KR20070055233A - Method for synchronize gps time in a broadband wireless access communication system - Google Patents

Abstract

The present invention relates to a method for synchronizing GPS time through another base station having GPS in a base station without GPS. The present invention relates to a GPS receiver in a GPS time synchronization method in a broadband wireless access communication system. Searching for a second base station including a GPS receiver in a first base station that does not include a; and obtaining time of day (TOD) data from the searched second base station; and using the obtained TOD data Calculating an access point frame number (AFN); and generating an EVEN clock by using the AFN and performing time synchronization with the second base station.

BWA, OFDMA, TDD, GPS, TOD, RAS, AP, Sync, Ranging, AFN

Description

Satellite positioning system time synchronization method in broadband wireless access communication system {METHOD FOR SYNCHRONIZE GPS TIME IN A BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEM}

1 is a diagram schematically illustrating a structure of a communication system using a general OFDMA scheme;

2A and 2B schematically show examples of system configuration according to an embodiment of the present invention;

3 is a diagram illustrating a base station system timing diagram according to an embodiment of the present invention;

4 illustrates the relationship between the AFN value and the EVEN period according to an embodiment of the present invention;

5 is a diagram illustrating an accurate time and even clock recovery process according to an embodiment of the present invention;

6 is a diagram schematically illustrating an EVEN clock generation process according to an embodiment of the present invention;

7 is a diagram illustrating a clock recovery procedure according to an embodiment of the present invention;

8 illustrates a synchronization procedure according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband wireless access (BWA) communication system, and in particular, to a satellite positioning system (GPS) in a broadband wireless access communication system. It is about.

Commonly used technologies for providing data services to users in the current wireless communication environment include CDMA2000 Code Division Multiple Access 2000 1x Evolution Data Optimized (GPDMA), General Packet Radio Services (GPRS), and Universal Mobile Telecommunication Service (UMTS). And wireless LAN technologies such as 2.5 generation or 3 generation cellular mobile communication technology, and IEEE (Institute of Electrical and Electronics Engineers) 802.11 wireless local area network (hereinafter referred to as "LAN"). Divided into.

The most prominent feature of the 3rd generation cellular mobile communication technology focused on voice services over a circuit network is that it provides packet data services that enable users to access the Internet in a wide range of wireless communication environments. will be.

However, there is a limit in supporting a high speed packet data service in a cellular mobile communication network. For example, the CDMA2000 1xEVDO system, which is a synchronous mobile communication system, provides data rates of up to about 2.4 Mbps.

Meanwhile, in parallel with the evolution of these mobile communication technologies, various short range wireless access technologies such as IEEE 802.16 based wireless LANs have emerged. These techniques do not guarantee the same level of mobility as in cellular mobile communication systems. However, the short range wireless access technologies replace wired communication networks such as cable modems or digital subscriber lines (xDSLs) in hot spot areas or home networks, such as public places or schools. In the meantime, it has been proposed as an alternative for providing a high speed data service in a wireless environment.

However, when providing a high-speed data service over the wireless LAN described above, there are limitations in providing public network services to users due to extremely limited mobility and narrow service area as well as radio wave interference.

Therefore, efforts to overcome the above limitations have been made at various angles. For example, researches on portable Internet technologies that complement the advantages and disadvantages of cellular mobile communication systems and wireless LANs are being actively conducted. As a representative example of the portable Internet technology, which is currently being standardized and developed, researches on a wireless broadband Internet (WiBro) system are being actively conducted. The WiBro system can provide high-speed data services in mobile environments such as indoor / outdoor stop environment, walking speed, and medium / low speed (about 60 km / h) using various types of mobile terminals (MS).

The WiBro system is a technology that has evolved from the wireless local loop (WLL) technology of the 2.3 GHz band to include the 4th generation mobile communication business area, and has a wider business field than the 3rd generation IMT2000 (International Mobile Telecommunication 2000). Have For this reason, the WiBro is referred to as 3.5 generation mobile communication technology.

Meanwhile, broadband wireless access (BWA, Broadband) using time division duplex (hereinafter referred to as 'TDD') orthogonal frequency division multiple access (hereinafter referred to as 'OFDMA') scheme. Wireless Access (e.g., WiBro systems or next-generation 4G systems, etc.) are provided between downlink (BS) base stations (BSs) and base stations (BSs) that provide downlinks. The time synchronization between the terminal and the base station must be correct so that the frequency reuse factor of the system can be set to one.

Therefore, GPS synchronization is generally applied to support this. That is, all base stations, for example, access points (APs) are provided with a GPS receiver board (Receiver Board) to synchronize the clock (clock) of the system, the mobile terminals are in the air link signal of the base station The synchronization is tracked and restored to synchronize with the base station. In other words, on the Earth's orbit, certain GPSs are rotated along a defined orbit to broadcast their own exact ephemeris and system time, allowing them to determine their position via a GPS receiver board on Earth. have. The GPS receiving board calculates the relative reception times of GPS signals transmitted simultaneously from a plurality of, for example, at least four GPSs, to determine the correct time and its position.

On the other hand, the time synchronization obtained from the GPS is a TOD (Time Of Day), 1PPS (1 Pulse Per Second) signal. Here, the TOD represents data indicating a precise time of the current 1PPS starting from a certain criterion, for example, midnight January 6, 1980, and the 1PPS is accurate timing. As a signal, a base station, for example, an access point, synchronizes all clocks used in the system with the 1PPS signal.

As described above, in order to use the TDD OFDMA scheme in broadband wireless access communication, a GPS reception board for maintaining synchronization between all base stations or a predetermined timing board performing a function equivalent to the GPS reception board may be used. Must be mounted in the base station. That is, in order to synchronize with the GPS signal received from the base station, a GPS reception board or the like must be mounted. However, this method increases the price of the entire system because of the high cost of the GPS receiver board, and also poses a great burden in designing a small base station. In addition, in order to receive the GPS signal as described above, when the base station is installed, it is necessary to install the GPS antenna in an outdoor location or to install an additional antenna. As a result, it is not easy to install a small base station for system expansion, and a lot of cost burden occurs.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for synchronizing GPS time in a broadband wireless access communication system.

Another object of the present invention is to provide a scheme for synchronizing GPS time in a small base station without GPS in a broadband wireless access communication system.

It is still another object of the present invention to provide a method for synchronizing GPS time synchronization using a predetermined base station including GPS in a small base station without GPS in a broadband wireless access communication system.

It is still another object of the present invention to provide a method for synchronizing GPS time synchronization without a GPS receiver in a base station by using time synchronization and TOD data transmitted from a base station equipped with a GPS receiver.

Method according to an embodiment of the present invention for achieving the above objects; A method for synchronizing satellite positioning system (GPS) time in a broadband wireless access communication system, the method comprising: searching for a second base station including a GPS receiver in a first base station not including a GPS receiver; Acquiring time of day (TOD) data; calculating an access point frame number (AFN) using the acquired TOD data; generating an EVEN clock using the AFN; Includes the process of performing time synchronization.

Method according to an embodiment of the present invention for achieving the above objects; In a GPS time synchronization method in a broadband wireless access communication system, receiving time of day (TOD) data from a predetermined base station including a GPS receiver and estimating using the received TOD data Calculating a predetermined value for acquiring an access point frame number (AFN); calculating the estimated AFN using the predetermined value; and calculating a predicted AFN predicted at a next time point using the estimated AFN. And generating an even (EVEN) clock using the calculated predictive AFN, and performing time synchronization with the predetermined base station using the EVEN clock and the TOD data.

Method according to an embodiment of the present invention for achieving the above objects; A time synchronization method in a base station without a satellite positioning system (GPS) receiver in a broadband wireless access communication system, the base station scanning a predetermined base station including a GPS receiver among neighboring base stations adjacent to the base station; If there is a predetermined neighbor base station to be scanned, a process of performing a clock restoration procedure with the neighboring base station, a process of performing a synchronization procedure after performing the clock restoration procedure, and generating an even (EVEN) clock after performing the synchronization procedure It includes the process of doing.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

Prior to the description of the present invention, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, the inventors in their best way For the purpose of explanation, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention on the basis of the principle that it can be appropriately defined as the concept of term. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The present invention proposes a global positioning system (BWA) in a broadband wireless access (BWA) system, for example, a wireless broadband internet (WiBro) system. GPS synchronization method). In particular, in the embodiment of the present invention by receiving and processing the signal of the base station having a GPS in order to synchronize in the base station (BS, BS) without GPS, a method that can synchronize the time synchronization in the base station without GPS Suggest.

An embodiment of the present invention proposes a GPS signal processing scheme for receiving GPS signals by receiving the signal of the base station having the GPS, and proposes a method of restoring GPS time information through the GPS signal.

In an embodiment of the present invention, a broadband wireless access using time division duplex (hereinafter, referred to as 'TDD') orthogonal frequency division multiple access (hereinafter, referred to as 'OFDMA') scheme. In the time synchronization process of the base station in the system, a base station without a GPS receiver is proposed to obtain a GPS synchronization. In the following description, the base station preferably includes an access point (hereinafter referred to as "AP") or a radio access station (hereinafter referred to as "RAS").

Meanwhile, in order to use the TDD OFDMA scheme in a broadband wireless access communication system, a GPS reception board for maintaining synchronization between all base stations or a predetermined timing board performing a function equivalent to the GPS reception board is mounted in the base station. Should be. Hereinafter, a method for synchronizing time between base stations having a general GPS receiver board will be described with reference to FIG. 1 as a general broadband wireless access communication system, for example, a WiBro system.

1 is a diagram schematically illustrating a structure of a communication system using a general OFDMA scheme. In particular, FIG. 1 is a diagram illustrating a synchronization method between base stations in a system.

Referring to FIG. 1, a WiBro system includes a mobile station (MS), for example, a first mobile terminal 101 and a second mobile terminal 103, which are largely connected to a WiBro system, and the mobile terminals 101 and 103. Wireless communication standard with the base station (BS) 105, 107, which is a network equipment that processes the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, and a mobile terminal (101, 103) connected to a WiBro system. Authentication, media access control (MAC) protocol processing, Internet Protocol (IP) address allocation, and routing. An access control router (ACR) 109, which is a network equipment to perform, and a GPS 111 for maintaining synchronization between all base stations. Here, the base stations 105 and 107 include an access point (AP) or a radio access station (RAS) in a WiBro system.

In the WiBro communication system having the above-described configuration, in order to use the TDD OFDMA scheme, as shown in FIG. 1, maintaining synchronization between all base stations, for example, the RAS (AP) 105 and the RAS (AP) 107. For all base stations, a GPS reception board for receiving and processing a signal transmitted from the GPS 111 or a timing board for performing such a function should be provided.

That is, in the prior art, in order for the RAS or the AP to receive the GPS signal and synchronize the time, the GPS receiver must be installed in each device. Here, the GPS signal includes TOD (Time Of Day) data and 1PPS (Pulse Per Second) signal obtained from the GPS 111. The TOD represents data indicating the exact time of the current 1PPS starting from a certain reference time point, and the 1PPS is an accurate timing signal. All clocks used in the system are used for the 1PPS signal in a base station, for example, an AP. Will be used in synchronization.

On the other hand, in general, for the GPS time synchronization, the price of the entire system increases because the GPS receiver having a high product cost must be installed in all base stations. In addition, in designing a small base station, the addition of the GPS receiver is a big burden. In addition, in order to receive a GPS signal from the GPS, it is necessary to install an outdoor GPS antenna or an additional antenna for the GPS reception.

As described above, in order to receive GPS signals from a base station such as a RAS or an AP to synchronize time, a GPS receiver must be installed in the base station. Accordingly, in the embodiment of the present invention, in order to improve the problems described above, a base station equipped with an existing GPS receiver, for example, a base station not including a GPS receiver using time synchronization and TOD data transmitted by the AP, for example, the GPS at the AP. We propose a scheme that allows GPS time synchronization without a receiver.

That is, the embodiment of the present invention relates to a method for restoring accurate GPS time and synchronization in a base station that is not equipped with a GPS receiver, for example, a small AP or a small RAS. To this end, an embodiment of the present invention proposes a time inference method using a frame clock number and a time recovery method using the frame clock number and TOD.

In the following description of the operation according to an embodiment of the present invention, the general theory of synchronization acquisition in a communication system using the OFDMA scheme is a well known well-known technique, which is outside the scope of the present invention, and thus the detailed description thereof will be omitted. Shall be. Therefore, in the following detailed description of the present invention, it should be noted that only parts necessary for GPS signal recovery according to an embodiment of the present invention are described.

2A and 2B are diagrams schematically showing examples of a system configuration according to an embodiment of the present invention.

2A, a system according to an exemplary embodiment of the present invention includes a mobile terminal connected to a WiBro system, for example, a first mobile terminal 201 and a second mobile terminal 203, and the mobile terminals 201 and 203. Network equipment that performs functions such as MAC protocol processing, IP address allocation, and routing to the base stations 205 and 207, which are network equipment that processes wireless access standards, and mobile terminals 201 and 203 that access WiBro systems. An access control router (ACR) 209 and a GPS 211 for maintaining synchronization between all base stations.

In FIG. 2A, the base station 205 represents an AP or RAS without a GPS receiver, and the base station 207 represents an AP or RAS with a GPS receiver.

As shown in FIG. 2A, FIG. 2A illustrates a base station equipped with a GPS receiver as an M_RAS 207 and a base station without a GPS receiver as an S_RAS 205. The M_RAS 207 and the S_RAS 205 preferably have a network designed such that there are two connection passages, for example, an air link and a line interface shown in FIG. 2A. Further, reference numeral a and reference numeral b denote transmission lines based on IP, and reference numeral c denotes a connection path using a radio frequency (hereinafter, referred to as 'RF').

In the WiBro system using the TDD OFDMA scheme, the M_RAS 207 acquires a signal synchronized with the GPS 211, and this synchronized signal may be represented as shown in FIG. 3.

3 is a diagram illustrating a RAS system timing diagram according to an embodiment of the present invention.

Referring to FIG. 3, the M_RAS 207 is a signal synchronized with the GPS 211 and, as shown in FIG. 3, a system clock, a frame clock, and an even clock. For example, a Pulse Per 2 Seconds (PP2S) signal may be generated. In addition, an AP frame number (hereinafter referred to as "AFN") of 24-bit data whose time synchronization coincides with the frame clock is generated. Definition of each sync signal is as follows.

System clock: Synchronization signal for data transmission.

Frame Clock: The physical size and time synchronization signal of the data transmitted over the Air Link.

-EVEN Clock: This is a synchronization signal generated based on an even number of 1PSS received from GPS, and can be combined with TOD information to generate an accurate time.

-TOD: The first GPS 1PPS is calculated based on a setting reference time point, for example, Midnight January, 6, 1980, so that the 1PPS currently received is the number of 1PPS, and thus the correct time. Information can be provided.

Next, referring back to FIG. 2A, the S_RAS 205 may restore the frame clock synchronized with the M_RAS 207 through the path indicated by reference numeral c, and may use the received data. The AFN value can be found. This series of operations is currently defined as a specification between RAS and mobile terminals in commercial WiBro systems.

Here, the path of the reference a and the path of the reference b may receive the TOD data received by the M_RAS 207 from the S_RAS 205 by requesting the ACR 209 or the M_RAS 207. A passage can be provided.

Next, FIG. 2B is more specific for the configuration of FIG. 2A. In particular, in FIG. 2B, a small base station, for example, the S_RAS 205, which is not equipped with the GPS receiver shown in FIG. An example of providing a service to the terminal 201 is shown. The description of FIG. 2B corresponds to the description of FIG. 2A, and detailed description thereof will be omitted herein as the same operation is performed.

On the other hand, when the TDD technique is applied to a communication system using the OFDMA scheme, a ranging process is required to adjust an accurate frame time offset and adjust power between a mobile terminal and a base station. Herein, the ranging is to secure time synchronization of a physical layer, and rangings used in a broadband wireless access communication system include initial ranging and maintenance ranging. Periodic ranging, bandwidth request ranging, and the like. A brief definition of the rangings is as follows.

The initial ranging is performed when the base station requests from the base station to acquire synchronization with the mobile terminal, and the initial ranging sets a correct time offset between the mobile terminal and the base station and transmit power ( Ranging is performed to adjust transmit power.

The periodic ranging refers to ranging periodically performed by a mobile terminal that adjusts a time offset and a transmission power with the base station through the initial ranging to adjust channel conditions with the base station. The mobile terminal performs the periodic ranging by using predetermined ranging codes allocated for the periodic ranging.

The bandwidth request ranging is a ranging in which a mobile station having adjusted a time offset and a transmission power with a base station through the initial ranging requires bandwidth allocation to perform actual communication with the base station.

As described above, the operation according to the embodiment of the present invention is used for searching and maintaining the correct frame clock synchronization and controlling traffic through the time offset function of the ranging as described above. Receiving the AFN to obtain GPS 1PPS time synchronization.

4 is a diagram illustrating an AFN value and an EVEN period relationship according to an embodiment of the present invention.

Referring to FIG. 4, in the IEEE 802.16 standard, 24-bit AFN data increases in number every 5 msec frame clock, and maintains modulation 1677216. Therefore, in the M_RAS 207 illustrated in FIGS. 2A and 2B, an AFN generation condition is inserted at the initial setting time, that is, '0' at the first 5 msec from midnight January 6, 1980. If conditions are set, all M_RAS including GPS receiver can unify the AFN value using GPS synchronization.

The S_RAS 205 may track the 5 msec and maintain synchronization within a few Hz offset range compared to the M_RAS 207. At this time, since the S_RAS 205 does not know the exact time and EVEN clock, it cannot be restored. Accordingly, an embodiment of the present invention proposes a method for restoring an exact clock and an even clock in the S_RAS 205 through the procedure and the arrangement described in FIG. 5.

5 is a diagram illustrating an accurate time and EVEN clock recovery process between base stations according to an embodiment of the present invention.

As shown in FIG. 5, an accurate time synchronization and EVEN clock recovery procedure between a base station such as a first RAS 510 that does not include a GPS receiver and a base station such as a second RAS 530 that includes a GPS receiver may be performed as follows. Same as

Referring to FIG. 5, first, the first RAS 510 and the second RAS 530 perform initialization and operation, respectively (steps 501 and 503). Thereafter, the first RAS 510 scans the peripheral RAS including the GPS receiver after the initialization, for example, the second RAS 530 (step 505).

When the second RAS 530 including the GPS receiver is scanned, the first RAS 510 sends a ranging request message to the second RAS (hereinafter, referred to as 'RNG-REQ'). The mobile station transmits the request to the mobile station in step 507. Then, when the second RAS 530 receives a ranging request from the first RAS 510, that is, the RNG-REQ message, the second RAS 530 receives a ranging response as a response to the ranging request. -RSP ') and the like through a message (step 509).

Next, when the first RAS 510 receives the ranging response from the second RAS 530, that is, the RNG-RSP message, the first RAS 510 recovers a frame clock for synchronization with the second RAS 530. recovery) and AFN tracking (steps 511 and 513). After the AFN tracking is completed, the first RAS 510 requests the second RAS 530 to acquire TOD data (step 515). Then, the second RAS 530 transmits TOD data corresponding to the TOD request of the first RAS 510 to the first RAS 510 (step 517).

Next, when the first RAS 510 obtains TOD data from the second RAS 530, the first RAS 510 calculates a predictive AFN using the obtained TOD data (step 519). Subsequently, the first RAS 510 performs EVEN clock synchronization using the calculated predictive AFN (step 521). When the EVEN clock synchronization is completed, the first RAS 510 restores the correct time by using the EVEN clock and the obtained TOD value, and through this, time synchronization with the second RAS 530. Perform step 523.

In the following, the procedure illustrated in FIG. 5, that is, a method of recovering the correct time and the EVEN clock will be described in detail.

First, the first RAS 510 that does not include a GPS receiver searches for a base station that includes a GPS receiver and, when the base station to be searched, for example, the second RAS 530 is searched, contacts the second RAS 530. Perform the ranging procedure. Then, when the ranging procedure between the first RAS 510 and the second RAS 530 is normally completed, the first RAS 510 restores a frame clock and calculates an estimated AFN. Then, the first RAS 510 obtains TOD data from the second RAS 530 corresponding to the estimated AFN.

In this case, when the first RAS 510 obtains TOD data from the second RAS 530, the first RAS 510 calculates a prediction AFN using the TOD data. At this time, the first RAS 510 performs the following processing to calculate the prediction AFN.

First, the first RAS 510 obtains a predetermined value for calculating the estimated AFN by using the obtained TOD data and the AFN cycle through the process as shown in Equation 1 below.

As shown in Equation 1, the first RAS 510 first divides the TOD data (dddddddddd sec) received from the second RAS 530 by an AFN period (83886.08 sec), for example, a predetermined value. , xxxx (lot) .yyyy (rest).

Subsequently, the first RAS 510 obtains the remaining value 0.yyyy that discards the xxxx corresponding to the quotient from the calculated predetermined value, that is, xxxx.yyyy. Then, the estimated AFN is calculated using Equation 2 using the remaining value 0.yyyy.

In Equation 2, the cal_AFN represents an estimated AFN estimated at the last EVEN time in consideration of delay, and the AFN period is obtained by multiplying a frame clock by an AFN value defined in the standard. The offset value 200 represents the number of frame clocks that fall within one second.

Next, the first RAS 510 uses the estimated AFN (cal_AFN) calculated as in Equation 2, and predicts an AFN (pre_AFN) predicted at the next EVEN time as shown in Equation 3 below. Calculate

In Equation 3, the pre_AFN represents a predicted AFN that should come out at the next EVEN time, and the offset 400 represents the number of frame clocks that fall within the EVEN time to predict the pre_AFN. The reason for calculating the pre_AFN is that the TOD delay received by the first RAS 510 through the IP network is taken into consideration. In addition, the offset 400 is variable. For example, if the delay difference between the time information checked through cal_AFN and the TOD time received by the first RAS 510 differs within 2 seconds or more and within 4 seconds, the offset (400) value is generated for 4 seconds. The delay can be buffered by substituting the number of frame clocks.

Next, the first RAS 510 compares the estimated AFN (cal_AFN) and the predicted AFN (pre_AFN) restored through a path with the second RAS 530 through, for example, an air link, and an EVEN clock (EVEN). clock) finds when to create Finally, the first RAS 510 generates the EVEN clock at the time of generating the EVEN clock, and restores the correct time by applying the TOD value obtained from the second RAS 530.

Next, the EVEN clock generation process according to the embodiment of the present invention as described above with reference to FIGS. 6 to 8 will be described in more detail.

6 is a diagram schematically illustrating an EVEN clock generation process according to an embodiment of the present invention.

Referring to FIG. 6, the base station performs an initialization process for generating an EVEN clock. That is, the base station proceeds to step 603 after power on in step 602. When the base station powers on in step 603, the base station scans a RAS including a neighboring base station, for example, a GPS receiver, adjacent to the base station, and then proceeds to step 605.

In step 605, the neighbor base station scan result is checked. If there is no neighbor base station to be scanned, the process proceeds to step 603, and if there is a neighbor base station to be scanned, step 607 is performed. When the neighboring base station is scanned, the base station performs the clock recovery procedure in step 607 and then proceeds to step 609 to perform a synchronization procedure and proceeds to step 611. Finally, the base station generates an EVEN clock through the clock recovery procedure and the synchronization procedure in step 611.

Next, the clock recovery procedure of step 607 and the synchronization procedure of step 609 will be described in more detail with reference to FIGS. 7 and 8, respectively.

7 is a diagram illustrating a clock recovery procedure according to an embodiment of the present invention.

Referring to FIG. 7, the clock recovery procedure illustrated in step 607 of FIG. 6 is described. First, in step 701, the base station performs a ranging request to the scanned neighboring base station, and then receives a corresponding response. Proceed to step. That is, the base station requests a ranging by transmitting an RNG-REQ message to the scanned neighbor base station, and receives a ranging response from the neighbor base station through an RNG-RSP message. In step 703, when the ranging response is received from the neighboring base station, the base station restores the AFN and the frame clock, and then proceeds to step 705.

When the AFN and the frame clock are restored, the base station requests TOD data from the neighboring base station in step 705 and receives a response thereto in step 707. That is, the base station transmits a TOD request (TOD-REQ) message to the neighboring base station to request TOD data, and receives the TOD data through the TOD response (TOD-RSP) message from the neighboring base station.

Then, the base station checks the TOD data obtained from the neighboring base station in step 707, and checks whether the TOD data satisfies the EVEN clock. In this case, if the TOD data does not satisfy the EVEN clock, the process proceeds to step 705 to perform a TOD data request again. If the TOD data satisfies the EVEN clock, the synchronization procedure of step 609 is performed.

8 is a diagram illustrating a synchronization procedure according to an embodiment of the present invention.

Referring to FIG. 8, the synchronization procedure shown in step 611 of FIG. 6 is described. First, in step 801, the base station acquires TOD data and AFN periods obtained from the neighboring base stations, as shown in Equation (1). After a predetermined value for calculating the estimated AFN is calculated using the cycle), the process proceeds to step 803. In step 803, the base station determines whether a quotient exists in the predetermined value obtained in step 801. That is, as shown in Equation 1, it is checked whether a quotient exists in the predetermined value obtained by dividing the acquired TOD data by an AFN period. Subsequently, the process proceeds to step 805 or 807 corresponding to the check result, calculates an estimated AFN value according to Equation 2, and then proceeds to step 809.

Specifically, if there is a quotient in step 803, the flow proceeds to step 805 to discard the portion corresponding to the quotient from the obtained predetermined value, and calculates the estimated AFN as shown in Equation 2 using only the remaining values. Calculate. If there is no quotient in step 803, the process proceeds to step 807 to calculate an estimated AFN using the obtained TOD data.

Next, in step 809, the base station calculates the prediction AFN as shown in Equation 3 using the estimated AFN calculated in step 805 or 807, and then proceeds to step 811. Finally, in step 811, the base station calculates an EVEN time counter for searching for an EVEN clock generation time and then generates the EVEN clock in step 611 at the generation time of the EVEN clock corresponding to the EVEN time counter. . In this case, the EVEN time counter may be represented by Equation 4 below.

As shown in Equation 4, the EVEN time counter indicates a process of executing the EVEN clock generation without searching for the EVEN clock generation time. Specifically, the EVEN time output time point is obtained through the AFN once at the initial stage of power-up and operation of the base station. Then, the EVEN time can be generated by generating the EVEN time whenever the AFN of the value obtained by adding the number of AFNs generated during the EVEN time, for example, 2 seconds, to the pre_AFN that has been calculated.

As described above, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are of course possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below, but also by the equivalents of the claims.

As described above, according to the satellite positioning system time synchronization method in the broadband wireless access communication system of the present invention proposed in the present invention, the GPS time synchronization can be efficiently adjusted even in a base station without GPS in the broadband wireless access communication system. Has In a base station not equipped with a GPS receiver according to the present invention, time may be synchronized through a base station equipped with a GPS receiver. That is, the present invention has an advantage of accurately matching GPS time synchronization even in a base station without a GPS receiver using time synchronization and TOD data transmitted from a base station equipped with a GPS receiver. As a result, it is easy to expand the micro base station installed in an indoor environment where GPS signals are difficult to receive. As described above, since a small base station can be implemented without a GPS receiver installed in a room where GPS signals are difficult to receive, there is an advantage of reducing the cost burden of the system design.

Claims (23)

In the satellite positioning system (GPS) time synchronization method in a broadband wireless access communication system, Searching for a second base station including a GPS receiver in a first base station not including a GPS receiver, Obtaining time of day (TOD) data from the searched second base station; Calculating an access point frame number (AFN) using the obtained TOD data; Generating an EVEN clock using the AFN and performing time synchronization with the second base station. The method of claim 1, The AFN calculation process, Obtaining a predetermined value for calculating an estimated AFN using the acquired TOD data and an AFN cycle; Calculating an estimated AFN using the remaining value of discarding the portion corresponding to the quotient from the calculated predetermined value; And calculating a predictive AFN predicted at a next EVEN time by using the estimated AFN. The method of claim 2, The predetermined value is calculated as follows.

The method of claim 2, And the estimated AFN is calculated as follows.

However, cal_AFN represents an estimated AFN estimated at the last EVEN time in consideration of delay, and the AFN period represents a value calculated by multiplying a frame clock by an AFN value defined in the standard. offset (200) represents the number of frame clocks that fall within one second. The method of claim 2, The prediction AFN is calculated as follows.

However, pre_AFN represents a predicted AFN that should come out at the next EVEN time, and offset (400) represents the number of frame clocks that fall within the EVEN time to predict the pre_AFN. The method of claim 1, After calculating the AFN, searching for an even (EVEN) clock generation time using the AFN, and generating the EVEN clock at the found EVEN clock generation time. The method of claim 6, The generation time point of the EVEN clock is obtained as follows.

In the satellite positioning system (GPS) time synchronization method in a broadband wireless access communication system, Receiving time of day (TOD) data from a predetermined base station including a GPS receiver, Calculating a predetermined value for obtaining an estimated access point frame number (AFN) using the received TOD data; Calculating the estimated AFN using the predetermined value; Calculating a predictive AFN predicted at a next time point using the estimated AFN; Generating an even clock using the calculated prediction AFN; And synchronizing time with the predetermined base station using the EVEN clock and the TOD data. The method of claim 8, Restoring a frame clock for synchronization with the predetermined base station when a predetermined base station including the GPS receiver is found. The method of claim 8, The predetermined value is calculated as follows.

The method of claim 8, And the estimated AFN is calculated as follows.

However, cal_AFN represents an estimated AFN estimated at the last EVEN time in consideration of delay, and the AFN period represents a value calculated by multiplying a frame clock by an AFN value defined in the standard. offset (200) represents the number of frame clocks that fall within one second. The method of claim 8, The prediction AFN is calculated as follows.

However, pre_AFN represents a predicted AFN that should come out at the next EVEN time, and offset (400) represents the number of frame clocks that fall within the EVEN time to predict the pre_AFN. The method of claim 8, After calculating the prediction AFN, searching for an EVEN clock generation time using the AFN, and generating the EVEN clock at the searched EVEN clock generation time. The method of claim 13, The generation time point of the EVEN clock is calculated as follows.

A time synchronization method in a base station without GPS reception in a broadband wireless access communication system, The base station scans a predetermined neighbor base station including a GPS receiver among neighboring base stations adjacent to the base station; Performing a clock recovery procedure with the neighboring base station if the predetermined neighboring base station is scanned; Performing a synchronization procedure after performing the clock recovery procedure; After performing the synchronization procedure, time synchronization method in a base station without a GPS receiver comprising the step of generating an even (EVEN) clock. The method of claim 15, The clock recovery procedure, Requesting ranging from the scanned neighboring base station and receiving a corresponding response; Restoring an access point frame number (AFN) period and frame clock upon receiving the ranging response; After the AFN cycle and clock recovery, requesting time of day (TOD) data from the neighboring base stations and receiving a response thereto; Checking TOD data obtained from the neighboring base station; If the TOD data satisfies an even (EVEN) clock, performing the synchronization procedure. The method of claim 15, The synchronization procedure, Calculating a predetermined value using TOD data and an AFN cycle obtained from the neighboring base stations; Discarding a portion corresponding to the quotient from the calculated predetermined value and calculating an estimated AFN using only the remaining values; Calculating a predictive AFN at the next EVEN time point using the calculated estimated AFN; Calculating an EVEN time counter after calculating the prediction AFN; And generating an EVEN clock corresponding to the EVEN time counter. The method of claim 17, The predetermined value is calculated as follows. Time synchronization method in a base station without a GPS receiver.

The method of claim 17, After calculating the predetermined value, checking whether a quotient exists at the predetermined value; If the quotient exists, discarding a portion corresponding to the quotient from the obtained predetermined value and calculating the estimated AFN using only the remaining values; If the quotient does not exist, calculating the estimated AFN using the obtained TOD data, the time synchronization method in a base station without a GPS receiver. The method of claim 17, The estimation AFN calculation is calculated as follows.

However, cal_AFN represents an estimated AFN estimated at the last EVEN time in consideration of delay, and the AFN period represents a value calculated by multiplying a frame clock by an AFN value defined in the standard. offset (200) represents the number of frame clocks that fall within one second. The method of claim 17, The prediction AFN calculation is calculated as follows.

However, pre_AFN represents a predicted AFN that should come out at the next EVEN time, and offset (400) represents the number of frame clocks that fall within the EVEN time to predict the pre_AFN. The method of claim 15, The generating of the EVEN clock may include: calculating an EVEN time counter by comparing the estimated AFN and the predicted AFN; Checking a time point for generating an EVEN clock by using the calculated EVEN time counter; And generating the EVEN clock at the identified EVEN clock generation time. The method of claim 22, And calculating the EVEN time covenant as follows.

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