U.S. patent number RE47,736 [Application Number 15/177,995] was granted by the patent office on 2019-11-19 for method and apparatus for supporting discontinuous reception operation in mobile communication system.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. The grantee listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Sung-Ho Choi, Kyeong-In Jeong, Jung-Soo Jung, Sang-Bum Kim, Soeng-Hun Kim, Chae-Gwon Lim.
United States Patent |
RE47,736 |
Kim , et al. |
November 19, 2019 |
Method and apparatus for supporting discontinuous reception
operation in mobile communication system
Abstract
A method and an apparatus for supporting a discontinuous
reception (DRX) operation in a Node B in a mobile communication
system are provided. The method includes defining a second System
Frame Number (SFN) where one cycle of a first SFN corresponds to
one bit, transmitting information on the second SFN to a User
Equipment (UE), determining a second SFN which is used to transmit
a paging signal to the UE, determining a first SFN which is used to
transmit the paging signal in the determined second SFN, and
transmitting the paging signal to the UE at the determined first
SFN.
Inventors: |
Kim; Sang-Bum (Seoul,
KR), Choi; Sung-Ho (Suwon-si, KR), Kim;
Soeng-Hun (Suwon-si, KR), Jeong; Kyeong-In
(Hwaseong-si, KR), Jung; Jung-Soo (Seongnam-si,
KR), Lim; Chae-Gwon (Seoul, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si, Gyeonggi-do |
N/A |
KR |
|
|
Assignee: |
Samsung Electronics Co., Ltd.
(Suwon-si, KR)
|
Family
ID: |
44921194 |
Appl.
No.: |
15/177,995 |
Filed: |
June 9, 2016 |
PCT
Filed: |
January 04, 2011 |
PCT No.: |
PCT/KR2011/000023 |
371(c)(1),(2),(4) Date: |
July 10, 2012 |
PCT
Pub. No.: |
WO2011/087233 |
PCT
Pub. Date: |
July 21, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
13521304 |
Jan 4, 2011 |
8750154 |
Jun 10, 2014 |
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Foreign Application Priority Data
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Jan 12, 2010 [KR] |
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10-2010-0002601 |
Apr 5, 2010 [KR] |
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10-2010-0031140 |
May 7, 2010 [KR] |
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10-2010-0043234 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
68/02 (20130101); H04W 76/28 (20180201); H04W
68/02 (20130101); H04W 76/28 (20180201); Y02D
30/70 (20200801); Y02D 30/70 (20200801) |
Current International
Class: |
G08C
17/00 (20060101); H04W 68/02 (20090101); H04W
68/00 (20090101); H04W 76/28 (20180101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2010114892 |
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May 2010 |
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JP |
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10-2004-0036966 |
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May 2004 |
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KR |
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10-2010-0091091 |
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Aug 2010 |
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KR |
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10-2010-0128323 |
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Dec 2010 |
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KR |
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10-2011-0002440 |
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Jan 2011 |
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KR |
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Other References
GS. S Kim et al, "An Adjustable Power Management for Optimal Power
Saving in LTE Terminal Baseband Modem", Oct. 2009, IEEE. cited by
examiner .
Bo et al, "DRX-Aware Scheduling Method for Delay-Sensitive
Traffic", Dec. 2010, IEEE Communications Letters, vol. 14. cited by
examiner .
R2-100331, Introduction of longer SFN length for MTC, 3GPP TSG RAN
WG2 #68bis, Valencia, Spain, Jan. 18-22. cited by
applicant.
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Primary Examiner: Craver; Charles R
Attorney, Agent or Firm: Jefferson IP Law, LLP
Claims
The invention claimed is:
1. A method for supporting a .[.Discontinuous Reception.].
.Iadd.discontinuous reception .Iaddend.(DRX) operation .[.in.].
.Iadd.by .Iaddend.a Node B in a .[.mobile.]. .Iadd.wireless
.Iaddend.communication system, the method comprising: .[.defining a
second System Frame Number (SFN) where one cycle of a first SFN
corresponds to one bit;.]. .Iadd.determining a first system frame
number (SFN) for a user equipment (UE) based on an identifier of
the UE; .Iaddend. transmitting information on .[.the.]. .Iadd.a
.Iaddend.second SFN .[.to a User Equipment (UE).]. .Iadd.for the UE
which is configured with an extended DRX, the second SFN being
incremented by one when one cycle of the first SFN wraps
around.Iaddend.; determining a second SFN which is used to transmit
a paging signal to the UE.Iadd., based on the information on the
second SFN.Iaddend.; determining .Iadd.a paging occasion based on
.Iaddend.a first SFN which is used to transmit the paging signal in
the determined second SFN .Iadd.with a cycle longer than a cycle of
the first SFN.Iaddend.; and transmitting.Iadd., to the UE,
.Iaddend.the paging signal .[.to the UE at.]. .Iadd.in .Iaddend.the
determined .[.first SFN.]. .Iadd.paging occasion.Iaddend..
2. The method of claim 1, wherein the determined second SFN
satisfies "(T.sub.M div .[.N.sub.m.].
.Iadd.N.sub.M.Iaddend.)*(UE_ID mod N.sub.M)" and the determined
first SFN satisfies "(T div N)*(UE_ID mod N)", and wherein the
N.sub.M is min (T.sub.M, nB.sub.M), the "N" is min (T, nB), the
T.sub.M, nB.sub.M, T, and nB are DRX cycles of the UE, and
.Iadd.the .Iaddend.UE_ID is .Iadd.the identifier of the UE which is
determined based on .Iaddend.an International Mobile Station
Identity (IMSI).
3. The method of claim 1, wherein the second SFN is added to one of
a .[.Master Information Block.]. .Iadd.master information block
.Iaddend.(MIB), an existing .[.System Information Block.].
.Iadd.system information block .Iaddend.(SIB), and a new SIB, and
is then transmitted to the UE.
4. The method of claim 1, wherein the UE .[.corresponds to.].
.Iadd.is .Iaddend.a machine-type communication device.
5. .[.An apparatus.]. .Iadd.A Node B .Iaddend.for supporting a
.[.Discontinuous Reception.]. .Iadd.discontinuous reception
.Iaddend.(DRX) operation in a .[.Node B in a mobile.].
.Iadd.wireless .Iaddend.communication system, the .[.apparatus.].
.Iadd.Node B .Iaddend.comprising: a transceiver .[.for defining a
second System Frame Number (SFN) where one cycle of a first SFN
corresponds to one bit, and for transmitting information on the
second SFN to a User Equipment (UE).].; and a controller .[.for.].
.Iadd.coupled with the transceiver and configured to control to:
determine a first system frame number (SFN) for a user equipment
(UE) based on an identifier of the UE, transmit information on a
second SFN for a UE which is configured with an extended DRX, the
second SFN being incremented by one when one cycle of the first SFN
wraps around,.Iaddend. .[.determining.]. .Iadd.determine .Iaddend.a
second SFN which is used to transmit a paging signal to the UE,
.Iadd.based on the information on the second SFN, .Iaddend. .[.for
determining.]. .Iadd.determine a paging occasion based on
.Iaddend.a first SFN.Iadd., .Iaddend.which is used to transmit the
paging signal in the determined second SFN .Iadd.with a cycle
longer than a cycle of the first SFN.Iaddend., and .[.for
controlling the transceiver to.]. transmit.Iadd., to the UE,
.Iaddend.the paging signal .[.to the UE at.]. .Iadd.in .Iaddend.the
determined .[.first SFN.]. .Iadd.paging occasion.Iaddend..
6. The .[.apparatus.]. .Iadd.Node B .Iaddend.of claim 5, wherein
the determined second SFN satisfies "(T.sub.M div .[.N.sub.m.].
.Iadd.N.sub.M.Iaddend.)*(UE_ID mod N.sub.M)" and the determined
first SFN satisfies "(T div N)*(UE_ID mod N)", and wherein the
N.sub.M is min (T.sub.M, nB.sub.M), the "N" is min (T, nB), the
T.sub.M, nB.sub.M, T, and nB are DRX cycles of the UE, and UE_ID is
.Iadd.determined based on .Iaddend.an International Mobile Station
Identity (IMSI).
7. The .[.apparatus.]. .Iadd.Node B .Iaddend.of claim 5, wherein
the second SFN is added to one of a .[.Master Information Block.].
.Iadd.master information block .Iaddend.(MIB), an existing
.[.System Information Block.]. .Iadd.system information block
.Iaddend.(SIB), and a new SIB, and is then transmitted to the
UE.
8. The .[.apparatus.]. .Iadd.Node B .Iaddend.of claim 5, wherein
the UE .[.corresponds to.]. .Iadd.is .Iaddend.a machine-type
communication device.
9. A method for supporting a .[.Discontinuous Reception.].
.Iadd.discontinuous reception .Iaddend.(DRX) operation .[.in.].
.Iadd.by .Iaddend.a .[.User Equipment.]. .Iadd.user equipment
.Iaddend.(UE) in a .[.mobile.]. .Iadd.wireless
.Iaddend.communication system, the method comprising:
.Iadd.determining a first system frame number (SFN) for the UE
based on an identifier of the UE;.Iaddend. receiving, from a Node
B, information on a second .[.System Frame Number (SFN), where one
cycle of a first SFN corresponds to one bit.]. .Iadd.SFN for the UE
which is configured with an extended DRX, the second SFN being
incremented by one when one cycle of the first SFN wraps
around.Iaddend.; .[.monitoring the first SFN and the second SFN
every cycle of the first SFN; determining whether the second SFN
includes a paging signal; determining whether the first SFN
corresponding to the second SFN includes the paging signal when the
second SFN includes the paging signal; and identifying the paging
signal through the first SFN when the first SFN includes the paging
signal.]. .Iadd.determining a second SFN which is used to transmit
a paging signal to the UE, based on the information on the second
SFN; determining a paging occasion based on a first SFN which is
used to transmit the paging signal in the determined second SFN
with a cycle longer than a cycle of the first SFN; and monitoring
whether the paging signal is received in the determined paging
occasion.Iaddend..
10. The method of claim 9, wherein a case in which the second SFN
includes the paging signal corresponds to a case in which the
second SFN satisfies "(T.sub.M div NM)*(UE_ID mod N.sub.M)" and a
case in which the first SFN includes the paging signal corresponds
to a case in which the first SFN satisfies "(T div N)*(UE_ID mod
N)", wherein the N.sub.M is min (T.sub.M, nB.sub.M), the "N" is min
(T, nB), the T.sub.M, nB.sub.M, T, and nB are DRX cycles of the UE,
and .Iadd.the .Iaddend.UE_ID is .Iadd.the identifier of the UE
which is determined based on .Iaddend.an International Mobile
Station Identity (IMSI).
11. The method of claim 9, wherein the second SFN is added to one
of a .[.Master Information Block.]. .Iadd.master information block
.Iaddend.(MIB), an existing .[.System Information Block.].
.Iadd.system information block .Iaddend.(SIB), and a new SIB, and
is then transmitted to the UE.
12. The method of claim 9, wherein the UE .[.corresponds to.].
.Iadd.is .Iaddend.a machine-type communication device.
13. .[.An apparatus.]. .Iadd.A user equipment (UE) .Iaddend.for
supporting a .[.Discontinuous Reception.]. .Iadd.discontinuous
reception .Iaddend.(DRX) operation .[.in a User Equipment (UE).].
in a .[.mobile.]. .Iadd.wireless .Iaddend.communication system, the
.[.apparatus.]. .Iadd.UE .Iaddend.comprising: a transceiver .[.for
receiving, from a Node B, information on a second System Frame
Number (SFN), where one cycle of a first SFN corresponds to one
bit.].; and a controller .[.for.]. .Iadd.coupled with the
transceiver and configured to control to: determine a first system
frame number (SFN) for the UE based on an identifier of the UE,
receive, from a Node B, information on a second SFN for the UE
which is configured with an extended DRX, the second SFN being
incremented by one when one cycle of the first SFN wraps around,
determine a second SFN which is used to transmit a paging signal to
the UE, based on the information on the second SFN, determine a
paging occasion based on a first SFN which is used to transmit the
paging signal in the determined second SFN with a cycle longer than
a cycle of the first SFN, and .Iaddend. .[.monitoring the first SFN
and the second SFN every cycle of the first SFN, for determining
whether the second SFN includes a paging signal, for determining
whether the first SFN corresponding to the second SFN includes the
paging signal when the second SFN includes the paging signal, and
for identifying the paging signal through the first SFN when the
first SFN includes the paging signal.]. .Iadd.monitor whether the
paging signal is received in the paging occasion.Iaddend..
14. The .[.apparatus.]. .Iadd.UE .Iaddend.of claim 13, wherein the
second SFN is added to one of a .[.Master Information Block.].
.Iadd.master information block .Iaddend.(MIB), an existing
.[.System Information Block.]. .Iadd.system information block
.Iaddend.(SIB), and a new SIB, and is then transmitted to the
UE.
15. The .[.apparatus.]. .Iadd.UE .Iaddend.of claim 13, wherein a
case in which the second SFN includes the paging signal corresponds
to a case in which the second SFN satisfies "(T.sub.M div
NM)*(UE_ID mod N.sub.M)" and a case in which the first SFN includes
the paging signal corresponds to a case in which the first SFN
satisfies "(T div N)*(UE_ID mod N)", wherein the N.sub.M is min
(T.sub.M, nB.sub.M), the "N" is min (T, nB), the T.sub.M, nB.sub.M,
T, and nB are DRX cycles of the UE, and .Iadd.the .Iaddend.UE_ID is
.Iadd.the identifier of the UE which is determined based on
.Iaddend.an International Mobile Station Identity (IMSI).
16. The .[.apparatus.]. .Iadd.UE .Iaddend.of claim 13, wherein the
UE .[.corresponds to.]. .Iadd.is .Iaddend.a machine-type
communication device.
.[.17. A method for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication
system, the method comprising: receiving system information which
includes a cell-specific DRX cycle from a Node B; transmitting an
attach request message, which includes a UE-specific DRX cycle and
an indication for selecting a DRX cycle of a long cycle, to a
Mobility Management Entity (MME); selecting a longer cycle of the
cell-specific DRX cycle and the UE-specific DRX cycle when
receiving an attach response message from the MME; and receiving a
paging message from the Node B in the selected DRX cycle..].
.[.18. An apparatus for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication
system, the apparatus comprising: a transceiver for receiving
system information which includes a cell-specific DRX cycle from a
Node B, and for transmitting an attach request message to a
Mobility Management Entity (MME), the attach request message
including a UE-specific DRX cycle and an indication for selecting a
DRX cycle of a long cycle; and a controller for selecting a longer
cycle of the cell-specific DRX cycle and the UE-specific DRX cycle
when receiving an attach response message from the MME; and for
controlling the transceiver to receive a paging message from the
Node B in the selected DRX cycle..].
.[.19. A method for supporting a Discontinuous Reception (DRX)
operation in a Node B in a mobile communication system, the method
comprising: transmitting system information which includes a
cell-specific DRX cycle to a User Equipment (UE); receiving a
UE-specific DRX cycle and an indication for selecting a DRX cycle
of a long cycle from a Mobility Management Entity (MME); selecting
a longer cycle of the cell-specific DRX cycle and the UE-specific
DRX cycle; and transmitting a paging message to the UE in the
selected DRX cycle..].
.[.20. An apparatus for supporting a Discontinuous Reception (DRX)
operation in a Node B in a mobile communication system, the
apparatus comprising: a transceiver for transmitting system
information which includes a cell-specific DRX cycle to a User
Equipment (UE), and for receiving a UE-specific DRX cycle and an
indication for selecting a DRX cycle of a long cycle from a
Mobility Management Entity (MME); and a controller for selecting a
longer cycle of the cell-specific DRX cycle and the UE-specific DRX
cycle, and for controlling the transceiver to transmit a paging
message to the UE in the selected DRX cycle..].
.[.21. A method for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication
system, the method comprising: determining whether a cell on which
the UE is currently camping corresponds to a cell supporting a DRX
cycle of a long cycle; selecting a longer DRX cycle of a
cell-specific DRX cycle and a UE-specific DRX cycle when the cell
on which the UE is currently camping supports the DRX cycle of a
long cycle; and receiving a paging message from a Node B of the
cell, on which the UE is camping, in the selected DRX cycle..].
.[.22. The method as claimed in claim 21, further comprising:
selecting a shorter DRX cycle of a cell-specific DRX cycle and a
UE-specific DRX cycle when the cell on which the UE is currently
camping does not support the DRX cycle of a long cycle..].
.[.23. An apparatus for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication
system, the apparatus comprising: a controller for determining
whether a cell on which the UE is currently camping corresponds to
a cell supporting a DRX cycle of a long cycle, and for selecting a
longer DRX cycle of a cell-specific DRX cycle and a UE-specific DRX
cycle when the cell on which the UE is currently camping supports
the DRX cycle of a long cycle; and a transceiver for receiving a
paging message from a Node B of the cell, on which the UE is
camping, in the selected DRX cycle..].
.[.24. The apparatus as claimed in claim 23, wherein, when the cell
on which the UE is currently camping does not support the DRX cycle
of a long cycle, the controller selects a shorter DRX cycle of a
cell-specific DRX cycle and a UE-specific DRX cycle..].
.[.25. A method for supporting a Discontinuous Reception (DRX)
operation in a Mobility Management Entity (MME) in a mobile
communication system, the method comprising: receiving a request
for a DRX cycle of a long cycle from a User Equipment (UE);
determining whether a cell on which the UE is camping supports a
DRX cycle of a long cycle; and transmitting a paging message to a
Node B of the cell, on which the UE is camping, in a UE-specific
DRX cycle when the cell on which the UE is camping supports a DRX
cycle of a long cycle..].
.[.26. The method as claimed in claim 25, further comprising:
transmitting the paging message to the Node B of the cell, on which
the UE is camping, in a predetermined cycle when the cell on which
the UE is camping does not support a DRX cycle of a long
cycle..].
.[.27. An apparatus for supporting a Discontinuous Reception (DRX)
operation in a Mobility Management Entity (MME) in a mobile
communication system, the apparatus comprising: a transceiver for
receiving a request for a DRX cycle of a long cycle from a User
Equipment (UE); and a controller for determining whether a cell on
which the UE is camping supports a DRX cycle of a long cycle, and
for controlling the transceiver to transmit a paging message to a
Node B of the cell, on which the UE is camping, in a UE-specific
DRX cycle when the cell on which the UE is camping supports a DRX
cycle of a long cycle..].
.[.28. The apparatus as claimed in claim 27, wherein, when the cell
on which the UE is camping does not support a DRX cycle of a long
cycle, the controller controls the transceiver to transmit the
paging message the Node B of the cell, on which the UE is camping,
in a predetermined cycle..].
.Iadd.29. The method of claim 1, wherein the second SFN which is
used to transmit the paging signal to the UE, is determined using
the information and identification information of the
UE..Iaddend.
.Iadd.30. The Node B of claim 5, wherein the second SFN which is
used to transmit the paging signal to the UE, is determined using
the information and identification information of the
UE..Iaddend.
.Iadd.31. The method of claim 9, wherein the second SFN which is
used to transmit the paging signal to the UE, is determined using
the information and identification information of the
UE..Iaddend.
.Iadd.32. The UE of claim 13, wherein the second SFN which is used
to transmit the paging signal to the UE, is determined using the
information and identification information of the UE..Iaddend.
Description
PRIORITY
This application is a National Stage application under 35 U.S.C.
.sctn.371 of an International application filed on Jan. 4, 2011 and
assigned application No. PCT/KR2011/000023, and claims the benefit
under 35 U.S.C. .sctn.365(b) of a Korean patent application filed
in the Korean Industrial Property Office on Jan. 12, 2010 and
assigned Ser. No. 10-2010-0002601, a Korean patent application
filed in the Korean Industrial Property Office on Apr. 5, 2010 and
assigned Ser. No. 10-2010-0031140, and a Korean patent application
filed in the Korean Industrial Property Office on May 7, 2010 and
assigned Ser. No. 10-2010-0043234, the entire disclosure of each of
which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system.
More particularly, the present invention relates to a method and
apparatus for supporting a Discontinuous Reception (DRX) operation
in a mobile communication system.
2. Description of the Related Art
In general, mobile communication systems have been developed with
an aim to provide communication while guaranteeing mobility of
users thereof. With the rapid progress of technologies, such mobile
communication systems have been developed to provide not only voice
communication services but also high-speed data communication
services. Now, the next-generation mobile communication system is
being conducted to provide Human-to-Machine (H2M) communication and
Machine-to-Machine (M2M) communication, beyond Human-to-Human (H2H)
communication. In order to meet such a requirement, the 3rd
Generation Partnership Project (3GPP), which is responsible for the
standardization of communication, is working on a standard for
machine-type communication. 3GPP SA1 Working Group (WG), which is
responsible for defining services and characteristics thereof, is
already discussing service requirements for machine-type
communication.
FIG. 1 is a block diagram illustrating a communication scenario for
machine-type communication according to the related art.
Referring to FIG. 1, machine-type communication devices 105 are
connected with a wireless provider network 110. Generally, the
machine-type communication devices 105 may be defined as various
unattended devices, including as meters, automatic vending
machines, and the like. The machine-type communication devices 105
may have characteristics different from those of the existing
wireless User Equipments (UEs) in several respects. Also, the
machine-type communication devices 105 may have different
characteristics depending on the types thereof. One cell may
include numerous machine-type communication devices 105. A
machine-type communication server 115, which has information on the
machine-type communication devices 105, functions not only to
perform authentication, but also to gather and deliver information,
which is collected from the machine-type communication devices 105.
The machine-type communication server 115 delivers the information
to a machine-type communication user 120. The machine-type
communication server 115 may exist inside or outside of the
wireless provider network 110. In addition, the machine-type
communication user 120 is a final user who needs information
delivered from the machine-type communication devices 105.
The machine-type communication has characteristics different from
those of the existing wireless communication. Also, the
characteristics of the machine-type communication are classified in
various ways depending on the use purposes. For example,
machine-type communication devices requiring communication only a
few times a day regardless of time have a time-tolerant
characteristic; and machine-type communication devices, which are
installed at fixed positions without mobility and are configured to
collect and transmit specific information, have a low mobility
characteristic. Wireless providers have to provide services by
taking characteristics of such various machine-type communications
and the coexistence of machine-type communication devices and the
existing UEs into consideration.
Of machine-type communication devices, tracking-related devices,
such as devices equipped on animals or trucks, generally either use
batteries, or are supplied with power generated by themselves.
Therefore, because such machine-type communication devices can use
only limited power, the machine-type communication services must be
configured to efficiently use extremely small power. The 3GPP SA1
WG defines an extra low power consumption mode, in which
machine-type communication devices may be set to use low power.
In the extra low power consumption mode, operations capable of
reducing the use of power can be performed, wherein one of such
operations is a method of lengthening a Discontinuous Reception
(DRX) cycle. A UE performs a reception operation in order to
receive a paging signal from an evolved Node B (eNB). However, a
paging signal is not a frequently transmitted signal. Consequently,
if the UE performs a reception operation even while the eNB does
not transmit a paging signal, power loss becomes large. Therefore,
in order to reduce power consumption, it is possible to
periodically perform a reception operation only during specific
time intervals so as to attempt to receive a paging signal, which
is called a Discontinuous Reception (DRX). In a Long Term Evolution
(LTE) system, the DRX operations of UEs being in an idle state are
achieved by Equation 1 below. A System Frame Number (SFN) increases
by one every radio frame. In a radio frame satisfying Equation 1
below, a paging signal is delivered, and a UE performs a reception
operation based on DRX. SFN mod T=(T div N)*(U_ID mod N) (1)
In Equation 1, "SFN" has 10 bits (i.e., MSB 8 bits explicit, and
LBS 2 bits implicit), and "T" denotes a DRX cycle of a UE. The "T"
is a value, which is included in a System Information Block Type 2
(SIB2) and is provided from an eNB, and may be, for example, rf32,
rf64, rf128, or rf256. Also, "N" is "min (T, nB)," wherein "nB" is
a value which is included in the SIB2 and is provided from the eNB,
and may be, for example, 4T, 2T, T, T/2, T/4, T/8, T/16, or T/32.
In addition, "UE_ID" is International Mobile Station Identity
(IMSI) mod 1024, and 8 bits of a Master Information Block (MIB) of
a Physical Broadcast CHannel (PBCH) represent an SFN.
FIG. 2 is a view showing a conception of a paging occasion in a
conventional LTE technology according to the related art.
Referring to FIG. 2, an SFN increases by one every radio frame (see
reference numeral 205). The SFN has a cycle of 1024, and is set to
zero (see reference numeral 210). In addition, based on equation 1,
a paging signal having the same pattern is repeated every SFN cycle
(see reference numeral 215).
Most UEs corresponding to machine-type communication devices are
expected to less frequently receive a paging signal than general
UEs. For example, tracking-related devices will communicate with an
eNB only a few times a day. Therefore, when a DRX cycle is set to
be very long, it is possible to remarkably reduce power consumption
due to reception operations. However, due to the characteristics of
the 3GPP LTE system, the DRX cycle is limited by the length of an
SFN. When the length of an SFN is 1024, the DRX cycle cannot exceed
1024. Accordingly, it is necessary to develop a method for first
extending the length of an SFN in order to extend a DRX cycle, and
a method for allowing an SFN extended for machine-type
communication not to exert an influence on the paging operations of
the existing UEs.
Therefore, a need exists for a method and apparatus for a
Discontinuous Reception (DRX) operation in a mobile communication
system. A need also exists for a method and apparatus for
implementing a long SFN to extend the DRX cycle of a machine-type
communication device in a mobile communication system.
The above information is presented as background information only
to assist with an understanding of the present disclosure. No
determination has been made, and no assertion is made, as to
whether any of the above might be applicable as prior art with
regard to the present invention.
SUMMARY OF THE INVENTION
Aspects of the present invention are to address at least the
above-mentioned problems and/or disadvantages and to provide at
least the advantages described below. Accordingly, an aspect of the
present invention is to provide a method and apparatus for a
Discontinuous Reception (DRX) operation in a mobile communication
system.
Another aspect of the present invention is to provide a method and
apparatus for implementing a long System Frame Number (SFN) to
extend the DRX cycle of a machine-type communication device in a
mobile communication system.
Another aspect of the present invention is to provide a DRX
operation method and apparatus for Machine-Type Communication
(MTC), which is compatible with the existing DRX, in a mobile
communication system.
In accordance with an aspect of the present invention, a method for
supporting a Discontinuous Reception (DRX) operation in a Node B in
a mobile communication system is provided. The method includes
defining a second System Frame Number (SFN) where one cycle of a
first SFN corresponds to one bit, transmitting information on the
second SFN to a User Equipment (UE), determining a second SFN which
is used to transmit a paging signal to the UE, determining a first
SFN which is used to transmit the paging signal in the determined
second SFN, and transmitting the paging signal to the UE at the
determined first SFN.
In accordance with another aspect of the present invention, an
apparatus for supporting a Discontinuous Reception (DRX) operation
in a Node B in a mobile communication system is provided. The
apparatus includes a transceiver for defining a second System Frame
Number (SFN) where one cycle of a first SFN corresponds to one bit,
and for transmitting information on the second SFN to a User
Equipment (UE), and a controller for determining a second SFN which
is used to transmit a paging signal to the UE, for determining a
first SFN which is used to transmit the paging signal in the
determined second SFN, and for controlling the transceiver to
transmit the paging signal to the UE at the determined first
SFN.
In accordance with still another aspect of the present invention, a
method for supporting a Discontinuous Reception (DRX) operation in
a User Equipment (UE) in a mobile communication system is provided.
The method includes receiving, from a Node B, information on a
second System Frame Number (SFN), where one cycle of a first SFN
corresponds to one bit, monitoring the first SFN and the second SFN
every cycle of the first SFN, determining whether the second SFN
includes a paging signal, and determining whether the first SFN
corresponding to the second SFN includes the paging signal when the
second SFN includes the paging signal, and identifying the paging
signal through the first SFN when the first SFN includes the paging
signal.
In accordance with still another aspect of the present invention,
an apparatus for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication system
is provided. The apparatus includes a transceiver for receiving,
from a Node B, information on a second System Frame Number (SFN),
where one cycle of a first SFN corresponds to one bit, and a
controller for monitoring the first SFN and the second SFN every
cycle of the first SFN, determining whether the second SFN includes
a paging signal, determining whether the first SFN corresponding to
the second SFN includes the paging signal when the second SFN
includes the paging signal, and for identifying the paging signal
through the first SFN when the first SFN includes the paging
signal.
In accordance with still another aspect of the present invention, a
method for supporting a Discontinuous Reception (DRX) operation in
a User Equipment (UE) in a mobile communication system is provided.
The method includes receiving system information which includes a
cell-specific DRX cycle from a Node B, transmitting an attach
request message, which includes a UE-specific DRX cycle and an
indication for selecting a DRX cycle of a long cycle, to a Mobility
Management Entity (MME), selecting a longer cycle of the
cell-specific DRX cycle and the UE-specific DRX cycle when
receiving an attach response message from the MME, and receiving a
paging message from the Node B in the selected DRX cycle.
In accordance with still another aspect of the present invention,
an apparatus for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication system
is provided. The apparatus includes a transceiver for receiving
system information which includes a cell-specific DRX cycle from a
Node B, and for transmitting an attach request message to a
Mobility Management Entity (MME), the attach request message
including a UE-specific DRX cycle and an indication for selecting a
DRX cycle of a long cycle, and a controller for selecting a longer
cycle of the cell-specific DRX cycle and the UE-specific DRX cycle
when receiving an attach response message from the MME, and
controlling the transceiver to receive a paging message from the
Node B in the selected DRX cycle.
In accordance with still another aspect of the present invention, a
method for supporting a Discontinuous Reception (DRX) operation in
a Node B in a mobile communication system is provided. The method
includes transmitting system information which includes a
cell-specific DRX cycle to a User Equipment (UE), receiving a
UE-specific DRX cycle and an indication for selecting a DRX cycle
of a long cycle from a Mobility Management Entity (MME), selecting
a longer cycle of the cell-specific DRX cycle and the UE-specific
DRX cycle, and transmitting a paging message to the UE in the
selected DRX cycle.
In accordance with still another aspect of the present invention,
an apparatus for supporting a Discontinuous Reception (DRX)
operation in a Node B in a mobile communication system is provided.
The apparatus includes a transceiver for transmitting system
information which includes a cell-specific DRX cycle to a User
Equipment (UE), and for receiving a UE-specific DRX cycle and an
indication for selecting a DRX cycle of a long cycle from a
Mobility Management Entity (MME); and a controller for selecting a
longer cycle of the cell-specific DRX cycle and the UE-specific DRX
cycle, and for controlling the transceiver to transmit a paging
message to the UE in the selected DRX cycle.
In accordance with still another aspect of the present invention, a
method for supporting a Discontinuous Reception (DRX) operation in
a User Equipment (UE) in a mobile communication system is provided.
The method includes determining whether a cell on which the UE is
currently camping corresponds to a cell supporting a DRX cycle of a
long cycle, selecting a longer DRX cycle of a cell-specific DRX
cycle and a UE-specific DRX cycle when the cell on which the UE is
currently camping supports the DRX cycle of a long cycle, and
receiving a paging message from a Node B of the cell, on which the
UE is camping, in the selected DRX cycle.
In accordance with still another aspect of the present invention,
an apparatus for supporting a Discontinuous Reception (DRX)
operation in a User Equipment (UE) in a mobile communication system
is provided. The apparatus includes a controller for determining
whether a cell on which the UE is currently camping corresponds to
a cell supporting a DRX cycle of a long cycle, and for selecting a
longer DRX cycle of a cell-specific DRX cycle and a UE-specific DRX
cycle when the cell on which the UE is currently camping supports
the DRX cycle of a long cycle, and a transceiver for receiving a
paging message from a Node B of the cell, on which the UE is
camping, in the selected DRX cycle.
In accordance with still another aspect of the present invention, a
method for supporting a Discontinuous Reception (DRX) operation in
a Mobility Management Entity (MME) in a mobile communication system
is provided. The method includes receiving a request for a DRX
cycle of a long cycle from a User Equipment (UE), determining
whether a cell on which the UE is camping supports a DRX cycle of a
long cycle, and transmitting a paging message to a Node B of the
cell, on which the UE is camping, in a UE-specific DRX cycle when
the cell on which the UE is camping supports a DRX cycle of a long
cycle.
In accordance with still another aspect of the present invention,
an apparatus for supporting a Discontinuous Reception (DRX)
operation in a Mobility Management Entity (MME) in a mobile
communication system is provided. The apparatus includes a
transceiver for receiving a request for a DRX cycle of a long cycle
from a User Equipment (UE), and a controller for determining
whether a cell on which the UE is camping supports a DRX cycle of a
long cycle, and for controlling the transceiver to transmit a
paging message to a Node B of the cell, on which the UE is camping,
in a UE-specific DRX cycle when the cell on which the UE is camping
supports a DRX cycle of a long cycle.
According to the embodiments of the present invention, the DRX
cycle of a machine-type communication device is lengthened in a
mobile communication system, so that it is possible to reduce the
power consumption due to reception operations.
Also, according to the embodiments of the present invention, the
length of an SFN is first extended in order to lengthen a DRX cycle
in a mobile communication system, thereby exerting no influence on
the paging operations of the existing UEs.
Meanwhile, the other various effects have been disclosed directly
or suggestively in the above description according to the
embodiments of the present invention.
Other aspects, advantages, and salient features of the invention
will become apparent to those skilled in the art from the following
detailed description, which, taken in conjunction with the annexed
drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features, and advantages of certain
exemplary embodiments of the present invention will be more
apparent from the following description taken in conjunction with
the accompanying drawings, in which:
FIG. 1 is a block diagram illustrating a communication scenario for
machine-type communication according to the related art;
FIG. 2 is a view showing a conception of a paging occasion in a
Long Term Evolution (LTE) technology according to the related
art;
FIG. 3 is a view showing a conception of a paging occasion
according to a first exemplary embodiment of the present
invention;
FIG. 4 is a flowchart illustrating the operation of a machine-type
communication device according to the first exemplary embodiment of
the present invention;
FIG. 5 is a block diagram illustrating the configuration of a User
Equipment (UE) according to the first exemplary embodiment of the
present invention;
FIG. 6 is a flowchart illustrating the operation of an evolved Node
B (eNB) according to the first exemplary embodiment of the present
invention;
FIG. 7 is a block diagram illustrating the configuration of an eNB
according to an exemplary embodiment of the present invention;
FIG. 8 is a flow diagram illustrating a procedure for applying a
UE-specific Discontinuous Reception (DRX) cycle according to a
second exemplary embodiment of the present invention;
FIG. 9 is a flow diagram illustrating the operations of a UE and an
Mobility Management Entity (MME) according to a third exemplary
embodiment of the present invention;
FIG. 10 is a flowchart illustrating the operation of the UE
according to the third exemplary embodiment of the present
invention; and
FIG. 11 is a flowchart illustrating the operation of the MME
according to the third exemplary embodiment of the present
invention.
Throughout the drawings, it should be noted that like reference
numbers are used to depict the same or similar elements, features,
and structures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
The following description with reference to the accompanying
drawings is provided to assist in a comprehensive understanding of
exemplary embodiments of the invention as defined by the claims and
their equivalents. It includes various specific details to assist
in that understanding but these are to be regarded as merely
exemplary. Accordingly, those of ordinary skill in the art will
recognize that various changes and modifications of the embodiments
described herein can be made without departing from the scope and
spirit of the invention. In addition, descriptions of well-known
functions and constructions may be omitted for clarity and
conciseness.
The terms and words used in the following description and claims
are not limited to the bibliographical meanings, but, are merely
used by the inventor to enable a clear and consistent understanding
of the invention. Accordingly, it should be apparent to those
skilled in the art that the following description of exemplary
embodiments of the present invention is provided for illustration
purpose only and not for the purpose of limiting the invention as
defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, reference to "a component surface"
includes reference to one or more of such surfaces.
Exemplary embodiments of the present invention provide a method and
an apparatus for performing a Discontinuous Reception (DRX)
operation based on a DRX cycle.
First Exemplary Embodiment
The first exemplary embodiment of the present invention provides a
method for implementing a long System Frame Number (SFN) in order
to extend a DRX cycle of a machine-type communication device, and a
method for supporting a DRX operation compatible with existing DRX
in a mobile communication system.
Hereinafter, according to the first exemplary embodiment of the
present invention, a method for extending the length of an SFN of a
machine-type communication device, and a DRX operation method for a
machine-type communication device using a long DRX cycle will be
described one after another.
In order to extend the length of an SFN to extend a DRX cycle of a
machine-type communication device, an evolved Node B (eNB) must
additionally transmit SFN bits to the machine-type communication
device, and the transmission methods are as follows.
1) Transmitting additional SFN bits in a Master Information Block
(MIB);
2) Transmitting additional SFN bits in an existing System
Information Block (SIB);
3) Defining a new SIB for a machine-type communication device, and
transmitting additional SFN bits in the new SIB.
In the first method of transmitting additional SFN bits in an MIB,
the MIB includes necessary information, such as a downlink
frequency band, a Physical Hybrid ARQ Indicator CHannel (PHICH)
configuration information, and an SFN. In addition, the MIB
contains 10 unused spare bits, which may be used to extend the
length of an SFN. While general UEs use the existing SFN of 8 bits,
machine-type communication devices can use not only the existing
SFN of 8 bits but also extended SFN bits. Accordingly, while
exerting no influence on the DRX operations of general UEs,
machine-type communication devices can perform a DRX operation in a
longer cycle.
In the second method of transmitting additional SFN bits in an
existing SIB, the SIB has no resource limit in transmitting SFN
bits, as compared with the MIB. By taking SFN bits of an MIB and
SFN bits added to the SIB together into consideration, it is
possible to express an SFN with a longer length. General UEs take
only SFN bits of an MIB into consideration, and machine-type
communication devices take the SFN bits of the MIB and the SFN bits
added to the SIB together into consideration. The added SFN bits
represent a value which is obtained by increasing by one every
existing one SFN cycle (or every multiple of an SFN cycle, e.g.,
1/2 SFN cycle, 3 SFN cycle, etc.). Through the value represented as
above, it is possible to express an SFN length longer than the
existing SFN length.
Also, according to the third method, SFN bits to be added may be
included in a new SIB for a machine-type communication device. As
described above, because the same additional SFN bit value is used
within one SFN cycle, it is unnecessary to transmit an additional
SFN bit value in all radio frames within one SFN cycle. Therefore,
when additional SFN bits are transmitted in a SIB that is not
frequently transmitted (e.g., preference of SIB2 to SIB 1), or when
additional SFN bits are transmitted only in an SIB transmitted in a
specific radio frame, it is possible to reduce an overhead due to
the additional SFN bits. For example, when an SFN length is 1024,
additional SFN bits may be transmitted only in an SIB transmitted
in every radio frame corresponding to "SFN=0." Also, in
consideration of the probability of reception failure, additional
SFN bits may be transmitted in more radio frames. Also, in order to
deliver information for a machine-type communication device, a new
SIB may be made. In this case, additional SFN bits may be carried
by the new SIB. Generally, because the new SIB is not frequently
transmitted, the resulting overhead increase is small. According to
the number of added SFN bits, the DRX cycle is extended as Table 1
below. As shown in Table 1 below, when 10 bits are added, the DRX
cycle can be extended up to a maximum of about three hours.
TABLE-US-00001 TABLE 1 Extended Bits 2n Cycle (Min) 1 2 0.3 2 4 0.7
3 8 1.4 4 16 2.7 5 32 5.5 6 64 10.9 7 128 21.8 8 256 43.7 9 512
87.4 10 1024 174.8
Hereinafter, the aforementioned DRX operation for a machine-type
communication device using a long SFN will be described. The first
exemplary embodiment of the present invention proposes a method for
extending a DRX cycle, and for simultaneously receiving a paging
signal several times during a predetermined DRX cycle in order to
increase the probability of reception success of the paging signal.
To this end, a paging occasion is determined through a procedure
including two steps.
1) First step: determining additional SFN bits to transmit a paging
signal for a machine-type communication device;
2) Second step: determining an SFN at which a paging signal is to
be transmitted in the additional SFN bits determined in the first
step.
In the first step, additional SFN bits to transmit a paging signal
are determined. The additional SFN bits have a value increased by
one every SFN cycle. A value expressed by the additional SFN bits
is defined as a Super SFN (SSFN). Equation 2 below is used to find
an SSFN at which a paging signal is to be transmitted. SSFN mod
T.sub.M=(T.sub.M div N.sub.M)*(UE_ID mod N.sub.M) (2)
In Equation 2, N.sub.M is min (T.sub.M, nBM), and T.sub.M and
nB.sub.M are values provided from an eNB and may be included in an
SIB2. UE_ID is an IMSI mod 1024 (or MTC device group ID mode 1024),
and can be derived from the same IMSI module operation as the
general UE. In addition, in the case of a machine-type
communication device, because the communication device can be
expressed in the form of a group ID, the UE_ID may be expressed by
a group ID. After an SSFN at which a paging signal is to be
transmitted is determined, as described above, it is determined
which radio frames in the determined SSFN are used to transmit the
paging signal. This can be implemented in such a way as described
with reference to Equation 1.
As described above, when an occurrence occasion of a paging signal
is defined by the two steps, and machine-type communication devices
have a DRX cycle according to the defined occurrence occasion, it
is possible to greatly reduce power consumption. Also, because a
paging signal can be repeatedly transmitted according to "T" and
"nB" set in an SSFN, which has been determined in the first step,
it is possible to increase the reception probability of the paging
signal.
FIG. 3 is a view showing a conception of a paging occasion
according to the first exemplary embodiment of the present
invention.
Referring to FIG. 3, an SSFN 305 increases by one every SFN cycle
of 1024. Based on Equation 2, an SSFN 315 at which a paging signal
is to be transmitted is determined. An SFN 310 increases by one
every radio frame.
In the SSFN 315 determined based on Equation 2, an eNB transmits a
paging signal 320 based on Equation 1.
FIG. 4 is a flowchart illustrating the operation of a UE according
to the first exemplary embodiment of the present invention. Here,
the UE according to the first embodiment of the present invention
is a machine-type communication device.
Referring to FIG. 4, in step 410, a UE monitors an SSFN and an SFN.
For example, the UE monitors the SSFN and the SFN at the same time
by additional SFN bits in an MIB, by additional SFN bits in an
existing SIB, or by additional SFN bits in a new SIB, as described
above. In this case, because the UE is aware of a time interval of
one SFN and SSFN in step 410, it is unnecessary to perform a
real-time monitoring, and it is enough to occasionally perform a
monitoring so as to reduce the power consumption.
In step 415, the UE determines whether the monitored current SSFN
satisfies Equation 2. When the current SSFN satisfies Equation 2, a
paging signal can be transmitted in the current SSFN. Accordingly,
the UE proceeds to step 420 in order to prepare the performance of
a DRX. In contrast, when the current SSFN does not satisfy Equation
2 in step 415, the UE returns to step 410.
In step 420, the UE determines whether the monitored current SFN
satisfies Equation 1. When the current SFN satisfies Equation 1, it
means that a paging signal can be transmitted in the current SFN,
so that the UE proceeds to step 425 in order to perform a DRX. In
contrast, when the current SFN does not satisfy Equation 1 in step
420, the UE returns to step 410.
Then, in step 425, the UE decodes a PDCCH, and performs a DRX when
a decoding-resultant PDCCH includes a paging signal.
FIG. 5 is a block diagram illustrating the configuration of a UE
according to the first exemplary embodiment of the present
invention.
Referring to FIG. 5, a UE 500 includes a transceiver 505, a
controller 510, and a buffer 515.
The transceiver 505 receives an MIB, an SIB, or a new SIB from an
eNB, and monitors an SSFN and an SFN. As an example, the monitoring
is controlled by the controller 510. The SFN increases by one every
radio frame of 10 ms, and the SSFN increases by one every SFN cycle
having a length of 1024, which the UE 500 is aware of in advance.
Therefore, the transceiver 505 in the UE 500 needs not decode a
PBCH and a PDCCH every time in order to receive an MIB or SIB, and
has only to occasionally monitor the PBCH and PDCCH.
The controller 510 determines whether the monitored current SFN and
SSFN satisfy Equation 1 and Equation 2, respectively, and
calculates a time point when a paging signal is transmitted. Then,
when the time point when a paging signal is transmitted is reached,
the controller 510 shifts the transceiver 505 into a reception
mode, and attempts to decode a PDCCH. Then, when receiving a paging
signal, the controller 510 stores the received paging signal in the
buffer 515, and transfers information on the received paging signal
to an upper layer.
FIG. 6 is a flowchart illustrating the operation of an eNB
according to the first exemplary embodiment of the present
invention.
Referring to FIG. 6, the eNB determines whether a paging signal is
required for the UE 500 in step 610. That is, when receiving data,
which is to be transmitted to the UE 500, from an upper layer in
step 610, the eNB determines that a paging signal is required, and
proceeds to step 615. In contrast, when the eNB does not receive
data to be transmitted to the UE 500 in step 610, the eNB is
maintained in a waiting state until the eNB receives data to be
transmitted to the UE 500.
In step 615, the eNB determines a timing (i.e., an SSFN and SFN),
at which a paging signal is to be transmitted by taking an UE_ID
(or MTC group ID) of the UE 500. Then, in step 620, the eNB checks
the current SSFN and SFN. In step 625, the eNB determines whether
the checked current SSFN satisfies Equation 2, and proceeds to step
630 when the current SSFN satisfies Equation 2. In contrast, when
current SSFN does not satisfy Equation 2 in step 625, the eNB
returns to step 620. In step 630, the eNB determines whether the
checked current SFN satisfies Equation 1, and proceeds to step 635
in order to transmit a paging signal when the current SFN satisfies
equation 1. In contrast, when current SFN does not satisfy Equation
1 in step 630, the eNB returns to step 620.
Then, in step 635, when a transmission timing according to the
checked SSFN and SFN is reached, the eNB transmits a paging signal
to the UE 500 by a PDCCH.
FIG. 7 is a block diagram illustrating the configuration of an eNB
according to an exemplary embodiment of the present invention.
Referring to FIG. 7, the eNB 700 includes a buffer 705, a
controller 710, and a transceiver 715.
The controller 710 determines whether data to be transmitted to the
UE 500 has been received through the buffer 705 from an upper
layer. Then, the controller 710 calculates a timing (i.e., an SSFN
and SFN), at which a paging signal is to be transmitted by taking
an UE_ID (or MTC group ID) of the UE 500. When the calculated SSFN
and SFN (i.e., a timing at which the paging signal is to be
transmitted), is reached based on Equations 1 and 2, the controller
710 transmits a Physical Downlink Control CHannel (PDCCH) including
the paging signal through the transceiver 715 to the UE 500.
Second Exemplary Embodiment
Hereinafter, a DRX operation method using a long DRX cycle
according to the second exemplary embodiment of the present
invention.
In the related art, a Mobility Management Entity (MME) compares a
UE-specific DRX cycle and a cell-specific DRX cycle, and determines
and uses a smaller value of the two DRX cycles as a paging cycle of
a corresponding UE. Thus, in the related art, although a UE wants
to receive a paging in a cycle longer than a cell-specific DRX
cycle and transmits a UE-specific DRX cycle of a long cycle to the
MME, the UE cannot be provided with the long UE-specific DRX cycle
as a paging cycle of the UE.
For example, an MTC requiring reduction of power consumption, as
described in the first exemplary embodiment of the present
invention, needs a DRX cycle longer than a cell-specific DRX cycle,
which has been set for supporting general UEs. As another example,
there is a UE which supports dual radio. For a UE which supports
both 3GPP LTE and 3GPP 1X system, it is necessary to set a DRX
cycle in accordance with a system having a long DRX cycle in order
to reduce power consumption.
Therefore, the second exemplary embodiment of the present invention
provides a method for making it possible to apply a UE to apply a
UE-specific DRX cycle, which is a relatively longer cycle, in a
UE.
FIG. 8 is a flow diagram illustrating a procedure for applying a
UE-specific DRX cycle according to the second exemplary embodiment
of the present invention.
Referring to FIG. 8, in step 820, a UE 805 receives an SIB2 message
from an eNB 810, and is provided with a cell-specific DRX cycle
included in the SIB2. In this case, the UE 805 may receive a paging
through the use of the cell-specific DRX cycle received from the
eNB 810, or may receive a paging after providing a UE-specific DRX
cycle to a Mobility Management Entity (MME) 815.
In step 825, the UE 805 transfers an indication, representing that
the UE 805 does not follow the existing DRX cycle determination
scheme, and a UE-specific DRX cycle which is a long cycle desired
by the UE 805 to the MME 815, through an attach request message.
Then, in step 830, the MME 815 notifies the UE 805 that the attach
request message has been successfully received, through an attach
accept message. Thereafter, in step 835, the UE 805 compares the
cell-specific DRX cycle with the UE-specific DRX cycle, and
determines a longer cycle value of the two DRX cycles to be
applied. As an example, the UE 805 may determine the UE-specific
DRX cycle to be applied, without performing the comparing process
of step 835.
In step 840, the MME 815 provides the eNB 810 with the indication
and UE-specific DRX cycle, which have been received from the UE
805, so that the eNB 810 can calculate a DRX cycle of the UE 805.
In step 845, the eNB 810 determines a paging cycle of the UE 805 in
a manner different from the existing determination scheme, due to
the indication provided from the MME 815. That is, in step 845, the
eNB 810 compares the cell-specific DRX cycle with the UE-specific
DRX cycle, and determines a longer cycle value of the two cycles to
be applied. As an example, without performing the comparing process
of step 845, the MME 815 may apply the UE-specific DRX cycle.
Then, in step 850, the eNB 810 transmits a paging to the UE 805 in
the determined DRX cycle.
While the second exemplary embodiment of the present invention
shows an example in which the UE 805 directly provides the MME 815
with a desired DRX cycle, exemplary embodiments of the present
invention may be implemented in such a manner that the UE 805
notifies the MME 815 that the UE 805 uses a DRX cycle having a
specific cycle pattern. Also, the UE 805 may inform that the UE 805
does not follow the existing DRX cycle determination scheme,
through an indication. In this case, the UE 805 may define cycles
having various patterns in advance, and use indication values
indicating the cycles having various patterns.
Third Exemplary Embodiment
Hereinafter, according to the third exemplary embodiment of the
present invention, a method for supporting a long DRX cycle
provided in a wireless network environment where homogeneous or
heterogeneous eNBs, of which the supportable DRX cycles are
different, exist together, will be described.
In a wireless network environment for the next-generation mobile
communication, heterogeneous wireless networks can be constructed
in the same area. Such heterogeneous wireless networks existing in
the same area have a function of performing an intersystem overhead
in order to maximize the performances thereof, and can provide a UE
with a high-quality service in cooperation with each other. Also,
even in wireless networks of the same system, eNBs of various
versions may be installed for performance improvement, wherein as
the version is upgraded, new functions may be added. A UE may
receive a service in a wireless network environment where
homogeneous or heterogeneous eNBs, the maximums of offerable DRX
cycles of which are different, exist together.
Therefore, although a UE requests a network to apply a long DRX
cycle, a paging message may not be provided in the long DRX cycle
requested by the UE depending on whether or not homogeneous or
heterogeneous eNBs can support the corresponding DRX cycle.
Therefore, an UE needs to be aware of whether an eNB of a cell, on
which the UE is currently camping, can support a DRX cycle
requested by the UE, and accordingly, the operation of the UE
varies. According to the third exemplary embodiment of the present
invention, a UE's operation for supporting a long DRX cycle in the
aforementioned wireless network environment is defined. Here, a
state in which the UE is camping on a cell represents a state in
which the UE can receive control information from the cell.
A method for supporting a long DRX cycle according to the third
exemplary embodiment of the present invention is as follows.
A UE requests an eNB to apply a UE-specific DRX cycle through a
registration process (which is called an attach process in 3GPP).
When the requested UE-specific DRX cycle is equal to or longer than
a predetermined reference cycle, the UE determines whether a long
DRX cycle is supported in a corresponding cell whenever moving from
a cell to another cell in an idle state. In a cell where a long DRX
cycle is supported, a UE calculates a paging occasion through the
use of a larger value of two DRX cycles (i.e., a long DRX cycle
requested by the UE, and a cell-specific DRX cycle broadcasted in
the cell).
In contrast, in a cell where a long DRX cycle is not supported, a
UE calculates a paging occasion through the use of a smaller value
of two DRX cycles, (i.e., a UE-specific DRX cycle, which is a long
DRX cycle requested by the UE, and a cell-specific DRX cycle
broadcasted in the cell). Consequently, in a cell where a long DRX
cycle is not supported, a cell-specific DRX cycle is used at all
times.
Also, according to the third exemplary embodiment of the present
invention, in the case in which a UE requests a long DRX cycle
equal to or greater than a predetermined reference value in a
registration process and so on, when transmitting a paging message
for the UE, an MME inserts and transmits a value requested by the
UE as the UE-specific DRX cycle of the paging message with respect
to cells supporting a long DRX cycle among cells to which the
paging message must be transmitted. In contrast, with respect to
cells in which a long DRX cycle is not supported, the MME inserts
and transmits a predetermined value as the UE-specific DRX cycle of
the paging message. The predetermined value is used to allow a
resultant value to be a cell-specific DRX cycle at all times when
in a cell where a long DRX cycle is not supported uses a smaller
value of two DRX cycles (i.e., a UE-specific DRX cycle provided by
a MME, and a cell-specific DRX cycle managed by the cell according
to the related technology). Therefore, the predetermined value may
be the largest value (i.e., 2.56 seconds), of DRX cycles, other
than the long DRX cycle.
When an eNB supporting a long DRX cycle receives a paging message
from an MME, the eNB determines whether the UE-specific DRX cycle
of the paging message is a long DRX cycle, and calculates a paging
occasion, during which the paging message is to be transmitted to
the UE, by applying the UE-specific DRX cycle when the UE-specific
DRX cycle of the paging message is a long DRX cycle. In contrast,
when the UE-specific DRX cycle of the paging message is not a long
DRX cycle, the eNB calculates a paging occasion, during which the
paging message is to be transmitted to the UE, through the use of a
smaller value of two DRX cycles (i.e., a cell-specific DRX cycle,
and the UE-specific DRX cycle).
Hereinafter, the third exemplary embodiment of the present
invention will be described in detail with reference to FIG. 9.
FIG. 9 is a flow diagram illustrating the operations of a UE and an
MME according to the third exemplary embodiment of the present
invention.
Referring to FIG. 9, when powered on, an UE 905 performs an attach
process to an MME 910 in step 915. In step 915, the UE 905 provides
a desired DRX cycle to the MME 910. When an eNB 920 of cell #1 on
which the UE 905 is camping in step 925 is an eNB which cannot
provide a long DRX cycle, the eNB 920, broadcasts system
information that the eNB 920 cannot support the long DRX cycle to
the UE 905 in step 930. When the UE 905 recognizes that the eNB 920
of cell #1, on which the UE 905 is currently camping, cannot
provide the long DRX cycle requested by the UE 905, the UE 905
determines a DRX cycle by Equation 3 below in step 935. DRX
cycle=min(cell specific DRX,UE specific DRX) (3)
When the UE 905 is camping on the eNB 920, which cannot support the
long DRX cycle requested by the UE 905, the MME 910 sets a paging
DRX cycle to 2.56 seconds, which is the maximum cycle, in step 940,
and transmits a paging to the eNB 920 in step 945 when the paging
occurs.
In contrast, when an eNB 950 of cell #2 on which the UE 905 is
camping in step 955 is an eNB which can provide a long DRX cycle,
the eNB 950 broadcasts system information that the eNB 950 can
support the long DRX cycle to the UE 905 in step 960. When the UE
905 recognizes that the eNB 950 of cell #2, on which the UE 905 is
currently camping, can provide the long DRX cycle requested by the
UE 905, the UE 905 determines a DRX cycle by Equation 4 below in
step 965. DRX cycle=max(cell specific DRX,UE specific DRX) (4)
When the UE 905 is camping on the eNB 950, which can support the
long DRX cycle requested by the UE 905, the MME 910 sets a paging
DRX cycle to the long DRX cycle requested by the UE 905 in step
970, and transmits a paging to the eNB 950 in step 975 when the
paging occurs.
FIG. 10 is a flowchart illustrating the operation of a UE according
to the third exemplary embodiment of the present invention.
Before performing the operation described in FIG. 10, the UE 905
performs a registration process with the MME 910, wherein an eNB is
notified of a UE-specific DRX cycle in the registration process.
The operation of the UE 905, presented in FIG. 10, corresponds to
the operation of the UE 905 which makes a request for the
UE-specific DRX cycle (i.e., a long DRX cycle), having a value
larger than the maximum value defined in LTE Rel-8/-9. After
performing the registration process, the UE 905 transitions to an
idle state and performs an idle mode operation in general.
FIG. 10 illustrates an operation of the UE 905 for receiving a
paging message in an idle state.
Referring to FIG. 10, when the UE 905 is camping on a cell in step
1010, the UE 905 proceeds to step 1015 at which the UE 905
determines whether or not the eNB of the cell supports a long DRX
cycle. Determination as to whether the eNB of the cell supports a
long DRX cycle can be made in a manner as described in the second
exemplary embodiment of the present invention. That is, it may be
determined that the cell supports a long DRX cycle when system
information broadcasted in the cell includes a "long DRX Support
indication," and it may be determined that the cell does not
support a long DRX cycle when system information broadcasted in the
cell does not include a "long DRX Support indication." Otherwise,
whether or not a long DRX cycle is supported may be set depending
on each Tracking Area (TA). Here, the TA represents a unit area for
identifying the mobility of a UE being in an idle state, and is
constituted by a plurality of cells. When a UE being in an idle
state is camping on a cell included in a TA different from a
previous TA, the UE performs a location update procedure. For
example, when the UE 905 performs a location update procedure, the
MME 910 indicates whether or not a long DRX cycle is supported in a
corresponding TA, and the UE 905 determines that a cell supports a
long DRX cycle when the cell belongs to a TA supporting a long DRX
cycle, and determines that a cell does not support a long DRX cycle
when the cell belongs to a TA not supporting a long DRX cycle.
The UE 905 proceeds to step 1020 when a corresponding cell
corresponds to a cell not supporting a long DRX cycle, and proceeds
to step 1025 when the corresponding cell corresponds to a cell
supporting a long DRX cycle. In step 1020, the UE 905 selects a
smaller value of a cell-specific DRX cycle and a UE-specific DRX
cycle as a DRX cycle, and calculates a paging occasion by applying
the selected DRX cycle. When the UE 905 uses a long DRX cycle, the
UE-specific DRX cycle always is longer than the cell-specific DRX
cycle, so that the DRX cycle selected by the UE 905 in step 1020 is
the cell-specific DRX cycle at all times. Therefore, step 1020 may
be changed to a step in which the UE 905 selects the cell-specific
DRX cycle without taking the UE-specific DRX cycle into
consideration.
In step 1025, the UE 905 selects a larger value of a cell-specific
DRX cycle and a UE-specific DRX cycle as a DRX cycle, and
calculates a paging occasion by applying the selected DRX cycle.
When the UE 905 uses a long DRX cycle, the UE-specific DRX cycle
always is longer than the cell-specific DRX cycle, so that the DRX
cycle selected by the UE 905 in step 1025 is the UE-specific DRX
cycle. Therefore, step 1025 may be changed to a step in which the
UE 905 selects the UE-specific DRX cycle without taking the
cell-specific DRX cycle into consideration.
In step 1030, the UE 905 performs a DRX operation of determining
whether a paging message is received every paging occasion, which
has been calculated in step 1020 or 1025.
FIG. 11 is a flowchart illustrating the operation of the MME
according to the third exemplary embodiment of the present
invention.
Referring to FIG. 11, while the MME 910 performs an attach process
with the UE 905 in step 1110, the MME 910 receives a request for a
long DRX cycle from the UE 905 in step 1115.
Then, the MME 910 stores the DRX cycle and so on requested by the
UE 905, and when a paging message for the UE 905 is generated, the
MME 910 proceeds to step 1120 for determining a UE-specific DRX
cycle which is inserted into a paging message to be transmitted to
eNBs belonging to a TA, where the UE 905 is located. For example,
in step 1120, it may be determined whether the cell supports a long
DRX cycle.
Next, the MME 910 proceeds to step 1125 when an eNB of a cell
belonging to a TA in which the UE 905 is located does not support a
long DRX cycle, and proceeds to step 1130 when the corresponding
eNB supports a long DRX cycle.
In step 1125, the MME 910 inserts a predetermined value (e.g., 2.56
seconds), other than the UE-specific DRX cycle of the UE 905, into
a UE-specific DRX cycle section of the paging message to be
transmitted to the eNB, and then transmits the paging message.
In step 1130, the MME 910 inserts the UE-specific DRX cycle
requested by the UE 905 into the UE-specific DRX cycle section of
the paging message to be transmitted to the eNB, and then transmits
the paging message.
While the invention has been shown and described with reference to
certain exemplary embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims and their
equivalents.
* * * * *