METHOD AND APPARATUS FOR FREQUENCY SCAN IN NARROW BAND - INTERNET OF THINGS (NB-IOT) SYSTEMS

• US 20180317161A1
• Filed: 04/25/2018
• Published: 11/01/2018
• Est. Priority Date: 04/28/2017
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: ABEDINI, Navid, HSU, Chun-Hao, MATHUR, Amit, UPPALA, Sathyadev Venkata, TAM, Wingip
• Granted Patent: US 10,455,485 B2
• Time in Patent Office: Days
• CPC Class Codes: H04J 11/0086 Search parameters, e.g. search strategy, accumulation length, range of search, thresholds code acquisition in DSSS H04B1/7075
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Techniques for efficient and accurate frequency scans in Narrow Band-Internet of Things (NB-IoT) systems are provided. In an example, a user equipment (UE) searches for a cell on at least one of a plurality of frequency rasters based on a multi-stage search technique, wherein each stage of the multi-stage search searches the at least one frequency raster based on a different set of search parameters. The UE detects a cell on at least one of the frequency rasters based on the searching.

Claims

1. A method for wireless communication by a User Equipment (UE), comprising:

searching for a cell on at least one of a plurality of frequency rasters based on a multi-stage search technique, wherein each stage of the multi-stage search searches the at least one frequency raster based on a different set of search parameters; and

detecting a cell on at least one of the frequency rasters based on the searching.

2. The method of claim 1, wherein the different set of search parameters for each stage of the multi-stage search includes different dwell times, a dwell time corresponding to an amount of time the UE searches a frequency raster,

wherein the UE, in different stages of the multi-stage search, is configured to search the at least one frequency raster for a different dwell time.

3. The method of claim 2, wherein the UE searches the at least one frequency raster one stage at a time starting from a stage corresponding to the smallest dwell time and in ascending order of dwell times.

4. The method of claim 3, wherein the UE terminates the searching in response to detecting a cell.

5. The method of claim 1, further comprising:

upon detecting a cell x on frequency raster n in stage k of the multi-stage search, determining if the detected cell x satisfies a performance criterion;

determining that the cell x is correctly detected on raster n, if the detected cell s satisfies the performance criterion; and

performing additional processing if the detected cell x fails to satisfy the performance criterion.

6. The method of claim 5, wherein the performance criterion is a function of one or a combination of two or more performance metrics of a set of performance metrics of the detected cell, the set of performance metrics including quality of the detected cell, identification of the detected cell, a raster index of the detected cell, a stage index, timing of the detected cell, and frequency of the detected cell.

7. The method of claim 5, wherein the performance criterion includes a Signal to Noise Ratio (SNR) of the detected cell being higher than a threshold SNR, the threshold SNR being a function of an identification (ID) of the detected cell, a raster index of the detected cell, and a stage index of the stage of the multi-stage search using which the cell was detected.

8. The method of claim 7, wherein the cell ID of the detected cell is from a first set of cell IDs assigned a first threshold SNR, the first threshold SNR chosen as the threshold SNR for the performance criterion, wherein the first threshold SNR is different from a second threshold SNR assigned to a second set of cell IDs different from the first set.

9. The method of claim 5, wherein at least one parameter for performing the additional processing is a function of one or more performance metrics of the detected cell.

10. The method of claim 9, wherein the performance metrics include quality of the detected cell, identification of the detected cell, a raster index of the detected cell, a stage index, timing of the detected cell, and frequency of the detected cell.

11. The method of claim 5, wherein the additional processing includes searching for a cell on at least one frequency raster adjacent to the frequency raster n, wherein the searching for the additional processing is limited to at least one of a timing window or a frequency window based on at least one of an estimated timing or an estimated frequency of the detected cell.

12. The method of claim 5, wherein the additional processing includes searching for a cell on at least one frequency raster adjacent to the frequency raster n, wherein a dwell time for the searching for the additional processing is a function of at least one of a stage of the multi-stage search in which the cell was detected or an SNR of the detected cell,

the dwell time corresponding to an amount of time the UE searches a frequency raster.

13. The method of claim 5, wherein the additional processing includes searching for a cell on at least one frequency raster adjacent to the frequency raster n, wherein the searching for the additional processing is limited to a subset of cell Identities (IDs) as a function of at least one of a cell ID of the detected cell or an SNR of the detected cell.

14. The method of claim 5, wherein the additional processing comprises:

searching for a cell on at least one frequency raster adjacent to the frequency raster n;

detecting a cell y based on the searching on the at least one adjacent frequency raster;

comparing performance metrics of the cell y with performance metrics of cell x; and

determining cell y or cell x as a correctly detected cell on a corresponding frequency raster, based on the comparison.

15. The method of claim 14, wherein the determining comprises designating cell y or cell x with a stronger detected SNR as the correctly detected cell.

16. The method of claim 14, wherein the determining is a function of cell identities of the cells x and y.

17. The method of claim 14, wherein the determining is a function of relative timing of the cells x and y.

18. The method of claim 5, wherein the additional processing comprises:

searching for a cell on at least one frequency raster adjacent to the frequency raster n;

determining that the cell is correctly detected on raster n, if no cell is detected on the at least one adjacent frequency raster.

19. The method of claim 1, wherein searching the at least one frequency raster comprises:

processing multiple instances of a synchronization signal received on the frequency raster based on a set of threshold values; and

detecting a cell on the at least one frequency raster, based on the processing.

20. The method of claim 19, wherein the set of threshold values includes a threshold value corresponding to each of the multiple instances.

21. The method of claim 20, wherein threshold values in the set are arranged in descending order, the highest threshold value corresponding to the first processing instance.

22. The method of claim 19, wherein the synchronization signal includes at least one of a Primary Synchronization Signal (PSS) or a Secondary Synchronization Signal (SSS).

23. The method of claim 19, wherein processing the multiples instances of the synchronization signal comprises:

for each instance, correlating received samples of the instance with a set of reference signals; and

combining results of the correlating for the multiple instances; and

comparing a result of the combining with one of the set of threshold values.

24. The method of claim 19, wherein each of the multiple instances of the synchronization signal corresponds to a combination of two or more parameters including time, frequency, cell identity, or x msec boundaries.

25. An apparatus for wireless communication by a User Equipment (UE), comprising:

means for searching for a cell on at least one of a plurality of frequency rasters based on a multi-stage search technique, wherein each stage of the multi-stage search searches the at least one frequency raster based on a different set of search parameters; and

means for detecting a cell on at least one of the frequency rasters based on the searching.

26. The apparatus of claim 25, wherein the different set of search parameters for each stage of the multi-stage search includes different dwell times, a dwell time corresponding to an amount of time the UE searches a frequency raster,

wherein the means for searching, in different stages of the multi-stage search, is configured to search the at least one frequency raster for a different dwell time.

27. An apparatus for wireless communication by a User Equipment (UE), comprising:

at least one processor configured to;

search for a cell on at least one of a plurality of frequency rasters based on a multi-stage search technique, wherein each stage of the multi-stage search searches the at least one frequency raster based on a different set of search parameters; and

detect a cell on at least one of the frequency rasters based on the searching; and

a memory coupled to the at least one processor.

28. The apparatus of claim 27, wherein the different set of search parameters for each stage of the multi-stage search includes different dwell times, a dwell time corresponding to an amount of time the UE searches a frequency raster,

wherein the at least one processor, in different stages of the multi-stage search, is configured to search the at least one frequency raster for a different dwell time.

29. A computer-readable medium for wireless communication by a User Equipment (UE), the computer-readable medium storing instructions which when processed by at least one processor performs a method comprising:

searching for a cell on at least one of a plurality of frequency rasters based on a multi-stage search technique, wherein each stage of the multi-stage search searches the at least one frequency raster based on a different set of search parameters; and

detecting a cell on at least one of the frequency rasters based on the searching.

30. The computer-readable medium of claim 29, wherein the different set of search parameters for each stage of the multi-stage search includes different dwell times, a dwell time corresponding to an amount of time the UE searches a frequency raster,

wherein the UE, in different stages of the multi-stage search, is configured to search the at least one frequency raster for a different dwell time.