U.S. patent application number 12/787391 was filed with the patent office on 2010-12-02 for method and apparatus for handling radio link failure.
Invention is credited to Meng-Hui Ou.
Application Number | 20100302951 12/787391 |
Document ID | / |
Family ID | 42641289 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100302951 |
Kind Code |
A1 |
Ou; Meng-Hui |
December 2, 2010 |
Method and Apparatus for Handling Radio Link Failure
Abstract
A method for handling radio link failure in a user equipment of
a wireless communication system is disclosed. The wireless
communication system supports Carrier Aggregation such that the UE
is able to perform transmission and/or reception through multiple
carriers. The method includes steps of configuring a plurality of
carriers and controlling a timer utilized for detecting the radio
link failure according to a status of a primary carrier within the
plurality of carriers.
Inventors: |
Ou; Meng-Hui; (Taipei City,
TW) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
42641289 |
Appl. No.: |
12/787391 |
Filed: |
May 25, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61180929 |
May 26, 2009 |
|
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Current U.S.
Class: |
370/242 |
Current CPC
Class: |
H04W 72/02 20130101;
H04L 5/0033 20130101; H04W 72/0453 20130101; H04L 5/001 20130101;
H04L 5/0007 20130101; H04L 5/0098 20130101; H04W 72/085 20130101;
H04W 76/34 20180201 |
Class at
Publication: |
370/242 |
International
Class: |
H04L 12/26 20060101
H04L012/26 |
Claims
1. A method for handling radio link failure in a user equipment
(UE) of a wireless communication system, the wireless communication
system supporting Carrier Aggregation (CA) such that the UE is able
to perform transmission and/or reception through multiple carriers,
the method comprising: configuring a plurality of carriers; and
controlling a timer utilized for detecting the radio link failure
according to a status of a primary carrier within the plurality of
carriers.
2. The method of claim 1, wherein controlling the timer according
to the status of the primary carrier within the plurality of
carriers is starting the timer when a radio problem is detected on
the primary carrier.
3. The method of claim 2, wherein the radio problem is detected on
the primary carrier when consecutive out-of-sync situations on the
primary carrier are detected.
4. The method of claim 1, further comprising determining the radio
link failure occurs on the primary carrier upon expiry of the
timer.
5. The method of claim 1, further comprising triggering a
connection re-establishment procedure upon expiry of the timer.
6. The method of claim 1, wherein the wireless communication system
is a Long Term Evolution Advanced (LTE-A) system.
7. A communication device for handling radio link failure in a user
equipment (UE) of a wireless communication system, the wireless
communication system supporting Carrier Aggregation (CA) such that
the UE is able to perform transmission and/or reception through
multiple carriers, the communication device comprising: a processor
for executing a program; and a memory coupled to the processor for
storing the program; wherein the program comprises: configuring a
plurality of carriers; and controlling a timer utilized for
detecting the radio link failure according to a status of a primary
carrier within the plurality of carriers.
8. The communication device of claim 7, wherein controlling the
timer according to the status of the primary carrier within the
plurality of carriers in the program is starting the timer when a
radio problem is detected on the primary carrier.
9. The communication device of claim 8, wherein the radio problem
is detected on the primary carrier when consecutive out-of-sync
situations on the primary carrier are detected.
10. The communication device of claim 7, wherein the program
further comprises determining the radio link failure occurs on the
primary carrier upon expiry of the timer.
11. The communication device of claim 7, wherein the program
further comprises triggering a connection re-establishment
procedure upon expiry of the timer.
12. The communication device of claim 7, wherein the wireless
communication system is a Long Term Evolution Advanced (LTE-A)
system.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/180,929, filed on May 26, 2009 and entitled
"Method and apparatus for improving timing synchronization and
Carrier Aggregation in a wireless communication system", the
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
handling radio link failure, and more particularly, to a method and
apparatus for handling radio link failure in a user equipment of a
wireless communication system, so as to reduce waste of radio
resources, and enhance the system performance.
[0004] 2. Description of the Prior Art
[0005] Long Term Evolution wireless communication system (LTE
system), an advanced high-speed wireless communication system
established upon the 3G mobile telecommunication system, supports
only packet-switched transmission, and tends to implement both
Medium Access Control (MAC) layer and Radio Link Control (RLC)
layer in one single communication site, such as in base stations
(Node Bs) alone rather than in Node Bs and RNC (Radio Network
Controller) respectively, so that the system structure becomes
simple.
[0006] In LTE system, to keep an effective connection between a
user equipment (UE) and a Node B after the connection is
established, the UE triggers a timer T310 if the UE detects a radio
problem, e.g. the UE detects consecutive "out-of-sync" indications
from a physical layer (PHY). If the radio problem is not recovered
before the timer T310 is expired, the UE determines a radio link
failure (RLF) occurs, and triggers a connection re-establishment
procedure, to re-establish a normal connection.
[0007] Therefore, via the RLF detection, the UE can timely trigger
the connection re-establishment procedure, to keep the normal
connection with the Node B. However, to meet future requirements of
all kinds of communication services, the 3rd Generation Partnership
Project (3GPP) has started to work out a next generation of the LTE
system: the LTE Advanced (LTE-A) system. Carrier aggregation (CA),
where two or more component carriers are aggregated, is introduced
into the LTE-A system in order to support wider transmission
bandwidths, e.g. up to 100 MHz and for spectrum aggregation. Using
CA, the network of the LTE-A system provides multiple component
carriers instead of a single carrier for a UE, to establish
multiple links for simultaneously receiving and/or transmitting on
these component carriers.
[0008] At present, the characteristics of CA are quoted as
below:
[0009] (1) Supporting CA for both contiguous and non-contiguous
component carriers.
[0010] (2) It is possible to configure a UE to aggregate a
different number of component carriers in the uplink (UL) and the
downlink (DL), to obtain different bandwidths.
[0011] (3) From a UE perspective, there is one transport block and
one hybrid-ARQ (HARQ) entity per scheduled component carrier.
[0012] As can be seen, a UE with CA configured can utilize multiple
component carriers, and each of the component carriers may have a
different coverage range or radio quality. Thus, a radio problem on
a component carrier does not mean other component carriers are
useless, i.e. other component carriers may work. In such a
situation, triggering the connection re-establishment procedure
seems to be improper and wastes radio resources.
SUMMARY OF THE INVENTION
[0013] It is therefore an objective of the present invention to
provide a method and apparatus for handling radio link failure in a
wireless communication system.
[0014] According to the present invention, a method for handling
radio link failure in a user equipment (UE) of a wireless
communication system is disclosed. The wireless communication
system supports Carrier Aggregation such that the UE is able to
perform transmission and/or reception through multiple carriers.
The method includes steps of configuring a plurality of carriers
and controlling a timer utilized for detecting the radio link
failure according to a status of a primary carrier within the
plurality of carriers.
[0015] According to the present invention, a communication device
for handling radio link failure in a user equipment of a wireless
communication system is disclosed. The wireless communication
system supports Carrier Aggregation such that the UE is able to
perform transmission and/or reception through multiple carriers.
The communication device includes a processor for executing a
program, and a memory coupled to the processor for storing the
program. The program includes steps of configuring a plurality of
carriers, and controlling a timer utilized for detecting the radio
link failure according to a status of a primary carrier within the
plurality of carriers.
[0016] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram of a wireless communications
system.
[0018] FIG. 2 is a function block diagram of a wireless
communications device.
[0019] FIG. 3 is a diagram of a program of FIG. 2.
[0020] FIG. 4 is a flowchart of a process according to an
embodiment of the present invention.
DETAILED DESCRIPTION
[0021] Please refer to FIG. 1, which illustrates a schematic
diagram of a wireless communication system 10. The wireless
communication system 10 is preferably an LTE advanced (LTE-A)
system, and is briefly composed of a network and a plurality of
user equipments (UEs). In FIG. 1, the network and the UEs are
simply utilized for illustrating the structure of the wireless
communication system 10. Practically, the network may comprise a
plurality of base stations (Node Bs), radio network controllers and
so on according to actual demands, and the UEs can be devices such
as mobile phones, computer systems, etc.
[0022] Please refer to FIG. 2, which is a functional block diagram
of a communication device 100 in a wireless communication system.
The communication device 100 can be utilized for realizing the UEs
in FIG. 1. For the sake of brevity, FIG. 2 only shows an input
device 102, an output device 104, a control circuit 106, a central
processing unit (CPU) 108, a memory 110, a program 112, and a
transceiver 114 of the communication device 100. In the
communication device 100, the control circuit 106 executes the
program 112 in the memory 110 through the CPU 108, thereby
controlling an operation of the communication device 100. The
communication device 100 can receive signals input by a user
through the input device 102, such as a keyboard, and can output
images and sounds through the output device 104, such as a monitor
or speakers. The transceiver 114 is used to receive and transmit
wireless signals, deliver received signals to the control circuit
106, and output signals generated by the control circuit 106
wirelessly. From a perspective of a communication protocol
framework, the transceiver 114 can be seen as a portion of Layer 1,
and the control circuit 106 can be utilized to realize functions of
Layer 2 and Layer 3.
[0023] Please continue to refer to FIG. 3. FIG. 3 is a diagram of
the program 112 shown in FIG. 2. The program 112 includes an
application layer 200, a Layer 3 202, and a Layer 2 206, and is
coupled to a Layer 1 218. The Layer 3 performs radio resource
control. The Layer 2 comprises a Radio Link Control (RLC) layer and
a Medium Access Control (MAC) layer, and performs link control. The
Layer 1 218 performs physical connections.
[0024] In LTE-A system, the Layer 1 218 and the Layer 2 206 may
support a Carrier Aggregation (CA) technology, which enables the UE
to perform transmission and/or reception through multiple carriers.
In such a situation, the embodiment of the present invention
provides a radio link failure (RLF) processing program 220 for
appropriately handling RLF, so as to avoid unnecessary connection
re-establishment procedures, and thus, enhance the system
performance.
[0025] Please refer to FIG. 4, which illustrates a schematic
diagram of a process 40. The process 40 is utilized for handling
RLF in a UE of the wireless communication system 10, and can be
compiled into the RLF processing program 220. The process 40
includes the following steps:
[0026] Step 400: Start.
[0027] Step 402: Configure a plurality of carriers.
[0028] Step 404: Control a timer utilized for detecting the radio
link failure according to a status of a primary carrier within the
plurality of carriers.
[0029] Step 406: End.
[0030] According to the process 40, after CA is applied, the UE
controls the timer used for detecting RLF according to the status
of the primary carrier. In other words, other carries, i.e.
secondary carriers, do not affect operations of the timer, such
that unnecessary connection re-establishment procedures can be
avoided, and radio resources can be saved. Noticeably, the
aforementioned primary carrier refers to a specific component
carrier within all the component carriers after CA is applied, and
the denomination of the primary carrier should not make limitation
to the present invention. Moreover, the timer for detecting RLF is
the aforementioned timer T310. However, the denomination of T310
follows the related radio resource control protocol, and should not
make limitation to the present invention.
[0031] In short, in the embodiment of the present invention, the
timer T310 is affected by the primary carrier and not affected by
other carriers. In addition, the timer T310 is not started when
timer T300/T301/T304/T311 is running. Therefore, even if a radio
problem is detected on a secondary carrier other than the primary
carrier, according to the process 40, the Layer 3 202 does not
start the timer T310, and thus, the connection re-establishment
procedure will not be started. Oppositely, when the Layer 1 218,
i.e. PHY layer, indicates a radio problem on the primary carrier,
e.g. consecutive out-of-sync situations on the primary carrier are
detected, the Layer 3 202 determines that the primary carrier
includes a radio problem, and starts the timer T310. If the radio
problem is not recovered before the timer T310 is expired, the
Layer 3 202 determines occurrence of RLF, and triggers the
connection re-establishment procedure, in order to re-establish a
normal connection with the network.
[0032] As can be seen, the timer T310 for detecting RLF is started
in the condition that the primary carrier has a radio problem;
thus, unnecessary connection re-establishment procedures can be
avoided, so as to save radio resources. In comparison, the prior
art does not disclose how to handle RLF after CA is applied.
[0033] In summary, when CA is applied, the present invention
controls the timer used for detecting RLF according to the status
of the primary carrier. As a result, even if secondary carriers
have radio problems, the present invention does not trigger the
connection re-establishment procedure, so as to prevent waste of
radio resources, and enhance the system performance.
[0034] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
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