Signal scanning systems and methods for multiple-mode cellular radiotelephones

• US 6,553,229 B1
• Filed: 09/28/2000
• Issued: 04/22/2003
• Est. Priority Date: 11/24/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson), Telefonaktiebolaget LM Ericsson
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul Wilkinson
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): Tran, Pablo N
• Application Number:
  US09/672,758
• Time in Patent Office: 936 Days
• Field of Search: 455/425, 455/436, 455/421, 455/552, 455/437, 455/553, 455/563, 455/564, 455/67.1, 455/67.2, 455/266, 455/188.1, 455/33.1, 455/131-132, 455/139, 370/342, 370/312, 370/320-321, 370/334-335, 370/318, 370/319, 370/337, 370/465-466, 370/481, 370/486-487, 375/267, 375/299, 375/347, 375/349, 375/356, 375/200, 375/295, 375/316
• US Class Current: 455/434
• CPC Class Codes: H03J 1/0075 where the receiving frequencies of the stations are stored in a permanent memory, e.g. ROM
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

Multiple-mode cellular radiotelephones use a wide bandwidth receiving mode while scanning for signals in a narrow bandwidth receiving mode. Thus, when it is desired to scan the received frequency band to search for the presence of narrowband signals, the wider receiver bandwidth is first selected. When significant signal energy is identified in the wider bandwidth, a further scan using the narrowband mode may then be provided in order to locate the narrow bandwidth channel containing the strongest signal. In another embodiment, the signals that are received in the wider bandwidth mode are digitized to obtain complex signal samples. The complex signal samples are then processed to determine energy in each of a plurality of narrower bandwidths corresponding to channels in the narrower bandwidth cellular radiotelephone standards. Accelerated scanning of TDMA cellular channels may be obtained by tuning the cellular radiotelephone to a succession of frequency channels within one TDMA time slot and measuring signal strength for each of the succession of frequency channels. Tuning and measuring is then repeated for remaining ones of the TDMA time slots in the TDMA frame, preferably using the same channels in the same order. For each frequency channel, the signal strength that is the greatest measured signal strength of the frequency channel in all of the TDMA slots is assigned to that frequency channel. The assigned signal strengths may then be used to select a frequency channel for TDMA signal acquisition. Historical information may also be used to accelerate scanning of cellular channels by a cellular radiotelephone.

Claims

1. A multiple-mode cellular radiotelephone, comprising:

means for selecting one of a wide bandwidth receiving mode corresponding to a first cellular radiotelephone standard, and a narrow bandwidth receiving mode that is narrower than the wide bandwidth receiving mode, corresponding to a second cellular radiotelephone standard ; and

means for controlling the means for selecting to select the wide bandwidth receiving mode while scanning for signals in the narrow bandwidth receiving mode.

2. A multiple-mode cellular radiotelephone according to claim 1 wherein the means for controlling further comprises:

means for controlling the means for selecting to select the narrow bandwidth receiving mode while scanning for signals in the wide bandwidth receiving mode.

3. A multiple-mode cellular radiotelephone according to claim 1 wherein the first and second cellular radiotelephone standards comprise two of the cellular radiotelephone standards selected from AMPS, IS95 and GSM.

4. A multiple-mode cellular radiotelephone according to claim 1, further comprising:

means for digitizing signals that are received in the wide bandwidth receiving mode while scanning for signals in the narrow bandwidth receiving mode, to obtain digitized complex signal samples of the wide bandwidth receiving mode; and

means for processing the digitized complex signal samples to determine energy in each of a plurality of narrow bandwidths corresponding to channels in the second cellular radiotelephone standard.

5. A multiple-mode cellular radiotelephone according to claim 1:

wherein the means for controlling further comprises means for controlling a receiver to tune to a sequence of channel frequencies in the wide bandwidth receiving mode and to make signal measurements on the sequence of channel frequencies;

the dual-mode radiotelephone further comprising means for processing the signal measurements to select at least one channel frequency from the sequence of channel frequencies, and means for controlling the means for selecting to select the narrow bandwidth receiving mode and to scan the at least one channel frequency in the narrow bandwidth receiving mode.

6. A method of searching for control channel signals in a multiple-mode cellular radiotelephone that conforms to at least two cellular radiotelephone standards of different signal bandwidths, the searching method comprising the step of:

selecting a receiver bandwidth conforming to a wider one of the at least two cellular radiotelephone standards of different signal bandwidths while searching for control channels that conform to a narrower one of the at least two cellular radiotelephone standards of different signal bandwidths relative to the wider one of the at least two cellular radiotelephone standards of different signal bandwidths.

7. A method according to claim 6 further comprising the step of:

selecting a receiver bandwidth conforming to a narrower one of the at least two cellular radiotelephone standards of different signal bandwidths while searching for control channels that conform to a wider one of the at least two cellular radiotelephone standards of different signal bandwidths relative to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.

8. A method according claim 6 wherein the at least two cellular radiotelephone standards of different signal bandwidths comprise at least two of the cellular radiotelephone standards selected from AMPS, IS95 and GSM.

9. A method according to claim 6, further comprising the steps of:

digitizing signals that are received in response to the selecting step to obtain complex signal samples; and

processing the complex signal samples to determine energy in each of a plurality of narrow bandwidths corresponding to channels in the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.

10. A method according to claim 6 further comprising the steps of:

searching for control channels that conform to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths by controlling a receiver to tune to a sequence of channel frequencies in the wider one of the at least two cellular radiotelephone standards of different signal bandwidths;

making signal measurements on the sequence of channel frequencies;

processing the signal measurements to select at least one channel frequency from the sequence of channel frequencies;

selecting a receiver bandwidth conforming to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths; and

scanning the at least one channel frequency using the receiver bandwidth conforming to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.

11. A multiple-mode cellular radiotelephone that conforms to at least two cellular radiotelephone standards of different signal bandwidths, the multiple-mode cellular radiotelephone comprising:

a selector that selects a receiver bandwidth conforming to a wider one of the at least two cellular radiotelephone standards of different signal bandwidths while searching for control channels that conform to a narrower one of the at least two cellular radiotelephone standards of different signal bandwidths relative to the wider one of the at least two cellular radiotelephone standards of different signal bandwidths.

12. A multiple-mode cellular radiotelephone according to claim 11 wherein the selector also selects a receiver bandwidth conforming to a narrower one of the at least two cellular radiotelephone standards of different signal bandwidths while searching for control channels that conform to a wider one of the at least two cellular radiotelephone standards of different signal bandwidths relative to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.

13. A multiple-mode cellular radiotelephone according to claim 11 wherein the at least two cellular radiotelephone standards of different signal bandwidths comprise at least two of the cellular radiotelephone standards selected from AMPS, IS95 and GSM.

14. A multiple-mode cellular radiotelephone according to claim 11, further comprising:

a digitizer that digitizes signals that are received in response to the selector to obtain complex signal samples; and

a channelizer that processes the complex signal samples to determine energy in each of a plurality of narrow bandwidths corresponding to channels in the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.

15. A multiple-mode cellular radiotelephone according to claim 11 further comprising:

a controller that controls a receiver to tune to a sequence of channel frequencies in the wider one of the at least two cellular radiotelephone standards of different signal bandwidths and to make signal measurements on the sequence of channel frequencies to search for control channels that conform to the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths; and

a signal evaluator that processes the signal measurements to select at least one channel frequency from the sequence of channel frequencies for scanning after selecting the narrower one of the at least two cellular radiotelephone standards of different signal bandwidths.