User equipment and method for adaptive selection of handover parameters in wireless-access networks

• US 8,818,376 B2
• Filed: 08/08/2012
• Issued: 08/26/2014
• Est. Priority Date: 01/27/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Yiu, Candy, Fong, Mo-Han
• Primary Examiner(s): MITCHELL, NATHAN A
• Application Number:
  US13/569,443
• Publication Number:
  US 20130196664A1
• Time in Patent Office: 748 Days
• Field of Search: 455436-444, 370331-334
• US Class Current: 455/436
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0623 Auxiliary parameters, e.g. power control [PCB] or not acknowledged commands [NACK], used as feedback information
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0027 Scheduling of signalling, e.g. occurrence thereof
• CPC Class Codes: H04L 1/0031 Multiple signaling transmission H04L1/1664, F15 take precedence
• CPC Class Codes: H04L 1/1864 ARQ related signaling H04L1/1607 takes precedence
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/1896 ARQ related signaling
• CPC Class Codes: H04L 12/189 in combination with wireless systems selective distribution or broadcast in wireless communication networks H04W4/06
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/1469 : using time-sharing
• CPC Class Codes: H04L 65/611 : for multicast or broadcast systems for broadcast or conference H04L12/18; arrangements for broadcast or distribution combined with broadcast H04H20/00; arrangements for broadcast applications with a direct linkage to broadcast information or to broadcast space-time H04H60/00; selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS], H04W4/06
• CPC Class Codes: H04L 65/65 : Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
• CPC Class Codes: H04W 36/0094 : Definition of hand-off measurement parameters
• CPC Class Codes: H04W 36/04 : Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 4/08 : User group management
• CPC Class Codes: H04W 4/70 : Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• CPC Class Codes: H04W 48/16 : Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0216 : using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 72/04 : Wireless resource allocation
• CPC Class Codes: H04W 72/044 : based on the type of the allocated resource
• CPC Class Codes: H04W 72/20 : Control channels or signalling for resource management
• CPC Class Codes: H04W 72/23 : in the downlink direction of a wireless link, i.e. towards a terminal
• CPC Class Codes: H04W 72/53 : based on regulatory allocation policies
• CPC Class Codes: H04W 72/541 : using the level of interference
• CPC Class Codes: H04W 72/542 : using measured or perceived quality
• CPC Class Codes: H04W 76/27 : Transitions between radio resource control [RRC] states
• CPC Class Codes: H04W 76/28 : Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• CPC Class Codes: Y02D 30/70 : in wireless communication networks

Abstract

Embodiments of user equipment (UE) and method for adaptively selecting an A3offset-TTT pair for handover in a wireless access network are generally described herein. In some embodiments, the UE may select an A3offset value based on target cell Reference Signal Received Power (RSRP) and select a time-to-trigger (TTT) based on serving cell RSRP. A measurement report may be transmitted to an eNodeB for handover when the target cell RSRP exceeds the serving cell RSRP by at least the A3offset value for the TTT. The A3offset value may be selected to be inversely related to the target cell RSRP and the TTT may be selected to be directly related to the serving cell RSRP.

Claims

1. A method performed by user equipment (UE) for adaptively selecting an A3offset-TTT pair for handover, the method comprising:

selecting an A3offset value based on target cell reference signal received Power (RSRP);

selecting a time-to-trigger (TTT) based on serving cell RSRP; and

transmitting a measurement report to an eNodeB for handover from a serving cell to a target cell when the target cell RSRP exceeds the serving cell RSRP by at least the A3offset value of the TTT,

wherein the A3offset value is selected to be inversely related to the target cell RSRP and the TTT is selected to be directly related to the serving cell RSRP,

wherein selecting the A3offset value comprises selecting one of a plurality of A3offset values based on the target cell RSRP and one or more RSRP thresholds, and

wherein selecting a TTT comprises selecting one of a plurality of TTTs based on the serving cell RSRP and the one or more RSRP thresholds.

2. The method of claim 1 further comprising:

receiving the plurality of A3offset values, the plurality of TTTs and the one or more RSRP thresholds from the eNodeB at connection establishment; and

storing the received A3offet values, TTTs and one or more RSRP thresholds in memory of the UE.

3. The method of claim 2 further comprising refraining from selecting or reselecting an A3offset value and TTT during an A3event, the A3event being when a measured target cell RSRP exceeds a measured serving cell RSRP by a currently selected A3offset value,

wherein selection and reselection of an A3offset value and TTT of an A3offset-TTT pair are performed outside of the A3event.

4. The method of claim 2 wherein based on the one or more RSRP threshods, greater A3offset values are selected for lower target cell RSRPs and lesser A3offset values are selected for higher target cell RSRPs, and

wherein based on the one or more RSRP thresholds, greater TTTs are selected for higher serving cell RSRPs and lesser TTTS are Selected for lower serving cell RSRPs.

5. The method of claim 1 wherein:

a first A3offset value is selected for the A3offset value when the target cell RSRP is greater than one of the RSRP thresholds;

a Second A3offSet value is selected for the A3offset value when the target cell RSRP is not greater than one of the RSRP thresholds;

a first TTT is selected to the TTT when the serving cell RSRP is greater than one of the RSRP thresholds; and

a second TTT is selected for the TTT when the serving cell RSRP is not greater than one of the RSRP thresholds,

wherein the first A3offset value is less than the second A3offset value, and the first TTT is greater than the second TTT.

6. The method of claim 1 wherein:

a first A3offset value is selected for the A3offset value when the target cell RSRP is greater than a first of the RSRP thresholds,

a second A3offset value is selected for the A3offset value when the target cell RSRP is greater than a second of the RSRP thresholds but is not greater than the first of the RSRP thresholds;

a third A3offset value is selected for the A3offset value when the target cell RSRP is not greater than the second of the RSRP thresholds;

a first TTT is selected for the TTT when the serving cell RSRP greater than the first of the RSRP thresholds;

a second TTT is selected for the TTT when the serving cell RSRP greater than the second of the RSRP thresholds but is not greater than the first of the RSRP thresholds; and

a third TTT is selected for the TTT when the serving cell RSRP is not greater than the second of the RSRP thresholds.

7. The method of claim 1 wherein the method further includes:

setting a TTT timer in response to an A3event, the TTT timer to expire after the selected TTT, the A3event including when the target cell RSRP exceeds the serving cell RSRP by at least a currently selected A3offset value;

stopping the TTT timer when the target cell RSRP does not exceed the serving cell RSRP by at least the selected A3offset value;

sending the measurement report to the eNodeB upon expiration of the TTT timer.

8. A method of claim 1 wherein the target cell and the serving cell comprise different cell layers, the different cell layers comprising a macro-cell layer and a micro-cell layer the macro-cell layer comprising marco cells, the micro-cell layer comprising micro-cells, pico-cells and femto-cells.

9. A method performed by user equipment (UE) for adaptively selecting an A3offset-TTT pair for handover, the method comprising:

selecting an A3offset value based on target cell reference signal received Power (RSRP);

selecting a time-to-trigger (TTT) based on serving cell RSRP; and

transmitting a measurement report to an eNodeB for handover from a serving cell to a target cell when the target cell RSRP exceeds the serving cell RSRP by at least the A3offset value for the TTT,

wherein the A3offset value is selected to be inversely related to the target cell RSRP and the TTT is selected to be directly related to the serving cell RSRP, and

wherein the method further comprises;

measuring the target cell RSRP based on an average of downlink reference signals transmitted by a target cell eNodeB across a channel bandwidth; and

measuring the serving cell RSRP based on an average of downlink reference signals transmitted by a serving cell eNodeB across the channel bandwidth,

wherein the A3offset value and the TTT of the A3offset-TTT pair are selected based on the measured RSRPs.

10. User equipment (UE) comprising:

processing circuitry to select an A3offset value based on a measured target cell reference signal received power (RSRP) and to select a time-to-trigger (TTT) based on a measured serving cell RSRP; and

physical layer circuitry to transmit a measurement report from a serving cell to a target cell when the target cell RSRP exceeds the serving cell RSRP by at least the A3offset value for the TTT,

wherein the A3offset value is selected to be inversely related the target cell RSRP and the TTT is selected to be directly related to the serving cell RSRP,

wherein the physical layer of circuitry is arranged to;

receive a plurality of A3offset values, a plurality of TTTs and one or more RSRP thresholds from an eNodeB at connection establishment; and

monitor the serving cell RSRP and the target cell RSRP,

wherein the processing circuitry is to select the A3offset value from the plurality of A3offset values based on the target cell RSRP and select the TTT from the plurality of TTTs based on the serving cell RSRP.

11. The UE of claim 10 wherein the processing circuitry is arranged to:

refrain from selecting or reselecting an A3offset value and TTT during an A3event, the A3event being when a measured target cell RSRP exceeds a measured serving cell RSRP by a currently selected A3offset value,

wherein selection and reselection of an A3offset value and TTT of an A3offset-TTT pair are performed outside of the A3event.

12. The UE of claim 11 wherein greater A3offset values are selected for lower target cell RSRPs and lesser A3offset values are selected for higher target cell RSRPs, and

wherein greater TTTs are selected for higher serving cell RSRPs and lesser TTTs are selected for lower serving cell RSRPs.

13. User equipment (UE) for operating in a wireless access network, the UE comprising:

physical layer circuitry to communicate with an enhanced node B (eNodeB) using two or more antennas in accordance with an orthogonal frequency division multiple access (OFDMA) technique, the physical layer circuitry to receive a plurality of A3offset values, a plurality of time-to-triggers (TTTs) and one of more reference signal received power (RSRP) thresholds from the eNodeB at connection establishment, the physical layer circuitry to measure RSRP of a target cell and a serving cell; and

processing circuitry to select one of the A3offset values based on the measured RSRP of the target cell and the one or more RSRP thresholds, and to select one of the TTTs based on the measured RSRP of the serving cell and the one or more RSRP thresholds.

14. The UE of claim 13 wherein the processing circuitry is arranged to transmit a measurement report to the eNodeB for handover initiation when the target cell RSRP exceeds the serving cell RSRP by at least the selected A3offset value selected TTT.

15. The UE of claim 14 wherein a greater A3offset value is selected for a lower target cell RSRP and a lesser A3offset value is selected for a higher target cell RSRP, and

wherein a greater TTT is selected for higher serving cell RSRPs and a lesser TTT is selected for lower serving cell RSRPs.

16. The UE of claim 15 wherein the processing circuitry is arranged to refrain from selecting or reselecting an A3offset value TTT during an A3event, the A3event being when the measured target cell RSRP exceeds the measured serving cell RSRP by a currently selected A3offset value,

wherein selection and reselection of an A3offset value and TTT of an A3offset-TTT pair are performed outside of the A3event.

17. A. method for handover comprising:

receiving a plurality of A3offset values, a plurality of time-to-triggers (TTTs) and one or more reference signal received power (RSRP) thresholds from an enhanced node B (eNodeB) at connection establishment;

measuring an RSRP of a target cell and an RSRP of a serving cell;

selecting one of the A3offset values based on the measured RSRP of the target cell and one or more RSRP thresholds, the A3offset value selected to be inversely related to the target cell RSRP; and

selecting one of the TTTs based on the measured RSRP of the serving cell and the one or more RSRP thresholds, the TTT selected to be directly related to the serving cell RSRP.

18. The method of claim 17 further comprising:

reselecting an A3offset value and a TTT from the pluralities as the serving cell and target cell RSRPs change; and

refraining from selecting or reselecting an A3offset value and a TTT during an A3event.

19. The method of claim 18 wherein the A3event includes a time when the measured target cell RSRP exceeds the measured serving cell RSRP by a currently selected A3offset value, and

wherein the method includes initiating handover from the serving cell to the target cell when the target cell RSRP exceeds the serving cell RSRP by at least the selected A3offset value for the selected TTT.