Multi-RAT Wireless Communication

Abstract

A wireless communication device uses a first radio access technology (RAT) module and a second RAT module to perform functions relating to a first RAT and a second RAT, respectively. The wireless communication device uses the second RAT module, while the first RAT module is in a reduced power state, to perform a portion of a random access procedure to access the first RAT. The wireless communication device then wakes the first RAT module from the reduced power state and uses the first RAT module to complete the random access procedure to access the first RAT.

What is claimed is: 
     
         1 . A method, performed by a wireless communication device, the method comprising:
 using a first radio access technology (RAT) module and a second RAT module to perform functions relating to a first RAT and a second RAT, respectively;   using the second RAT module, while the first RAT module is in a reduced power state, to perform a portion of a random access procedure to access the first RAT;   waking the first RAT module from the reduced power state and using the first RAT module to complete the random access procedure to access the first RAT.   
     
     
         2 . The method of  claim 1 , further comprising using the second RAT module, while the first RAT module is in the reduced power state, to receive system information for the first RAT. 
     
     
         3 . The method of  claim 1 , further comprising using the second RAT module, while the first RAT module is in the reduced power state, to perform signal measurements on the first RAT. 
     
     
         4 . The method of  claim 1 , wherein waking the first RAT module from the reduced power state comprises using the second RAT module to send a control message to the first RAT module. 
     
     
         5 . The method of  claim 1 , further comprising:
 transitioning the first RAT module from a Radio Resource Control (RRC) CONNECTED state to an RRC INACTIVE or RRC SUSPENDED state upon entering the reduced power state; and   transitioning the first RAT module back to the RRC CONNECTED state upon waking from the reduced power state.   
     
     
         6 . The method of  claim 1 , further comprising:
 transitioning the first RAT module from an RRC CONNECTED state to an RRC IDLE state upon entering the reduced power state; and   transitioning the first RAT module back to the RRC CONNECTED state upon waking from the reduced power state.   
     
     
         7 . The method of  claim 1 , further comprising using the second RAT module, while the first RAT module is in the reduced power state, to perform paging operations for the first RAT. 
     
     
         8 . The method of  claim 1 , further comprising using the second RAT module, while the first RAT module is in the reduced power state, to exchange user data via the first RAT. 
     
     
         9 . The method of  claim 8 , wherein using the second RAT module to exchange the user data via the first RAT is responsive to an amount of the user data over a defined time period being less than a threshold. 
     
     
         10 . The method of  claim 8 , wherein using the second RAT module to exchange the user data via the first RAT is responsive to user data exchange via the first RAT occurring at a frequency that is less than a threshold. 
     
     
         11 . The method of  claim 8 , wherein using the second RAT module to exchange the user data via the first RAT is responsive to a latency requirement for the user data being less than a threshold. 
     
     
         12 . A wireless communication device comprising:
 a first radio access technology (RAT) circuitry module and a second RAT circuitry module, the first RAT circuitry module being configured to:
 perform functions relating to a first RAT; 
 enter a reduced power state; 
 wake from the reduced power state to complete a random access procedure being performed by the second RAT circuitry module to access the first RAT; and 
   a second RAT circuitry module configured to:
 perform functions relating to a second RAT; and 
 perform at least a portion of the random access procedure to access the first RAT while the first RAT circuitry module is in the reduced power state. 
   
     
     
         13 . The wireless communication device of  claim 12 , wherein the second RAT circuitry module is further configured to receive system information for the first RAT while the first RAT circuitry module is in the reduced power state. 
     
     
         14 . The wireless communication device of  claim 12 , wherein the second RAT circuitry module is further configured to perform signal measurements on the first RAT while the first RAT module is in the reduced power state. 
     
     
         15 . The wireless communication device of  claim 12 , wherein the second RAT circuitry module is further configured to send a control message to the first RAT module to wake the first RAT circuitry module from the reduced power state. 
     
     
         16 . The wireless communication device of  claim 12 , wherein the first RAT circuitry module is further configured to:
 transition from a Radio Resource Control (RRC) CONNECTED state to an RRC INACTIVE or RRC SUSPENDED state upon entering the reduced power state; and   transition back to the RRC CONNECTED state upon waking from the reduced power state.   
     
     
         17 . The wireless communication device of  claim 12 , wherein the first RAT circuitry module is further configured to:
 transition from an RRC CONNECTED state to an RRC IDLE state upon entering the reduced power state; and   transition back to the RRC CONNECTED state upon waking from the reduced power state.   
     
     
         18 . The wireless communication device of  claim 12 , wherein the second RAT circuitry module is further configured to perform paging operations for the first RAT while the first RAT circuitry module is in the reduced power state. 
     
     
         19 . The wireless communication device of  claim 12 , wherein the second RAT circuitry module is further configured to exchange user data via the first RAT while the first RAT module is in the reduced power state. 
     
     
         20 . The wireless communication device of  claim 19 , wherein the second RAT circuitry module is configured to exchange the user data via the first RAT responsive to an amount of the user data over a defined time period being less than a threshold. 
     
     
         21 . The wireless communication device of  claim 19 , wherein the second RAT circuitry module is configured to exchange the user data via the first RAT responsive to user data exchange via the first RAT occurring at a frequency that is less than a threshold. 
     
     
         22 . The wireless communication device of  claim 19 , wherein the second RAT circuitry module is configured to exchange the user data via the first RAT responsive to a latency requirement for the user data being less than a threshold.