Handover schemes for wireless systems

• US 8,811,339 B2
• Filed: 07/06/2009
• Issued: 08/19/2014
• Est. Priority Date: 07/07/2008
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Fong, Mo-Han, Zhang, Hang, Vrzic, Sophie, Novak, Robert
• Primary Examiner(s): Nguyen, Thai
• Application Number:
  US12/806,185
• Publication Number:
  US 20110149904A1
• Time in Patent Office: 1,870 Days
• Field of Search: 370/445, 370/328, 370/331, 370/332, 370/338, 455/437, 455/439, 455/442
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0058 Transmission of hand-off measurement information, e.g. measurement reports

Abstract

One method of wireless communication involves acknowledging that an anchor base station received a handover indication signal. Another method involves: receiving, from base stations of an active set, offset signals identifying a respective differences in time between a reference time and respective times when the base station received a ranging signal from a mobile station; and transmitting, to the mobile station, a ranging control signal in response to the respective offset signals. Another method involves transmitting, to a mobile station in response to an active set signal, a system configuration information signal including system configuration information of a base station in an active set. Another method involves determining an uplink control channel power parameter in response to channel condition signals received from base stations in an active set. Another method involves transmitting a control signal to base stations in an active set on respective control channels. Apparatuses are also disclosed.

Claims

1. A method of a user equipment (UE) in an orthogonal frequency division multiplexing (OFDM) system comprising:

performing network entry via a first base station;

receiving system information via a unicast message from the first base station for at least one other base station, wherein the system information includes a preamble index for each of the at least one other base station, and each of the at least one other base station belongs to an active set of the UE;

measuring, at the UE, a signal strength of a signal of each of the at least one other base station, the measurement based on the received system information, wherein the signal strength is measured using a plurality of OFDM pilot tones, wherein the plurality of OFDM pilot tones are arranged in a scattered pattern in time and frequency;

determining, at the UE, whether the signal strength for each of the at least one other base stations exceeds a pre-defined pilot tone signal strength threshold; and

reporting, from the UE to the first base station, the signal strength corresponding to the base stations determined to exceed the pre-defined pilot tone signal strength threshold.

2. The method of claim 1, further comprising handing over to a second base station, wherein the second base station is one of the at least one other base stations.

3. The method of claim 1, wherein the signal is a preamble.

4. The method of claim 1, wherein the unicast message is received in connected state.

5. The method of claim 1, further comprising reporting the signal strength of each of the at least one other base station to the first base station.

6. The method of claim 1, wherein the system information is received from the first base station via a relay station.

7. A user equipment comprising:

a hardware processor; and

a transceiver, the transceiver configured to communicate with elements of a wireless communications network;

the hardware processor configured to control the transceiver to;

perform network entry via a first base station;

receive system information via a unicast message from the first base station for at least one other base station, wherein the system information includes a preamble index for each of the at least one other base station, and each of the at least one other base station belongs to an active set of the user equipment;

measure a signal strength of a signal of the at least one other base station, the measurement based on the received system information, wherein the signal strength is measured using a plurality of orthogonal frequency division multiplexing (OFDM) pilot tones, wherein the OFDM pilot tones are arranged in a scattered pattern in time and frequency;

determine whether the signal strength for each of the at least one other base stations exceeds a pre-defined pilot tone signal strength threshold; and

report, to the first base station, the signal strength corresponding to the base stations determined to exceed the pre-defined pilot tone signal strength.

8. The user equipment of claim 7, further configured to hand over to a second base station, wherein the second base station is one of the at least one other base stations.

9. The user equipment of claim 7, wherein the signal is a preamble.

10. The user equipment of claim 7, wherein the unicast message is received in connected state.

11. The user equipment of claim 7, further configured to report the signal strength of each of the at least one other base station to the first base station.

12. The user equipment of claim 7, wherein the system information is received from the first base station via a relay station.

13. A non-transitory machine-readable medium with a set of instructions stored thereon, which when executed, cause a processor of a user equipment (UE) in an orthogonal frequency division multiplexing (OFDM) system to perform operations comprising:

performing network entry via a first base station;

receiving system information via a unicast message from the first base station for at least one other base station, wherein the system information includes a preamble index for each of the at least one other base station, and each of the at least one other base station belongs to an active set of the UE;

measuring a signal strength of a signal of each of the at least one other base station, the measurement based on the received system information, wherein the signal strength is measured using a plurality of OFDM pilot tones, wherein the plurality of OFDM pilot tones are arranged in a scattered pattern in time and frequency;

determining whether the signal strength for each of the at least one other base stations exceeds a pre-defined pilot tone signal strength threshold; and

reporting, to the first base station, the signal strength corresponding to the base stations determined to exceed the pre-defined pilot tone signal strength threshold.

14. The non-transitory machine-readable medium of claim 13, the operations further comprising handing over to a second base station, wherein the second base station is one of the at least one other base stations.

15. The non-transitory machine-readable medium of claim 13, wherein the signal is a preamble.

16. The non-transitory machine-readable medium of claim 13, wherein the unicast message is received in connected state.

17. The non-transitory machine-readable medium of claim 13, the operations further comprising reporting the signal strength of each of the at least one other base station to the first base station.

18. The non-transitory machine-readable medium of claim 13, wherein the system information is received from the first base station via a relay station.