Base station synchronization

• US 20060034407A1
• Filed: 10/25/2005
• Published: 02/16/2006
• Est. Priority Date: 04/07/2000
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Zeira, Eldad, Dick, Stephen G.
• Granted Patent: US 7,379,518 B2
• Time in Patent Office: Days
• US Class Current: 375/356
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04B 7/2687 Inter base stations synchronisation
• CPC Class Codes: H04B 7/269 Master/slave synchronisation
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04B 7/2696 Over the air autonomous synchronisation, e.g. by monitoring network activity H04B7/2693 takes precedence
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 56/0065 using measurement of signal travel time
• CPC Class Codes: H04W 56/0075 based on arrival time vs. expected arrival time

Abstract

In a radio network controller (RNC), a covariant matrix and a database are updated. The RNC then detects that a first base station'"'"'s time-error-variance exceeds a predetermined threshold. In response, the RNC signals to a user-equipment (UE) to measure a time difference of arrival (TDOA) between signals transmitted from the first base station and a reference base station. The UE measures the requested TDOA between the designated base stations and reports the measurement results back to the RNC. The RNC then compares the measured TDOA with a TDOA value stored in the database. Based on the comparison, the RNC signals to the first base station to adjust its time base.

Claims

1. A method, for use in a radio network controller (RNC), of maintaining base stations synchronized in a wireless communication system, said wireless communication system comprising a node B comprising a plurality of base stations, an RNC, and at least one user equipment (UE), the method comprising:

updating a covariant matrix and a database;

detecting that a time error variance of a first base station exceeds a predetermined threshold;

signaling to a UE to measure a time difference of arrival (TDOA) between signals transmitted from the first base station and a reference base station;

measuring and reporting the TDOA measurement;

comparing the measured TDOA value with a value stored in the database; and

transmitting a message to the first base station to adjust its time base based on said comparison.

2. The method of claim 1, wherein the covariant matrix maintains a state estimate for each of the plurality of base stations, said state estimates including a time error of each base station relative to a reference, a rate of change of each time error, and a transmission delay between base station pairs.

3. The method of claim 2, wherein the database maintains previously received TDOA measurement values, and a time reference and time rate of change of each of the plurality of base stations.

4. The method of claim 3, further comprising determining whether a difference between the measured TDOA value and a TDOA value stored in the database exceeds a predetermined TDOA threshold;

and transmitting an adjustment message to the first base station if said difference exceeds said predetermined TDOA threshold.

5. The method of claim 4, further comprising:

adjusting a time base at the first base station according to the transmitted adjustment message;

reporting said adjustment to an RNC; and

updating the database and covariant matrix according to said adjustment.

6. The method of clam 5, wherein the reference base station is a master base station in a node B, and wherein the first base station is slaved to said master base station.

7. An RNC configured to maintain base stations synchronized, wherein said base stations are within a node B, the RNC comprising:

a covariant matrix configured to maintain a state estimate of each of a plurality of base stations;

a database configured to maintain received TDOA measurement values;

a message generator configured to generate and transmit measurement-request messages;

a measurement receive device configured to receive and process received TDOA measurement values; and

a synchronization controller configured to compute a time of transmission of each of the base stations and filter gains based on received TDOA measurement values.

8. The RNC of claim 7, wherein said state estimates include a time error of each base station relative to a reference, a rate of change of each time error, and a transmission delay between base station pairs.

9. The RNC of claim 8, wherein the synchronization controller is further configured to determine whether a difference between the received TDOA value and a TDOA value stored in the database exceeds a predetermined threshold.

10. The RNC of claim 9, wherein the message generator is further configured to generate and transmit adjustment messages according to a determined difference between the received TDOA value and the stored TDOA value.

11. The RNC of claim 10, wherein the measurement receive device is further configured to receive and process reporting messages responsive to transmitted adjustment messages.

12. The RNC of claim 11, wherein the synchronization controller is further configured to update the state estimates in the covariance matrix and update the database with received TDOA values.