Method of synchronizing with an uplink channel and a method of determining a propagation delay in a wireless communications system

• US 20070147337A1
• Filed: 12/28/2005
• Published: 06/28/2007
• Est. Priority Date: 12/28/2005
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Bosch, Peter, Samuel, Louis, Farag, Emad, Mullender, Sape, Nathues, Alexander
• Granted Patent: US 8,089,938 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2681 Synchronisation of a mobile station with one base station
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 56/009 Closed loop measurements

Abstract

A method of synchronizing with an uplink channel and a method of determining a propagation delay in a wireless communications system are provided. In the example method of synchronizing, a propagation delay between a target base station and a mobile station is calculated. Then, the calculated propagation delay is sent to the target base station. In the example method of determining a propagation delay, a first signal is received indicating a first measured chip offset between a downlink channel of a serving base station and a pilot signal of the target base station. A second signal indicating a second measured chip offset between an uplink channel of the mobile station and a pilot signal of the target base station is then received. A propagation delay between the target base station and the mobile station is calculated based at least in part on the first and second measured chip offsets.

Claims

1. A method of synchronizing a target base station with a mobile station in a wireless communications system, comprising:

calculating a propagation delay between the target base station and the mobile station; and

sending the calculated propagation delay to the target base station.

2. The method of claim 1, wherein the calculating step calculates the calculated propagation delay based on (i) a first chip offset between a downlink channel and a pilot channel of the target base station and (ii) a second chip offset between an uplink channel of a mobile and the pilot channel of the target base station.

3. The method of claim 2, wherein the calculating step calculates the calculated propagation delay by subtracting the second chip offset and a constant value from the first chip offset and dividing the subtraction result by two.

4. The method of claim 2, wherein the constant value is a set amount of time between a receipt of a downlink transmission and a start of an uplink transmission.

5. The method of claim 2, wherein the first chip offset is received at a radio network controller (RNC) from the mobile station.

6. The method of claim 2, wherein the second chip offset is received at a radio network controller (RNC) from the target base station.

7. The method of claim 1, wherein the sending step is performed before communication between a serving base station and the mobile station terminates, the serving base station currently handling communication with the mobile station.

8. The method of claim 1, wherein the calculating and sending steps are performed in response to the target base station having a greater connection strength with the mobile station than a current serving base station.

9. The method of claim 1, wherein the calculating and sending steps are performed in support of a hard handoff of the mobile station from the serving base station to the target base station.

10. The method of claim 1, wherein the wireless communications system operates in accordance with Universal Mobile Telecommunications System (UMTS).

11. A method of synchronizing a target base station with a mobile station in a wireless communications system, comprising:

receiving a signal indicating a propagation delay between the target base station and the mobile station; and

synchronizing with an uplink channel received from the mobile station based on the indicated propagation delay.

12. The method of claim 11, further comprising:

sending a signal indicating a chip offset between an uplink channel of a mobile and a pilot channel of the target base station, the received signal indicating the propagation delay based at least in part on the sent signal.

13. The method of claim 11, wherein the receiving step is performed before communication between a serving base station and the mobile station terminates, the serving base station currently handling communication with the mobile station.

14. The method of claim 11, wherein the synchronizing step includes:

determining an expected arrival time of a next transmission time interval (TTI) based on the propagation delay; and

searching for uplink transmissions in a given proximity of the expected arrival time.

15. The method of claim 14, wherein the given proximity is determined based on an expectation of accuracy for the propagation delay.

16. The method of claim 14, wherein the given proximity accounts for drift in an actual propagation delay.

17. A method of calculating a propagation delay between a target base station and a mobile station in a wireless communications system, comprising:

first receiving a first signal indicating a first measured chip offset between a downlink channel of a serving base station and a pilot signal of the target base station;

second receiving a second signal indicating a second measured chip offset between an uplink channel of a the mobile station and a pilot signal of the target base station; and

calculating the propagation delay between the target base station and the mobile station based at least in part on the first and second measured chip offsets.

18. The method of claim 17, wherein the calculating step calculates the calculated propagation delay by subtracting the second measured chip offset and a constant value from the first measured chip offset and dividing the subtraction result by two.

19. The method of claim 18, wherein the first signal is received from the mobile station and the second signal is received from the target base station.

20. The method of claim 18, wherein the calculating step is performed at a radio network controller (RNC).

21. The method of claim 18, wherein the constant value is a set amount of time between a receipt of a downlink transmission and a start of an uplink transmission.