Method for performing frequency synchronization of a base station and a network part
View Patent ↗The invention relates to a method for performing frequency synchronization of a base station, and to a network part. In the method, the following operations are performed: maintaining a reference clock in a network element of the cellular radio network; generating a time stamp signal in the reference clock; transferring the time stamp signal from the network element to the base station over an asynchronous data transmission connection; calculating on the basis of the transferred time stamp signal how much the time by the local clock at the base station deviates from the time by the reference clock; generating a speed correction factor for the local clock on the basis of at least one calculated deviation; correcting the running of the local clock with the speed correction factor; and generating the frequencies needed at the base station by using the local clock corrected with the speed correction factor.
1. A base station in a cellular radio network comprising:
a local clock;
means for receiving a time stamp signal sent over an asynchronous data transmission connection and generated by a reference clock of a network element connected to the base station by an asynchronous connection;
means for calculating how much time measured by the local clock at the base station deviates from time measured by the reference clock based on the received time stamp signal;
means for generating a speed correction factor for the local clock based on at least one calculated deviation;
means for correcting operation of the local clock using the speed correction factor, and
a frequency synthesizer for generating frequencies needed at the base station by using the local clock corrected with the speed correction factor.
2. The base station of claim 1 , wherein the speed correction factor indicates when a supply voltage of the local clock changes.
3. The base station of claim 2 , wherein the speed correction factor compensates for changes that gradually take place in characteristics of the local clock.
4. The base station of claim 3 , wherein the speed correction factor is adjusted more than once a year.
5. The base station of claim 1 , wherein the base station further comprises means for calculating deviation in transmission delay for the time stamp signal sent over the asynchronous data transmission connection, for comparing the deviation with a predetermined limit, and for concluding that accuracy of the local clock does not meet a required level if the deviation exceeds the predetermined limit.
6. A method for performing frequency synchronization of a base station in a cellular radio network, the method comprising:
maintaining a local clock;
receiving a time stamp signal at the base station, the time stamp signal having been generated by a reference clock of a network element connected to the base station over an asynchronous data transmission connection;
calculating how much time measured by the local clock at the base station deviates from time measured by the reference clock;
generating a speed correction factor for the local clock based on at least one calculated deviation;
correcting operation of the local clock with the speed correction factor; and
generating frequencies needed at the base station using the local clock corrected with the speed correction factor.
7. The method of claim 6 , wherein the speed correction factor indicates when a supply voltage of the local clock at the base station changes.
8. The method of claim 7 , wherein the speed correction factor compensates for changes that gradually take place in the characteristics of the local clock.
9. The method of claim 8 , wherein the correction is performed more than once a year.
10. The method of claim 6 , further comprising:
calculating the deviation in the transmission delay for the time stamp signal sent over the asynchronous data transmission connection;
comparing the deviation with a predetermined limit, and
if the deviation exceeds the predetermined limit, concluding that the accuracy of the local clock at the base station does not meet a required level.
11. An article of manufacture for performing frequency synchronization of a bases station in a cellular radio network, the article of manufacture comprising a machine readable medium containing one or more programs which when executed implement the steps of:
maintaining a local clock;
receiving a time stamp signal at the base station, the time stamp signal having been generated by a reference clock of a network element connected to the base station over an asynchronous data transmission connection;
calculating how much time measured by the local clock at the base station deviates from time measured by the reference clock;
generating a speed correction factor for the local clock based on at least one calculated deviation;
correcting operation of the local clock with the speed correction factor; and
generating frequencies needed at the base station using the local clock corrected with the speed correction factor.
12. The article of manufacture of claim 11 , wherein the speed correction factor indicates when a supply voltage of the local clock at the base station changes.
13. The article of manufacture of claim 12 , wherein the speed correction factor compensates for changes that gradually take place in the characteristics of the local clock.
14. The article of manufacture of claim 13 , wherein the correction is performed more than once a year.
15. The article of manufacture of claim 11 , wherein the steps further comprise:
calculating the deviation in the transmission delay for the time stamp signal sent over the asynchronous data transmission connection;
comparing the deviation with a predetermined limit, and
if the deviation exceeds the predetermined limit, concluding that the accuracy of the local clock at the base station does not meet a required level.