synchronizes with the core network using the restored time information. Characterized in that.

The small base station includes: a radio access terminal module (ACCESS TERMINAL) including a time information restoration module for restoring time information of a core network using the received beacon after receiving the beacon; And a control module for performing synchronization with the core network using the restored time information.

On the other hand, the synchronization performing method in a small base station according to an embodiment of the present invention is a beacon transmission step of transmitting a beacon in synchronization with the core network; After receiving the beacon, recovering clock information from the beacon, and performing a synchronization with the core network.

And receiving a GPS signal for synchronizing with the core network, wherein the beacon transmission step is preferably synchronized with the received GPS signal to periodically transmit a beacon.

In the beacon transmission step, it is preferable to drive a built-in timer in synchronization with the received GPS signal, and periodically generate and transmit the beacon in association with the timer.

And a multiplexer step of combining the beacon and the data packet, wherein the beacon transmission step preferably transmits the combined packet.

The synchronizing step may include: a time information restoration step of restoring time information of a core network using the received beacon after receiving the beacon; And a synchronization control step of performing synchronization with the core network using the restored time information.

The time information restoration step may include a time error calculation step of calculating a time error from a difference between an expected reception time and an actual reception time of the beacon; A time error correction step of correcting the time error by calculating a transmission delay time of a beacon; A time error average step of estimating an average of the corrected time error; And a beacon time synchronization step of feeding back the estimated average time error to a local clock generator so that the local clock is synchronized to the reception time of the beacon.

In addition, when the beacon is received, the time error calculation step measures a beacon actual reception time of measuring a time when the beacon is received using a local clock, and estimates the beacon expected reception time using the period information of the beacon. It is preferable to measure and calculate a time error using the difference between the actual beacon reception time and the expected beacon reception time.

And a demultiplexer (DEMUX) for receiving the combined packet and classifying the received packet into a beacon and a data packet. And a data decoder step of processing the received data packet.

As described in detail above, by using the small base station synchronization system and the synchronization method according to the present invention, it can be used indoors and is not limited by the installation position of the small base station.

In addition, even if the uplink and the downlink of the backhaul are asymmetric, accurate time synchronization can be obtained by establishing a radio link for synchronous transmission. In addition, when using a wireless LAN-based wireless backhaul for installation convenience of the small base station, it is possible to obtain the time synchronization of the small base station using the beacons of the wireless LAN without using a separate packet for transmission of synchronization information.

Therefore, by using the synchronization scheme proposed in the present invention, it is possible to significantly reduce the installation position constraint of the small base station and at the same time obtain more accurate time synchronization than the conventional scheme.

As described above, in order to operate a small base station such as a femtocell base station or a picocell base station in a mobile communication network, the time clock of the small base station must be synchronized with the time clock of the macro base station. In particular, in a wireless communication system using time division multiplexing such as mobile WiMAX, when the time synchronization between the macro base station and the small base station is out of time, the uplink signal of the macro base station interferes with the downlink signal of the small base station, or the downlink of the macro base station. The signal interferes with the uplink signal of the small base station. In addition, the uplink and downlink signals of the small base station interfere with the downlink and uplink signals of the macro base station. Since such interference can significantly reduce the capacity of the mobile communication base station, time synchronization between the macro base station and the small base station is very important.

In the case of a GPS-based method, which is widely used as a synchronization acquisition method between a core network and a macro base station, it is difficult to apply to a small base station. Unlike macro base stations, small base stations are often installed indoors and are often installed outside the coverage of macro base stations. Accordingly, in the case of the conventional acquisition method using GPS, it is difficult to use the indoors where GPS signal reception is difficult, and the synchronization acquisition method using the pilot of the macro base station cannot be used when the installation location of the small base station is out of coverage of the macro base station.

In addition, in the case of the synchronization method using IEEE1588, it is difficult to accurately measure the time error when the uplink and the downlink of the backhaul are asymmetrical, such as a high-speed Internet network.

Accordingly, the present invention uses a wireless backhaul structure for wirelessly connecting the core network and the small base station.

In the case of mobile WiMAX, when using wireless backhaul, a more precise time synchronization error standard (within 2 microseconds) is applied in consideration of radio signal interference.

As described above, when a small base station is connected to an uplink, downlink, and asymmetric wired network, it is difficult to secure accurate time synchronization with the existing IEEE 1588. In addition, when a small base station is installed using a wireless backhaul, more precise time synchronization is required than when using a wired network.

In the present invention, IEEE 802.11 based WLAN is used to synchronize the core network and the small base station. In the case of a WLAN, a beacon is periodically transmitted to inform an access terminal (AT) of an access point (AP), a transmission standard, a frequency band, a beacon transmission period, and AP ID information. That is, the beacon is always transmitted periodically even if there is no data to transmit from the access point. In the present invention, the beacons of the wireless LAN are synchronized with the clocks of the core network and transmitted, and the clock information of the core network and the small base station is restored by recovering clock information after receiving the beacons from the accessor terminal connected to the small base station. We propose a technique for synchronizing clocks.

There are two methods of connecting the core network and the small base station using a wireless backhaul and a wired network.

2 is a diagram of a system for synchronization according to an embodiment of the present invention when a core network and a small base station are connected by a wired network.

As shown in FIG. 2, the system is divided into a core network 100, a macro base station 110, and a wireless access point (AP) 130 connected to the macro base station 110, and the wireless access point 130. A wireless access terminal 140, a femtocell (150, hereinafter referred to collectively as a small base station for convenience) and a wired network IP network 160 that are wirelessly connected to receive a beacon from the wireless network.

First, in the case of the macro base station 110, a GPS signal is received using an antenna 120 (hereinafter referred to as a GPS module for convenience) installed outdoors, and the signal is received by the base station controller 115 and the core network ( Sharing with 110 allows the macro base station 110 and the core network 100 to be synchronized. Synchronization method between the macro base station and the core network using the GPS can be easily known to those skilled in the art, detailed description thereof will be omitted.

Thereafter, the timer 132 inside the wireless access point 130 is driven in synchronization with the GPS signal. The timer 132 informs the transmission time of the beacon in the wireless access point. For example, the timer is initialized to 1023, the timer value is decremented by 1 for every clock synchronized to the GPS, and the timer is set to transmit a beacon when the timer reaches zero. The timer then resets to 1023 on the next clock after zero. This will send a beacon every time the timer goes to 0 with a 1024 clock cycle.

That is, the timer 132 is driven using the GPS clock, and the transmission module 134 synchronizes with the timer 132 to periodically transmit the beacon so that the beacon is synchronized with the GPS clock.

The wireless accessor 140 attached to the small base station 150 receives the beacon, and the time information restoration module 142 in the wireless accessor 140 uses the time at which the beacon is received to time information of the core network. After the restoration, the information is transmitted to the small base station 150 through the synchronization information transmission module 148. Through this, the small base station 150 acquires time synchronization.

On the other hand, since a wired network is used for data transmission, data packets are transmitted from the core network 100 to the small base station through the IP network 160. On the other hand, the synchronization information is transmitted to the small base station 150 through the radio link using a beacon linked to the GPS.

3 is a diagram of a system for synchronization according to an embodiment of the present invention when the core network and the small base station use the WLAN backhaul.

As shown in FIG. 3, the system is largely connected wirelessly from the core network 100, the macro base station 110, and the wireless access point 130 and the wireless access point 130 connected to the macro base station 110. Wireless beacon terminal 140, receiving a beacon, and a small base station (150, femtocell).

First, in the case of the macro base station 110, the GPS signal is received using the GPS module 120 installed outdoors, and the signal is shared between the base station controller 115 and the core network 110. The 110 and the core network 100 are synchronized.

The macro base station 110 drives the timer 132 inside the wireless access point 130 again in synchronization with the GPS signal. This timer 132 informs the transmission time of the beacon in the wireless access point 130. For example, the timer is initialized to 1023, the timer value is decremented by 1 for every clock synchronized to the GPS, and the timer is set to transmit a beacon when the timer reaches zero. The timer then resets to 1023 on the next clock after zero. This will send a beacon every time the timer goes to 0 with a 1024 clock cycle.

In case of using the WLAN backhaul, both beacons and data packets are transmitted to the small base station 150 through the wireless backhaul. For this purpose, the wireless access point 130 includes a data packet module 136 and a multiplexer (MUX, 138). ) Is further included.

 The multiplexer (MUX, 138) module included in the wireless access point 130 transmits the beacon through the transmission module 134 and the data packet passing through the data packet module 136 in a timed manner.

The packet is received by the wireless accessor 140, which includes a demultiplexer module 144 (DEMUX), a time information restoration module 142, and a data decoder 146.

The demultiplexer module 144 classifies the received packet into a beacon and a data packet. The data decoder 146 decodes the separated data packet and transmits it to the small base station 150.

The time information restoration module 142 restores time information of the core network using the beacons. The restored information is transmitted to the small base station 150 through the synchronization information transmission module 148. The time information restored in the wireless access terminal 140 synchronizes the small base station 150 with the core network 100. Play a role.

4 is a flowchart illustrating a synchronization method of a small base station.

First, the macro base station 110 receives a GPS signal for synchronization with the core network from the GPS module 120 (S210).

Thereafter, the macro base station 110 causes the core network 100 to be synchronized using the GPS signal (S220).

Thereafter, the macro base station S210 drives the timer embedded in the wireless access pointer 130 using the synchronization information (S230), and the wireless access pointer 130 is linked to the timer to periodically operate the beacon. Create and transmit (S240).

Afterwards, the wireless access terminal 140 receives the beacon and restores clock information from the beacon (S250).

The small base station 150 is synchronized with the restored clock information, and as a result, the small base station 150 and the core network 100 are synchronized with each other.

5 is a block diagram illustrating in more detail the time information restoration module 142 of the wireless access terminal 140 shown in FIGS.

As shown in the figure, the time information restoration module 142 includes a time error calculation module 143, a time error correction module 144, a time error average module 145, and a beacon time synchronization module 146.

First, when the beacon is received, the time error calculation module 143 first measures the time when the beacon is received using a local clock. In addition, since the wireless access terminal 140 knows the period in which the wireless access point 130 transmits a beacon, the wireless access terminal 130 calculates an estimated time at which the beacon is received using the difference, and from the difference between the expected reception time and the actual reception time of the beacon. Calculate the time error.

The time error correction module 144 corrects the previously calculated time error by reflecting when the beacon transmission time is changed for data packet transmission in the wireless access pointer 130. For example, if you set the beacons to be sent at 1 ms intervals, t = 0, 1 ms, 2 ms,... Beacons should be sent to. However, if a data packet is being transmitted when the beacon is transmitted, the standard is defined to transmit the beacon after the transmission of the data packet is completed. Therefore, the beacon transmission time may be delayed for the transmission of the data packet. In the wireless access terminal 140, it is possible to know whether data packets are transmitted in the beacon receiving section, and thus, by calculating the beacon transmission delay time in the access pointer 130, the time error is corrected.

The time error average module 145 observes the time error thus calculated for a predetermined time, and estimates the average time error therefrom.

The beacon time synchronization module 146 feeds back the estimated average time error to a local time clock generator so that the local time clock is synchronized to the beacon reception time.

Through this process, the GPS clock of the core network and the transmission time of the beacons are synchronized, and the transmission time of the beacons and the local time clock of the wireless access terminal 140 attached to the small base station are synchronized. As a result, the small base station 150 and the core network 100 connected to the wireless access terminal 140 are time synchronized with each other.

FIG. 6 is a flowchart illustrating a calculation process performed in the time information restoration module 142 described with reference to FIG. 5 in detail.

The wireless access terminal 140 restores the information included in the received beacon to obtain a transmission period of the beacon (S310).

And using this to calculate the expected reception time of the beacon periodically received (S320).

Next, the beacon is to selectively receive only the beacon among the packets received in the radio access terminal 140 to calculate the actual received time (S330), using the local time clock (local time clock) the time the beacon is received Measured by (S340).

When the beacon expected reception time is defined as T1 and the beacon is actually received as T2, the time error T3 is calculated as a difference between T1 and T2 as shown in Equation 1 (S350).

T3 = T1-T2

Then, when the data packet is transmitted at the time when the beacon is transmitted, the beacon transmission time is delayed until the transmission of the data packet is completed. When the time when the beacon transmission is delayed is C, the time error T3 is expressed by Equation 2 below. By adding the C values as described above, correction is made in consideration of the transmission delay (S360).

T3 = T3 + C

Then, the average of the time error is estimated using the time error estimated for a certain time (S370). When the time error calculated by step S360 at time n is referred to as T3 (n), for example, when the arithmetic mean is taken for m hours and the average of the time error is estimated as follows.

t_offset = [T3 (n) + T3 (n-1) +... + T3 (n-m + 1)] / m

Equation 3 may be changed into other forms such as a finite impulse response (FIR) filter and an finite impulse response (IIR) according to an average estimation method of time error.

Thereafter, the local time clock is updated as follows using the finally estimated average estimation error (S380).

local_time = local_time + t_offset

The time clock of the core network 100 and the time clock of the small base station 150 are synchronized through steps S310 to S380 described above.

Meanwhile, the wireless access terminal 140 and the small base station 150 have been described as separate devices for convenience of description, but are not limited thereto. That is, of course, the function of the time information restoration module 142 of the wireless access terminal 140 may be mounted inside the small base station 150. 7 is a diagram illustrating an example of a base station 400 in which the functions of the wireless access terminal 140 described above are incorporated. As shown in FIG. 7, after receiving the beacon, the base station 400 includes a wireless access terminal including a time information restoration module 420 for restoring time information of a core network using the received beacon. Module 410 and a control module 430 for synchronizing with the core network using the restored time information.

So far, a small base station synchronization system and a synchronization method for the same have been described.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

The small base station synchronization system according to the present invention is a method for solving the synchronization of small base stations that cannot be solved by the conventional synchronization method. It is an invention with industrial applicability because it is not only sufficient but also practically evident.

1 is a diagram showing a system for synchronization between a core network and a small base station using a conventional IEEE1588,

2 is a diagram of a system for synchronization according to an embodiment of the present invention when a core network and a small base station are connected by wired network;

3 is a diagram of a system for synchronization according to an embodiment of the present invention when a core network and a small base station use a wireless LAN backhaul;

4 is a flowchart illustrating a synchronization method of a small base station;

FIG. 5 is a block diagram illustrating in more detail the time information restoration module of the wireless access terminal shown in FIGS.

6 is a flowchart for explaining in detail the calculation process performed in the time information restoration module described in FIG. 5;

7 is a block diagram of a small base station according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: core network 110: macro base station

120: GPS module 130: wireless access point

140: Wireless Excess Terminal 150: Small Base Station

Claims (19)

A base station synchronized with the core network; A wireless access point (ACCESS POINT) connected to the base station and transmitting beacons in synchronization with the core network; A radio access terminal (ACCESS TERMINAL) for generating synchronization information for performing synchronization with the core network by restoring clock information from the beacon after receiving the beacon; And And a small base station connected to the wireless access terminal and configured to perform synchronization with the core network using the synchronization information. The method of claim 1 The wireless access point is A GPS module for receiving a GPS signal for synchronization with the core network; And And a transmission module configured to periodically transmit a beacon in synchronization with the GPS signal. The method of claim 2 The transmission module And a built-in timer in synchronization with the GPS signal, and periodically generating and transmitting the beacon in association with the timer. The method of claim 1 The wireless access point is Further comprising a multiplexer (MUX) module for combining the beacons and data packets, The transmission module And a small base station synchronization system for transmitting the combined packet. After receiving the beacon from the outside, using the beacon to restore the time information of the core network, and using the restored time information to transmit the synchronization information for performing synchronization with the core network to the small base station Wireless access terminal device for the synchronization of small base stations. The method of claim 5 The wireless access terminal device A time information restoration module for restoring time information of a core network using the received beacon after receiving the beacon, and generating synchronization information for synchronizing with the core network using the restored time information; And And a synchronization information transmission module for transmitting the generated synchronization information to the small base station. The method of claim 6 The time information restoration module A time error calculation module for calculating a time error from the difference between the expected reception time and the actual reception time of the beacon; A time error correction module for correcting the time error by calculating a transmission delay time of a beacon; A time error average module for estimating an average of the corrected time error; And And a beacon time synchronization module for feeding back the estimated average time error to a local clock generator so that the local clock is synchronized to the reception time of the beacon. Excess terminal device. The method of claim 7, The time error calculation module When the beacon is received, the beacon actual reception time, which is the time when the beacon is actually received, is measured using a local clock, the beacon expected reception time is measured using the beacon period information, and the beacon actual reception is performed. A wireless access terminal device for synchronizing a small base station, using the difference between the time and the beacon expected reception time. The method of claim 6 The wireless access terminal device A demultiplexer (DEMUX) module for receiving packets from the outside and classifying the received packets into beacons and data packets; And And a data decoder module for processing the received data packet and transmitting the processed data packet to the small base station. And after receiving the beacon from the outside, recovering time information of the core network using the beacon, and synchronizing with the core network using the restored time information. The method of claim 10 The small base station An ACCESS TERMINAL module including a time information restoring module for restoring time information of a core network using the received beacon after receiving the beacon; And And a control module for synchronizing with the core network by using the restored time information. Beacon transmission step of transmitting a beacon in synchronization with the core network; And a synchronization performing step of restoring clock information from the beacon after receiving the beacon to perform synchronization with the core network. The method of claim 12, A GPS receiving step of receiving a GPS signal for synchronizing with the core network; The beacon transmission step And a beacon periodically transmitted in synchronization with the received GPS signal. The method of claim 13, The beacon transmission step And a built-in timer in synchronization with the received GPS signal, and periodically generating and transmitting the beacon in association with the timer. The method of claim 12, Further comprising a multiplexer step of combining the beacons and data packets, The beacon transmission step And transmitting the combined packet. The method of claim 12, The synchronization performing step A time information restoration step of restoring time information of a core network by using the received beacon after receiving the beacon; And And a synchronization control step of synchronizing with the core network using the restored time information. The method of claim 16 The time information restoration step A time error calculation step of calculating a time error from the difference between the expected reception time and the actual reception time of the beacon; A time error correction step of correcting the time error by calculating a transmission delay time of a beacon; A time error average step of estimating an average of the corrected time error; And And a beacon time synchronization step of feeding back the estimated average time error to a local clock generator so that a local clock is synchronized to a reception time of the beacon. . The method of claim 17 The time error calculation step When the beacon is received, the beacon actual reception time is measured by measuring the time when the beacon is received using a local clock, the beacon expected reception time is measured using the period information of the beacon, the beacon actual reception And calculating a time error using a difference between a time and the expected reception time of the beacon. The method of claim 15, A demultiplexer (DEMUX) step of receiving the combined packet and classifying the received packet into a beacon and a data packet; And And a data decoder step of processing the received data packet.

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