Uplink Timing Maintenance Upon Time Alignment Timer Expiry

• US 20140086219A1
• Filed: 02/19/2013
• Published: 03/27/2014
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: Research In Motion Limited (Blackberry Limited)
• Inventors: Suzuki, Takashi, Cai, Zhijun, Earnshaw, Andrew Mark
• Granted Patent: US 9,167,547 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04W 56/0005 synchronizing of arrival of multiple uplinks
• CPC Class Codes: H04W 56/003 Arrangements to increase tolerance to errors in transmission or reception timing
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 56/0055 determining timing error of reception due to propagation delay

Abstract

Systems, apparatuses, and methods for uplink timing maintenance in wireless communications are provided. Certain aspects of the disclosure involve applying a timing advance command to adjust uplink transmission timing/resume uplink synchronization; and determining a metric. The metric can be used in determining whether to apply a timing advance command (TAC) to resume uplink resynchronization.

Claims

1. A method for controlling uplink transmission timing of a wireless communications network, the network comprising a base station and a User Equipment (UE), the method comprising:

applying a first timing advance command to adjust uplink transmission timing;

determining a time limit, the time limit identifying an amount of time elapsed, relative to an expiration of a time alignment timer (TAT), until an estimated uplink transmission error exceeds a timing error limit; and

determining whether to use a second timing advance command to resume uplink synchronization based on the determined time limit.

2. The method of claim 1 further comprising:

if the elapsed time since the first timing advance command being applied is within the time limit, using the second timing advance command to start TAT; and

if the elapsed time since the first timing advance command being applied exceeds the time limit, refraining from using the second timing advance command to resume uplink synchronization.

3. The method of claim 1, wherein the uplink transmission error is a timing difference between the uplink transmission timing and a reference timing, wherein the reference timing can be an amount of time prior to a downlink timing and the amount of time to keep transmission from the UE arriving within a processing or demodulation window of a base station.

4. The method of claim 3, wherein the amount of time includes an amount of time to compensate for UE mobility.

5. The method of claim 3, wherein a downlink timing comprises a time when a first detected path in time of a corresponding downlink frame is received by the user equipment.

6. The method of claim 1, further comprising:

estimating a speed of the user equipment;

determining a speed limit of the user equipment; and

determining whether to use the second timing advance command to resume uplink synchronization based on the determined speed limit and the estimated speed of the user equipment.

7. The method of claim 6, wherein the speed limit of the user equipment can be calculated based on the timing error limit value, the speed of light, whether the timing advance is adjusted by the user equipment or timing advance is adjusted when TAT is not running, and a resynchronization time, the resynchronization time is the time taken to resynchronize an unsynchronized user equipment.

8. The method of claim 7, wherein the resynchronization time may comprise

a detection time which is the time taken to detect that the user equipment is not uplink synchronized;

and

a scheduling time which is the time taken to schedule and transmit a timing advance command for re-establishing uplink synchronization.

9. The method of claim 7, wherein the scheduling time may further comprise a retransmission delay.

10. The method of claim 6, wherein the speed estimation can be done by the network based on number of cells UE has visited per unit of time and cell radius information.

11. The method of claim 6, wherein the user equipment can use its geo-positioning capability and/or inertia sensor or accelerometer to estimate the speed or a range of speed of the user equipment.

12. The method of claim 11, further comprising:

at the user equipment, sending the network a mobility status indicator; and

at the base station, determining how to apply the second timing advance command based on the mobility indicator.

13. The method of claim 12 further comprising the base station determining a frequency of sending a timing advance command (TAC) medium access control (MAC) control element (CE) based on the mobility status indicator of the user equipment.

14. The method of claim 12 further comprising the base station determining a value of a time alignment timer (TAT) based on the mobility status indicator of the user equipment.

15. The method of claim 1, wherein the time limit is calculated based on one or more of the timing error limit value, the speed of light, an estimated speed of the user equipment, or whether a stored timing advance is adjusted by the user equipment or where a timing advance is adjusted when TAT is not running.

16. The method of claim 15, further comprising identifying an error margin of the estimated speed of the user equipment;

and wherein the time limit is calculated further based on the error margin of the estimated speed of the user equipment.

17. The method of claim 15, further comprising:

using the second timing advance command to resume uplink synchronization if the estimated speed of the user equipment is less than the speed limit of the user equipment; and

not using the second timing advance command to resume uplink synchronization if the estimated speed of the user equipment is greater than the speed limit of the user equipment.

22. The method of claim 10, wherein the speed estimation can be done by the network based on the UE staying in the cell for a time period greater than a threshold time period.

18. A base station of a wireless communications network, for controlling uplink transmission timing, the base station being operable to:

apply a Timing Advance Command (TAC) Medium Access Control (MAC) Control Element (CE) to resume uplink synchronization; and

send an instruction if the UE receives TAC MAC CE when a Time Alignment Timer (TAT) is expired.

19. The base station of claim 18, wherein the instruction is included in broadcast or dedicated Radio Resource Control (RRC) signaling.

20. A method performed at a base station of a wireless communications network, for controlling uplink transmission timing, the method comprising:

applying a Timing Advance Command (TAC) Medium Access Control (MAC) Control Element (CE) to resume uplink synchronization; and

sending an instruction if the UE receives TAC MAC CE when a Time Alignment Timer (TAT) is expired.

21. The method of claim 20, wherein the instruction is included in broadcast or dedicated Radio Resource Control (RRC) signaling.