APPARATUS AND METHODS FOR ADAPTIVELY RESUMING RADIO CHANNEL ESTIMATION

• US 20130322586A1
• Filed: 05/03/2013
• Published: 12/05/2013
• Est. Priority Date: 05/03/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Tabet, Tarik, Damji, Navid, Song, Kee-Bong, Ji, Zhu, Mujtaba, Syed Aon, Sebeni, Johnson
• Granted Patent: US 9,967,112 B2
• Time in Patent Office: Days
• US Class Current: 375/350
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0256 Channel estimation using minimum mean square error criteria

Abstract

Methods and apparatus for resuming radio channel measurements and estimations after an interruption in reception. In one exemplary embodiment of the present disclosure, an adaptive solution is provided for channel estimation based at least in part on the reception interruption duration. In one variant, an LTE UE determines a windowing length and/or “shape” for a time domain channel estimation algorithm based on at least the interruption duration. In an alternate variant, an LTE UE determines the interpolation coefficients for a filter based on the interruption duration.

Claims

1. A method of performing radio channel estimation after an interruption in reception between a mobile device and a network, comprising:

determining a duration of the interruption in reception;

determining a channel estimation window based at least in part on the duration of the interruption, wherein the channel estimation window is characterized by a channel estimation window length and a channel estimation window shape; and

performing channel estimation in accordance with the determined channel estimation window;

wherein;

when the determined duration is less than a first threshold;

the channel estimation window length comprises a first channel estimation window length; and

the channel estimation window shape is determined before the interruption in reception;

when the determined duration is greater than the first threshold and less than a second threshold;

the channel estimation window length comprises a second channel estimation window length and is based at least in part on a noise estimate and a maximum delay spread; and

the channel estimation window shape is based at least on an unevenly weighted distribution; and

when the determined duration is greater than the second threshold;

the channel estimation window length comprises a third channel estimation window length and is based at least in part on a characteristic of a radio channel of the network; and

the channel estimation window shape comprises a third channel estimation window shape and is based at least in part on an evenly weighted distribution.

2. The method of claim 1, wherein the unevenly weighted distribution comprises at least one of a Gaussian distribution, an exponential distribution, a Hamming distribution, and an evenly weighted distribution.

3. The method of claim 1, further comprising updating a secondary channel estimate based, at least in part, on the performed radio channel estimation.

4. The method of claim 1, wherein the first threshold and the second threshold are based, at least in part, on a Doppler shift.

5. The method of claim 1, wherein performing a radio channel estimation comprises multiplying a Channel Impulse Response (OR) with a corresponding weight defined by a window shape.

6. The method of claim 1, further comprising determining a frequency domain channel estimate by transforming the radio channel estimation with a Fast Fourier Transfolin (FFT),

7. The method of claim 1, wherein the maximum delay spread is based on a relative spread of one or more window weights from a previous channel estimation.

8. The method of claim 7, further comprising replacing the performed radio channel estimation after a designated number of subframes with a second radio channel estimation based on a Minimum Mean Squared Estimation (MMSE).

9. The method of claim 8, wherein the designated number of subframes is based, at least in part, on a time constant of an Infinite Impulse Response (UR) filter.

10. An apparatus comprising:

a network interface;

a processor; and

a non-transitory computer readable storage medium with at least one computer program stored thereon, the at least one computer program configured to, when executed on the processor, cause the apparatus to;

interrupt communication with a first network for a first duration;

based at least in part on the length of the first duration, determine an appropriate channel estimation window characterized by a window shape and a window length; and

perform channel estimation in accordance with the determined appropriate channel estimation window.

11. The apparatus of claim 10, wherein the interrupted communication comprises a tune away event from the first network.

12. The apparatus of claim 10, wherein the appropriate channel estimation window is selected from a multi-tiered scheme, the multi-tiered scheme comprising increasingly conservative channel estimation techniques associated with longer tune away durations.

13. The apparatus of claim 10, wherein the at least one computer program is further configured to, when executed on the processor, cause the apparatus to determine interpolation coefficients for a filter.

14. The apparatus of claim 10, wherein the at least one computer program is further configured to, when executed on the processor, cause the apparatus to:

update a concurrently executed secondary channel estimation measurement based on the performed channel estimation.

15. The apparatus of claim 10, wherein the at least one computer program is further configured to, when executed on the processor, cause the apparatus to replace a concurrently executed secondary channel estimation measurement with one or more results of the channel estimation.

16. The apparatus of claim 10, wherein the appropriate channel estimation window is determined based on a weighted distribution and a window length, the window length determined by a noise estimate and a maximum delay spread.

17. The apparatus of claim 10, wherein the at least one computer program is further configured to, when executed on the processor, cause the apparatus to:

when the first duration is less than a first threshold;

the window length is based at least in part on a first channel estimation window length; and

the window shaped is based at least in part on a first channel estimation window shape determined before the interruption in reception;

when the first duration is greater than the first threshold and less than a second threshold;

the window shape is based at least in part on a second channel estimation window shape based at least in part on an unevenly weighted distribution, and

the window length is based at least in part on a second channel estimation window length based at least in part on a noise estimate and a maximum delay spread; and

when the first duration is greater than the second threshold;

the window shape is based at least in part on a third channel estimation window shape based at least in part on an evenly weighted distribution; and

the window length is based at least in part on a third channel estimation window length based at least in part on a characteristic of a radio channel of the network.

18. A base station comprising:

a network interface;

a processor; and

a non-transitory computer readable storage medium having a storage medium with at least one computer program stored thereon, the at least one computer program configured to, when executed on the processor, cause the base station to;

determine a duration of interruption between the base station and a mobile device;

determine an adjustment parameter for use in a channel estimation measurement, based on the determined duration of interruption; and

perform channel estimation in accordance with the determined adjustment parameter.

19. The base station of claim 18, wherein the at least one computer program is further configured to, when executed on the processor, cause the base station to update one or more concurrently executed secondary channel estimation measurements based on the results of the performed channel estimation.

20. The base station of claim 18, wherein the at least one computer program is further configured to, when executed on the processor, cause the base station to:

when the determined duration is less than a first threshold, the determined adjustment parameter is based at least in part on an initial window length and an initial window shape, where the initial window length and the initial window shape were determined prior to the interruption between the mobile device and the base station; and

when the determined duration is greater than the first threshold, the determined adjustment parameter is based at least on a weighted distribution based at least in part on a second window length, where the second window length is determined at least in part, by a noise estimate and a maximum delay spread.

21-24. -24. (canceled)