Channel scanning method and apparatus

• US 6,327,469 B1
• Filed: 12/11/1998
• Issued: 12/04/2001
• Est. Priority Date: 12/11/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gaastra, Lyle A.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Gesesse, Tilahun
• Application Number:
  US09/210,319
• Time in Patent Office: 1,089 Days
• Field of Search: 455/515, 455/434, 455/512, 455/513, 455/525, 455/437, 455/450, 455/552, 455/553, 455/527
• US Class Current: 455/436
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

The channel scanning method and apparatus uses a priority table (500) to determine the action that should be taken by a mobile station (MS) during an idle frame of a traffic channel (TCH) in order to decode the base station identification code (BSIC) of each channel in a reporting table every ten seconds in accordance with GSM specification 05.08. The priority table (500) has channel groups (510, 520, 530, 540, 550, 560) based on the role of the cell relative to the MS, the time elapsed since the cell'"'"'s broadcast channel (BCH) was most recently synchronized, the expected amount of time needed to either detect a frequency burst (FCH) or demodulate a synchronization burst (SCH), the power level of a BCH, and the detected noise level. The priority table is used by a scheduler (600) to aid the MS in efficiently using each idle frame and reducing nonuse of idle frames.

Claims

1. A channel scanning method for prioritizing scanning of broadcast channels (BCHs) in a cellular radiotelephone system having a mobile station (MS) and plurality of base stations comprising the steps of:

detecting a plurality of BCHs transmitted by the plurality of base stations;

selecting a first BCH from the plurality of BCHs;

determining if the MS is synchronized with the first BCH in both a frequency domain and a time domain; and

assigning a first priority to the first BCH if the MS is synchronized with the first BCH in both the frequency domain and the time domain, wherein the first priority is a first verify priority if the MS should enter the verify mode and the first priority is a first search priority if the MS should enter the search mode.

2. A channel scanning method according to claim 1 wherein the step of selecting the first BCH comprises the step of:

choosing a serving cell BCH.

3. A channel scanning method according to claim 1 wherein the step of selecting the first BCH comprises the steps of:

measuring a signal strength for each of the plurality of BCHs; and

choosing a BCH having a highest signal strength.

4. A channel scanning method according to claim 1 wherein the step of assigning a first verify priority comprises the step of:

determining whether a time elapsed since the MS was synchronized with the first BCH in a time domain exceeds a predetermined threshold;

assigning a higher priority if the time elapsed exceeds the predetermined threshold; and

assigning a lower priority if the time elapsed does not exceed the predetermined threshold.

5. A channel scanning method according to claim 1 further comprising the steps of:

selecting a next BCH, different from the first BCH, from the plurality of BCHs;

determining if the MS is synchronized with the next BCH in both the frequency domain and the time domain; and

assigning a first search priority to the next BCH if the MS is not synchronized with the next BCH in both the frequency domain and the time domain.

6. A channel scanning method according to claim 5 further comprising the step of:

assigning a next verify priority to the next BCH if the MS is synchronized with the next BCH in both the frequency domain and the time domain.

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

deciding a highest assigned priority from the first verify priority, the first search priority, and the next verify priority; and

acquiring an acquired BCH associated with the highest assigned priority.

8. A channel scanning method according to claim 7 further comprising the steps of:

detecting a frequency burst (FCH) on the acquired BCH if the highest assigned priority is a search priority; and

demodulating a synchronization burst (SCH) on the acquired BCH if the highest assigned priority is a search priority.

9. A channel scanning method for prioritizing scanning of channels in a cellular communication system comprising the steps of;

selecting a first channel from a plurality of channels;

obtaining first parameters associated with the first channel;

assigning a first priority to the first channel, the first priority selected from a plurality of priorities based on the first parameters, wherein the first priority is a first verify priority if the MS should enter the verify mode and the first priority is a first search priority if the MS should enter the search mode;

selecting the next channel, different from the first channel, from the plurality of channels;

obtaining next parameters associated with the next channel;

assigning a next priority to the next channel, the next priority selected from a plurality of priorities based on the next parameters;

determining which channel is assigned a higher priority; and

acquiring an acquired channel wherein the acquired channel is the channel that is assigned the higher priority.

10. A channel scanning method according to claim 9 further comprising the step of:

synchronizing to the acquired channel in a frequency domain and synchronizing to the acquired channel in a time domain if the higher priority is a predetermined search priority.

11. A channel scanning method according to claim 9 further comprising the step of:

synchronizing to the acquired channel in a frequency domain if the higher priority is a predetermined verify priority.

12. A channel scanning method for assisting a mobile station (MS) to obtain a base station identification code (BSIC) in a Global System for Mobile Communications (GSM) digital cellular system comprising the steps of:

selecting a first broadcast channel (BCH);

determining if the MS should enter a verify mode to decode a synchronization burst (SCH) on the first BCH or if the MS should enter a search mode to detect a frequency burst (FCH) on the first BCH;

assigning a first priority to the first BCH wherein the first priority is a first verify priority if the MS should enter the verify mode and the first priority is a first search priority if the MS should enter the search mode;

selecting a next BCH;

determining if the MS should enter a verify mode to decode an SCH on the next BCH or if the MS should enter a search mode to detect an FCH on the next BCH;

assigning a next priority to the next BCH wherein the next priority is a next verify priority if the MS should enter the verify mode and the next priority is a next search priority if the MS should enter the search mode; and

acquiring a BCH wherein the acquired BCH is the first BCH if the first priority is higher than the next priority and the acquired BCH is the next BCH if the next priority is higher than the first priority.

13. A channel scanning method according to claim 12 further comprising the step of:

detecting an FCH on the acquired BCH and demodulating an SCH on the acquired BCH to obtain a BSIC if the first search priority or the next search priority is assigned to the acquired BCH.

14. A channel scanning method according to claim 12 further comprising the step of:

demodulating an SCH on the acquired BCH to obtain a BSIC if the first verify priority or the next verify priority is assigned to the acquired BCH.

15. A channel scanning apparatus in a mobile station (MS), having a receiver for receiving broadcast channel (BCH) signals from a serving cell base station and at least one neighbor cell base station, comprising;

a call processor, for appointing a priority for a BCH signal, having;

a scheduler for assigning a priority to the BCH signal using a priority table, the priority table having priority entries for BCHs based on at least one parameter, wherein the assigned priority is a verify priority if the MS should enter the verify mode and the assigned priority is a search priority if the MS should enter the search mode;

a digital signal processor (DSP), coupled to the call processor, for varying signal from a variable crystal to acquire the BCH signal; and

a radio frequency (RF) section, coupled to the DSP, for receiving a BCH signal as directed by the DSP.

16. A channel scanning apparatus according to claim 15 wherein the at least one parameter is a signal strength measurement of the BCH signal.

17. A channel scanning apparatus according to claim 15 wherein the at least one parameter is a time elapsed since a most recent synchronization in a time domain of the MS to the BCH signal.

18. A channel scanning apparatus according to claim 15 wherein the at least one parameter is a role of the BCH signal relative to the MS.

19. A channel scanning apparatus according to claim 15 wherein the at least one parameter is a detected noise level of the BCH signal.