U.S. patent application number 16/535551 was filed with the patent office on 2020-10-08 for method for receiving nrs and nb-iot device thereof.
The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Joonkui AHN, Seunggye HWANG, Changhwan PARK, Seokmin SHIN, Suckchel YANG.
Application Number | 20200322200 16/535551 |
Document ID | / |
Family ID | 1000005104343 |
Filed Date | 2020-10-08 |
![](/patent/app/20200322200/US20200322200A9-20201008-D00000.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00001.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00002.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00003.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00004.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00005.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00006.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00007.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00008.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00009.png)
![](/patent/app/20200322200/US20200322200A9-20201008-D00010.png)
View All Diagrams
United States Patent
Application |
20200322200 |
Kind Code |
A9 |
HWANG; Seunggye ; et
al. |
October 8, 2020 |
METHOD FOR RECEIVING NRS AND NB-IOT DEVICE THEREOF
Abstract
One disclosure of the present specification proposes a method
for receiving a Narrowband Reference Signal (NRS) by a Narrow band
Internet of Things (NB-IoT) device. The method may comprise
receiving the NRS on at least one or more orthogonal frequency
division multiplexing (OFDM) symbols. The one or more OFDM symbols
are in a time division duplex (TDD) subframe. If the TDD subframe
corresponds to a TDD special subframe, the one or more OFDM symbols
for receiving the NRS is determined based on which TDD special
subframe configuration index among a plurality of TDD special
configuration indexes is used by the TDD special subframe.
Inventors: |
HWANG; Seunggye; (Seoul,
KR) ; AHN; Joonkui; (Seoul, KR) ; PARK;
Changhwan; (Seoul, KR) ; YANG; Suckchel;
(Seoul, KR) ; SHIN; Seokmin; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20190363920 A1 |
November 28, 2019 |
|
|
Family ID: |
1000005104343 |
Appl. No.: |
16/535551 |
Filed: |
August 8, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16249569 |
Jan 16, 2019 |
10425265 |
|
|
16535551 |
|
|
|
|
PCT/KR2018/007770 |
Jul 10, 2018 |
|
|
|
16249569 |
|
|
|
|
62531363 |
Jul 12, 2017 |
|
|
|
62674562 |
May 21, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 4/70 20180201; H04L
27/2613 20130101; H04L 1/00 20130101; H04L 5/22 20130101; H04L
5/0007 20130101; H04L 5/143 20130101; H04L 5/1469 20130101; H04L
5/005 20130101; H04L 12/4612 20130101; H04L 27/2602 20130101 |
International
Class: |
H04L 27/26 20060101
H04L027/26; H04L 12/46 20060101 H04L012/46; H04L 5/22 20060101
H04L005/22; H04L 5/14 20060101 H04L005/14; H04L 5/00 20060101
H04L005/00; H04L 1/00 20060101 H04L001/00; H04W 4/70 20060101
H04W004/70 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2018 |
KR |
10-2018-0038747 |
Claims
1. A method of receiving a narrowband reference signal (NRS), the
method performed by a narrowband internet of things (NB-IoT) device
and comprising: determining information regarding a time division
duplex (TDD) special subframe configuration, among a plurality of
TDD special subframe configurations that each configures a
plurality of downlink (DL) orthogonal frequency division
multiplexing (OFDM) symbols and at least one uplink (UL) OFDM
symbol within a TDD special subframe; and receiving the NRS on at
least one DL OFDM symbol among the plurality of DL OFDM symbols
within the TDD special subframe, wherein a symbol location of the
at least one DL OFDM symbol for receiving the NRS is determined
based on the TDD special subframe configuration.
2. The method of claim 1, wherein the TDD special subframe
comprising the at least one DL OFDM symbol for receiving the NRS
uses at least one of TDD special configuration indexes 1, 2, 3, 4,
6, 7, 8, or 9.
3. The method of claim 1, wherein the at least one DL OFDM symbol
for receiving the NRS comprises at least one of a 6th symbol or a
7th symbol in the TDD special subframe.
4. The method of claim 1, wherein the NRS is not received on at
least one TDD special subframe using TDD special configuration
indexes 0 and 5.
5. The method of claim 1, wherein the at least one DL OFDM symbol
for receiving the NRS comprises at least one of a 2nd symbol or a
3rd symbol in the TDD special subframe.
6. The method of claim 1, wherein the NRS on the TDD special
subframe is generated based on a normal downlink subframe.
7. The method of claim 1, further comprising: receiving a second
reference signal (RS) in a second TDD special subframe using a TDD
special subframe configuration index 10.
8. The method of claim 7, wherein based on an NB-IoT operation mode
being an inband-same PCI mode representing an inband-same physical
cell identifier (PCI): the second RS comprises a cell-specific
reference signal (CRS).
9. The method of claim 8, wherein based on the NB-IoT operation
mode being the inband-same PCI representing the inband-same PCI: a
location of a resource element (RE) to which the NRS is mapped is
different from a location of a RE to which the CRS is mapped.
10. The method of claim 8, wherein based on a NB-IoT operation mode
being an inband-different PCI mode representing an inband-different
PCI: the second RS comprises an NRS.
11. The method of claim 10, wherein based on the NB-IoT operation
mode being the inband-different PCI representing the
inband-different PCI: an RE to which the CRS is to be mapped is
used as a blank RE.
12. The method of claim 7, wherein the second TDD special subframe
using the TDD special subframe configuration index 10 is designated
as a valid subframe.
13. The method of claim 11, wherein the second TDD special subframe
using the TDD special subframe configuration index 10 comprises a
downlink pilot time slot (DwPTS) in which a downlink data is to be
received.
14. The method of claim 1, wherein the TDD special subframe in
which the NRS is received is a valid subframe in which a downlink
data is to be received.
15. A narrowband internet of things (NB-IoT) device configured to
receive a narrowband reference signal (NRS), the NB-IoT device
comprising: a transceiver; at least one processor; and at least one
computer memory operably connectable to the at least one processor
and storing instructions that, when executed by the at least one
processor, perform operations comprising: determining information
regarding a time division duplex (TDD) special subframe
configuration, among a plurality of TDD special subframe
configurations that each configures a plurality of downlink (DL)
orthogonal frequency division multiplexing (OFDM) symbols and at
least one uplink (UL) OFDM symbol within a TDD special subframe;
and receiving, via the transceiver, the NRS on at least one DL OFDM
symbol among the plurality of DL OFDM symbols within the TDD
special subframe, wherein a symbol location of the at least one
OFDM symbol for receiving the NRS is determined based on the TDD
special subframe configuration.
16. The method of claim 1, wherein the TDD special subframe
comprises at least three DL OFDM symbols for receiving the NRS, and
uses at least one of TDD special configuration indexes 1, 2, 3, 4,
6, 7, 8, or 9.
17. The method of claim 1, wherein for a first TDD special subframe
configuration among the plurality of TDD special subframe
configurations, the symbol location of the at least one DL OFDM
symbol comprises a third symbol in the TDD special subframe, and
wherein for a second TDD special subframe configuration among the
plurality of TDD special subframe configurations, the symbol
location of the at least one DL OFDM symbol comprises a sixth
symbol in the TDD special subframe.
18. The method of claim 1, wherein the TDD special subframe
configuration relates to a TDD special subframe that comprises a
downlink pilot time slot (DwPTS), a guard period (GP), and an
uplink pilot time slot (UpPTS).
19. The method of claim 1, wherein at least one of a number of DL
OFDM symbols or a number of UL OFDM symbols is different for
different TDD special subframe configurations among the plurality
of TDD special subframe configurations.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 16/249,569, filed on Jan. 16, 2019, which claims benefit of
International Application No. PCT/KR2018/007770, filed on Jul. 10,
2018, which claims the benefit of U.S. Provisional Applications No.
62/531,363 filed on Jul. 12, 2017, No. 62/674,562 filed on May 21,
2018, and Korean Patent Application No. 10-2018-0038747 filed on
Apr. 3, 2018, the contents of which are all hereby incorporated by
reference herein in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to mobile communication.
Related Art
[0003] In recent years, communication, i.e., machine type
communication (MTC), occurring between devices or between a device
and a server without a human interaction, i.e., a human
intervention, is actively under research. The MTC refers to the
concept of communication based on an existing wireless
communication network used by a machine device instead of a user
equipment (UE) used by a user. Meanwhile, since the existing LTE
system has been designed for the purpose of supporting high-speed
data communication, it has been regarded as an expensive
communication method. However, the MTC may be widely used only when
a price is low according to a characteristic thereof. Therefore, a
method of reducing a bandwidth for MTC to be smaller than a system
bandwidth has been examined for cost reduction.
[0004] Also, the MTC is recently getting attention as a means to
implement Internet of Things (IoT).
[0005] As one solution to provide IoT devices at low cost, an
operation scheme for IoT devices is under consideration, which
makes an IoT device operate with bandwidth more reduced than the
system bandwidth of a cell.
[0006] As described above, IoT communication operating with reduced
bandwidth is called Narrow Band (NB)-IoT communication.
[0007] To improve channel estimation and decoding performance of an
NB-IoT device, Narrowband Reference Signal (NRS) has been
proposed.
[0008] However, up to now, research has been conducted only into
transmission of the NRS from frequency division duplex (FDD)-based
subframes, and research into a method for transmitting the NRS on a
time division duplex-based subframe has not been conducted yet.
SUMMARY OF THE INVENTION
[0009] Accordingly, a disclosure of the present specification has
been made in an effort to solve the aforementioned problem.
[0010] To achieve the aforementioned purpose, a disclosure of the
present specification provides a method for receiving a narrowband
reference signal (NRS). The method may be performed by a narrowband
internet of things (NB-IoT) device and comprise: receiving the NRS
on at least one or more orthogonal frequency division multiplexing
(OFDM) symbols. The one or more OFDM symbols may be in a time
division duplex (TDD) subframe. If the TDD subframe corresponds to
a TDD special subframe, the one or more OFDM symbols for receiving
the NRS may be determined based on which a TDD special subframe
configuration index, among a plurality of TDD special subframe
configuration indexes, the TDD special subframe uses.
[0011] The TDD special subframe including the one or more OFDM
symbols for receiving the NRS may use at least one of TDD special
configuration indexes 1, 2, 3, 4, 6, 7, 8 and 9.
[0012] The one or more OFDM symbols for receiving the NRS may
include at least one of 6th and 7th symbols in the TDD special
subframe.
[0013] The NRS may not be received on at least one TDD special
subframe using TDD special configuration indexes 0 and 5.
[0014] The one or more OFDM symbols for receiving the NRS may
include at least one of 2nd and 3rd symbols in the TDD special
subframe.
[0015] The NRS on the TDD special subframe may be generated based
on a normal downlink subframe.
[0016] The method may comprise: receiving a second reference signal
(RS) in a TDD special subframe using a TDD special subframe
configuration index 10.
[0017] The second RS may include a cell-specific reference signal
(CRS) if a NB-IoT operation mode is an inband-samePCl mode
representing an inband same physical cell identifier (PCI).
[0018] If the NB-IoT operation mode is the inband-samePCl
representing the inband same PCI, a location of a resource element
(RE) to which the NRS is mapped may be different from a location of
a RE to which the CRS is mapped.
[0019] The second RS may include an NRS if a NB-IoT operation mode
is an inband-differentPCI mode representing an inband different
PCI.
[0020] If the NB-IoT operation mode is the inband-differentPCl
representing the inband different PCI, an RE to which the CRS is to
be mapped may be used as a blank RE.
[0021] The special subframe using the TDD special subframe
configuration index 10 may be designated as a valid subframe.
[0022] The special subframe using the TDD special subframe
configuration index 10 may include a downlink pilot time slot
(DwPTS) in which a downlink data is to be received.
[0023] The TDD special subframe in which the NRS is received may be
a valid subframe in which a downlink data is to be received.
[0024] To achieve the aforementioned purpose, a disclosure of the
present specification provides a narrowband internet of things
(NB-IoT) device for receiving a narrowband reference signal (NRS).
The NB-IoT device may comprise: a transceiver; and a processor
configured to receive, via the transceiver, the NRS on at least one
or more orthogonal frequency division multiplexing (OFDM) symbols.
The one or more OFDM symbols may be in a time division duplex (TDD)
subframe. If the TDD subframe corresponds to a TDD special
subframe, the one or more OFDM symbols for receiving the NRS may be
determined based on which a TDD special subframe configuration
index, among a plurality of TDD special subframe configuration
indexes, the TDD special subframe uses.
[0025] According to the disclosure of the present invention, the
problem of the conventional technology described above may be
solved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a wireless communication system.
[0027] FIG. 2 illustrates a structure of a radio frame according to
FDD in 3GPP LTE.
[0028] FIG. 3 illustrates a structure of a downlink radio frame
according to TDD in the 3GPP LTE.
[0029] FIG. 4a illustrates one example of Internet of Things (IoT)
communication.
[0030] FIG. 4b illustrates cell coverage extension or enhancement
for IoT devices.
[0031] FIG. 4c illustrates one example of transmitting a bundle of
downlink channels.
[0032] FIGS. 5a and 5b illustrate an example of a sub-band in which
IoT devices operate.
[0033] FIG. 6 illustrates an example where time resources that may
be used for NB-IoT are represented in units of M-frames.
[0034] FIG. 7 is another example illustrating time resources and
frequency resources that may be used for NB IoT.
[0035] FIG. 8 illustrates an example of subframe type in the
NR.
[0036] FIG. 9 illustrates a third symbol of a special subframe
described in Section I-1.
[0037] FIG. 10 illustrates the position of an RE to which an NRS is
mapped according to a method of I-1-3.
[0038] FIG. 11 illustrates a symbol to which an NRS is mapped
according to Section I-2.
[0039] FIG. 12 illustrates a symbol to which an NRS is mapped
according to Section I-3.
[0040] FIG. 13 illustrates a block diagram of a wireless device and
a base station in which a disclosure of the present specification
is implemented.
[0041] FIG. 14 is a detailed block diagram of a transceiver of a
wireless device of FIG. 13.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0042] Hereinafter, based on 3rd Generation Partnership Project
(3GPP) long term evolution (LTE) or 3GPP LTE-advanced (LTE-A), the
present invention will be applied. This is just an example, and the
present invention may be applied to various wireless communication
systems. Hereinafter, LTE includes LTE and/or LTE-A.
[0043] The technical terms used herein are used to merely describe
specific embodiments and should not be construed as limiting the
present invention. Further, the technical terms used herein should
be, unless defined otherwise, interpreted as having meanings
generally understood by those skilled in the art but not too
broadly or too narrowly. Further, the technical terms used herein,
which are determined not to exactly represent the spirit of the
invention, should be replaced by or understood by such technical
terms as being able to be exactly understood by those skilled in
the art. Further, the general terms used herein should be
interpreted in the context as defined in the dictionary, but not in
an excessively narrowed manner.
[0044] The expression of the singular number in the present
invention includes the meaning of the plural number unless the
meaning of the singular number is definitely different from that of
the plural number in the context. In the following description, the
term `include` or `have` may represent the existence of a feature,
a number, a step, an operation, a component, a part or the
combination thereof described in the present invention, and may not
exclude the existence or addition of another feature, another
number, another step, another operation, another component, another
part or the combination thereof.
[0045] The terms `first` and `second` are used for the purpose of
explanation about various components, and the components are not
limited to the terms `first` and `second`. The terms `first` and
`second` are only used to distinguish one component from another
component. For example, a first component may be named as a second
component without deviating from the scope of the present
invention.
[0046] It will be understood that when an element or layer is
referred to as being "connected to" or "coupled to" another element
or layer, it can be directly connected or coupled to the other
element or layer or intervening elements or layers may be present.
In contrast, when an element is referred to as being "directly
connected to" or "directly coupled to" another element or layer,
there are no intervening elements or layers present.
[0047] Hereinafter, exemplary embodiments of the present invention
will be described in greater detail with reference to the
accompanying drawings. In describing the present invention, for
ease of understanding, the same reference numerals are used to
denote the same components throughout the drawings, and repetitive
description on the same components will be omitted. Detailed
description on well-known arts which are determined to make the
gist of the invention unclear will be omitted. The accompanying
drawings are provided to merely make the spirit of the invention
readily understood, but not should be intended to be limiting of
the invention. It should be understood that the spirit of the
invention may be expanded to its modifications, replacements or
equivalents in addition to what is shown in the drawings.
[0048] As used herein, `base station` generally refers to a fixed
station that communicates with a wireless device and may be denoted
by other terms such as eNB (evolved-NodeB), BTS (base transceiver
system), or access point.
[0049] As used herein, `user equipment (UE)` may be stationary or
mobile, and may be denoted by other terms such as device, wireless
device, terminal, MS (mobile station), UT (user terminal), SS
(subscriber station), MT (mobile terminal) and etc.
[0050] Hereinafter, based on 3rd Generation Partnership Project
(3GPP) long term evolution (LTE) or 3GPP LTE-advanced (LTE-A), the
present invention will be applied. This is just an example, and the
present invention may be applied to various wireless communication
systems. Hereinafter, LTE includes LTE and/or LTE-A.
[0051] The technical terms used herein are used to merely describe
specific embodiments and should not be construed as limiting the
present invention. Further, the technical terms used herein should
be, unless defined otherwise, interpreted as having meanings
generally understood by those skilled in the art but not too
broadly or too narrowly. Further, the technical terms used herein,
which are determined not to exactly represent the spirit of the
invention, should be replaced by or understood by such technical
terms as being able to be exactly understood by those skilled in
the art. Further, the general terms used herein should be
interpreted in the context as defined in the dictionary, but not in
an excessively narrowed manner.
[0052] The expression of the singular number in the present
invention includes the meaning of the plural number unless the
meaning of the singular number is definitely different from that of
the plural number in the context. In the following description, the
term `include` or `have` may represent the existence of a feature,
a number, a step, an operation, a component, a part or the
combination thereof described in the present invention, and may not
exclude the existence or addition of another feature, another
number, another step, another operation, another component, another
part or the combination thereof.
[0053] The terms `first` and `second` are used for the purpose of
explanation about various components, and the components are not
limited to the terms `first` and `second`. The terms `first` and
`second` are only used to distinguish one component from another
component. For example, a first component may be named as a second
component without deviating from the scope of the present
invention.
[0054] It will be understood that when an element or layer is
referred to as being "connected to" or "coupled to" another element
or layer, it can be directly connected or coupled to the other
element or layer or intervening elements or layers may be present.
In contrast, when an element is referred to as being "directly
connected to" or "directly coupled to" another element or layer,
there are no intervening elements or layers present.
[0055] Hereinafter, exemplary embodiments of the present invention
will be described in greater detail with reference to the
accompanying drawings. In describing the present invention, for
ease of understanding, the same reference numerals are used to
denote the same components throughout the drawings, and repetitive
description on the same components will be omitted. Detailed
description on well-known arts which are determined to make the
gist of the invention unclear will be omitted. The accompanying
drawings are provided to merely make the spirit of the invention
readily understood, but not should be intended to be limiting of
the invention. It should be understood that the spirit of the
invention may be expanded to its modifications, replacements or
equivalents in addition to what is shown in the drawings.
[0056] As used herein, `base station` generally refers to a fixed
station that communicates with a wireless device and may be denoted
by other terms such as eNB (evolved-NodeB), BTS (base transceiver
system), or access point.
[0057] As used herein, `user equipment (UE)` may be stationary or
mobile, and may be denoted by other terms such as device, wireless
device, terminal, MS (mobile station), UT (user terminal), SS
(subscriber station), MT (mobile terminal) and etc.
[0058] FIG. 1 illustrates a wireless communication system.
[0059] As seen with reference to FIG. 1, the wireless communication
system includes at least one base station (BS) 20. Each base
station 20 provides a communication service to specific
geographical areas (generally, referred to as cells) 20a, 20b, and
20c. The cell can be further divided into a plurality of areas
(sectors).
[0060] The UE generally belongs to one cell and the cell to which
the UE belong is referred to as a serving cell. Abase station that
provides the communication service to the serving cell is referred
to as a serving BS. Since the wireless communication system is a
cellular system, another cell that neighbors to the serving cell is
present. Another cell which neighbors to the serving cell is
referred to a neighbor cell. A base station that provides the
communication service to the neighbor cell is referred to as a
neighbor BS. The serving cell and the neighbor cell are relatively
decided based on the UE.
[0061] Hereinafter, a downlink means communication from the base
station 20 to the UE1 10 and an uplink means communication from the
UE 10 to the base station 20. In the downlink, a transmitter may be
a part of the base station 20 and a receiver may be a part of the
UE 10. In the uplink, the transmitter may be a part of the UE 10
and the receiver may be a part of the base station 20.
[0062] Meanwhile, the wireless communication system may be
generally divided into a frequency division duplex (FDD) type and a
time division duplex (TDD) type. According to the FDD type, uplink
transmission and downlink transmission are achieved while occupying
different frequency bands. According to the TDD type, the uplink
transmission and the downlink transmission are achieved at
different time while occupying the same frequency band. A channel
response of the TDD type is substantially reciprocal. This means
that a downlink channel response and an uplink channel response are
approximately the same as each other in a given frequency area.
Accordingly, in the TDD based wireless communication system, the
downlink channel response may be acquired from the uplink channel
response. In the TDD type, since an entire frequency band is
time-divided in the uplink transmission and the downlink
transmission, the downlink transmission by the base station and the
uplink transmission by the terminal may not be performed
simultaneously. In the TDD system in which the uplink transmission
and the downlink transmission are divided by the unit of a
subframe, the uplink transmission and the downlink transmission are
performed in different subframes.
[0063] Hereinafter, the LTE system will be described in detail.
[0064] FIG. 2 shows a downlink radio frame structure according to
FDD of 3rd generation partnership project (3GPP) long term
evolution (LTE).
[0065] The radio frame of FIG. 2 may be found in the section 5 of
3GPP TS 36.211 V10.4.0 (2011-12) "Evolved Universal Terrestrial
Radio Access (E-UTRA); Physical Channels and Modulation (Release
10)".
[0066] The radio frame includes 10 sub-frames indexed 0 to 9. One
sub-frame includes two consecutive slots. Accordingly, the radio
frame includes 20 slots. The time taken for one sub-frame to be
transmitted is denoted TTI (transmission time interval). For
example, the length of one sub-frame may be 1 ms, and the length of
one slot may be 0.5 ms.
[0067] The structure of the radio frame is for exemplary purposes
only, and thus the number of sub-frames included in the radio frame
or the number of slots included in the sub-frame may change
variously.
[0068] One slot includes NRB resource blocks (RBs) in the frequency
domain. For example, in the LTE system, the number of resource
blocks (RBs), i.e., NRB, may be one from 6 to 110.
[0069] The resource block is a unit of resource allocation and
includes a plurality of sub-carriers in the frequency domain. For
example, if one slot includes seven OFDM symbols in the time domain
and the resource block includes 12 sub-carriers in the frequency
domain, one resource block may include 7.times.12 resource elements
(REs).
[0070] The physical channels in 3GPP LTE may be classified into
data channels such as PDSCH (physical downlink shared channel) and
PUSCH (physical uplink shared channel) and control channels such as
PDCCH (physical downlink control channel), PCFICH (physical control
format indicator channel), PHICH (physical hybrid-ARQ indicator
channel) and PUCCH (physical uplink control channel).
[0071] The uplink channels include a PUSCH, a PUCCH, an SRS
(Sounding Reference Signal), and a PRACH (physical random access
channel).
[0072] FIG. 3 illustrates the architecture of a downlink radio
frame according to TDD in 3GPP LTE.
[0073] For this, 3GPP TS 36.211 V10.4.0 (2011-23) "Evolved
Universal Terrestrial Radio Access (E-UTRA); Physical Channels and
Modulation (Release 8)", Ch. 4 may be referenced, and this is for
TDD (time division duplex).
[0074] Sub-frames having index #1 and index #6 are denoted special
sub-frames, and include a DwPTS(Downlink Pilot Time Slot: DwPTS), a
GP(Guard Period) and an UpPTS(Uplink Pilot Time Slot). The DwPTS is
used for initial cell search, synchronization, or channel
estimation in a terminal. The UpPTS is used for channel estimation
in the base station and for establishing uplink transmission sync
of the terminal. The GP is a period for removing interference that
arises on uplink due to a multi-path delay of a downlink signal
between uplink and downlink.
[0075] In TDD, a DL (downlink) sub-frame and a UL (Uplink) co-exist
in one radio frame. Table 1 shows an example of configuration of a
radio frame.
TABLE-US-00001 TABLE 1 UL-DL Switch-point Subframe index
configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S
U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms
D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D
D D D D 6 5 ms D S U U U D S U U D
[0076] `D` denotes a DL sub-frame, `U` a UL sub-frame, and `S` a
special sub-frame. When receiving a UL-DL configuration from the
base station, the terminal may be aware of whether a sub-frame is a
DL sub-frame or a UL sub-frame according to the configuration of
the radio frame.
TABLE-US-00002 TABLE 2 Normal CP in downlink Extended CP in
downlink UpPTS UpPTS Special Normal Extended Normal Extended
subframe CP in CP in CP in CP in configuration DwPTS uplink uplink
DwPTS uplink uplink 0 6592*Ts 2192*Ts 2560*Ts 7680*Ts 2192*Ts
2560*Ts 1 19760*Ts 20480*Ts 2 21952*Ts 23040*Ts 3 24144*Ts 25600*Ts
4 26336*Ts 7680*Ts 4384*Ts 5120*ts 5 6592*Ts 4384*Ts 5120*ts
20480*Ts 6 19760*Ts 23040*Ts 7 21952*Ts -- 8 24144*Ts --
[0077] <Carrier Aggregation>
[0078] A carrier aggregation system is now described.
[0079] A carrier aggregation system aggregates a plurality of
component carriers (CCs). A meaning of an existing cell is changed
according to the above carrier aggregation. According to the
carrier aggregation, a cell may signify a combination of a downlink
component carrier and an uplink component carrier or an independent
downlink component carrier.
[0080] Further, the cell in the carrier aggregation may be
classified into a primary cell, a secondary cell, and a serving
cell. The primary cell signifies a cell operated in a primary
frequency. The primary cell signifies a cell which UE performs an
initial connection establishment procedure or a connection
reestablishment procedure or a cell indicated as a primary cell in
a handover procedure. The secondary cell signifies a cell operating
in a secondary frequency. Once the RRC connection is established,
the secondary cell is used to provided an additonal radio
resouce.
[0081] As described above, the carrier aggregation system may
support a plurality of component carriers (CCs), that is, a
plurality of serving cells unlike a single carrier system.
[0082] The carrier aggregation system may support a cross-carrier
scheduling. The cross-carrier scheduling is a scheduling method
capable of performing resource allocation of a PDSCH transmitted
through other component carrier through a PDCCH transmitted through
a specific component carrier and/or resource allocation of a PUSCH
transmitted through other component carrier different from a
component carrier basically linked with the specific component
carrier.
[0083] <Internet of Things (IoT) Communication>
[0084] In what follows, IoT will be described.
[0085] FIG. 4a illustrates one example of Internet of Things (IoT)
communication.
[0086] IoT refers to exchange of information through a base station
200 among IoT devices 100, which does not involve human interaction
or exchange of information through the base station 200 between an
IoT device 100 and a server 700. In this way, IoT is also called
Cellular Internet of Things (CIoT) in that IoT communication
employs a cellular base station.
[0087] IoT communication as described above is one type of Machine
Type Communication (MTC). Therefore, an IoT device may also be
called an MTC device.
[0088] IoT services may be distinguished from communication-based
conventional services which require human intervention, including a
wide range of services such as tracking, metering, payment,
medical-care, and remote control. For example, IoT services may
include meter reading, level measurement, use of surveillance
cameras, reporting an inventory of a vending machine, and so
on.
[0089] Since the amount of transmission data handled by IoT
communication is small, and transmission and reception of uplink or
downlink data occurs infrequently, it is preferable to lower the
unit price of an IoT device 100 and to reduce battery consumption
according to a low data transfer rate. Also, since an IoT device
100 has low mobility, channel conditions rarely change.
[0090] FIG. 4b illustrates cell coverage extension or enhancement
for IoT devices.
[0091] Recently, cell coverage extension or enhancement of a base
station to accommodate IoT devices 100 is being considered, and
various techniques for extending or enhancing cell coverage are
under discussion.
[0092] It should be noted, however, that when cell coverage is
extended or enhanced, and a base station transmits a downlink
channel to an IoT device located in the coverage extension (CE)
area or coverage enhancement (CE) area, the IoT device encounters a
difficulty in receiving the downlink channel.
[0093] To solve the problem above, a downlink channel or an uplink
channel may be transmitted repeatedly on several subframes. In this
way, transmission of an uplink/downlink channel repeatedly on
several subframes is referred to as bundle transmission.
[0094] FIG. 4c illustrates one example of transmitting a bundle of
downlink channels.
[0095] As may be known from FIG. 4c, a base station transmits a
downlink channel (for example, PDCCH and/or PDSCH) repeatedly to an
IoT device 100 located in a coverage extension area on several
subframes (for example, N subframes).
[0096] Then the IoT device or base station receives a bundle of
downlink/uplink channels on several subframes and improves a
decoding success rate by decoding the whole or part of the
bundle.
[0097] FIGS. 5a and 5b illustrate an example of a sub-band in which
IoT devices operate.
[0098] As one solution for providing IoT devices at low cost, as
shown in FIG. 5a, the IoT devices may use a sub-band of, for
example, approximately 1.4 MHz independently of the system
bandwidth of a cell.
[0099] At this time, as shown in FIG. 5a, the sub-band area in
which the IoT devices operate may be located in the central area
(for example, central six PRBs) of the system bandwidth of the
cell.
[0100] Similarly, as shown in FIG. 5b, a plurality of sub-bands for
IoT devices may be defined within one subframe for multiplexing of
the IoT devices so that the IoT devices may use separate sub-bands.
At this time, a majority of the IoT devices may use a different
sub-band rather than the central area (for example, central six
PRBs) of the system bandwidth of the cell.
[0101] As described above, the IoT communication operating with
reduced bandwidth may be referred to as Narrow Band (NB) IoT
communication or NB CIoT communication.
[0102] FIG. 6 illustrates an example where time resources that may
be used for NB-IoT are represented in units of M-frames.
[0103] Referring to FIG. 6, a frame which may be used for NB-IoT is
called an M-frame, the length of which may be 60 ms, for example.
Also, a subframe which may be used for NB IoT is called an
M-subframe, the length of which may be 6 ms, for example.
Therefore, an M-frame may comprise 10 M-subframes.
[0104] Each M-subframe may comprise two slots, and each slot may be
3 ms, for example.
[0105] However, different from what is shown in FIG. 6, a slot
which may be used for NB IoT may have a length of 2 ms, a subframe
may accordingly have a length of 4 ms, and a frame may have a
length of 40 ms. Regarding this possibility, more details will be
given with reference to FIG. 7.
[0106] FIG. 7 is another example illustrating time resources and
frequency resources that may be used for NB IoT.
[0107] Referring to FIG. 7, a physical channel or physical signal
transmitted on a slot from an uplink of NB-IoT includes
N.sub.symb.sup.UL SC-FDMA symbols in the time domain and
N.sub.SC.sup.UL subcarriers in the frequency domain. The uplink
physical channel may be divided into a Narrowband Physical Uplink
Shared Channel (NPUSCH) and a Narrowband Physical Random Access
Channel (NPRACH). And a physical signal in the NB-IoT may become a
Narrowband DeModulation Reference Signal (NDMRS).
[0108] The uplink bandwidths of N.sub.SC.sup.UL subcarriers during
T.sub.slot slots in the NB-IoT are as follows.
TABLE-US-00003 TABLE 3 Subcarrier spacing N.sup.UL.sub.SC
T.sub.slot .DELTA.f = 3.75 kHz 48 61440*T.sub.s .DELTA.f = 15 kHz
12 15360*T.sub.s
[0109] In the NB-IoT, each resource element (RE) of a resource grid
may be defined by an index pair (k, l) within a slot, where k=0, .
. . , N.sub.SC.sup.UL-1, and l=0, . . . , N.sub.symb.sup.UL-1,
specifying an index in the time and frequency domain,
respectively.
[0110] In the NB-IoT, a downlink physical channel includes a
Narrowband Physical Downlink Shared Channel (NPDSCH), Narrowband
Physical Broadcast Channel (NPBCH), and Narrowband Physical
Downlink Control Channel (NPDCCH). And a downlink physical signal
includes a Narrowband reference signal (NRS), Narrowband
synchronization signal (NSS), and Narrowband positioning reference
signal (NPRS). The NSS includes a Narrowband primary
synchronization signal (NPSS) and a Narrowband secondary
synchronization signal (NSSS).
[0111] Meanwhile, NB-IoT is a communication scheme for wireless
devices using bandwidth reduced to satisfy low-complexity/low-cost
constraints (namely, narrowband). The NB-IoT is aimed to allow as
many wireless devices as possible to be connected by using the
reduced bandwidth. Moreover, the NB-IoT communication is aimed to
support cell coverage larger than the cell coverage provided in the
legacy LTE communication.
[0112] Meanwhile, as may be known from Table 1, when subcarrier
spacing is 15 kHz, a carrier having the reduced bandwidth includes
only one PRB. In other words, NB-IoT communication may be performed
by using only one PRB. Here, a wireless device assumes that
NPSS/NSSS/NPBCH/SIB-NB is transmitted from a base station, where a
PRB connected to receive the NPSS/NSSS/NPBCH/SIB-NB may be called
an anchor PRB (or anchor carrier). Meanwhile, in addition to the
anchor PRB (or anchor carrier), the wireless device may receive
additional PRBs from the base station. Here, among the additional
PRBs, those PRBs not expected to receive the NPSS/NSSS/NPBCH/SIB-NB
from the base station may be called a non-anchor PRB (or non-anchor
carrier).
[0113] The NRS is generated by a sequence r.sub.l,ns(m), and the
sequence r.sub.l,ns(m) may be mapped to a complex-valued modulation
symbol, namely a.sub.k,l.sup.(p).
[0114] The complex-valued modulation symbol, namely
a.sub.k,l.sup.(p) is used as a reference signal for the antenna
port p within a slot n.sub.s.
a.sub.k,l.sup.(p)=r.sub.l,n.sub.s(m') [Eq. 1]
[0115] k=6m+(v+v.sub.shift) mod 6
[0116] l=N.sub.symb.sup.DL-2, N.sub.symb.sup.DL-1
[0117] m=0, 1
[0118] m'=m+N.sub.RB.sup.max,DL-1
[0119] The variable v and v.sub.shift represent the positions in
the frequency domain with respect to other reference signals. v is
determined by the following equation.
v = { 0 if p = 2000 and l = N symb DL - 2 3 if p = 2000 and l = N
symb DL - 1 3 if p = 2001 and l = N symb DL - 2 0 if p = 2001 and l
= N symb DL - 1 [ Eq . 2 ] ##EQU00001##
[0120] The cell-specific frequency shift is given as follows.
v.sub.shift=N.sub.ID.sup.Ncell mod 6. [Eq. 3]
Next-Generation Mobile Communication Network
[0121] Due to the success of the long term evolution
(LTE)/LTE-Advanced (LTE-A) for the fourth-generation mobile
communication, a public interest in the next-generation (so-called
5G) mobile communication is growing, and researches into the
next-generation mobile communication are conducted one after
another.
[0122] The 5-th generation mobile communication, as defined by the
International Telecommunication Union (ITU), refers to the
technology aimed to provide a data transfer speed of up to 20 Gbps
and an effective transfer speed faster than at least 100 Mbps
everywhere. The official name of the 5-th generation mobile
communication is `IMT-2020`, which is due to be commercialized by
2020 worldwide.
[0123] The ITU proposed three use case scenarios: enhanced Mobile
BroadBand (eMBB), massive Machine Type Communication (mMTC), Ultra
Reliable and Low Latency Communication (URLLC).
[0124] URLLC is related to a use scenario which requires high
reliability and low latency. For example, such services as
automated driving, factory automation, and augmented reality
require high reliability and low latency (for example, latency less
than 1 ms). The latency of the current 4G (LTE) technology is
statistically 21-43 ms (best 10%) and 33-75 ms (median). This
specification is not sufficient to support services requiring
latency less than 1 ms. The eMBB described next is related to a use
scenario requiring a mobile ultra-wideband.
[0125] In other words, the 5-th generation mobile communication
system targets to provide a capacity higher than that of the
current 4G LTE, improve density of mobile broadband users, and
support high reliability and Machine Type Communication (MTC). 5G
R&Ds also target lower latency and lower battery consumption
than provided by the 4G mobile communication system to implement
the Internet of things more efficiently. To realize the 5G mobile
communication as described above, a new radio access technology
(New RAT or NR) may be proposed.
[0126] In the NR, it may be taken into consideration that reception
from a base station may use downlink subframes, and transmission to
the base station may use uplink subframes. This scheme may be
applied to paired spectra and unpaired spectra. One pair of spectra
indicates that two carrier spectra are involved for downlink and
uplink operations. For example, in one pair of spectra, one carrier
may include a downlink and uplink bands forming a pair with each
other.
[0127] FIG. 8 illustrates an example of subframe type in the
NR.
[0128] The transmission time interval (TTI) shown in FIG. 8 may be
called a subframe or a slot for the NR (or new RAT). The subframe
(or slot) of FIG. 8 may be used in the TDD system of NR (or new
RAT) to minimize data transfer latency. As shown in FIG. 8, a
subframe (or slot) comprises 14 symbols in the same way as the
current subframe. The leading symbol of a subframe (or slot) may be
used for DL control channel, and the trailing symbol of the
subframe (or slot) may be used for UL control channel. The
remaining symbols may be used for DL data transmission or UL data
transmission. According to the aforementioned subframe (or slot)
structure, downlink transmission and uplink transmission may be
carried out sequentially in one subframe (or slot). Therefore,
downlink data may be received within the subframe (or slot), or an
uplink acknowledgement response (ACK/NACK) may also be transmitted
within the subframe (or slot). The structure of the subframe (or
slot) as described above may be referred to as a self-contained
subframe (or slot). When this subframe (or slot) structure is used,
time required to retransmit data which has caused a reception error
is reduced, leading to minimization of final data transmission
waiting time. In the self-contained subframe (or slot) structure,
however, a time gap may be needed for a transitioning process from
a transmission mode to a reception more or vice versa. To this end,
part of OFDM symbols employed for transitioning from DL to UL
transmission in the subframe structure may be designated as a guard
period (GP).
Support of Various Numerologies
[0129] In the next-generation system, according to the advances in
the wireless communication technology, a plurality of numerologies
may be provided for a UE.
[0130] The numerology may be defined by the length of cyclic prefix
(CP) and subcarrier spacing. A single cell may provide a plurality
of numerologies to a UE. If the index of numerology is represented
by .mu., each subcarrier spacing and the corresponding CP length
may be given as follows.
TABLE-US-00004 TABLE 4 .mu. .DELTA.f = 2.sup..mu. 15 [kHz] CP 0 15
Normal 1 30 Normal 2 60 Normal, Extended 3 120 Normal 4 240
Normal
[0131] In the case of normal CP, if the numerology index is
represented by .mu., the number of OFDM symbols per slot
(N.sub.symb.sup.slot), the number of slots per frame
(N.sub.slot.sup.frame,.mu.), and the number of slots per subframe
(N.sub.slot.sup.subframe,.mu.) are given as follows.
TABLE-US-00005 TABLE 5 .mu. N.sub.symb.sup.slot
N.sub.slot.sup.frame, .mu. N.sub.slot.sup.subframe, .mu. 0 14 10 1
1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16 5 14 320 32
[0132] In the case of extended CP, if the numerology index is
represented by .mu., the number of OFDM symbols per slot
(N.sub.symb.sup.slot), the number of slots per frame
(N.sub.slot.sup.frame,.mu.), and the number of slots per subframe
(N.sub.slot.sup.subframe,.mu.) are given as follows.
TABLE-US-00006 TABLE 6 .mu. N.sub.symb.sup.slot
N.sup.slot.sup.frame, .mu. N.sub.slot.sup.subframe, .mu. 2 12 40
4
[0133] Meanwhile, in the next-generation mobile communication, each
symbol within a slot may be used as a downlink or an uplink as
shown in the table below. In the table below, the uplink is denoted
by U while the downlink is denoted by D. In the table below, X
represents a symbol which may be used flexibly as an uplink or a
downlink.
TABLE-US-00007 TABLE 7 Symbol number in a slot Format 0 1 2 3 4 5 6
7 8 9 10 11 12 13 0 D D D D D D D D D D D D D D 1 U U U U U U U U U
U U U U U 2 X X X X X X X X X X X X X X 3 D D D D D D D D D D D D D
X 4 D D D D D D D D D D D D X X 5 D D D D D D D D D D D X X X 6 D D
D D D D D D D D X X X X 7 D D D D D D D D D X X X X X 8 X X X X X X
X X X X X X X U 9 X X X X X X X X X X X X U U 10 X U U U U U U U U
U U U U U 11 X X U U U U U U U U U U U U 12 X X X U U U U U U U U U
U U 13 X X X X U U U U U U U U U U 14 X X X X X U U U U U U U U U
15 X X X X X X U U U U U U U U 16 D X X X X X X X X X X X X X 17 D
D X X X X X X X X X X X X 18 D D D X X X X X X X X X X X 19 D X X X
X X X X X X X X X U 20 D D X X X X X X X X X X X U 21 D D D X X X X
X X X X X X U 22 D X X X X X X X X X X X U U 23 D D X X X X X X X X
X X U U 24 D D D X X X X X X X X X U U 25 D X X X X X X X X X X U U
U 26 D D X X X X X X X X X U U U 27 D D D X X X X X X X X U U U 28
D D D D D D D D D D D D X U 29 D D D D D D D D D D D X X U 30 D D D
D D D D D D D X X X U 31 D D D D D D D D D D D X U U 32 D D D D D D
D D D D X X U U 33 D D D D D D D D D X X X U U 34 D X U U U U U U U
U U U U U 35 D D X U U U U U U U U U U U 36 D D D X U U U U U U U U
U U 37 D X X U U U U U U U U U U U 38 D D X X U U U U U U U U U U
39 D D D X X U U U U U U U U U 40 D X X X U U U U U U U U U U 41 D
D X X X U U U U U U U U U 42 D D D X X X U U U U U U U U 43 D D D D
D D D D D X X X X U 44 D D D D D D X X X X X X U U 45 D D D D D D X
X U U U U U U 46 D D D D D D X D D D D D D X 47 D D D D D X X D D D
D D X X 48 D D X X X X X D D X X X X X 49 D X X X X X X D X X X X X
X 50 X U U U U U U X U U U U U U 51 X X U U U U U X X U U U U U 52
X X X U U U U X X X U U U U 53 X X X X U U U X X X X U U U 54 D D D
D D X U D D D D D X U 55 D D X U U U U D D X U U U U 56 D X U U U U
U D X U U U U U 57 D D D D X X U D D D D X X U 58 D D X X U U U D D
X X U U U 59 D X X U U U U D X X U U U U 60 D X X X X X U D X X X X
X U 61 D D X X X X U D D X X X X U
Disclosure of the Present Specification
[0134] The present specification proposes methods for transmitting
and receiving a reference signal (RS) on a special subframe to
support Narrow band Internet of Things (NB-IoT) employing the
Time-Division Duplexing (TDD) scheme.
[0135] NB-IoT may operate in one of the following three operation
modes. The three operation modes may include a guard-band operation
mode, stand-alone operation mode, and in-band operation mode. After
setting the operation mode, the base station transmits an upper
layer signal through, for example, a Master Information Block (MIB)
or a System Information Block (SIB) to a UE (for example, an NB-IoT
device).
[0136] The in-band operation mode refers to a mode where an NB-IoT
cell operates in part of a band in which a first LTE cell operates.
The in-band operation mode is further divided into an in-band same
PCI mode (inband-samePCl) where the NB-IoT cell and the LTE cell
share the same physical cell ID (hereinafter, it is also called a
PCI) and an in-band different PCI mode (inband-DifferentPCl) where
the NB-IoT cell and the LTE cell use different PCIs.
[0137] In the in-band same PCI mode, the number of NRSs is the same
as the number of CRSs.
[0138] The guard-band operation mode refers to a mode where part of
the LTE band is designated as a guard band, and the NB-IoT cell
uses the guard band not used by the LTE cell. For example, the
NB-IoT cell may operate one a guard band existing between a first
band where a first LTE cell operates and a second band where a
second LTE cell operates.
[0139] The stand-alone operation mode refers to a mode where the
NB-IoT cell operates on a band where a non-LTE cell operates. For
example, the NB-IoT cell may operate in part of a band where a GSM
cell operates.
[0140] In what follows, for the convenience of descriptions,
methods for transmitting an RS on a special subframe in the NB-IoT
will be mostly described; however, it should be noted that the
proposed methods may be applied to general communication systems in
the same manner.
[0141] I. First Disclosure: Transmission of a Narrowband Reference
Signal (NRS) on a Special Subframe
[0142] First, except for the case where the operation mode of
NB-IoT is the in-band same PCI mode (inband-samePCl), an NB-IoT
device (or UE) is unable to use a CRS. Also, the more the number of
available downlink reference signals, the better the accuracy of
measurement performed by an NB-IoT device (or UE) and the
performance of channel estimation become. However, since NB-IoT has
been designed by considering only the FDD scheme of the 3GPP
release-14 and does not take into account the structure of a TDD
special subframe, NRS transmission based on the TDD scheme may not
be easily performed if the existing definition is reused. More
specifically, in the case of NB-IoT, a CRS is not used, but an NRS
is utilized for improving measurement accuracy and performing
channel estimation. The NRS has been designed by using the FDD
scheme since the release-14. However, a method for transmitting an
NRS on a TDD special subframe has not been studied yet. To this
regard, the first disclosure of the present specification proposes
a method for transmitting an RS which may be used by an NB-IoT
device (or UE) on a special subframe. More specifically, the
corresponding RS may become an NRS in the NB-IoT communication. The
methods proposed below may be used separately, or in the form of a
combination of one or more of the methods.
[0143] I-1. Method for Transmitting NRS on Third Symbol of Special
Subframe
[0144] The present section proposes a method for transmitting an
NRS by using a third symbol of a special subframe. The third symbol
refers to a symbol appearing thirdly on the special subframe.
[0145] FIG. 9 illustrates a third symbol of a special subframe
described in Section I-1.
[0146] The example of FIG. 9 assumes a situation of TDD UL-DL
configuration#0 and special subframe configuration#0. However, the
definition of the third symbol may be applied to other TDD UL-DL
configuration#0 in the same manner.
[0147] A specific example to which the proposal above is applied
may be described as follows.
[0148] I-1-1. Application Method May Be Determined According to
Special Subframe Configuration Index
[0149] I-1-1-1. When a specific special subframe configuration is
used, an NRS may be transmitted to all of the special subframes
from the entire carriers available for NB-IoT.
[0150] The aforementioned specific special subframe configuration
may correspond to #0 and #5 of Table 2.
[0151] The aforementioned specific special subframe configuration
may be defined by a special subframe configuration where the length
of DwPTS is less than X symbols.
[0152] At this time, it is possible that X=3.
[0153] The available carrier described above may include an anchor
carrier from which an NB-IoT device (or UE) acquires
synchronization and also include a non-anchor carrier configured
through higher layer signaling.
[0154] If information related to special subframe configuration may
be distinguished in a step for acquiring an NPSS and an NSSS, and
the distinguished information may be used for determining whether
an NRS is always transmitted from a third symbol of the special
subframe,
[0155] The NB-IoT device (namely, UE) may use the NRS of the third
symbol of the special subframe during a cell selection process.
[0156] The NB-IoT device (namely, UE) may use the NRS of the third
symbol of the special subframe for decoding of an NPBCH.
[0157] I-1-1-2. When specific special subframe configuration is
used, and the special subframe among carriers available for NB-IoT
is designated as a valid subframe, an NRS may be transmitted.
[0158] The aforementioned specific special subframe configuration
may correspond to #1, #2, #3, #4, #6, #7, #8, and #9 of Table
2.
[0159] Option a. The aforementioned valid subframe is defined as a
subframe to which an NB-IoT device (or UE) expects an NPDCCH or
NPDSCH to be transmitted. This information may be delivered to an
NB-IoT device (or UE) through higher layer signaling such as one
using an SIB or an RRC signal.
[0160] Option b. The aforementioned valid subframe may be an
independent meaning defined only for a special subframe. In this
case, the valid subframe with respect to the special frame may be
defined as a subframe to which an NRS is transmitted irrespective
of transmission of an NPDCCH or an NPDSCH. This information may be
delivered to an NB-IoT device (or UE) through higher layer
signaling such as one using an SIB or an RRC signal.
[0161] In the case of a special subframe except for the valid
subframe delivered through higher layer signaling, information
about the special subframe to be transmitted dynamically by an NRS
through DCI may be delivered to an NB-IoT device (or UE).
[0162] When the information is delivered dynamically through DCI,
the delivery may be applied in conjunction with the option a or
option b.
[0163] The aforementioned available carrier may include an anchor
carrier from which an NB-IoT device (or UE) acquires
synchronization also include a non-anchor carrier configured
through higher layer signaling.
[0164] I-1-1-3. When specific special subframe configuration is
used, transmission of an NRS may be determined according to whether
to transmit NPDCCH or NPDSCH.
[0165] The aforementioned specific special subframe configuration
may correspond to #9 of Table 2.
[0166] For example, when an NPDCCH or an NPDSCH is used, an NRS may
be made not to be transmitted to the corresponding special
subframe.
[0167] Whether an NPDCCH or an NPDSCH is transmitted from the
special subframe may be delivered through higher layer signaling
such as one using an SIB or an RRC signal or through DCI.
[0168] At this time, the SIB, RRC signal, or DCI may include an
information field of 1-bit length which indicates whether to use a
special subframe for data transmission or NRS transmission or may
include an information field in the form of a bitmap.
[0169] As in the proposed method, the reason why the application id
determined according to the special subframe configuration index is
that availability of the third symbol of the special subframe is
changed according to the special subframe configuration. For
example, in the case of special subframe configuration #0 and #5,
the third symbol of the special subframe is not used in the legacy
LTE system except for central six RBs, the special subframe is
always available for an NB-IoT carrier. Meanwhile, in the case of
special subframe configuration #1, #2, #3, #4, #6, #7, #8, and #9,
the special frame may be used as an LTE PDSCH; therefore,
information about whether the corresponding special subframe is
available in the NB-IoT communication has to be provided.
[0170] I-1-2. Application Method May Be Determined According to
Operation Mode of NB-IoT
[0171] I-1-2-1. When the operation mode is in-band, an NRS may be
transmitted only when a specific condition is satisfied.
[0172] At this time, the specific condition is a condition for a
special subframe configuration index.
[0173] The specific condition may be a condition about whether the
special subframe is a valid subframe.
[0174] The specific condition may be related to whether the carrier
is an anchor carrier and/or a carrier to which an SIB for NB-IoT
(for example, SIB1-NB) is transmitted.
[0175] At this time, the NB-IoT device (or UE) may assume that an
NRS is always transmitted in a DwPTS of the corresponding
carrier.
[0176] I-1-2-2. When operation mode is guardband or standalone, NRS
may be always transmitted.
[0177] After checking the operation mode, an NB-IoT device (or UE)
notices that an NRS always exists in the third symbol of a DwPTS
and uses the fact for decoding.
[0178] To this end, all of the special subframe configurations
include NRS transmission in the third symbol.
[0179] For example, it may be configured so that the 3rd, 6th, 7th,
and 10th OFDM symbols are used for NRS transmission in the special
subframe, and an NRS is transmitted at the corresponding positions
when the DwPTS length includes the OFDM symbol index.
[0180] The reason why the application is determined according to
the operation mode as in the proposed method is that when the
operation mode is guardband or standalone, the DwPTS area may be
used only for the purpose of NB-IoT communication. On the other
hand, when the operation mode is inband, except for a specific
situation, it is not possible to determine whether a special
subframe area is used only for the purpose of NB-IoT communication,
use of inband mode may be restricted. If the proposed method is
used, a UE is able to utilize more NRSs in a situation where only a
limited amount of NRSs is allowed to be used, such as the SIB1-NB,
and therefore, performance improvement may be obtained.
[0181] I-1-3. NRS Used in the Third Symbol of Special Subframe May
Use the Following Options.
[0182] Option a. A method for generating an NRS used by other
downlink subframe and a method for determining frequency domain
resources may be used.
[0183] A method for generating a sequence of the NRS may reuse an
existing method for generating an NRS sequence according to Eqs. 1
to 3.
[0184] The position of a frequency domain resource of the NRS may
be determined by the k value which determines a mapping position in
the frequency domain of the method defined by Eq. 1.
[0185] At this time, the position of the time domain resource to be
applied may be determined so that l=2 at the first slot. This
position corresponds to the third symbol of the special subframe.
An embodiment thereof is illustrated in FIG. 10.
[0186] Option b. The option b may determine to use a method for
generating an NRS newly defined for the third symbol of a special
subframe and a frequency domain mapping rule. At this time, the
newly defined NRS may be designed to use all of 12 resource
elements (REs) used by the third symbol.
[0187] As one example, a Zadoff-Chu sequence may be used. At this
time, the root index of the Zadoff-Chu sequence may be determined
by NNcellID which distinguishes an NB-IoT cell ID.
[0188] For example, a Gold sequence may be used. At this time, the
C.sub.init value of the Gold sequence may be determined by NNcellID
which distinguishes an NB-IoT cell ID.
[0189] This method may be applied only to the case where the
corresponding NRS symbol is not used for the purpose of data
transmission. To this end, a base station may deliver information
about whether a newly defined NRS is transmitted to the
corresponding position to an NB-IoT device (or UE) through higher
layer signal or DCI.
[0190] The option a described above provides an advantage that an
existing method may be reused. The option b may be intended to
lower PAPR by using all of the REs when data are not transmitted to
the corresponding symbol.
[0191] I-1-4. Energy per resource element (EPRE) of NRS transmitted
from the third symbol of special subframe may be configured
separately from the EPRE of NRS transmitted from a different
subframe.
[0192] I-1-4-1. The EPRE of an NRS transmitted from the third
symbol of a special subframe may be determined by an offset (or in
the form of a multiple) from the EPRE of an NRS transmitted from a
different subframe.
[0193] Option a. At this time, the EPRE of an NRS transmitted from
the third symbol of a special subframe may be delivered to an
NB-IoT device (or UE) through higher layer signaling using an SIB
or an RRC signal.
[0194] At this time, the EPRE of an NRS transmitted from the third
symbol of the special subframe may be determined by a fixed offset
from the EPRE of an NRS transmitted from a different subframe.
[0195] The option above may be applied only for the case where data
are not mapped to the third symbol of the special subframe.
[0196] For example, when the number of REs to which an NRS from the
third symbol of the special subframe is mapped is N, and the EPRE
of an NRS from a different DL subframe is defined by ENRS, the EPRE
of the NRS used at the third symbol of the special subframe may be
defined by the mathematical equation below.
E NRS_special = E NRS .times. 12 N [ Eq . 4 ] ##EQU00002##
[0197] I-2. Method for Transmitting NRS by Using First to Third
Symbols of Special Subframe
[0198] The method proposed in the present section includes a method
for transmitting an NRS using a first to third symbols of a special
subframe. At this time, the first to the third symbols indicate the
symbols appearing firstly, secondly, and thirdly on the special
subframe, respectively.
[0199] FIG. 11 illustrates a symbol to which an NRS is mapped
according to Section I-2.
[0200] The embodiment of FIG. 11 assumes a situation based on UL-DL
configuration#0 and special subframe configuration#0, but it should
be clearly understood that the definition of the first, second, and
third symbols may be applied in the same way for other TDD
configurations.
[0201] The proposed method is a special case of the method
described in Section I-1, and the operations other than those given
in the descriptions below may be performed in the same manner as in
the method described in Section I-1. For example, a method for
distinguishing a special subframe configuration index or a method
for configuring the EPRE for which the corresponding method is
applied may be applied in the same manner as in the method
described in Section I-1.
[0202] A specific method to which the proposed specification is
applied may be described as follows.
[0203] The proposed specification may be applied only to the case
where the operation mode of the corresponding cell is the guard
band or stand-alone.
[0204] If the operation mode is in-band, an NB-IoT device (or UE)
may assume that an NRS is transmitted according to a criterion
described in Section I-1.
[0205] If the NB-IoT device (or UE) has not obtained information
about the operation mode of the corresponding cell yet, it may be
assumed that the NRS is transmitted according to the criterion
described in Section I-1.
[0206] The reason why the operation mode determines whether to use
the method as described above is that in the case of the guard band
operation mode and the stand-alone mode, the control region used
for the legacy LTE system is not configured, and thus the first and
second symbols may be used additionally. Also, since an NRS is
transmitted by using a larger number of symbols, an advantage is
obtained that the number of REs which may be used for an NB-IoT
device (or UE) to perform channel measurement or estimation is
increased.
[0207] I-2-1. NRS used in the first, second, and third symbols of
special subframe may be as follows.
[0208] Option a. The option a may determine to use a method for
generating an NRS used in a different downlink subframe and a
method for determining frequency domain resources.
[0209] A method for generating a sequence of the NRS may reuse an
existing method for generating an NRS sequence according to Eqs. 1
to 3.
[0210] The position of the NRS in the frequency domain may be
determined by the k value which determines a mapping position in
the frequency domain according to the method defined by Eq. 1.
[0211] At this time, the position of an applied time domain
resource may be determined as follows. [0212] In the first slot,
l=0, 1. This corresponds to the position indicating the first and
the second symbol of a special subframe. [0213] In the first slot,
l=1, 2. This corresponds to the position indicating the second and
the third symbol of the special subframe. [0214] In the first slot,
l=0, 1, 2.
[0215] At this time, when l=0, 1, it may be determined to use an
existing method for generating an NRS according to Eqs. 1 to 3.
[0216] At this time, when l=2, it may be determined to use a method
for generating an NRS mapped to the third symbol in Section
I-1.
[0217] Option b. The option b may determine to use a method for
generating an NRS newly defined for the first, second, and third
symbols of a special subframe and a frequency domain mapping
rule.
[0218] At this time, the newly defined NRS may be designed to form
a sequence of length 12 with reference to 12 resource elements
(REs) used by one symbol.
[0219] A sequence generated with reference to one symbol may be
mapped repeatedly onto three symbols used for NRS transmission in a
special subframe. At this time, a cover code which is intended for
distinguishing an antenna port or cell ID may be applied to each
symbol.
[0220] At this time, the cover code applied to the third symbol may
be determined to have a value of 1.
[0221] As one example of a sequence mapped to one symbol, the
Zadoff-Chu sequence may be used. At this time, the root index of
the Zadoff-Chu sequence may be determined by NNcellID which
distinguishes an NB-IoT cell ID.
[0222] As one example of a sequence mapped to one symbol, a Gold
sequence may be used. At this time, the C.sub.init value of the
Gold sequence may be determined by NNcellID which distinguishes an
NB-IoT cell ID.
[0223] The option a is advantageous in that an existing method may
be reused. When a method with a condition of l=0, 1, 2 of the
option a is used together, an advantage is obtained that even when
an NB-IoT device (or UE) does not know the operation mode, the NRS
of the third symbol may be estimated based on the method with a
condition of l-1. A method based on the option b may be aimed to
lower PAPR by using all of the REs when data are not transmitted to
the corresponding symbol. At this time, a method for generating an
NRS of the third symbol and a method for applying a cover code may
be intended for the NRS of the third symbol to be used even when an
NB-IoT device (or UE) does not know the operation mode.
[0224] I-3. Method for Transmitting NRS by Using the Sixth and
Seventh Symbols of Special Subframe
[0225] The present section proposes a method for transmitting an
NRS by using the sixth and seventh symbols of a special subframe.
At this time, the sixth and the seventh symbol refer to the symbols
appearing sixth and seventh on the special subframe,
respectively.
[0226] FIG. 12 illustrates a symbol to which an NRS is mapped
according to Section I-3.
[0227] The embodiment of FIG. 12 assumes a situation based on UL-DL
configuration#0 and special subframe configuration#1, but an NRS
may also be transmitted on the sixth and seventh symbols for the
case of a different TDD configuration.
[0228] A specific method to which the proposed specification is
applied may be described as follows.
[0229] I-3-1. Application method may be determined according to
special subframe configuration index
[0230] I-3-1-1. When a specific special subframe configuration is
used, the proposed method may not be applied.
[0231] The aforementioned specific special subframe configuration
may correspond to #0 and #5 of Table 2.
[0232] The aforementioned specific special subframe configuration
may be defined by a special subframe configuration where the length
of DwPTS is less than X symbols.
[0233] At this time, it is possible that X=3.
[0234] I-3-1-2. When a specific special subframe configuration is
used, and the special subframe among carriers available for NB-IoT
is designated as a valid subframe, an NRS may be transmitted.
[0235] The aforementioned specific special subframe configuration
may correspond to #1, #2, #3, #4, #6, #7, #8, and #9 of Table
2.
[0236] Option a. The aforementioned valid subframe is defined as a
subframe to which an NB-IoT device (or UE) expects an NPDCCH or
NPDSCH to be transmitted. This information may be delivered to an
NB-IoT device (or UE) through higher layer signaling such as one
using an SIB or an RRC signal.
[0237] Option b. The aforementioned valid subframe may be an
independent meaning defined only for a special subframe. In this
case, the valid subframe with respect to the special frame may be
defined as a subframe to which an NRS is transmitted irrespective
of transmission of an NPDCCH or an NPDSCH. This information may be
delivered to an NB-IoT device (or UE) through higher layer
signaling such as one using an SIB or an RRC signal.
[0238] In the case of a special subframe except for the valid
subframe delivered through higher layer signaling, information
about the special subframe to be transmitted dynamically by an NRS
through DCI may be delivered to an NB-IoT device.
[0239] When the information is delivered dynamically through DCI,
the delivery may be applied in conjunction with the option a or
option b.
[0240] The aforementioned available carrier may include an anchor
carrier from which an NB-IoT device (or UE) acquires
synchronization also include a non-anchor carrier configured
through higher layer signaling.
[0241] More specifically, in the case of special subframe
configuration#9, it is proposed as follows. [0242] It may be
determined that only the sixth symbol is used for NRS transmission.
This may be intended to guard a DwPTS slot available for the
special subframe configuration#9. [0243] Both of the sixth and
seventh symbols may be used for NRS transmission. This may be
intended to increase transmission of the NRS when there is no
significant difficulty in securing GAP.
[0244] The base station may determine whether to transmit an NRS to
the seventh symbol, and this information may be delivered to an
NB-IoT device (or UE) through higher layer signaling using an SIB
or an RRS signal.
[0245] In the method described above, the cases of special subframe
configuration#0 and #5 may be excluded from application since the
sixth and seventh symbols of the special subframe are not
configured to be in the DwPTS region. On the other hand, since the
special subframe may be used as the LTE PDSCH in the cases of
special subframe configuration#1, #2, #3, #4, #6, #7, #8, and #9,
information about whether the corresponding special subframe is
available for NB-IoT has to be provided.
[0246] I-3-1-3. When an NRS is transmitted from the sixth and
seventh symbols of a special subframe, it may be proposed as
follows.
[0247] A method for generating an NRS used in a different downlink
subframe and a method for determining a time-frequency domain
resource may determine to use a resource corresponding to a first
slot.
[0248] If a special subframe configuration#9 is used, and only the
sixth symbol is used for NRS transmission, a time resource to be
used may be determined only for the case where l=5.
[0249] I-3-1-4. Energy per resource element (EPRE) of an NRS
transmitted from the sixth and seventh symbols of a special
subframe may be configured separately from the EPRE of an NRS
transmitted from a different subframe.
[0250] At this time, the EPRE of an NRS transmitted from the
special subframe may be determined by an offset (or in the form of
a multiple) from the EPRE of an NRS transmitted from a different
subframe.
[0251] At this time, the EPRE of an NRS transmitted from the
special subframe may be delivered to an NB-IoT device (or UE)
through higher layer signaling using an SIB or an RRC signal.
[0252] The case where the EPRE of an NRS transmitted from a
different subframe is applied differently may be limited to the
case where an NPDCCH or NPDSCH is not transmitted to the
corresponding special subframe.
[0253] At this time, the base station may deliver information about
whether the corresponding special subframe is to be used as an
NPDCCH or NPDSCH through higher layer signaling using an SIB or an
RRC signal.
[0254] II. Second Disclosure: Uplink Reference Signal in a Special
Subframe
[0255] In the TDD scheme, the uplink transmission region of a
special subframe is limited to UpPTS region. In general, the UpPTS
is determined to have a symbol length of 1 or 2. A legacy LTE UE
may use the region for the purpose of an SRS or a PRACH. In the
case of NB-IoT, since the minimum unit for NPUSCH transmission is
fixed as a slot, the UpPTS of a special subframe may not be
appropriate for data transmission. Also, when intervals among
groups of symbols used as transmission units for NPRACH
transmission and hopping among the symbol groups are considered,
the UpPTS may not be appropriate for transmission of the NPRACH.
Also, the NB-IoT technology of up to release 14 does not define an
operation for transmitting an SRS.
[0256] To this regard, the present invention proposes a method to
be used for transmitting an uplink reference signal. More
specifically, the proposed method for transmitting an uplink
reference signal, when used for NB-IoT, may have the form and
purpose as an SRS is transmitted. The methods described below may
be used independently of each other or in the form of a combination
of one or more methods.
[0257] II-1. Method for Configuring to Transmit an SRS Only for a
Valid Special Subframe
[0258] A method proposed by the present specification may be
determined to operate only for a case where a special subframe is
configured as a valid subframe. At this time, a valid subframe
refers to a subframe configured by a base station, which allows an
NB-IoT device (or UE) to perform uplink transmission. At this time,
a valid subframe for an SRS works as information to indicate
whether each special subframe is allowed for uplink transmission,
which may be provided independently. This information may be
informed to an NB-IoT device (or UE) through higher layer signal
using an SIB or an RRC signal. If aperiodic SRS transmission is
configured by using an NPDCCH, information about a valid subframe
may be configured dynamically by using a predetermined area of
DCI.
[0259] II-2. Method for Transmitting an SRS to One or More Carriers
by Using Carrier Hopping
[0260] Since NB-IoT is designed to operate using one carrier (more
specifically, one PRB comprising 12 subcarriers), it may be
inappropriate to transmit an SRS to a plurality of carriers
simultaneously. Therefore, when a plurality of carriers (namely
anchor carrier and a plurality of non-anchor carriers) are
available, a method for transmitting an SRS is needed for carriers
to which an SRS may be transmitted. A method proposed in the
present section may include a method for hopping carriers to which
an SRS is transmitted to perform an SRS operation on a plurality of
carriers.
[0261] Carrier hopping may be performed on an anchor carrier and/or
non-anchor carriers configured for an NB-IoT device (or UE). At
this time, target carriers on which carrier hopping is performed
may be determined by a combination of one or more options given
below.
[0262] Option a. Carrier hopping is determined to be performed on
the carriers configured by an SIB so that an NB-IoT device (or UE)
may perform paging or NPRACH.
[0263] Option b. Carrier hopping may be performed on the carriers
configured separately through higher layer signaling using an SIB
or an RRC signal.
[0264] Option c. Carrier hopping may be performed on the carriers
configured separately through DCI.
[0265] Carrier hopping may not be performed while repeated
transmission is performed. When the number of repetitions that an
NB-IoT device (or UE) has to perform for each carrier to support
coverage is predetermined, carrier hopping may be determined not to
be performed while the corresponding repetitions are being
performed.
[0266] A carrier hopping pattern may be determined to have
different patterns for each cell. This may be intended to reduce
inter-cell interference.
[0267] II-3. Method for Transmitting a Periodic SRS of an
NB-IoT
[0268] An NB-IoT device (or UE) may transmit an SRS periodically.
To this purpose, a base station may deliver necessary information
through higher layer signaling using an SIB or an RRC signal. The
necessary information described above may include one or more of
the information given below. [0269] Period: A period for
transmitting an SRS may be specified. At this time, the period may
be defined as an interval between positions at which SRS
transmission is started. If SRS transmission is impossible because
the start position of SRS transmission specified by a period
corresponds to an invalid subframe, SRS transmission may be given
up on the corresponding UpPTS. [0270] Time offset: Information of a
time offset may be used for determining the position for
transmitting an SRS for the first time. For example, the time
offset may be determined so that the initial SRS transmission is
performed after a configured time offset measured from the moment
CDRX is completed. If SRS transmission is impossible because the
start position of SRS transmission specified through the time
offset corresponds to an invalid subframe, SRS transmission may be
given up on the corresponding UpPTS. If the period information is
applied, a period value may be applied after the SRS start position
configured by the time offset. [0271] Starting carrier: A carrier
from which SRS transmission is started may be determined. After the
starting carrier performs SRS transmission, a carrier to transmit
the SRS may be selected according to a carrier hopping pattern. At
this time, the starting carrier may be a carrier on which an NB-IoT
device (or UE) camps. Similarly, the starting carrier may always be
determined as an anchor carrier. Or the starting carrier may be a
specific carrier configured through higher layer signaling. [0272]
Repetition: Transmission of an SRS may be repeated on one or more
UpPTSs. This may be intended to obtain sufficient power required
for SRS transmission.
[0273] II-4. Method for Transmitting an Aperiodic SRS of an NB-IoT
Device
[0274] An NB-IoT device (or UE) may transmit an SRS aperiodically.
To this end, a base station may deliver necessary common
information to the NB-IoT device (or UE) through higher layer
signaling using an SIB or an RRC signal, and part of individual
information may be configured through DCI. If a periodic SRS is
configured, part of the necessary common information above may be
utilized for transmission of a periodic SRS. The necessary
individual information described above may include one or more
information defined in Section II-3.
[0275] II-5. Method for Determining Repetition According to the
Number of Symbols Comprising UpPTS
[0276] If the number of OFDM symbols available for an UpPTS is
larger than 2, an NB-IoT device (or UE) may transmit an SRS
repeatedly. At this time, the number of repetitions may be the same
as the number of OFDM symbols available in the UpPTS.
[0277] When repetition is applied, OFDM symbols belonging to one
UpPTS (or multiple UpPTSs) are regarded as belonging to one group,
and a cover code in units of OFDM symbols may be applied. This may
be intended for multiplexing a plurality of NB-IoT devices (or UEs)
within the same cell or for reducing inter-cell interference. At
this time, each NB-IoT device (or UE) may determine the cover code
type to be used by itself based on its ID (namely UE ID) or
information configured by the base station. The information may be
configured through higher layer signaling using an SIB or an RRC
signal; or configured dynamically through DCI when aperiodic SRS
transmission is configured by the NPDCCH.
[0278] II-6. Method for Resolving Collision with Other Channel
Having Different SRS Transmission Timing
[0279] If an NB-IoT device (or UE) detects DCI corresponding to a
downlink grant, an SRS may not be transmitted for a duration since
an NPDSCH is received until ACK/NACK is transmitted in response
thereto. Also, if an NB-IoT device (or UE) detects DCI
corresponding to an uplink grant, an SRS may not be transmitted
while NPUSCH transmission is performed. This may be intended to
reduce time required for frequency retuning and power
consumption.
[0280] A downlink SRS gap may be configured for a predetermined
time period after transmission of an NPUSCH (data and/or ACK/NACK),
which determines not to transmit an SRS. This may be intended to
guarantee the case where reception of an NPDSCH or transmission of
an NPUSCH is performed continuously through the next DCI.
[0281] When a resource for an NPRACH or a scheduling request is
configured, an SRS may be determined not to be transmitted for the
case of an UpPTS located right before the uplink subframe for which
the corresponding resource is configured. This is intended to
secure time for frequency retuning of an NB-IoT device (or UE).
[0282] II-7. Method for Specifying Subcarrier Allocation
[0283] In NB-IoT uplink transmission, uplink transmission using 1,
3, 6, and 12 subcarriers is possible. At this time, an NB-IoT
device (or UE) may be capable of supporting only one carrier.
Taking into account this feature, the present section may include a
method for distinguishing SRS transmission using 1, 3, 6, and 12
subcarriers.
[0284] II-7-1. When SRS transmission using one or more subcarriers
is allowed, SRS transmission methods corresponding to the
respective numbers of subcarriers may differ from each other.
[0285] At this time, the size of a subcarrier which transmits an
SRS may be different from each other in terms of SRS transmission
units comprising the subcarrier in the time domain.
[0286] For example, when an SRS is transmitted using 1, 3, 6, and
12 subcarriers, X1, X2, X3, or X4 UpPTS regions may be used as one
SRS unit, respectively.
[0287] When an SRS is transmitted by using one subcarrier, a
sequence may be composed in X1 UpPTS regions of the time domain.
This may be intended to identify different NB-IoT devices (or UEs)
within the same cell or reduce inter-cell interference.
[0288] II-7-2. When an SRS is transmitted by using one or more
subcarriers, SRS resources which transmits the SRS may be
configured separately according to the number of subcarrier
used.
[0289] At this time, one UpPTS symbol may be configured such that
its resources on the frequency domain are distinguished in the FDM
form to support SRS transmission using 1, 3, and 6 subcarriers.
[0290] At this time, a specific UpPTS may be used for supporting an
SRS which uses a specific subcarrier number.
[0291] At this time, information about SRS resources used may be
delivered to an NB-IoT device (or UE) through higher layer
signaling using an SIB or an RRC signal according to the size of
each subcarrier.
[0292] At this time, if SRS transmission is performed aperiodically
using an NPDCCH, the number of subcarriers to be selected by the
NB-IoT device (or UE) and information about SRS resources may be
delivered dynamically through DCI.
[0293] III. Third Disclosure: RS Configuration for Special Subframe
Configuration#10
[0294] According to the definition of frame structure type 2, the
total number of special subframe configurations available for the
TDD structure is 11. In particular, the special subframe
configuration#10, which is a new structure introduced since the
release-14, uses 6 OFDM symbols in the DwPTS region and 6 OFDM
symbols in the UpPTS region as a new CP criterion. More
specifically, the special subframe configuration#10 may determine
whether to transmit a CRS to the fifth symbol position of the DwPTS
region. If the base station supports the special subframe
configuration#10 for which CRS-less DwPTS has been configured,
legacy LTE UEs are unable to expect a CRS at the fifth OFDM symbol
of the DwPTS region from the corresponding base station. A primary
reason of the aforementioned structure is to minimize interference
imposed on UL transmission by the DwPTS region.
[0295] In what follows, when the subframe configuration#10 is used
for the NB-IoT TDD structure, RSs are used independently from each
other. The methods proposed below may be used separately or in the
form of a combination thereof. In what follows, unless described
specifically, descriptions below are related to the methods for RS
transmission with respect to the fifth OFDM symbol of the DwPTS
region.
[0296] III-1. Method for Transmitting an RS to the Fifth Symbol of
Special Subframe Configuration#10
[0297] The method proposed by the present section enables a base
station to transmit an RS to the position of the fifth symbol of a
DwPTS when the special subframe configuration#10 is configured and
an NB-IoT device to receive and use the RS. In general, an RS may
be used for the purposes of channel estimation and measurement and
provide higher accuracy as the RS density becomes higher (namely
the more the RSs become available).
[0298] Detailed descriptions of the proposed method may be as
follows.
[0299] III-1-1. The proposed method may be applied when the
operation mode of an NB-IoT is the in-band mode.
[0300] When the operation mode of an NB-IoT is the in-band same PCI
mode, the RS transmitted may be a CRS.
[0301] At this time, the transmitted CRS may be determined to
follow the CRS pattern and generation rule of the fifth OFDM symbol
of a downlink subframe.
[0302] When the operation mode of an NB-IoT is in-ban different PCI
(inband-DifferentPCI) mode, the RS transmitted may be an NRS.
[0303] At this time, the transmitted NRS may follow one of the
patterns and generation rules among OFDM symbols (for example, the
sixth and seventh symbols in a slot) including the NRS in the
downlink subframe.
[0304] At this time, the pattern to be selected and the generation
rule may be determined based on the sixth OFDM symbol when the
index of a special subframe is an odd number and the seventh OFDM
symbol when the index is an even number (or vice versa).
[0305] The reason for determining whether to transmit an RS
according to the operation mode as described above is that when the
operation mode is the guardband or standalone mode, there may be no
influence by a CRS-less DwPTS. Also, when the operation mode is the
in-band same PCI mode, an NB-IoT device, being aware of the
information about the CRS pattern and the generation rule, may
perform decoding by using the information. Also, the reason is that
when the operation mode is the in-band same PCI mode, the NB-IoT
device becomes able to transmit a CRS so that cross-subframe
channel estimation or symbol-level combining may be applied easily.
Also, when the operation mode is the inband-DifferentPCI mode,
since an NB-IoT device does not know the CRS pattern and the
generation rule, it regards the position of the CRS as an RE which
is not used normally. However, if the CRS-less DwPTS is configured,
it may be expected that an RS is not transmitted to the
transmission position of the CRS at the fifth symbol of the DwPTS.
Therefore, in this case, it may be determined that the position of
the corresponding CRS is used for mapping of an NRS which may be
recognized by an NB-IoT device.
[0306] III-1-2. The proposed method may be applied to the case
where a DwPTS region is configured as a valid subframe.
[0307] If a specific DwPTS is invalid, an NB-IoT device does not
expect an RS to be transmitted at the fifth OFDM symbol of the
corresponding DwPTS.
[0308] The proposed method may be applied only for the case where
actual data are transmitted to the DwPTS region.
[0309] The proposed method may be applied only for the case where
an NRS is included in a different OFDM symbol other than the fifth
OFDM symbol in the DwPTS region.
[0310] When an NB-IoT device does not know whether an NRS is
included in a different OFDM symbol other than the fifth OFDM
symbol in a specific DwPTS region, the corresponding NB-IoT device
does not expect a CRS to be transmitted in the corresponding DwPTS
region.
[0311] The reason why the proposed method allows RS transmission on
a valid subframe is that when a base station declares the
corresponding DwPTS region as valid, the corresponding DwPTS region
may be regarded as being allowed to be used for the purpose of
NB-IoT. Also, even when the base station declares a specific DwPTS
as valid, if actual data or an NRS is not transmitted to the
specific DwPTS, the base station may be regarded to intend to avoid
interference due to uplink transmission by skipping transmission in
the corresponding DwPTS.
[0312] III-1-3. The proposed method may be applied when
transmission of an NPDSCH granted through an NPDCCH is scheduled so
that transmission at a DwPTS may be performed.
[0313] At this time, the NPDCCH may be determined not to be
transmitted through the DwPTS.
[0314] At this time, whether NPDSCH transmission is allowed at the
DwPTS may be delivered to a UE through information included in the
DCI obtained through the NPDCCH. For example, the information may
include DCI bit, CRC masking value, and so on.
[0315] At this time, whether NPDSCH transmission is allowed at the
DwPTS may be determined according to the transmission length of the
NPDSCH delivered by the DCI.
[0316] The transmission length may refer to the repetition size of
the NPDSCH, the number of downlink subframes required to map one TB
to an RE, or a combination of both. More specifically, whether
NPDSCH transmission is allowed at the DwPTS may be determined for
the case where the transmission length is less than M subframes
with respect to a specific constant M. Or whether NPDSCH
transmission is allowed at the DwPTS may be determined for the case
where the number of DwPTSs involved in transmission of the NPDSCH
is less than N with respect to a specific constant N.
[0317] According to the method described above, an advantage is
obtained that a base station may dynamically control transmission
of the NPDSCH at the DwPTS depending on the situation. Also, when
the number of DwPTSs used for transmission of the NPDSCH is small
since the length of NPDSCH transmission is short, transmission of
the corresponding NPDSCH exerts relatively little influence, and
therefore, in this case, the transmission may be allowed.
[0318] III-1-4. The proposed method may be determined to be always
applied for the anchor carrier.
[0319] At this time, transmission may be determined only by higher
layer signaling.
[0320] In the case of an anchor carrier, since NPSS/NSSS is
transmitted periodically, the number of subframes capable of
transmitting an NRS may be relatively small compared with a
non-anchor carrier. Also, the more subframes to which an CRS and an
NRS are transmitted, the more advantageous to improve decoding
performance of SIB1-NB. Also, since an anchor carrier may be
regarded as a subframe allocated by the base station for NB-IoT, a
probability that downlink/uplink transmission for other purposes
occurs may be relatively low. Therefore, an in the proposed method,
it may be advantageous to always expect an RS in the DwPTS region
of the anchor carrier.
[0321] III-1-5. The proposed method may be applied when NPRACH
transmission is started within K subframes after DwPTS.
[0322] At this time, the K value may be a predefined value.
[0323] The proposed method may be applied to a carrier capable of
performing RRM measurement before a UE performs NPRACH.
[0324] The carrier may be determined as an anchor carrier.
[0325] The carrier may be determined as a carrier from which an
NB-IoT device expects to receive the second message (Msg2) (namely,
random access response) and/or fourth message (Msg4) of a random
access procedure.
[0326] An NB-IoT device needs to know its CE level accurately
Before performing the random access procedure (namely NPRACH). The
NB-IoT device may perform RRM measurement using an RS to measure
the CE level, and the proposed method may be intended to allow the
UE to secure more RSs to estimate the CE level under such a
situation.
[0327] III-2. Method for Not Transmitting an RS to the Fifth Symbol
of Special Subframe Configuration#10
[0328] According to the proposed method in this section, a base
station does not transmit an RS to the position of the fifth symbol
of a DwPTS, which may be recognized by an NB-IoT; and the RS at the
corresponding position may be made not to be used.
[0329] A specific example to which the proposed method is applied
may be as follows.
[0330] III-2-1. When actual data transmission is performed in the
DwPTS region, all of the REs of the fifth OFDM symbol of the
corresponding DwPTS may be used for the purpose of data
transmission.
[0331] In some cases, instead of increasing the density of RS,
securing a sufficient number of REs for data and lowering the code
rate may be more advantageous. Similarly, in terms of complexity of
a UE, instead of applying an RS differently according to the
situation, it may be more advantageous to always assume that an RS
is not available.
[0332] The embodiments of the present invention described above may
be implemented through various means. For example, embodiments of
the present invention may be implemented by hardware, firmware,
software, or a combination thereof. More specifically,
implementation of the embodiments will be described with reference
to related drawings.
[0333] FIG. 13 illustrates a block diagram of a wireless device and
a base station in which a disclosure of the present specification
is implemented.
[0334] Referring to FIG. 13, a wireless device 100 and a base
station 200 may implement the disclosure of the present
specification.
[0335] The wireless device 100 in the figure comprises a processor
101, memory 102, and transceiver 103. In the same manner, the base
station 200 comprises a processor 201, memory 202, and transceiver
203. The processor 101, 201, memory 102, 202, and transceiver 103,
203 may be implemented by the respective chips, or at least two or
more blocks/functions may be implemented through one chip.
[0336] The transceiver 103, 203 includes a transmitter and a
receiver. When a specific operation is performed, an operation of
only one of the transmitter and the receiver may be performed, or
both of the transmitter and receiver operations may be performed.
The transceiver 103, 203 may include one or more antennas
transmitting and/or receiving a radio signal. Also, the transceiver
103, 203 may include an amplifier for amplifying a reception signal
and/or transmission signal; and a bandpass filter for transmission
to a specific frequency band.
[0337] The processor 101, 201 may implement functions, processes
and/or methods proposed by the present specification. The processor
101, 201 may include an encoder and a decoder. For example, the
processor 101, 202 may perform an operation due to the methods
described above. The processor 101, 201 may include
application-specific integrated circuit (ASIC), other chipsets,
logic circuits, data processing apparatus and/or converter which
converts a baseband signal and a radio signal to each other.
[0338] The memory 102, 202 may include Read-Only Memory (ROM),
Random Access Memory (RAM), flash memory, memory card, storage
medium and/or other storage devices.
[0339] FIG. 14 is a detailed block diagram of a transceiver of a
wireless device of FIG. 13.
[0340] Referring to FIG. 14, a transceiver 110 comprises a
transmitter 111 and a receiver 112. The transmitter 111 comprises a
Discrete Fourier Transform (DFT) unit 1111, subcarrier mapper 1112,
IFFT unit 1113, CP inserting unit 1114, and wireless transmitting
unit 1115. The transmitter 111 may further comprise a modulator.
Also, for example, the transmitter 111 may further comprise a
scramble unit (not shown), modulation mapper (not shown), layer
mapper (not shown), and layer permutator, which may be disposed in
from of the DFT unit 1111. In other words, to prevent increase of
peak-to-average power ratio (PAPR), the transmitter 111 first makes
information go through the DFT 1111 before mapping a signal to a
subcarrier. A signal spread (or precoded in the same context) by
the DFT unit 1111 goes through subcarrier mapping through the
subcarrier mapper 1112 and is converted again to a time-series
signal through the Inverse Fast Fourier Transform (IFFT) unit
1113.
[0341] The DFT unit 1111 performs DFT on the input symbols to
produce symbols of complex-number symbols. For example, if Ntx
symbols are input (where Ntx is a natural number), its DFT size is
Ntx. The DFT unit 1111 may be called a transform precoder. The
subcarrier mapper 1112 maps the complex-number symbols to the
respective subcarriers in the frequency domain. The complex-number
symbols may be mapped to resource elements corresponding to a
resource block allocated for data transmission. The subcarrier
mapper 1112 may be called a resource element mapper. IFFT unit 1113
performs IFFT on the input symbols to produce a baseband signal for
data, which is a signal in the time domain. The CP inserting unit
1114 copies part of the trailing portion of the baseband signal for
data and inserts the part into the leading portion of the baseband
signal for data. Through CP insertion, inter-symbol interference
(ISI) and inter-carrier interference (ICI) may be prevented, and
thus orthogonality may be maintained even for multi-path
channels.
[0342] On the other hand, the receiver 112 may comprise a wireless
receiving unit 1121, CP removing unit 1122, FFT unit 1123, and
equalizing unit 1124. The wireless receiving unit 1121, CP removing
unit 1122, and FFT unit 1123 of the receiver 112 perform the
inverse roles of the wireless transmitting unit 1115, CP inserting
unit 1114, and the IFFT unit 1113 of the transmitter 111. The
receiver 112 may further comprise a demodulator.
* * * * *