U.S. patent application number 15/326021 was filed with the patent office on 2017-07-27 for method for receiving reference signal in wireless communication system and apparatus therefor.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Hyunho LEE, Hanjun PARK.
Application Number | 20170214508 15/326021 |
Document ID | / |
Family ID | 55400041 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170214508 |
Kind Code |
A1 |
LEE; Hyunho ; et
al. |
July 27, 2017 |
METHOD FOR RECEIVING REFERENCE SIGNAL IN WIRELESS COMMUNICATION
SYSTEM AND APPARATUS THEREFOR
Abstract
A method for receiving a reference signal for determining a
position in a wireless communication system, according to one
embodiment of the present invention, may comprise the steps of:
receiving positioning reference signal (PRS)-related configuration
information transmitted from a plurality of antenna ports; and, if
the PRS-related configuration information includes specific
information, measuring a reference signal time difference (RSTD) by
using only the PRS indicated by the PRS-related configuration
information.
Inventors: |
LEE; Hyunho; (Seoul, KR)
; PARK; Hanjun; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
55400041 |
Appl. No.: |
15/326021 |
Filed: |
August 26, 2015 |
PCT Filed: |
August 26, 2015 |
PCT NO: |
PCT/KR2015/008903 |
371 Date: |
January 12, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62042778 |
Aug 27, 2014 |
|
|
|
62172775 |
Jun 8, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0053 20130101;
G01S 5/02 20130101; H04L 5/0048 20130101; H04W 64/003 20130101;
G01S 5/0236 20130101; H04W 64/00 20130101; H04W 64/006 20130101;
H04L 5/0051 20130101; H04L 5/0035 20130101; H04W 24/10
20130101 |
International
Class: |
H04L 5/00 20060101
H04L005/00; H04W 64/00 20060101 H04W064/00; G01S 5/02 20060101
G01S005/02; H04W 24/10 20060101 H04W024/10 |
Claims
1. A method for receiving a reference signal for positioning in a
wireless communication system, the method comprising: receiving
positioning reference signal (PRS) related configuration
information transmitted from a plurality of antenna ports; and if
the PRS related configuration information includes specific
information, measuring a reference signal time difference (RSTD) by
using only the PRS indicated by the PRS related configuration
information.
2. The method according to claim 1, further comprising, if the PRS
related configuration information does not include specific
information, measuring a reference signal time difference (RSTD) by
using a cell-specific reference signal (CRS) and the PRS indicated
by the PRS related configuration information.
3. The method according to claim 1, wherein the specific
information includes at least one of information about an antenna
port used for the PRS transmission, information about a subframe in
which each antenna port transmits the PRS within a positioning
occasion for the PRS transmission, information about an orthogonal
cover code applied to each antenna port, or PRS RE mapping
information for each antenna port.
4. The method according to claim 1, wherein the PRS is multiplexed
and mapped to REs for each of the plurality of antenna ports.
5. The method according to claim 1, further comprising reporting
the measured RSTD to a serving cell.
6. A terminal configured to receive a reference signal for
positioning in a wireless communication system, the UE comprising:
a radio frequency (RF) unit; and a processor configured to control
the RF unit, wherein the processor is configured to receive
positioning reference signal (PRS) related configuration
information transmitted from a plurality of antenna ports and if
the PRS related configuration information includes specific
information, measure a reference signal time difference (RSTD) by
using only the PRS indicated by the PRS related configuration
information.
7. The terminal according to claim 6, wherein, if the PRS related
configuration information does not include specific information,
the processor is configured to measure a reference signal time
difference (RSTD) by using a cell-specific reference signal (CRS)
and the PRS indicated by the PRS related configuration
information.
8. The terminal according to claim 6, wherein the specific
information includes at least one of information about an antenna
port used for the PRS transmission, information about a subframe in
which each antenna port transmits the PRS within a positioning
occasion for the PRS transmission, information about an orthogonal
cover code applied to each antenna port, or PRS RE mapping
information for each antenna port.
9. The terminal according to claim 6, wherein the PRS is
multiplexed and mapped into REs for each of the plurality of
antenna ports.
10. The terminal according to claim 6, wherein the processor is
configured to report the measured RSTD to a serving cell.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wireless communication
system, and more particularly, to a method for receiving a
reference signal in a wireless communication system and an
apparatus therefor.
BACKGROUND ART
[0002] Various devices (e.g., smartphones, tablet PCs, etc.) and
technologies requiring Machine-to-Machine (M2M) communications and
high data throughputs continue to appear and tend to be
popularized. And, a data amount necessary to be processed on a
cellular network is increasing very fast. In order to meet the fast
increasing data processing requirement amount, technologies (e.g.,
carrier aggregation technology, cognitive radio technology, etc.)
for using more frequency bands efficiently and technologies (e.g.,
multi-antenna technology, multi-base station cooperation
technology, etc.) for increasing data capacity transmitted within a
limited frequency are developed. And, a communication environment
is evolved in a direction of increasing density of nodes accessible
by a nearby user equipment. A node means a fixed point capable of
transmitting/receiving a radio signal to/from a user equipment by
being equipped with at least one antenna. A communication system
equipped with nodes of high density can provide a user equipment
with a communication service of high performance by cooperation
between the nodes.
[0003] According to the multinode cooperative communication scheme
of performing communication with a user equipment using the same
time-frequency resource at a plurality of nodes, since each node
operates as an independent base station, such a scheme has
performance much better than that of an existing communication
scheme of performing communication with a user equipment without
mutual cooperation.
[0004] A multinode system performs a cooperative communication
using a plurality of nodes that operate as a base station (or,
access point), an antenna, an antenna group, a radio remote header
(RRH) and a radio remote unit (RRU). Unlike the existing center
concentrated antenna system having antennas concentrated on a base
station, a plurality of the nodes in the multinode system are
located in a manner of being spaced apart from each other over a
predetermined interval. A plurality of the nodes can be operated by
at least one base station or a base station controller configured
to control an operation of each node or schedule data to be
transmitted/received through each node. And, each of the nodes is
connected to the base station or the base station controller
configured to operate the corresponding node through a cable or a
dedicated line.
[0005] Such a multinode system may be regarded as a sort of MIMO
(multiple input multiple output) system in that distributed nodes
can communicate with single or multiple users by
transmitting/receiving different streams simultaneously. Yet, since
the multinode system transmits a signal using the nodes distributed
to various locations, a transmitting area supposed to be covered by
each antenna is reduced in comparison with antennas provided to an
existing centralized antenna system. Hence, compared to the
existing system capable of implementing the MIMO technology in the
centralized antenna system, the multinode system can reduce a
transmit power required for each antenna to transmit a signal.
Moreover, since a transmitting distance between an antenna and a
user equipment is reduced, a pathloss is reduced and a fast
transmission of data is enabled. Hence, transmission capacity and
power efficiency of a cellular system can be raised and a
communication performance of a relatively uniform quality can be
met irrespective of a location of a user equipment within a cell.
In the multinode system, since base station(s) or base station
controller(s) connected to a plurality of nodes cooperates for data
transmission/reception, a signal loss generated from a transmitting
process is reduced. In case that nodes located by being spaced
apart from each other over a predetermined distance perform
cooperative communication with a user equipment, correlation and
interference between antennas are reduced. Hence, according to the
multinode cooperative communication scheme, it is able to obtain a
high SINR (signal to interference-plus-noise ratio).
[0006] Owing to the advantages of the multinode system mentioned in
the above description, in order to extend a service coverage and
improve channel capacity and SINR as well as reduce a base station
establishment cost and a maintenance cost of a backhaul network in
a next generation mobile communication system, the multinode system
is used together with or substituted with the existing centralized
antenna system, thereby emerging as a new base of a cellular
communication.
DISCLOSURE
Technical Problem
[0007] An object of the present invention is to provide a method
for receiving a reference signal in a wireless communication system
and an operation related therewith.
[0008] It will be appreciated by persons skilled in the art that
the objects that could be achieved with the present invention are
not limited to what has been particularly described hereinabove and
the above and other objects that the present invention could
achieve will be more clearly understood from the following detailed
description.
Technical Solution
[0009] Provided is a method for receiving a reference signal for
positioning in a wireless communication system according to one
embodiment of the present invention comprises the steps of
receiving positioning reference signal (PRS) related configuration
information transmitted from a plurality of antenna ports; and if
the PRS related configuration information includes specific
information, measuring a reference signal time difference (RSTD) by
using only the PRS indicated by the PRS related configuration
information.
[0010] Additionally or alternatively, if the PRS related
configuration information does not include specific information,
the method may comprise measuring a reference signal time
difference (RSTD) by using a cell-specific reference signal (CRS)
and the PRS indicated by the PRS related configuration
information.
[0011] Additionally or alternatively, the specific information may
include at least one of information about an antenna port used for
the PRS transmission, information about a subframe in which each
antenna port transmits the PRS within a positioning occasion for
the PRS transmission, information about an orthogonal cover code
applied to each antenna port, or PRS RE mapping information for
each antenna port.
[0012] Additionally or alternatively, the PRS may be multiplexed
and mapped into REs for each of the plurality of antenna ports.
[0013] Additionally or alternatively, the method may further
comprise reporting the measured RSTD to a serving cell.
[0014] Provided is a terminal configured to receive a reference
signal for positioning in a wireless communication system according
to one embodiment of the present invention comprises a radio
frequency (RF) unit; and a processor configured to control the RF
unit, wherein the processor is configured to receive positioning
reference signal (PRS) related configuration information
transmitted from a plurality of antenna ports and if the PRS
related configuration information includes specific information,
measure a reference signal time difference (RSTD) by using only the
PRS indicated by the PRS related configuration information.
[0015] Additionally or alternatively, if the PRS related
configuration information does not include specific information,
the processor may be configured to measure a reference signal time
difference (RSTD) by using a cell-specific reference signal (CRS)
and the PRS indicated by the PRS related configuration
information.
[0016] Additionally or alternatively, the specific information may
include at least one of information about an antenna port used for
the PRS transmission, information about a subframe in which each
antenna port transmits the PRS within a positioning occasion for
the PRS transmission, information about an orthogonal cover code
applied to each antenna port, or PRS RE mapping information for
each antenna port.
[0017] Additionally or alternatively, the PRS may be multiplexed
and mapped to REs for each of the plurality of antenna ports.
[0018] Additionally or alternatively, the processor may be
configured to report the measured RSTD to a serving cell.
[0019] The above technical solutions are merely some parts of the
embodiments of the present invention and various embodiments into
which the technical features of the present invention are
incorporated can be derived and understood by persons skilled in
the art from the following detailed description of the present
invention.
Advantageous Effects
[0020] According to one embodiment of the present invention,
reception of a reference signal and measurement of the reference
signal can efficiently be performed in a wireless communication
system.
[0021] It will be appreciated by persons skilled in the art that
that the effects that can be achieved through the present invention
are not limited to what has been particularly described hereinabove
and other advantages of the present invention will be more clearly
understood from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention. In the drawings:
[0023] FIG. 1 is diagram illustrating an example of a radio frame
structure used in a wireless communication system;
[0024] FIG. 2 is diagram illustrating an example of a
downlink/uplink (DL/UL) slot structure in a wireless communication
system;
[0025] FIG. 3 is diagram illustrating an example of a downlink (DL)
subframe structure used in a 3GPP LTE/LTE-A system;
[0026] FIG. 4 is diagram illustrating an example of an uplink (UL)
subframe structure used in a 3GPP LTE/LTE-A system;
[0027] FIG. 5 is a diagram illustrating a PRS transmission
structure;
[0028] FIGS. 6 and 7 are diagrams illustrating RE mapping a PRS
(positioning reference signal);
[0029] FIG. 8 is a diagram illustrating PRS RE mapping frequency
shifted in accordance with physical cell ID;
[0030] FIG. 9 is a diagram illustrating multi-antenna port PRS RE
mapping according to CDM;
[0031] FIG. 10 is a diagram illustrating multi-antenna port PRS RE
mapping according to TDM and FDM;
[0032] FIG. 11 is a diagram illustrating multi-antenna port PRS RE
mapping according to TDM, FDM and CDM;
[0033] FIG. 12 is a diagram illustrating PRS RE mapping at MBSFN
subframe;
[0034] FIGS. 13 and 14 are diagrams examples of positioning
occasion allocation for a plurality of TPs having the same physical
cell ID;
[0035] FIG. 15 is a diagram illustrating an operation according to
one embodiment of the present invention; and
[0036] FIG. 16 is a block diagram illustrating an apparatus for
implementing the embodiment(s) of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. The accompanying drawings
illustrate exemplary embodiments of the present invention and
provide a more detailed description of the present invention.
However, the scope of the present invention should not be limited
thereto.
[0038] In some cases, to prevent the concept of the present
invention from being ambiguous, structures and apparatuses of the
known art will be omitted, or will be shown in the form of a block
diagram based on main functions of each structure and apparatus.
Also, wherever possible, the same reference numbers will be used
throughout the drawings and the specification to refer to the same
or like parts.
[0039] In the present invention, a user equipment (UE) is fixed or
mobile. The UE is a device that transmits and receives user data
and/or control information by communicating with a base station
(BS). The term `UE` may be replaced with `terminal equipment`,
`Mobile Station (MS)`, `Mobile Terminal (MT)`, `User Terminal
(UT)`, `Subscriber Station (SS)`, `wireless device`, `Personal
Digital Assistant (PDA)`, `wireless modem`, `handheld device`, etc.
A BS is typically a fixed station that communicates with a UE
and/or another BS. The BS exchanges data and control information
with a UE and another BS. The term `BS` may be replaced with
`Advanced Base Station (ABS)`, `Node B`, `evolved-Node B (eNB)`,
`Base Transceiver System (BTS)`, `Access Point (AP)`, `Processing
Server (PS)`, etc. In the following description, BS is commonly
called eNB.
[0040] In the present invention, a node refers to a fixed point
capable of transmitting/receiving a radio signal to/from a UE by
communication with the UE. Various eNBs can be used as nodes. For
example, a node can be a BS, NB, eNB, Pico-cell eNB (PeNB), home
eNB (HeNB), relay, repeater, etc. Furthermore, a node may not be an
eNB. For example, a node can be a radio remote head (RRH) or a
radio remote unit (RRU). The RRH and RRU have power levels lower
than that of the eNB. Since the RRH or RRU (referred to as RRH/RRU
hereinafter) is connected to an eNB through a dedicated line such
as an optical cable in general, cooperative communication according
to RRH/RRU and eNB can be smoothly performed compared to
cooperative communication according to eNBs connected through a
wireless link. At least one antenna is installed per node. An
antenna may refer to an antenna port, a virtual antenna or an
antenna group. A node may also be called a point. Unlink a
conventional centralized antenna system (CAS) (i.e. single node
system) in which antennas are concentrated in an eNB and controlled
an eNB controller, plural nodes are spaced apart at a predetermined
distance or longer in a multi-node system. The plural nodes can be
managed by one or more eNBs or eNB controllers that control
operations of the nodes or schedule data to be transmitted/received
through the nodes. Each node may be connected to an eNB or eNB
controller managing the corresponding node via a cable or a
dedicated line. In the multi-node system, the same cell identity
(ID) or different cell IDs may be used for signal
transmission/reception through plural nodes. When plural nodes have
the same cell ID, each of the plural nodes operates as an antenna
group of a cell. If nodes have different cell IDs in the multi-node
system, the multi-node system can be regarded as a multi-cell
(e.g., macro-cell/femto-cell/pico-cell) system. When multiple cells
respectively configured by plural nodes are overlaid according to
coverage, a network configured by multiple cells is called a
multi-tier network. The cell ID of the RRH/RRU may be identical to
or different from the cell ID of an eNB. When the RRH/RRU and eNB
use different cell IDs, both the RRH/RRU and eNB operate as
independent eNBs.
[0041] In a multi-node system according to the present invention,
which will be described below, one or more eNBs or eNB controllers
connected to plural nodes can control the plural nodes such that
signals are simultaneously transmitted to or received from a UE
through some or all nodes. While there is a difference between
multi-node systems according to the nature of each node and
implementation form of each node, multi-node systems are
discriminated from single node systems (e.g. CAS, conventional MIMO
systems, conventional relay systems, conventional repeater systems,
etc.) since a plurality of nodes provides communication services to
a UE in a predetermined time-frequency resource. Accordingly,
embodiments of the present invention with respect to a method of
performing coordinated data transmission using some or all nodes
can be applied to various types of multi-node systems. For example,
a node refers to an antenna group spaced apart from another node by
a predetermined distance or more, in general. However, embodiments
of the present invention, which will be described below, can even
be applied to a case in which a node refers to an arbitrary antenna
group irrespective of node interval. In the case of an eNB
including an X-pole (cross polarized) antenna, for example, the
embodiments of the preset invention are applicable on the
assumption that the eNB controls a node composed of an H-pole
antenna and a V-pole antenna.
[0042] A communication scheme through which signals are
transmitted/received via plural transmit (Tx)/receive (Rx) nodes,
signals are transmitted/received via at least one node selected
from plural Tx/Rx nodes, or a node transmitting a downlink signal
is discriminated from a node transmitting an uplink signal is
called multi-eNB MIMO or CoMP (Coordinated Multi-Point Tx/Rx).
Coordinated transmission schemes from among CoMP communication
schemes can be categorized into JP (Joint Processing) and
scheduling coordination. The former may be divided into JT (Joint
Transmission)/JR (Joint Reception) and DPS (Dynamic Point
Selection) and the latter may be divided into CS (Coordinated
Scheduling) and CB (Coordinated Beamforming). DPS may be called DCS
(Dynamic Cell Selection). When JP is performed, more various
communication environments can be generated, compared to other CoMP
schemes. JT refers to a communication scheme by which plural nodes
transmit the same stream to a UE and JR refers to a communication
scheme by which plural nodes receive the same stream from the UE.
The UE/eNB combine signals received from the plural nodes to
restore the stream. In the case of JT/JR, signal transmission
reliability can be improved according to transmit diversity since
the same stream is transmitted from/to plural nodes. DPS refers to
a communication scheme by which a signal is transmitted/received
through a node selected from plural nodes according to a specific
rule. In the case of DPS, signal transmission reliability can be
improved because a node having a good channel state between the
node and a UE is selected as a communication node.
[0043] In the present invention, a cell refers to a specific
geographical area in which one or more nodes provide communication
services. Accordingly, communication with a specific cell may mean
communication with an eNB or a node providing communication
services to the specific cell. A downlink/uplink signal of a
specific cell refers to a downlink/uplink signal from/to an eNB or
a node providing communication services to the specific cell. A
cell providing uplink/downlink communication services to a UE is
called a serving cell. Furthermore, channel status/quality of a
specific cell refers to channel status/quality of a channel or a
communication link generated between an eNB or a node providing
communication services to the specific cell and a UE. In 3GPP LTE-A
systems, a UE can measure downlink channel state from a specific
node using one or more CSI-RSs (Channel State Information Reference
Signals) transmitted through antenna port(s) of the specific node
on a CSI-RS resource allocated to the specific node. In general,
neighboring nodes transmit CSI-RS resources on orthogonal CSI-RS
resources. When CSI-RS resources are orthogonal, this means that
the CSI-RS resources have different subframe configurations and/or
CSI-RS sequences which specify subframes to which CSI-RSs are
allocated according to CSI-RS resource configurations, subframe
offsets and transmission periods, etc. which specify symbols and
subcarriers carrying the CSI RSs.
[0044] In the present invention, PDCCH (Physical Downlink Control
Channel)/PCFICH (Physical Control Format Indicator Channel)/PHICH
(Physical Hybrid automatic repeat request Indicator Channel)/PDSCH
(Physical Downlink Shared Channel) refer to a set of time-frequency
resources or resource elements respectively carrying DCI (Downlink
Control Information)/CFI (Control Format Indicator)/downlink
ACK/NACK (Acknowledgement/Negative ACK)/downlink data. In addition,
PUCCH (Physical Uplink Control Channel)/PUSCH (Physical Uplink
Shared Channel)/PRACH (Physical Random Access Channel) refer to
sets of time-frequency resources or resource elements respectively
carrying UCI (Uplink Control Information)/uplink data/random access
signals. In the present invention, a time-frequency resource or a
resource element (RE), which is allocated to or belongs to
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH, is referred to as a
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE or
PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. In the
following description, transmission of PUCCH/PUSCH/PRACH by a UE is
equivalent to transmission of uplink control information/uplink
data/random access signal through or on PUCCH/PUSCH/PRACH.
Furthermore, transmission of PDCCH/PCFICH/PHICH/PDSCH by an eNB is
equivalent to transmission of downlink data/control information
through or on PDCCH/PCFICH/PHICH/PDSCH.
[0045] FIG. 1 illustrates an exemplary radio frame structure used
in a wireless communication system. FIG. 1(a) illustrates a frame
structure for frequency division duplex (FDD) used in 3GPP
LTE/LTE-A and FIG. 1(b) illustrates a frame structure for time
division duplex (TDD) used in 3GPP LTE/LTE-A.
[0046] Referring to FIG. 1, a radio frame used in 3GPP LTE/LTE-A
has a length of 10 ms (307200 Ts) and includes 10 subframes in
equal size. The 10 subframes in the radio frame may be numbered.
Here, Ts denotes sampling time and is represented as Ts=1/(2048*15
kHz). Each subframe has a length of 1 ms and includes two slots. 20
slots in the radio frame can be sequentially numbered from 0 to 19.
Each slot has a length of 0.5 ms. A time for transmitting a
subframe is defined as a transmission time interval (TTI). Time
resources can be discriminated by a radio frame number (or radio
frame index), subframe number (or subframe index) and a slot number
(or slot index).
[0047] The radio frame can be configured differently according to
duplex mode. Downlink transmission is discriminated from uplink
transmission by frequency in FDD mode, and thus the radio frame
includes only one of a downlink subframe and an uplink subframe in
a specific frequency band. In TDD mode, downlink transmission is
discriminated from uplink transmission by time, and thus the radio
frame includes both a downlink subframe and an uplink subframe in a
specific frequency band.
[0048] Table 1 shows DL-UL configurations of subframes in a radio
frame in the TDD mode.
TABLE-US-00001 TABLE 1 Downlink- DL-UL to-Uplink config-
Switch-point Subframe number uration 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
[0049] In Table 1, D denotes a downlink subframe, U denotes an
uplink subframe and S denotes a special subframe. The special
subframe includes three fields of DwPTS (Downlink Pilot TimeSlot),
GP (Guard Period), and UpPTS (Uplink Pilot TimeSlot). DwPTS is a
period reserved for downlink transmission and UpPTS is a period
reserved for uplink transmission. Table 2 shows special subframe
configuration.
TABLE-US-00002 TABLE 2 Normal cyclic prefix in downlink Extended
cyclic prefix in downlink Special UpPTS UpPTS subframe Normal
cyclic Extended cyclic Normal cyclic Extended cyclic configuration
DwPTS prefix in uplink prefix in uplink DwPTS prefix in uplink
prefix in uplink 0 6592 T.sub.s 2192 T.sub.s 2560 T.sub.s 7680
T.sub.s 2192 T.sub.s 2560 T.sub.s 1 19760 T.sub.s 20480 T.sub.s 2
21952 T.sub.s 23040 T.sub.s 3 24144 T.sub.s 25600 T.sub.s 4 26336
T.sub.s 7680 T.sub.s 4384 T.sub.s 5120 T.sub.s 5 6592 T.sub.s 4384
T.sub.s 5120 T.sub.s 20480 T.sub.s 6 19760 T.sub.s 23040 T.sub.s 7
21952 T.sub.s 12800 T.sub.s 8 24144 T.sub.s -- -- -- 9 13168
T.sub.s -- -- --
[0050] FIG. 2 illustrates an exemplary downlink/uplink slot
structure in a wireless communication system. Particularly, FIG. 2
illustrates a resource grid structure in 3GPP LTE/LTE-A. A resource
grid is present per antenna port.
[0051] Referring to FIG. 2, a slot includes a plurality of OFDM
(Orthogonal Frequency Division Multiplexing) symbols in the time
domain and a plurality of resource blocks (RBs) in the frequency
domain. An OFDM symbol may refer to a symbol period. A signal
transmitted in each slot may be represented by a resource grid
composed of N.sub.RB.sup.DL/UL*N.sub.sc.sup.RB subcarriers and
N.sub.symb.sup.DL/UL OFDM symbols. Here, N.sub.RB.sup.DL denotes
the number of RBs in a downlink slot and N.sub.RB.sup.UL denotes
the number of RBs in an uplink slot. N.sub.RB.sup.DL and
N.sub.RB.sup.UL respectively depend on a DL transmission bandwidth
and a UL transmission bandwidth. N.sub.symb.sup.DL denotes the
number of OFDM symbols in the downlink slot and N.sub.symb.sup.UL
denotes the number of OFDM symbols in the uplink slot. In addition,
N.sub.sc.sup.RB denotes the number of subcarriers constructing one
RB.
[0052] An OFDM symbol may be called an SC-FDM (Single Carrier
Frequency Division Multiplexing) symbol according to multiple
access scheme. The number of OFDM symbols included in a slot may
depend on a channel bandwidth and the length of a cyclic prefix
(CP). For example, a slot includes 7 OFDM symbols in the case of
normal CP and 6 OFDM symbols in the case of extended CP. While FIG.
2 illustrates a subframe in which a slot includes 7 OFDM symbols
for convenience, embodiments of the present invention can be
equally applied to subframes having different numbers of OFDM
symbols. Referring to FIG. 2, each OFDM symbol includes
N.sub.RB.sup.DL/UL*N.sub.sc.sup.RB subcarriers in the frequency
domain. Subcarrier types can be classified into a data subcarrier
for data transmission, a reference signal subcarrier for reference
signal transmission, and null subcarriers for a guard band and a
direct current (DC) component. The null subcarrier for a DC
component is a subcarrier remaining unused and is mapped to a
carrier frequency (f0) during OFDM signal generation or frequency
up-conversion. The carrier frequency is also called a center
frequency.
[0053] An RB is defined by N.sub.symb.sup.DL/UL (e.g., 7)
consecutive OFDM symbols in the time domain and N.sub.sc.sup.RB
(e.g., 12) consecutive subcarriers in the frequency domain. For
reference, a resource composed by an OFDM symbol and a subcarrier
is called a resource element (RE) or a tone. Accordingly, an RB is
composed of N.sub.symb.sup.DL/UL*N.sub.sc.sup.RB REs. Each RE in a
resource grid can be uniquely defined by an index pair (k, l) in a
slot. Here, k is an index in the range of 0 to
N.sub.symb.sup.DL/UL*N.sub.sc.sup.RB-1 in the frequency domain and
l is an index in the range of 0 to N.sub.symb.sup.DL/UL-1.
[0054] Two RBs that occupy N.sub.sc.sup.RB consecutive subcarriers
in a subframe and respectively disposed in two slots of the
subframe are called a physical resource block (PRB) pair. Two RBs
constituting a PRB pair have the same PRB number (or PRB index). A
virtual resource block (VRB) is a logical resource allocation unit
for resource allocation. The VRB has the same size as that of the
PRB. The VRB may be divided into a localized VRB and a distributed
VRB depending on a mapping scheme of VRB into PRB. The localized
VRBs are mapped into the PRBs, whereby VRB number (VRB index)
corresponds to PRB number. That is, nPRB=nVRB is obtained. Numbers
are given to the localized VRBs from 0 to N.sub.VRB.sup.DL-1, and
N.sub.VRB.sup.DL=N.sub.RB.sup.DL is obtained. Accordingly,
according to the localized mapping scheme, the VRBs having the same
VRB number are mapped into the PRBs having the same PRB number at
the first slot and the second slot. On the other hand, the
distributed VRBs are mapped into the PRBs through interleaving.
Accordingly, the VRBs having the same VRB number may be mapped into
the PRBs having different PRB numbers at the first slot and the
second slot. Two PRBs, which are respectively located at two slots
of the subframe and have the same VRB number, will be referred to
as a pair of VRBs.
[0055] FIG. 3 illustrates a downlink (DL) subframe structure used
in 3GPP LTE/LTE-A.
[0056] Referring to FIG. 3, a DL subframe is divided into a control
region and a data region. A maximum of three (four) OFDM symbols
located in a front portion of a first slot within a subframe
correspond to the control region to which a control channel is
allocated. A resource region available for PDCCH transmission in
the DL subframe is referred to as a PDCCH region hereinafter. The
remaining OFDM symbols correspond to the data region to which a
physical downlink shared chancel (PDSCH) is allocated. A resource
region available for PDSCH transmission in the DL subframe is
referred to as a PDSCH region hereinafter. Examples of downlink
control channels used in 3GPP LTE include a physical control format
indicator channel (PCFICH), a physical downlink control channel
(PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc. The
PCFICH is transmitted at a first OFDM symbol of a subframe and
carries information regarding the number of OFDM symbols used for
transmission of control channels within the subframe. The PHICH is
a response of uplink transmission and carries an HARQ
acknowledgment (ACK)/negative acknowledgment (NACK) signal.
[0057] Control information carried on the PDCCH is called downlink
control information (DCI). The DCI contains resource allocation
information and control information for a UE or a UE group. For
example, the DCI includes a transport format and resource
allocation information of a downlink shared channel (DL-SCH), a
transport format and resource allocation information of an uplink
shared channel (UL-SCH), paging information of a paging channel
(PCH), system information on the DL-SCH, information about resource
allocation of an upper layer control message such as a random
access response transmitted on the PDSCH, a transmit control
command set with respect to individual UEs in a UE group, a
transmit power control command, information on activation of a
voice over IP (VoIP), downlink assignment index (DAI), etc. The
transport format and resource allocation information of the DL-SCH
are also called DL scheduling information or a DL grant and the
transport format and resource allocation information of the UL-SCH
are also called UL scheduling information or a UL grant. The size
and purpose of DCI carried on a PDCCH depend on DCI format and the
size thereof may be varied according to coding rate. Various
formats, for example, formats 0 and 4 for uplink and formats 1, 1A,
1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3A for downlink, have been defined
in 3GPP LTE. Control information such as a hopping flag,
information on RB allocation, modulation coding scheme (MCS),
redundancy version (RV), new data indicator (NDI), information on
transmit power control (TPC), cyclic shift demodulation reference
signal (DMRS), UL index, channel quality information (CQI) request,
DL assignment index, HARQ process number, transmitted precoding
matrix indicator (TPMI), precoding matrix indicator (PMI), etc. is
selected and combined based on DCI format and transmitted to a UE
as DCI.
[0058] In general, a DCI format for a UE depends on transmission
mode (TM) set for the UE. In other words, only a DCI format
corresponding to a specific TM can be used for a UE configured in
the specific TM.
[0059] A PDCCH is transmitted on an aggregation of one or several
consecutive control channel elements (CCEs). The CCE is a logical
allocation unit used to provide the PDCCH with a coding rate based
on a state of a radio channel. The CCE corresponds to a plurality
of resource element groups (REGs). For example, a CCE corresponds
to 9 REGs and an REG corresponds to 4 REs. 3GPP LTE defines a CCE
set in which a PDCCH can be located for each UE. A CCE set from
which a UE can detect a PDCCH thereof is called a PDCCH search
space, simply, search space. An individual resource through which
the PDCCH can be transmitted within the search space is called a
PDCCH candidate. A set of PDCCH candidates to be monitored by the
UE is defined as the search space. In 3GPP LTE/LTE-A, search spaces
for DCI formats may have different sizes and include a dedicated
search space and a common search space. The dedicated search space
is a UE-specific search space and is configured for each UE. The
common search space is configured for a plurality of UEs.
Aggregation levels defining the search space is as follows.
TABLE-US-00003 TABLE 3 Search space Aggregation Size Number of
PDCCH Type level L [in CCEs] candidates M.sup.(L) UE- 1 6 6
specific 2 12 6 4 8 2 8 16 2 Common 4 16 4 8 16 2
[0060] A PDCCH candidate corresponds to 1, 2, 4 or 8 CCEs according
to CCE aggregation level. An eNB transmits a PDCCH (DCI) on an
arbitrary PDCCH candidate with in a search space and a UE monitors
the search space to detect the PDCCH (DCI). Here, monitoring refers
to attempting to decode each PDCCH in the corresponding search
space according to all monitored DCI formats. The UE can detect the
PDCCH thereof by monitoring plural PDCCHs. Since the UE does not
know the position in which the PDCCH thereof is transmitted, the UE
attempts to decode all PDCCHs of the corresponding DCI format for
each subframe until a PDCCH having the ID thereof is detected. This
process is called blind detection (or blind decoding (BD)).
[0061] The eNB can transmit data for a UE or a UE group through the
data region. Data transmitted through the data region may be called
user data. For transmission of the user data, a physical downlink
shared channel (PDSCH) may be allocated to the data region. A
paging channel (PCH) and downlink-shared channel (DL-SCH) are
transmitted through the PDSCH. The UE can read data transmitted
through the PDSCH by decoding control information transmitted
through a PDCCH. Information representing a UE or a UE group to
which data on the PDSCH is transmitted, how the UE or UE group
receives and decodes the PDSCH data, etc. is included in the PDCCH
and transmitted. For example, if a specific PDCCH is CRC (cyclic
redundancy check)-masked having radio network temporary identify
(RNTI) of "A" and information about data transmitted using a radio
resource (e.g., frequency position) of "B" and transmission format
information (e.g., transport block size, modulation scheme, coding
information, etc.) of "C" is transmitted through a specific DL
subframe, the UE monitors PDCCHs using RNTI information and a UE
having the RNTI of "A" detects a PDCCH and receives a PDSCH
indicated by "B" and "C" using information about the PDCCH.
[0062] A reference signal (RS) to be compared with a data signal is
necessary for the UE to demodulate a signal received from the eNB.
A reference signal refers to a predetermined signal having a
specific waveform, which is transmitted from the eNB to the UE or
from the UE to the eNB and known to both the eNB and UE. The
reference signal is also called a pilot. Reference signals are
categorized into a cell-specific RS shared by all UEs in a cell and
a modulation RS (DM RS) dedicated for a specific UE. A DM RS
transmitted by the eNB for demodulation of downlink data for a
specific UE is called a UE-specific RS. Both or one of DM RS and
CRS may be transmitted on downlink. When only the DM RS is
transmitted without CRS, an RS for channel measurement needs to be
additionally provided because the DM RS transmitted using the same
precoder as used for data can be used for demodulation only. For
example, in 3GPP LTE(-A), CSI-RS corresponding to an additional RS
for measurement is transmitted to the UE such that the UE can
measure channel state information. CSI-RS is transmitted in each
transmission period corresponding to a plurality of subframes based
on the fact that channel state variation with time is not large,
unlike CRS transmitted per subframe.
[0063] FIG. 4 illustrates an exemplary uplink subframe structure
used in 3GPP LTE/LTE-A.
[0064] Referring to FIG. 4, a UL subframe can be divided into a
control region and a data region in the frequency domain. One or
more PUCCHs (physical uplink control channels) can be allocated to
the control region to carry uplink control information (UCI). One
or more PUSCHs (Physical uplink shared channels) may be allocated
to the data region of the UL subframe to carry user data.
[0065] In the UL subframe, subcarriers spaced apart from a DC
subcarrier are used as the control region. In other words,
subcarriers corresponding to both ends of a UL transmission
bandwidth are assigned to UCI transmission. The DC subcarrier is a
component remaining unused for signal transmission and is mapped to
the carrier frequency f0 during frequency up-conversion. A PUCCH
for a UE is allocated to an RB pair belonging to resources
operating at a carrier frequency and RBs belonging to the RB pair
occupy different subcarriers in two slots. Assignment of the PUCCH
in this manner is represented as frequency hopping of an RB pair
allocated to the PUCCH at a slot boundary. When frequency hopping
is not applied, the RB pair occupies the same subcarrier.
[0066] The PUCCH can be used to transmit the following control
information. [0067] Scheduling Request (SR): This is information
used to request a UL-SCH resource and is transmitted using On-Off
Keying (OOK) scheme. [0068] HARQ ACK/NACK: This is a response
signal to a downlink data packet on a PDSCH and indicates whether
the downlink data packet has been successfully received. A 1-bit
ACK/NACK signal is transmitted as a response to a single downlink
codeword and a 2-bit ACK/NACK signal is transmitted as a response
to two downlink codewords. HARQ-ACK responses include positive ACK
(ACK), negative ACK (HACK), discontinuous transmission (DTX) and
NACK/DTX. Here, the term HARQ-ACK is used interchangeably with the
term HARQ ACK/NACK and ACK/NACK. [0069] Channel State Indicator
(CSI): This is feedback information about a downlink channel.
Feedback information regarding MIMO includes a rank indicator (RI)
and a precoding matrix indicator (PMI).
[0070] The quantity of control information (UCI) that a UE can
transmit through a subframe depends on the number of SC-FDMA
symbols available for control information transmission. The SC-FDMA
symbols available for control information transmission correspond
to SC-FDMA symbols other than SC-FDMA symbols of the subframe,
which are used for reference signal transmission. In the case of a
subframe in which a sounding reference signal (SRS) is configured,
the last SC-FDMA symbol of the subframe is excluded from the
SC-FDMA symbols available for control information transmission. A
reference signal is used to detect coherence of the PUCCH. The
PUCCH supports various formats according to information transmitted
thereon.
[0071] Table 4 shows the mapping relationship between PUCCH formats
and UCI in LTE/LTE-A.
TABLE-US-00004 TABLE 4 Number of bits per PUCCH Modulation
subframe, format scheme M.sub.bit Usage Etc. 1 N/A N/A SR
(Scheduling Request) 1a BPSK 1 ACK/NACK or One codeword SR +
ACK/NACK 1b QPSK 2 ACK/NACK or Two codeword SR + ACK/NACK 2 QPSK 20
CQI/PMI/RI Joint coding ACK/NACK (extended CP) 2a QPSK + 21
CQI/PMI/RI + Normal CP BPSK ACK/NACK only 2b QPSK + 22 CQI/PMI/RI +
Normal CP QPSK ACK/NACK only 3 QPSK 48 ACK/NACK or SR + ACK/NACK or
CQI/PMI/RI + ACK/NACK
[0072] Referring to Table 4, PUCCH formats 1/1a/1b are used to
transmit ACK/NACK information, PUCCH format 2/2a/2b are used to
carry CSI such as CQI/PMI/RI and PUCCH format 3 is used to transmit
ACK/NACK information.
[0073] Generally, in a cellular communication system, various
methods for acquiring position information of a UE in a network are
used. Representatively, a positioning scheme based on OTDOA
(observed time difference of arrival) exists in the LTE system.
According to the positioning scheme, the UE may be configured to
receive PRS (positioning reference signal) transmission related
information of base stations from a higher layer signal, and may
transmit a reference signal time difference (RSTD) which is a
difference between a reception time of a PRS transmitted from a
reference base station and a reception time of a PRS transmitted
from a neighboring base station to a base station or network by
measuring PRS transmitted from cells in the periphery of the UE,
and the network calculates a position of the UE by using RSTD and
other information. In addition, other schemes such as an
A-GNSS(Assisted Global Navigation Satellite System) positioning
scheme, an E-CID(Enhanced Cell-ID) scheme, and a UTDOA(Uplink Time
Difference of Arrival) exist, and various location-based services
(for example, advertisements, position tracking, emergency
communication means, etc.) may be used based on these positioning
schemes.
[0074] [LTE Positioning Protocol]
[0075] In the LTE system, an LPP (LTE positioning protocol) has
been defined, and notifies the UE of OTDOA-ProvideAssistanceData
having the following configuration through IE (information
element).
TABLE-US-00005 -- ASN1START OTDOA-ProvideAssistanceData ::=
SEQUENCE { otdoa-ReferenceCellInfo OTDOA-ReferenceCellInfoOPTIONAL,
-- Need ON otdoa-NeighbourCellInfo OTDOA-NeighbourCellInfoList
OPTIONAL, -- Need ON otdoa-Error OTDOA-Error OPTIONAL, -- Need ON
... } -- ASN1STOP In this case, OTDOA-ReferenceCellInfo means a
cell which is a reference of RSTD measurement, and is configured as
follows. -- ASN1START OTDOA-ReferenceCellInfo ::= SEQUENCE {
physCellId INTEGER (0..503), cellGlobalId ECGI OPTIONAL, -- Need ON
earfcnRef ARFCN-ValueEUTRA OPTIONAL, --Cond NotSameAsServ0
antennaPortConfig ENUMERATED {ports1-or-2, ports4, ... } OPTIONAL,
-- Cond NotSameAsServ1 cpLength ENUMERATED { normal, extended, ...
}, prsInfo PRS-Info OPTIONAL, -- Cond PRS ..., [[ earfcnRef-v9a0
ARFCN-ValueEUTRA-v9a0 OPTIONAL -- Cond NotSameAsServ2 ]] } --
ASN1STOP
[0076] Meanwhile, OTDOA-NeighbourCellInfo means cells (for example,
eNB or TP) which is a target for RSTD measurement, and may include
information on maximum 24 neighboring cells per frequency layer
with respect to maximum three frequency layers. That is,
OTDOA-NeighbourCellInfo may notify the UE of information on a total
of 3*24=72 cells.
TABLE-US-00006 -- ASN1START OTDOA-NeighbourCellInfoList ::=
SEQUENCE (SIZE (1..maxFreqLayers)) OF OTDOA-NeighbourFreqInfo
OTDOA-NeighbourFreqInfo ::= SEQUENCE (SIZE (1..24)) OF OTDOA-
NeighbourCellInfoElement OTDOA-NeighbourCellInfoElement ::=
SEQUENCE { physCellId INTEGER (0..503), cellGlobalId ECGI OPTIONAL,
-- Need ON earfcn ARFCN-ValueEUTRA OPTIONAL, -- Cond NotSameAsRef0
cpLength ENUMERATED {normal, extended, ...} OPTIONAL, -- Cond
NotSameAsRef1 prsInfo PRS-Info OPTIONAL, -- Cond NotSameAsRef2
antennaPortConfig ENUMERATED {ports-1-or-2, ports-4, ...} OPTIONAL,
-- Cond NotsameAsRef3 slotNumberOffset INTEGER (0..19) OPTIONAL, --
Cond NotSameAsRef4 prs-SubframeOffset INTEGER (0..1279) OPTIONAL,
-- Cond InterFreq expectedRSTD INTEGER (0..16383),
expectedRSTD-Uncertainty INTEGER (0..1023), ..., [[ earfcn-v9a0
ARFCN-ValueEUTRA-v9a0 OPTIONAL -- Cond NotSameAsRef5 ]] }
maxFreqLayers INTEGER ::= 3 -- ASN1STOP
[0077] In this case, PRS-Info which is IE included in
OTDOA-ReferenceCellInfo and OTDOA-NeighbourCellInfo has PRS
information, and is specifically configured, as follows, as PRS
Bandwidth, PRS Configuration Index (IPRS), Number of Consecutive
Downlink Subframes, and PRS Muting Information.
TABLE-US-00007 PRS-Info ::= SEQUENCE { prs-Bandwidth ENUMERATED {
n6, n15, n25, n50, n75, n100, ... }, prs-ConfigurationIndex INTEGER
(0..4095), numDL-Frames ENUMERATED {sf-1, sf-2, sf-4, sf-6, ...},
..., prs-MutingInfo-r9 CHOICE { po2-r9 BIT STRING (SIZE(2)), po4-r9
BIT STRING (SIZE(4)), po8-r9 BIT STRING (SIZE(8)), po16-r9 BIT
STRING (SIZE(16)), ... } OPTIONAL -- Need OP } -- ASN1STOP
[0078] FIG. 5 illustrates a PRS transmission structure according to
the above parameters.
[0079] At this time, PRS Periodicity and PRS Subframe Offset are
determined in accordance with a value of PRS Configuration Index
(IPRS), and their correlation is as follows.
TABLE-US-00008 TABLE 5 PRS Configuration Index PRS Periodicity PRS
Subframe Offset (I.sub.PRS) (subframes) (subframes) 0-159 160
I.sub.PRS 160-479 320 I.sub.PRS - 160 480-1119 640 I.sub.PRS - 480
1120-23399 1280 I.sub.PRS - 1120
[0080] [PRS(Positioning Reference Signal)]
[0081] The PRS has a transmission occasion, that is, a positioning
occasion at a period of 160, 320, 640, or 1280 ms, and may be
transmitted for N DL subframes consecutive for the positioning
occasion. In this case, N may have a value of 1, 2, 4 or 6.
Although the PRS may be transmitted substantially at the
positioning occasion, the PRS may be muted for inter-cell
interference control cooperation. Information on such PRS muting is
signaled to the UE as prs-MutingInfo. A transmission bandwidth of
the PRS may be configured independently unlike a system bandwidth
of a serving base station, and is transmitted to a frequency band
of 6, 15, 25, 50, 75 or 100 resource blocks (RBs). Transmission
sequences of the PRS are generated by initializing a pseudo-random
sequence generator for every OFDM symbol using a function of a slot
index, an OFDM symbol index, a cyclic prefix (CP) type, and a cell
ID. The generated transmission sequences of the PRS are mapped to
resource elements (REs) depending on a normal CP or an extended CP
as shown in FIG. 6 (normal CP) and FIG. 7 (extended CP). A position
of the mapped REs may be shifted on the frequency axis, and a shift
value is determined by a cell ID. The positions of the REs for
transmission of the PRS shown in FIGS. 6 and 7 correspond to the
case that the frequency shift is 0.
[0082] The UE receives designated configuration information on a
list of PRSs to be searched from a position management server of a
network to measure PRSs. The corresponding information includes PRS
configuration information of a reference cell and PRS configuration
information of neighboring cells. The configuration information of
each PRS includes a generation cycle and offset of a positioning
occasion, and the number of continuous DL subframes constituting
one positioning occasion, cell ID used for generation of PRS
sequences, a CP type, the number of CRS antenna ports considered at
the time of PRS mapping, etc. In addition, the PRS configuration
information of the neighboring cells includes a slot offset and a
subframe offset of the neighboring cells and the reference cell, an
expected RSTD, and a level of uncertainty of the expected RSTD to
support determination of the UE when the UE determines a timing
point and a level of time window used to search for the PRS to
detect the PRS transmitted from the neighboring cell.
[0083] Meanwhile, the RSTD refers to a relative timing difference
between an adjacent or neighboring cell j and a reference cell i.
In other words, the RSTD may be expressed by
T.sub.subframeRxj-T.sub.subframeRxi, wherein T.sub.subframeRxj
refers to a timing point at which a UE starts to receive a specific
subframe from the neighboring cell j, and T.sub.subframeRxi refers
to a timing point at which a UE starts to receive a subframe, which
is closest to the specific subframe received from the neighboring
cell j in terms of time and corresponds to the specific subframe,
from the reference cell i. A reference point for an observed
subframe time difference is an antenna connector of the UE.
[0084] Although the aforementioned positioning schemes of the
related art are already supported by the 3GPP UTRA and E-UTRAN
standard (for example, (LTE Rel-9), higher accuracy is recently
required for an in-building positioning scheme. That is, although
the positioning schemes of the related art may commonly be applied
to outdoor/indoor environments, in case of E-CID scheme, general
positioning accuracy is known as 150 m in a non-LOS (NLOS)
environment and as 50 m in a LOS environment. Also, the OTDOA
scheme based on the PRS has a limit in a positioning error, which
may exceed 100 m, due to an eNB synchronization error, a multipath
propagation error, a quantization error in RSTD measurement of a
UE, and a timing offset estimation error. Also, since a GNSS
receiver is required in case of the A-GNSS scheme, the A-GNSS
scheme has a limit in complexity and battery consumption, and has a
restriction in using in-building positioning.
[0085] In this specification, a cellular network basically
transmits a specific pilot signal (for example, specific reference
signal type identifiable separately per base station/TP
(transmission point)) to the UE, and the UE calculates a
positioning related estimation value (for example, OTDOA and RSTD
estimation value) based on a specific positioning scheme by
measuring each pilot signal and then reports the calculated value
to the base station, whereby a method for calculating position
information of the corresponding UE at a base station terminal is
considered.
[0086] According to the LTE standard, the PRS is designed such that
the PRS is set to a single antenna port as shown in FIGS. 6 and 7
to calculate a positioning related estimation value of the UE.
However, as described above, to more improve positioning accuracy,
a method for transmitting the PRS from a plurality of antenna ports
may be considered. In this specification, a detailed method for
transmitting the PRS from a plurality of antenna ports will be
suggested.
[0087] PRS RE mapping according to the 3GPP LTE standard may be
shifted on the frequency axis in accordance with physical cell ID
as shown in FIG. 8. Referring to FIG. 8, the UE performs
positioning related measurement by using the PRS transmitted from
neighboring base stations/TPs, and to assist the positioning
related measurement of the UE, the PRS is mapped into different REs
in accordance with the physical cell ID to minimize interference
caused by the PRS transmitted from the neighboring base
stations/TPs. Therefore, it is not preferable that the PRS is
transmitted to REs which will be used by other base station/TP in
addition to REs designated to be used for PRS transmission by a
specific base station/TP. One embodiment of the present invention
suggests that various multiplexing schemes should be considered to
define a plurality of antenna ports for the PRS.
[0088] FIG. 9 is a diagram illustrating PRS RE mapping through
multi-antenna ports to which CDM (code division multiplexing) is
applied. In more detail, in FIG. 9, each antenna port of the PRS is
identified by applying CDM based on OCC (orthogonal cover code) to
REs, and a modulo value for physical cell ID of a transmission base
station is 0 and normal CP is used.
[0089] Supposing that 16 REs are used for PRS transmission within
one subframe, an OCC (for example, walsh code) designed to have
orthogonality may be used as a code multiplied by RE corresponding
to each antenna port. Although the OCC multiplied by the PRS is
mapped in a first frequency index mode in FIG. 9, the OCC may be
mapped in a first time mode or random mode as a modified example of
this embodiment. At this time, it will be apparent that mapping
patterns for mapping the orthogonal code into each antenna port
should be the same as one another. Also, as a modified type of
application of the OCC, the number of REs to which the OCC is
applied within one subframe may be reduced.
[0090] Alternatively, TDM (time division multiplexing) and FDM
(frequency division multiplexing) may be applied to each antenna
port without application of CDM as shown in FIG. 10, or CDM
together with TDM/FDM may be applied each antenna port as shown in
FIG. 11.
[0091] RE mapping per antenna port and the mapping patterns for the
OCC applied to each antenna port may be designated previously, or
may be configured by the base station for the UE, which will
perform positioning related estimation, through a higher layer (for
example, RRC signaling) within a given set.
[0092] According to the 3GPP LTE standard, the base station
transmits a CRS (cell-specific reference signal) from a non-MBSFN
(multicast and broadcast single frame network) area only at an
MBSFN subframe. Therefore, supposing that indexes of OFDM symbols
are 0 to 13 in FIG. 8, the UE does not expect that the CRS is
transmitted from the fourth, seventh and eleventh OFDM symbols. In
this respect, to improve positioning performance of LTE &
beyond UEs, the transmission base station may transmit the PRS to a
specific RE within the fourth, seventh and eleventh OFDM symbols if
a subframe designated to transmit the PRS is the MBSFN subframe.
FIG. 12 is an example that the PRS is transmitted from an RE
additionally designated at the MBSFN subframe. The LTE & beyond
UE may perform more improved positioning related measurement by
using the added PRS RE, and the legacy UE may perform positioning
related measurement by using the existing PRS mapping RE only
without considering RE, which will newly be used for PRS
transmission, without separate effect.
[0093] Also, the aforementioned CDM mode to which OCC is applied
and the aforementioned FDM+TDM+CDM mode may similarly be applied to
even the case that PRS transmission is performed at the MBSFN
subframe. At this time, RE mapping per antenna port and the mapping
patterns for the OCC applied to each antenna port may be designated
previously, or may be configured by the base station for the UE,
which will perform positioning related estimation, through a higher
layer (for example, RRC signaling) within a given set.
[0094] As another embodiment of the present invention, for advanced
positioning of higher accuracy, in addition to a macro cell, even
TP such as a small cell may transmit the PRS and the UE may perform
positioning related measurement. However, in this scenario, if a
plurality of RRHs (remote radio heads) below one base station use
the same physical cell ID as illustrated in a CoMP scenario 4, a
transmission sequence of the PRS is the same as a shift value on
the frequency axis related to RE mapping of the PRS, and the UE may
have a difficulty in identifying RRH that has transmitted the PRS
if a plurality of RRHs transmit the PRS at the same positioning
occasion. To solve this problem, methods for transmitting multi-PRS
from a plurality of TPs will be described.
[0095] As a first method, if TPs which use the same physical cell
ID desire to transmit the PRS, PRS transmission period and offset
may be transmitted by being divided from each other per TP as shown
in FIG. 13. However, this method causes a lot of positioning
occasions as the number of TPs is increased, whereby excessive
overhead may be caused.
[0096] As a second method, antenna ports are divided per TP as
shown in FIG. 14(a), whereby the PRS may simultaneously be
transmitted at the subframe within the same positioning occasion.
At this time, the aforementioned CDM mode or the aforementioned
TDM+FDM mode or the aforementioned TDM+FDM+CDM mode may be applied
such that the UE may identify each antenna port. The UE may perform
positioning related measurement for all antenna ports designated as
PRS transmission antenna ports at the positioning occasion
corresponding to corresponding physical cell ID.
[0097] As a third method, it is suggested that the PRS may be
transmitted at only a subframe scheduled per antenna port
corresponding to each TP among subframes within the same
positioning occasion as shown in FIG. 14(b). At this time, an
antenna port used for PRS transmission may be designated per
subframe and configured for the UE. As a simpler method, a given
number of subframes sequentially determined per TP may be used in
turn to transmit the PRS.
[0098] Alternatively, in the same manner as the first method, the
second method and the third method, in an environment configured
such that a specific TP transmits the PRS by using a specific
antenna port, the UE may be configured to perform and report
positioning related measurement per TP.
[0099] If a plurality of TPs having the same physical cell ID
transmit multi-antenna port PRS as above, the following information
for the PRS, which will be transmitted from each TP, should be
given to the UE using a higher layer signal. [0100] Antenna port
used for PRS transmission [0101] PRS transmission subframe within
positioning occasion [0102] OCC applied to each antenna port [0103]
PRS RE mapping for each antenna port
[0104] Although the above suggestions have been described for the
case that a plurality of TPs having the same physical cell ID
transmit multi-antenna port PRS, the suggestions may be applied to
even the case that a plurality of TPs having different physical
cell IDs desire to share the same positioning occasion by sharing
one PRS configuration index.
[0105] In respect of the aforementioned embodiments of the present
invention, detailed PRS related configuration information may be
defined as follows.
TABLE-US-00009 -- ASN1START PRS-Info ::= SEQUENCE { prs-Bandwidth
ENUMERATED { n6, n15, n25, n50, n75, n100, ... },
prs-ConfigurationIndex INTEGER (0..4095), numDL-Frames ENUMERATED
{sf-1, sf-2, sf-4, sf-6, ...}, prs-APConfig ENUMERATED {p1, p2, p3,
p4, p1-and-p2, p3-and- p4, ... } OPTIONAL, prs-SFPatternInfo CHOICE
{ sf2 BIT STRING (SIZE(2)), sf4 BIT STRING (SIZE(4)), sf6 BIT
STRING (SIZE(6)), ... } OPTIONAL, prs-OCCConfig ENUMERATED
{OCCpattern1, OCCpattern2, OCCpattern3, ... } OPTIONAL,
prs-RePatternInfo ENUMERATED {Repattern1, Repattern2, Repattern3,
... } OPTIONAL, ..., prs-MutingInfo-r9 CHOICE { po2-r9 BIT STRING
(SIZE(2)), po4-r9 BIT STRING (SIZE(4)), po8-r9 BIT STRING
(SIZE(8)), po16-r9 BIT STRING (SIZE(16)), ... } OPTIONAL -- Need OP
} -- ASN1STOP
[0106] In the above higher layer signals, prs-APConfig is an
indicator that includes information on an antenna port used for PRS
transmission. prs-SFPatternInfo is an indicator that includes
subframe information which will transmit PRS to a corresponding
antenna port within positioning occasion. prs-OCCConfig is an
indicator that includes OCC information applied to a corresponding
antenna port, and prs-RePatternInfo is an indicator that includes
PRS RE mapping information on a corresponding antenna port.
[0107] The above signaling may be configured to include PRS-Info
per TP, or may be configured to use one PRS-Info for a plurality of
TPs but include parameters identified per TP.
[0108] If at least one of the aforementioned parameters, that is,
prs-APConfig, prs-SFPatternInfo, prs-OCCConfig and
prs-RePatternInfo is configured, the UE performs positioning
related measurement by using the PRS only. Alternatively, an
explicit signal indicating that positioning related measurement
should be performed by the PRS only may be defined together with
the above parameter, whereby the UE performs positioning related
measurement by using the PRS only if the corresponding explicit
signal is given.
[0109] When the UE desires to perform positioning measurement,
particularly desires to measure RSTD for OTDOA based positioning,
the UE may use the PRS or may use the PRS and the CRS together. The
UE which can use these two methods (that is, method for using the
PRS only and the method for using the PRS and the CRS together) may
perform RSTD measurement by determining whether to use the PRS only
or both the PRS and the CRS.
[0110] In case of LTE Rel-9 OTDOA based positioning, although a
homogeneous network (that is, macro eNB exists as a serving cell)
has been considered, a heterogeneous network that small cells
coexist is recently considered. Particularly, if a plurality of
small cells (for example, femto cells) that is associated with one
macro cell and uses the same physical cell ID exist, small cells at
different positions transmit the CRS generated by the same physical
cell ID. If RSTD measurement based on the CRS is used for RSTD
measurement for a specific cell, accuracy of RSTD measurement may
be reduced.
[0111] For another example, if the CRS is used for RSTD measurement
even in case of a cell that does not transmit the CRS like a device
(for example, beacon that transmits PRS only) that transmits PRS
only, accuracy of RSTD measurement may be reduced.
[0112] Therefore, when specific measurement (for example, RSTD) is
configured, a signal indicating whether a corresponding cell may
use the CRS may be defined, and the UE which has received this
signal may perform RSTD measurement by using the CRS of the
corresponding cell or without using the CRS depending on
interpretation.
[0113] Alternatively, if the at least one parameter is configured
or the explicit signal indicating that positioning related
measurement should be performed by the PRS only is defined, or if
the signal indicating whether the corresponding cell may use the
CRS is defined, the UE may perform the RSTD measurement by using a
third reference signal of the cell corresponding to the CRS
together with the PRS.
[0114] Meanwhile, although prs-APConfig, prs-SFPatternInfo,
prs-OCCConfig and prs-RePatternInfo have been mentioned as the PRS
related parameters, these titles are only exemplary and may be
defined and used as other titles.
[0115] As still another embodiment of the present invention, the
aforementioned various multiplexing modes (for example, CDM,
TDM+FDM, and CDM+TDM+FDM) for the multi-antenna ports may be
applied to only a specific time/frequency domain or subframe set,
which has been defined or signaled previously.
[0116] As further still another embodiment of the present
invention, a mapping relationship between a subframe within the
positioning occasion and a specific antenna port for transmitting
the PRS may be defined previously or configured through signaling.
Or, a mapping relationship between the positioning occasion and a
specific antenna port for transmitting the PRS may be defined
previously or configured through signaling. Or, a mapping
relationship between a specific value generated by combination of
subframe index and physical cell ID (or virtual cell ID) within the
positioning occasion and a specific antenna port for transmitting
the PRS may be defined/scheduled previously or configured through
signaling. This configuration may also be applied to only a
specific time/frequency domain or subframe set, which has been
defined or signaled previously.
[0117] Since the examples for the aforementioned suggested method
may be included in one of the implementation methods of the present
invention, it will be apparent that the examples may be regarded as
kinds of the suggested methods. Also, the aforementioned suggested
methods may be implemented independently but may be implemented in
a combination (or merge) type of some of the suggested methods. A
rule may be defined to notify the UE of information (or information
on rules of the suggested methods) as to application of the
suggested methods, from a base station/position server through
signaling (for example, physical layer signal or higher layer
signal) which is previously defined.
[0118] FIG. 15 illustrates an operation according to one embodiment
of the present invention.
[0119] FIG. 15 relates to a method for receiving a reference signal
for positioning in a wireless communication system.
[0120] A UE 151 may receive positioning reference signal (PRS)
related configuration information transmitted from a plurality of
antenna ports (S1510). The UE may detect or measure the PRS by
using the PRS related configuration information (S1520). The PRS
may be mapped into resource elements (REs) for each of the
plurality of antenna ports by multiplexing.
[0121] Also, the PRS may be mapped into a specific RE within OFDM
symbols, into which the PRS is not mapped at a non-MBSFN subframe,
at an MBSFN subframe. An orthogonal cover code for code division
multiplexing (CDM) may be used for mapping of the RE, and may be
designated for each of the plurality of antenna ports.
[0122] The UE may receive information on the orthogonal cover code
for each of the plurality of antenna ports.
[0123] Also, the plurality of antenna ports may relate to a
plurality of transmission devices. If the plurality of transmission
devices use the same physical cell ID, each transmission device may
transmit the PRS through different ones among the plurality of
antenna ports. In this case, the UE may measure the PRS for each of
the plurality of transmission devices. Also, the PRS related
configuration information may include at least one of antenna port
information used for the PRS transmission, subframe information for
transmitting the PRS from each antenna port within a positioning
occasion for the PRS transmission, orthogonal cover code
information applied to each antenna port, and PRS RE mapping
information for each antenna port.
[0124] Also, the UE may report a detection or measurement result of
the PRS (S1530). The measurement result of the PRS may include a
measurement result of the PRS for each of the plurality of
transmission devices.
[0125] Although the embodiments according to the present invention
have been described as above with reference to FIG. 15, the
embodiment related to FIG. 15 may include at least a part of the
aforementioned embodiment(s) alternatively or additionally.
[0126] FIG. 16 is a block diagram of a transmitting device 10 and a
receiving device 20 configured to implement exemplary embodiments
of the present invention. Referring to FIG. 16, the transmitting
device 10 and the receiving device 20 respectively include radio
frequency (RF) units 13 and 23 for transmitting and receiving radio
signals carrying information, data, signals, and/or messages,
memories 12 and 22 for storing information related to communication
in a wireless communication system, and processors 11 and 21
connected operationally to the RF units 13 and 23 and the memories
12 and 22 and configured to control the memories 12 and 22 and/or
the RF units 13 and 23 so as to perform at least one of the
above-described embodiments of the present invention.
[0127] The memories 12 and 22 may store programs for processing and
control of the processors 11 and 21 and may temporarily storing
input/output information. The memories 12 and 22 may be used as
buffers. The processors 11 and 21 control the overall operation of
various modules in the transmitting device 10 or the receiving
device 20. The processors 11 and 21 may perform various control
functions to implement the present invention. The processors 11 and
21 may be controllers, microcontrollers, microprocessors, or
microcomputers. The processors 11 and 21 may be implemented by
hardware, firmware, software, or a combination thereof. In a
hardware configuration, Application Specific Integrated Circuits
(ASICs), Digital Signal Processors (DSPs), Digital Signal
Processing Devices (DSPDs), Programmable Logic Devices (PLDs), or
Field Programmable Gate Arrays (FPGAs) may be included in the
processors 11 and 21. If the present invention is implemented using
firmware or software, firmware or software may be configured to
include modules, procedures, functions, etc. performing the
functions or operations of the present invention. Firmware or
software configured to perform the present invention may be
included in the processors 11 and 21 or stored in the memories 12
and 22 so as to be driven by the processors 11 and 21.
[0128] The processor 11 of the transmitting device 10 is scheduled
from the processor 11 or a scheduler connected to the processor 11
and codes and modulates signals and/or data to be transmitted to
the outside. The coded and modulated signals and/or data are
transmitted to the RF unit 13. For example, the processor 11
converts a data stream to be transmitted into K layers through
demultiplexing, channel coding, scrambling and modulation. The
coded data stream is also referred to as a codeword and is
equivalent to a transport block which is a data block provided by a
MAC layer. One transport block (TB) is coded into one codeword and
each codeword is transmitted to the receiving device in the form of
one or more layers. For frequency up-conversion, the RF unit 13 may
include an oscillator. The RF unit 13 may include Nt (where Nt is a
positive integer) transmit antennas.
[0129] A signal processing process of the receiving device 20 is
the reverse of the signal processing process of the transmitting
device 10. Under the control of the processor 21, the RF unit 23 of
the receiving device 10 receives RF signals transmitted by the
transmitting device 10. The RF unit 23 may include Nr receive
antennas and frequency down-converts each signal received through
receive antennas into a baseband signal. The RF unit 23 may include
an oscillator for frequency down-conversion. The processor 21
decodes and demodulates the radio signals received through the
receive antennas and restores data that the transmitting device 10
wishes to transmit.
[0130] The RF units 13 and 23 include one or more antennas. An
antenna performs a function of transmitting signals processed by
the RF units 13 and 23 to the exterior or receiving radio signals
from the exterior to transfer the radio signals to the RF units 13
and 23. The antenna may also be called an antenna port. Each
antenna may correspond to one physical antenna or may be configured
by a combination of more than one physical antenna element. A
signal transmitted through each antenna cannot be decomposed by the
receiving device 20. A reference signal (RS) transmitted through an
antenna defines the corresponding antenna viewed from the receiving
device 20 and enables the receiving device 20 to perform channel
estimation for the antenna, irrespective of whether a channel is a
single RF channel from one physical antenna or a composite channel
from a plurality of physical antenna elements including the
antenna. That is, an antenna is defined such that a channel
transmitting a symbol on the antenna may be derived from the
channel transmitting another symbol on the same antenna. An RF unit
supporting a MIMO function of transmitting and receiving data using
a plurality of antennas may be connected to two or more
antennas.
[0131] In embodiments of the present invention, a UE serves as the
transmission device 10 on uplink and as the receiving device 20 on
downlink. In embodiments of the present invention, an eNB serves as
the receiving device 20 on uplink and as the transmission device 10
on downlink.
[0132] The transmitting device and/or the receiving device may be
configured as a combination of one or more embodiments of the
present invention.
[0133] The detailed description of the exemplary embodiments of the
present invention has been given to enable those skilled in the art
to implement and practice the invention. Although the invention has
been described with reference to the exemplary embodiments, those
skilled in the art will appreciate that various modifications and
variations can be made in the present invention without departing
from the spirit or scope of the invention described in the appended
claims. For example, those skilled in the art may use each
construction described in the above embodiments in combination with
each other. Accordingly, the invention should not be limited to the
specific embodiments described herein, but should be accorded the
broadest scope consistent with the principles and novel features
disclosed herein.
INDUSTRIAL APPLICABILITY
[0134] The present invention may be used for a wireless
communication apparatus such as a user equipment (UE), a relay and
an eNB.
* * * * *