System and method for edge of coverage detection in a wireless communication device

• US 6,363,260 B1
• Filed: 07/07/1999
• Issued: 03/26/2002
• Est. Priority Date: 07/07/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ahsan, Syed N., Hughes, Robbin, Achour, Baaziz, Usmani, Farrukh
• Primary Examiner(s): To, Doris H.
• Assistant Examiner(s): RAMOS FELICIANO, ELISEO
• Application Number:
  US09/348,442
• Time in Patent Office: 993 Days
• Field of Search: 455/552, 455/553, 455/513, 455/437, 455/450-454, 455/422, 455/434, 455/436, 455/432, 455/512, 455/67.1, 455/296, 455/426, 455/515
• US Class Current: 455/553.1
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• 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

A method to enhance performance of a dual-mode or dual-band mobile phone includes, after the phone has initially connected to a CDMA wireless network, monitoring a level of total power received by the phone. This power level is compared to a preset threshold level. If the power level remains below the threshold level for over two seconds, the dual-mode or dual-band phone switches to an AMPS or other network retrieved from the preferred roaming list that is stored in the phone. If the power level is above the threshold, the phone moves into the idle state. Once in the idle state, both the pilot strength and Received Signal Strength Indication are monitored. If both of these levels are below respective thresholds for over eight seconds, the phone switches to another network stored in the preferred roaming list. If the mobile phone is not a dual-mode or dual-band phone, the mobile phone can perform similar measurements and switch between service provider systems compatible with the mobile phone.

Claims

1. In a wireless telephone communication system having more than one service provider system, a method to enhance performance of a mobile phone, comprising:

when the mobile phone that is communicating with a first service provider system is in an idle mode, monitoring a first performance level and a second performance level;

if the first performance level falls below a first threshold and the second performance level falls below a second threshold, starting a timer;

if, while the timer is running, either the first or second performance levels exceed their respective thresholds, resetting the timer and continue monitoring the first and second performance levels; and

if the timer exceeds a predetermined duration, switching the mobile telephone from the first service provider system to a second service provider system.

2. The wireless communication system of claim 1 wherein the first performance level is pilot strength.

3. The method of claim 1 wherein the second performance level is a received signal strength indication.

4. The method of claim 1 wherein both the first and second service provider systems are CDMA digital service provider systems.

5. The method of claim 1 wherein the first service provider system is a CDMA digital service provider system and wherein the second service provider system is an AMPS cellular service provider system.

6. The method of claim 1 wherein the switching comprises:

retrieving a frequency from a list of alternate service provider systems;

disconnecting the mobile phone from the first service provider system; and

connecting the mobile phone to the second service provider system operating at the frequency retrieved from the list of alternate service provider systems.

7. The method of claim 6 wherein the list of alternate service provider systems is stored within the mobile phone.

8. A wireless telephone comprising:

a signal detector structured to receive and measure a first performance level of communication signals after the telephone has connected to a first service provider system;

a signal comparator structured to compare the first performance level with a first threshold level;

a timer that begins when the first performance level is below the first threshold level and expires a preselected time period after it begins;

a system determinator structured to determine a second service provider system for the wireless telephone to connect to when the timer expires;

a second signal detector structured to receive and measure a second performance level of communication signals; and

a second signal comparator structured to compare the second performance level with a second threshold level;

wherein the timer begins when both the first performance level is below the first threshold level and when the second performance level is below the second threshold level.

9. The wireless telephone of claim 8 wherein the signal detector detects total power received by the wireless telephone.

10. The wireless telephone of claim 8 wherein the first service provider system is a CDMA digital service provider system and the first threshold level used by the signal comparator is −

107 dBm for cellular and −

105 dBm for PCS.

11. The wireless telephone of claim 8 wherein the timer expires 2 seconds after it begins.

12. The wireless telephone of claim 8, further comprising a preferred roaming list containing operational frequencies of a plurality of possible service provider systems, the system determinator selecting an operational frequency of the second service provider system from the preferred roaming list and disconnecting the wireless telephone from the first service provider system and connecting the wireless telephone to the second service provider system operating at the frequency selected from the preferred roaming list.

13. The wireless telephone of claim 12 wherein the wireless preferred roaming list is stored within the wireless telephone.

14. The wireless telephone of claim 8 wherein the wireless telephone is a dual-mode or dual-band telephone.

15. The wireless telephone of claim 8 wherein the signal detector measures pilot strength.

16. The wireless telephone of claim 8 wherein the second signal detector measures pilot received power.