Two-step uplink synchronization for pico/femtocell

• US 20110171949A1
• Filed: 01/07/2011
• Published: 07/14/2011
• Est. Priority Date: 01/08/2010
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Lin, Kuhn-Chang, Su, York Ted, Liao, Pei-Kai, Chen, Yih-Shen
• Granted Patent: US 8,855,044 B2
• Time in Patent Office: Days
• US Class Current: 455/422.1
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

A two-step uplink synchronization method is provided for uplink synchronization between a mobile station and a pico/femto base station that is deployed together with an overlay macro/micro base station. In a first step, the pico/femto BS encodes and broadcasts UL transmission timing advance offset information via a broadcast channel. The MS decodes the received UL transmission timing advance offset information and advances its uplink timing for uplink ranging or reference signal transmission based on the decoded offset value. In a second step, the MS and the pico/femto BS performs regular uplink synchronization and uplink access. In one example, the UL transmission timing advance offset information indicates a round-trip propagation time of radio signals between the pico/femto base station and the overlay macro/micro base station. By using the two-step uplink synchronization method, a unified synchronous ranging channel may be used for ranging and UL access in pico/femtocells with reduced interference.

Claims

1. A method comprising:

receiving uplink (UL) transmission timing advance offset information from a base station by a mobile station in a cellular communication system, wherein the mobile station is located within a cell coverage that is overlapped with a different cell coverage provided by another overlaying base station;

adjusting an UL transmission timing based on the received UL transmission timing advance offset information; and

performing UL synchronization and UL access with the base station.

2. The method of claim 1, wherein the UL transmission timing is advanced for ranging signal transmission via a ranging channel (RCH).

3. The method of claim 1, wherein the UL transmission timing is advanced for reference signal transmission via a random access channel (RACH).

4. The method of claim 1, wherein the UL transmission timing advance offset information indicates a round-trip propagation time of radio signals between the base station and the overlaying base station.

5. The method of claim 1, wherein the UL transmission timing advance offset information comprises an encoded number indicative of an UL transmission timing advance offset value.

6. The method of claim 1, wherein the mobile station decodes the UL transmission timing advance offset information broadcasted by the base station via a broadcast channel (BCH).

7. A mobile station, comprising:

a transceiver that receives uplink (UL) transmission timing advance offset information from a base station in a cellular communication system, wherein the mobile station is located within a cell coverage that is overlapped with a different cell coverage provided by another overlaying base station;

an information decoding module that decodes the UL transmission timing advance offset information and derives an UL transmission timing advance offset value for UL transmission timing adjustment; and

an UL access and timing adjustment module that performs UL synchronization and UL access with the base station.

8. The mobile station of claim 7, wherein the UL transmission timing for ranging signal transmission via a ranging channel (RCH) is advanced based on the offset value.

9. The mobile station of claim 7, wherein the UL transmission timing for reference signal transmission via a random access channel (RACH) is advanced based on the offset value.

10. The mobile station of claim 7, wherein the UL transmission timing advance offset information indicates a round-trip propagation time of radio signals between the base station and the overlaying base station.

11. The mobile station of claim 7, wherein the UL transmission timing advance offset information comprises an encoded number indicative of an UL transmission timing advance offset value.

12. The mobile station of claim 7, wherein the information decoding module decodes the UL transmission timing advance offset information broadcasted by the base station via a broadcast channel (BCH).

13. A method, comprising:

determining an uplink (UL) transmission timing advance offset value by a base station in a cellular communication system, wherein the base station has a different cell coverage overlapped with a cell coverage of an overlay base station;

encoding the UL transmission timing advance offset value into UL transmission timing advance offset information and broadcasting the information via a broadcast channel; and

detecting an uplink signal from a mobile station, wherein the uplink signal is transmitted with an adjusted transmission timing either based on the UL transmission timing advance offset information in an initial uplink transmission or based on an estimated timing advance from the base station in a subsequent uplink transmission.

14. The method of claim 13, wherein the base station adjusts UL transmission timing based on the UL transmission timing advance offset when the base station and the overlay base station operate either in the same frequency band or in nearby frequency bands.

15. The method of claim 13, wherein the base station either uses a predefined value for UL transmission timing or adjusts UL transmission timing based on the UL transmission timing advance offset when the base station and the overlay base station operate in separate frequency bands.

16. The method of claim 13, wherein the uplink signal is a ranging signal transmitted via a ranging channel (RCH).

17. The method of claim 13, wherein the uplink signal is a reference signal transmitted via a random access channel (RACH).

18. The method of claim 13, wherein the UL transmission timing advance offset value is equal to a round trip propagation time of radio signals between the base station and the overlay base station.

19. The method of claim 13, wherein the UL transmission timing advance offset information comprises an encoded number indicative of the UL transmission timing advance offset value.

20. A base station, comprising:

an information, encoding module that encodes an uplink (UL) transmission timing advance offset value into UL transmission timing advance offset information;

a transceiver that broadcasts the UL transmission timing advance offset information via a broadcast channel in a cellular communication system, wherein the base station has a different cell coverage overlapped with a cell coverage of an overlay base station; and

a signal detection and timing estimation module that detects an uplink signal from a mobile station and estimates a drift timing difference, wherein the uplink signal is transmitted with an adjusted transmission timing either based on the UL transmission timing advance offset information in an initial uplink transmission or based on an estimated timing advance from the base station in a subsequent uplink transmission.

21. The base station of claim 20, wherein the base station adjusts UL transmission timing based on the UL transmission timing advance offset when the base station and the overlay base station operate either in the same frequency band or in nearby frequency bands.

22. The base station of claim 20, wherein the base station either uses a predefined value for UL transmission timing or adjusts UL transmission timing based on the UL transmission timing advance offset when the base station and the overlay base station operate in separate frequency bands.

23. The base station of claim 20, wherein the uplink signal is a ranging signal transmitted via a ranging channel (RCH).

24. The base station of claim 20, wherein the uplink signal is a reference signal transmitted via a random access channel (RACH).

25. The base station of claim 20, wherein the UL transmission timing advance offset value is equal to a round trip propagation time of radio signals between the base station and the overlay base station.

26. The base station of claim 20, wherein the UL transmission timing advance offset information comprises an encoded number indicative of the UL transmission timing advance offset value.