Description
Title of Invention
RADIO COMMUNICATION DEVICE, RADIO COMMUNICATION METHOD,
AND RADIO COMMUNICATION SYSTEM
Technical Field
[OOOl]
The technology disclosed in the present description relates to a radio
10 communication device which serves as a base station, a radio communication method,
and a radio communication system in a radio communications environment in which
cells with different sizes are hierarchically structured, and particularly to a radio
communication device which reduces interference between the cells, a radio
communication method, and a radio communication system in a radio
15 communications environment in which the cells with different sizes are
hierarchically structured.
Background Art
[OOOZ]
20 At present, 3GPP (Third Generation Partnership Project) is workimg on
standardization of the 4th generation mobile communication system. "LTE (Long
Term Evolution)", which is one of the data communication specifications defined by
the 3GPP, is a long term advancement system aiming for 4th generation (4G) IMTAdvanced,
and is also referred to as "3.9G (super 3G)".
25 [0003]
In the LTE, 2 types of duplex methods, FDD (Frequency Division Duplex)
and TDD (Time Division Duplex) are available for selection. In the FDD, a band
dedicated for uplink and a band dedicated for downlink are used. For each of the
uplink and the downlink, a radio frame format including 10 contiguous subfratncs is
30 used. The uplink herein refers to communication from a terminal station (UE
terminal: User Equipment) to a base station of LTE (eNodeB: evolved Node B), and
the downlink refers to communication from an eNodeB to a UE terminal. In the
TDD, a radio frame format including 10 contiguous subframes is used, too.
However, in the TDD, the same band is used for communication in the uplink and the
downlink. Each subframe in a radio frame includes a control signal PDCCH (Fhy
5 Downlink Control Channel) from an eNodeB, and a PDSCH (Fhy Downlink Shared
Channel) which is used as user data.
[0004]
In the LTE, 1-cell reuse is applied, that is, one frequency is used by all the
cells in common. This is because using different frequencies between adjacent base
10 stations as in a conventional cellular causes a shortage of frequency resources. In
this case, a problem arises in that radio waves transmitted and received via UE
terminals around a cell cause interference. Thus, the LTE, which is the 3GPP Re1 8,
uses a technology called inter cell interference coordination (ICIC) in the Re1 8.
[OOOS]
15 The ICIC can be achieved, for example, by fractional frequency reuse which
is a combination of 1 cell frequency reuse and multiple cell frequency reuse. FIG.
14 illustrates the manner in which three cells 1 to 3, which perform fractional
frequency reuse, are adjacent to each other. In FIG. 14, the range of each cell is
indicated by a hexagon. In the fractional frequency reuse, each cell is divided into a
20 central area (unshaded area inside the cell) which is inside the cell and near an
eNodeB, and a peripheral area (shaded area at the edge of the cell) which is at the
edge of the cell and located away from the eNodeB. Although a "center frequency"
assigned to the communication between the eNodeB and UE terminals in the central
area causes a conflict (that is, 1-cell frequency reuse) between the cell and an
25 adjacent cell, the eNodeB avoids interference between the cells by reducing
transmission power so that signals can he transmitted only within the central area.
On the other hand, the eNodeB needs to use high power for transmission in order to
send signals to the peripheral area, and avoids interference between the cells by using
mutually different "peripheral frequencies" (that is, multiple cell frequency reuse) for
30 the peripheral areas of the cell and the adjacent cell. In the illustrated example, a 20
MHz band is divided into, for example, 3 bands, and peripheral frequencies are
reused so as not to overlap with each other between adjacent cells. In FIG 14,
differences between frequency bands are indicated by types of shading (diagonal line,
vertical shading line, horizontal shading line).
[0006]
5 In addition to the above-mentioned frequency reuse technology, in the ICIC
of the 3GPP Rel 8, a signal for reducing interference is exchanged between base
stations, that is, eNodeBs via the X2 interface. The X2 interface is an interface that
connects between eNodeBs, and is typified by a transmission medium such as an
optical fiber. Specifically, High Interference Indicator (HII) and Overload Indicator
10 (01) are each defmed as a message to be exchanged via the X2 interface.
[0007]
The HI1 is the information for informing an adjacent eNodeB of the location
of a resource block which is assigned to a UE terminal at the cell edge. I t i s
probable that the adjacent eNodeB is subject to interference from a resource block
15 specified by the HU. Thus, taking this into consideration, the adjacent cell performs
scheduling of the resource block. On the other hand, the 01 is the information for
informing of the level of interference of an uplink resource block, and has 3 levels
LowMediutnIHigh. When the adjacent eNodeB is informed by the 01 via the X2
interface that the level of interference to a certain resource block is High, the
20 adjacent eNodeB adjusts scheduling of the resource block, andlor uplink power
control.
[0008]
In this manner, the ICIC in the 3GPP Re18 adopts the adjustment method via
the X2 interface for the purpose of eliminating interference between macro cells.
25 The method, however, allows only the PDSCH in subframes to be adjusted, and the
PDCCH portion cannot be adjusted. This is because the PDCCH has a format
which allows the same band to be used between adjacent cells and is resistant to
interference.
[0009]
30 The ICIC in 3GPP Rel 10 will be described in the following. The ICIC in
the Re1 10 aims to reduce interference between a macro cell and a pica cell.
[OOl 01
In the 3GPP, a network referred to as HetNet has been studied in which
various sized cells such as MacrolMicro/Pico~emto are hierarchically structured to
increase the overall system capacity. For example, a Pico eNodeB, which is the
5 base station of a pico cell, has a characteristic that the transmission output thereof is
lower than the transmission output of a Macro eNodeB which is the base station of a
macro cell, of the order of tens of dB. It can be assumed that the X2 interface is
provided between the Macro eNodeB and the Pico eNodeB (in other words, the
interference of the PDSCH portion in subframes has been addressed by the ICIC in
10 the Re1 8). However, in some cases, it is necessary to assume that the X2 interface
between the Picoe NodeB and the Macro eNodeB has inferior characteristics of
speed, capacity, and delay compared with the X2 interface between Macro eNodeBs.
[OOll]
Because the transmission power from the Pico eNodeB is low, an increasing
15 number of areas will receive signals with higher power from the Macro eNodeB.
Even in an area where a loss in transmission from a pico cell is lower than a loss in
transmission from the Macro eNodeB (or an area which is closer in distance to the
Pico eNodeB than the Macro eNodeB), higher received power from the Macro
eNodeB often causes a UE terminal to attempt RRC (Radio Resource)_Connected to
20 the Macro eNodeB in a far distance rather than the Pico eNodeB in the vicinity.
However, uplink connection is advantageously made to a base station having a lower
transmission loss in consideration of consumption of the battery at the UE terminal,
and it is important to obtain a gain through cell division by assigning UE terminals to
the pic0 cell in a heterogeneous environment such as HetNet including combinations
25 of different types of cells. For these reasons, it is necessary to address the problem
that each UE terminal tends to be connected to the Macro eNodeB only.
[0012]
Thus, the Re1 10 defines a technology referred to as Range Expansion.
The Range Expansion will be described with reference to FIG. 15. A UE terminal,
30 when perfonning cell selection, that is, determining a base station to be associated
with, selects to be associated with an eNodeB having higher power, based on the
received power (RSRP: Reference Signal Received Power) obtained from a reference
signal (Cell-specific reference signal) from each eNodeB. When the RSRP is
evaluated for each eNodeB, for example, an offset of 10 dB is added to the RSRP of
the Pico eNodeB for the evaluation so that the area including UE terminals to be
5 associated with the Pico eNodeB is expanded. This is the Range Expansion and the
area of expanded portion is called a Range Expansion Area. The Range Expansion
Area is an area in which a UE terminal, which is originally to be associated with the
Macro eNodeB due to low RSRP from the Pica eNodeB, can be associated with the
Pico eNodeB thanks to an offset of RSRP, that is, the technology of the Range
10 Expansion.
[0013]
Some UE terminals in the Range Expansion Area may have higher received
power from the Macro eNodeB than that from the Pica eNodeB which is associated
with. In other words, the Range Expansion Area has a drawback in that the
15 reception from the Pico eNodeB by the UE terminals is susceptible to interference
from the Macro eNodeB. In the Range Expansion Area, a problem occurs of
downlink interference between the Pica eNodeB and the Macro eNodeB.
[0014]
For example, a communication system which controls interference to a
20 home base station device has been proposed, the communication system including a
mobile station, a base station device that manages macro cells, and the home base
station device that manages a femto cell, a pica cell, a nano cell, and a home cell (for
example, refer to Patent Literature I). However, the communication system does
not control downlink interference to the UE terminals in the Range Expansion Area.
25
Citation List
Patent Literature
[OOlS]
Patent Literature 1: JP 2011-77964A
Summary of Invention
Technical Problem
[0016]
It is an object of the technology disclosed in the present description to
provide an excellent radio communication device, a radio communication method,
5 and a radio communication system that are capable of preferably reducing
interference between cells, in a radio communications environment in which the cells
with different sizes are hierarchically structured.
[0017]
Another object of the technology disclosed in the present description is to
10 provide an excellent radio communication device, a radio communication method,
and a radio communication system that are capable of preferably reducing downlink
inter-cell interference to a terminal, in a radio communications environment in which
cells with different sizes are hierarchically structured, the radio communication
device serving as a base station.
15
Solution to Problem
[OOlS]
In the light of the foregoing issues, the present application has been
presented and according to the invention described in claim 1, there is provided a
20 radio communication device including an information acquisition unit configured to
acquire information of a frequency position at which predetermined indispensable
information is allocated in a data area of a downlink subframe transmitted by an
adjacent base station, and a virtual carrier transmission control unit configured to
transmit a virtual carrier in a data area of a downlink subframe of a current cell in a
25 manner that the virtual carrier does not overlap with the frequency position at which
the predetermined indispensable information is allocated, the virtual carrier having a
narrower band than a donor band.
[0019]
According to the technology described in claim 2 of the present application,
30 in the radio communication device according to claim 1, the subframes are
synchronized between the radio communication device and the adjacent base station.
[0020]
According to the technology described in claim 3 of the present application,
in the radio cotnmunication device according to claim 1, the subframes are not
synchronized between the radio communication device and the adjacent base station.
5 [0021]
According to the technology described in claim 4 of the present application,
there is provided a radio communication device including an information acquisition
unit configured to acquire information of a location at which predetermined
indispensable information is allocated in a data area of a downlink subframe
10 transmitted by an adjacent base station, and a virtual carrier operation unit configured
to prohibit operation of a virtual carrier in a data area of a downlink subframe of a
current cell, the downlink subframe overlapping with the subframe in which the
predetermined indispensable information is allocated, the virtual carrier having a
narrower band than a donor band.
15 [0022]
According to the technology described in claim 5 of the present application,
in the radio communication device according to claim 4, the subframes are
synchronized between the radio communication device and the adjacent base station.
[0023]
20 According to the technology described in claim 6 of the present application,
in the radio conununication device according to claim 4, the subframes are not
synchronized between the radio communication device and the adjacent base station.
[0024]
According to the technology described in claim 7 of the present application,
25 there is provided a radio communication device including an information acquisition
unit configured to acquire information of a location at which predetermined
indispensable information is allocated in a data area of a downlink subframe
transmitted by an adjacent base station, and a virtual carrier operation unit configured
to prohibit transmission of control information of a virtual carrier in a data area of a
30 downlink subframe of a current cell, the downlink subframe overlapping with the
subfsame in which the predetermined indispensable information is allocated, the
virtual carrier having a narrower band than a donor band.
[0025]
According to the technology described in claim 8 of the present application,
in the radio communication device according to claim 7, the subframes are
5 synchronized between the radio communication device and the adjacent base station.
[0026]
According to the technology described in claim 9 of the present application,
there is provided a radio communication device including an information acquisition
unit configured to acquire information of a frequency band in which a control area of
10 a virtual carrier is allocated in a data area of a downlink subframe by an adjacent
base station, the virtual carrier having a narrower band than a donor band, and a
subframe transmission control unit configured to transmit control information of a
downlink subframe of a current cell without overlapping with the frequency band in
which the control area of the virtual carrier is allocated by the adjacent base station.
15 [0027]
According to the technology described in claim 10 of the present application,
in the radio communication device according to claim 9, the subframes are not
synchronized between the radio communication device and the adjacent base station.
[0028]
20 According to the technology described in claim 11 of the present application,
there is provided a radio communication device including an information acquisition
unit configured to acquire information of a band included in a downlink subframe
transmitted by an adjacent base station, the information of the band carrying control
information for all terminals in the adjacent cell, and a virtual carrier transmission
25 control unit configured to transmit a control area of a virtual carrier in a data area of
a downlink subframe of a current cell in a manner that the control area does not
overlap with a band for transmitting the control information by the adjacent base
station, the virtual carrier having a narrower band than a donor band.
[0029]
30 According to the technology described in claim 12 of the present application,
in the radio communication device according to claim 11, the subframes are not
synchronized between the radio communication device and the adjacent base station.
[0030]
According to the technology described in claim 13 of the present application,
there is provided a radio communication method including a step of acquiring
5 information of a frequency position at which predetermined indispensable
information is allocated in a data area of a downlink subframe transmitted by an
adjacent base station, and a step of transmitting a vi~tuacl arrier in a data area of a
downlink snbframe of a current cell in a manner that the virtual carrier does not
overlap with the frequency position at which the predetermined indispensable
10 information is allocated, the virtual carrier having a narrower band than a donor band.
[003 l]
According to the technology described in claim 14 of the present application,
there is provided a radio communication method including a step of acquiring
information of a location at which predetermined indispensable information is
15 allocated in a data area of a downlink subframe transmitted by an adjacent base
station, and a virtual carrier operation step of prohibiting operation of a virtual carrier
in a data area of a downlink subframe of a current cell, the downlink subframe
overlapping with the subframe in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
20 [0032]
According to the technology described in claim 15 of the present application,
there is provided a radio communication method including a step of acquiring
information of a location at which predetermined indispensable information is
allocated in a data area of a downlink subframe transmitted by an adjacent base
25 station, and a virtual carrier operation step of prohibiting transmission of a virtual
carrier in a data area of a downlink subframe of a current cell, the downlink subfiame
overlapping with the subframe in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
[0033]
30 According to the technology described in claim 16 of the present application,
there is provided a radio cotnmunication method including a step of acquiring
information of a frequency band in which a control area of a virtual carrier is
allocated in a data area of a downlink suhframe by an adjacent base station, the
virtual carrier having a narrower band than a donor band, and a step of transmitting
control information of a downlink subframe of a current cell without overlapping
5 with the frequency band in which a control area C of the virtual carrier is allocated
by the adjacent base station.
100341
According to the technology described in claim 17 of the present application,
there is provided a radio communication method including a step of acquiring
10 information of a band included in a downlink subframe transmitted by an adjacent
base station, the information of the band carrying control information for all
terminals in the adjacent cell, and a step of transmitting a control area of a virtual
carrier in a data area of a downlink subframe of a current cell in a manner that the
control area does not overlap with a band for transmitting the control information by
15 the adjacent base station, the virtual carrier having a narrower hand than a donor
band.
[0035]
According to the technology described in claim 18 of the present application,
there is provided a radio communication system including a first base station
20 configured to allocate predetermined indispensable information at a predetermined
frequency position of a data area of a downlink subframe at a predetermined position
of a current cell, and a second base station configured to transmit a virtual carrier in
the data area of the downlink subframe of the curlent cell in a manner that the virtual
carrier does not overlap with the frequency position at which the predetermined
25 indispensable information is allocated, the virtual carrier having a narrower band
than a donor band.
[0036]
Here, the expression "system" refers to a logical grouping of a plurality of
apparatuses (and/or functional modules that realize specified functions), and does not
30 depend on such apparatuses andlor functional modules being present inside a single
housing (and the same hereinafter).
[0037]
According to the technology described in claim 19 of the present application,
there is provided a radio communication system including a first base station
configured to allocate predetermined indispensable information in a data area of a
5 downlink subframe at a predetermined position of a current cell, and a second base
station configured to prohibit operation of a virtual carrier in a data area of a
downlink subframe of a current cell, the downlink subframe overlapping with the
subframe in which the predetermined indispensable information is allocated, the
virtual carrier having a narrower band than a donor band.
lo [0038]
According to the technology described in claim 20 of the present application,
there is provided a radio communication system including a first base station
configured to allocate predetermined indispensable information in a data area of a
downlink subframe at a predetermined position of a current cell, and a second base
15 station configured to prohibit transmission of a virtual carrier in a data area of a
downlink subframe of a current cell, the downlink subframe overlapping with the
subframe in which the predetermined indispensable information is allocated, the
virtual carrier having a narrower band than a donor band.
[0039]
20 According to the technology described in claim 21 of the present application,
there is provided a radio communication system including a first base station
configured to transmit a virtual carrier at a predetermined frequency band of a data
area of a do\vnlink subframe of a cul-rent cell, the virtual carrier having a narrower
band than a donor band, and a second base station configured to transmit control
26 information of the downlink subframe of the current cell without overlapping with
the frequency band in which the control area of the virtual carrier is allocated by the
first base station.
[0040]
According to the technology described in claim 22 of the present application,
30 there is provided a radio communication system including a first base station
configured to transmit a subframe which includes control information for all
terminals in a current cell, and a second base station configured to transmit a control
area of a virtual carrier in a data area of a downlink subframe of the current cell in a
manner that the control area does not overlap with a band for transmitting the control
information by the first base station, the virtual carrier having a narrower band than a
5 donor band.
Advantageous Effects of Invention
[0041]
According to the technology disclosed in the present description, it is
10 possible to provide an excellent radio communication device, a radio communication
method, and a radio communication system that are capable of preferably reducing
downlink inter-cell interference to a terminal in the Range Expansion Area, in a radio
communications environment in which cells with different sizes are hierarchically
structured, the radio communication device serving as a base station.
15 [0042]
According to the technology disclosed in the present description, an
interference problem between Macro eNodeB and Pica eNodeB can be efficiently
solved, and thus the throughput of each cell can be improved.
[0043]
- 20 According to the technology disclosed in the present description, a virtual
carrier used in MTC can be preferably operated in a heterogeneous environment such
as HetNet including combinations of different types of cells.
[0044]
Other objects, features, and advantages of the technology according to the
25 present disclosure should be apparent from the following detailed description of the
embodiments and the appended drawings.
Brief Description of Drawings
[0045]
30 FIG. 11 FIG. 1 is a diagram illustrating the manner in which a control area
PDCCH-MTC for operating a narrow band and a data area PDSCH-MTC are
allocated in a data area PDSCH of a donor band.
[FIG 21 FIG. 2 is a diagram illustrating the case where a PDCCH-MTC of a Pico
eNodeB, and PSS, SSS of a Macro eNodeB overlap each another.
[FIG 31 FIG 3 is a diagram illustrating the manner in which a narrow band used by a
5 virtual carrier is allocated so as not to overlap with a center 72 sub carrier of the
donor band.
[FIG. 41 FIG. 4 is a diagram illustrating the manner in which the control area
PDCCH-MTC of the virtual carrier is prohibited from being allocated in a subframe
where the BCH, PSS, SSS are present.
10 FIG. 51 FIG. 5 is a diagram illustrating the manner in which the positions of the
PDCCH of the Macro eNodeB and the PDCCH-MTC of the Pico eNodeB overlap
each other.
FIG 61 FIG. 6 is a diagram illustrating the manner in which UE Specific Search
Space of the control area PDCCH on Macro eNodeB side is specified except for the
15 center 72 sub carrier which is used by the control area PDCCH - MTC on Pico
eNodeB side.
[FIG. 71 FIG. 7 is a diagram illustrating the manner in which the control area
PDCCH-MTC of tlie virtual carrier is allocated so as not to overlap with Common
Search Space of the PDCCH.
20 FIG. 81 FIG. 8 is a diagram illustrating the manner in which the control area
PDCCH-MTC of the virtual carrier is allocated so as not to overlap with the
Common Search Space of tlie PDCCH.
[FIG 91 FIG. 9 is a diagram schematically illustrating a configuration example of
radio communication device 900 which serves as the Pico eNodeB.
25 FIG. 101 FIG. 10 is a diagram schematically illustrating a configuration example of
radio communication device 1000 which operates as a UE terminal belonging to the
Pico eNodeB illustrated in FIG. 9.
[FIG. 111 FIG. 11 is a flow chart illustrating an operational procedure for using a
virtual carrier in a pico cell.
30 FIG 121 FIG. 12 is a diagram schetnatically illustrating a configuration example of
radio communication device 1200 which serves as Macro eNodeB.
FIG 131 FIG. 13 is a diagram schematically illustrating a configuration example of
radio communication device 1300 which serves as a UE terminal belonging to the
Macro eNodeB illustrated in FIG 12.
[FIG. 141 FIG. 14 is an illustration depicting the manner in which three cells 1 to 3,
5 which perform fractional frequency reuse, are adjacent to each other.
FIG. 151 FIG. 15 is an illustration for explaining the Range Expansion which is
defined in the 3GPP Re1 10.
FIG. 161 FIG. 16 is a diagram illustrating a configuration of a downlink radio frame
in the LTE.
10 FIG 171 FIG. 17 is a diagram illustrating locations at which the synchronization
signals PSS, SSS are inserted into a downlink subframe in FDD.
[FIG. 181 FIG. 18 is a diagram illustrating locations at which the synchronization
signals PSS, SSS are inserted into a downlink subframe in TDD.
FIG 191 FIG. 19 is a diagram illustrating a location at which the system information
15 BCH is inserted into a downlink subframe.
FIG 201 FIG 20 is a diagram illustrating the structure of a normal subframe.
[FIG 211 FIG. 21 is a diagram illustrating the structure of a subframe which is set as
a normal ABS.
[FIG. 221 FIG 21 is a diagram illustrating the structure of a subframe which is set as
20 an MBSFN type ABS.
[FIG 231 FIG. 23 is a diagram illustrating an example in which an offset is provided
behveen the subframes of the Macro eNodeB and the subframes of the Pica eNodeB.
[FIG 241 FIG. 24 is a diagram illustrating an example in which no offset is provided
between the subframes of the Macro eNodeB and the subframes of the Pica eNodeB.
25
Description of Embodiments
[0046]
Hereinaftel; an embodiment of the technology disclosed in the present
description will be described in detail with reference to the drawings.
30 [0047]
The LTE is a communication system based on OFDM modulation system,
and adopts OFDMA as a downlink radio access system. FIG 16 illustrates a
configuration of a downlink radio frame in the LTE. As illustrated, the radio kame
has 3 layers of hierarchy: time slot, subframe, and radio frame in increasing order of
time unit.
5 [0048]
A time slot with 0.5 millisecond length includes 7 OFDM symbols (in the
case of a normal unicast transmission) and serves as a unit of a demodulation
processing at the time of reception by a user (mobile station) side. A subframe with
1 millisecond length includes 2 contiguous time slots (14 OFDM symbols), and
10 serves as a transmission time unit for a data packet on which error correction coding
has been performed. A radio frame with 10 millisecond length includes 10
contiguous subframes (that is, 20 time slots), and serves as a basic unit for
multiplexing all physical channels. Tlie subframe is divided into a control area
PDCCH used for control signals from an eNodeB, and a data area PDSCH used for
15 user data.
[0049]
Users can communicate with each other without mutual interference by
using different sub carriers or different time slots. The LTE defines so-called
"resource hlock (RB)" which is a minimum unit of radio resource allocation and
20 obtained by grouping contiguous sub carriers in a block. A scheduler installed on a
base station allocates a radio resource to each user in units of resource blocks. The
resource block consists of 12 sub carriers x 1 time lot (7 OFDM symbols = 0.5
millisecond). A maximum of 3 OFDM symbols from the head of each subframe is
used for the control channel, that is, the PDCCH. The scheduler of the base station
25 can allocate a resource hlock evesy subframe interval, that is, 1 millisecond interval.
Position information of the resource block is called scheduling. Uplink scheduling
information and downlink scheduling information are both carried on a downlink
control channel. Each user can recognize the resource block allocated to the user by
referring to the control channel.
30 [0050]
A time slot of 0.5 milli length is the minimum allocation unit which can be
used by each user. The scheduler installed on the base station (eNodeB) allocates
usable time slots to each user in units of time slots. In the LTE, 2 types of
communication systems, FDD and TDD are available for selection. In the TDD,
whether the subfiame is used for uplink or downlink can be selected for each
5 subframe.
[0051]
As illustrated in FIG. 16, each downlink radio frame consists of 10
contiguous subframes, and a synchronization signal and system information are each
inserted at a predetermined position.
10 [0052]
The synchronization signal has 2 types: PSS (Primary Synchronization
Signal) and SSS (Secondary Synchronization Signal). The insertion position of a
synchronization signal in the subframes and OFDM symbols in the radio frame
varies depending on whether Duplex mode is FDD or TDD. In the FDD, as
15 illustrated in FIG 17, both PSS and SSS are inserted in the subframes #O and #5.
The PSS is inserted at the last OFDM symbol in the fist slot, and the SSS is inserted
at the last but one OFDM symbol. In the TDD, as illustrated in FIG. 18, the PSS is
inserted at the position of the 6th OFDM symbol from the head of the first slot in the
subfratnes #1 and #6, and the SSS is inserted at the last OFDM of the second slot in
20 the subframes #O and #5. In either case, the 72 sub carrier at the center of a usable
band is used. The synchronization signals PSS, SSS are first received by a UE
terminal, and thus can be considered to be the most important signals in all of the
downlink signals. If the synchronization signals cannot be received, the UE
terminal cannot perform a subsequent step to be associated with a cell.
25 [0053]
The system information includes ME3 (Master Information Block) and SIB
(System Information Block). The MTB stores indispensable information for
receiving data in a first stage, such as a bandwidth to be used, System Frame Number,
and a configuration of Hybrid ACK. Although the SIB includes other system
30 information and is important information, MIB is Inore important information. The
MIB is transmitted through a channel called BCH (Broadcast CHanncl). It is
defined that the SIB is to be transmitted through the PDSCH. In either case where
Duplex mode is FDD or TDD, as illustrated in FIG. 19, the BCH is insetted at the 4th
OFDM symbol from the head of the second slot in the subframe #0, and the center 72
sub carrier in the frequency band is used. Because the area of the BCH is very
5 important, it is significantly important to reduce interference to the BCH.
[0054]
Hereinafter, a downlink interference problem between a Pica eNodeB and a
Macro eNodeB in a Range Expansion Area defined in the 3GPP Re1 10 will be
discussed subsequent to the discussion in the section of "Background Art".
10 [OOSS]
As described above, for a UE terminal in the Range Expansion Area,
received power from a Macro eNodeB may be higher than the received power from
the Pico eNodeB which is associated with the UE terminal. That is, the Range
Expansion Area has a drawback in that the reception by the UE terminal is
15 susceptible to interference from the Macro eNodeB.
[0056]
As described above, it can be assumed that the X2 interface is present
between the Macro eNodeB and the Pico eNodeB, and so interference to the PDSCH
portion in each subframe has been addressed by the ICIC in the Re1 8. In the Range
20 Expansion Area, however, even though the PDSCH portion may be adjusted using
the ICIC technology in the Re1 8, a problem of interference to the PDCCH occurs.
[0057]
In the Re1 8, the PDCCH is designed to resist interference between Macro
eNodeBs which have comparable transmission outputs. However, in the Re1 10,
25 because RSRP is evaluated by the Range Expansion, a high power with several 10
dB higher than the power from the Pico eNodeB is transmitted from the Macro
eNodeB, thereby causing a problem that the PDCCH transmitted from the Picoe
NodeB is more likely to be susceptible to interference than the PDCCH transmitted
from the Macro eNodeB. Particularly, UE terminals belonging to the Range
30 Expansion Area are unable to receive the PDCCH from the Pico eNodeB.
[OOSS]
For this reason, the ICIC in the Rel 10 aims to reduce interference between
macro cells and pic0 cells. The ICIC in the Rel 10 has a solution by providing
some output-prohibited subframes out of 10 subframes in each radio frame
transmitted by the Macro eNodeB. The output-prohibited subframe is called ABS
5 (Almost Blank Subframe).
[0059]
FIG. 20 illustrates the structure of a normal snbframe. In FIG. 20, the
horizontal axis indicates time and the vertical axis indicates frequency. Each
subframe includes the control signal PDCCH from the eNodeB and the PDSCH
10 which is used as user data (described above). In the example of FIG. 20, the OFDM
symbols from the head to the third serve as the PDCCH, and the OFDM symbols on
the fourth and after serves as the PDSCH. A signal called CRS (Cell-Specific
Reference Signal) is inserted in both the PDCCH and the PDSCH. In FIG. 20, the
resource block portions colored in black each correspond to the CRS signal. Even
15 when a signal in a subframe for a normal download is attempted to be prohibited,
only the data in the PDSCH portion can be prohibited. Prohibition of the PDSCH
portion can be achieved by prohibiting the PDSCH from being allocated by the
scheduler of the eNodeB. However, the eNodeB cannot prohibit the CRS of the
PDSCH. Similarly, the eNodeB also cannot prohibit the Cell Specific Reference
20 Signal of the PDCCH. That is, CRS must be inserted in a normal subframe even
when an ABS is set. FIG 21 illustrates the structure of a subframe which is set as a
normal ABS, and only the resource block portion in which the CRS signal is not
inserted can be prohibited.
[0060]
25 In the 3GPP Rel 10, in order to prohibit even the CRS of the PDSCH, ABS
snbframe is set to be a subframe in MBSFN (Multimedia Broadband Single
Frequency Network). The subframe in MBSFN is a subframe which is used for
broadcast using SFN, and does not allow transmission of a normal CRS. The UE
terminal has a feature that ~vlvhen an MBSFN subframe is recognized, the UE terminal
30 does not need to receive the CRS of the PDSCH. The CRS of the PDSCH can be
prohibited by making a normal ABS subframe appear to be an MBSFN subframe for
the UE terminal. However, even in an MBSFN subframe, the CRS of the PDSCH
cannot be prohibited. FIG. 22 illustrates the structure of a subframe which is set as
an MBSFN type ABS, and the CRS of the PDSCH cannot be prohibited.
[0061]
5 In short, the Rel 10 includes 2 types of ABS: a normal ABS and an MBSFN
type ABS. As illustrated in FIG. 21, in a normal ABS subframe, only the PDCCH
and the CRS of the PDSCH remain and other resource block portions are not
transmitted. As illustrated in FIG 22, in a subframe of the MBSFN type ABS, only
the CRS of the PDCCH remains and other portions are not transmitted. In FIGS. 21
10 and 22, the resource block portions colored in black each correspond to a CRS signal,
and the white resource block portions correspond to the portions not to be transmitted.
[0062]
As described above, in the Range Expansion Area, reception from the Pico
eNodeB by the UE terminal is susceptible to interference from the Macro eNodeB.
15 On the other band, as illustrated in FIGS. 21 and 22, most part of a subframe set as
an ABS is not transmitted, and consequently a subframe of the Pico eNodeB is
resistant to interference, the subframe corresponding to a subfratne which is set as an
ABS by the Macro eNodeB. Therefore, the Pico eNodeB can perform downlink
communication efficiently while avoiding interference by allocating much resources
20 to each subframe which is set as an ABS by the Macro eNodeB, the resources being
directed to the UE terminal in the Range Expansion Area.
[0063]
The subframes of the Macro eNodeB and the Pico eNodeB can be operated
by providing an offset or by providing no offset between the subframes. FIG. 23
25 illustrates an example in which an offset is provided between the subframes of the
Macro eNodeB and the subframes of the Pico eNodeB. In the example of FIG. 23,
an offset by 7 subfiames is provided in time direction. FIG. 24 illustrates an
example in which no offset is provided behveen the subframes of the Macro eNodeB
and the subframes of the Pico eNodeB.
30 [0064]
As already described with reference to FIGS. 18 to 20, the synchronization
signals PSS, SSS and the system information BCH, which are very important for
reducing interference, are inserted at specific positions of the subframes in the radio
frame. The eNodeB cannot prohibit transmission of these signals. When no offset
is provided between the subfratnes as illustrated in FIG. 24, the insertion positions of
5 the subframes for the synchronization signals PSS, SSS and the system information
BCH are matched between the Macro eNodeB and the Pico eNodeB, and thus a
conflict therebetween cannot be avoided by setting an ABS by the Macro eNodeB.
[0065]
On the other hand, as illustrated in FIG. 23, with the operation by providing
10 an offset between the snbframes, the inseltion positions of the subframes for the
synchronization signals PSS, SSS and the system information BCH are different
between the Macro eNodeB and the Pico eNodeB. For example, it is sufficient for
the Pica eNodeB to provide an offset so as to be able to transmit the synchronization
signal PSS, SSS and the system information BCH with a subeame which is set as an
15 ABS by the Macro eNodeB. Consequently, in consideration of the signal
interference of the synchronization signals PSS, SSS and the system information
BCH between the eNodeBs, the operation of providing an offset between the
snbfratnes of the Macro eNodeB and the Pico eNodeB will probably be more
common.
20 [0066]
As additional remark, in a snbframe which has been set as an ABS,
transmission of both the PDCCH and the PDSCH is almost prohibited. The
interference to the PDSCH poltion in the subframes has been addressed by the ICIC
in the Re1 8 as described above. The reason why transmission of even the PDSCH
25 is prohibited nonetheless in the ABS is that the PDCCH includes the scheduling
information indicating which resource blocks are to be used for reception by each UE
terminal. It is not possible to transmit the PDSCH while prohibiting the
transmission of the PDCCH only.
[0067]
30 Hereinafter, a method of decoding the PDCCH will be described.
[0068]
Transmission of the PDCCH is performed in units of Resource Element
called CCE (Control Channel Element) consisting of 36 symbols. Because the
PDCCH is modulated by QPSK (Quadrature Phase Shift Keying), 72-bit information
can be transmitted per one unit of CCE. Aggregation, that is, repeated transmission
5 of the same information is applied to the CCE. The number of repeat, that is, CCE
Aggregation Level may have the following values: 1, 2,4, and 8. It is obvious that
SN is improved as the CCE Aggregation Level is increased. For a cell having a
larger radius, the CCE Aggregation Level is increased in order to prevent reduction
in SN.
10 [0069]
When the UE terminal cannot recognize the location of the CCE addressed
to the UE terminal, Blind decoding, that is, decoding is performed anyway. When a
CRC (Cyclic Redundancy Check) error does not occul; the UE terminal recognizes
that the CCE is addressed to itself. In the eNodeB, the CRC is assigned to each
15 CCE using a number specific to the UE terminal (UE identity = C-RNTI (Cell Radio
Network Temporary Identity), and thus when the CCE is checked for the CRC, an
error should occur in any UE terminal except for the corresponding UE terminal.
[0070]
The above-mentioned Blind decoding decodes all the CCEs inserted in the
20 control area PDCCH of the subframes, and a load for the UE terminal increases.
For this reason, Search Space has been introduced in the Re1 8. The Search Space
is divided into Common Search Space and UE Specific Search Space. The former
Common Search Space is contiguously allocated from the head of a candidate CCE.
The Common Search Space is present only when the CCE Aggregation Level = 4, 8
25 (in other words, the Common Search Space is present only when a cell has a large
radius). In addition, the area for the Common Search Space needs 16 CCEs.
Because each CCE has 36 symbols, 576 sub carriers from the first OFDM symbol in
increasing order of frequency correspond to the Common Search Space.
[0071]
30 The CCE in the UE Specific Search Space is encoded by masking the CRC
using the UE identity. Thus, the UE terminal performs Blind decoding on the UE
Specific Search Space, that is, perfoms the CRC check using its own UE identiy.
When a CRC error does not occur, the UE terminal can recognize that the CCE is
addressed to itself. All the UE terminals are configured to attempt to perform Blind
decoding on the Common Search Space using 2 identities, UE identity and Common
5 identity
[0072]
The eNodeB and each UE terminal have a common function (hash function)
for determining the location of the UE Specific Search Space. When a UE identity
and a subframe number are inputted to the function, the Search Space within the UE
10 Specific Search Space in the subframe, that is, the location of the CCE to he decoded
by the UE terminal can be obtained as the output of the function. The hash function
is a function which outputs a random looking value for an input (well known).
When a UE identity and a subframe number are inputted to the hash function, a
random looking area within a certain range is outputted. Therefore, when a UE
15 identity or a subframe is varied, a different Search Space is outputted from the hash
function in almost all cases. Even when the calculation of the function accidentally
generates the same Search Space for 2 or more UE terminals, it is highly probable
that the calculation generates different Search Spaces in the subsequent subfiame.
[0073]
20 - In the LTE, 6 types of bandwidths fiom 1.4 to 20 MHz are available for
selection. The number of sub carriers in each bandwidth is shown in the following
table 1.
[0074]
[Table 11
[0075]
In each bandwidth, the number of CCEs included in 1 OFDM symbol is the
value obtained by dividing the number of sub carriers by 36. Thus, when the
5 bandwidth is 20 MHz, it can be seen from the above table 1 that the number of CCEs
included in 1 OFDM symbol is 1201136 - approximately 33.
[0076]
By the way, a communication network has increasing application to an
object other than a common terminal such as a conventional cellular phone or a PC
10 (Personal Computer) which is directly accessed by a user. Hereinafter,
communication which is performed between machines and not directly accessed by a
user is referred to as MTC (Machine Type Communication), and a terminal which is
not directly accessed by a user for communication is referred to as an MTC terminal.
In general, the MTC is synonymous with the technology referred to as an M2M
15 (Machine to Machine). The antonym of M2M is H2H (Human To Human).
[0077]
The MTC terminal generally communicates with a server without human
intervention. For example, medical applications include transmission of medical
information to a server. That is, electrocardiograms of subjects are collected, and
20 when certain trigger conditions are met, the collected information is transmitted to
the server side using an uplink. Other applications include a vending machine. A
server side can order a vending machine to report sales for every fixed cycle (for
example, 30 days), the vending machine being managed by the server.
[0078]
The features of the MTC include, for example, the following:
[0079]
(1) Almost no movement involved.
5 (2) Small amount of data transfer.
(3) Extremely low power consumption.
(4) MTC terminals are grouped to be handled.
[OOSO]
Although the above-mentioned features are general, the MTC does not need
10 to have all the above features. Which combination of the above-mentioned features
is depends on application. It is also necessary to note that MTC can exhibit various
features.
[0081]
In contrast to a normal voice terminal, MTC is assumed to be mounted on a
15 device which involves no human intervention. Thus, it is expected that more MTC
terminals than the cellular phone terminals in number will be on the market in the
future.
[0082]
With an increasing number of MTC terminals, concerns are rising that
20 congestion may occur at a base station or in a core network due to transmission and
reception requests which are made to the base station all at once. In order to
promote the spread of the MTC terminals, reduction in cost is desired. In addition,
the MTC terminals and conventional cellular phone terminals need to be able to
coexist. Creating a new cellular network having only the MTC terminals is
25 impractical in terms of cost.
[0083]
As one of the methods to reduce the cost of the MTC terminal, the
frequency band used by the MTC terminal may be limited to a narrow band. This is
called "virtual carrier" or "narrow band operation". The LTE can have a maximum
30 bandwidth of 20 MHz (the maximum bandwidth is called a "donor band"). The
narrow band operation is a method of limiting the frequency band used by MTC
terminal to 1.4 MHz. In the conventional LTE terminals, the LTE terminal of
Category 1 is defined as the terminal which uses 1.4 MHz at the center, and only uses
the center frequency of 1.4 MHz. On the other hand, the narrow band operation
allows any 1.4 MHz band in 20 MHz bandwidth to be used.
5 [0084]
In the narrow band operation, the general view is that PDCCH serving as
control signals should be included in the area of conventional PDSCH. This is
because, in consideration of coexistence of the narrow band operation of MTC and
the conventional LTE standard, PDCCH at the time of the narrow band operation of
10 MTC should not be allocated in the area of conventional PDSCH. In addition,
because the number of terminals in MTC tends to increase, a problem also occurs in
that the resources for the conventional PDCCH may be exhausted. Consequently, it
is natural to assume that PDCCH in MTC is included in the area of PDSCH.
Hereinafter, the control area PDCCH in MTC is referred to as PDCCH-MTC. The
15 data area PDSCH in MTC is referred to as PDSCH-MTC.
[0085]
The interference problem between Macro eNodeB and Pica eNodeB can be
divided into two cases: one case where synchronization is perfect between eNodeBs
and the case where synchronization is not perfect between eNodeBs, and the other
20 case where the virtual carrier causes interference and the case where the virtual
carrier receives interference.
[0086]
Problem 1: interference from BCH, PSS, SSS to PDCCH-MTC. First, an
interference problem of the virtual carrier will be discussed, in the case where
25 synchronization is perfect between a Macro eNodeB and a Pica eNodeB (an offset is
provided in units of subframes (see FIG. 23), but no time difference is provided in
units of OFDM symbols).
[0087]
As described above, in order to reduce the cost for terminals in MTC,
30 operation of the narrow band (virtual carrier operation) is expected. In the
operation of the narrow band, any narrow band in the donor band of 20 MHz of the
eNodeB is selected. As illustrated in FIG 1, the control area PDCCH-MTC and the
data area PDSCH-MTC in the arrow band operation, that is, the virtual carrier are
both allocated in the data area PDSCH of the donor band. This is because MTC can
only receive the width of the narrow band, and so cannot receive all PDCCHs of the
5 donor band and decode them.
[OOSS]
Here, the virtual carrier including PDCCH-MTC and PDSCH-MTC is
assumed to be a carrier (that is, the virtual carrier is subject to interference)
transmitted from the Pico eNodeB (node having low power transmission).
10 [0089]
In the PDSCH in a predetermined subframe transmitted from the Macro
eNodeB, the system information BCH and the synchronization signals PSS, SSS are
inserted at the position of the center 72 sub carrier of the donor band (see FIGS. 17 to
19). Avoiding interference between these signals and the PDCCH-MTC
15 transmitted from the Pico eNodeB is a technical challenge to achieve the narrow
band operation of MTC. Normally, for the PDSCH in a subframe, an interference
area can be adjusted via the X2 interface which is prepared by the ICIC in the Re1 8
(described above). However, because the BCH, PSS, SSS are important
information, the Macro eNodeB cannot prohibit the transmission of these. On the
20 other hand, the control information for MTC is inserted in the PDCCH-MTC which
is subject to interference, thus when the PDCCH-MTC receives interference, a
problem arises in that the PDSCH-MTC cannot be transmitted and received.
[0090]
It should be reconfirmed that this problem concerns the influence of the
25 BCH, PSS, SSS of the Macro eNodeB on the virtual carrier of the Pico eNodeB.
For the virtual carrier in the Macro eNodeB, naturally, the virtual carrier is
transmitted without overlapping with the same locations as those of the BCH and
PSS, SSS of the Macro eNodeB, and so no problem arises.
[0091]
30 Now, a question may arise that when the positions of the BCH, PSS, SSS of
the Macro eNodeB are the same as those of the BCH, PSS, SSS of the Pico eNodeB
even between the Macro eNodeB and the Pico eNodeB, the PDCCH-MTC of the
Pico eNodeB is allocated so as not to overlap with the positions of the BCH, PSS,
SSS of the Pico eNodeB, and consequently, the PDCCH-MTC of the Pico eNodeB
does not overlap with the BCH, PSS, SSS of the Macro eNodeB.
5 [0092]
However, this question is not valid. As illustrated in FIG. 23, the ICIC in
the Re1 10 is expected to adopt the operation of providing an offset between the
subframes of the Macro eNodeB and the subfratnes of the Pico eNodeB. In this
case, although the boundaries between the subfiames are the same and synchronized
10 with each other (in units of OFDM symbols), the positions of the BCH, PSS, SSS of
the Macro eNodeB and the positions of the BCH, PSS, SSS of the Pico eNodeB are
different because of the offset provided. Therefore, there is a case where the
PDCCH-MTC of the Pico eNodeB overlaps with the BCH, PSS, SSS of the Macro
eNodeB. FIG. 2 illustrates the manner in which the PDCCH-MTC of the Pico
15 eNodeB overlaps with the PSS, SSS which are inserted in the PDSCH of the
subframes #0, #5 of the Macro eNodeB. In such a case, transmission of the BCH,
PSS, SSS of the Macro eNodeB cannot be prohibited (interference is adjusted via the
X2 interface) utilizing the ICIC in the Re1 8, thereby causing high interference to the
PDCCH-MTC of the Pico eNodeB. Interference to the PDSCH-MTC can be
20 avoided by the ICIC in the Re1 8, however, the interference to the PDCCH-MTC is
serious.
[0093]
Method 1-1 : proposed is an interference avoidance method by which the
vittual carrier is allocated so as not to overlap with the position of the center 72 sub
25 carrier of the donor band.
[0094]
FIG. 3 illustrates the manner in which the narrow band used by the virtual
carrier is allocated so as not to overlap with center 72 sub carrier of the donor band.
By using this method, the PDCCH-MTC is not allocated at the same locations in
30 frequency as those of the BCH, PSS, SSS, and thus interference from the BCH, PSS,
SSS to the PDCCH-MTC can be preferably avoided. FIG. 3 illustrates an example
in which the method is applied when synchronization between the Macro eNodeB
and the Pico eNodeB is perfect (an offset is provided in units of subfiames, but no
time difference is provided in units of OFDM symbols). Of course, the method can
be similarly applied even when synchronization is not perfect. FIG. 3 illustrates an
5 example in which the virtual carrier is operated by the Pico eNodeB side. The
method, however, can be applied even when the virtual carrier is operated by the
Macro eNodeB.
[0095]
The Pico eNodeB communicates with the Macro eNodeB through the X2
10 interface, S-GW (Serving Gateway), and MME (Mobility Management Entity) to
recognize the positions of the subframes, at which the control signal BCH and the
synchronization signals PSS, SSS are inserted by the Macro eNodeB side. In a
subframe of a current cell of the Pico eNodeB, which overlaps with the subframes
where the control signal BCH and the synchronization signals PSS, SSS are inserted
15 by the Macro eNodeB side, the Pico eNodeB transmits the virtual carrier so as not to
overlap with the center 72 sub carrier of the donor area where the BCH, PSS, SSS
are allocated.
100961
Method 1-2: proposed is an interference avoidance method by which the
20 operation of the virtual carrier is prohibited in a specific subframe.
[0097]
When the narrow band operation with the virtual carrier is allocated at the
center 72 sub carrier of the donor band, the operation is prohibited in the subframes
where the BCH, PSS, SSS are present. The subframes where the BCH, PSS, SSS
25 are present are different between downlink in FDD and downlink in TDD (see FIGS.
17 to 19). The cases of FDD and TDD will be separately described in the following.
[0098]
In the case of FDD, the operation of a virtual carrier is prohibited, the
virtual carrier being allocated at the center 72 sub carrier of the Pico eNodeB
30 corresponding to the subframes #0, #5 of the Macro eNDdeB. In the case of TDD,
the operation of a virtual carrier is prohibited, the virtual carrier being allocated at the
center 72 sub carrier of the Pico eNodeB corresponding to the subfiames #0, #I, #5,
#6 of the Macro eNodeB.
[0099]
The method can be applied when the synchronization between the Macro
5 eNodeB and the Pico eNodeB is perfect as well as when the synchronization is not
perfect therebetween. In addition, the method can be applied in both situations
when the virtual carrier is operated by the Macro eNodeB and when the virtual
carrier is operated by the Pico eNodeB.
[OlOO]
10 The Pico eNodeB communicates with the Macro eNodeB through the X2
interface, S-GW, and MME to recognize the positions of the subframes, at which the
control signal BCH and the synchronization signals PSS, SSS are inserted by the
Macro eNodeB side. The Pico eNodeB prohibits the operation of the virtual carrier
in the subframes of the current cell which are overlapped with the subfiames in
15 which the control signal BCH and the synchronization signals PSS, SSS are inserted
by the Macro eNodeB side.
[Ol 011
Method 1-3: proposed is an interference avoidance method by which the
control area PDCCH-MTC of the virtual carrier is prohibited so as not to overlap
20 with a specific subframe.
[O 1021
PDCCH-MTC is not transmitted in a subframe wvhich overlaps with the
subframes where BCH, PSS, SSS are present. However, the method 1-3 differs
from the method 1-2 in that the method 1-2 causes the operation of the entire virtual
25 carrier to be prohibited in the subfiames where BCH, PSS, SSS are present, whereas
the method 1-3 causes the transmission of the control area PDCCH-MTC to be
prohibited but allows the operation of the data area PDSCH-MTC to be performed.
FIG. 4 illustrates an example in wvhich the method 1-3 is applied when
synchronization between Macro eNodeB and Pico eNodeB is perfect (an offset is
30 provided in units of subframes, but no time difference is provided in units of OFDM
symbols). In the example of FIG. 4, the virtual carrier is operated by the Pico
eNodeB side, and Pico eNodeB prohibits the control area PDCCH-MTC of the
virtual carrier in the subframes where BCH, PSS, SSS are present on the Macro
eNodeB side. Of course, the method 1-3 can be applied even when the virtual
carrier is operated by Macro eNodeB. Here, interference between PDSCH-MTC
5 and BCH, PSS, SSS is avoided by the ICIC in the Re1 8 (interference is adjusted via
the X2 interface). Normally, the interference with BCH, PSS, SSS is reduced by a
method of reducing the transmission of PDSCH - MTC from Pico eNodeB.
[0103]
The Pico eNodeB communicates with the Macro eNodeB through the X2
10 interface, S-GW, and MME to recognize the positions of the subframes, at which the
control signal BCH and the synchronization signals PSS, SSS are inserted by the
Macro eNodeB side. In a subframe of the current cell of Pico eNodeB, which
overlaps with the subframes where the control signal BCH and the synchronization
signals PSS, SSS are inserted by the Macro eNodeB side, transmission of the control
15 area PDCCH - MTC of the virtual carrier is prohibited.
[0104]
FIG. 9 schematically illustrates a configuration example of a radio
communication device 900 which serves as the Pico eNodeB to achieve the abovedescribed
methods 1-1, 1-2, 1-3.
20 [0105]
The radio communication device 900 includes an RF communication
processing unit 901 to perform an analog processing on a radio signal which is
transmitted/received via an antenna, and a digital communication processing unit 902
to perform modulation processing on a digital transmission signal and demodulation
25 processing on a digital reception signal. The digital communication processing unit
902 exchanges transmission/reception data with an upper layer protocol of a
communication layer of the radio comtnunication device 900. In addition, the
digital communication processing unit 902 communicates with another eNodeB
through the X2 interface, S-GW, and MME.
30 [0106]
A Macro eNodeB subframe number identification unit 905 identifies the
subframe number on the Macro eNodeB side of a macro cell including the pic0 cell
(Range Expansion Area) of itself. A Pico eNodeB subframe number identification
unit 906 identifies the subframe number of the pic0 cell of itself.
[0107]
5 A virtual carrier subframe position determination unit 904 determines the
position of a subframe for transmitting the virtual carrier based on the subframe
number on the Macro eNodeB side and the subframe number of the pico cell. The
position of the subframe determined here is informed to a UE terminal (MTC
terminal) in the pico cell using, for example, a BCH signal.
lo [0108]
A virtual carrier control unit 903 controls the operation of the virtual carrier
based on a result determined by the virtual carrier subframe position determination
unit 904. In the method 1-1, when the current subframe number on the Macro
eNodeB side indicates a subframe including a signal such as BCH, PSS, SSS, the
15 virtual carrier subframe position determination unit 904 determines a frequency
position so as not to overlap with the center 72 sub carrier of the donor band. In the
method 1-2, when the current subframe number on the Macro eNodeB side indicates
a subframe including a signal such as BCH, PSS, SSS, the virtual carrier subframe
position determination unit 904 determines to prohibit the operation of the virtual
20 carrier. In the method 1-3, when the current subframe number on the Macro
eNodeB side indicates a subframe including a signal such as BCH, PSS, SSS, the
virtual carrier subframe position determination unit 904 determines prohibit the
transmission of the control area PDCCILMTC of the virtual carrier and to reduce the
transmission of the PDSCH-MTC by adjustment via the X2 interface.
25 [0109]
FIG. 10 schematically illustrates a configuration example of the radio
communication device 1000 which serves as a UE terminal (MTC terminal)
belonging to the Pico eNodeB illustrated in FIG. 9.
[OllO]
30 The radio conunuuication device 1000 includes an RF communication
processing unit 1001 to perfom an' analog processing on a radio signal which is
transmittedlreceived via an antenna, and a digital communication processing unit
1002 to perform modulation processing on a digital transmission signal and
demodulation processing on a digital reception signal. The digital communication
processing unit 1002 exchanges transmissionlreception data with an upper layer
5 protocol of a communication layer of the radio communication device 1000.
[ O l l l ]
The radio communication device 1000 is informed of the position of a
subframe for transmitting the virtual carrier from the Pico eNodeB, for example, by a
BCH signal. The virtual carrier subframe position holding unit 1003 stores the
10 position of a subframe in the pic0 cell including itself, the subframe having the
virtual carrier inserted therein. The digital communication processing unit 1002
performs reception processing for the virtual carrier at the position of the subframe in
which the virtual carrier is inserted.
[0112]
15 FIG. 11 illustrates an operational procedure in a flow chart format for
operating the virtual carrier in the pico cell.
[0113]
The Pico eNodeB determines the position of a subframe for transmitting the
virtual carrier in the pic0 cell of itself (step S1101).
20 [0114]
Subsequently, the Pico eNodeB informs a UE terminal (MTC terminal) in
the current cell of the above-mentioned information determined in step Sl I01 using a
BCH signal (step S1102).
[0115]
25 The UE terminal (MTC terminal) then recognizes the position of a subframe
in which the virtual carrier is inserted and performs reception processing (step
S1103).
[0116]
Problem 2 : interference from PDCCH to PDCCH-MTC
30 Here, the virtual carrier including the PDCCH-MTC and the PDSCH-MTC is
assumed to be a carrier (that is, the virtual carrier is subject to interference)
transmitted from a Pico eNodeB (node having low power transmission). However,
a similar problem arises even when the virtual carrier causes interference, and the
problem can be solved by the below-described method.
[0117]
5 The problem arises in the case where synchronization between the Macro
eNodeB and the Pico eNodeB is not perfect. For example, this is the case where
synchronization accuracy of the Pica eNodeB cannot be assured and a difference in
units of OFDM symbols occurs between the Macro eNodeB and the Pico eNodeB.
[0118]
10 Even whensynchronization is not perfect, the problem 1 may occur, that is,
interference to the PDCCH-MTC by the Pico eNodeB due to the BCH, PSS, SSS
transmitted from the Macro eNodeB may still occur. However, the problem 2 will
be discussed only in terms of the effect of the PDCCH transmitted from the Macro
eNodeB on the PDCCH-MTC of the Pico eNodeB.
15 [0119]
The positions of the PDCCH of the Macro eNodeB and the PDCCH-MTC
of the Pico eNodeB overlap depending on a direction of deviation in synchronization
between the Macro eNodeB and the Pico eNodeB, and consequently, it is
conceivable that receiving the PDCCH - MTC will be difticult for the UE terminals in
20 the Range Expansion Area of the Pico eNodeB. FIG. 5 illustrates the manner in
which the positions of the PDCCH of the Macro eNodeB and the PDCCH-MTC of
the Pico eNodeB overlap each other.
[OlZO]
This includes not only the case where synchronization accuracy of the Pico
25 eNodeB cannot be assured, but also the case where PDCCHs are shifted on purpose
(intentionally) in units of OFDM symbols in order to reduce interference between the
PDCCHs of the Macro eNodeB and the PDCCHs of the Pico eNodeB. Referring to
FIG. 5 again, the positions of the PDCCHs of the Macro eNodeB and the PDCCHs of
the Pico eNodeB are not overlapped each other, and so it is not necessary to place
30 higher priority on one PDCCH and to prohibit the another PDCCH. Tlms, it is
important to reduce the interference to the control area PDCCH-MTC of the virtual
carrier under such situations.
[0121]
Method 2-1: proposed is a method of limiting the range of UE Specific
Search Space in the PDCCH of an eNodeB as an interference source.
5 [O122]
That is, as illustrated in FIG. 6, the UE Specific Search Space in the control
area PDCCH on the Macro eNodeB side is designed to have no interference with the
PDCCH - MTC of the Pica eNodeB by allocating the control information PDCCH on
the downlink subframes in the current cell so as not to overlap with the center 72 sub
10 carrier which is used by the control area PDCCH-MTC on the Pica eNodeB side.
[0 1231
In the example illustrated in FIG. 6, the control signal itself is allocated so as
not to overlap with the center 72 sub carrier. Consequently, even with the center 72
sub carrier not excluded from the Search Space of the UE terminal side, no problem
15 arises because Blind decoding of a CCE in the center 72 sub carrier portion causes a
CRC error. Alternatively, the UE terminal may recognize that Search of the portion
should not be made for the UE Specific Search Space, and performs no decoding
operation. The latter is advantageous in that a load to the UE terminal is reduced.
[0 1241
20 The Macro eNodeB communicates with the Pica eNodeB through the X2
interface, S-GW, and MME to recognize the frequency band in which the virtual
carrier is allocated. Tile Macro eNodeB then transmits the control information
PDCCH without using the frequency band in which the control area PDCCH-MTC
of the virtual carrier is allocated by the Pica eNodeB.
25 [0125]
As a method of omitting Search or omitting decoding of the center 72 sub
carrier portion performed by the UE terminal, the hash function, which determines
the location of the UE Specific Search Space, may be configured to specify a
position so as not to overlap with the center 72 sub carrier portion. As one of the
30 method, a position may be specified after the center 72 sub carrier pottion is initially
excluded from the addresses to be specified by the hash function.
[0126]
There is also another method such as specifying a position in an area on the
left of the center 72 sub carrier portion by the hash function or setting an area on the
right to be identical with the area on the left.
5 [0127]
Method 2-2: proposed is a method of allocating the control area
PDCCH-MTC of the vitual carrier so as not to overlap with the Common Search
Space of PDCCH.
[0 1281
10 The method of limiting the range of Search Space according to Method 2-1
assumes the UE Specific Search Space as the Searchspace. However, the Common
Search Space is needed by the Macro eNodeB depending on a cell radius, and must
be allocated contiguously from the head of a CCE. The Common Search Space is
an area on which Search is made and Blind decoding is attempted to be performed by
15 all the UE terminals, and thus it is not desirable to prohibit transmission of the area.
When the Common Search Space is allocated so as not to overlap with the center 72
sub carrier as illustrated in FIG 6, a probleln arises if the Common Search Space
reaches the center 72 sub carrier.
[0129]
20 The area of the Common Search Space needs 576 sub carriers from the first
OFDM symbol in increasing order of frequency (described above). Because the
number of sub carriers is 1201 when the Macro eNodeB selects a bandwidth of 20
MHz (see Table I), contiguously allocated Common Search Space from the head of
the CCE does not reach the center 72 sub carrier as illustrated in FIG. 7, and thus the
25 Common Search Space can be used by the method 2-1. However, when a
bandwidth of 15 MHz or lower is selected, the Common Search Space cannot be
contiguously allocated from the head of the CCE without overlapping with the center
72 sub carrier.
[0130]
30 Thus, as the method 2-2, the Pica eNodeB allocates the virtual carrier out of
the range of the Cornmon Search Space according to a bandwidth to be used as
illustrated in FIG 8. According to the method 2-1, the Macro eNodeB specifies the
control area PDCCH (UE Specific Search Space) so as not to overlap with the sub
carrier used by the control area PDCCH - MTC on the Pica eNodeB side, thereby
preventing interference to the PDCCH-MTC of the Pica eNodeB.
5 [0131]
The Pica eNodeB communicates with the Macro eNodeB through the X2
interface, S-GW, and MME to acquire the information of a band which carries the
Common Search Space on the Macro eNodeB side. The Pica eNodeB then
transmits the control area PDCCH-MTC of the virtual carrier, the control area
10 PDCCH-MTC not overlapping with the band of the Common Search Space.
[0132]
FIG. 12 schematically illustrates a configuration example of a radio
communication device 1200 which serves as a Macro eNodeB that achieves the
above-described methods 2-1,2-2.
15 [0133]
The radio communication device 1200 includes an FW communication
processing unit 1201 to perform an analog processing on a radio signal which is
transmitted/received via an antenna, and a digital communication processing unit
1202 to perform lnodulation processing on a digital transmission signal and
20 demodulation processing on a digital reception signal. The digital communication
processing unit 1202 exchanges transmission/reception data with an upper layer
protocol of a communication layer of the radio communication device 1200. In
addition, the digital communication processing unit 1202 communicates with another
eNodeB through the X2 interface, S-GW, and MME.
25 [0134]
A Macro eNodeB subframe number identification unit 1207 identifies the
subframe number of a Macro eNodeB. A Pica eNodeB sub frame number
identification unit 1208 identifies the subframe number of a Pica eNodeB. An
offset information acquisition unit 1209 identifies an amount of deviation between
30 the suhframes of the Macro eNodeB and the Pica eNodeB in units of OFDM
symbols. An interference control unit 1206 identifies the frequency band which
includes the control area PDCCH-MTC of the virtual carrier transmitted by the
Picoe NodeB.
[0135]
A hash function management unit 1205 determines a hash function to be
5 used in each subframe according to a position identified by the interference control
unit 1206, the position causing interference to the PDCCH-MTC. A Search Space
determination unit 1204 determines the location of the UE Specific Search Space of
each UE terminal associated with the current cell using a hash function stored in the
hash function management unit 1205 in consideration of an interference-causing
10 subframe identified by the interference control unit 1206. Specifically, the Search
Space determination unit specifies the UE Specific Search Space of the control area
PDCCH on the Macro eNodeB side so as not to overlap with the band used by the
control area PDCCH-MTC on the Pico eNodeB side, and specifies the UE Specific
Search Space of the control area PDCCH on the Macro eNodeB side so as not to
15 overlap with the center 72 sub carrier used by the control area PDCCH - MTC on the
Pica eNodeB side. A CCE insertion control unit 1203 controls the insertion of each
CCE to the PDCCH based on the determined Specific Search Space.
[0136]
FIG. 13 schematically illustrates a configuration example of radio
20 communication device 1300 which serves as a UE terminal belonging to the Macro
eNodeB illustrated in FIG 12.
[0137]
The radio comtnunication device 1300 includes an RF communication
processing unit 1301 to perform an analog processing on a radio signal which is
25 transmittedlreceived via an antenna, and a digital communication processing unit
1302 to perform modulation processing on a digital transmission signal and
demodulation processing on a digital reception signal. The digital communication
processing unit 1302 exchanges transmission/reception data with an upper layer
protocol of a communication layer of the radio comnlunication device 1300.
30 [0138]
A hash function management unit 1305 determines a hash function to be
used in each subframe. A Search Space determination unit 1304 determines the
location of the Search Space. In addition, the Search Space determination unit 1304
determines the location of the UE Specific Search Space of the current terminal using
a hash function stored in the hash function management unit 1305. A Blind
5 decoding unit 2003 performs Blind decoding on the PDCCH of the Macro eNodeB
based on the determined UE Specific Search Space.
[0139]
In order to perform a virtual carrier operation having a band restricted to a
part of the donor band of 20 MHz, a UE terminal (MTC terminal), which is
10 associated with an eNodeB that transmits a virtual carrier, needs a mechanism for
recognizing the location of the virtual carrier. The operational procedure for an
MTC terminal to be able to receive the virtual carrier from the eNodeB will be
described below. .
[0140]
15 Step 1: the MTC terminal selects a corresponding eNodeB. The MTC
terminal performs synchronous processing on the target eNodeB. The synchronous
processing is performed using the (above-described) PSS, SSS which have been
inserted in specific subframes. The MTC terminal receives a reference signal such
as a Cell Specific Reference signal from the synchronized eNodeB, and acquires a
20 value corresponding to a reference signal received power RSRP. Basically, an
eNodeB having the highest RSRP is selected for connection. The MTC terminal,
however, makes comparison behveen eNodeBs with an offset of 10 to 15 dB added
to the RSRP of each Pica eNodeB, so that connection to a Pica eNodeB is likely to
occur. The MTC terminal is manufactured so as to receive a signal in a narrow
25 band only. Because the PSS, SSS of eNodeB are allocated at the center 72 sub
carrier in the donor band of 20 MHz, acquisition of RSRP is suitably performed
using a signal in the center 72 sub carrier.
[0141]
Step 2: The MTC terminal acquires the position of the virtual carrier of the
30 selected eNodeB. The MTC, after determining the eNodeB to be connected by the
above-described step 1, needs to recognize which frequency position (sub carrier) is
used for operating the virtual carrier in the eNodeB.
[0 1421
As a method, the system information transmitted by the eNodeB may be
used. The information, which has been broadcast as the system information BCH
5 from the eNodeB, includes the frequency position of the virtual carrier. The MTC
terminal, while receiving the center 72 sub carrier of the donor band in step 1,
acquires the system information to be able to recognize the frequency position of the
virtual carrier.
[0 1431
10 As another method, the MTC terminal may perform scanning operation to
identify the virtual carrier. However, the scanning operation increases the load to
the MTC terminal, thereby conflicting with a feature of MTC, that is, extremely low
power consumption (described above).
101441
15 Step 3: The MTC terminal acquires the position information in time
direction of the control area PDCCH-MTC of the virtual carrier.
[0145]
As a method, the system information transmitted by the eNodeB may be
used. The information, which has been broadcast as the system information BCH
20 from the eNodeB, includes the frequency position of the virtual cwrier. The MTC
terminal, while receiving the center 72 sub carrier of the donor band in step 1,
acquires the system information to be able to recognize the position of the virtual
carrier in time direction.
[0146]
25 As another method, the MTC terminal performs Blind decoding on the
virtual carrier to obtain desired control information, thereby acquiring the location of
the virtual carrier. The Blind decoding is used in general LTE as a method for
acquiring the CCE addressed to the MTC terminal, in a normal PDCCH. In this
method, the CCE, which indicates the head of the PDCCH-MTC, is designed to be
30 received by all the terminals. Each MTC terminal performs Blind decoding on the
virtual carrier to search for a location where CRC returns OK, and thus can recognize
the location as the head of the PDCCH-MTC.
[0 1471
The MTC terminal determines an eNodeB to be connected according to the
operational procedure of the above steps 1 to 3, obtains the position of the virtual
5 carrier, and thus acquire the position of PDCCH-MTC in the virtual carrier.
Consequently, the technology disclosed in the present description can be
implemented.
[0148]
Additionally, the technology disclosed herein may also be configured as
10 below.
(1)
A radio communication device (Pico eNodeB or Macro eNodeB) including:
an information acquisition unit configured to acquire information of a
frequency position (the center 72 sub carrier of the donor area) at which
15 predetermined indispensable information BCH, PSS, SSS is allocated in a data area
PDSCH of a downlink subframe transmitted by an adjacent base station Macro
eNodeB or Pico eNodeB; and
a virtual carrier transmission control unit configured to transmit a viltual
carrier (PDCCH - MTC, PDSCH-MTC) in a data area PDSCH of a downlink
20 subframe of a current cell in a manner that the virtual carrier does not overlap with
the frequency position at which the predetermined indispensable information BCH,
PSS, SSS is allocated, the virtual carrier having a narrower band than a donor band.
(2)
The radio communication device according to (I),
25 wherein the subframes are synchronized between the radio communication
device and the adjacent base station Macro eNodeB or Pico eNodeB.
(3)
The radio communication device according to (I),
wherein the subframes are not synchronized between the radio
30 communication device and the adjacent base station Macro eNodeB or Pico eNodeB.
(4)
Aradio communication device (Pico eNodeB or Macro eNodeB) including:
an information acquisition unit configured to acquire information of a
location at which predetermined indispensable information BCH, PSS, SSS is
allocated in a data area PDSCH of a downlink subframe transmitted by an adjacent
5 base station Macro eNodeB or Pico eNodeB; and
a virtual carrier operation unit configured to prohibit operation of a virtual
carrier (PDCCH-MTC, PDSCH-MTC) in a data area PDSCH of a downlink
subframe of a current cell, the downlink subframe overlapping with the subframe in
which the predetermined indispensable information BCH, PSS, SSS is allocated, the
10 virtual carrier having a narrower band than a donor band.
(5)
The radio communication device according to (4),
wherein the subframes are synchronized between the radio communication
device and the adjacent base station Macro eNodeB or Pico eNodeB.
15 (6)
The radio communication device according to (4),
wherein the subframes are not synchronized between the radio
communication device and the adjacent base station Macro eNodeB or Pico eNodeB.
(7)
20 - A radio communication device (Pico eNodeB or Macro eNodeB) including:
an infonnation acquisition unit configured to acquire information of a
location at which predetermined indispensable information BCH, PSS, SSS is
allocated in a data area PDSCH of a downlink subframe transmitted by an adjacent
base station Macro eNodeB or Pico eNodeB; and
25 a virtual carrier operation unit configured to prohibit transmission of control
information PDCCH-MTC of a virtual carrier in a data area PDSCH of a downlink
subframe of a current cell, the downlink subframe overlapping with the subframe in
which the predetermined indispensable information BCH, PSS, SSS is allocated, the
virtual carrier having a narrower band than a donor band.
30 (8)
The radio communication device according to (7),
wherein the subframes are synchronized between the radio communication
device and the adjacent base station Macro eNodeB or Pico eNodeB.
(9)
A radio communication device including:
5 an information acquisition unit configured to acquire information of a
frequency band in which a control area PDCCH-MTC of a virtual carrier is allocated
in a data area PDSCH of a downlink subframe by an adjacent base station Pico
eNodeB, the virtual carrier having a narrower band than a donor band; and
a subframe transmission control unit configured to transmit control
10 information of a downlink subfiame of a current cell without overlapping with the
frequency band in which the control area PDCCH-MTC of the virtual carrier is
allocated by the adjacent base station Pico eNodeB.
(10)
The radio communication device according to (9),
15 wherein the subframes are not synchronized between the radio
communication device and the adjacent base station Macro eNodeB or Pico eNodeB.
(11)
A radio communication device (Pico eNodeB) including:
an information acquisition unit configured to acquire information of a band
20 included in a downlink subfiame transmitted by an adjacent base station Macro
eNodeB, the information of the band carrying control information Common Search
Space for all terminals in the adjacent cell; and
a virtual carrier transmission control unit configured to transmit a control
area PDCCH-MTC of a virtual carrier in a data area PDSCH of a downlink subframe
25 of a current cell in a manner that the control area does not overlap with a band for
transmitting the control information Common Search Space by the adjacent base
station Macro eNodeB, the virtual carrier having a narrower band than a donor band.
(12)
The radio communication device according to (ll),
wherein the subframes are not synchronized between the radio
communication device and the adjacent base station Macro eNodeB or Pico eNodeB.
Aradio communication method includmg:
a step of acquiring information of a frequency position (the center 72 sub
carrier of the donor area) at which predetermined indispensable information BCH,
5 PSS, SSS is allocated in a data area PDSCH of a downlink subframe transmitted by
an adjacent base station Macro eNodeB or Pico eNodeB; and
a step of transmitting a virtual carrier (PDCCH-MTC, PDSCH-MTC) in a
data area PDSCH of a downlink subframe of a current cell in a manner that the
virtual carrier does not overlap with the frequency position at which the
10 predetermined indispensable information BCH, PSS, SSS is allocated, the virtual
carrier having a narrower band than a donor band.
(14)
A radio communication method including:
a step of acquiring information of a location at which predetermined
15 indispensable information BCH, PSS, SSS is allocated in a data area PDSCII of a
downlink subframe transmitted by an adjacent base station Macro eNodeB or Pico
eNodeB; and
a virtual carrier operation step of prohibiting operation of-a virtual carrier
(PDCCH-MTC, PDSCH-MTC) in a data area PDSCH of a downlink subframe of a
20 current cell, the downlink subframe overlapping with the subfiame in which the
predetermined indispensable information BCH, PSS, SSS is allocated, the virtual
carrier having a narrower band than a donor band.
(15)
Aradio communication method including:
25 a step of acquiring information of a location at which predetermined
indispensable information BCH, PSS, SSS is allocated in a data area PDSCH of a
downlink subframe transmitted by an adjacent base station Macro eNodeB or Pico
eNodeB; and
a virtual carrier operation step of prohibiting transmission of PDCCH - MTC
30 of a virtual carrier in a data area PDSCH of a downlink subframe of a current cell,
the downlink subframe overlapping with the subfiame in which the predetermined
indispensable information BCH, PSS, SSS is allocated, the virtual carrier having a
narrower band than a donor band.
(16)
A radio communication method including:
5 a step of acquiring information of a frequency band in which a control area ,
PDCCH-MTC of a virtual carrier is allocated in a data area PDSCH of a downlink
subframe by an adjacent base station Pico eNodeB, the virtual carrier having a
narrower band than a donor band; and
a step of transmitting control information of a downlink subframe of a
10 current cell without overlapping with the fiequency band in which the control area
PIICCH-MTC of the virtual carrier is allocated by the adjacent base station Pico
eNodeB.
(17)
A radio communication method including:
15 a step of acquiring information of a band included in a downlink subframe
transmitted by an adjacent base station Macro eNodeB, the information of thc band
carrying control information Common Search Space for all terminals in the adjacent
cell; and
a step of transmitting a control area of a virtual carrier in a data area PDSCH
20 of a downlink subframe of a current cell in a manner that the control area
PDCCH-MTC does not overlap with a band for transmitting the control information
Common Search Space by the adjacent base station Macro eNodeB, the vit-tual
carrier having a narrower band than a donor band.
(18)
25 A radio communication system including:
a first base station Macro eNodeB configured to allocate predetermined
indispensable information BCH, PSS, SSS at a predetermined frequency position
(the center 72 sub carrier of the donor area) of a data area PDSCH of a downlink
subfiame at a predetermined position of a current cell; and
30 a second base station Pica eNodeB configured to transmit a virtual carrier
(PDCCH-MTC, PDSCH-MTC) in the data area PDSCH of the downlink subfiatne
of the current cell in a manner that the virtual carrier does not overlap with the
frequency position at which the predetermined indispensable information BCH, PSS,
SSS is allocated, the virtual carrier having a narrower band than a donor band.
(19)
5 A radio communication system including:
a first base station Macro eNodeB configured to allocate predetermined
indispensable information BCH, PSS, SSS in a data area PDSCH of a downlink
subfiame at a predetermined position of a current cell; and
a second base station configured to prohibit operation of a virtual carrier
10 (PDCCH - MTC, PDSCH - MTC) in a data area PDSCH of a downlink subfiame of a
current cell, the downlink subfiame overlapping with the subfranle in which the
predetermined indispensable information BCH, PSS, SSS is allocated, the virtual
carrier having a narrower band than a donor band.
(20)
15 A radio communication system including:
a first base station Macro eNodeB configured to allocate predetermined
indispensable information BCH, PSS, SSS in a data area PDSCH of a downlink
subframe at a predetermined position of a current cell; and
a second base station configured to prohibit transmission of PDCCH-MTC
20 of a virtual carrier (PDCCH-MTC, PDSCH-MTC) in a data area PDSCH of a
downlink subframe of a current cell, the downlink subfiame overlapping with the
subframe in which the predetermined indispensable information BCH, PSS, SSS is
allocated, the virtual carrier having a narrower band than a donor band.
(21)
25 A radio communication system including:
a first base station Pico eNodeB configured to transmit a virtual carrier at a
predetermined frequency band of a data area PDSCH of a downlink subftame of a
current cell, the virtual carrier having a narrower band than a donor band; and
a second base station Macro eNodeB configured to transmit control
30 information of the downlink subfratne of the current cell without overlapping with
the frequency band in which the control area PDCCH-MTC of the virtual carrier is
allocated by the first base station.
(22)
A radio communication system including:
a first base station Macro eNodeB configured to transmit a subframe which
5 includes control information Common Search Space for all terminals in a current
cell; and
a second base station Pico eNodeB configured to transmit a control area
PDCCH-MTC of a vittual carrier in a data area PDSCH of a downlink subframe of
the current cell in a manner that the control area does not overlap with a band for
10 transmitting the control information Common Search Space by the first base station
Macro eNodeB, the virtual carrier having a narrower band than a donor band.
Industrial Applicability
[0 1491
15 It should be understood by those skilled in the art that various modifications,
combinations, sub-combinations and alterations may occur depending on design
requirements and other factors insofar as they are within the scope of the appended
claims or the equivalents thereof.
[0150]
20 In the present description, the embodiment, which is applied to a cellular
co~mnunications system in accordance with the LTE defined by the 3GPP, has been
mainly described. However, the gist of the technology disclosed in the present
description is not limited to this. The technology disclosed in the present
description can be similarly applied to various cellular colnmunications systems in
25 which cells with different sizes are l~ierarcbicallys tructured.
[a1511
In short, the present technology disclosed by the present specification has
been explained in a form of illustration and should not be interpreted limitedly. To
detennine the gist of the present technology disclosed in the present specification,
30 patent claims should be taken into account.
Reference Signs List
radio communication device
RF communication processing unit
digital communication processing unit
virtual carrier control unit
virtual carrier subframe position determination unit
Macro eNodeB subframe number identification unit
Pica eNodeB subframe number identification unit
radio communication device
RF communication processing unit
digital communication processing unit
virtual carrier subframe position holding unit
radio communication device
RF communication processing unit
digital communication processing unit
CCE insertion control unit
Search Space determination unit
bash function management unit
interference control unit
Macro eNodeB subframe number identification unit
Pica eNodeB subframe number identification unit
offset information acquisition unit
radio communication device
RF communication processing unit
digital communication processing unit
Blind decoding unit
Search Space determination unit
hash function management unit
CLAIMS
Claim 1
A radio communication device comprising:
an information acquisition unit configured to acquire information of a
5 frequency position at which predetermined indispensable information is allocated in
a data area of a downlink subframe transmitted by an adjacent base station; and
a virtual carrier transmission control unit configured to transmit a virtual
carrier in a data area of a downlink subframe of a current cell in a manner that the
virtual carrier does not overlap with the frequency position at which the
10 predetermined indispensable information is allocated, the virtual carrier having a
narrower band than a donor band.
Claim 2
The radio communication device according to claim 1,
15 wherein the subframes are synchronized between the radio communication
device and the adjacent base station.
Claim 3
The radio connnunication device according to claim 1,
20 wherein the subframes are not synchronized between the radio
communication device and the adjacent base station.
Claim 4
A radio communication device comprising:
25 an information acquisition unit configured to acquire information of a
location at which predetermined indispensable information is allocated in a data area
of a downlink subframe transmitted by an adjacent base station; and
a virtual carrier operation unit configured to prohibit operation of a virtual
carrier in a data area of a downlink subframe of a current cell, the downlink subframe
30 overlapping with the subfratne in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
Claim 5
The radio communication device according to claim 4,
wherein the subframes are synchronized between the radio communication
5 device and the adjacent base station.
Claim 6
The radio communication device according to claim 4,
wherein the subframes are not synchronized between the radio
10 communication device and the adjacent base station.
Claim 7
A radio communication device comprising:
an information acquisition unit configured to acquire information of a
15 location at which predetermined indispensable information is allocated in a data area
of a downlink snbframe transmitted by an adjacent base station; and
a virtual carrier operation unit configured to prohibit transmission of control
information of a virtual carrier in a data area of a downlink subframe of a current cell,
the downlink subframe overlapping with the subframe in which the predetermined
20 indispensable information is allocated, the virtual carrier having a narrower band
than a donor band.
Claim 8
The radio communication device according to claim 7,
25 wherein the subframes are synchronized between the radio communication
device and the adjacent base station.
Claim 9
A radio communication device comprising:
an information acquisition unit configured to acquire information of a
frequency band in which a control area of a virtual carrier is allocated in a data area
of a downlink subframe by an adjacent base station, the virtual carrier having a
narrower band than a donor band; and
a subframe transmission control unit configured to transmit control
information of a downlink subframe of a current cell without overlapping with the
5 frequency band in which the control area of the virtual carrier is allocated by the
adjacent base station.
Claim 10
The radio communication device according to claim 9,
10 wherein the subframes are not synchronized between the radio
communication device and the adjacent base station.
Claim 11
A radio communication device comprising:
15 an information acquisition unit configured to acquire information of a band
included in a downlink subframe transmitted by an adjacent base station, the
information of the band carrying control information for all terminals in the adjacent
cell; and
a virtual carrier transmission control unit configured to transmit a control
' 20 area of a virtual carrier in a data area of a downlink subframe of a current cell in a
manner that the control area does not overlap with a band for transmitting the control
information by the adjacent base station, the virtual carrier having a narrower band
than a donor band.
25 Claim 12
The radio comlnunication device according to claim 11,
wherein the subframes are not synchronized between the radio
communication device and the adjacent base station.
30 Claim 13
Aradio cotnmunication method comprising:
a step of acquiring information of a frequency position at which
predetermined indispensable information is allocated in a data area of a downlink
subframe transmitted by an adjacent base station; and
a step of transmitting a virtual carrier in a data area of a downlink subfratne
5 of a current cell in a manner that the virtual carrier does not overlap with the
frequency position at which the predetermined indispensable information is allocated,
the virtual carrier having a narrower band than a donor band.
Claim 14
10 Aradio communication method comprising:
a step of acquiring information of a location at which predetermined
indispensable information is allocated in a data area of a downlink subframe
transmitted by an adjacent base station; and
a virtual carrier operation step of prohibiting operation of a virtual carrier in
15 a data area of a downlink subfiame of a current cell, the downlink subframe
overlapping with the subframe in which the predetermined indispensable information
is allocated, the virtual carrier having a.narrower band than a donor band.
Claim 15
20 A radio comtnunication method comprising:
a step of acquiring information of a location at which predetermined
indispensable information is allocated in a data area of a downlink subframe
transmitted by an adjacent base station; and
a virtual carrier operation step of prohibiting transmission of a virtual carrier
25 in a data area of a downlink subframe of a current cell, the downlink subframe
overlapping with the subframe in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
Claim 16
30 A radio co~nmunicationm ethod comprising:
a step of acquiring information of a frequency band in which a control area
of a virtual carrier is allocated in a data area of a downlink subframe by an adjacent
base station, the virtual carrier having a narrower band than a donor band; and
a step of transmitting control information of a downlink subframe of a
current cell without overlapping with the frequency band in which a control area C of
5 the virtual carrier is allocated by the adjacent base station.
Claim 17
Aradio communication method comprising:
a step of acquiring information of a band included in a downlink subframe
10 transmitted by an adjacent base station, the information of the band carrying control
information for all terminals in the adjacent cell; and
a step of transmitting a control area of a virtual carrier in a data area of a
downlink subframe of a current cell in a manner that the control area does not
overlap with a band for transmitting the control information by the adjacent base
15 station, the virtual carrier having a narrower band than a donor band.
Claim 18
A radio communication system comprising:
a first base station configured to allocate predetermined indispensable
20 information at a predetermined frequency position of a data area of a downlink
subframe at a predetermined position of a current cell; and
a second base station configured to transmit a virtual carrier in the data area
of the downlink subframe of the current cell in a manner that the virtual carrier does
not overlap with the frequency position at which the predetermined indispensable
25 information is allocated, the virtual carrier having a narrower band than a donor band.
Claim 19
Aradio communication system comprising:
a fnst base station configured to allocate predetermined indispensable
30 information in a data area of a downlink subframe at a predetermined position of a
current cell; and
a second base station configured to prohibit operation of a virtual carrier in a
data area of a downlink subframe of a current cell, the downlink subframe
overlapping with the subfiame in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
5
Claim 20
A radio communication system comprising:
a first base station configured to allocate predetermined indispensable
information in a data area of a downlink subframe at a predetermined position of a
10 current cell; and
a second base station configured to prohibit transmission of a virtual carrier
in a data area of a downlink subframe of a current cell, the downlink subframe
overlapping with the subframe in which the predetermined indispensable information
is allocated, the virtual carrier having a narrower band than a donor band.
15
Claim 21
A radio communication system comprising:
a first base station configured to transmit a virtual carrier at a predetermined
frequency band of a data area of a downlink subframe of a current cell, the virtual
20 carrier having a narrower band than a donor band; and
a second base station configured to transmit control information of the
downlink subframe of the current cell without overlapping with the frequency band
in which the control area of the virtual carrier is allocated by the f ~ sbta se station.
25 Claim22
A radio communication system comprising:
a f ~ sbtas e station configured to transmit a subframe which includes control
information for all terminals in a current cell; and
a second base station configured to transmit a control area of a virtual
30 carrier in a data area of a downlink subframe of the current cell in a manner that the
control area does not overlap with a band for transmitting the control information by
the first base station, the virtual carrier having a narrower band than a donor band.