Scanning methods and apparatus which utilize a carrier signal bandwidth test

• US 20070254612A1
• Filed: 04/28/2006
• Published: 11/01/2007
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Wu, Huan, Simmons, Sean, Kemenczy, Zoltan
• Granted Patent: US 7,865,156 B2
• Time in Patent Office: Days
• US Class Current: 455/161.100
• CPC Class Codes: H03J 1/0091 provided with means for scanning over a band of frequencies H03J1/0058 takes precedence
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information

Abstract

One illustrative method of scanning a radio frequency (RF) band (e.g. 850 MHz band) for valid RF carrier signals of a wireless communication network (e.g. a GSM network) includes the steps of monitoring an RF channel to receive a candidate RF carrier signal; identifying whether the candidate RF carrier signal is a valid RF carrier signal of the wireless communication network by estimating a bandwidth of the candidate RF carrier signal and, if the estimated bandwidth is different from a predetermined bandwidth associated with valid RF carrier signals of the wireless communication network, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network; and repeating the acts of monitoring and identifying for a next RF channel of a plurality of RF channels associated with the wireless communication network. Preferably, the RF bandwidth estimation is performed together with a system signal detection process (e.g. FCCH detection). Advantageously, the time required to scan the RF band is reduced.

Claims

1. A method of scanning a radio frequency (RF) band for valid RF carrier signals of a wireless communication network, the method comprising the acts of:

monitoring an RF channel of the wireless communication network to receive a candidate RF carrier signal;

estimating a bandwidth of the candidate RF carrier signal;

if the estimated bandwidth is different from a predetermined bandwidth associated with valid RF carrier signals of the wireless communication network, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network; and

repeating the acts of monitoring and estimating for a next RF channel of a plurality of RF channels associated with the wireless communication network.

2. The method of claim 1, further comprising the acts of:

detecting whether the candidate RF carrier signal has a predetermined system signal of the wireless communication network modulated thereon; and

if there is a failure in detecting the predetermined system signal modulated on the candidate RF carrier signal, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network.

3. The method of claim 1, further comprising the acts of:

if the candidate RF carrier signal is a valid RF carrier signal, decoding system information from the valid RF carrier signal which includes a network identification of a wireless communication network; and

after scanning the RF band, selecting one of a plurality of wireless communication networks for communication based on network identifications decoded from the plurality of wireless communication networks.

4. The method of claim 1, further comprising the acts of:

if the candidate RF carrier signal is a valid RF carrier signal of the wireless communication network, decoding and saving system information from the valid RF carrier signal; and

if the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network, refraining from decoding and saving system information from the candidate RF carrier signal.

5. The method of claim 1, further comprising:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of FFT values; and

wherein the act of estimating comprises the further act of estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal.

6. The method of claim 1, further comprising:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of frequency strength values;

wherein the act of estimating comprises the further act of estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal; and

wherein the act of identifying comprises the further act of identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network based on the plurality of frequency power values.

7. The method of claim 1, further comprising:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal for producing a plurality of frequency strength values;

wherein the act of estimating comprises the further acts of estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values and counting each frequency power value that is above a limit set by a predetermined power threshold value for producing a count value; and

wherein the act of identifying comprises the further act of identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if the count value is below a limit set by a predetermined count value.

8. The method of claim 1, further comprising:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal for producing a plurality of frequency strength values;

wherein the act of estimating comprises the further acts of estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values, performing at least one of averaging and normalizing the frequency power values, and counting each frequency power value that is above a limit set by a predetermined power threshold value for producing a count value; and

wherein the act of identifying comprises the further act of identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if the count value is outside below a limit set by a predetermined count value.

9. The method of claim 1, wherein the predetermined system signal comprises a frequency correction signal.

10. The method of claim 1, which is performed by a mobile station which is adapted to communication through the wireless communication network.

11. The method of claim 1, wherein the wireless communication network comprises a Global System for Mobile Communications (GSM) network.

12. A communication device, comprising:

a radio frequency (RF) channel scanner which is adapted to monitor, with use of a wireless transceiver, each one of a plurality of a radio frequency (RF) channels of an RF band of a wireless communication network to identify one or more candidate RF carrier signals;

an RF carrier signal validator comprising an RF carrier signal bandwidth estimator which is adapted to estimate a bandwidth of each candidate RF carrier signal identified from the RF channel scanner; and

the RF carrier signal validator being adapted to identify that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if the estimated bandwidth of the candidate RF carrier signal is different from a predetermined bandwidth associated with valid RF carrier signals of the wireless communication network.

13. The communication device of claim 12, further comprising:

the RF carrier signal validator including a system signal detector which is adapted to identify a predetermined system signal of the wireless communication network modulated on the candidate RF carrier signal; and

the RF carrier signal validator being adapted to identify that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if there is a failure in identifying the predetermined system signal on the candidate RF carrier signal.

14. The communication device of claim 12, further comprising:

a system signal detector which is adapted to identify a predetermined system signal of the wireless communication network modulated on the candidate RF carrier signal;

the system signal detector comprising a frequency correction channel (FCCH) detector and the predetermined system signal comprises a FCCH burst signal; and

the RF carrier signal validator being further adapted to identify that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if there is a failure in identifying the predetermined system signal on the candidate RF carrier signal.

15. The communication device of claim 12, further comprising:

a channel decoder which is adapted to decode and save system information from the candidate RF carrier signal if the candidate RF carrier signal is a valid RF carrier signal.

16. The communication device of claim 12, further comprising:

a channel decoder which is adapted to decode and save system information from the candidate RF carrier signal if the candidate RF carrier signal is a valid RF carrier signal, the system information including a network identification of the wireless communication network; and

a network selector which is adapted to select one of a plurality of wireless communication networks for communication based on network identifications decoded from the plurality of wireless communication networks.

17. The communication device of claim 12, wherein the RF carrier signal bandwidth estimator further comprises:

a Fast-Fourier Transform (FFT) component which is adapted to perform an FFT on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of FFT values; and

a frequency power estimator which is adapted to estimate a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal.

18. The communication device of claim 12, further comprising:

wherein the RF carrier signal bandwidth estimator further comprises;

a Fast-Fourier Transform (FFT) component which is adapted to perform an FFT on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of FFT values;

a frequency power estimator which is adapted to estimate a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal; and

wherein the RF carrier signal validator is adapted to identify that the candidate RF carrier signal is not a valid RF carrier signal based on the plurality of frequency power values.

19. The communication device of claim 12, which comprises a mobile station which is adapted to communicate with the wireless communication network.

20. A computer program product, comprising:

a storage medium;

computer instructions stored on the storage medium;

the computer instructions being executable by one or more processors for scanning a radio frequency (RF) band for valid RF carrier signals of a wireless communication network by;

monitoring an RF channel of the wireless communication network to

receive a candidate RF carrier signal;

estimating a bandwidth of the candidate RF carrier signal;

if the estimated bandwidth is different from a predetermined bandwidth associated with valid RF carrier signals of the wireless communication network, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network; and

repeating the acts of monitoring and estimating for a next RF channel of a plurality of RF channels associated with the wireless communication network.

21. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

detecting whether the candidate RF carrier signal has a predetermined system signal of the wireless communication network modulated thereon; and

if there is a failure in detecting the predetermined system signal modulated on the candidate RF carrier signal, identifying that the candidate RF signal is not a valid RF carrier signal of the wireless communication network.

22. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

if the candidate RF carrier signal is a valid RF carrier signal, decoding system information from the valid RF carrier signal which includes a network identification of a wireless communication network; and

after scanning the RF band, selecting one of a plurality of wireless communication networks for communication based on network identifications decoded from the plurality of wireless communication networks.

23. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

if the candidate RF carrier signal is a valid RF carrier signal of the wireless communication network, decoding and saving system information from the valid RF carrier signal; and

if the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network, refraining from decoding and saving any system information from the candidate RF carrier signal.

24. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of FFT values; and

wherein the estimating further comprises estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal.

25. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal, to thereby produce a plurality of frequency strength values;

wherein the estimating further comprises estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values which represent at least a portion of the bandwidth of the candidate RF carrier signal; and

wherein the identifying further comprises identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network based on the plurality of frequency power values.

26. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal for producing a plurality of frequency strength values;

wherein the estimating further comprises estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values, and counting each frequency power value that is above a limit set by a predetermined power threshold value for producing a count value; and

wherein the identifying further comprises identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if the count value is below a limit set by a predetermined count value.

27. The computer program product of claim 20, wherein the computer instructions are further executable by the one or more processors for:

performing a Fast-Fourier Transform (FFT) process on digitized data which represents the candidate RF carrier signal for producing a plurality of frequency strength values;

wherein the estimating further comprises estimating a frequency power value from each frequency strength value for producing a plurality of frequency power values, performing at least one of averaging and normalizing the frequency power values, and counting each frequency power value that is above a limit set by a predetermined power threshold value for producing a count value; and

wherein the identifying further comprises identifying that the candidate RF carrier signal is not a valid RF carrier signal of the wireless communication network if the count value is below a limit set by a predetermined count value.