WO2010115357A1

WO2010115357A1 - Method and system for clock correction of wireless base station based on internet protocol (ip) network

Info

Publication number: WO2010115357A1
Application number: PCT/CN2010/071024
Authority: WO
Inventors: 杨锋; 姚幸林; 周辉; 邰春玲
Original assignee: 中兴通讯股份有限公司
Priority date: 2009-04-09
Filing date: 2010-03-12
Publication date: 2010-10-14
Also published as: CN101860952B; CN101860952A

Abstract

A method for clock correction of wireless base station based on Internet Protocol (IP) network, the method comprises: the wireless base station obtains at least two groups of related correction data which represent clock synchronization; the wireless base station calculates correction frequency difference using the related correction data, and corrects the local clock according to the correction frequency difference. A system for clock correction of wireless base station based on IP network is also provided, and the system comprises: a correction data acquisition module (12) for obtaining at least two groups of related correction data which represent clock synchronization; a clock correction module (13) for calculating correction frequency difference using the related correction data and correcting the local clock according to the correction frequency difference. With the method and the system, more accurate clock is provided for a wireless base station in IP network.

Description

Method and system for correcting wireless base station clock based on IP network

The present invention relates to a clock synchronization correction technology for a wireless base station in the field of mobile communication, and more particularly to a method and system for correcting a wireless base station clock based on an Internet Protocol (IP) network. Background technique

Global System For Mobile Communication (GSM) is the most widely used communication standard in mobile communications. The radio access network of the GSM system is usually called a base station subsystem (BSS, Base Station Subsystem), and is composed of a base station controller (BSC) and a base transceiver station (BTS), and is connected to the mobile station through a radio interface to perform wireless signals. Send, receive and manage wireless resources.

Wireless base stations require accurate clock signals for a variety of applications. Generally, a wireless base station uses a temperature compensated crystal oscillator (TCXO, Temperature Compensated Crystal Oscillator) to generate a 26 MHz oscillation frequency as a local clock signal, but as time and temperature change, the 26 MHz oscillation frequency will have a relatively large change, thereby affecting Air interface wireless transmission quality, and bring interference to other base stations and affect mobile phone access.

For this reason, it is necessary to correct the frequency offset of the crystal oscillator, that is, to correct the clock of the radio base station. At present, for a traditional wireless access network system based on time division multiplexing (TDM) transmission mode, the BTS extracts a synchronous clock signal by means of an E1/T1 link of TDM, or a GPS device, to calibrate the oscillation of the local clock. Frequency, to ensure the quality of air interface wireless transmission, to solve the interference problem caused by frequency offset. However, in the face of IP-based networking, IP network networking is diverse and flexible, and IP networking has become mainstream. For the IP networking mode, the clock signal cannot be obtained through the E1 link, but the clock accuracy obtained only through the physical layer of the IP network cannot meet the requirements of the wireless communication device. Summary of the invention

In view of the above background, the present invention provides a method and system for correcting a radio base station clock based on an IP network to provide a more accurate clock for a radio base station in an IP network.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A method for correcting a wireless base station clock based on an IP network, the method comprising:

During the calibration data acquisition process, the wireless base station acquires at least two sets of related correction data indicating clock synchronization; in the clock correction process, the wireless base station calculates a corrected frequency difference by using the correlation correction data, and pairs the local clock according to the corrected frequency difference Make corrections.

The correlation correction data of each group includes a first timestamp, a second timestamp, a third timestamp, and a fourth timestamp;

The first timestamp is a time when the wireless base station sends a clock synchronization request to the clock synchronization server; the second timestamp is a time when the clock synchronization server receives the clock synchronization request; the third timestamp is a clock a time when the synchronization server sends a clock synchronization response to the wireless base station; the fourth timestamp is a time when the wireless base station receives the clock synchronization response;

among them, /. # is the correction frequency difference; ^ is the standard frequency; ^Δ ^ is the difference between the first time stamps corresponding to each of the two sets of the correlation correction data; ^Δ ^ is the corresponding corresponding to each of the two sets of the correlation correction data a difference between the two timestamps; ^Δ ^ is a difference between the third timestamps corresponding to each of the two sets of the correlation correction data;

Δ^ ⁴ is the difference between the fourth time stamps corresponding to each of the two sets of the correlation correction data.

Wherein, when the wireless base station performs correction by using multiple corrected frequency differences, the method further includes: filtering the bad values in the corrected frequency difference.

Wherein, when the wireless base station performs correction by using multiple corrected frequency differences, the method further includes: the wireless base station correcting the local clock by using an average of the plurality of corrected frequency differences.

The clock synchronization server is a network time protocol (ΝΤΡ) synchronization source, and the US electrical And the Institute of Electrical Engineers 1588 Protocol (PTP) synchronization source, or a custom synchronization source. In addition, this method can also be used as a clock synchronization source.

The invention also discloses a wireless base station clock correction system based on an IP network, the system comprising: a correction data acquisition module and a clock correction module; wherein

a calibration data acquisition module, configured to acquire, by the wireless base station, at least two sets of related correction data that characterize clock synchronization;

And a clock correction module, configured to calculate, by the wireless base station, a corrected frequency difference by using the correlation correction data, and correct the local clock according to the corrected frequency difference.

The correction data collection module is further configured to: when acquiring at least two sets of the correlation correction data, each set of the correlation correction data includes a first timestamp, a second timestamp, a third timestamp, and a fourth Timestamp

The clock correction module is further configured to: when the local clock is corrected according to the corrected frequency difference,

Wherein, the frequency difference is corrected; ^ is the standard frequency; ^Δ ^ is the difference between the first time stamps corresponding to each of the two sets of the correlation correction data; ^Δ ^ is corresponding to each of the two sets of the correlation correction data respectively a difference between the second time stamps; ^Δ ^ is a difference between the third time stamps corresponding to each of the two sets of the correlation correction data; ^ is a fourth time corresponding to each of the two sets of the correlation correction data The difference between the stamps.

The system further includes: a bad value filtering module, configured to filter a bad value in the corrected frequency difference when the wireless base station performs correction by using multiple corrected frequency differences.

The clock correction module is further configured to: when the wireless base station passes multiple correction frequencies When the difference is corrected, the radio base station corrects the local clock by the mean of the plurality of corrected frequency differences. The clock synchronization server is an NTP synchronization source, a PTP synchronization source, or a customized synchronization source. In addition, the system can be used as a clock synchronization source.

Compared with the prior art, the present invention has the following advantages:

The invention corrects the local clock of the wireless base station by collecting data such as the sending time of the clock synchronization request of the wireless base station, the time when the clock synchronization server receives the request, the time of sending the clock synchronization response, and the time when the wireless base station receives the response. This provides accurate clock timing. DRAWINGS

1 is a schematic view showing the structure of a system of an example of the present invention;

2 is a schematic flow chart of a calibration process of an example of the present invention;

3 is a schematic structural diagram of a system hardware of an example of the present invention;

4 is a flow chart of calibration data acquisition of an example of the present invention. detailed description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Figure 1 exemplarily depicts the system architecture of the present invention. FIG. 1 depicts only portions relevant to the present invention, and those skilled in the art will appreciate that the wireless base station has other functions and structures, but these are not within the scope of the present invention. The exemplary system shown in Figure 1 includes: a wireless base station at the client 1. A clock synchronization server 2 at the server. The radio base station 1 includes a local clock 11, a correction data acquisition module 12, and a clock correction module 13.

In Fig. 1, the radio base station 1 transmits a clock synchronization request 3 to the clock synchronization server 2 through the correction data acquisition module 12, and records the transmission time of the clock synchronization request 3 as the first time stamp T1. The first timestamp T1 can be obtained by using the local clock 11 of the radio base station 1, for example, a 26 压 voltage controlled crystal oscillator.

When the clock synchronization server 2 receives the clock synchronization request 3, it records the current time as Second timestamp T2. Then, when the clock synchronization server 2 transmits the clock synchronization response 4 to the radio base station 1, the current time is also recorded, that is, the transmission time of the clock synchronization response 4 is taken as the third time stamp Τ3. The clock synchronization response 4 sent by the clock synchronization server 2 to the radio base station 1 will contain a second time stamp Τ2 and a third time stamp Τ3. The acquisition of the second timestamp Τ2 and the third timestamp Τ3 may have different manners depending on the application scenario. For example, the clock synchronization server 2 may acquire the second time stamp Τ2 and the third time stamp Τ3 from the reference clock carried by itself, or may also be acquired by the coordinated receiving universal time (UTC) standard clock by the GPS receiving device.

When the radio base station 1 receives the clock synchronization response 4, the current time is recorded, that is, the reception time of the clock synchronization response 4 of the radio base station 1 is taken as the fourth time stamp Τ4. Similarly, the fourth timestamp Τ4 can be obtained by the local clock 11.

The calibration data acquisition module 11 of the radio base station 1 receives the correction data and hands it to the clock correction module 13 for correction processing. The correction data includes: a first timestamp T1, a second timestamp Τ2, a third timestamp Τ4, and a fourth timestamp Τ4.

The data collection process needs to be repeated in one synchronization. The data collection can be performed periodically by the timing mode of the timer. In this mode, the next data collection may have a certain time interval from the previous data collection. Or the event triggering mode in which the wireless base station receives the clock synchronization response causes the next data acquisition to start immediately following the end of the previous data collection. Figure 4 depicts the process of two data acquisitions. In Figure 4, the client is the wireless base station 1, the server is the clock synchronization server 2, and the data Τ10, Τ20, Τ30, Τ40 are the first timestamp data collected, data Tll T21, T31, T41 are the timestamp data collected for the second time, ul=T20-T10, Dl=T40-T30; u2=T21-Tll, D2=T41-T31. The following explains how to calculate the frequency difference using timestamp data.

1) Calculate according to the timestamp of the client and server

Δ Τ1 = T11 - T10

Δ Τ2 = Τ21 - Τ20 ΔΤ3 = T31 -T30

ΔΤ4 = Τ41 -T40

2) Calculated according to the transmission delay

ΔΤ2 = ΔΤ1 -ul+u2

ΔΤ3 = ΔΤ4- D2+D1

Δ Τ2+ Δ Τ3 = ΔΤΙ + AT4-ul +u2-D2+Dl

= ΔΤΙ + ΔΤ4 + (u2+ Dl)- (ul + D2)

In the example of the present invention, the FPGA count time is employed, and therefore, in the following derivation, the time data is expressed in the form of a count.

3) According to the count N = time T frequency F:

AD

—— -+—— - + +

Fc fc fc + f _off fc + f _off fc + f _off where ΔΝ^ ΔΝ ₂ , ΔΝ ₃ , ΔΝ ₄ , AD are ΔΤ1, ΔΤ2, ΔΤ3, Δ Τ4, and (u2+ Dl)- (ul + D2), respectively The form of the count is indicated.

Push:

Where = the standard frequency is 26MHz, which is the difference between the actual frequency and the standard frequency.

4) Considering the effects of network delay and jitter, in the formula

It can be regarded as the error caused by the network environment. When the value is less than 1Hz, it can be ignored. and also

(u2+ Dl)- (ul + D2) _Λ

― -X f _c < 1

That is to say, when ΔΛ^ +ΔΛ^ ³ , the network factor band can be ignored. The impact of coming. Then the corrected frequency difference can be obtained as

AN, + AN,

AN2+ AN3

The bias correction voltage, the crystal oscillator is frequency corrected under the control of the correction voltage. For data acquisition, the interval between two acquisitions, that is, the larger the timing interval of T11-T10, the smaller the introduction error. In addition, to improve measurement accuracy, multiple measurements can be taken and then averaged.

FIG. 2 exemplarily describes the calibration processing flow of the present invention, including the following steps: Step S201, the system is started.

Step S202: The calibration data collection module 12 of the radio base station 1 acquires and acquires data for correction and saves it by interacting with the data of the clock synchronization server 2. Thereafter, the process officially entered the correction process.

Step S203: The calibration process first needs to perform filtering algorithm analysis on the collected data to filter the bad values. For the analysis of the filtering algorithm, it can be performed by the bad value filtering module in the wireless base station 1, and the bad value filtering module is not indicated in the drawing. Step S204, according to the foregoing frequency difference calculation process,

, to determine whether it meets the network quality threshold requirements. After judging that the data meets the network quality threshold requirement, the process will proceed to step S205, otherwise, the process jumps to step

Step S209.

Step S205: The data that meets the network quality threshold requirement is saved to a reasonable data area. Through the screening of network quality threshold requirements, it is possible to filter out data whose accuracy is greatly affected by factors such as network jitter and delay, and to save more reasonable data.

Step S206, when the amount of reasonable data saved in the reasonable data area has not reached the predetermined number When the value is up, the process will return to step S202 to continue the above process of data collection, filtering, network quality threshold requirement judgment, etc., once the reasonable data amount in the reasonable data area reaches a predetermined value, usually set to 10, the process will The process proceeds to step S207.

Step S207: using a reasonable data of a predetermined data amount as a correction reference, using a frequency offset calculation algorithm, calculating a corrected frequency difference, and converting the corrected frequency difference into a voltage control voltage value to the wireless base station by using a D/A conversion algorithm The 26M voltage controlled crystal oscillator of 1 performs correction control to realize frequency offset correction of the radio base station 1.

Step S208: When the frequency offset correction is completed, all data areas are cleared.

In step S209, the data that does not meet the network quality threshold requirement will not be saved and will be cleared after the end of the synchronization.

Fig. 3 exemplarily describes the hardware configuration of the radio base station 1 of the present invention. It should be understood that Figure 3 only depicts portions of the invention that are relevant to the present invention, and that other configurations that the wireless base station should have are not within the scope of the description of Figure 3. Meanwhile, FIG. 3 is also merely an example of the present invention, and does not limit the necessity of adopting the hardware structure shown in FIG. 3 to implement the present invention. In Figure 3, the main components included in the wireless base station 1 and their functions are:

Microprocessor chip (CPU): used for the implementation of the IP protocol stack and the functional control of each module of the system. Programmable Logic Array (FPGA): Used to count the output signal of the voltage controlled oscillator; 26M voltage controlled oscillator: Voltage controlled crystal oscillator, less affected by temperature drift and time drift; A/D subject to CPU control High-precision conversion chip for outputting voltage control values.

After the system starts to complete the hardware circuit self-test, the CPU activates the FPGA running program to complete the initialization of each hardware module parameter. The FPGA counts the 26M crystal oscillator output oscillation signal and converts it into a 64-bit format. The unit assumes that it is 1/26000000S. It periodically sends a time synchronization message to the clock synchronization server that provides the IP clock synchronization source. The protocol can use the network time protocol (NTP, Network Time Protocol). Or IEEE1588 protocol (PTP), after collecting a certain amount of data, you can obtain optimal multi-group data according to statistical methods, such as removing the maximum and minimum data of the offset value. After averaging these multiple sets of data, calculate the deviation of the FPGA count for a certain period of time, convert it to voltage voltage control value, and calibrate the 26M crystal oscillator signal. Among them, IEEE is the American Institute of Electrical and Electronics Engineers.

The technical effects of the present invention are as follows:

Targeted: Resolved the problem of clock and frequency synchronization in the current IP networking environment. Flexible networking: The present invention can be fully integrated into the base station software; and the same device can be used as a client for frequency offset correction, and can be used as a calibration synchronization source for other clients.

Low implementation cost: The present invention can be implemented entirely in software without the need for other external devices. High precision: By using a stable clock synchronization source as the clock synchronization server, filtering out the bad values that are greatly affected by network jitter, and using the data after the Xuexuan calculation to calculate the voltage control voltage value, the accuracy of O.lppm in the internet network environment can be obtained. O.Olppm precision clock under LAN.

The above is a further detailed description of the present invention in connection with the specific preferred embodiments, but this is only an example for the sake of understanding, and the specific implementation of the present invention should not be construed as being limited to the description. It is to be understood by those skilled in the art that various changes and substitutions may be made without departing from the spirit and scope of the invention.

Claims

Claim

The wireless base station acquires at least two sets of correlation correction data indicative of clock synchronization; the wireless base station calculates a corrected frequency difference using the correlation correction data, and corrects the local clock based on the corrected frequency difference.

2. The method according to claim 1, wherein each set of the correlation correction data comprises a first timestamp, a second timestamp, a third timestamp, and a fourth timestamp;

The first timestamp is a time when the wireless base station sends a clock synchronization request to the clock synchronization server; the second timestamp is a time when the clock synchronization server receives the clock synchronization request; the third timestamp is a clock And a time when the synchronization server sends a clock synchronization response to the wireless base station; the fourth timestamp is a time when the wireless base station receives the clock synchronization response; and the corrected frequency difference is calculated by / _£ ; wherein, /. _#为校正频

AN ₂ between each of said second time stamp is associated correction data sets corresponding to each; difference; standard frequency; ΔΛ ^ for each of the two sets of correction data related to a difference between a first time stamp corresponding to each difference; aN ₃ as the difference between the two sets of each of the third timestamp associated correction data respectively corresponding to; aN ₄ between the fourth time stamp for each of said two sets of correction data respectively corresponding to the relevant difference value.

3. The method according to claim 2, wherein when the wireless base station performs correction by using a plurality of corrected frequency differences, the method further comprises: filtering the bad values in the corrected frequency difference.

The method according to claim 2, wherein when the wireless base station performs correction by using a plurality of corrected frequency differences, the method further comprises: the wireless base station correcting the local clock by using the average of the plurality of corrected frequency differences.

The method according to any one of claims 2 to 4, characterized in that said clock synchronization The server is a Network Time Protocol (NTP) synchronization source, the Institute of Electrical and Electronics Engineers 1588 Protocol (PTP) synchronization source, or a custom synchronization source.

A wireless base station clock correction system based on an IP network, the system comprising: a correction data acquisition module and a clock correction module; wherein

And a calibration data acquisition module, configured to acquire at least two sets of related correction data for characterizing clock synchronization; a clock correction module, configured to calculate a corrected frequency difference by using the correlation correction data, and correct the local clock according to the corrected frequency difference.

The system according to claim 6, wherein the correction data acquisition module is further configured to: when acquiring at least two sets of the correlation correction data, each set of the correlation correction data includes a first time stamp, a second timestamp, a third timestamp, and a fourth timestamp;

The clock correction module is further configured to: when the local clock is corrected according to the corrected frequency difference, calculate the corrected frequency difference by using X /:; _Ff is corrected

Frequency frequency rate difference;; //:: is the standard frequency of the standard frequency;; ΔΔΛΛ^^ is the correction of the positive data of the relevant correlation corrections for each of the two groups of two groups The value of the difference between the first and first time stamps; AANN ₂₂ is the correct correlation data for each of the two groups of two groups. The value of the difference between the second and second time stamps; AANN ₃₃ is the correction of the positive data for each of the two groups of the two groups. Corresponding to the value of the difference between the third and third time stamps; AANN ₄₄ is the correction of the positive data for each of the two groups of two The value of the difference between the time stamps of the fourth and fourth time corresponding to the corresponding ones. .

88. The system according to the claim of claim 77, the special feature of which is that the system system further includes:: bad value Passing the filter module block for correcting the correction when the step of correcting the positive frequency frequency difference is performed by the plurality of wireless base station stations The bad value in the difference of the positive frequency frequency rate is filtered through the filter. .

99. The system according to the claim of claim 77, wherein the characteristic system is characterized in that: the clock clock correction correcting module module, Enter One step is for correcting the local clock by the mean of the plurality of corrected frequency differences when the wireless base station corrects by the plurality of corrected frequency differences.

The system according to any one of claims 7 to 9, wherein the clock synchronization server is an NTP synchronization source, a PTP synchronization source, or a customized synchronization source.