Reestablishment procedure for an emergency call

Abstract

Traditional rules that apply to cell selection are overridden to allow cell selection on an acceptable cell, in addition to cell selection on a suitable cell. Once a mobile device acquires service on an acceptable cell, mobile device can inform network of the emergency call in progress or initiation of an emergency call, which allows network to perform necessary actions to support the emergency call during establishment / reestablishment.

Description

CROSS-REFERENCE[0001]This is a divisional application of U.S. patent application Ser. No. 12 / 752,577 entitled REESTABLISHMENT PROCEDURE FOR AN EMERGENCY CALL, filed Apr. 1, 2010, assigned U.S. Pat. No. 8,831,555 with an issue date of Sep. 9, 2014, which claims priority to Provisional Application No. 61 / 166,629 entitled METHOD AND APPARATUS TO ENABLE RE-ESTABLISHMENT PROCEDURES FOR EMERGENCY CALLS, filed Apr. 3, 2009, both assigned to the assignee hereof and hereby expressly incorporated by reference herein.BACKGROUND[0002]I. Field[0003]The following description relates generally to wireless communications and more particularly to reestablishment procedures in a wireless communications environment.[0004]II. Background[0005]Wireless communication systems are widely deployed to provide various types of communication content, such as voice, data, video, and so forth, and to communicate information regardless of where a user is located (e.g., inside or outside a structure) and whether a ...

AI Technical Summary

Benefits of technology

The patent describes a method and apparatus for reestablishing connections in a wireless communication system in case of radio link failure. The technical effects of the patent include improved reliability and resilience in emergency calls, faster recovery of lost connections, and better utilization of available network resources. The method involves detecting a radio link failure and determining if the mobile device is making an emergency call, and then either reestablishing the connection on the same cell or identifying an acceptable cell for the mobile device to connect to. The apparatus includes a memory and processor for executing the method.

Problems solved by technology

According to traditional procedures, mobile device can only select a suitable E-UTRA cell for reestablishment.

However, when there is an emergency call, mobile device might encounter the situation where no suitable E-UTRA cell is present, but there is an acceptable E-UTRA cell (which is a cell where mobile device can obtain emergency services (only)).

Therefore, since mobile device finds no cell on which reestablishment is allowed, mobile device goes to idle mode and the call needs to be reinitiated by the mobile device user, which is an undesirable result in the case of an emergency call.

If an acceptable cell is the only cell available to mobile device, the delay before mobile device enters idle mode can be significant.

However, searching all frequencies of all RATs may take a long time in the case of a mobile device supporting many technologies.

In an example, a maximum value of a reestablishment timer can be about 30 seconds, which, in an emergency situation, can be an extremely long time.

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