Method and Apparatus for Determining Coverage and Switching Between Overlay Communication Systems

Abstract

Techniques to determine whether or not a terminal is under the coverage of a current wireless communication system (e.g., a packet data system) and to switch from the current system to another wireless communication system (e.g., a voice/data system). In one method, at least one measurement of at least one parameter for at least one base station in the current system is initially obtained. The measurement(s) may be SNR measurements. A metric is derived based on the measurement(s) and used (typically along with a metric threshold and a timer) to determine whether or not the terminal is within the coverage of the current system. A switch to another system is initiated if the terminal is deemed to be outside the coverage of the current system. The two systems provide at least one common service (e.g., packet data service).

1 . A method of switching a terminal between overlay communication systems, the method comprising:
 determining one or more switching criteria for switching the terminal between a first wireless communication system and a second wireless communication system;   initiating a switch from the first wireless communication system to the second wireless communication system based on the switching criteria in accordance with a first switching scheme; and   initiating a switch from the second wireless communication system to the first wireless communication system based on the switching criteria in accordance with a second switching scheme different from the first switching scheme.   
   
   
       2 . The method of  claim 1 , wherein the second switching scheme has a lower switch threshold for initiating the switch than the first switching scheme. 
   
   
       3 . The method of  claim 1 , wherein the first wireless communication system is a preferred packet data system with a relatively small coverage area and the second wireless communication system is a voice/data system with a relatively large coverage area. 
   
   
       4 . The method of  claim 3 , wherein the switching criteria comprises a coverage obtained by the terminal, the terminal being switched to the preferred packet data system if it is under the coverage of the preferred packet data system. 
   
   
       5 . The method of  claim 3 , wherein the switching criteria comprises current data requirements of the terminal, the terminal being switched to the preferred packet data system if there is data to send. 
   
   
       6 . The method of  claim 3 , wherein the switching criteria comprises an operating state of the terminal, the terminal being switched to the preferred packet data system if it is in an idle operating state and not currently receiving service. 
   
   
       7 . The method of  claim 1 , wherein a switch is initiated only if at least one base station in the target wireless communication system is received by the terminal with sufficient signal quality. 
   
   
       8 . The method of  claim 1 , wherein the first and second communication systems provide at least one common service. 
   
   
       9 . The method of  claim 8 , wherein the at least one common service includes packet data service. 
   
   
       10 . The method of  claim 1 , wherein the first communication system is an IS-856 system and the second communication system is a cdma2000 system. 
   
   
       11 . A terminal capable of switching between overlay communication systems, the terminal comprising:
 a controller configured to determine one or more switching criteria for switching the terminal between a first wireless communication system and a second wireless communication system, to initiate a switch from the first wireless communication system to the second wireless communication system based on the switching criteria in accordance with a first switching scheme, and to initiate a switch from the second wireless communication system to the first wireless communication system based on the switching criteria in accordance with a second switching scheme different from the first switching scheme; and   a memory coupled to the controller for storing the switching criteria.   
   
   
       12 . The terminal of  claim 11 , wherein the second switching scheme has a lower switch threshold for initiating the switch than the first switching scheme. 
   
   
       13 . The terminal of  claim 11 , wherein the first wireless communication system is a preferred packet data system with a relatively small coverage area and the second wireless communication system is a voice/data system with a relatively large coverage area. 
   
   
       14 . The terminal of  claim 13 , wherein the switching criteria comprises a coverage obtained by the terminal, the terminal being switched to the preferred packet data system if it is under the coverage of the preferred packet data system. 
   
   
       15 . The terminal of  claim 13 , wherein the switching criteria comprises current data requirements of the terminal, the terminal being switched to the preferred packet data system if there is data to send. 
   
   
       16 . The terminal of  claim 13 , wherein the switching criteria comprises an operating state of the terminal, the terminal being switched to the preferred packet data system if it is in an idle operating state and not currently receiving service. 
   
   
       17 . A terminal capable of switching between overlay communication systems, the terminal comprising:
 means for determining one or more switching criteria for switching the terminal between a first wireless communication system and a second wireless communication system;   means for initiating a switch from the first wireless communication system to the second wireless communication system based on the switching criteria in accordance with a first switching scheme; and   means for initiating a switch from the second wireless communication system to the first wireless communication system based on the switching criteria in accordance with a second switching scheme different from the first switching scheme.   
   
   
       18 . The terminal of  claim 17 , wherein the second switching scheme has a lower switch threshold for initiating the switch than the first switching scheme. 
   
   
       19 . The terminal of  claim 17 , wherein the first wireless communication system is a preferred packet data system with a relatively small coverage area and the second wireless communication system is a voice/data system with a relatively large coverage area. 
   
   
       20 . The terminal of  claim 19 , wherein the switching criteria comprises a coverage obtained by the terminal, the terminal being switched to the preferred packet data system if it is under the coverage of the preferred packet data system. 
   
   
       21 . The terminal of  claim 19 , wherein the switching criteria comprises current data requirements of the terminal, the terminal being switched to the preferred packet data system if there is data to send. 
   
   
       22 . The terminal of  claim 19 , wherein the switching criteria comprises an operating state of the terminal, the terminal being switched to the preferred packet data system if it is in an idle operating state and not currently receiving service. 
   
   
       23 . A non-transitory computer-readable medium comprising code, which, when executed by a machine, causes the machine to perform operations for switching a terminal between overlay communication systems, the computer-readable medium comprising:
 code for determining one or more switching criteria for switching the terminal between a first wireless communication system and a second wireless communication system;   code for initiating a switch from the first wireless communication system to the second wireless communication system based on the switching criteria in accordance with a first switching scheme; and   code for initiating a switch from the second wireless communication system to the first wireless communication system based on the switching criteria in accordance with a second switching scheme different from the first switching scheme.   
   
   
       24 . The computer-readable medium of  claim 23 , wherein the second switching scheme has a lower switch threshold for initiating the switch than the first switching scheme. 
   
   
       25 . The computer-readable medium of  claim 23 , wherein the first wireless communication system is a preferred packet data system with a relatively small coverage area and the second wireless communication system is a voice/data system with a relatively large coverage area. 
   
   
       26 . The computer-readable medium of  claim 25 , wherein the switching criteria comprises a coverage obtained by the terminal, the terminal being switched to the preferred packet data system if it is under the coverage of the preferred packet data system. 
   
   
       27 . The computer-readable medium of  claim 25 , wherein the switching criteria comprises current data requirements of the terminal, the terminal being switched to the preferred packet data system if there is data to send. 
   
   
       28 . The computer-readable medium of  claim 25 , wherein the switching criteria comprises an operating state of the terminal, the terminal being switched to the preferred packet data system if it is in an idle operating state and not currently receiving service.