U.S. patent application number 17/110357 was filed with the patent office on 2021-03-25 for methods for transmitting and receiving control channel in wireless communication systems.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. The applicant listed for this patent is Electronics and Telecommunications Research Institute. Invention is credited to Jae Young AHN, Young Jo KO, Tae Gyun NOH, Bang Won SEO.
Application Number | 20210092726 17/110357 |
Document ID | / |
Family ID | 1000005252024 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210092726 |
Kind Code |
A1 |
NOH; Tae Gyun ; et
al. |
March 25, 2021 |
METHODS FOR TRANSMITTING AND RECEIVING CONTROL CHANNEL IN WIRELESS
COMMUNICATION SYSTEMS
Abstract
A method of transmitting and receiving a control channel in a
wireless communication system is provided. A base station allocates
a data channel to a radio resource, adds start position information
of the data channel into a payload of a control channel, and
performs signaling for indication information on the start position
information added into the payload of the control channel to a
terminal. Accordingly, the legacy system and the enhanced system
can efficiently transmit a control channel.
Inventors: |
NOH; Tae Gyun; (Daejeon,
KR) ; KO; Young Jo; (Daejeon, KR) ; SEO; Bang
Won; (Daejeon, KR) ; AHN; Jae Young; (Daejeon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electronics and Telecommunications Research Institute |
Daejeon |
|
KR |
|
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejeon
KR
|
Family ID: |
1000005252024 |
Appl. No.: |
17/110357 |
Filed: |
December 3, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16398306 |
Apr 30, 2019 |
10893525 |
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17110357 |
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14986292 |
Dec 31, 2015 |
10327247 |
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16398306 |
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13529310 |
Jun 21, 2012 |
10009896 |
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14986292 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/046 20130101;
H04W 72/042 20130101; H04L 5/0094 20130101; H04W 72/0406 20130101;
H04W 4/20 20130101; H04L 5/0053 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04L 5/00 20060101 H04L005/00; H04W 4/20 20060101
H04W004/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2011 |
KR |
10-2011-0060191 |
Aug 16, 2011 |
KR |
10-2011-0081043 |
Aug 29, 2011 |
KR |
10-2011-0086737 |
Oct 10, 2011 |
KR |
10-2011-0102910 |
Jan 31, 2012 |
KR |
10-2012-0009514 |
Claims
1. A method of transmitting and receiving a control channel, which
is performed in a data transmission apparatus, the method
comprising: allocating a data channel to a radio resource; adding
start position information of the data channel into a payload of a
control channel; and signaling indication information on the start
position information added into the payload of the control channel.
Description
CLAIM FOR PRIORITY
[0001] This application is a continuation of U.S. application Ser.
No. 13/529,310, filed Jun. 21, 2012, which claims priority to
Korean Patent Application Nos. 10-2011-0060191 filed on Jun. 21,
2011, 10-2011-0081043 filed on Aug. 16, 2011, 10-2011-0086737 filed
on Aug. 29, 2011, 10-2011-0102910 filed on Oct. 10, 2011, and
10-2012-0009514 filed on Jan. 31, 2012, in the Korean Intellectual
Property Office (KIPO), the entire contents of which are hereby
incorporated by reference.
BACKGROUND
1. Technical Field
[0002] Example embodiments of the present invention relate in
general to a wireless communication system, and more specifically
to a method of transmitting and receiving a control channel in a
wireless communication system.
2. Related Art
[0003] A data transmission rate in wireless communication systems
and wired communication systems has recently become very high. In
line with this trend, the 3.sup.rd generation project partnership
long term evolution (3GPP LTE) system and the LTE-advanced system
are presently undergoing standardization.
[0004] In the 3GPP LTE system, downlink transmission is based on
orthogonal frequency division multiplexing (OFDM), and uplink
transmission is based on single frequency-frequency division
multiple access (SC-FDMA).
[0005] That is, the 3GPP system uses time-frequency resources as
fundamental physical resources, and each resource element
corresponds to one OFDM subcarrier during one OFDM symbol period.
Also, downlink subcarriers are grouped into a plurality of resource
blocks in a frequency domain, and each of the resource blocks
consists of twelve successive subcarriers.
[0006] In the 3GPP LTE system, the physical downlink shared channel
(PDSCH) is used as a physical channel for transmitting downlink
unicast data, and the physical uplink shared channel (PUSCH) is
used as a downlink physical data channel for transmitting uplink
data. Also, the physical downlink control channel (PDCCH) is used
as a downlink physical control channel for transmitting downlink
control information, such as scheduling necessary for receiving the
PDSCH, and scheduling approval for transmission in the PUSCH. The
downlink physical data channel and the downlink physical control
channel are mapped in units of subframes comprising time-frequency
resources.
[0007] When a data channel and a control channel are multiplexed in
one subframe, a base station provides start position information of
the data channel in a time domain, for which an efficient method is
required.
[0008] Moreover, when the enhanced PDCCH (ePDCCH) allocated to a
data channel region of a subframe is introduced, an efficient
control channel transmission method is necessary for both an
enhanced system capable of transmitting/receiving the ePDCCH and a
legacy system incapable of transmitting/receiving the ePDCCH.
SUMMARY
[0009] Accordingly, example embodiments of the present invention
are provided to substantially obviate one or more problems due to
limitations and disadvantages of the related art.
[0010] Example embodiments of the present invention provide a
method of efficiently transmitting and receiving a control channel
in a wireless communication system.
[0011] In some example embodiments, a method of transmitting and
receiving a control channel includes: allocating a data channel to
a radio resource; adding start position information of the data
channel into a payload of a control channel; and signaling
indication information on the start position information added into
the payload of the control channel.
[0012] The adding of start position information may include
defining a bit field for the start position information in the
payload, and adding the start position information into the bit
field.
[0013] The adding of start position information may include adding
the start position information into an unused bit field among bit
fields of the payload.
[0014] The adding of start position information may include
inserting a CRC value, which is obtained by applying a predefined
mask value to CRC of the payload, into the payload according to the
start position information.
[0015] The adding of start position information may include
inserting a result of performing a modulo operation using the
predefined mask value, an ID of a terminal, and the CRC of the
payload, into the payload according to the start position
information.
[0016] The data transmission apparatus may not allocate at least
one ID equal to a quantity of start position information to another
terminal such that the CRC values of the terminal and the other
terminal do not overlap.
[0017] The adding of start position information may include:
additionally allocating different temporary IDs to a terminal
according to the start position information; calculating a CRC
value corresponding to the start position information by using the
additionally allocated temporary IDs; and inserting the calculated
CRC value into the payload.
[0018] A temporary ID first allocated to the terminal may indicate
specific start position information, and the start position
information may be predefined between the base station and the
terminal.
[0019] The adding of start position information may include
applying different scrambling sequences to the payload of the
control channel according to the start position information.
[0020] Each of the scrambling sequences may be generated on the
basis of different sequence initial values that are predefined
between the data transmission apparatus and a terminal according to
the start position information.
[0021] In other example embodiments, a method of transmitting and
receiving a control channel in a wireless communication system,
including a plurality of data transmission apparatuses, includes:
transmitting, by at least one first data transmission apparatus, a
data channel to a terminal; and transmitting, by a second data
transmission apparatus, a control channel to the terminal, wherein
the second data transmission apparatus transmits MBSFN subframe
information as information on the at least one first data
transmission apparatus.
[0022] The transmitting of a control channel may include: defining,
by the second data transmission apparatus, a bit field for the
MBSFN subframe information in a payload of the control channel; and
adding, by the second data transmission apparatus, bitmap
information into the bit field, the bitmap information indicating
whether the at least one first data transmission apparatus includes
MBSFN subframe information.
[0023] In still other example embodiments, a control channel
transmission and reception method for transmitting an enhanced
downlink physical control channel, which is added into a section of
a downlink physical data channel and transmitted, includes:
allocating at least one downlink demodulation reference signal to a
first symbol other than a second symbol to which a downlink
cell-specific reference signal has been allocated, in a subframe,
the first symbol being included in an frequency domain to which at
least one control channel element configuring the enhanced downlink
physical control channel has been allocated; and transmitting the
subframe.
[0024] The allocating of at least one downlink demodulation
reference signal may include allocating a control channel element
instead of the downlink cell-specific reference signal to the
frequency domain to which the at least one control channel element
has been allocated, when the subframe is an MBSFN subframe.
[0025] In still other example embodiments, a control channel
transmission and reception method of a data transmission apparatus
includes: configuring a search space in which an enhanced downlink
physical control channel candidate consists of adjacent control
channel elements (CCEs), in at least one aggregation level, the
enhanced downlink physical control channel denoting a physical
control channel that is added into a downlink physical data channel
region and transmitted; and providing information of the configured
search space to a terminal.
[0026] The configuring of a search space may include: allocating
different enhanced downlink physical control channel candidates by
aggregation level; setting a CCE-unit offset between the enhanced
downlink physical control channel candidates by aggregation level;
and setting a CCE-unit offset for each terminal by aggregation
level.
[0027] In still other example embodiments, a data channel
transmission and reception method of a data transmission apparatus
includes: configuring a search space by configuring an enhanced
downlink physical control channel candidate with distributed
control channel elements (CCEs), in at least one aggregation level,
the enhanced downlink physical control channel denoting a physical
control channel that is added into a downlink physical data channel
region and transmitted; and providing information of the configured
search space to a terminal.
[0028] The configuring of a search space may include setting a
CCE-unit offset between the at least one CCE configuring the
enhanced downlink physical control channel candidate.
[0029] In still other example embodiments, a control channel
transmission and reception method of a data transmission apparatus
includes: determining a kind of a control channel for transmitting
control information and a transmission type of the control channel
according to whether to enable reception of an enhanced downlink
physical control channel and fallback control information and
control information based on a physical data transmission mode, the
enhanced downlink physical control channel denoting a physical
control channel that is added into a downlink physical data channel
region and transmitted; and configuring a control channel on the
basis of the determined kind and transmission type of the control
channel.
[0030] The determining of a kind of a control channel may include:
determining one of a downlink physical control channel and the
enhanced downlink physical control channel as the kind of the
control channel; and determining one of a localized type, in which
a search space is configured for control channel elements of the
control channel to be adjacent, and a distributed type, in which a
search space is configured for the control channel elements to be
distributed, as the transmission type of the control channel.
[0031] According to the methods of transmitting and receiving a
control channel in the wireless communication system, provided are
various methods that provide the start position information of the
data channel by using the allocation information control channel.
Also, provided are various methods of configuring an enhanced
downlink physical control channel, and provided are a search space
configuration method for a legacy system and an enhanced system and
a method of transmitting control information that is transmitted
through a search space.
[0032] Therefore, base stations and terminals can effectively
transmit and receive a control channel in both an enhanced system
with an enhanced downlink physical control channel applied thereto
and a legacy system to which the enhanced downlink physical control
channel is not applied.
BRIEF DESCRIPTION OF DRAWINGS
[0033] Example embodiments of the present invention will become
more apparent by describing in detail example embodiments of the
present invention with reference to the accompanying drawings, in
which:
[0034] FIG. 1 is a conceptual diagram illustrating an example of a
wireless communication environment in which it is necessary to
explicitly transmit start position information;
[0035] FIG. 2 is a conceptual diagram illustrating another example
of a wireless communication environment in which it is necessary to
explicitly transmit start position information;
[0036] FIG. 3 is a conceptual diagram illustrating a configuration
of a downlink subframe that is used in a method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0037] FIG. 4 is a conceptual diagram illustrating an example of a
normal subframe applied to the method of transmitting and receiving
a control channel according to an embodiment of the present
invention;
[0038] FIG. 5 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0039] FIG. 6 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0040] FIG. 7 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0041] FIG. 8 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0042] FIG. 9 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0043] FIG. 10 is a conceptual diagram illustrating another example
of a normal subframe applied to the method of transmitting and
receiving a control channel according to an embodiment of the
present invention;
[0044] FIG. 11 is a diagram illustrating a configuration example of
a localized type search space applied to the method of transmitting
and receiving a control channel according to an embodiment of the
present invention;
[0045] FIG. 12 is a diagram illustrating another configuration
example of a localized type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention;
[0046] FIG. 13 is a diagram illustrating another configuration
example of a localized type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention;
[0047] FIG. 14 is a diagram illustrating another configuration
example of a localized type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention;
[0048] FIG. 15 is a diagram illustrating a configuration example of
a distributed type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention;
[0049] FIG. 16 is a diagram illustrating another configuration
example of a distributed type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention;
[0050] FIG. 17 is a diagram illustrating another configuration
example of a distributed type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention; and
[0051] FIG. 18 is a diagram illustrating another configuration
example of a distributed type search space applied to the method of
transmitting and receiving a control channel according to an
embodiment of the present invention.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0052] The invention may have diverse modified embodiments, and
thus, example embodiments are illustrated in the drawings and are
described in the detailed description of the invention.
[0053] However, this does not limit the invention within specific
embodiments and it should be understood that the invention covers
all the modifications, equivalents, and replacements within the
idea and technical scope of the invention. Like numbers refer to
like elements throughout the description of the figures.
[0054] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises", "comprising,", "includes" and/or
"including", when used herein, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
[0055] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0056] A terminal used in the specification may refer to user
equipment (UE), a mobile station (MS), a relay node (RN), a machine
type communication (MTC) device, a mobile terminal (MT), a user
terminal (UT), a wireless terminal, an access terminal (AT), a
terminal, a subscriber unit, a subscriber station (SS), a wireless
device, a wireless communication device, a wireless
transmit/receive unit (WTRU), a mobile node, a mobile, or something
else.
[0057] Moreover, a base station used in the specification denotes a
control apparatus that controls one cell. However, a physical base
station may actually control a plurality of cells in a wireless
communication system, in which case the physical base station may
be regarded as including one or more base stations used in the
specification. For example, in the specification, different
parameters being allocated to a plurality of cells should be
understood as respective base stations allocating different values
to the cells. Also, the base station used in the specification may
be called by other names such as a base station, a node-B, an
eNode-B, a base transceiver system (BTS), an access point, a
transmission point, etc.
[0058] Hereinafter, example embodiments of the invention will be
described in detail with reference to the accompanying drawings. In
describing the invention, to facilitate a comprehensive
understanding of the invention, like numbers refer to like elements
throughout the description of the figures, and descriptions of
elements are not repeated.
[0059] The 3GPP LTE system and the LTE-advanced system use a time
domain structure that is configured with a frame including ten
subframes with a length of 1 ms.
[0060] When a data channel and a control channel are multiplexed in
one subframe, in order for a terminal to demodulate a received data
channel, a base station needs to provide start position information
of the data channel to the terminal in a time domain.
[0061] The terminal may demodulate the data channel by using the
start position information received from the base station. Here,
for example, the start position information may be an index of a
symbol configuring a subframe, and the symbol may be an OFDM symbol
or an SC-FDMA symbol.
[0062] A method in which a base station transmits start position
information to a terminal may be categorized into an implicit
method and an explicit method.
[0063] The implicit method is a method in which a base station
indirectly transmits start position information through a control
channel section, and requires that a data channel is transmitted
from a symbol just next to the control channel section. For
example, in the 3GPP system, a terminal may receive the physical
control format indicator channel (PCFICH), received from a base
station, to determine a control channel section of the base
station.
[0064] When a plurality of base stations simultaneously transmit a
data channel for a specific terminal, a specific one of the base
stations may transmit information on the base stations that
transmit the data channel to the terminal. Here, information on the
base stations may include an identifier (ID) of each of the base
stations and reference signal information of each base stations.
For example, in the 3GPP system, a base station ID may be a
physical cell ID (PCI), and the reference signal information may be
the number of cell-specific reference signal (CRS) antennas or
ports.
[0065] The terminal may determine a control channel section of each
base station that participates in transmission of the data channel,
on the basis of the information on the base stations that transmit
the data channel received from the specific base station. Also, the
terminal may determine a control channel section of a base station
that transmits a control channel. On the assumption that a data
channel allocated to the terminal is transmitted from a symbol just
next to a control channel section that has the greatest value among
the control channel section of the base station transmitting the
control channel, the terminal may demodulate the data channel.
Here, the base station that transmits the control channel to the
terminal may or may not transmit the data channel. In the 3GPP
system, the terminal may receive the PCFICH transmitted from the
base station to determine the control channel section of the base
station.
[0066] Unlike an implicit method, in an explicit method, a base
station directly transmits start position information to a
terminal. In a wireless communication system, when the implicit
method and the explicit method are simultaneously used, priority
higher than that of the implicit method may be given to the
explicit method.
[0067] A base station transmits a data channel from the same start
position as that of start position information that is transmitted
via the explicit method. A terminal demodulates the data channel on
the basis of the explicitly transmitted start position
information.
[0068] The explicit method may be categorized into a semi-static
signaling method and a dynamic signaling method.
[0069] The semi-static signaling method is a method in which a base
station transmits start position information to a terminal through
semi-static signaling, and particularly, when the start position
information is not changed for a certain time, the semi-static
signaling method is useful. For example, in the 3GPP system, the
semi-static signaling method may allow a base station to transmit
start position information to a terminal through high layer
signaling or radio resource control (RRC) signaling.
[0070] The dynamic signaling method is a method in which a base
station transmits start position information to a terminal through
a control channel that is used to transmit allocation information
of a data channel, and when the start position information is
changed for each subframe, the dynamic signaling method is useful.
Hereinafter, the control channel for transmitting the allocation
information of the data channel is referred to as an allocation
information control channel. For example, in the 3GPP system, the
allocation information control channel may be the PDCCH.
[0071] A base station may allocate a control channel and a data
channel to a subframe, and transmit start position information
through the allocation information control channel. Hereinafter, a
method of transmitting start position information through the
allocation information control channel in the method of
transmitting and receiving a control channel according to an
embodiment of the present invention will be described.
[0072] A first method includes defining a bit field representing
start position information in a payload of the allocation
information control channel. Here, the payload of the allocation
information control channel denotes a state before channel coding
is applied. The bit size of the bit field may vary according to a
quantity of start position information.
[0073] A base station adds start position information into the bit
field that is defined in the payload of the allocation information
control channel, and transmits the start position information with
the bit field added thereto to a terminal. Also, the base station
may transmit semi-static signaling, which indicates whether the
payload of the allocation information control channel includes the
bit field representing the start position information, to the
terminal. The terminal varies the size of the payload of the
allocation information control channel to demodulate the allocation
information control channel according to the semi-static signaling
received from the base station.
[0074] A second method involves using a bit field, which is defined
for some other use in the payload of the allocation information
control channel, as start position information. In a specific
condition, at least one bit field may not be used, and thus may be
reused as start position information.
[0075] A base station adds start position information into a bit
field that is not used in the payload of the allocation information
control channel, and transmits the start position information with
the bit field added thereto to a terminal. Also, the base station
may transmit semi-static signaling, which indicates whether the bit
field (which is defined for some other use in the payload of the
allocation information control channel) is to be used as the start
position information, to the terminal. The terminal demodulates the
allocation information control channel on the basis of the
semi-static signaling received from the base station.
[0076] In a third method, a predefined mask is applied differently
to cyclic redundancy check (CRC) of the payload of the allocation
information control channel according to start position
information. Here, the number of predefined masks may vary
according to a quantity of start position information. An
embodiment of the third method may be expressed as Equation
(1).
c.sub.k=(p.sub.k+x.sub.k.sup.RNTI+x.sub.k.sup.SS)mod 2, k=0,1, . .
. ,L-1
where p.sub.k denotes CRC of the payload of the allocation
information control channel, L denotes a CRC length, and
x.sub.k.sup.RNTI denotes a temporary ID (radio network temporary
identifier (RNTI) of a terminal. As an example, in the 3GPP system,
the temporary ID of the terminal may be a cell RNTI (C-RNTI), a
semi-persistent scheduling C-RNTI (SPS C-RNTI), or a temporary
C-RNTI, and one terminal may have all of the C-RNTI, the SPS
C-RNTI, and the temporary C-RNTI. x.sub.k.sup.SS denotes a CRC mask
based on start position information, and c.sub.k denotes a CRC mask
result value.
[0077] In Equation 1, x.sub.k.sup.RNTI is included as one parameter
for applying the CRC mask, in the CRC mask, but in another
embodiment of the present invention, x.sub.k.sup.RNTI may not be
included in the CRC mask of the payload of the allocation
information control channel. Also, in another embodiment of the
present invention, a mask that is not expressed in Equation (1) may
be additionally added into the CRC mask of the payload of the
allocation information control channel.
[0078] As a detailed example in which Equation (1) is applied, when
the CRC length is defined as 16 (i.e., L=16), the CRC mask based on
the start position information may be indicated as Table 1 or Table
2. In Table 1 or Table 2, the start position information is
expressed as 1, 2, and 3 as an example, but the start position
information and the CRC mask are not limited to Table 1 or Table
2.
TABLE-US-00001 TABLE 1 CRC mask of start position information Start
position information <x.sub.0.sup.SS, x.sub.1.sup.SS,
x.sub.2.sup.SS, . . . , x.sub.15.sup.SS> 1 <0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0> 2 <1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1> 3 <0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,
0, 1, 0, 1>
TABLE-US-00002 TABLE 2 CRC mask of start position information Start
position information <x.sub.0.sup.SS, x.sub.1.sup.SS,
x.sub.2.sup.SS, . . . , x.sub.15.sup.SS> 1 <0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0> 2 <0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 1> 3 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 1, 0>
[0079] In Equation (1), a modulo operation is performed with the
CRC mask (corresponding to the start position information) and the
temporary ID of the terminal. When a modulo operation result of a
CRC mask of arbitrary start position information and a temporary ID
of a specific terminal is equal to a modulo operation result of the
CRC mask of the arbitrary start position information and a
temporary ID of another terminal, a plurality of terminals can
recognize an allocation information control channel for one
specific terminal as their allocation information control
channels.
[0080] To prevent such a drawback, a base station needs to allocate
a temporary ID to a terminal such that a modulo operation result of
a temporary ID allocated to a specific terminal and a CRC mask of
arbitrary start position information differs from a modulo
operation result of a temporary ID of another terminal and the CRC
mask of the arbitrary start position information.
[0081] That is, although a base station actually allocates only one
temporary ID to a terminal, the base station does not allocate
temporary ID(s) equal to "a quantity of start position
information--1" to other terminals but rather reserves the
temporary IDs. This denotes that a base station virtually allocates
temporary ID(s) equal to a quantity of start position information.
For example, as shown in Table 1 and Table 2, when a quantity of
start position information is three, a base station actually
allocates one temporary ID to a specific terminal, and reserves two
temporary IDs without allocating the two temporary IDs to other
terminals, thereby virtually allocating three temporary IDs to the
specific terminal.
[0082] A base station may or may not use the explicit method for
transmitting start position information to a terminal. The base
station does not use a CRC mask of the start position information
for a terminal that uses only the implicit method without using the
explicit method. Therefore, the base station needs to reserve
temporary IDs that are not allocated to another terminals. That is,
it may be considered that the base station actually and virtually
allocates only one temporary ID to the terminal.
[0083] Moreover, the base station may divide a plurality of
temporary IDs into two groups, for efficiently using the temporary
IDs. One of the two groups is a temporary ID group for terminals
using the explicit method and is a group (hereinafter referred to
as a first group) that actually allocates only one temporary ID but
virtually allocates temporary IDs equal to a quantity of start
position information. The other of the two groups is a temporary ID
group for terminals using only the implicit method, and is a group
(hereinafter referred to as a second group) that actually or
virtually allocates only one temporary ID.
[0084] When the base station intends to allocate a temporary ID to
a terminal for the first time, the base station cannot determine
whether the terminal uses the explicit method or uses only the
implicit method. Therefore, the base station allocates a temporary
ID of the first or second group to the terminal. At this point, the
temporary ID of the second group may be allocated to a terminal
using the explicit method, and the temporary ID of the first group
may be allocated to a terminal using only the implicit method.
[0085] When the temporary ID of the second group is first allocated
to the terminal using the explicit method, a plurality of terminals
can recognize an allocation information control channel for one
specific terminal as their allocation information control
channels.
[0086] To prevent such a drawback, the base station knows whether
the terminal uses the explicit method or the implicit method, and
when the temporary ID of the second group is first allocated to the
terminal using the explicit method, the base station may change the
allocated temporary ID to the temporary ID of the first group.
[0087] Alternatively, when the number of temporary IDs of the first
group is insufficient, when the temporary ID of the first group is
first allocated to the terminal using only the implicit method, the
base station may change the temporary ID (which is first allocated
to the terminal using only the implicit method) to the temporary ID
of the first group.
[0088] In a fourth method, a base station additionally allocates
different temporary IDs according to start position information,
calculates a CRC value with the additionally allocated temporary
IDs, and inserts the CRC value into the payload of the allocation
information control channel. The number of temporary IDs which are
additionally allocated by the base station may vary based on a
quantity of start position information.
[0089] The base station and a terminal may predefine start position
information. A temporary ID that the base station allocates to the
terminal may be predefined as indicating specific start position
information. Subsequently, the base station may additionally
allocate a temporary ID indicating other start position information
to a terminal using the explicit method. An embodiment of the
fourth method may be expressed as Equation (2).
c.sub.k=(p.sub.k+x.sub.k.sup.RNTI,n)mod 2, k=0,1, . . . ,L-1
(2)
where p.sub.k denotes CRC of the payload of the allocation
information control channel, L denotes a CRC length, c.sub.k
denotes a CRC mask result value, and x.sub.k.sup.RNTI,n denotes a
temporary ID of a terminal based on start position information. In
an embodiment of the present invention, when it is assumed that
start position information which a base station and a terminal have
predefined is 1, 2, and 3, the temporary ID of the terminal based
on start position information may be expressed as in Table 3, for
example. A temporary ID "x.sub.k.sup.RNTI,0" that the base station
first allocates to the terminal may be predefined as being used to
indicate first start position information. Subsequently, the base
station may additionally allocate temporary IDs
"x.sub.k.sup.RNTI,1" and "x.sub.k.sup.RNTI,2" indicating the other
start position information "2" and "3" to terminals using the
explicit method.
TABLE-US-00003 TABLE 3 Start position information Temporary ID 1
x.sub.k.sup.RNTI, 0 2 x.sub.k.sup.RNTI, 1 3 x.sub.k.sup.RNTI, 2
[0090] In Table 3, the start position information is expressed as
1, 2, and 3 as an example, but the start position information and
the temporary IDs corresponding thereto are not limited to Table
3.
[0091] In a fifth method, a base station applies different
scrambling sequences to the payload of the allocation information
control channel according to start position information. The number
of scrambling sequences may vary according to a quantity of start
position information. Here, each of the scrambling sequences may be
generated by changing a sequence initial value in the same sequence
according to the start position information. Also, the scrambling
sequences may use different predefined sequences according to the
start position information. An embodiment of the fifth method may
be expressed as Equation (3).
b.sub.k=(a.sub.k+s.sub.k)mod 2, k=0,1, . . . ,A-1 (3)
where a.sub.k denotes the payload of the allocation information
control channel, A denotes a payload length of the allocation
information control channel, s.sub.k denotes a scrambling sequence,
and b.sub.k denotes a result value that is obtained by scrambling
the payload of the allocation information control channel. CRC of
the payload of the allocation information control channel may be
generated for the scrambled result value.
[0092] When one base station transmits a data channel and a control
channel to a terminal, start position information may be
transmitted in only the implicit method. However, when a base
station that transmits the data channel to the terminal differs
from a base station that transmits the control channel to the
terminal, the start position information transmitted via the
implicit method can be inaccurate.
[0093] FIG. 1 is a conceptual diagram illustrating an example of a
wireless communication environment in which it is necessary to
explicitly transmit start position information. FIG. 1, for
example, illustrates a case in which a base station transmitting
the data channel differs from a base station transmitting the
control channel.
[0094] In FIG. 1, a first base station 110 transmits a control
channel to a terminal 150, and a second base station 130 transmits
a data channel to the terminal 150.
[0095] The control channel of the first base station 110
transmitting the control channel consists of two symbols, but the
control channel of the second base station 130 transmitting the
data channel consists of three symbols.
[0096] In an environment that is as illustrated in FIG. 1, when a
base station transmits start position information via the implicit
method, the terminal 150 performs demodulation, on the assumption
that a data channel starts from the third symbol of a subframe on
the basis of the control channel of the first base station 110.
[0097] However, an actual data channel starts from the fourth
symbol of the subframe, and thus, it is quite possible that the
terminal 150 fails to demodulate the data channel.
[0098] Accordingly, in the environment of FIG. 1, a base station
may transmit start position information via the explicit method,
for transmitting accurate start position information to the
terminal 150.
[0099] FIG. 2 is a conceptual diagram illustrating another example
of a wireless communication environment in which it is necessary to
explicitly transmit start position information, and as an example,
illustrates a case in which a plurality of base stations 110 and
130 transmit a data channel to a terminal 150, and one base station
110 transmits a control channel to the terminal 150.
[0100] When a plurality of base stations transmit a data channel to
the terminal 150 and one base station transmits a control channel
to the terminal 150, the transmission of start position information
via the implicit method may be inaccurate.
[0101] In FIG. 2, the first base station 110 transmits a control
channel and a data channel to the terminal 150, and the second base
station 130 transmits a data channel to the terminal 150. The first
and second base stations 110 and 120 need to transmit the data
channel to the terminal 150 by using the same resource, and thus
transmit the data channel from the fourth symbol of a subframe with
respect to the control channel section of the second base station
130 having the longer control channel section of the control
channel sections of the first and second base stations 110 and
130.
[0102] However, the control channel of the first base station 110
transmitting the control channel consists of two symbols, and thus,
when the first base station 110 transmits start position
information via the implicit method, the terminal performs
demodulation on the assumption that the data channel starts from
the third symbol. On the other hand, an actual data channel starts
from the fourth symbol, and thus, the terminal 150 mostly fails to
demodulate the data channel.
[0103] Accordingly, in the environment of FIG. 2, a base station
may transmit start position information via the explicit method,
for transmitting accurate start position information to the
terminal 150.
[0104] An environment that requires the implicit method or the
explicit method for transmitting start position information is a
wireless communication environment in the above-described
embodiments of the present invention. However, according to the
present invention, the implicit method or the explicit method may
be applied to environments other than the above-described wireless
communication environment.
[0105] When a base station transmitting a data channel differs from
a base station transmitting a control channel as illustrated in
FIG. 1, or when a plurality of base stations transmit a data
channel as illustrated in FIG. 2, the reference signal arrangement
of a base station transmitting the control channel may differ from
the reference signal arrangement of a base station transmitting the
data channel.
[0106] The reference signal arrangement may change according to the
frequency shift of a reference signal, the number of reference
signal antennas or ports, or whether a subframe in which a data
channel is transmitted is a multicast-broadcast single frequency
network (MBSFN) subframe or not.
[0107] A base station which transmits a control channel to a
terminal may transmit MBSFN subframe information, as information on
base stations transmitting a data channel, to a terminal. Here, the
base station may transmit the MBSFN subframe information in the
semi-static signaling method or the dynamic signaling method.
[0108] First, a method of transmitting the MBSFN subframe
information through semi-static signaling is one in which a base
station transmits the MBSFN subframe information to a terminal
through semi-static signaling. For example, in the 3GPP system,
semi-static signaling may be higher layer signaling or RRC
signaling.
[0109] The MBSFN subframe information transmitted through the
semi-static signaling method may become an MBSFN subframe pattern
for a certain time. Here, it is assumed that a previous MBSFN
subframe pattern is repeated until new MBSFN subframe information
is transmitted to a terminal.
[0110] Base stations transmitting MBSFN subframe information are
base stations relevant to the transmission of a data channel, and
some of the base stations may not actually transmit the data
channel to a terminal. For example, in the 3GPP system, the base
stations may be a CoMP cooperating set.
[0111] A method of transmitting MBSFN subframe information through
the dynamic signaling method includes defining a bit field
representing the MBSFN subframe information in the payload of the
allocation information control channel, and using the defined bit
field.
[0112] In the dynamic signaling method, the MBSFN subframe
information may consist of bitmap information indicating whether
the subframe of each base station transmitting a data channel is an
MBSFN subframe or not. Here, base stations transmitting the MBSFN
subframe information are base stations that transmit a data channel
to a terminal. For example, in the 3GPP system, the base stations
may be the CoMP transmission set.
[0113] A downlink subframe may be configured by
time-division-multiplexing a downlink physical control channel and
a downlink physical data channel.
[0114] FIG. 3 is a conceptual diagram illustrating a configuration
of a downlink subframe that is used in a method of transmitting and
receiving a control channel according to an embodiment of the
present invention.
[0115] As illustrated in FIG. 3, the downlink subframe may be
configured by time-division-multiplexing the downlink physical
control channel and the downlink physical data channel, and an
enhanced downlink physical control channel may be added into a
downlink physical data channel section and transmitted.
Hereinafter, the enhanced downlink physical control channel is
referred to as an ePDCCH. In the 3GPP system, the downlink physical
control channel may be a PDCCH.
[0116] One ePDCCH may consist of one enhanced control channel
element or a plurality of enhanced control channel elements.
Hereinafter, an enhanced control channel element is referred to as
an eCCE. One eCCE may be configured with a plurality of resource
elements. Here, a resource element is the same as the resource
element, or RE, of the 3GPP system.
[0117] One virtual resource block pair may include a plurality of
eCCEs. Also, one eCCE may be included in one virtual resource
block. Here, the virtual resource block and the virtual resource
block pair are the same as a virtual resource block (VRB) and a VRB
pair in the 3GPP system, respectively.
[0118] FIGS. 4 to 10 are conceptual diagrams illustrating a
configuration of an eCCE and a downlink demodulation reference
signal when a plurality of eCCEs exist in one virtual resource
block pair.
[0119] In FIGS. 4 to 10, it is assumed that the number of OFDM
symbols of the downlink physical control channel is two, and the
number of transmission antenna ports for a downlink cell-specific
reference signal is four. An eCCE is transmitted from a position
from which the downlink cell-specific reference signal is not
transmitted in the eCCE of a subframe according to the number of
transmission antenna ports for the downlink cell-specific reference
signal.
[0120] FIG. 4 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of fourteen OFDM symbols and is a normal subframe, in a method of
transmitting and receiving a control channel according to an
embodiment of the present invention.
[0121] Moreover, FIG. 4 illustrates a configuration of an eCCE and
a downlink demodulation reference signal when three eCCEs exist in
one virtual resource block pair.
[0122] FIG. 5 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of fourteen OFDM symbols and is a normal subframe, in a method of
transmitting and receiving a control channel according to another
embodiment of the present invention, and illustrates a
configuration of an eCCE and a downlink demodulation reference
signal when three eCCEs exist in one virtual resource block
pair.
[0123] FIGS. 4 and 5 differ in position of the downlink
demodulation reference signal on the frequency axis.
[0124] FIG. 6 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of fourteen OFDM symbols and is a normal subframe, in a method of
transmitting and receiving a control channel according to another
embodiment of the present invention, and illustrates a
configuration of an eCCE and a downlink demodulation reference
signal when four eCCEs exist in one virtual resource block
pair.
[0125] When the subframe of each of FIGS. 4 to 6 is an MBSFN
subframe, a downlink cell-specific reference signal is not
transmitted in each eCCE of FIGS. 4 to 6, and an eCCE is
transmitted to the position of a downlink cell-specific reference
signal.
[0126] FIG. 7 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of fourteen OFDM symbols and is a special subframe, in a method of
transmitting and receiving a control channel according to another
embodiment of the present invention.
[0127] As an example, FIG. 7 illustrates a configuration of an eCCE
and a downlink demodulation reference signal when a downlink part
(downlink pilot time slot (DwPTS)) is configured with eleven
symbols among the fourteen OFDM symbols and includes four
eCCEs.
[0128] FIG. 8 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of fourteen OFDM symbols and is a special subframe, in a method of
transmitting and receiving a control channel according to another
embodiment of the present invention.
[0129] As an example, FIG. 8 illustrates a configuration of an eCCE
and a downlink demodulation reference signal when a downlink part
(DwPTS) is configured with nine symbols among the fourteen OFDM
symbols and includes four eCCEs.
[0130] FIG. 9 illustrates a configuration of an eCCE and a downlink
demodulation reference signal when one downlink subframe consists
of twelve OFDM symbols and is a normal subframe, in a method of
transmitting and receiving a control channel according to another
embodiment of the present invention,
[0131] As an example, FIG. 9 illustrates a configuration of an eCCE
and a downlink demodulation reference signal when four eCCEs exist
in one virtual resource block pair. For example, when a subframe is
an MBSFN subframe, the downlink cell-specific reference signal of
FIG. 9 is not transmitted, and an eCCE is transmitted to the
position of the downlink cell-specific reference signal.
[0132] FIG. 10 illustrates a configuration of an eCCE and a
downlink demodulation reference signal when one downlink subframe
consists of twelve OFDM symbols and is a special subframe, in a
method of transmitting and receiving a control channel according to
another embodiment of the present invention.
[0133] As an example, FIG. 10 illustrates a configuration of an
eCCE and a downlink demodulation reference signal when a downlink
part (DwPTS) of the special subframe is configured with eight
symbols among the fourteen OFDM symbols, and the configuration of
the eCCE and downlink demodulation reference signal may change
according to the number of OFDM symbols configuring the downlink
part.
[0134] In the above-described configuration of the subframe, when a
subframe is a normal subframe or when a subframe is an MBSFN
subframe, a zeropower channel state information reference signal
(CSI-RS) and/or a non-zeropower channel state information reference
signal (CSI-RS) may be disposed in an eCCE, in which case an eCCE
is not transmitted from the position of the zeropower CSI-RS and/or
the position of non-zeropower CSI-RS.
[0135] An ePDCCH may consist of one eCCE or a plurality of eCCEs.
Hereinafter, the number of eCCEs configuring one ePDCCH is referred
to as an aggregation level. For example, the aggregation level may
consist of a set such as 1, 2, 4, 8 or the like. Hereinafter, a set
of eCCEs that a terminal needs to search and that is a region in
which ePDCCH candidates are transmittable is referred to as a
search space.
[0136] The search space may change according to terminals or the
aggregation level of an ePDCCH. Also, since the format of an ePDCCH
is not known to a terminal in advance, the terminal may change the
aggregation level to find an ePDCCH (which is transmitted from a
base station) through blind decoding, and the number of blind
decodings may vary according to the aggregation level.
[0137] The search space may be a localized type search space or a
distributed type search space according to terminals. A base
station may inform a terminal of whether the search space is the
localized type search space or the distributed type search space
through higher layer signaling for each terminal. In the 3GPP
system, higher layer signaling for each terminal may be RRC
signaling.
[0138] The localized type search space may be configured as
follows, for obtaining a frequency selective scheduling gain.
[0139] First, in all aggregation levels (for example, 1, 2, 4, 8),
each ePDCCH may consist of adjacent eCCEs. Such an operation may be
performed by a base station. It is assumed by a terminal that the
same precoding is applied to a plurality of eCCEs in each ePDCCH
candidate. Also, the base station may set an eCCE-unit offset
between ePDCCH candidates, and the offset may change according to
aggregation level. Here, the offset may be a positive integer
including zero.
[0140] Moreover, a base station may set an eCCE-unit offset for
each terminal, for efficiently using the resource of the localized
type search space. Here, the offset for each terminal may be a
positive integer including zero.
[0141] When an aggregation level is L, i.sub.offset,L indicating
the offset for each terminal may be expressed as Equation (4).
i.sub.offset,L=(ID)mod K.sub.offset,L (4)
where ID denotes an identifier that a base station gives to a
terminal. In the 3GPP system, the identifier (ID) is an RNTI, and
may be a C-RNTI or an SPS C-RNTI. K.sub.offset,L denotes the number
of offsets between ePDCCH candidates when an aggregation level is
L, and may have different values according to the aggregation level
"L".
[0142] A base station may inform each terminal of an offset for
each terminal through higher layer signaling for each terminal. In
the 3GPP system, higher layer signaling for each terminal may be
RRC signaling. Also, the base station may set the same offset for
each terminal or set different offsets according to aggregation
level.
[0143] Higher layer signaling for each terminal may include an
offset for each terminal by aggregation level, and the same offset
for each terminal may be included in all aggregation levels. Here,
an offset for each terminal may be zero according to aggregation
level, and the offset for each terminal of an aggregation level
whose offset for each terminal is zero may not be included in
higher layer signaling for each terminal.
[0144] A base station may inform a terminal of one virtual resource
block pair or virtual resource block through higher layer signaling
for each terminal, in order for the terminal to determine a search
space. Also, the base station may inform the terminal of one
virtual resource block set consisting of a plurality of virtual
resource blocks or a plurality of virtual resource block pairs
through higher layer signaling for each terminal, in order for the
terminal to determine the search space.
[0145] The mapping of the physical resource block of a virtual
resource block may be based on a resource allocation type "0", a
resource allocation type "1", and a resource allocation type "2"
that are defined in the standard of the 3GPP system. In the 3GPP
system, higher layer signaling for each terminal may be RRC
signaling. When a base station may inform a terminal of one virtual
resource block set consisting of a plurality of virtual resource
blocks or a plurality of virtual resource block pairs through
higher layer signaling for each terminal in order for the terminal
to determine a search space, the localized type search space may be
set as expressed in Equation (5).
n.sub.eCC.sup.ePDCCH=(L(mK.sub.offset,L+i.sub.offset,L)+i)mod N
where i=0,1, . . . ,L-1 and m=0,1, . . . ,M.sub.L-1 (5)
where n.sub.eCCE.sup.ePDCCH denotes the index of an eCCE in which
an ePDCCH candidate "m" having an aggregation level "L" is
disposed. N denotes the number of eCCEs configuring one virtual
resource block set that a base station transmits to a terminal, and
an eCCE index in a virtual resource block set is 0, 1, . . . , N-1.
L denotes the aggregation level of an eCCE, m denotes the index of
an ePDCCH candidate, and i.sub.offset,L denotes an offset for each
terminal when an aggregation level is L. K.sub.offset,L denotes an
offset between ePDCCH candidates when the aggregation level is L,
and i denotes an eCCE index configuring an ePDCCH candidate having
an aggregation level "L". Also, M.sub.L denotes the number of
ePDCCH candidates having an aggregation level "L". As expressed in
Equation (5), respective ePDCCH candidates may be transmitted to L
number of successive eCCEs.
[0146] Alternatively, when a base station may inform a terminal of
one virtual resource block pair or virtual resource block in order
for the terminal to determine a search space, the localized type
search space may be set as expressed in Equation (6).
n.sub.eCCE.sup.ePDCCH=(L(mK.sub.offset,L+i.sub.offset,L)+i) where
i=0,1, . . . ,L-1 and m=0,1, . . . ,M.sub.L-1 (6)
where n.sub.eCCE.sup.ePDCCH denotes the index of an eCCE in which
an ePDCCH candidate "m" having an aggregation level "L" is
disposed. One virtual resource block pair or virtual resource block
of which a base station has informed a terminal corresponds to a
position in which an eCCE "0" that is the lowest index in a search
space is mapped, and a plurality of virtual resource blocks or
virtual resource block pairs having the second greatest value after
the index of the virtual resource block pair or virtual resource
block of which the base station has informed the terminal configure
a search space successively. An ePDCCH in which i.sub.offset,L=0
and m=0 is transmitted to the virtual resource block pair or
virtual resource block of which the base station has informed the
terminal. L denotes the aggregation level of an eCCE, m denotes the
index of an ePDCCH candidate, and i.sub.offset,L denotes an offset
for each terminal when an aggregation level is L. K.sub.offset,L
denotes an offset between ePDCCH candidates when the aggregation
level is L, and i denotes an eCCE index configuring an ePDCCH
candidate having an aggregation level "L". As expressed in Equation
(6), respective ePDCCH candidates may be transmitted to L number of
successive eCCEs.
[0147] FIGS. 11 to 14 are conceptual diagrams illustrating a
configuration example of a localized type search space in a method
of transmitting and receiving a control channel according to an
embodiment of the present invention.
[0148] FIG. 11 is a diagram illustrating a configuration example of
a localized type search space in a method of transmitting and
receiving a control channel according to an embodiment of the
present invention.
[0149] In FIG. 11, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be
M.sub.1=M.sub.2=6 and M.sub.4=M.sub.8=2. Offsets between ePDCCH
candidates are assumed to be K.sub.offset,1=4,
K.sub.offset,2=K.sub.offset,4=2, and K.sub.offset,8=1. An offset
for each terminal is assumed to be
i.sub.offset,1=i.sub.offset,2=i.sub.offset,4=i.sub.offset,8=0.
[0150] FIG. 12 is a diagram illustrating a configuration example of
a localized type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0151] In FIG. 12, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be
M.sub.1=M.sub.2=6 and M.sub.4=M.sub.8=2. Offsets between ePDCCH
candidates are assumed to be K.sub.offset,1=4,
K.sub.offset,2=K.sub.offset,4=2, and K.sub.offset,8=1. An offset
for each terminal is assumed to be i.sub.offset,1=2,
i.sub.offset,2=i.sub.offset,4=1, and i.sub.offset,8=0.
[0152] FIG. 13 is a diagram illustrating a configuration example of
a localized type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0153] In FIG. 13, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be M.sub.1=8,
M.sub.2=4, and M.sub.4=M.sub.8=2. Offsets between ePDCCH candidates
are assumed to be K.sub.offset,1=K.sub.offset,2=K.sub.offset,4=2,
and K.sub.offset,8=1. An offset for each terminal is assumed to be
i.sub.offset,1=i.sub.offset,2=i.sub.offset,4=i.sub.offset,8=0.
[0154] FIG. 14 is a diagram illustrating a configuration example of
a localized type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0155] In FIG. 14, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be M.sub.1=8,
M.sub.2=4, and M.sub.4=M.sub.8=2. Offsets between ePDCCH candidates
are assumed to be K.sub.offset,1=K.sub.offset,2=K.sub.offset,4=2,
and K.sub.offset,8=1. An offset for each terminal is assumed to be
i.sub.offset,1=i.sub.offset,2=i.sub.offset,4=1, and
i.sub.offset,8=0.
[0156] The distributed type search space may be configured as
follows, for obtaining a frequency diversity gain.
[0157] First, in all aggregation levels (for example, 1, 2, 4, 8),
each ePDCCH may consist of distributed eCCEs that are not adjacent
to one another. An eCCE-unit offset between a plurality of eCCEs
configuring each ePDCCH candidate is necessary for configuring each
ePDCCH candidate with distributed eCCEs, and the offset may change
according to aggregation level. Here, the offset may be a positive
integer including zero.
[0158] It is assumed by a terminal that different precodings are
applied to a plurality of eCCEs included in each ePDCCH
candidate.
[0159] Moreover, there may be an eCCE-unit offset between ePDCCH
candidates, and the offset may change according to aggregation
level. Here, the offset may be a positive integer including
zero.
[0160] Moreover, there may be an eCCE-unit offset for each
terminal, for efficiently using the distributed type search space.
Here, the offset for each terminal may be a positive integer
including zero. The offset for each terminal in the distributed
type search space may be configured as expressed in Equation (4),
as in the above-described offset for each terminal.
[0161] A base station may inform a terminal of an offset for each
terminal through higher layer signaling for each terminal. In the
3GPP system, higher layer signaling for each terminal may be RRC
signaling. Offsets for respective terminals may be the same or may
differ. Higher layer signaling for each terminal may include an
offset for each terminal by aggregation level, and the same one
offset for each terminal may be included in all aggregation levels.
An offset for each terminal may be zero according to aggregation
level, and the offset for each terminal of an aggregation level
whose offset for each terminal is zero may not be included in
higher layer signaling for each terminal.
[0162] A base station may inform a terminal of one virtual resource
block pair or virtual resource block through higher layer signaling
for each terminal, in order for the terminal to determine a search
space. Also, the base station may inform the terminal of one
virtual resource block set consisting of a plurality of virtual
resource blocks or a plurality of virtual resource block pairs
through higher layer signaling for each terminal, in order for the
terminal to determine the search space.
[0163] The mapping of the physical resource block of a virtual
resource block may be based on a resource allocation type "0", a
resource allocation type "1", and a resource allocation type "2"
that are defined in the standard of the 3GPP system. In the 3GPP
system, higher layer signaling for each terminal may be RRC
signaling.
[0164] When a base station may inform a terminal of one virtual
resource block set consisting of a plurality of virtual resource
blocks or a plurality of virtual resource block pairs through
higher layer signaling for each terminal in order for the terminal
to determine a search space, the distributed type search space may
be set as expressed in Equation (7).
n.sub.eCCE.sup.ePDCCH=(mK.sub.offset,L+i.sub.offset,L+iD.sub.offset,L)mo-
d N where i=0,1, . . . ,L-1 and m=0,1, . . . ,M.sub.L-1 (7)
where n.sub.eCCE.sup.ePDCCH denotes the index of an eCCE in which
an ePDCCH candidate "m" having an aggregation level "L" is
disposed. N denotes the number of eCCEs configuring one virtual
resource block set that a base station transmits to a terminal, and
an eCCE index in a virtual resource block set is 0, 1, . . . , N-1.
L denotes the aggregation level of an eCCE, and m denotes the index
of an ePDCCH candidate. Also, i.sub.offset,L denotes an offset for
each terminal when an aggregation level is L. K.sub.offset,L
denotes an offset between ePDCCH candidates when the aggregation
level is L.
[0165] D.sub.offset,L denotes an offset between a plurality of
eCCEs in each ePDCCH candidate when an aggregation level is L. i
denotes an eCCE index configuring an ePDCCH candidate having an
aggregation level "L". Respective ePDCCH candidates may be
transmitted to L number of distributed eCCEs.
[0166] Moreover, when a base station may inform a terminal of one
virtual resource block pair or virtual resource block in order for
the terminal to determine a search space, the distributed type
search space may be set as expressed in Equation (8).
n.sub.eCCE.sup.ePDCCH=mK.sub.offset,L+i.sub.offset,L+iD.sub.offset,L
where i=0,1, . . . ,L-1 and m=0,1, . . . ,M.sub.L-1 (8)
where n.sub.eCCE.sup.ePDCCH denotes the index of an eCCE in which
an ePDCCH candidate "m" having an aggregation level "L" is
disposed. One virtual resource block pair or virtual resource block
of which a base station has informed a terminal corresponds to a
position in which an eCCE "0" that is the lowest index in a search
space is mapped, and a plurality of virtual resource blocks or
virtual resource block pairs having the second greatest value after
the index of the virtual resource block pair or virtual resource
block of which the base station has informed the terminal configure
a search space successively.
[0167] An ePDCCH in which i.sub.offset,L=0 and m=0 is transmitted
to the virtual resource block pair or virtual resource block of
which the base station has informed the terminal. L denotes the
aggregation level of an eCCE, m denotes the index of an ePDCCH
candidate, and i.sub.offset,L denotes an offset for each terminal
when an aggregation level is L. K.sub.offset,L denotes an offset
between ePDCCH candidates when the aggregation level is L. Also,
D.sub.offset,L denotes an offset between a plurality of eCCEs in
each ePDCCH candidate when an aggregation level is L. i denotes an
eCCE index configuring an ePDCCH candidate having an aggregation
level "L". As expressed in Equation (8), respective ePDCCH
candidates may be transmitted to L number of distributed eCCEs.
[0168] FIGS. 15 to 18 are conceptual diagrams illustrating a
configuration example of a distributed type search space in a
method of transmitting and receiving a control channel according to
an embodiment of the present invention.
[0169] FIG. 15 is a diagram illustrating a configuration example of
a distributed type search space in a method of transmitting and
receiving a control channel according to an embodiment of the
present invention.
[0170] In FIG. 15, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be
M.sub.1=M.sub.2=6 and M.sub.4=M.sub.8=2. Offsets between ePDCCH
candidates are assumed to be K.sub.offset,1=4,
K.sub.offset,2=K.sub.offset,4=2, and K.sub.offset,8=1. Also,
offsets between a plurality of eCCEs in an ePDCCH candidate are
assumed to be D.sub.offset,1=1, D.sub.offset,2=12,
D.sub.offset,4=4, and D.sub.offset,8=2, and an offset for each
terminal is assumed to be
D.sub.offset,1=i.sub.offset,2=i.sub.offset,4=i.sub.offset,8=0.
[0171] FIG. 16 is a diagram illustrating a configuration example of
a distributed type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0172] In FIG. 16, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be
M.sub.1=M.sub.2=6 and M.sub.4=M.sub.8=2. Offsets between ePDCCH
candidates are assumed to be K.sub.offset,1=4,
K.sub.offset,2=K.sub.offset,4=2, and K.sub.offset,8=1. Also,
offsets between a plurality of eCCEs in an ePDCCH candidate are
assumed to be D.sub.offset,1.sup.=1, D.sub.offset,2=12,
D.sub.offset,4=4, and D.sub.offset,8=2, and an offset for each
terminal is assumed to be i.sub.offset,1=2,
i.sub.offset,2=i.sub.offset,4=1, and i.sub.offset,8=0.
[0173] FIG. 17 is a diagram illustrating a configuration example of
a distributed type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0174] In FIG. 17, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be M.sub.1=8,
M.sub.2=4, and M.sub.4=M.sub.8=2. Offsets between ePDCCH candidates
are assumed to be K.sub.offset,1=K.sub.offset,2=K.sub.offset,4=2,
and K.sub.offset,8=1. Also, offsets between a plurality of eCCEs in
an ePDCCH candidate are assumed to be D.sub.offset,1=1,
D.sub.offset,2=8, D.sub.offset,4=4, and D.sub.offset,8=2, and an
offset for each terminal is assumed to be
i.sub.offset,1=i.sub.offset,2=i.sub.offset,4=i.sub.offset,8=0.
[0175] FIG. 18 is a diagram illustrating a configuration example of
a distributed type search space in a method of transmitting and
receiving a control channel according to another embodiment of the
present invention.
[0176] In FIG. 18, the aggregation level of an eCCE is assumed to
be L=1, 2, 4, and 8. In the drawing, a number illustrated in each
ePDCCH candidate denotes the index "m" of each ePDCCH candidate.
Also, the number of ePDCCH candidates is assumed to be M.sub.1=8,
M.sub.2=4, and M.sub.4=M.sub.8=2. Offsets between ePDCCH candidates
are assumed to be K.sub.offset,1=K.sub.offset,2=K.sub.offset,4=2,
and K.sub.offset,8=1. Also, offsets between a plurality of eCCEs in
an ePDCCH candidate are assumed to be D.sub.offset,1=1,
D.sub.offset,2=8, D.sub.offset,4=4, and D.sub.offset,8=2, and an
offset for each terminal is assumed to be
i.sub.offset,1=i.sub.offset,2=i.sub.offset,4=1, and
i.sub.offset,8=0.
[0177] As described above, the ePDCCH supports localized
transmission and distributed transmission, but the downlink
physical control channel supports only the distributed type. Also,
the search space of a terminal may be divided into a
terminal-common (UE-common) search space and a terminal-specific
(UE-specific) search space. In the terminal-common search space a
terminal may receive control information for a plurality of
terminals, but in the terminal-specific search space a terminal may
receive control information for one specific terminal.
[0178] In a legacy system capable of transmitting and receiving
only the downlink physical control channel, a base station
transmits the control information of the terminal-common search
space and the control information of the terminal-specific search
space through only the downlink physical control channel. On the
other hand, in an enhanced system capable of transmitting and
receiving the ePDCCH, a base station may transmit the control
information of the terminal-common search space and the control
information of the terminal-specific search space through the
downlink physical control channel or the ePDCCH. Hereinafter, a
terminal incapable of transmitting and receiving the ePDCCH is
referred to as a legacy terminal, and a terminal capable of
transmitting and receiving the ePDCCH is referred to as an enhanced
terminal.
[0179] The enhanced system supports the legacy terminal as well as
the enhanced terminal, and thus, in the enhanced system, a base
station and a terminal may transmit and receive the downlink
physical control channel.
[0180] A transmission type and a channel for transmitting the
control information of a search space in the enhanced system in
which the downlink physical control channel and the ePDCCH have
been defined will be described in detail below. Also, an operation
in which the enhanced terminal receives the control information of
the search space will be described in detail. In the
terminal-common search space a terminal may receive common control
information for both the enhanced terminal and the legacy terminal.
Accordingly, a base station may transmit the common control
information through the downlink physical control channel, for
supporting the legacy terminal. Depending on system configuration
and environment, the base station may not transmit the downlink
physical control channel in a specific component carrier. Also, the
base station may transmit the downlink physical control channel,
but the enhanced terminal may not receive the downlink physical
control channel. In this case, the base station may transmit the
common control information through the ePDCCH, for the enhanced
terminal. As described above, the enhanced terminal may or may not
receive the downlink physical control channel depending on system
configuration and environment.
[0181] A method in which the enhanced terminal receives a channel
for transmitting the common control information may be largely
categorized into three methods.
[0182] A first method is a method in which the enhanced terminal
receives common control information through only the downlink
physical control channel. A second method is a method in which the
enhanced terminal receives common control information through only
the ePDCCH. To this end, a base station may transmit the same
common control information through the downlink physical control
channel or the ePDCCH. A third method is a method in which a base
station establishes a channel (downlink physical control channel or
ePDCCH) through which common control information is received, to a
terminal.
[0183] In the terminal-common search space a terminal may receive
common control information for a plurality of terminals, and thus,
distributed transmission is more effective than localized
transmission. Accordingly, when a base station transmits the common
control information through the ePDCCH, the ePDCCH may have a
distributed type.
[0184] In the terminal-specific search space a terminal may receive
two kinds of control information. One of the two kinds of control
information is control information based on the transmission mode
of a physical data channel, and the other is fallback control
information irrelevant to the transmission mode of the physical
data channel. For example, in the 3GPP system, the physical data
channel may be a PDSCH or a PUSCH, and the fallback control
information may be a downlink control information (DCI) format lA
or a DCI format 0.
[0185] A base station may transmit control information that is
transmitted in the terminal-specific search space, through the
downlink physical control channel or the ePDCCH. The downlink
physical control channel enables distributed transmission, but the
ePDCCH enables localized transmission or distributed
transmission.
[0186] A transmission type effective for control information based
on the transmission mode of the physical data channel may be the
localized type or the distributed type according to the
transmission mode of the physical data channel. A transmission type
effective for the fallback control information is the distributed
type in general, but may be the localized type depending on
conditions.
[0187] A transmission scheme may be classified as shown in Table 4,
according to the kinds of control information, the channels for
transmitting the control information, and the transmission types of
the channels through which the control information is
transmitted.
TABLE-US-00004 TABLE 4 Control information based on physical data
Fallback control transmission mode information First trans-
Downlink physical control Downlink physical control mission scheme
channel-distributed type channel-distributed type Second trans-
ePDCCH-distributed type ePDCCH-distributed type mission scheme
Third trans- ePDCCH-localized type Downlink physical control
mission scheme channel-distributed type Fourth trans-
ePDCCH-localized type ePDCCH-distributed type mission scheme Fifth
trans- ePDCCH-localized type ePDCCH-localized type mission
scheme
[0188] All or some of the five transmission schemes classified in
Table 4 may be defined in the enhanced system.
[0189] Hereinafter, a plurality of transmission schemes capable of
being defined in the enhanced system will be described in
detail.
[0190] The first transmission scheme is necessary when the enhanced
terminal communicates with a base station for the legacy system,
and thus may be included in the enhanced system.
[0191] The second transmission scheme uniquely has the distributed
type using the ePDCCH, and thus may be included in the enhanced
system.
[0192] The following three methods may be used for adding the third
to fifth transmission schemes into the enhanced system.
[0193] In a first method, only the third and fourth transmission
schemes are added into the enhanced system.
[0194] In a second method, only the fourth transmission scheme is
added into the enhanced system.
[0195] In a third method, only the fifth transmission scheme is
added into the enhanced system. Here, in the first and second
methods, the transmission types of channels for transmitting
control information differ according to the kind of the control
information (fallback control information or control information
based on the physical data transmission mode). Accordingly, the
terminal-specific search space may be divided into a search space
for control information based on the physical data transmission
mode, and a search space for the fallback control information. A
base station may transmit resource block information, which
configures each terminal-specific search space based on control
information, to a terminal through higher layer signaling. In each
of the search spaces, the number of blind decodings performed by
the enhanced terminal may differ. For the ePDCCH, the number of
blind decodings may be implicitly determined according to the size
of a resource block configuring a search space.
[0196] Moreover, in the first method, the fallback control
information may be transmitted through the downlink physical
control channel or the ePDCCH, and thus, a base station may
transmit establishment information on a channel, through which the
fallback control information is transmitted, to a terminal through
higher layer signaling.
[0197] The third method has only the ePDCCH-localized type as the
transmission type of a channel through which control information is
transmitted, irrespective of the kind of the control information.
Accordingly, only one terminal-specific search space is required to
be defined. A base station may transmit resource block information
that configures the terminal-specific search space to a terminal
through higher layer signaling.
[0198] While example embodiments of the present invention and their
advantages have been described in detail, it should be understood
that various changes, substitutions and alterations may be made
herein without departing from the scope of the invention.
* * * * *