ANCHOR CARRIER SELECTION IN MULTI-CARRIER WIRELESS NETWORK

• US 20110142009A1
• Filed: 09/03/2008
• Published: 06/16/2011
• Est. Priority Date: 03/25/2008
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Kamuf, Matthias, Parkvall, Stefan
• Granted Patent: US 8,699,467 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Mechanism to receive control signals transmitted from a base station (210, 510, 910) to the user equipment (220, 520, 920) in a manner that minimizes power consumption on the user equipment (220, 520, 920) while still maintaining some acceptable level of performance is described. The user equipment (220, 520, 920) periodically measures the signal quality of component carriers used by the base station (210, 510, 910) and requests control signaling (anchor) carrier reselection. Either a single component carrier can be chosen if the single carrier has sufficient quality or multiple component carriers can be selected when the quality of the single quality is low. The anchor carrier reselection may also be triggered to manage the system as a whole. For fast moving user equipments (220, 520, 920), anchor carrier hopping pattern can be provided to increase robustness and reduce reselection signaling overhead.

Claims

1. A method for operating a user equipment (220, 520, 920) of a wireless network (200, 500, 900), comprising:

making (A330, A630) a determination as to whether an anchor carrier set should be changed, wherein the anchor carrier set includes one or more anchor carriers used by the user equipment (220, 520, 920) to receive control signals transmitted from a base station (210, 510, 910); and

making (A340, A640) a request to the base station (210, 510, 910) to change the anchor carrier set when it is determined that the anchor carrier set should be changed.

2. The method of claim 1,

wherein the user equipment (220, 520, 920) is capable of communicating with the base station (210, 510, 910) over a plurality of carriers with each carrier being associated with a bandwidth, and

wherein there is at least one gap in a frequency spectrum represented by the plurality of carriers.

3. The method of claim 1,

wherein it is determined that the anchor carrier set should be changed when a reliability of a first carrier is greater than a reliability of a second carrier from a perspective of the user equipment (220, 520, 920), and

wherein the anchor carrier set includes the second carrier but does not include the first carrier.

4. The method of claim 3, wherein the first carrier is determined to be more reliable than the second carrier when any one or more of the following is true:

a signal-to-interference ratio (SIR) of the first carrier is higher than a SIR of the second carrier,

a reference signal received power (RSRP) of the first carrier is higher than a RSRP of the second carrier,

a data transmission rate of the first carrier is greater than a data transmission rate of the second carrier,

an error rate of the first carrier is lower than an error rate of the second carrier, and

a repeat request rate of the first carrier is lower than a repeat request rate of the second carrier.

5. The method of claim 3, wherein the act (A340, A640) of making the request to the base station (210, 510, 910) to change the anchor carrier set comprises:

making (A410, A710) a determination as to whether the first carrier meets a predetermined minimum reliability threshold when it is determined that the anchor carrier set should be changed; and

making (A420, A720) a request to the base station (210, 510, 910) to include only the first carrier in the anchor carrier set when it is determined that the first carrier meets the predetermined minimum reliability threshold.

6. The method of claim 3, wherein the act (A340, A640) of making the request to the base station (210, 510, 910) to change the anchor carrier set comprises:

making (A410, A710) a determination as to whether the first carrier meets a predetermined minimum reliability threshold when it is determined that the anchor carrier set should be changed; and

making (A430, A730) a request to the base station (210, 510, 910) to include multiple carriers into the anchor carrier set when it is determined that the first carrier does not meet the predetermined minimum reliability threshold,

wherein the multiple carriers are chosen from the plurality of carriers that the user equipment (220, 520, 920) is capable of listening to so as to minimize a number of anchor carriers necessary to meet the predetermined minimum reliability threshold.

7. The method of claim 5,

wherein the base station (210, 510, 910) is a current serving base station (210, 510, 910), and

wherein the act (A720) of making the request to the base station (210, 510, 910) to include only the first carrier in the anchor carrier set comprises:

making (A810) a determination whether a handoff to a new serving base station (210, 510, 910) is required when it is determined that the first carrier meets the predetermined minimum reliability threshold;

making (A820) a request to the current serving base station (210, 510, 910) for the handoff when it is determined that the handoff is required; and

making (A830) a request to the new serving base station (210, 510, 910) to include only the first carrier in the anchor carrier set after the handoff is requested.

8. The method of claim 1, further comprising putting receivers of the user equipment (220, 520, 920) adapted to receive signals on carriers not in the anchor carrier set into a power conservation mode.

9. The method of claim 8, wherein putting each of the receivers in the conservation mode includes any one or more of turning off the receiver, enabling a DRX mode for the receiver, and narrowing a receiving frequency range of the receiver to exclude the non-anchor carriers.

10. The method of claim 1, further comprising:

receiving (A1040) an anchor hopping pattern from the base station (210, 510, 910); and

adapting (A1050) one or more receivers of the user equipment (220, 520, 920) to receive control signals transmitted from the base station (210, 510, 910) according to the anchor hopping pattern,

wherein the anchor hopping pattern specifies a sequence over time of one or more anchor carriers used by the user equipment (920) to receive the control signals transmitted by the base station (210, 510, 910).

11. The method of claim 10, further comprising:

making (A1030) a request to the base station (210, 510, 910) for the anchor hopping pattern when it is determined that the user equipment (220, 520, 920) is moving at a rate that is at or greater than a predetermined minimum speed threshold.

34. The method of claim 1, a number of anchor carriers in the anchor carrier set are changed after making request.

12. A user equipment (220, 520, 920) of a wireless network (200, 500, 900) comprising:

a communications unit (1230) arranged to communicate with a base station (210, 510, 910); and

a processing unit (1210) arranged to;

make a determination as to whether an anchor carrier set should be changed, wherein the anchor carrier set includes one or more anchor carriers used by the user equipment (220, 520, 920) to receive control signals transmitted from a base station (210, 510, 910); and

make a request to the base station (210, 510, 910), via the communications unit (1230), to change the anchor carrier set when it determines that the anchor carrier set should be changed.

13. The user equipment (220, 520, 920) of claim 12,

wherein the communications unit (1230) is capable of communicating with the base station (210, 510, 910) over a plurality of carriers with each carrier being associated with a bandwidth, and

wherein there is at least one gap in a frequency spectrum represented by the plurality of carriers.

14. The user equipment (220, 520, 920) of claim 12,

wherein the processing unit (1210) is arranged to determine that the anchor carrier set should be changed when a reliability of a first carrier is greater than a reliability of a second carrier, and

wherein the anchor carrier set includes the second carrier but does not include the first carrier.

15. The user equipment (220, 520, 920) of claim 14, wherein the processing unit (1210) is arranged to determine that the first carrier is more reliable than the second carrier when any when any one or more of the following is true:

a signal-to-interference ratio (SIR) of the first carrier is higher than a SIR of the second carrier,

a reference signal received power (RSRP) of the first carrier is higher than a RSRP of the second carrier,

a data transmission rate of the first carrier is greater than a data transmission rate of the second carrier,

an error rate of the first carrier is lower than an error rate of the second carrier, and

a repeat request rate of the first carrier is lower than a repeat request rate of the second carrier.

16. The user equipment (220, 520, 920) of claim 14, wherein the processing unit (1210) is arranged to request the change to the anchor carrier set by:

making a determination as to whether the first carrier meets a predetermined minimum reliability threshold when it is determined that the anchor carrier set should be changed; and

making a request to the base station (210, 510, 910) to include only the first carrier in the anchor carrier set when it makes the determination that the first carrier meets the predetermined minimum reliability threshold.

17. The user equipment (220, 520, 920) of claim 14, wherein the processing unit (1210) is arranged to request the change to the anchor carrier set by:

making a determination as to whether the first carrier meets a predetermined minimum reliability threshold when it determines that the anchor carrier set should be changed; and

making a request to the base station (210, 510, 910) to include multiple carriers into the anchor carrier set when it determines that the first carrier does not meet the predetermined minimum reliability threshold,

wherein the multiple carriers are chosen from the plurality of carriers the communications unit (1230) is capable of listening to so as to minimize a number of anchor carriers necessary to meet the predetermined minimum reliability threshold.

18. The user equipment (520) of claim 16,

wherein the base station (210, 510, 910) is a current serving base station (210, 510, 910), and

wherein the processing unit (1210) is arranged to:

make a determination whether a handoff to a new serving base station (210, 510, 910) is required when it determines that the first carrier meets the predetermined minimum reliability threshold;

make a request to the current serving base station (210, 510, 910) for the handoff when it determines that the handoff is required; and

make a request to the new serving base station (210, 510, 910) to include only the first carrier in the anchor carrier set after the handoff is requested.

19. The user equipment (520) of claim 12, wherein the processing unit (1210) is arranged to put receivers of the communications unit (1230) adapted to receive signals on carriers not in the anchor carrier set into a power conservation mode.

20. The user equipment (520) of claim 19, wherein putting each of the receivers in the conservation mode includes any one or more of turning off the receiver, enabling a DRX mode for the receiver, and narrowing a receiving frequency range of the receiver to exclude the non-anchor carriers.

21. The user equipment (220, 520, 920) of claim 12, wherein the communication unit (1230) includes:

two or more fixed bandwidth receivers with each receiver arranged to receive signals on corresponding carriers transmitted by the base station (210, 510, 910),

one or more adaptive bandwidth receivers with each receiver arranged to be dynamically adaptable to receive signals on one or more carriers transmitted by the base station (210, 510, 910), or

one or more fixed bandwidth receivers and one or more adaptive bandwidth receivers.

22. The user equipment (220, 520, 920) of claim 12, wherein the processing unit (1210) is arranged to:

receive, via the communications unit (1230), an anchor hopping pattern from the base station (210, 510, 910), and

adapt one or more receivers of the communications unit (1230) to receive the control signals transmitted from the base station (210, 510, 910) according to the anchor hopping pattern,

wherein the anchor hopping pattern specifies a sequence over time of one or more anchor carriers used by the user equipment (220, 520, 920) to receive the control signals transmitted by the base station (210, 510, 910).

23. The user equipment (220, 520, 920) of claim 22, further comprising:

a location detection unit (1240) arranged to determine a location of the user equipment (220, 520, 920), wherein

the processing unit (1210) is arranged to;

make a determination, via the location detection unit (1240), that the user equipment (220, 520, 920) is moving at a predetermined minimum speed threshold or greater; and

make a request to the base station (210, 510, 910), via the communications unit (1230), for the anchor hopping pattern when it determines that the user equipment (220, 520, 920) is moving at the predetermined minimum speed threshold or greater.

24. A method operating a base station (210, 510, 910) of a wireless network (200, 500, 900), comprising:

making a determination (A1120) as to whether anchor carrier sets should be updated for one or more user equipments (220, 520, 920), wherein the anchor carriers are used by a base station (210, 510, 910) to transmit control signals to the one or more user equipments (220, 520, 920); and

transmitting (A1130) to the one or more of the user equipments (220, 520, 920) a notification of the anchor carrier set update when it is determined that the anchor carrier sets should be updated.

25. The method of claim 24, wherein for each of the user equipments (220, 520, 920), the notification includes an indication of which carrier or carriers will be used by the base station (210, 510, 910) as anchor carrier or carriers for the user equipment (220, 520, 920) to transmit control signals.

26. The method of claim 24, wherein it is determined that the anchor carrier sets should be updated when any one or more of the following is true:

a signal-to-interference (SIR) of at least one anchor carrier falls below a predetermined minimum SIR threshold for any of the one or more user equipments (220, 520, 920);

an error rate of data transmitted over at least one anchor carrier passes over a predetermined error rate threshold for any of the one or more user equipments (220, 520, 920);

a repeat request rate of data transmitted over at least one anchor carrier falls below a predetermined repeat request rate threshold for any of the one or more user equipments (220, 520, 920);

a number of user equipments (220, 520, 920) being served by the base station (210, 510, 910) over a first carrier is greater than a number of user equipments (220, 520, 920) being served by the base station (210, 510, 910) over a second carrier by at least a predetermined number; and

an amount of data transmitted over the first carrier is greater than an amount of data transmitted over the second carrier by at least a predetermined amount.

27. The method of claim 24, further comprising:

making (A1020) a determination as to whether an anchor hopping pattern is needed for a user equipment (220, 520, 920);

providing (A1040) the anchor hopping pattern to the user equipment (920) when it is determined that the anchor hopping pattern is needed; and

transmitting (A1050) control signals to the user equipment (220, 520, 920) according to the anchor hopping pattern,

wherein the anchor hopping pattern specifies a sequence over time of one or more anchor carriers used by the base station (210, 510, 910) to transmit the control signals to the user equipment (220, 520, 920).

28. The method of claim 27, wherein it is determined that the anchor hopping pattern is needed when

it is determined that a user equipment (220, 520, 920) is moving at a rate that is at or greater than a predetermined minimum speed threshold, or

a request for the anchor hopping pattern is received from the user equipment (220, 520, 920).

29. A base station (210, 510, 910) of a wireless network (200, 500, 900), comprising:

a communications unit (1330) arranged to communicate with the user equipment (920); and

a processing unit (1310) arranged to;

make a determination as to whether anchor carrier sets should be updated for one or more user equipments (220, 520, 920), wherein the anchor carriers are used by a base station (210, 510, 910) to transmit control signals to the one or more user equipments (220, 520, 920); and

transmit to the one or more of the user equipments (220, 520, 920), via the communications unit (1330), a notification of the anchor carrier set update when it determines that the anchor carrier sets should be updated.

30. The base station (210, 510, 910) of claim 29, wherein for each of the user equipments (220, 520, 920), the notification includes an indication of which carrier or carriers will be used by the base station (210, 510, 910) as anchor carrier or carriers for the user equipment (220, 520, 920) to transmit control signals.

31. The base station (210, 510, 910) of claim 29, wherein the processing unit (1310) is arranged to make the determination as to whether anchor carrier sets should be updated when any one or more of the following is true:

a signal-to-interference (SIR) of at least one anchor carrier falls below a predetermined minimum SIR threshold for any of the one or more user equipments (220, 520, 920);

an error rate of data transmitted over at least one anchor carrier passes over a predetermined error rate threshold for any of the one or more user equipments (220, 520, 920);

a repeat request rate of data transmitted over at least one anchor carrier falls below a predetermined repeat request rate threshold for any of the one or more user equipments (220, 520, 920);

a number of user equipments (220, 520, 920) being served by the base station (210, 510, 910) over a first carrier is greater than a number of user equipments (220, 520, 920) being served by the base station (210, 510, 910) over a second carrier by at least a predetermined number; and

an amount of data transmitted over the first carrier is greater than an amount of data transmitted over the second carrier by at least a predetermined amount.

32. The base station (210, 510, 910) of claim 29, wherein processing unit (1310) arranged to:

make a determination as to whether an anchor hopping pattern is needed for a user equipment (220, 520, 920);

provide the anchor hopping pattern to the user equipment (220, 520, 920), via the communications unit (1330), when it is determined that the anchor hopping pattern is needed; and

transmit control signals to the user equipment (220, 520, 920), via the communications unit (1330), according to the anchor hopping pattern,

wherein the anchor hopping pattern specifies a sequence over time of one or more anchor carriers used by the base station (210, 510, 910) to transmit the control signals to the user equipment (220, 520, 920).

33. The method of claim 32, wherein the processing unit (1310) is arranged to determined that the anchor hopping pattern is needed when

the processing unit (1310) determines that a user equipment (220, 520, 920) is moving at a rate that is at or greater than a predetermined minimum speed threshold, or

a request for the anchor hopping pattern is received from the user equipment (220, 520, 920).