CN101505215B - Method and apparatus for time clock synchronization - Google Patents
Method and apparatus for time clock synchronization Download PDFInfo
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- CN101505215B CN101505215B CN2009101272055A CN200910127205A CN101505215B CN 101505215 B CN101505215 B CN 101505215B CN 2009101272055 A CN2009101272055 A CN 2009101272055A CN 200910127205 A CN200910127205 A CN 200910127205A CN 101505215 B CN101505215 B CN 101505215B
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Abstract
The invention discloses a method for clock synchronization. The method comprises the following steps that: a terminal receives and buffers a system clock from a mobile multimedia broadcast system; the terminal selects a time slot occupied by a service logical channel, calculates offset time of the selected time slot relative to the system clock, and accumulates the calculated offset time and the system clock to acquire a correction clock; and the terminal updates the lock clock by adopting the correction clock. The method calculates the offset time according to the time slot occupied by the service logical channel carrying a data frame, accumulates the offset time and system clock issued by the mobile multimedia broadcast system, updates the local clock of the terminal, improves the precision of the terminal clock, meets the service requirement, and is easy to be realized.
Description
Technical field
The present invention relates to the China mobile multi-media broadcasting technology field, relate in particular to a kind of method and device that carries out clock synchronization.
Background technology
In recent years, digital radio China mobile multi-media broadcasting technology and standard evolution are rapid, Ou Zhou DVB-H (Digital Video Broadcast Handheld for example, the reception of digital video broadcast-handheld formula), MediaFLO (the Media Forward Link Only of the U.S., the single forward link of medium) and the CMMB (China Mobile Multimedia Broadcast, China Mobile multimedia broadcasting) etc. of China.
Mobile multimedia broadcast system can provide video and audio service for mobile phone users, simultaneously also can provide the several data broadcasting service, as video segment file based on the file downloading mode, MP3 (MPEG Audio Layer 3, Motion Picture Experts Group's audio layer 3) song is based on the business of real time data stream, as transport information, and various business based on IP (Internet Protocol, Internet protocol).
In the service application of majority, need terminal to have comparatively accurately clock as the fiducial time of business data processing.Especially for real time data stream business, real-time data service and file downloading service etc.According to user's experience, the error that need make terminal clock and broadcast system clock could provide the sound that is satisfied in the main visual experience for the user less than 0.1 second.
Figure 1 shows that the logic channel and the time slot relation of mobile multimedia broadcast system, Mobile Multimedia Broadcasting normalized definition broadcast channel physical layer provides broadcast channel by physical layer logic channel (PLCH) for upper-layer service.The physical layer logic channel is divided into control logic channel (CLCH) and service logical channels (SLCH).
The control logic channel is used to carry the broadcast system control information, and service logical channels is used to carry broadcasting service.Physical layer has only a fixing control logic channel, and the 0th time slot that takies system sends.Service logical channels is by system configuration, and the number of service logical channels can be 1～39 in each physical layer bandwidth, and each service logical channels takies an integer time slot.
In the multiplex mode of mobile multimedia broadcast system, comprise system clock information in the control information that sends in the Frame on the control logic channel, Frame periodically sends to terminal.But, because, there is error in the terminal timing, other communication system and service application also may be changed terminal clock, and the length of Frame is 1 second, that is to say that mobile multimedia broadcast system upgrades once terminal clock at the most 1 second, therefore, only carry system clock information by the control logic channel, clock to terminal carries out synchronously, is difficult to satisfy the requirement that requires clocking error littler (for example less than 0.1 second) in the service application on precision, in fact, terminal clock has uncertainty 1 second error at interval, even may be 1 second.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of method and device that carries out clock synchronization, and the error that solves the existence of mobile multi-media broadcast terminal clock can't satisfy the problem of business need, reduces the error of terminal clock, improves its precision.
For solving the problems of the technologies described above, a kind of method of carrying out clock synchronization of the present invention comprises:
Terminal receives and the caching system clock from mobile multimedia broadcast system;
The time slot that terminal selects service logical channels to take calculates the shift time of selected time slot relative system clock, and the shift time that calculated and system clock are added up obtains position;
Terminal adopts position to upgrade local clock.
Further, terminal is calculated the concrete grammar of the shift time of selected time slot relative system clock and is: the number of time slots of skew between the time slot 0 of selected time slot and same Frame be multiply by slot length.
Further, one or more time slots that terminal selects service logical channels to take are respectively according to selected time slot calculation correction clock.
Further, when position when being a plurality of, adopt position to upgrade local clock according to sequencing.
Further, terminal adopts position to upgrade before the local clock, and position and local clock are compared, if error does not satisfy the clock accuracy requirement, then adopts position to upgrade local clock.
Further, a kind of device that carries out clock synchronization, this device comprises: receiver module and clock correction module, wherein:
Receiver module is used for receiving and the caching system clock from mobile multimedia broadcast system;
The clock correction module is used for from receiver module reading system clock, the time slot of selecting service logical channels to take, calculate the shift time of selected time slot relative system clock, the shift time that calculated and system clock are added up obtains position, adopts position to upgrade local clock.
Further, the clock correction module is calculated the concrete grammar of the shift time of selected time slot relative system clock and is: the number of time slots of skew between the time slot 0 of selected time slot and same Frame be multiply by slot length.
Further, one or more time slots that the clock correction module selects service logical channels to take are respectively according to selected time slot calculation correction clock.
Further, when position when being a plurality of, the clock correction module adopts position to upgrade local clock according to sequencing.
Further, the clock correction module adopts position to upgrade before the local clock, and position and local clock are compared, if error does not satisfy the clock accuracy requirement, then adopts position to upgrade local clock.
The present invention calculates shift time according to the shared time slot of the service logical channels of carrying Frame, the system clock that shift time and mobile multimedia broadcast system are issued adds up, local clock to terminal upgrades, improved the precision of terminal clock, satisfied business need, and be easy to realize.
Description of drawings
Fig. 1 is the logic channel of mobile multimedia broadcast system and the schematic diagram of time slot relation;
Fig. 2 carries out the flow chart of the method for clock synchronization for the present invention;
Fig. 3 carries out the Organization Chart of the device of clock synchronization for the present invention.
Embodiment
Consider that existing mobile multimedia broadcast system could be to the local clock of terminal synchronously once every a second, and service application requires the error of terminal clock in 0.1 second, only pass through the synchronous of mobile multimedia broadcast system, can't reach error requirements to terminal clock, therefore, the present invention calculates shift time by the time slot of the control logic channel occupancy of employing mobile multimedia broadcast system, the system clock that shift time and system are issued adds up and obtains position, when the terminal local clock does not reach required precision, adopt the more local clock of new terminal of position.
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described.
Figure 2 shows that the present invention carries out the method for clock synchronization, comprising:
Step 201: mobile multimedia broadcast system regularly sends Frame to terminal, and wherein, the control information that sends on the control logic channel in the Frame comprises system clock;
Mobile multimedia broadcast system regularly sends Frame to terminal, send control information by the control logic channel, corresponding network configuration information is provided in the network information table of control information, 40 bit fields that comprise tag system clock T0, wherein, preceding 16 bit representation MJD (simplification Julian date) date code; 24 of backs are by 4 BCD coding, the system clock that is accurate to second of totally 6 numerals.
Step 202: terminal is received in the control information of carrying in the Frame that sends on the control logic channel, adopts the system clock in the control information to upgrade local clock, and the caching system clock;
Step 203: the data that on service logical channels, send in the terminal receiving data frames, the time slot of selecting service logical channels to take calculates the shift time of the system clock that carries in the relative control information of selected time slot;
The service logical channels of carrying Frame can be one or more, and by the mobile multimedia broadcast system configuration, each service logical channels takies the integer time slot more than 1 or 1.Physical layer signal was 1 Frame in per 1 second, was divided into 40 time slots, and each slot length is 25ms.
For example, the current reception service logical channels of terminal n, service logical channels n takies time slot 38 and 39, the shift time of the system clock T0 of time slot 38 relative terminal buffers is that the number of time slots that is offset between the time slot 0 of time slot 38 and same data frames multiply by slot length 25ms, that is: 25ms * 38=950ms.
When service logical channels takies a plurality of time slot, the first time slot that can only select service logical channels to take calculates shift time, also can select a time slot to calculate shift time, or each time slot that service logical channels takies is all calculated shift time every one or more time slots.
Step 204: terminal is to the system clock of the shift time that calculated and the buffer memory acquisition position that adds up;
Terminal adds up shift time 950ms and system clock T0 and obtains position.
Step 205: terminal compares local clock and position, judges whether local clock satisfies required precision, if the terminal local clock does not satisfy the clock accuracy requirement, then, carries out next step; Otherwise, finish;
If the error between terminal local clock and the position then satisfied the clock accuracy requirement in 0.1 second; Otherwise, do not satisfy the clock accuracy requirement.
Step 206: terminal adopts position to upgrade local clock.
When a plurality of time slots of selecting service logical channels to take calculated shift time, for the position of relativity shift time, the sequencing that needs to press position upgraded local clock.
Terminal is a benchmark with the local clock after upgrading, and the data that send on the service logical channels that receives are handled.
Figure 3 shows that the present invention carries out the device of clock synchronization, this device comprises: receiver module and clock correction module, wherein:
Receiver module is used for receiving the control information that Frame that mobile multimedia broadcast system sends carries on the control logic channel, adopt the system clock in the control information to upgrade local clock, and the caching system clock; And the data that on service logical channels, send in the receiving data frames.
Correction module is used to the time slot of selecting service logical channels to take, calculates the shift time of the system clock that carries in the relative control information of selected time slot; To the system clock of the shift time that calculated and the buffer memory acquisition position that adds up; Local clock and position are compared,, then adopt position to upgrade local clock if the terminal local clock does not satisfy the clock accuracy requirement.
For example, the current reception service logical channels of receiver module n, service logical channels n takies time slot 38 and 39, the method that correction module calculates the shift time of time slot 38 relative system clock T0 is: the number of time slots of skew between the time slot 0 of time slot 38 and same data frames be multiply by slot length 25ms, that is: 25ms * 38=950ms, shift time 950ms and system clock T0 added up obtains position.
When service logical channels takies a plurality of time slot, the first time slot that can only select service logical channels to take calculates shift time, also can select a time slot to calculate shift time every one or more time slots, or each time slot that service logical channels takies all calculated shift time, and further calculate position.When a plurality of time slots that position selects service logical channels to take calculated shift time, for the position that obtains according to the relativity shift Time Calculation, the sequencing that needs to press position upgraded local clock.
It should be noted last that above embodiment is only unrestricted in order to technical scheme of the present invention to be described, the modification that those of ordinary skill in the art carries out technical scheme of the present invention or be equal to replacement all is encompassed in the middle of the claim scope of the present invention.
Claims (10)
1. method of carrying out clock synchronization comprises:
Terminal receives and the caching system clock from mobile multimedia broadcast system;
The time slot that terminal selects service logical channels to take calculates the shift time of the described relatively system clock of selected time slot, and the shift time that calculated and described system clock are added up obtains position; Wherein, described shift time multiply by slot length for the number of time slots of skew;
Terminal adopts described position to upgrade local clock.
2. the method for claim 1 is characterized in that, the concrete grammar that described terminal is calculated the shift time of the described relatively system clock of selected time slot is: the number of time slots of skew between the time slot 0 of selected time slot and same Frame be multiply by slot length.
3. method as claimed in claim 2 is characterized in that, one or more time slots that described terminal selects service logical channels to take are respectively according to selected time slot calculation correction clock.
4. the method for claim 1 is characterized in that, when described position when being a plurality of, adopts described position to upgrade local clock according to sequencing.
5. as claim 1 or 4 described methods, it is characterized in that described terminal adopts described position to upgrade before the local clock, and described position and local clock are compared, if error does not satisfy the clock accuracy requirement, then adopt described position to upgrade local clock.
6. a device that carries out clock synchronization is characterized in that, this device comprises: receiver module and clock correction module, wherein:
Described receiver module is used for receiving and the caching system clock from mobile multimedia broadcast system;
Described clock correction module is used for reading described system clock from described receiver module, the time slot of selecting service logical channels to take, calculate the shift time of the described relatively system clock of selected time slot, the shift time that calculated and described system clock added up obtains position, adopts described position to upgrade local clock; Wherein, described shift time multiply by slot length for the number of time slots of skew.
7. device as claimed in claim 6, it is characterized in that the concrete grammar that described clock correction module is calculated the shift time of the described relatively system clock of selected time slot is: the number of time slots of skew between the time slot 0 of selected time slot and same Frame be multiply by slot length.
8. device as claimed in claim 7 is characterized in that, one or more time slots that described clock correction module selects service logical channels to take are respectively according to selected time slot calculation correction clock.
9. device as claimed in claim 6 is characterized in that, when described position when being a plurality of, described clock correction module adopts described position to upgrade local clock according to sequencing.
10. as claim 6 or 9 described devices, it is characterized in that described clock correction module adopts described position to upgrade before the local clock, and described position and local clock are compared, if error does not satisfy the clock accuracy requirement, then adopt described position to upgrade local clock.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101272055A CN101505215B (en) | 2009-03-05 | 2009-03-05 | Method and apparatus for time clock synchronization |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2009101272055A CN101505215B (en) | 2009-03-05 | 2009-03-05 | Method and apparatus for time clock synchronization |
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| CN101505215A CN101505215A (en) | 2009-08-12 |
| CN101505215B true CN101505215B (en) | 2011-07-13 |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102098144A (en) * | 2011-01-26 | 2011-06-15 | 华为技术有限公司 | Updating method of clock skew as well as announcing method and device of clock skew information |
| JP5965223B2 (en) * | 2012-06-29 | 2016-08-03 | ルネサスエレクトロニクス株式会社 | Clock correction circuit and clock correction method |
| CN103475404B (en) * | 2013-09-26 | 2016-08-17 | 北京米波通信技术有限公司 | A kind of satellite communication signals receives system and method |
| CN113347706B (en) * | 2021-06-01 | 2023-05-16 | 四川中电昆辰科技有限公司 | System and method for determining position occurrence time of device to be positioned in positioning system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1960435A (en) * | 2006-08-25 | 2007-05-09 | 中兴通讯股份有限公司 | Method and system for synchronizing broadcast time of mobile multimedia |
| CN1988667A (en) * | 2006-12-07 | 2007-06-27 | 中兴通讯股份有限公司 | Clock synchronizing method in broadcast network |
| CN101202613A (en) * | 2006-12-11 | 2008-06-18 | 中兴通讯股份有限公司 | Terminal for clock synchronising |
| CN101202921A (en) * | 2006-12-11 | 2008-06-18 | 中兴通讯股份有限公司 | Clock synchronous system of moving multimedia network |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1960435A (en) * | 2006-08-25 | 2007-05-09 | 中兴通讯股份有限公司 | Method and system for synchronizing broadcast time of mobile multimedia |
| CN1988667A (en) * | 2006-12-07 | 2007-06-27 | 中兴通讯股份有限公司 | Clock synchronizing method in broadcast network |
| CN101202613A (en) * | 2006-12-11 | 2008-06-18 | 中兴通讯股份有限公司 | Terminal for clock synchronising |
| CN101202921A (en) * | 2006-12-11 | 2008-06-18 | 中兴通讯股份有限公司 | Clock synchronous system of moving multimedia network |
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Granted publication date: 20110713 Termination date: 20180305 |