Handling tracking area update reject without extended delay

Abstract

A method, apparatus and computer program product are described for reducing delay when making a network connection between user equipment (UE) and a network node when a tracking area update (TAU) request has been denied during LTE reselection. Following a revised signaling protocol, a UE can avoid activation of a NAS Attach Retry timer and move directly to establishing a connection to the network, reducing the UE communications delay from about eleven seconds to less than one second.

What is claimed is: 
     
       1. A method comprising:
 receiving, at a user equipment, a message received from a network node, the message indicating a radio resource control connection to be released in response to a tracking area update reject; 
 awaiting, at a non-access-stratum layer, a notification from a lower, radio resource control layer, the notification indicating the radio resource control connection release is completed; 
 executing, at the user equipment and in response to the received message, a delay timer; 
 allowing an attach procedure to start, when the delay timer expires; and 
 allowing the attach procedure to start, when the notification from the lower, radio resource control layer is received, the notification bypassing the delay timer in order to allow the attach procedure to start. 
 
     
     
       2. The method of  claim 1 , wherein the attach procedure is executed using an existing connection or a new connection is established using Random Access procedure. 
     
     
       3. The method of  claim 2 , wherein a cause value of Tracking Area Update procedure Reject requires initiation of the attach procedure. 
     
     
       4. The method of  claim 1 , wherein a cause value of the received message is other. 
     
     
       5. An apparatus comprising:
 at least one processor; and 
 at least one memory including computer program code, 
 the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least: 
 receive a message, from a network node, the message indicating a radio resource control connection to be released in response to a tracking area update reject; 
 await, at a non-access-stratum layer, a notification from a lower, radio resource control layer, the notification indicating the radio resource control connection release is completed, the notification enabling a delay in the start of the attach procedure; 
 execute, in response to the received message, a delay timer; 
 allow an attach procedure to start, when the delay timer expires; and 
 allow the attach procedure to start, when the notification from the lower, radio resource control layer is received, the notification bypassing the delay timer in order to allow the attach procedure to start. 
 
     
     
       6. The apparatus of  claim 5 , wherein the attach procedure is executed using an existing connection or a new connection is established using Random Access procedure. 
     
     
       7. The apparatus of  claim 6 , wherein a cause value of Tracking Area Update procedure Reject requires initiation of the attach procedure. 
     
     
       8. The apparatus of  claim 5 , wherein a cause value of the received message is other. 
     
     
       9. The apparatus of  claim 5 , wherein a value, for the bypass timer, is specified by at least one of signaling from network, specification, and user equipment. 
     
     
       10. A computer program product comprising at least one non-transitory computer-readable storage medium having executable computer-readable program code instructions stored therein, the computer-readable program code instructions configured to at least:
 receive a message, at a user equipment from a network node, the message indicating a radio resource control connection to be released in response to a tracking area update reject; 
 await, at a non-access-stratum-layer, a notification from a lower, radio resource control layer, the notification indicating the radio resource control connection release is completed; 
 execute, in response to the received message, a delay timer; 
 allow an attach procedure to start, when the delay timer expires; and 
 allow the attach procedure to start, when the notification from the lower, radio resource control layer is received, the notification bypassing the delay timer in order to allow the attach procedure to start. 
 
     
     
       11. The computer program product of claim 10, wherein the attach procedure is executed using an existing connection or a new connection is established using Random Access procedure. 
     
     
       12. The computer program product of claim 11, wherein a cause value of Tracking Area Update procedure Reject requires initiation of the attach procedure.