U.S. patent application number 12/940988 was filed with the patent office on 2011-05-05 for reestablishment of an rrc connection for an emergency call in an lte network.
This patent application is currently assigned to HTC Corporation. Invention is credited to Chih-Hsiang Wu.
Application Number | 20110105074 12/940988 |
Document ID | / |
Family ID | 43925953 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110105074 |
Kind Code |
A1 |
Wu; Chih-Hsiang |
May 5, 2011 |
REESTABLISHMENT OF AN RRC CONNECTION FOR AN EMERGENCY CALL IN AN
LTE NETWORK
Abstract
A mobile device initiates an RRC connection reestablishment
procedure or a cell update procedure for an emergency call after
experiencing a failure condition in an LTE network environment. The
mobile device establishes an RRC connection with an acceptable cell
to originate an emergency call. The mobile device detects a failure
condition, such as a radio link failure, which disrupts the RRC
connection. The mobile device searches for available cells that it
may reestablish the RRC connection with, but can only find
acceptable cells. The mobile device may initiate an RRC connection
reestablishment procedure with an acceptable cell. The mobile
device may also only attempt to reestablish the RRC connection with
a cell that is part of a PLMN that the original acceptable cell was
also a part of. The mobile device may also enter an RRC_IDLE mode
upon detecting a failure condition.
Inventors: |
Wu; Chih-Hsiang; (Taoyuan
City, TW) |
Assignee: |
HTC Corporation
Taoyuan City
TW
|
Family ID: |
43925953 |
Appl. No.: |
12/940988 |
Filed: |
November 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61258214 |
Nov 5, 2009 |
|
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|
Current U.S.
Class: |
455/404.1 |
Current CPC
Class: |
H04W 4/90 20180201; H04W
76/19 20180201; H04W 76/50 20180201 |
Class at
Publication: |
455/404.1 |
International
Class: |
H04W 4/22 20090101
H04W004/22 |
Claims
1. A method of reestablishing a radio resource control (RRC)
connection, the method performed by a wireless mobile device
configured to communicate wirelessly with a Long Term Evolution
(LTE) or a Universal Mobile Telecommunications System (UMTS)
network employing a wireless communications protocol, the wireless
mobile device comprising a processor, a radio, and a memory, the
method comprising: establishing an RRC connection with a first
acceptable cell of an LTE or UMTS network, wherein the first
acceptable cell supports emergency calls; establishing an emergency
call via the RRC connection; detecting a failure condition in the
RRC connection, wherein the failure condition is one of a radio
link failure, a handover failure, a mobility from Evolved Universal
Terrestrial Radio Access (E-UTRA) failure, an integrity check
failure, or an RRC connection reconfiguration failure; detecting a
second acceptable cell, wherein the second acceptable cell is
either the first acceptable cell or another acceptable cell; and
sending a request to the second acceptable cell to reestablish the
RRC connection without considering sending the request to a
suitable cell.
2. The method of claim 1, wherein the request to the second
acceptable cell to reestablish the RRC connection commences an RRC
connection reestablishment procedure or a cell update
procedure.
3. The method of claim 1, further comprising detecting a suitable
cell, wherein the suitable cell supports emergency calls.
4. The method of claim 1, wherein the second acceptable cell and
the first acceptable cell are different cells, and wherein the
first acceptable cell belongs to a public land mobile network
(PLMN) and the second acceptable cell also belongs to the PLMN.
5. The method of claim 1, further comprising receiving an
indication from the second acceptable cell that it supports
emergency calls.
6. A method of establishing an RRC connection, the method performed
by a wireless mobile device configured to communicate wirelessly
with an LTE or a UMTS network employing a wireless communications
protocol, the wireless mobile device comprising a processor, a
radio, and a memory, the method comprising: establishing a first
RRC connection with a first acceptable cell of an LTE or UMTS
network, wherein the first acceptable cell supports emergency
calls; establishing a first emergency call via the first RRC
connection; detecting a failure condition in the first RRC
connection, wherein the failure condition is one of a radio link
failure, a handover failure, a mobility from E-UTRA failure, an
integrity check failure, or an RRC connection reconfiguration
failure; entering an RRC_IDLE mode upon detecting the failure
condition without waiting for a timer to expire, wherein the timer
is associated with a procedure for reestablishing the RRC
connection; establishing a second RRC connection with a second
cell; and establishing a second emergency call via the second RRC
connection.
7. The method of claim 6, wherein the timer is timer T311 or timer
T305.
8. The method of claim 6, wherein the second emergency call is
established automatically upon establishing the second RRC
connection with the second cell.
9. A method of reestablishing an RRC connection, the method
performed by a wireless mobile device configured to communicate
wirelessly with an LTE or UMTS network employing a wireless
communications protocol, the wireless mobile device comprising a
processor, a radio, and a memory, the method comprising:
establishing an RRC connection with a first cell of an LTE or UMTS
network, wherein the first cell supports emergency calls;
establishing an emergency call via the RRC connection; detecting a
failure condition in the RRC connection, wherein the failure
condition is one of a radio link failure, a handover failure, a
mobility from E-UTRA failure, an integrity check failure, or an RRC
connection reconfiguration failure; searching for a second cell
that either: (i) belongs to a PLMN that the first cell also belongs
to, or (ii) is identified as able to supports emergency calls; and
in response to finding the second cell, sending a request to
reestablish the RRC connection to the second cell.
10. The method of claim 9, further comprising entering an RRC_IDLE
mode when a second cell that belongs to a PLMN that the first cell
also belongs to or that supports emergency calls is not found, but
a suitable cell is found.
11. The method of claim 9, wherein the request to reestablish the
RRC connection commences an RRC connection reestablishment
procedure or a cell update procedure.
12. The method of claim 9, wherein the second cell is either an
acceptable cell or a suitable cell.
13. The method of claim 9, further comprising receiving an
indication from the second cell that it supports emergency
calls.
14. The method of claim 10, further comprising establishing a
second RRC connection with the suitable cell and establishing a
second emergency call via the suitable cell.
15. The method of claim 9, wherein the first cell is an acceptable
cell.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/258,214 filed on Nov. 5, 2009 and titled METHOD
TO HANDLE RRC CONNECTION RECOVERY IN WIRELESS COMMUNICATIONS
SYSTEM, which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] In an emergency, a person's mobile device (i.e., user
equipment (UE)) is often his or her lifeline for help. This
dependence makes it crucial that the mobile device be able to
establish emergency calls (e.g., to 9-1-1) whenever necessary. To
this end, mobile devices are generally allowed to establish
emergency calls through cells of wireless networks that they are
not authorized to use for normal service.
[0003] In a Long Term Evolution (LTE) or Universal Mobile
Telecommunications System (UMTS) radio network, a mobile device
establishes a radio resource control (RRC) connection through a
cell to use network services. The mobile device can camp on a
suitable cell to obtain normal service. The mobile device can camp
on an acceptable cell only to originate emergency calls (e.g., a
circuit switched (CS) or an Internet Protocol Multimedia Subsystem
(IMS) emergency call) and receive Earthquake and Tsunami Warning
System (ETWS) and Commercial Mobile Alert System (CMAS)
notifications. As a result, a mobile device establishes an
emergency call through either a suitable cell or an acceptable
cell.
[0004] Like any other call, emergency calls can be disrupted by
failure conditions that interrupt the RRC connection. Failure
conditions may include radio link failures, handover failures,
mobility from evolved Universal Mobile Telecommunications System
(UMTS) Terrestrial Radio Access (e-UTRA) failures, integrity check
failures, RRC connection reconfiguration failures, or other
failures. To continue the emergency call after a failure condition,
the mobile device can perform an RRC connection reestablishment
procedure in an LTE network or a cell update procedure in a UMTS
network. Existing mobile devices operating in an LTE or UMTS
network with an established emergency call via an RRC connection
often struggle to reestablish the RRC connection once it
experiences a failure condition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a system diagram illustrating a representative LTE
network environment for implementing aspects of the invention.
[0006] FIG. 2 is a block diagram illustrating a mobile device.
[0007] FIG. 3 is a flow diagram depicting an example of a routine
to reestablish an RRC connection for an emergency call after a
failure condition is detected.
[0008] FIG. 4 is a flow diagram depicting an example of a routine
to establish an RRC connection for an emergency call after a
failure condition is detected.
[0009] FIG. 5 is a flow diagram depicting an example of a routine
to reestablish an RRC connection for an emergency call after a
failure condition is detected.
[0010] FIG. 6 is a flow diagram depicting an example of a routine
to reestablish an RRC connection for an emergency call after a
failure condition is detected.
DETAILED DESCRIPTION
Overview
[0011] The present disclosure is directed to reestablishing an RRC
connection that was established for an emergency call in an LTE or
a UMTS network environment. As discussed below, the mobile device
initiates an RRC connection reestablishment procedure or a cell
update procedure when it detects a failure condition, such as a
radio link failure, a handover failure, etc. Although embodiments
of the disclosure discuss the reestablishment of an RRC connection
with respect to an RRC connection reestablishment procedure, it
will be appreciated that in a UMTS network environment, a cell
update procedure may be used.
[0012] In some implementations, the mobile device has an emergency
call connected via an RRC connection established with an acceptable
cell. The mobile device detects a failure condition and searches
for available cells with which to reestablish the RRC connection.
If a suitable cell is detected, the mobile device commences an RRC
reestablishment procedure with the suitable cell. If no suitable
cell is found, but the mobile device detects an acceptable cell,
the mobile device initiates an RRC reestablishment procedure with a
detected acceptable cell. In some implementations, the mobile
device initiates an RRC connection reestablishment procedure with
an acceptable cell regardless of whether it also finds a suitable
cell.
[0013] In some implementations, the mobile device has an emergency
call connected via an RRC connection established with an acceptable
cell. The mobile device detects a failure condition and immediately
enters an RRC_IDLE state. The mobile device does not initiate an
RRC connection reestablishment procedure. Instead, the mobile
device can originate another emergency call without having to wait
for a timer (T311 in e-UTRAN or T305 in UTRAN) to expire while it
searches for a suitable cell to connect with.
[0014] In some implementations, the mobile device has an emergency
call connected via an RRC connection established with an acceptable
cell. The mobile device detects a failure condition and searches
for available cells with which it can commence an RRC connection
reestablishment procedure. If the mobile device finds a cell that
belongs to a public land mobile network (PLMN) that the original
acceptable cell belongs to, the mobile device initiates an RRC
connection reestablishment procedure with that cell. In some
implementations, if the mobile device finds a suitable cell that
does not belong to a PLMN that the original acceptable cell belongs
to, the mobile device enters an RRC_IDLE mode and subsequently
requests that a new RRC connection be established with the suitable
cell.
[0015] In some implementations, the mobile device has an emergency
call connected via an RRC connection established with a cell. The
mobile device detects a failure condition and searches for a cell
that supports emergency calls that the mobile device can
reestablish the RRC connection with. If the mobile device finds
such a cell, it initiates an RRC connection reestablishment
procedure with that cell.
[0016] Various examples of the invention will now be described. The
following description provides specific details for a thorough
understanding and enabling description of these examples. One
skilled in the relevant art will understand, however, that the
invention may be practiced without many of these details. Likewise,
one skilled in the relevant art will also understand that the
invention can include many other obvious features not described in
detail herein. Additionally, some well-known structures or
functions may not be shown or described in detail below, so as to
avoid unnecessarily obscuring the relevant description.
[0017] The terminology used below is to be interpreted in its
broadest reasonable manner, even though it is being used in
conjunction with a detailed description of certain specific
examples of the invention. Indeed, certain terms may even be
emphasized below; however, any terminology intended to be
interpreted in any restricted manner will be overtly and
specifically defined as such in this Detailed Description
section.
System Description
[0018] The following discussion provides a brief, general
description of a representative environment in which the invention
can be implemented. Although not required, aspects of the invention
may be described below in the general context of
computer-executable instructions, such as routines executed by a
general-purpose data processing device (e.g., a server computer, a
personal computer, or a mobile/portable device). Those skilled in
the relevant art will appreciate that the invention can be
practiced with other communications, data processing, or computer
system configurations, including wireless devices, Internet
appliances, hand-held devices (including personal digital
assistants (PDAs)), wearable computers, tablet computers, netbook
computers, all manner of cellular or mobile phones, multi-processor
systems, microprocessor-based or programmable consumer electronics,
set-top boxes, network PCs, mini-computers, mainframe computers,
and the like. Indeed, "mobile device" as used herein may refer to
any of the above devices and systems.
[0019] While aspects of the invention, such as certain functions,
are described as being performed exclusively on a single device,
the invention can also be practiced in distributed environments
where functions or modules are shared among disparate processing
devices.
[0020] Aspects of the invention may be stored or distributed on
tangible computer-readable media, including magnetically or
optically readable computer discs, hard-wired or preprogrammed
chips (e.g., EEPROM semiconductor chips), nanotechnology memory,
biological memory, or other data storage media. Alternatively,
computer implemented instructions, data structures, screen
displays, and other data related to the invention may be
distributed over the Internet or over other networks (including
wireless networks), on a propagated signal on a propagation medium
(e.g., an electromagnetic wave(s), a sound wave, etc.) over a
period of time. In some implementations, the data may be provided
on any analog or digital network (packet switched, circuit
switched, or other scheme).
[0021] As shown in the example of FIG. 1, mobile devices 104, 106,
such as a cellular phone, may wirelessly communicate with one or
more cells of a cell tower 108 coupled to a network 110. In some
implementations, the network 110 is an LTE network. In other
implementations, the network 110 is a UTRAN network. The term
"mobile device," as used herein, may be a cell phone, a personal
digital assistant (PDA), a portable email device (e.g., a
Blackberry.RTM. device), a portable media player (e.g., an Apple
iPod Touch.RTM.), a tablet or slate computer (e.g., an Apple
iPad.RTM.), a netbook computer, a notebook computer, an e-reader,
or any other device having wireless communication capability. The
network 110 may be an IP-based telecommunications network, and
communication between the cell tower 108 and the mobile devices
104, 106 may be based, for example, on e-UTRAN or UTRAN, utilizing,
for example, orthogonal frequency-division multiple access (OFDMA)
and single-carrier frequency-division multiple access
(SC-FDMA).
[0022] As mentioned earlier, the network 110 communicates with the
mobile devices 104, 106 via a cell of the cell tower 108. The cell
tower may be a cellular transceiver or base station antenna. In
some implementations, the cell is a femtocell or a hybrid of a
macro cell and femtocell. In some implementations, a cell of the
cell tower 108 is part of a single PLMN, while in other
implementations, a cell of the cell tower 108 is part of multiple
PLMNs.
[0023] Although the mobile devices 104, 106 are generally described
in the examples provided below, aspects of the invention apply
equally to any communication device, such as a laptop, or a more
stationary computing device, such as a personal desktop computer,
or another device, such as a television, set-top box, electronic
picture frame, electronic reading device, etc.
Mobile
[0024] FIG. 2 is a block diagram of the mobile device 104 or 106
according to some implementations. The mobile device 104, 106
includes one or more wireless transceivers or radios 210, a memory
and firmware 212, input components 214, and output components 215,
which all communicate with one or more processors 216. The input
components 214 of the mobile device 104, 106 may include a
microphone, user input buttons (physical or via a touch screen), a
global positioning system (GPS), a digital camera, a wireless LAN
(WiFi) interface, a motion sensor, a Bluetooth.RTM. interface, a
USB or similar port, and so forth. The output components 215 may
include a speaker, headphone or headset jack adapter, visual
display, and haptic output device (e.g., a vibrator), as well as
the communication elements noted above as input components. For
example, the BlueTooth.RTM. interface may communicate with an
external wireless communications component, such as a wireless
headset, to not only receive audio input but also provide audio
output.
[0025] The communication component can include a radio implementing
wireless standards such as LTE, UMTS, Global System for Mobile
Communications (GSM), or CDMA 2000, as well as a WLAN, and/or a
personal area network (PAN) radio, such as one employing IEEE
802.11, Bluetooth or other wireless standards. The processors in
the mobile device 104, 106 can include components for facilitating
voice and data calls, processing images, and executing firmware, as
well as processors for performing actions described herein. Indeed,
as an alternative, or in addition to the processor(s), the mobile
device 104, 106 may include one or more digital signal processors
(DSPs), application-specific integrated circuits (ASICs), field
programmable gate arrays (FPGAs), or other logic/data processing
circuitry.
[0026] In some instances, the mobile device 104, 106 may include a
removable card slot to receive a Subscriber Identity Module (SIM)
and/or a removable memory card 218 that may itself include a
processor, memory, radio, etc. The removable memory card is
received within a card slot of the mobile, and can be of a form and
shape common to any known cards, such as SD cards, xD cards, PCMCIA
cards, etc. Further, the mobile may include other memory, such as a
cache memory for temporarily storing information.
[0027] The mobile device 104, 106 includes an operating system
(OS), which is resident in the memory 212 and which is executed by
the processor 216. One or more application programs may be loaded
into the memory 212 and are run by or in conjunction with the OS.
Examples of application programs include conventional phone
application programs, such as address book/phonebook/contacts
programs, as well as game programs, navigation programs,
installation wizard programs, customer care applications, email
programs, scheduling programs, PIM (personal information
management) programs, word processing programs, spreadsheet
programs, Internet web browser programs, games, media playback
programs, etc. Any application program or the OS can be provisioned
according to implementations of the invention.
[0028] The memory 212 can include an RRC connection reestablishment
module 220. The RRC connection reestablishment module 220 contains
data and instructions for reestablishing an RRC connection
according to implementations of the present disclosure. For
example, the RRC connection reestablishment module 220 includes
instructions for reestablishing an RRC connection after the mobile
device detects a failure condition according to the routines
discussed below with reference to FIGS. 3-6.
[0029] The mobile device 104, 106 also includes a power supply 217,
which can be implemented as one or more batteries. The power supply
217 may further include an external power source, such as an AC
adapter or a powered docking cradle for supplementing or recharging
the batteries. Of course, other power supplies may be employed,
such as solar cells, transducers for generating electricity for
motion, fuel cells, bioelectric or temperature transducers designed
to generate electricity and store it in a rechargeable
battery/capacitor, and so forth.
[0030] While various components, features, and functions of the
mobile device 104, 106 have been described in the implementation
illustrated in FIG. 2, it should be understood that numerous other
configurations, components, features, and the like may be
incorporated into the mobile devices described herein, and that the
implementations described herein are not limited to any particular
configuration for the mobile devices.
Reestablishing an RRC Connection
[0031] In an LTE or UMTS network environment, a mobile device
establishes an RRC connection with an acceptable cell or a suitable
cell for an emergency call. If a failure condition disrupts the RRC
connection, the emergency call will be terminated. In order to
continue the emergency call after a failure condition, the mobile
device can reestablish the RRC connection. However, existing mobile
devices operating in an LTE network may not be able to recover the
RRC connection for a variety of reasons. The following example
scenarios illustrate typical problems.
[0032] (1) A mobile device detects a failure condition during an
emergency call established through a first acceptable cell. The
mobile device cannot reestablish an RRC connection in an LTE or
UMTS network environment if it can only find the first acceptable
cell or a second acceptable cell to connect to. Instead, the mobile
device searches for a suitable cell to connect to.
[0033] (2) A mobile device detects a failure condition during an
emergency call established through a first acceptable cell. As in
the previous scenario, the mobile device can only find the first
acceptable cell and/or a second acceptable cell to connect to. The
mobile device searches for a suitable cell until a timer (e.g.,
T311 or T305) expires. The mobile device cannot establish a new
emergency call while the timer is running.
[0034] (3) A mobile device detects a failure condition during an
emergency call established through an acceptable cell. The mobile
device searches for and finds a suitable cell to connect to and
attempts to reestablish the RRC connection with the suitable cell.
If the suitable cell and the acceptable cell that the emergency
call was established through belong to different PLMNs, the
reestablishment procedure can fail.
[0035] (4) A mobile device detects a failure condition during an
emergency call. It searches for and finds a suitable cell and
reestablishes an RRC connection through that suitable cell.
However, if the suitable cell does not support emergency calls, the
mobile device may nevertheless remain camped on the suitable cell,
unable to end the failed emergency call.
[0036] In the first scenario, the mobile device has an RRC
connection established with an acceptable cell and experiences a
failure event (e.g., a radio link failure, a handover failure,
etc.), and finds only the acceptable cell or another acceptable
cell available for reestablishing the RRC connection with. FIG. 3
is a flow diagram depicting an example of a routine 300 performed
by the mobile device 104, 106 to reestablish an RRC connection
under such a scenario.
[0037] At a block 305, the mobile device 104, 106 maintains an
emergency call via an RRC connection established with an acceptable
cell. For example, a user of the mobile device may have prompted
the emergency call by dialing 9-1-1, and the mobile device may have
searched for available cells that could support the emergency call
and found only the acceptable cell, which it established the RRC
connection with.
[0038] At a decision block 310, the mobile device determines
whether it has detected a failure condition that disrupts the RRC
connection, and hence, the emergency call. If the mobile device has
not detected a failure condition, the process returns to block 305.
If the mobile device has detected a failure condition, at a block
312, the mobile device searches for a cell with which to
reestablish the RRC connection. For example, the mobile device may
search for a cell by detecting and analyzing radio signals
broadcast by cells within a certain vicinity of the mobile
device.
[0039] At a decision block 315, the mobile device determines
whether it detected a suitable cell. The mobile device can
determine whether a detected cell is a suitable cell or an
acceptable cell by analyzing radio signals sent by the detected
cell, which identify the cell and/or the services that it offers
for the mobile device. If the mobile device did detect a suitable
cell, at a block 320, the mobile device sends a request to the
suitable cell to reestablish the RRC connection. The mobile device
may send an RRCConnection-ReestablishmentRequest message to a
detected suitable cell to attempt to reestablish the RRC connection
with the suitable cell. After sending the reestablishment request
to the suitable cell, the mobile device executes an RRC connection
reestablishment procedure with the suitable cell.
[0040] If at decision block 315 the mobile device did not detect a
suitable cell, at a decision block 325, the mobile device
determines whether it detected an acceptable cell. If it does not
detect an acceptable cell, the routine 300 ends. If at block 325,
the mobile device determines that it did detect an acceptable cell,
at a block 330, the mobile device sends a request to a detected
acceptable cell to reestablish the RRC connection. As mentioned
before, this may be the acceptable cell that the mobile device
originally established an RRC connection with. After requesting
that the RRC connection be reestablished, the mobile device
executes an RRC connection reestablishment procedure or a cell
update procedure through the acceptable cell.
[0041] In practice, the mobile device treats the acceptable cell as
if it were a suitable cell. Existing mobile devices would continue
searching for a suitable cell despite an apparent emergency
situation and an available acceptable cell. In some
implementations, the mobile device does not decide whether a
suitable cell is available first before sending an RRC
reestablishment request to an acceptable cell. Rather, the mobile
device sends an RRC reestablishment request to the acceptable cell
if it is detected. In some implementations, the mobile device sends
an RRC reestablishment request to an acceptable cell despite also
finding a suitable cell. In some implementations, the mobile device
receives system information from at least one of the found cells,
and the system information indicates that the cell supports
emergency calls. Consequently, the mobile device sends the RRC
connection reestablishment request to the cell that supports
emergency calls. In some implementations, the acceptable cell that
the RRC connection was originally established with and the
acceptable cell that the RRC connection is reestablished with
belong to a same PLMN. In some implementations, the acceptable
cells each belong to one PLMN, and in other implementations, at
least one of the acceptable cells belongs to multiple PLMNs. When
the acceptable cells belong to multiple PLMNs, the mobile device
may be configured to only attempt to reestablish the RRC connection
with an acceptable cell that belongs to a PLMN that the original
acceptable cell belongs to.
[0042] FIG. 4 is a flow diagram depicting an example of a routine
400 performed by the mobile device 104, 106 to establish a new RRC
connection once the mobile device detects a failure condition for
an existing RRC connection. At a block 405, the mobile device 104,
106 maintains an emergency call via an RRC connection established
with an acceptable cell. At a decision block 410, the mobile device
determines whether it has detected a failure condition. If the
mobile device has not detected a failure condition, the process
returns to block 405. If the mobile device has detected a failure
condition, at a block 415, the mobile device enters an RRC_IDLE
state. Entering the RRC_IDLE state allows the mobile device to
originate a subsequent emergency call without having to wait for a
timer (e.g., T311 or T305) to expire. This can be important in an
emergency situation, when it is more likely that time is of the
essence. After entering the RRC_IDLE state, the mobile device does
not initiate an RRC connection reestablishment procedure. At a
block 420, the mobile device searches for a cell (acceptable or
suitable) to establish a new RRC connection with. At a decision
block 425, the mobile device determines whether a cell was found
(acceptable or suitable). If no cell was found, the process 400
ends. If a cell was found, at a block 430, the mobile device 104,
106 sends a request to establish an RRC connection with a cell
found at block 420. Once the RRC connection is established, the
mobile device can originate an emergency call. In some
implementations, the mobile device originates an emergency call
immediately upon establishing an RRC connection.
[0043] FIG. 5 is a flow diagram depicting an example of a routine
500 performed by the mobile device 104, 106 to reestablish an RRC
connection once the mobile device detects a failure condition. At a
block 505, the mobile device 104, 106 maintains an emergency call
via an RRC connection established with an acceptable cell. At a
decision block 510, the mobile device determines whether it has
detected a failure condition. If the mobile device has not detected
a failure condition, the process returns to block 505. If the
mobile device has detected a failure condition, at a block 515, the
mobile device searches for a cell that belongs to a PLMN that the
acceptable cell that the RRC connection was previously established
with belongs to. The mobile device can search for such a cell by
analyzing radio signals sent by proximate cells. For example, cells
can broadcast which PLMN they belong to, or the mobile device can
request this information from detected cells.
[0044] At decision block 520, the mobile device determines whether
a cell was found that belongs to a PLMN that the original cell also
belongs to. If no such cell was found, at a decision block 525, the
mobile device determines whether a suitable cell was found that
does not belong to a PLMN that the original cell belongs to. If
such a cell was found, at a block 530, the mobile device enters an
RRC_IDLE mode and subsequently sends a request to the suitable cell
to establish an RRC connection with the cell, which is then
established with the cell. If no suitable cell was found, at a
block 535, the mobile device continues to search for an acceptable
cell or a suitable cell that it can establish the RRC connection
with until a timer (e.g., timer T311) expires. In some
implementations, the mobile device may not reestablish an RRC
connection with an acceptable cell that does not belong to a PLMN
that the original cell belongs to.
[0045] If at a decision block 520, the mobile device determines
that a cell was found that belongs to the same PLMN as the original
cell, at a block 540, the mobile device sends a request to
reestablish the RRC connection to that cell. The cell can be either
an acceptable cell or a suitable cell. The request to reestablish
the RRC connection can commence, for example, an RRC connection
reestablishment procedure or a cell update procedure. In some
implementations, the mobile device selects a cell to reestablish
the RRC connection with because the cell supports emergency calls.
For example, a cell may send signals to the mobile device
indicating its ability to support emergency calls, and the mobile
device selects the cell at least in part because it supports
emergency calls.
[0046] FIG. 6 is a flow diagram depicting an example of a routine
600 performed by the mobile device 104, 106 to reestablish an RRC
connection once the mobile device detects a failure condition. At a
block 605, the mobile device 104, 106 maintains an emergency call
via an RRC connection established with a cell. At a decision block
610, the mobile device determines whether it has detected a failure
condition.
[0047] If the mobile device has not detected a failure condition,
the process returns to block 605. If the mobile device has detected
a failure condition, at a block 615 the mobile device searches for
a cell that supports emergency calls that it can establish an RRC
connection with. For example, the mobile device can search for such
cells by analyzing radio signals sent by proximate cells.
[0048] At a decision block 620, the mobile device determines
whether it has found a cell that supports emergency calls. The
mobile device can determine whether a cell supports emergency calls
using the signals sent to the mobile device by the proximate cells
and/or by examining data related to the cell, such as its system
information. If the mobile device does not find a cell that
supports emergency calls, the routine 600 ends. If the mobile
device does find a cell that supports emergency calls, at a block
625, the mobile device sends a request to reestablish the RRC
connection to that cell, initiating an RRC connection
reestablishment procedure or a cell update procedure.
CONCLUSION
[0049] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense, as opposed
to an exclusive or exhaustive sense; that is to say, in the sense
of "including, but not limited to." As used herein, the terms
"connected," "coupled," or any variant thereof mean any connection
or coupling, either direct or indirect, between two or more
elements; the coupling or connection between the elements can be
physical, logical, or a combination thereof. Additionally, the
words "herein," "above," "below," and words of similar import, when
used in this application, refer to this application as a whole and
not to any particular portions of this application. Where the
context permits, words in the above Detailed Description using the
singular or plural number may also include the plural or singular
number, respectively. The word "or," in reference to a list of two
or more items, covers all of the following interpretations of the
word: any of the items in the list, all of the items in the list,
and any combination of the items in the list.
[0050] The above Detailed Description of examples of the invention
is not intended to be exhaustive or to limit the invention to the
precise form disclosed above. While specific examples for the
invention are described above for illustrative purposes, various
equivalent modifications are possible within the scope of the
invention, as those skilled in the relevant art will recognize. For
example, while processes, elements, or blocks are presented in a
given order or arrangement, alternative implementations may perform
routines having steps, or employ systems having blocks or elements,
in a different order or arrangement, and some processes or blocks
may be deleted, moved, added, subdivided, combined, and/or modified
to provide alternative combinations or subcombinations. Each of
these processes or blocks may be implemented in a variety of
different ways. Also, while processes or blocks are at times shown
as being performed in series, these processes or blocks may instead
be performed or implemented in parallel, or may be performed at
different times. Further, any specific numbers noted herein are
only examples: alternative implementations may employ differing
values or ranges.
[0051] The teachings of the invention provided herein can be
applied to other systems, not necessarily the system described
above. The elements and acts of the various examples described
above can be combined to provide further implementations of the
invention. Some alternative implementations of the invention may
include not only additional elements to those implementations noted
above, but also may include fewer elements.
[0052] Any patents and applications and other references noted
above, including any that may be listed in accompanying filing
papers, are incorporated herein by reference. Aspects of the
invention can be modified, if necessary, to employ the systems,
functions, and concepts of the various references described above
to provide yet further implementations of the invention.
[0053] These and other changes can be made to the invention in
light of the above Detailed Description. While the above
description describes certain examples of the invention, and
describes the best mode contemplated, no matter how detailed the
above appears in text, the invention can be practiced in many ways.
Details of the system may vary considerably in their specific
implementation, while still being encompassed by the invention
disclosed herein. As noted above, particular terminology used when
describing certain features or aspects of the invention should not
be taken to imply that the terminology is being redefined herein to
be restricted to any specific characteristics, features, or aspects
of the invention with which that terminology is associated. In
general, the terms used in the following claims should not be
construed to limit the invention to the specific examples disclosed
in the specification, unless the above Detailed Description section
explicitly defines such terms. Accordingly, the actual scope of the
invention encompasses not only the disclosed examples, but also all
equivalent ways of practicing or implementing the invention under
the claims.
[0054] To reduce the number of claims, certain aspects of the
invention are presented below in certain claim forms, but the
applicant contemplates the various aspects of the invention in any
number of claim forms. For example, while only one aspect of the
invention is recited as a means-plus-function claim under 35 U.S.C
sec. 112, sixth paragraph, other aspects may likewise be embodied
as a means-plus-function claim, or in other forms, such as being
embodied in a computer-readable medium. (Any claims intended to be
treated under 35 U.S.C. .sctn.112, 6 will begin with the words
"means for," but use of the term "for" in any other context is not
intended to invoke treatment under 35 U.S.C. .sctn.112, 6.)
Accordingly, the applicant reserves the right to pursue additional
claims after filing this application to pursue such additional
claim forms, in either this application or in a continuing
application.
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