WO2002035734A1 - Apparatus and method for acquiring synchronization - Google Patents

Apparatus and method for acquiring synchronization Download PDF

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Publication number
WO2002035734A1
WO2002035734A1 PCT/KR2000/001214 KR0001214W WO0235734A1 WO 2002035734 A1 WO2002035734 A1 WO 2002035734A1 KR 0001214 W KR0001214 W KR 0001214W WO 0235734 A1 WO0235734 A1 WO 0235734A1
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WO
WIPO (PCT)
Prior art keywords
synchronization signal
time
signal
communication medium
transmitting
Prior art date
Application number
PCT/KR2000/001214
Other languages
French (fr)
Inventor
Ha-Jae Jeung
Jun-Woo Lee
Sung-Cheol Hong
Original Assignee
Sk Telecom Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sk Telecom Co., Ltd. filed Critical Sk Telecom Co., Ltd.
Priority to PCT/KR2000/001214 priority Critical patent/WO2002035734A1/en
Publication of WO2002035734A1 publication Critical patent/WO2002035734A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/204—Multiple access
    • H04B7/212—Time-division multiple access [TDMA]
    • H04B7/2125—Synchronisation

Definitions

  • the present invention relates to an apparatus and method for acquiring synchronization in a communication system; particularly to a synchronization signal transceiving apparatus and its synchronization acquiring method, which operate a base station using a code division multiple access (CDMA) modulation technique.
  • CDMA code division multiple access
  • the transceiving system comprises a plurality of base stations 110 and 111, at least one mobile station 120, a multiplicity of global positioning system (GPS) receivers 130 and 131, and a plurality of GPS satellites 140-143.
  • GPS global positioning system
  • Terrestrial GPS receivers 130 and 131 can track a maximum 5 to 8 number of GPS satellites at the same time and receive very accurate synchronization and time information (TOD : Time of Day) from satellites, which the receivers are tracking.
  • TOD Time of Day
  • the terrestrial GPS receivers 130 and 131 After receiving synchronization signals from GPS satellites being tracked, the terrestrial GPS receivers 130 and 131 provide base stations with a synchronization signal having a lowest tolerance (i.e., typically less than 0.8 msec) .
  • the base stations transmit signals synchronized to the synchronization signal provided from the receivers and, thereafter, all of the base stations are synchronized to each other. As a result, it is possible for the mobile station 120 to accomplish a soft/softer handoff between base stations or sectors of base station.
  • a domestic mobile communication service may not be effectively performed when there happen a failure in GPS satellite or a situation in which users have to pay for using the GPS satellites.
  • a primary object of the present invention to provide a synchronization signal transceiving apparatus capable of acquiring synchronization through the use of a certain communication medium (e.g., Koreasat Mugunghwa) without depending on GPS satellites provided by foreign countries when operating CDMA base stations by transmitting a synchronization signal required to operate a CDMA base station from a transmitting end to a communication medium, allowing all of remote CDMA base stations to received the synchronization signal from the communication medium, and interpreting information for the synchronization signal to thereby estimate a synchronization signal approximating t'o the original synchronization signal, and synchronization acquiring method of the synchronization signal transceiving apparatus.
  • a certain communication medium e.g., Koreasat Mugunghwa
  • an apparatus for acquiring synchronization in a communication system including: a transmitter for generating, in a predetermined time period, a synchronization signal and a preamble signal of the synchronization signal, transmitting the generated signals to a communication medium, and providing the communication medium with time information in response to the synchronization signal; and a receiver for receiving the signals transmitted via the communication medium, extracting, based on the received signals, an equivalent synchronization signal which is generated at the same moment when the synchronization signal is produced at the transmitter, detecting original time information transferred from the transmitter based on the extracted equivalent synchronization signal, providing a base station with the time information, estimating a generation time of the synchronization signal by using synchronization signals transmitted for a preset time via the communication medium, and providing the base station with the synchronization signal according to the estimated result.
  • a method for acquiring synchronization in a communication system including the steps of: (a) generating a synchronization signal in a predetermined time period and transmitting the synchronization signal to a communication medium; (b) transmitting time information to the communication medium according to whether or not the synchronization signal is generated at an even second; (c) producing a preamble signal of the synchronization signal in a preset time after the step (b) is performed, and transmitting the preamble signal to the communication medium; and (d) at a synchronization signal receiving end, estimating a generation time of the synchronization signal transmitted through the communication medium by using the synchronization signal and the preamble signal received from the communication medium, and selectively providing the synchronization signal or the time information at the estimated generation time to a base station.
  • Fig. 1 shows a block diagram of a transceiving apparatus for use in explaining a conventional synchronization signal acquiring method
  • FIG. 2 illustrates a block diagram of a synchronization signal transceiving apparatus in a communication system in accordance with the present invention
  • Figs. 3A and 3B exemplify a synchronization signal transceiving method for use in the communication system in accordance with the present invention
  • Fig. 4 provides a flow chart of showing a synchronization acquiring method for use in the communication system in accordance with the present invention
  • Fig. 5 is a flow chart of describing a synchronization signal transmitting method in accordance with the present invention
  • Fig. 6 depicts a flow chart of illustrating a synchronization signal receiving method in accordance with the present invention.
  • the synchronization signal transceiving apparatus comprises a synchronization signal transmitting unit 210 for transmitting a synchronization signal, and synchronization signal receiving units 220 and 230 for receiving the synchronization signal which is outputted from the synchronization signal transmitting unit 210 and then transmitted via a communication medium such as a Koreasat Mugunghwa 240, extracting an equivalent synchronization signal corresponding to the received synchronization signal, and delivering the received synchronization signal to base stations 250 and 251.
  • a communication medium such as a Koreasat Mugunghwa 240
  • a mobile station 260 can perform a soft/softer handoff in a base station which provides a communication service to the mobile station 260.
  • the synchronization signal transmitting unit 210 includes a synchronization signal generator 211 for producing the synchronization signal in a predetermined time period, a time information generator 212 for providing time information according to the synchronization signal transferred from the synchronization signal generator 211, and a modem 213 for modulating the synchronization signal and the time information supplied from the time information generator 212 and transmitting the modulated information.
  • the synchronization signal transmitting unit 210 modulates the synchronization signal and the time information by using the modem 213 and transmits the modulated information.
  • the time information generator 212 checks whether or not the synchronization signal delivered thereto is generated at an even second. If it is determined that the synchronization signal is produced at the even second, the time information generator 212 transmits the synchronization signal and then outputs time information (i.e., year, month, day, hour, minute, second and the like) .
  • Each of the synchronization signal receiving units 220 and 230 includes a modem 221, a signal processor 222 and a time information detector 223.
  • the modem 221 modulates a signal transmitted through the Koreasat Mugunghwa 240 that is the communication medium.
  • the signal processor 222 receives the modulated signal provided from the modem 221, extracts, based on the received signal, the equivalent synchronization signal produced at the same time as the synchronization signal is generated at the synchronization signal transmitting unit 210 to thereby provide the base station 250 and 251 with the equivalent synchronization signal, estimates a generation time of the synchronization signal by using signals modulated by the modem 221 for a preset time, and then provides the base station 250 and 251 with a synchronization signal corresponding to the estimated generation time.
  • the time information detector 223 receives the synchronization signal extracted by the signal processor 222, detects original time information transmitted from the synchronization signal transmitting unit 210 by using the received synchronization signal, and delivers the detected time information to the base station 250 and 251.
  • FIGs. 3A and 3B there are explained the operations of the synchronization signal transceiving apparatus and its synchronization acquiring method for use in the communication system in accordance with the present invention.
  • the operation of the synchronization signal transceiving apparatus having the structure described above will be explained in detail with reference to Figs. 3A and 3B.
  • the synchronization signal transmitting unit 210 outputs one byte ⁇ BB' signal in an ACSII (American Standard Code for Information Interchange) fashion as a preamble signal of the synchronization signal so as to report that the synchronization signal ⁇ AA' will be immediately transmitted after its preamble signal being transferred.
  • ACSII American Standard Code for Information Interchange
  • the time information generator 212 checks whether the synchronization signal is an even second synchronization signal or not, and transmits time information of 16 bytes in 20 msec after transferring the synchronization signal.
  • the synchronization signal transmitting unit 210 repeats the above transmission cycle in every second.
  • each of the synchronization signal receiving units 220 and 230 recognizes that the synchronization signal ⁇ AA' will be transmitted thereto in a moment, and, in a ready state, waits for the transmission of the synchronization signal.
  • each of the synchronization signal receiving units 220 and 230 receives the time information TOD of 16 bytes, transmits the time information TOD to the base stations in 9600 bps, and then waits for the preamble signal BB' of the synchronization signal .
  • a processor detects a time difference between a receiving time of the synchronization signal and an estimated receiving time of the synchronization signal (i.e., an estimated synchronization signal) to be provided to the base stations from the synchronization signal receiving units 220 and 230.
  • an estimated receiving time of the synchronization signal i.e., an estimated synchronization signal
  • the synchronization signal receiving units 220 and 230 employ the signal processor 222.
  • the signal processor 222 detects an average value of time differences, detected for a preset time, between a receiving time of the synchronization signal AA' and an estimated receiving time of the synchronization signal so that the tolerance due to a lower transmission rate can be reduced.
  • the processor can provide the base stations with a stabilized synchronization signal by controlling a generation time of the estimated synchronization signal by using the time difference obtained from the detection of the equivalent synchronization signal.
  • Fig. 4 there is provided a flow chart of showing a synchronization acquiring method for use in the communication system in accordance with the present invention.
  • step 401 the synchronization signal is generated in a period of about one second and the generated synchronization signal is modulated into a 1 byte signal AA' which is in turn transmitted to a communication medium.
  • step 402 the transmitting unit checks whether the synchronization signal is generated at an even or odd second. If the synchronization signal is produced at the even second, in step 403, the time information TOD of 16 bytes is transmitted after 20 msec being passed and then the transmission operation is stopped for a following 20 msec. At this time, the transmission of the 16 byte time information TOD is performed by using a protocol provided from a current base station to a mobile station.
  • step 402 if it is determined that the synchronization signal is generated at the odd second, in step 404, the transmission operation is stopped for 40 msec without transmitting the time information TOD.
  • step 405 the preamble signal BB' of the synchronization signal is transmitted to the communication medium.
  • the synchronization signal is produced in about 10 msec after the preamble signal is generated.
  • step 406 it is checked whether a signal transferred via the communication medium is the preamble signal BB' of the synchronization signal or not. If the received signal is the preamble signal of the synchronization signal, internal processors of the synchronization signal receiving units 220 and 230 wait for, in a ready state, the receiving of the synchronization signal ⁇ AA' for a predetermined time. If the synchronization signal ⁇ ⁇ A r is received, in step 407, it is detected a time difference between an estimated generation time of the synchronization signal and a receiving time of the synchronization signal ⁇ AA' , and then an equivalent synchronization signal of the synchronization signal is extracted based on the detected time difference. At this time, the detected time difference is accumulated for a preset time to thereby obtain an average value of the accumulated time differences and, in turn, the estimated generation time of the synchronization signal is changed in response to the average value.
  • the synchronization signal receiving units 220 and 230 receive the time information TOD of 16 bytes and transmit the received time information TOD to the base stations in step 408.
  • Fig. 5 there is provided a flow chart of describing a synchronization signal transmitting method in accordance with the present invention.
  • the synchronization signal transmitting unit 210 generates the synchronization signal in a period of about one second in step 501. Then, the generated synchronization signal is modulated into one byte signal AA' by the modem 213 and the modulated signal is transmitted to the communication medium in step 502.
  • an internal transmission processor of the synchronization signal transmitting unit 210 checks whether the synchronization signal is generated at an even or odd second. If the synchronization signal is produced at the even second, in step 504, this transmission operation for the synchronization signal is stopped for 20 msec. After then, the time information TOD of 16 bytes is transmitted in step 505 and, in turn, the transmission operation is stopped for 20 msec again in step 506. As a checking result of step 503, if it is determined that the synchronization signal is produced at the odd second, in step 507, the transmission operation is paused for 40 msec without transmitting the time information TOD. Like in steps 506 and 507, after the transmission operation is paused for a while, in step 508, the preamble signal BB' of the synchronization signal is provided to the communication medium.
  • the synchronization signal transmitting unit 210 checks whether an operation pausing instruction is inputted thereto from outside by using its internal processor. If the operation pausing instruction is not inputted, this procedure goes to step 501 and, if otherwise, the transmission of the synchronization signal is terminated.
  • the synchronization signal transmitting unit 210 repeats the above steps 501 to 508 in every second.
  • the synchronization signal transmitting unit 210 provides the synchronization signal and the preamble signal having 1 pps (pulse per second) in every second and the time information TOD in every two seconds.
  • FIG. 6 there is depicted a flow chart of illustrating a synchronization signal receiving method in accordance with the present invention.
  • step 601 the synchronization signal receiving units 220 and 230 check whether a signal received from the communication medium is the preamble signal BB' of the synchronization signal or not. If the received signal is the preamble signal of the synchronization signal, in step 602, the internal processors of the synchronization signal receiving units 220 and 230 wait for, in a ready state, the receiving of the synchronization signal ⁇ AA' for a predetermined time to thereby receive the synchronization signal AA' .
  • the synchronization signal ⁇ AA' is received in step 602
  • the equivalent synchronization signal of the synchronization signal is extracted based on the detected time difference.
  • the extracted equivalent synchronization signal represents a synchronization signal generated at the synchronization signal receiving units 220 and 230 at the same moment as the synchronization signal is produced at the synchronization signal transmitting unit 210.
  • the detected time difference is accumulated for about 20 msec to thereby obtain an average value of the accumulated time differences, and then the synchronization signal receiving units 220 and 230 estimate an exact generation time of the 1 pps synchronization signal at the synchronization signal transmitting unit 210 and provide the base stations 250 and 251 with the exact synchronization signal according to the estimation result in step 604.
  • the 1 pps synchronization signal provided to the base stations is used as a reference clock in the base stations, wherein the reference clock is utilized in generating a system clock in the base stations.
  • step 601 if it is decided that the received signal is not the preamble signal ⁇ BB' of the synchronization signal, the synchronization signal receiving units 220 and 230 receive the time information TOD of 16 bytes in step 605 and provide the received time information TOD to the base stations in step 606.
  • the synchronization signal receiving units 220 and 230 check whether an operation pausing instruction is transferred thereto from outside by using their internal processors. If the operation pausing instruction is not transferred, this procedure goes to step 601 and, if otherwise, the receiving operation of the synchronization signal is terminated.
  • the present invention can obtain a synchronization signal by using a certain communication medium without depending on GPS satellites provided by foreign countries when operating CDMA base stations so that it can provide the CDMA base stations with a stabilized synchronization signal by using the certain communication medium (e.g., Koreasat Mugunghwa, a transmission path and the like) located between a transmitter and a receiver. Furthermore, the present invention can accomplish a stabilization of communication by providing the stabilized synchronization signal required in a communication system only through the use of domestic satellites when it is impossible or difficult to use the foreign GPS satellites.
  • the certain communication medium e.g., Koreasat Mugunghwa, a transmission path and the like

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

Abstract

Apparatus and method for acquiring synchronization without a global positioning system (GPS). The apparatus for acquiring synchronization includes: a transmitter for generating and transmitting a synchronization signal and a preamble signal of the synchronization signal, and for transmitting time information based on a characteristic of the synchronization signal; and a receiver for receiving the synchronization signal, extracting an equivalent synchronization signal from the received synchronization signal and the time information, for estimating a generation time of the synchronization signal, and for outputting the equivalent synchronization signal at the estimated generation time of the synchronization signal.

Description

APPARATUS AND METHOD FOR ACQUIRING SYNCHRONIZATOIN
Technical Field
The present invention relates to an apparatus and method for acquiring synchronization in a communication system; particularly to a synchronization signal transceiving apparatus and its synchronization acquiring method, which operate a base station using a code division multiple access (CDMA) modulation technique.
Background Art
Referring to Fig. 1, there is shown a block diagram of a transceiving system for use in explaining a conventional synchronization signal acquiring method. The transceiving system comprises a plurality of base stations 110 and 111, at least one mobile station 120, a multiplicity of global positioning system (GPS) receivers 130 and 131, and a plurality of GPS satellites 140-143.
Hereinafter, the conventional synchronization signal acquiring method will be explained with reference to the transceiving system described in Fig. 1.
Domestic base stations 110 and 111 employing a CDMA modulation technique entirely have depended on foreign GPS satellites 140-143.
Terrestrial GPS receivers 130 and 131 can track a maximum 5 to 8 number of GPS satellites at the same time and receive very accurate synchronization and time information (TOD : Time of Day) from satellites, which the receivers are tracking.
After receiving synchronization signals from GPS satellites being tracked, the terrestrial GPS receivers 130 and 131 provide base stations with a synchronization signal having a lowest tolerance (i.e., typically less than 0.8 msec) .
The base stations transmit signals synchronized to the synchronization signal provided from the receivers and, thereafter, all of the base stations are synchronized to each other. As a result, it is possible for the mobile station 120 to accomplish a soft/softer handoff between base stations or sectors of base station.
However, in case of the conventional synchronization acquiring method, a domestic mobile communication service may not be effectively performed when there happen a failure in GPS satellite or a situation in which users have to pay for using the GPS satellites.
Disclosure of Invention
It is, therefore, a primary object of the present invention to provide a synchronization signal transceiving apparatus capable of acquiring synchronization through the use of a certain communication medium (e.g., Koreasat Mugunghwa) without depending on GPS satellites provided by foreign countries when operating CDMA base stations by transmitting a synchronization signal required to operate a CDMA base station from a transmitting end to a communication medium, allowing all of remote CDMA base stations to received the synchronization signal from the communication medium, and interpreting information for the synchronization signal to thereby estimate a synchronization signal approximating t'o the original synchronization signal, and synchronization acquiring method of the synchronization signal transceiving apparatus.
In accordance with one aspect of the present invention, there is provided an apparatus for acquiring synchronization in a communication system, including: a transmitter for generating, in a predetermined time period, a synchronization signal and a preamble signal of the synchronization signal, transmitting the generated signals to a communication medium, and providing the communication medium with time information in response to the synchronization signal; and a receiver for receiving the signals transmitted via the communication medium, extracting, based on the received signals, an equivalent synchronization signal which is generated at the same moment when the synchronization signal is produced at the transmitter, detecting original time information transferred from the transmitter based on the extracted equivalent synchronization signal, providing a base station with the time information, estimating a generation time of the synchronization signal by using synchronization signals transmitted for a preset time via the communication medium, and providing the base station with the synchronization signal according to the estimated result.
In accordance with another aspect of the present invention, there is provided a method for acquiring synchronization in a communication system, including the steps of: (a) generating a synchronization signal in a predetermined time period and transmitting the synchronization signal to a communication medium; (b) transmitting time information to the communication medium according to whether or not the synchronization signal is generated at an even second; (c) producing a preamble signal of the synchronization signal in a preset time after the step (b) is performed, and transmitting the preamble signal to the communication medium; and (d) at a synchronization signal receiving end, estimating a generation time of the synchronization signal transmitted through the communication medium by using the synchronization signal and the preamble signal received from the communication medium, and selectively providing the synchronization signal or the time information at the estimated generation time to a base station. Brief Description of Drawings
The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
Fig. 1 shows a block diagram of a transceiving apparatus for use in explaining a conventional synchronization signal acquiring method;
Fig. 2 illustrates a block diagram of a synchronization signal transceiving apparatus in a communication system in accordance with the present invention; Figs. 3A and 3B exemplify a synchronization signal transceiving method for use in the communication system in accordance with the present invention;
Fig. 4 provides a flow chart of showing a synchronization acquiring method for use in the communication system in accordance with the present invention;
Fig. 5 is a flow chart of describing a synchronization signal transmitting method in accordance with the present invention; and Fig. 6 depicts a flow chart of illustrating a synchronization signal receiving method in accordance with the present invention.
Best Mode for Carrying out the Invention
Hereinafter, with reference to the drawings, the preferred embodiment of the present invention will be explained in detail.
Referring to Fig.2, there is illustrated a block diagram of a synchronization signal transceiving apparatus in a communication system in accordance with a preferred embodiment of the present invention. The synchronization signal transceiving apparatus comprises a synchronization signal transmitting unit 210 for transmitting a synchronization signal, and synchronization signal receiving units 220 and 230 for receiving the synchronization signal which is outputted from the synchronization signal transmitting unit 210 and then transmitted via a communication medium such as a Koreasat Mugunghwa 240, extracting an equivalent synchronization signal corresponding to the received synchronization signal, and delivering the received synchronization signal to base stations 250 and 251.
Herein, since the synchronization signal receiving units 220 and 230 receive information transmitted via the communication medium, extract the equivalent synchronization signal based on the received information, and provide the synchronization signal to the base stations 250 and 251, a mobile station 260 can perform a soft/softer handoff in a base station which provides a communication service to the mobile station 260.
The synchronization signal transmitting unit 210 includes a synchronization signal generator 211 for producing the synchronization signal in a predetermined time period, a time information generator 212 for providing time information according to the synchronization signal transferred from the synchronization signal generator 211, and a modem 213 for modulating the synchronization signal and the time information supplied from the time information generator 212 and transmitting the modulated information.
When the synchronization signal is generated every second at the synchronization signal generator 211, the synchronization signal transmitting unit 210 modulates the synchronization signal and the time information by using the modem 213 and transmits the modulated information. At this time, the time information generator 212 checks whether or not the synchronization signal delivered thereto is generated at an even second. If it is determined that the synchronization signal is produced at the even second, the time information generator 212 transmits the synchronization signal and then outputs time information (i.e., year, month, day, hour, minute, second and the like) .
Each of the synchronization signal receiving units 220 and 230 includes a modem 221, a signal processor 222 and a time information detector 223. The modem 221 modulates a signal transmitted through the Koreasat Mugunghwa 240 that is the communication medium. The signal processor 222 receives the modulated signal provided from the modem 221, extracts, based on the received signal, the equivalent synchronization signal produced at the same time as the synchronization signal is generated at the synchronization signal transmitting unit 210 to thereby provide the base station 250 and 251 with the equivalent synchronization signal, estimates a generation time of the synchronization signal by using signals modulated by the modem 221 for a preset time, and then provides the base station 250 and 251 with a synchronization signal corresponding to the estimated generation time. The time information detector 223 receives the synchronization signal extracted by the signal processor 222, detects original time information transmitted from the synchronization signal transmitting unit 210 by using the received synchronization signal, and delivers the detected time information to the base station 250 and 251.
Referring to Figs. 3A and 3B, there are explained the operations of the synchronization signal transceiving apparatus and its synchronization acquiring method for use in the communication system in accordance with the present invention. Hereinafter, the operation of the synchronization signal transceiving apparatus having the structure described above will be explained in detail with reference to Figs. 3A and 3B.
Referring to Fig. 3A, the operation of the synchronization signal transmitting unit 210 will be explained. The synchronization signal transmitting unit 210 outputs one byte λBB' signal in an ACSII (American Standard Code for Information Interchange) fashion as a preamble signal of the synchronization signal so as to report that the synchronization signal λAA' will be immediately transmitted after its preamble signal being transferred.
Once the synchronization signal is fed thereto, the time information generator 212 checks whether the synchronization signal is an even second synchronization signal or not, and transmits time information of 16 bytes in 20 msec after transferring the synchronization signal.
That is, in case of the even second synchronization signal, after the time information is outputted, this transmission operation is stopped for about 20 msec and then the preamble signal BB' of the synchronization signal is transmitted again.
If the synchronization signal is not the even second synchronization signal, this transmission operation is stopped for about 40 msec and then the preamble signal ΛBB' of the synchronization signal is transmitted. Namely, the synchronization signal transmitting unit 210 repeats the above transmission cycle in every second.
Referring to Fig. 3B, the operations of the synchronization signal receiving units 220 and 230 will be explained. If the preamble signal λBB' of the synchronization signal is provided thereto, each of the synchronization signal receiving units 220 and 230 recognizes that the synchronization signal λAA' will be transmitted thereto in a moment, and, in a ready state, waits for the transmission of the synchronization signal. If the signal coupled thereto is not the preamble signal BB' of the synchronization signal, each of the synchronization signal receiving units 220 and 230 receives the time information TOD of 16 bytes, transmits the time information TOD to the base stations in 9600 bps, and then waits for the preamble signal BB' of the synchronization signal .
At the moment when the synchronization signal ,AA' is coupled thereto, a processor detects a time difference between a receiving time of the synchronization signal and an estimated receiving time of the synchronization signal (i.e., an estimated synchronization signal) to be provided to the base stations from the synchronization signal receiving units 220 and 230. At this time, since the synchronization signal is transmitted as serial data from the Koreasat Mugunghwa 240, a synchronization tolerance of the synchronization signal increases as a transmission rate of the data becomes lower. As a result, the tolerance can be maximally 1 board/sec. In order to overcome the above drawback, the synchronization signal receiving units 220 and 230 employ the signal processor 222. The signal processor 222 detects an average value of time differences, detected for a preset time, between a receiving time of the synchronization signal AA' and an estimated receiving time of the synchronization signal so that the tolerance due to a lower transmission rate can be reduced.
As described above, the processor can provide the base stations with a stabilized synchronization signal by controlling a generation time of the estimated synchronization signal by using the time difference obtained from the detection of the equivalent synchronization signal.
In Fig. 4, there is provided a flow chart of showing a synchronization acquiring method for use in the communication system in accordance with the present invention.
Referring to Fig. 4, in step 401, the synchronization signal is generated in a period of about one second and the generated synchronization signal is modulated into a 1 byte signal AA' which is in turn transmitted to a communication medium.
Then, in step 402, the transmitting unit checks whether the synchronization signal is generated at an even or odd second. If the synchronization signal is produced at the even second, in step 403, the time information TOD of 16 bytes is transmitted after 20 msec being passed and then the transmission operation is stopped for a following 20 msec. At this time, the transmission of the 16 byte time information TOD is performed by using a protocol provided from a current base station to a mobile station.
On the other hand, as a result of the checking process in step 402, if it is determined that the synchronization signal is generated at the odd second, in step 404, the transmission operation is stopped for 40 msec without transmitting the time information TOD.
Like in steps 403 and 404, after the transmission operation is stopped for a certain time, in step 405, the preamble signal BB' of the synchronization signal is transmitted to the communication medium. In accordance with the present invention, the synchronization signal is produced in about 10 msec after the preamble signal is generated.
After then, in step 406, it is checked whether a signal transferred via the communication medium is the preamble signal BB' of the synchronization signal or not. If the received signal is the preamble signal of the synchronization signal, internal processors of the synchronization signal receiving units 220 and 230 wait for, in a ready state, the receiving of the synchronization signal λAA' for a predetermined time. If the synchronization signal ΛΑAr is received, in step 407, it is detected a time difference between an estimated generation time of the synchronization signal and a receiving time of the synchronization signal λAA' , and then an equivalent synchronization signal of the synchronization signal is extracted based on the detected time difference. At this time, the detected time difference is accumulated for a preset time to thereby obtain an average value of the accumulated time differences and, in turn, the estimated generation time of the synchronization signal is changed in response to the average value.
As a checking result of step 406, if it is decided that the received signal is not the preamble signal ΛBB' of the synchronization signal, the synchronization signal receiving units 220 and 230 receive the time information TOD of 16 bytes and transmit the received time information TOD to the base stations in step 408.
In Fig. 5, there is provided a flow chart of describing a synchronization signal transmitting method in accordance with the present invention.
Referring to Fig. 5, the synchronization signal transmitting unit 210 generates the synchronization signal in a period of about one second in step 501. Then, the generated synchronization signal is modulated into one byte signal AA' by the modem 213 and the modulated signal is transmitted to the communication medium in step 502.
In step 503, an internal transmission processor of the synchronization signal transmitting unit 210 checks whether the synchronization signal is generated at an even or odd second. If the synchronization signal is produced at the even second, in step 504, this transmission operation for the synchronization signal is stopped for 20 msec. After then, the time information TOD of 16 bytes is transmitted in step 505 and, in turn, the transmission operation is stopped for 20 msec again in step 506. As a checking result of step 503, if it is determined that the synchronization signal is produced at the odd second, in step 507, the transmission operation is paused for 40 msec without transmitting the time information TOD. Like in steps 506 and 507, after the transmission operation is paused for a while, in step 508, the preamble signal BB' of the synchronization signal is provided to the communication medium.
As recursively performing the transmission operation as shown above, in step 509, the synchronization signal transmitting unit 210 checks whether an operation pausing instruction is inputted thereto from outside by using its internal processor. If the operation pausing instruction is not inputted, this procedure goes to step 501 and, if otherwise, the transmission of the synchronization signal is terminated.
Meanwhile, the synchronization signal transmitting unit 210 repeats the above steps 501 to 508 in every second.
Further, the synchronization signal transmitting unit 210 provides the synchronization signal and the preamble signal having 1 pps (pulse per second) in every second and the time information TOD in every two seconds.
Referring to Fig. 6, there is depicted a flow chart of illustrating a synchronization signal receiving method in accordance with the present invention.
In step 601, the synchronization signal receiving units 220 and 230 check whether a signal received from the communication medium is the preamble signal BB' of the synchronization signal or not. If the received signal is the preamble signal of the synchronization signal, in step 602, the internal processors of the synchronization signal receiving units 220 and 230 wait for, in a ready state, the receiving of the synchronization signal ΛAA' for a predetermined time to thereby receive the synchronization signal AA' . Then, if the synchronization signal λAA' is received in step 602, it is detected a time difference between the estimated generation time (i.e., the time when the synchronization signal ΛAA' is generated at the synchronization signal transmitting unit) and the receiving time of the synchronization signal XAA' , and then, in step 603, the equivalent synchronization signal of the synchronization signal is extracted based on the detected time difference. Herein, the extracted equivalent synchronization signal represents a synchronization signal generated at the synchronization signal receiving units 220 and 230 at the same moment as the synchronization signal is produced at the synchronization signal transmitting unit 210.
The detected time difference is accumulated for about 20 msec to thereby obtain an average value of the accumulated time differences, and then the synchronization signal receiving units 220 and 230 estimate an exact generation time of the 1 pps synchronization signal at the synchronization signal transmitting unit 210 and provide the base stations 250 and 251 with the exact synchronization signal according to the estimation result in step 604.
The 1 pps synchronization signal provided to the base stations is used as a reference clock in the base stations, wherein the reference clock is utilized in generating a system clock in the base stations.
In the meantime, one mobile station communicates with at least two base stations and each of the base stations is provided with 1 pps synchronization signals which are generated at the same moment. As a checking result of step 601, if it is decided that the received signal is not the preamble signal ΛBB' of the synchronization signal, the synchronization signal receiving units 220 and 230 receive the time information TOD of 16 bytes in step 605 and provide the received time information TOD to the base stations in step 606. As recursively performing the receiving operation as described above, in step 607, the synchronization signal receiving units 220 and 230 check whether an operation pausing instruction is transferred thereto from outside by using their internal processors. If the operation pausing instruction is not transferred, this procedure goes to step 601 and, if otherwise, the receiving operation of the synchronization signal is terminated.
As described above, the present invention can obtain a synchronization signal by using a certain communication medium without depending on GPS satellites provided by foreign countries when operating CDMA base stations so that it can provide the CDMA base stations with a stabilized synchronization signal by using the certain communication medium (e.g., Koreasat Mugunghwa, a transmission path and the like) located between a transmitter and a receiver. Furthermore, the present invention can accomplish a stabilization of communication by providing the stabilized synchronization signal required in a communication system only through the use of domestic satellites when it is impossible or difficult to use the foreign GPS satellites.
While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims .

Claims

1. An apparatus for acquiring synchronization in a communication system, comprising: a transmitting means for generating, in a predetermined time period, a synchronization signal and a preamble signal of the synchronization signal, transmitting the generated signals to a communication medium, and providing the communication medium with time information in response to the synchronization signal; and a receiving means for receiving the signals transmitted via the communication medium, extracting, based on the received signals, an equivalent synchronization signal which is generated at the same moment when the synchronization signal is produced at the transmitting means, detecting original time information transferred from the transmitting means based on the extracted equivalent synchronization signal, providing a base station with the time information, estimating a generation time of the synchronization signal by using synchronization signals transmitted for a preset time via the communication medium, and providing the base station with the synchronization signal according to the estimated result.
2. The apparatus as recited in claim 1, wherein the transmitting means includes: means for generating the synchronization signal in the predetermined time period; and means for providing the time information in response to the synchronization signal.
3. The apparatus as recited in claim 2, wherein the transmitting means further includes: means for modulating the synchronization signal and the time information, and providing the modulated synchronization signal and time information to the communication medium.
4. The apparatus as recited in claim 1, wherein the receiving means includes: a signal processing means for extracting the equivalent synchronization signal by using a time difference between a receiving time of the synchronization signal transmitted via the communication medium and an estimated generation time of the synchronization signal obtained by using the preamble signal, and outputting the equivalent synchronization signal at the estimated generation time; and a time information detecting means for receiving the equivalent synchronization signal, detecting the original time information based on the equivalent synchronization signal, and providing the detected time information to the base station.
5. The apparatus as recited in claim 4, wherein the receiving means further includes: means for demodulating the signals provided from the communication medium and transferring the demodulated signals to the signal processing means.
6. The apparatus as recited in claim 3, wherein the transmitting means generates the synchronization signal in every second and produces the time information in every even second.
7. The apparatus as recited in claim 4, wherein the signal processing means accumulates, for a given time, the time difference between the receiving time of the synchronization signal and the estimated generation time, computes an average value of the accumulated time differences, and changes the estimated generation time by using the average value.
8. The apparatus as recited in claim 7, wherein the given time is 20 sec.
9. A method for acquiring synchronization in a communication system, comprising the steps of:
(a) generating a synchronization signal in a predetermined time period and transmitting the synchronization signal to a communication medium;
(b) transmitting time information to the communication medium according to whether or not the synchronization signal is generated at an even second;
(c) producing a preamble signal of the synchronization signal in a preset time after the step (b) is performed, and transmitting the preamble signal to the communication medium; and
(d) at a synchronization signal receiving end, estimating a generation time of the synchronization signal transmitted through the communication medium by using the synchronization signal and the preamble signal received from the communication medium, and selectively providing the synchronization signal or the time information at the estimated generation time to a base station.
10. The method according to claim 9 further comprising the step of:
(e) modulating the synchronization signal and transmitting the modulated signal to the communication medium.
11. The method according to claim 9, wherein the step (b) includes the steps of: determining whether the synchronization signal is generated at an even or odd second; if it is determined that the synchronization signal is produced at the even second, stopping a transmission operation for a first preset time; transmitting the time information to the communication medium; after transmitting the time information, stopping the transmission operation for a second preset time; if it is determined that the synchronization signal is generated at the odd second, pausing the transmission operation for a third preset time; and transmitting the preamble signal to the communication medium.
12. The method according to claim 11, wherein the step (b) further includes the steps of: after transmitting the preamble signal, determining whether or not an operation pausing instruction is provided from outside; if the operation pausing instruction is inputted, terminating the transmission of the synchronization signal; and if the operation pausing instruction is not inputted, repeating the transmission operation from the step (a) .
13. The method according to claim 9, wherein the step (d) includes the steps of: determining whether a signal received from the communication medium is the preamble signal or not; if the received signal is the preamble signal, estimating the generation time of the synchronization signal, detecting a time difference between the estimated generation time and a receiving time of the synchronization signal, and extracting, based on the detected time difference, an equivalent synchronization signal which is generated at the same moment when the synchronization signal is produced at a transmitting end; accumulating the time difference for a fifth preset time, computing an average value of the accumulated time differences, estimating an exact generation time of the synchronization signal at the transmitting end, and providing the synchronization signal to the base station in response to the estimated exact generation time; if the received signal is not the preamble signal, receiving the time information from the communication medium; and providing the base station with the received time information.
14. The method according to claim 13, wherein the step (d) further includes: determining whether or not an operation pausing instruction is transferred from outside; if it is determined that the operation pausing instruction is inputted, terminating the receiving operation of the synchronization signal; and if it is decided that the operation pausing instruction is not coupled, repeating the receiving operation from the step of determining whether the received signal is the preamble signal or not.
PCT/KR2000/001214 2000-10-26 2000-10-26 Apparatus and method for acquiring synchronization WO2002035734A1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR950013060A (en) * 1993-10-15 1995-05-17 엘리 베이스 Broadcast frequency synchronization device and method
KR960027640A (en) * 1994-12-23 1996-07-22 양승택 Visual information transmission circuit of digital communication network

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR950013060A (en) * 1993-10-15 1995-05-17 엘리 베이스 Broadcast frequency synchronization device and method
KR960027640A (en) * 1994-12-23 1996-07-22 양승택 Visual information transmission circuit of digital communication network

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