Granted Patent B2

US 7,460,869 · App. 11/132,372 · Granted Dec 2, 2008

Abstract

Claims (81)

1. A method comprising:

determining cell parameters for a current cell, wherein the current cell broadcasts a broadband digital signal;

determining a handover measurement interval based on the cell parameters;

determining that a signal is scheduled to be received at a predetermined time;

adjusting the handover measurement interval so that a handover measurement is scheduled to coincide with the predetermined time; and

measuring a signal quality of one or more candidate cells at a time varying based on the handover measurement interval.

2. The method of claim 1 , further comprising:

receiving the broadband digital signal from the current cell;

determining a rate of signal quality change over time for the current cell; and

adjusting the handover measurement interval based on the rate of signal quality change.

3. The method of claim 2 , wherein the rate of signal quality change over time is determined at least in part by calculating a rate of signal strength change.

4. The method of claim 2 , wherein the rate of signal quality change over time is determined at least in part by calculating a rate of change for one of a bit error ratio and a packet error ratio.

5. The method of claim 1 , further comprising:

determining a receiver speed relative to a cell transmission station; and

adjusting the handover measurement interval based on the receiver speed.

6. The method of claim 5 , wherein the receiver speed relative to a cell transmission station is determined in part by measuring the Doppler shift of signals received from the cell transmission station.

7. The method of claim 1 , wherein the cell parameters comprise a size of the current cell.

8. The method of claim 1 , wherein a previously received signal indicates the predetermined time.

9. An apparatus comprising:

a receiver configured to receive a digital broadband broadcast signal from a transmitter in a current cell;

a processor configured to:

determine parameters for the current cell;

determine a handover measurement interval based on the current cell parameters;

determine that a signal is scheduled to be received at a predetermined time;

adjust the handover measurement interval so that a handover measurement is scheduled to coincide with the predetermined time; and

schedule a handover measurement at a time based on the handover measurement interval.

10. The apparatus of claim 9 , further comprising:

a memory, and

wherein the processor is further configured to:

store signal quality information for the current cell in the memory; and

calculate an adjustment to the handover measurement interval based on the stored signal quality information for the current cell.

11. The apparatus of claim 10 , wherein the signal quality information comprises signal strength measurements over time.

12. The apparatus of claim 10 , wherein the signal quality information comprises one of a bit error ratio and a packet error ratio calculated over time.

13. The apparatus of claim 9 , wherein the processor is further configured to:

determine a speed of the apparatus relative to the transmitter; and

calculate an adjustment to the handover measurement interval based on the apparatus speed.

14. The apparatus of claim 13 , wherein the speed of the apparatus is determined by estimating the Doppler shift of a carrier frequency caused by movement of the apparatus.

15. The apparatus of claim 9 , wherein current cell parameters are determined by receiving the parameters via the digital broadband broadcast signal.

16. The apparatus of claim 15 , wherein the current cell parameters comprise a cell size.

17. The apparatus of claim 9 , wherein a previously received digital broadband broadcast signal at the receiver indicates the predetermined time.

18. An apparatus comprising:

a receiver configured to receive digital broadband broadcast burst signals from a transmitter in a cell;

a memory configured to store information relevant to the cell; and

a processor, configured to:

determine a size of the cell;

retrieve signal quality measurements from the receiver;

store signal quality measurements in the memory;

determine a handover measurement interval based on the size of the cell;

adjust the handover measurement interval based on the signal quality measurements stored in the memory; and

schedule handover measurements at a time based on the handover measurement interval.

19. The apparatus of claim 18 , wherein the processor is configured to determine the size of the current cell by:

receiving longitude and latitude information about the cell via the receiver from the digital broadband broadcast burst signals; and

calculating a size of the cell based on the longitude and latitude information.

20. The apparatus of claim 18 , further comprising:

a positioning system, wherein the processor is further configured to:

receive a location of the apparatus from the positioning system;

calculate a speed and a direction of the apparatus based on changes in the location; and

adjust the handover measurement interval based on the calculated speed and direction of the apparatus.

21. An apparatus, comprising:

circuitry configured to perform the following:

determining a speed of the apparatus moving through a current cell by performing the following:

receiving a channel impulse response of a Doppler shifted signal;

performing a Fast Fourier Transform on the channel impulse response to produce a Doppler power spectrum;

estimating a Doppler spread frequency based on the Doppler power spectrum; and

calculating the speed of the apparatus by dividing the Doppler spread frequency by a carrier frequency and multiplying the resulting ratio by the speed of light; and

determining at least a portion of a handover measurement interval based on the speed of the apparatus.

22. The apparatus of claim 21 , wherein the circuitry is further configured to determine at least a portion of the handover measurement interval based on a predetermined time at which a signal is scheduled to be received.

23. The apparatus of claim 22 , wherein the circuitry is further configured to use the portions of the handover measurement interval to schedule a handover measurement to occur at a time to coincide with the predetermined time.

24. One or more computer readable media storing computer code that, when executed, cause a computer to perform a method comprising:

determining parameters for a current cell;

determining a handover measurement interval based on the parameters;

determining that a signal is scheduled to be received at a predetermined time;

adjusting the handover measurement interval so that a handover measurement is scheduled to coincide with the predetermined time; and

measuring the signal quality of one or more candidate cells at a time varying based on the handover measurement interval.

25. The computer readable media of claim 24 , storing further computer code, that when executed, cause the computer to:

perform the adjusting by scheduling a handover measurement to coincide with the predetermined time by occurring at a time immediately after the predetermined time.

26. The computer readable media of claim 24 , storing further computer code, that when executed, cause the computer to: ,

receive a digital broadband broadcast burst at the predetermined time, followed by performing the handover measurement.

27. The computer readable media of claim 24 , storing further computer code, that when executed, cause the computer to:

determine a Doppler shift of signals received from a cell transmission station; and

calculate a speed relative to the cell transmission station based on the Doppler shift.

Assignments (8)