Description
Title of Invention
COMMUNICATION CONTROL DEVICE, COMMUNICATION CONTROL
5 METHOD, AND PROGRAM
Technical Field
[OOOl]
The present invention relates to a communication control device, a
10 communication control method, and a program.
Bacltground Art
[0002]
Recently, a cellular system of fourth generation (4G) has been discussed to
15 further improve the performance of wireless communication. In the 4G, relay
technology, carrier aggregation, Coordinated Multiple Point transmission and
reception (CoMP) technology, and the lilte are paid attention.
[0003]
The relay technology is technology by which a relay node relays
20 communication between a base station (for instance, a macrocell base station) and a
communication terminal, and is important in improving a cell-edge throughput of the
base station. Moreover, the carrier aggregation is technology for extending a usage
bandwidth (for instance, 20 MHz x 5 = 100 MHz) and improving a maximum
tl?roughput by co!lectively treating a plura!itjl cf frequency bands that have a
25 bandwidth of 20 MHz. Moreover, the CoMP is technology by which a plurality of
base stations called a CoMP set cooperates to perfor111 data coinmunication with a
communication terininal, and can expand the coverage that can support
cotn~nunicationa t high data rates. The CoMP is disclosed in Patent Literature 1, for
example.
30 [0004]
Moreover, in the 4G it has been discussed to i~nprove the coverage by
introducing base stations other than macro-eNodeBs, for example, by introducing
Home eNodeBs (such as femtocell base stations and micro-base stations for mobile
phones), remote radio heads (RRHs), and pico-eNodeBs.
5 Citation List
Patent Literature
[0005]
Patent Literature 1 : JP 2011-091785A
10 Summary of Invention
Technical Problem
[0006]
In this way, in a heterogeneous environment in which various ltinds of base
stations such as RRHs and macro eNodeBs are dispersed, it is anticipated that even
15 the CoMP set might dynamically change. However, methods of determining the
CoMP set in the heterogeneous environment are not sufficiently discussed.
[0007]
Accordingly, the present disclosure proposes a novel and improved
communication control device, cominunication control method, and program for
20 appropriately determining a combination of base stations used for communication
with a communication terminal.
Solution to Problem
[ooos]
2 5 According to the present disclosure, there is provided a communication
control device including a setting unit configured to set a timing at which a
predetermined signal is transmitted only from one of a plurality of base stations
having an identical cell ID, and a determining unit configured to, based on a
reception result of a con~municationd evice at the timing, determine a combination of
30 base stations from the plurality of base stations, the colnbination of the base stations
being used for transmitting a signal to the cominunication device.
[0009]
According to the present disclosure, there is provided a conlmunication
control method including setting a timing at which a predetermined signal is
transmitted only from one of a plurality of base stations having an identical cell ID,
5 and determining, based on a reception result of a communication device at the timing,
a combination of base stations from the plurality of base stations, the combination of
the base stations being used for transmitting a signal to the communication device.
[OO 101
According to the present disclosure, there is provided a program for causing
10 a computer to function as a setting unit configured to set a tinling at which a
predetermined signal is transmitted only from one of a plurality of base stations
having an identical cell ID, and a determining unit configured to, based on a
reception result of a communication device at the timing, determine a combination of
base stations fiom the plurality of base stations, the coinbination of the base stations
15 being used for transmitting a signal to the coinlnunication device.
Advantageous Effects of Invention
[OO 1 11
According to the present disclosure as described above, it is possible to
20 appropriately determine a combination of base stations used for communication with
a communication terminal.
Brief Description of Drawings
[0012j
25 [FIG. 11 FIG. 1 is an explanatory diagram illustrating a configuration of a
communication system according to an embodiment of the present disclosure.
[FIG. 21 FIG. 2 is an explanatory diagram illustrating a frame format of 4G.
[FIG. 31 FIG. 3 is an explanatory diagram illustrating an example of an embodiinent
of CoMP.
30 [FIG, 4'1 FIG. 4 is an explanatory diagram illustrating another example of the
elnbodiment of the COW.
[FIG. 51 FIG. 5 is a functional block diagram illustrating configurations of an eNodeB
and an RRH according to a first embodiment.
[FIG. 61 FIG. 6 is an explanatory diagram illustrating a subframe which is set as an
ABS.
5 [FIG. 71 FIG. 7 is an explanatory diagram illustrating subframes which are set as an
ABS and a Multimedia Broadcast n~ulticastS ingle Frequency Network (MBSFN).
[FIG. 81 FIG. 8 is an explanatory diagram illustrating an example of setting an ABS.
[FIG. 91 FIG. 9 is an explanatory diagram illustrating another example of setting an
ABS.
10 [FIG. 101 FIG. 10 is an explanatory diagram illustrating an example of setting an
ABS when base stations are grouped.
[FIG. 111 FIG. 11 is an explanatory diagram illustrating an example. of information
that is held by an RSRP holding unit.
[FIG. 121 FIG. 12 is a functional block diagram illustrating a configuration of a UE
15 according to the first embodiment.
[FIG. 131 FIG. 13 is a flowchart illustrating an operation of a communication system.
[FIG. 141 FIG. 14 is an explanatory diagram illustrating a modification of a method
of setting an ABS.
[FIG. 151 FIG. 15 is a functional block diagram illustrating configurations of an
20 eNodeB and an RRH according to a second embodiment of the present disclosure.
[FIG. 161 FIG. 16 is an explanatory diagram illustrating a specific example of a CSIRS
insertion period.
[FIG. 171 FIG. 17 is an explanatory diagram illustrating an example of setting the
CSI-RS iiisertion period whcn WGIs are groupzd.
25 [FIG. 181 FIG. 18 is a functional block diagram illustrating a configuration of a UE
according to the second embodiment.
[FIG. 191 FIG. 19 is a flowchart illustrating an operation of a communication system.
[FIG. 201 FIG. 20 is an explanatory diagram illustrating a modification of the CSI-RS
insertion period.
30 [FIG. 211 FIG. 21 is an explanatory diagram illustrating CSI-RS + Enhanced-Muting
according to a second modification.
Description of Embodiments
[00 131
Preferred embodiments of the present disclosure are described below in
5 detail referring to the accompanying drawings. Throughout the present description
and drawings, components having substantially the same functional configuration are
denoted by the same reference letters or numbers and thus a redundant description
about such coinponents will not be made.
[0014]
10 Moreover, a plurality of components having substantially the same
functional configuration may be distinguished sometimes by different alphabets
added to the last part of the same reference letters in the present description and the
drawings. For instance, a plurality of components having substantially the same
functional configuration may be distinguished like RRHs 30A, 30B, and 30C if
15 necessary. However, when a plurality of co~nponentsh aving substantially the same
functional configuration need not necessarily be distinguished from each other, such
components may be denoted only by the same reference letter. For instance, when
RRHs 30A, 30B, and 30C need not be necessarily distinguished from each other,
they are only referred to as RRHs 30.
20 [0015]
Moreover, the present disclosure will be described in the following order of
items.
1. Overall configuration of coiv~inunication system
2. First erxbodiixen:
2 5 2-1. Configuration of base station
2-2. Configuration of UE
2-3. Operation of com~nunications ystem
2-4. Modification
3. Second embodiment
3 0 3- 1. Regarding CSI-RS
3-2. Configuration of base station
3-3. Configuration of UE
3-4. Operation of communication system
3-5. First modification
3-6. Second modification
5 4. Conclusion
[00 1 61

The technology according to the present disclosure may be executed in
various modes as described in detail, for example, in sections from "2. First
10 embodiment" to "3. Second embodiment". A communication control device
(eNodeB 10) according to each embodiment includes
A. a setting unit (ABS setting holding unit 160, CSI-RS period setting holding unit
162) configured to set a timing at which a predetermined signal is transmitted only
from one of a plurality of base stations having an identical cell ID, and
15 13. a determining unit (CoMP set determining unit 182) configured to, based on a
reception result of a communication device at the timing, determine a combination of
base stations from the plurality of base stations, the combination of the base stations
being used for transmitting a signal to the coininunication device.
[0017]
20 Hereinbelow, first, a basic configuration that is coininon in each
embodiment will be described with reference to FIGS. 1 and 2.
[0018]
(Overall configuration of communication systein)
FIG. 1 is aii explanatory diagram illustiating a configuration of a
25 con~munications ystem 1 according to an embodiment of the present disclosure. As
illustrated in FIG. 1, the coinmunication systein 1 according to the embodiment of the
present disclosure includes an eNodeB 10, a core network 12, a user equipment (UE)
20, and a plurality of RRHs 30A to 30F.
[00 191
3 0 The UE 20 is a coininunication device that performs reception processing
for a down-link resource block that is allocated by a base station such as the eNodeB
10, and performs transmission processing for an up-link resource block.
[0020]
The UE 20 may be a smartphone shown in FIG. 1 for instance, or may be an
information processing device such as a personal computer (PC), a home-use video
processing device (DVD recorder, VCR, and the like), a personal digital assistants
(PDA), a family-use game console, or a home electric appliance. In addition, the
UE 20 may be a mobile cominunication device such as a mobile phone, a personal
handyphone system (PHs), a portable music player, a portable video processing
device, and a portable game console.
[0021]
The eNodeB 10 is a radio base station that coinmunicates with the UE 20 in
the coverage (in the present description, the eNodeB 10 indicates a Macro-eNodeB
unless specifically described otherwise). Moreover, the eNodeB 10 is connected to
a plurality of RRHs 30A to 30F through a coininunication path such as an optical
fiber for instance. Therefore, the eNodeB 10 can transmit a down-link signal to the
RRH 30 through the comnlunication path and cause the RRH 30 to transmit the
down-link signal to the UE 20, or can receive an up-link signal, which the RRH 30
has received from the UE 20, from the RRH 30. In addition, it is also possible for
the eNodeB 10 to perforin CoMP communication by cooperating with the plurality of
RRHs 30A to 30F. Details of the COW communication will be described later.
Although not illustrated in FIG. 1, a lot of the eNodeBs 10 are actually connected to a
core network 12.
[0022]
The core netvvoi-k is a service-provider's iietwoi-k iiiciildii~g inanageineni
nodes such as a mobility management entity (MME) and a serving gateway (GW).
The MME is a device that sets a session for data communication, and controls
opening and hand-over. This MME is connected to the eNodeB 10 through an
interface called X2. The S-GW is a device that routes and forwards user data.
COO231
The RRH 30 is a radio base station which coinmunicates with the UE 20
with less power than the eNodeB 10. Specifically, the RRH 30 is connected to the
eNodeB 10 through a cominunication path such as an optical fiber, and transmits the
down-link signal, which has been received froin the eNodeB 10 through this
colnmunication path, to the UE 20. Moreover, the RRH 30 transniits the up-link
signal, which has been received from the UE 20, to the eNodeB 10 through the
communication path. The comlnunication system 1 according to the present
disclosure includes the RRHs 30 so that the coverage and the quality in the vicinity
of the cell edge can be improved.
[0024]
(Frame configuration)
Next, a radio frame shared between the UE 20 and a base station such as the
eNodeB 10 will be described.
[0025]
FIG. 2 is an explanatory diagram illustrating a frame format of 4G. As
illustrated in FIG. 2, a radio frame of 10 Ins includes ten subframes #O to #9 each of
which is 1 111s. Each subfranle is one resource block including twelve subcarriers x
fourteen orthogonal frequency division multiplexing (OFDM) symbols, and
scheduling is assigned in units of a resource block. Moreover, a single OFDM
symbol corresponds to a unit used in a comn~unication system of an OFDM
modulation system, and is the unit for outputting data which is processed through
one time of fast Fourier transform (FFT).
[0026]
Moreover, as illustrated in FIG. 2, each subframe includes a control region
and a data region. The control region includes first one to three OFDM sylllbols
(FIG 2 S ~ ~ O WaSn ~xaiilplsi il which the coiltrol ~egioili iichdes three OFDM
symbols) and is used to transmit a control signal that is called phy downlink control
channel (PDCCH). Further, the data region following the control region is used to
transinit user data or the like that is called phy downlink shared channel (PDSCH).
[0027]
In addition, a cell-specific common reference signal (CRS) that is a cellspecific
reference signal is disposed in the control region and the data region. The
UE 20 performs channel estimation by receiving this CRS, and can demodulate the
PDSCH and the like on the basis of the channel estimation result.
[0028]
(Regarding C o w )
Next, the CoMP that relates to the present disclosure will be described.
5 The CoMP is technology by which a plurality of base stations called a CoMP set
cooperate to perform data communication with the UE 20, and can extend the
coverage which can support communicatio~a~t high data rates. This CoMP is
divided roughly into Joint Processing and Coordinated Scheduling andlor
Beamforming.
10 [0029]
The former, Joint Processing, is technology by which a plurality of base
stations perform data communication with one UE 20 at the same time. For
instance, as illustrated in FIG. 3, an example in which the eNodeB 10 and the RRHs
30A to 30F transmit data to the UE 20 at the same time comes under the Joint
15 Processing. According to this Joint Processing, since branches (antennas and
analog circuits (wireless processing units)) of a plurality of base stations can be used
for data communication, the antenna gain and SINR can be improved.
[0030]
When Joint Processing for down-link is performed, transmission data to the
20 UE 20 should be distributed to the RRHs 30A to 30F through a wired communication
path, for example, called a backing hole between the base stations beforehand.
Moreover, the Joint Processing for up-link is performed by integrating the data
received by a plurality of base stations from the UE 20.
i003 11
25 Examples of the data integration inethod include a inethod of integrating
data of a bit level which has been deinodulated by each of the base stations, a method
of integrating data of a soft bit level which has not yet been decoded by each of the
base stations, a method of integrating data which has not yet been demapped by each
of the base stations, and the like. As the data is integrated after latter part of the
30 data is demodulated in each base station, the amount of data which is exchanged
through the backing hall increases, b~ltth e performance tends to improve.
[0032]
The latter, the Coordinated Scheduling and/or Beamforming, is technology
by which data transmission is performed only by one base station and scheduling
(control for detennining resource blocks to be allocated to respective UEs 20) is
5 performed cooperatively by the plurality of base stations. According to this
Coordinated Scheduling and/or Beamforming, interference among the plurality of
base stations can be easily avoided by performing scheduling adjustment.
[0033]
The technology according to the present disclosure especially focuses on the
10 former, that is, Joint Processing, among the two kinds of CoMPs. This Joint
Processing is roughly classified into Non-Coherent Joint Processing and Coherent
Joint Processing.
[0034]
The Coherent Joint Processing is an adjustment inethod of adjusting timing
15 of data transmission fro~n each of the base stations so that phases of data, which
arrives at a communication terminal 20 from the respective base stations, match. To
the contrary, the Non-Coherent Joint Processing is a inethod in which each of the
base stations transmits data without adjusting timing of data transmission from each
of the base stations. Therefore, the Coherent Joint Processing is superior in
20 performance to the Non-Coherent Joint Processing. However, in order to perform
the Coherent Joint Processing, it is necessary to calculate an adjustment amount of
transmission timing of each of the base stations 10 for every cominunication terminal
20. Accordingly, it is disadvantageous in terms of complex processing.
iGG35j
2 5 (Regarding CoMP set)
The CoMP set is a term used in 3GPP, and it means a combination of base
stations which cooperatively perforin transn~ission for the purpose of performing the
CoMP. Usually, it is assumed that about three eNodeBs 10 compose the CoMP set.
Meanwhile, three or more base stations, such as five and ten, compose the C o w set
30 in an heterogeneous environment in which cells such as Pico-eNodeBs,
Home - eNodeBs, and RRH-eNodeBs (in the present description, simply called
RRHs) are overlaid. Moreover, it is anticipated that the CoMP set dynamically
changes.
[0036]
By the way, since the distances to the respective base stations are different
5 depending on the UEs 20, the best CoMP set is different for each of the UEs 20.
Therefore, it is important to determine the best CoMP set for each of the UEs 20.
For instance, the CoMP set can be determined in such a manner that the base stations
receive the reports of reference signal received power (RSRP) of CRS that each of
the UEs 20 has acquired in a frame-synchronized manner with each of the base
10 stations and the base stations where the RSRP is large are selected from among the
plurality of base stations that are reported from the UEs 20.
[0037]
(Relation between cell ID and CoMP)
The above-mentioned Macro-eNodeBs 10 usually have cell IDS which are
15 different for cach of the Macro-eNodeBs 10. Similarly, it has been assumed for the
RRHs 30 to have cell IDS different for each of the RRHs 30. However, recently, a
scenario has been discussed in which the plurality of RRHs 30 that belongs to a
certain Macro-eNodeB 10 shares the same cell ID with the Macro - eNodeB 10. In
this case, since the Macro - eNodeB 10 and the plurality of RRHs 30 transmit the
20 same signal, there are advantages that an intercell interference of the RRHs 30 does
not occur and it is easy to execute the CoMP while there is also a disadvantage that
the cell gain is not improved.
[003 81
(Point of present enibodiinent)
25 Since the cell ID and the reference signal such as the CRS are in one-to-one
correspondence when the eNodeB 10 and all of the RRHs 30 have the same cell ID
as described above, it is considered that the CRSs that are transmitted by the eNodeB
10 and each of the RRFFs 30 are identical. Therefore, even if the UE 20 attempts to
measure and report the RSSP of the CRS transmitted from each of the RRHs 30, it is
30 difficult to distinguish the sending station of the CRS. Therefore, it is also difficult
for the eNodeB 10 to select the best CoMP set for the UE 20. As a result, as
illustrated in FIG. 3, it is considered that the eNodeB 10 and all of the RRHs 30
perform the CoMP with respect to the UE 20.
[0039]
FIG. 3 is an explanatory diagram illustrating an example of the embodiment
5 of the CoMP. When the eNodeB 10 and all of the RRHs 30 perform the CoMP with
respect to the UE 20 as illustrated in FIG. 3, the UE 20 iinproves the reception
quality by receiving the same signal from the eNodeB 10 and all of the RRHs 30.
[0040]
However, when it is discussed in detail, the signal transmissions from the
10 RRHs 30D and 30E do not really contribute to the improvement of the reception
quality of the UE 20 because the reception power from the RRHs 30D and 30E that
are far from the UE 20 is low. The signal transmissions froin the RRHs 30D and
30E act as an interference wave and thus is considered to cause degradation of the
throughput of the entire system.
15 [0041]
Therefore, ideally as illustrated in FIG. 4, it is preferable that the CoMP be
performed by using only a part of the RRHs 30 (for instance, RRHs 30A and 30B)
that contributes to the improvement of the reception quality of the UE 20. However,
there has been no means for selecting the best CoMP set for the UE 20 as described
20 above. In this respect, since the conventional UEs of Rel8, Re19, and Re110 expect
the same signal to be transmitted from each of the RRHs, if the respective RRHs 30
transmit signals by which the respective RRHs can be distinguished while the
respective RRHs 30 have the same cell ID, the compatibility may be lost.
i0042j
2 5 Therefore, in view of the above-mentioned circun~stances,e ach embodiment
of the present disclosure has been made. According to each embodiment of the
present disclosure, the best CoMP set for the UE 20 can be determined by obtaining
the RSRP of each of the RRHs 30 in the UE 20. Hereinbelow, each embodiment of
the present disclosure will be described in detail as follows.
30 [0043]
<2. First embodiment>
(2-1. Configuration of base station)
FIG. 5 is a functional block diagram illustrating configurations of an
eNodeB 10-1 and RRHs 30 according to a first embodiment. As illustrated in FIG.
5, each of the RRHs 30 includes an antenna group 304 and a wireless processing unit
5 310, and transmits a down-link signal, supplied from the eNodeB 10-1 through an
optical fiber, to a UE 20-1 according to the first embodiment. Moreover, each of
the RRHs 30 supplies an up-link signal received from the UE 20-1 to the eNodeB 10-
1 through the optical fiber. Each of the RRHs 30 has the same cell ID as the
eNodeB 10-1, and transmits the same cell-specific reference signal (for instance,
10 CRS).
[0044]
Moreover, as illustrated in FIG. 5, the eNodeB 10-1 includes an antenna
group 104, a wireless processing unit 1 10, a DAIAD converter 120, an up-link (UL)
signal detector 130, a scheduler 140, a down-link (DL) signal generator 150, an ABS
15 setting holding unit 160, an RSRP holding unit 170, and a CoMP set determining unit
180. Almost blank subfraille (ABS) is technology that is decided to be adopted in
Re110 of 3GPP, and the ABS is a subfiame most of which is stopped from being
transmitted. For instance, only PDCCH and CRS are transmitted. in a subframe
which is set as the ABS. The first embodiment is made by paying attention to the
20 ABS.
[0045]
The antenna group 104 receives a radio signal from the UE 20-1, acquires
an electric high frequency signal, and supplies the high frequency signal to the
wireless precessing unit 11 0. Morecver, the antenna group 104 transmits the radio
25 signal to the UE 20-1 on the basis of the high frequency signal supplied from the
wireless processing unit 1 10. Since the eNodeB 10-1 includes the antenna group
104 including a plurality of antennas in this way, the eNodeB 10-1 can perform
MIMO coinmunication and diversity communication.
100461
3 0 The wireless processing unit 110 converts a high frequency signal supplied
from the antenna group 104 into a baseband signal (up-link signal) by performing
analog processing such as amplification, filtering, and down conversion. Moreover,
the wireless processing unit 110 converts the baseband signal (down-link signal)
supplied from the DAIAD convei-ter 120 into the high frequency signal.
[0047]
5 The DAIAD converter 120 converts the up-link signal of an analog for~nat
supplied from the wireless processing unit 110 into a digital format, and supplies the
converted signal to the UL signal detector 130. Moreover, the DAIAD converter
120 converts the down-link signal of the digital format supplied from the DL signal
generator 150 into the analog format, and supplies the converted signal to the
10 wireless processing unit 110.
[0048]
Moreover, the down-link signals for the respective RRHs 30 are supplied to
the DAIAD converter 120 from the DL signal generator 150. Therefore, the
DAIAD converter 120 converts the down-link signal for each of these RRHs 30 into
15 the analog format, and supplies the converted signal to the corresponding RRH 30
through the optical fiber. Similarly, the DAIAD converter 120 is supplied with the
up-link signal from each of the RRHs 30 through the optical fiber, converts the uplink
signal into the digital format, and supplies the converted signal to the UL signal
detector 130.
20 [0049]
The UL signal detector 130 detects a control signal such as PUCCH or user
data such as PUSCH from the up-link signal supplied from the DAIAD converter 120.
In particular, the UL signal detector 130 according to the present embodiment detects
an RSRP measurement result obtained through CRS measurement in the TE. 20 1
25 from the up-link signal supplied from the DAIAD converter 120. The RSRP
measurement result inay be included in the PUSCH.
[0050]
The scheduler 140 schedules resources to be used by the eNodeB 10-1, each
of the RRHs 30, and the UE 20-1 for communication. In particular, the scheduler
30 140 according to the present embodiment perforlns scheduling on the basis of the
base station (the eNodeB 10-1 or each of the RRHs 30) where the ABS is set by the
ABS setting holding unit 160 and a position of the subframe. Moreover, the
scheduler 140 schedules the communication with the UE 20-1 by using the CoMP set
for the UE 20-1 which is determined by the CoMP set determining unit 180.
[005 11
5 The DL signal generator 150 generates the down-link signal to be
transmitted from the eNodeB 10-1 and each of the RRHs 30. Specifically, the DL
signal generator 150 generates PDCCH, PDSCH, and the like according to the
scheduling by the scheduler 140. In addition, the DL signal generator 150
according to the present embodiment sets the position of the subframe, which is
10 specified by the ABS setting holding unit 160 as the ABS, in the ABS for the
eNodeB 10-1 and each of the RRHs 30. Moreover, the PDCCH or PDSCH may
contain infonnation on the ABS which is set by the ABS setting holding unit 160.
Hereinbelow, the subframe which is set as the ABS will be described in detail with
reference to FIGS. 6 and 7.
15 [0052]
FIG. 6 is an explanatory diagram illustrating a subframe which is set as an
ABS. In the subfraine which is set as the ABS as illustrated in FIG. 6, the PDSCH
is not transmitted in a data region. To the contrary, transmission of the PDCCH and
the CRS (reference signal) is not stopped in the data region.
20 [0053]
FIG. 7 is an explanatory diagram illustrating a subframe which is set as both
an ABS and a multimedia broadcast multicast single frequency network (MBSFN).
As illustrated in FIG. 7, all transinissions except a trans~nission of a CRS can be
stopped in the c~ntrol region by setting both the ABS and the T ~ S F Nto the
25 subframe. In the present embodiment, as described in detail later, the ABS and the
MBSFN are set in the eNodeB 10-1 and each of the RRHs 30 so that the RSRPs of
the respective RRHs 30 can be obtained in the UE 20-1.
[0054]
Here, returning to the description about the configuration of the eNodeB 10-
30 1 with reference to FIG. 5, the ABS setting holding unit 160 sets the ABS (which
niay contain the Ml3SFN, and the same applies hereinbelow) with respect to at least
part of subframes of the eNodeB 10-1 and the RRHs 30A to 30F. The ABS setting
holding unit 160 holds information that indicates the subframe set as the ABS in
association with information that indicates the base station where the ABS is set.
[OOSS]
In more detail, the ABS setting holding unit 160 sets the same subframe as
the ABS in the base stations except one base station, or except two or more base
stations among the eNodeB 10-1 and the RRHs 30A to 30F. As a result, in the
subframes that are set as the ABS, only one base station or only two or more base
stations will transmit a CRS in the data region. Hereafter, setting of such an ABS is
described more specifically with reference to FIGS. 8 to 10.
[0056]
FIG. 8 is an explanatory diagram illustrating an example of setting the ABS.
When a subframe #3 of radio frames #M to #N is set as the ABS in the eNodeB 10-1
and the RRHs 30B to 30F excluding the RRH 30A as illustrated in the first row of
FIG. 8, only the RRH 30A transmits the CRS in the data region of the subfi-ame #3 of
the radio frames #M to #N as illustrated in the upper part of FIG. 9.
[0057]
Similarly, when the subframe #3 of the radio frames #N+1 to #O is set as
the ABS in the eNodeB 10-1, the RRH 30A, and the RRHs 30C to 30F excluding the
RRH 30B as illustrated in the second row of FIG. 8, only the RRH 30B transmits the
CRS in the data region of the subfi-ame #3 of the radio frames #N+1 to #O as
illustrated in the lower part of FIG. 9. By repeating such a setting, it is possible to
generate the subframes with the data region in which only each of the RRHs 30A to
;OF Gar1 iransniil ihe CRS.
[0058]
Although the example of setting the ABS excluding only one RRH 30 has
been described above, the present embodiment is not limited to the example. For
instance, the ABS setting holding unit 160 may group the eNodeB 10-1 and the
RRHs 30A to 30F into two or inore base station groups, and the ABS may be set
excluding any given base station groups. Hereafter, it will be described more
specifically with reference to FIG. 10.
[0059]
FIG. 10 is an explanatory diagram illustrating an example of setting the ABS
when base stations are grouped. As illustrated in FIG. 10, the ABS setting holding
unit 160 may group the RRHs 30A to 30F into a base station group including the
5 RRHs 30A to 30C and a base station group including the RRHs 30D to 30F. In this
case, the ABS setting holding unit 160 can cause only the base station group CI
including the RRHs 30A to 30C to transinit the CRS in the data region of the
subframe #3 by setting the subframe #3 of the radio frames #M to #N as the ABS for
the eNodeB 10-1 and the base station group including the RRHs 30D to 30F.
10 [0060]
Similarly, as illustrated in the lower part of FIG. 10, the ABS setting holding
unit 160 can cause only the base station group including the RRHs 30D to 30F to
transmit the CRS in the data region of the subframe #3 by setting the subframe #3 of
the radio frames #N+1 to #O as the ABS for the eNodeB 10-1 and the base station
15 group including the RRHs 30A to 30C. As a result, though details will be described
later, it is possible to determine the base station group where the RSRP measurement
result in the UE 20-1 is excellent as a CoMP set.
[0061]
In addition, the ABS setting holding unit 160 may set the ABS such that the
20 base station group where the RSRP measurement result in the UE 20-1 is excellent is
distinguished first and then the RSRPs of the respective RRHs 30 that compose the
corresponding base station group can be acquired. According to this configuration,
since the RRHs 30 where the RSRP in the UE 20-1 is excellent can be specified in
stages, such a ~~lifiguratioisi ie Eeciive in tenills of tlie time requii-ed aiid ef5cieilcy.
25 [0062]
Here, returning to the description about the configuration of the eNodeB 10-
1 with reference to FIG. 5, the RSRP holding unit 170 holds the RSRP measurement
results in the UE 20-1 detected by the UL signal detector 130 in association with
timings (for instance, radio frame numbers and/or subframe numbers) for
30 measurement by the UE 20-1.
[0063]
FIG. 11 is an explanatory diagram illustrating an example of inforination
that is held by the RSRP holding unit 170. When the ABS setting holding unit 160
sets the ABS, for example, as illustrated in FIG. 8, the RSRP holding unit 170 holds
information shown in FIG. 11 on the basis of the feedback from the UE 20-1.
5 Specifically, the RSRP holding unit 170 holds the radio frames #M to #N which are
set as the ABS in association with the RSRPs measured by the UE 20-1 in tlie
coriesponding radio frames such that the CRS can be transmitted from only the RRH
30A. Similarly, the RSRP holding unit 170 holds the radio frame numbers to which
the ABS is set in association with the RSRPs measured by the UE 20-1 in the
10 corresponding radio frames such that the CRS can be transmitted only from any one
of the RRHs 30.
[0064]
The CoMP set determining unit 180 determines the C o w set for
performing the CoMP with each of the UEs 20-1. Specifically, the CoMP set
15 determining unit 180 determine which RRH 30 the RSRP in each of the radio fraines
which are held by the RSRP holding unit 170 is associated with by collating the
RSRPs with the ABS setting information which is held by the ABS setting holding
unit 160. The CoMP set determining unit 180 determines a suitable CoMP set for
the UE 20-1 on the basis of the RSRP of each of the RRHs 30.
20 [0065]
For instance, the CoMP set determining unit 180 may determine a
predetermined number of the RRHs 30 from among ones where the RSRP is
excellent as the COME' set. Alternatively, the CoMP set determining unit 180 may
deteriiiine the MIs 30 where the RSW exceeds a predeteriniiied value as the CoMP
25 set. In addition, the CoMP set determining unit 180 may determine the RRHs 30
selected from ones where the RSRP is excellent in a manner that the total value of
RSRPs reaches a predetermined value as the CoMP set. The C o w set may contain
or may not contain eNodeB 10- 1.
[0066]
3 0 (2-2. Configuration of UE)
The configurations of the eNodeB 10-1 and the RRH 30 according to the
first embodiment have been described hereinabove. Next, the configuration of the
UE 20-1 according to the first embodiment will be described.
[0067]
FIG. 12 is a functional block diagram illustrating the configuration of the
5 UE 20-1 according to the first embodiment. As illustrated in FIG. 12, the UE 20-1
includes an antenna group 204, a wireless processing unit 210, a DAIAD converter
220, a DL signal detector 230, a UL signal detector 240, and an ABS setting position
holding unit 250.
[0068]
10 The antenna group 204 receives a radio signal from the eNodeB 10-1 and
the RRHs 30 to acquire an electric high frequency signal, and supplies the high
frequency signal to the wireless processing unit 210. Moreover, the antenna group
204 transmits the radio signal to the eNodeB 10-1 and the RRHs 30 on the basis of
the high frequency signal supplied from the wireless processing unit 210. The UE
15 20-1 includes the antenna group 204 including a plurality of antennas as described
above so that the UE 20-1 can perform the MIMO communication or the diversity
communication.
[0069]
The wireless processing unit 210 converts the high frequency signal
20 supplied from the antenna group 204 into a baseband signal (down-link signal) by
perfonning analog processing such as amplification, filtering, and down conversion.
Moreover, the wireless processing unit 210 converts the baseband signal (up-link
signal) supplied from the DNAD converter 220 into the high frequency signal.
Thus, the wireless processing unit 210 cooperates with the antenna group 2?4 so as
25 to function as a transmitter and a receiver.
[0070]
The DAIAD converter 220 converts the down-link signal of the analog
forinat supplied from the wireless processing unit 210 into the digital format, and
supplies the converted signal to the DL signal detector 230. Moreover, DAIAD
30 converter 220 converts the up-link signal of the digital format supplied from the UL
signal generator 240 into the analog format, and supplies the converted signal to the
wireless processing unit 2 10.
[0071]
The DL signal detector 230 detects a control signal such as PDCCH, user
data such as PDSCH, or the like from the down-link signal supplied from the DNAD
converter 220. In particular, the DL signal detector 230 according to the present
embodiment extracts information that indicates an ABS setting position from the %
PDCCH or the PDSCH. The information that indicates the ABS setting position
corresponds to a location to measure an RSRP and is held in the ABS setting position
holding unit 250. Moreover, the DL signal detector 230 functions as a measuring
unit that measures the RSRP at the ABS setting position which is held in the ABS
setting position holding unit 250. According to the present embodiment, since only
some base stations out of the eNodeB 10-1 and the RRHs 30A to 30F transmit the
CRS at the ABS setting position, the DL signal detector 230 can measure the RSRP
of only a part of the base stations.
[0072]
The UL signal generator 240 generates an up-link signal to be transmitted to
the eNodeB 10-1 and each of the RRHs 30. Specifically, the UL signal generator
240 generates a control signal such as PUCCH and a user data signal such as PUSCH.
In particular, the UL signal generator 240 according to the present embodinlent
generates the PUCCH or the PUSCH including the RSRP measurement result
obtained by the DL signal detector 230.
[0073]
(2-3. Operation of communication system) ..
Ee~eir~a'uuvteh,e configurations of the eP4odeE 10-1, the KXHs 30, hi13 the
UE 20-1 according to the first embodiment have been described. Next, the
operation of a communication systein including the eNodeB 10-1, the RRHs 30, and
the UE 20-1 will be described with reference to FIG. 13.
[0074]
FIG. 13 is a flowchart illustrating the operation of the coinmunication
system. As illustrated in FIG. 13, when the ABS setting holding unit 160 of the
eNodeB 10-1 first sets the ABS (S404), the eNodeB 10-1 notifies the UE 20-1 of
information that indicates the ABS setting position by dedicated signaling (S408).
When the information that indicates the ABS setting position is received, the UE 20-
1 transmits a reception acknowledgement to the eNodeB 10- 1 (S4 12).
[0075]
Subsequently, the eNodeB 10-1 and the RRHs 30 perfonn a regular
operation as usual until the ABS setting position arrives (5416, S420). Then, when
the ABS setting position arrives, only the RRHs 30 where the ABS is not set transmit
the CRS in the data region, but the other eNodeB 10-1 or the other RRHs 30 does not
or do not transmit the CRS in the data region (S424).
[0076]
Meanwhile, the UE 20-1 measures the RSRP at the ABS setting position on
the basis of the information notified in S408 (S428). Then, the UE 20-1 transinits
the RSRP measureinent result to the eNodeB 10- 1 (S432).
[0077]
After that, the eNodeB 10-1 dete~llliilesa suitable CoMP set for the UE 20-1
on the basis of the RSRP of each of the RRHs 30, or the RSRP of each group of the
RRHs 30 when the RSRP of each of the RRHs 30 or the RSRP of each group of the
RRHs 30 are coinpletely gathered (S436). Then, the eNodeB 10-1 and the RRHs
30 that compose the determined CoMP set perfonn the CoMP communication with
the UE 20-1 (S440). Specifically, the eNodeB 10-1 supplies the down-link signal to
the RRHs 30 that compose the determined CoMP set, and the RRHs 30 that coinpose
the CoMP set send the supplied down-link signal to the UE 20-1 in cooperation with
the eNodeB 10- 1. Further, if the eNodeB 10 1 supplies the down-link signal to the
KGIs 36 that compose the Cold? set as described above, the dowii-iink signai is
transmitted fro111 the corresponding RRHs 30 so that the CoMP con~munication can
be achieved. Accordingly, the determined C o w set is not necessarily notified to
the RRHs 30.
[0078]
As described above, according to the first einbodii~lent of the present
disclosure, the RSRP in the UE 20-1 of each of the RRHs 30 can be measured even
in the situation in which each of the RRtIs 30 transmits the same CRS. Therefore,
the eNodeB 10-1 can determine the suitable CoMP set for the UE 20-1 on the basis
of the RSRP of each of the RRHs 30 in the UE 20-1.
[0079]
(2-4. Modification)
Although the example where the ABS setting holding unit 160 sets the ABS
to different radio frames for different RRHs 30 has been described above with
reference to FIG. 9 and the lilte, the present embodiment is not limited to the example.
For instance, the ABS setting holding unit 160 may set the ABS to a plurality of
subframes within the same radio frame for different RRHs 30 as described with
reference to FIG. 14.
[OOSO]
FIG. 14 is an explanatory diagram illustrating a modification of the method
of setting the ABS. As illustrated in FIG. 14, the ABS setting holding unit 160 may
set the ABS for the base stations other than the RRH 30A in the subframes #3 of the
sanle radio frame, and set the ABS for the base stations other than the RRH 30B ill
the subfraine #4. In this case, since only the RRH 30A transmits the CRS in the
data region of the subframe #3, the UE 20-1 can measure the RSRP of the RRH 30A
in the subframe #3. Similarly, the UE 20-1 can measure the RSRP of the RRH 30B
in the subfraine #4. -
[OOSl]
In this modification, the UE 20-1 may report the RSRP measurement results
and the subfraine numbers where the RSRP is measured, in association with each
other to the eNodeB 10-1 such that the eNodeB 10-1 can distinguish which RRH 30
ihe RSW riviifiecl by ihe 'u'E 20-1 is associated with.
[0082]
Lilte this modification, when the ABS is set in different RRHs 30 with
respect to a plurality of subframes of the same radio frame, the time to acquire the
RSRPs of the respective RRHs 30 can be shortened.
[0083]
<3. Second embodiment>
Hereinabove, the first embodiment of the present disclosure has been
described. Next, a second embodiment of the present disclosure will be described.
The second embodiment acquires an RSRP of each of RRHs 30 by measuring a
reference signal that is called CSI-RS not by measuring the CRS that is described in
the first embodiment. In the following, the CSI-RS will be described first, after
5 which details of the second embodiment will be described.
[0084]
(3-1. Regarding CSI-RS)
A channel state information reference signal (CSI-RS) is a reference signal
defined by LTE Advanced (RellO). This CSI-RS is used to measure a channel
10 quality, not for the purpose of data demodulation. Therefore, the CSI-RS is thinned
out in the directions of frequency and time and inserted comparatively sparsely. For
instance, an insertion period of the CSI-RS can be set within the range of about 5 ms
to 80 ins like 10 ms. Since the setting of the CSI-RS (for instance, settings such as
adjusting the insertion period to 5 ins or to 10 ms) can be perfornled for each UE, it
15 can be said that the setting (configuration) is UE-Specific.
[0085]
Moreover, as specified in Section 36.2116.10.5.1 of RellO, a pseudorandom
sequence is used for the CSI-RS. However, an initial value of the random
sequence is different for each cell (cell ID). Therefore, since the CSI-RS is
20 originally cell-specific, the base station which is a sending station of the CSI-RS can
be distinguished by the UE.
[0086]
However, when the respective RRHs 30 have the same cell ID, the CSI-RSs
that are transmitted by the respective hn31s SC are also id~iitical. Moreovei;
25 although the insertion period of the CSI-RS can be set in units of a cell, when each of
the RRHs 30 has the same cell ID, the CSI-RS insertion periods (timings) of the
respective RRIIs 30 bkcome also identical. Therefore, it has been difficult to
distinguish the RRH 30 which is a sending station of'the CSI-RS measured by the
UE, and to determine a suitable CoMP set for the UE.
30 [0087]
The second embodiment of the present disclosure is technology that is
conceived by taking the above-mentioned circumstances into consideration.
According to the second embodiment of the present disclosure, it is possible to
distinguish the RRH 30 which is a sending station of the CSI-RS received by the UE.
The second embodiment of the present disclosure is described in detail below.
[0088]
(3-2. Configuration of base station)
FIG. 15 is a functional block diagram illustrating configurations of an
eNodeB 10-2 and RRHs 30 according to the second embodiment of the present
disclosure. As illustrated in FIG. 15, each of the RRHs 30 transmits a down-link
signal supplied from the eNodeB 10-2 through an optical fiber to a UE 20-2
according to the second einbodiment siinilarly to the first embodiment. Moreover,
each of the RRHs 30 supplies an up-link signal received from the UE 20-2 to the
eNodeB 10-2 through the optical fiber. Each of the RRHs 30 has the same cell ID
as the eNodeB 10-2, and transinits the same cell-specific reference signal (for
instance, CSI-RS).
[0089]
Moreover, as illustrated in FIG. 15, the eNodeB 10-2 according to the
second einbodiment includes an antenna group 104, a wireless processing unit 11 0, a
DAIAD converter 120, an up-link (UL) signal detector 130, a scheduler 140, and a
down-link (DL) signal generator 150, a CSI-RS period setting holding unit 162, an
RSRP holding unit 172, and a C o w set determining unit 182. Since the antenna
group 104, the wireless processing unit 110, and the DAIAD converter 120 have
been described in the first einbodiment, detailed description thereof will not be given
here.
[0090]
The UL signal detector 130 detects a control signal such as PUCCH and
user data such as PUSCH from the up-link signal supplied from *the DAIAD
converter 120. In particular, the UL signal detector 130 according to the present
einbodiment detects an RSRP measurement result obtained through a CSI-RS
measurement in the UE 20-2 from the up-link signal supplied from the DAJAD
converter 120. The RSRP measurement result may be contained in the PUSCH.
[0091]
The scheduler 140 schedules resources to be used by the eNodeB 10-2, each
of the RRHs 30, and the UE 20-2 for coinmunication. In particular, the scheduler
140 according to the present embodiment perforins scheduling according to the CSI-
5 RS insertion period set by the CSI-RS period setting holding unit 162. Moreover,
the scheduler 140 schedules the communication with the UE 20-2 by using the
CoMP set for the UE 20-2, which is determined by the CoMP set determining unit
180.
[0092]
10 The DL signal generator 150 generates the down-link signal to be
transmitted from the eNodeB 10-2 and each of the RRHs 30. Specifically, the DL
signal generator 150 generates PDCCH, PDSCH, and the like according to the
scheduling performed by the scheduler 140. In addition, the DL signal generator
150 according to the present embodiment inserts a CSI-RS into the eNodeB 10-2 and
15 each of the RRHs 30 according to the period set by the CSI-RS period setting
holding unit 162. In addition, the PDCCH or the PDSCH may contain information
about the CSI-RS insertion period set by the CSI-RS period setting holding unit 162.
[0093]
The CSI-RS period setting holding unit 162 sets the CSI-RS insertion period
20 for the eNodeB 10-2 and each of the RRHs 30. For instance, the CSI-RS period
setting holding unit 162 sets different insertion periods (insertion timings) for the
eNodeB 10-2 and each of the RRHs 30. As a result, it is possible to specify a
sending station of the CSI-RS when the UE 20-2 receives the CSI-RS at a certain
+L' iming. I-Iereaftei-, the CSI-RS iiisei-tioii period will be described mo1.e specificaiiy
25 with reference to FIG. 16.
[0094]
FIG. 16 is an explanatory diagram illustrating a specific example of the CSIRS
insertion period. As illustrated in FIG. 16, the CSI-RS period setting holding
unit 162 sets the CSI-RS insertion periods such that there may be timings at which
30 only some base stations out of the eNodeB 10-2 and each of the RRHs 30 transmit
the CSI-RS.
[0095]
For instance, the CSI-RS period setting holding unit 162 sets the CSI-RS
insertion periods named t l , t3, 15, and t7 for the eNodeB 10-2 as illustrated in FIG.
16, and sets the CSI-RS insertion periods named t2 and t4 for the RRH 30A.
Therefore, only the RRH 30A transmits the CSI-RS for t2 and t4. Similarly, the
CSI-RS period setting holding unit 162 sets the CSI-RS insertion periods named t6
and t8 for the RRH 30B. Therefore, only the RRH 30B transmits the CSI-RS for t6
and t8. Similarly, it is possible to generate timings at which only each of the RRHs
30 transmits the CSI-RS by setting CSI-RS insertion periods different from those of
the eNodeB 10-2 for each of the RRHs 30.
[0096]
The example of setting the CSI-RS insertion periods named t.1, t3, t5, and t7
only for the eNodeB 10-2 is shown in FIG. 16, but these CSI-RS insertion periods
inay be set for each of the RRHs 30. In such a case, the UEs up to Re110 receive
the CSI-RSs from the plurality of RRHs 30 for the same periods named 11, 13, t5, and
t7 and acquire channels without distinguishing sending stations of the respective
CSI-RSs. Meanwhile, the UTE 20-2 down from Relll can receive the CSI-RSs at
the tilllings at which only each of the RRHs 30 transmits by setting a plurality of
periods as the CSI-RS reception periods. That is, the method of setting the CSI-RS
according to the second embodiment can ensure compatibility with existing UEs.
[0097]
Moreover, though the example of setting different CSI-RS insertion periods
for each of the RRHs 30 has been described in the above-mentioned embodiment, the
present eiiibodiment is not limited to the exampie. For instance, the CSI-RS period
setting holding unit 162 inay group the RRHs 30A to 30F into two or inore groups,
and set the same CSI-RS insertion period for the RRHs 30 that compose the same
group. Hereinbelow, such a setting is described more specifically with reference to
FIG. 17.
[0098]
FIG. 17 is an explanatory diagram illustrating an example of setting CSI-RS
insertion periods when the RRHs 30 are grouped. As illustrated in FIG. 17, the
CSI-RS period setting holding unit 162 may group the RRHs 30A to 30F into a
group including the RRHs 30A to 30C and a group including the RRHs 30D to 30F.
In this case, the CSI-RS period setting holding unit 162 can cause only the RRHs
30A to 30C to transmit the CSI-RS for t2 and t4 by setting the CSI-RS insertion
5 periods named t2 and t4 for the group including the RRHs 30A to 30C.
[0099]
Similarly, the CSI-RS period setting holding unit 162 can cause only the
RRHs 30D to 30F to transmit the CSI-RS for t6 and t8 by setting the CSI-RS
insertion periods named t6 and t8 for the group including the RRHs 30D to 30F. As
10 a result, it is possible to detennine the group where the RSRP measurement result in
the UE 20-2 is excellent, for instance, as a CoMP set.
[O 1001
In addition, the CSI-RS period setting holding unit 162 may set the CSI-RS
insertion periods such that the group where the RSRP measurement result in the UE
15 20-2 is excellent is distinguished first and then the RSRP of each of the RRHs 30 that
composes the corresponding group can be obtained. According to this
configuration, since the RRI-Is 30 where the RSRP in the UE 20-2 is excellent can be
specified in stages, the configuration is effective in terms of the time required and
efficiency.
20 [OlOl]
Here, returning to the description about the configuration of the eNodeB 10-
2 with reference to FIG. 15, the RSRP holding unit 172 holds the RSRP measurement
results in the UE 20-2 detected by the UL signal detector 130 in association with
timings (for instance, radio frame numbers and/or subframe numbers) for
25 measurement by the UE 20-2.
[O 1 021
The CoMP set detelxlining unit 182 determines the CoMP set for
performing the CoMP with each of the UEs 20-2. Specifically, the CoMP set
determining unit 182 determines which RRH 30 the RSRP in each of the radio
30 frames held in the RSRP holding unit 172 is associated with by collating the RSRP
with setting infomn~ation of each base station held in the CSI-RS period setting
holding unit 162. The C o w set determining unit 182 determines a suitable CoMP
set for the UE 20-2 on the basis of the RSRP of each of the RRHs 30.
[0 1031
I
For instance, the CoMP set determining unit 182 may determine a
5 predetermined number of the RRHs 30 from among ones where the RSRP is
excellent as the CoMP set. Alternatively, the CoMP set determining unit 182 inay
determine the RRHs 30 where the RSRP exceeds a predetennined value as the CoMP
set. In addition, the CoMP set determining unit 182 may determine, as the CoMP
set, the RRHs 30 selected from among ones where the RSRP is excellent such that
10 the total value of the RSRPs reaches a predetermined value. The CoMP set inay
contain or may not contain eNodeB 10-2.
[0 1 041
(3-3. Configuration of UE)
Hereinabove, the configurations of the eNodeB 10-2 and the RRHs 30
15 according to the second embodiment have been described. Next, the configuration
of the UE 20-2 according to the second embodiment will be described.
[O 1051
FIG. 18 is a functional block diagram illustrating the configuration of the
UE 20-2 according to the second embodiment. As illustrated in FIG. 18, the UE 20-
20 2 includes an antenna group 204, a wireless processing unit 210, a DNAD converter
220, a DL signal detector 230, a UL signal detector 240, and a CSI-RS period
holding unit 252. Since the antenna group 204, the wireless processing unit 210,
and the DNAD converter 220 have been described in the first embodiment, a
deiaiieci desclipiiun thereof is iicjt given below.
25 [0106]
The DL signal detector 230 detects a control signal such as PDCCH and
user data such as PDSCH from a down-link signal supplied from the DAIAD
converter 220. In particular, the DL signal detector 230 according to the present
embodiment extracts information that indicates the CSI-KS insertion period from the
30 PDCCH or the PDSCH. The information that indicates the CSI-RS insertion period
corresponds to a location for RSRP illeasurement and is held in the CSI-RS period
holding unit 252. Moreover, the DL signal detector 230 measures the RSRP for the
CSI-RS insertion period held in the CSI-RS period holding unit 252. According to
the present embodiment, since only some base stations of the eNodeB 10-2 and the
RRHs 30A to 30F transmit the CSI-RSs for the CSI-RS insertion periods, the DL
5 signal detector 230 can measure the RSRPs of a part of the base stations.
[0107]
The UL signal generator 240 generates an up-link signal to be transmitted to
the eNodeB 10-2 and each of the RRHs 30. Specifically, the UL signal generator
240 generates a control signal such as PUCCH and a user data signal such as PUSCH.
10 In particular, the UL signal generator 240 according to the present embodilllent
generates the PUCCH or the PUSCH including the RSRP measurement result
obtained by the DL signal detector 230.
[O 1081
(3-4. Operation of communication system)
15 Hereinabove, the configurations of the eNodeB 10-2, the RRHs 30, and the
UE 20-2 according to the second einbodinlent have been described. Next, the
operation of a comn~unications ystem including the eNodeB 10-2, the RRHs 30, and
the UE 20-2 will be described with reference to FIG. 19.
[0 1091
20 FIG. 19 is a flowchart illustrating the operation of the communication
system. As illustrated in FIG. 19, when the CSI-RS period setting holding unit 162
of the eNodeB 10-2 first sets a CSI-RS insertion period for each of the RRHs 30
(S504), the eNodeB 10-2 notifies the UE 20-2 of information that indicates a CSI-RS
insertizn period by dedicated signaling (S508). When the informztion thct indicctes
25 the CSI-RS insertion period is received, the UE 20-2 transmits a reception
acl
As described above, according to the embodiments of the present disclosure,
the RSRP can be measured in the UE 20 of each of the RRHs 30 even in the situation
in which each of the RRHs 30 operates based on the same cell ID. Therefore, the
eNodeB 10 can determine the CoMF set that is suitable for the UE 20 on the basis of
30 the RSRP of each of the RRHs 30 in the UE 20. As a result, it is possible to achieve
improvement of a system throughput and reduction in power consumption because
the transmission from the RRHs 30 that do not really contribute to the improvement
of the reception quality of the UE 20 can be avoided.
[O 1241
Although the preferred embodiments of the present disclosure have been
5 described in detail referring to the accompanying drawings, the technical scope of the
present disclosure is not limited to the examples. It is understood that those
ordinarily skilled in the technical field of the present disclosure may certainly
conceive various alterations or modifications within the scope of the technical spirit
described in the claims, and be aware that these naturally fall within the technical
10 scope of the present disclosure.
[O 12.51
For instance, although the examples of determining the C o w set on the
basis of the measurement result of the RSRP as a reference signal which is measured
by the UE 20 have been described above, the technical scope of the present
15 disclosure is not limited to the examples. As a modification, the UE 20 may
feedback an index that indicates a reception quality such as an error occurrence rate
of a signal sent from each of the RRHs 30 to the eNodeB 10, and the eNodeB 10 may
determine the CoMP set on the basis of the index.
[0 1 261
20 Furthermore, the second modification of the second embodiment has been
described by using an example in which the RSRPs corresponding to the respective
con~binations of the RRHs 30 are acquired by using the CSI-RS Muting, but the
signals used are not limited to the CSI-RS. For example, a mechanism similar to
the &hove-described il~echar~isciaii~i be provided by preparing an RRS other than the
25 CSI-RS (or a new RS). Especially when a plurality of RRHs 30 (or a plurality of
eNodeBs 10) send the RS using the same resource element, the RSRPs
corresponding to the respective combinations can be obtained using the same
mechanism as the present technology.
[O 1271
30 Furtherinore, though the CoMP set is determined by using an estimation of a
desired signal and an estimation of an interference signal, the method of acquiring
these estimations has not yet been sufficiently studied. Moreover, the estimation of
the interference amount in CoMP environment can be used for the determination of
the CoMP set, and can also be used as information for controlling other interferences,
such as ICIC (Inter-Cell Interference Coordination) of the LTE Release 8.
5 Accordingly, the estimation of the interference amount froin each eNodeB also
becomes important.
[0 1 281
That is, the technology of the present disclosure is used not only for the
purpose of acquiring a desired RSRP, but also for the purpose of acquiring an
10 intensity of an interference component. That is, according to the technology of the
present disclosure, the interference component from the base stations such as the
RRHs 30 and the eNodeBs 10 that have the same cell ID can be acquired for each of
different con~binationso f the base stations. This is implemented, for example, in a
way that the UL signal detector 130 of the eNodeB 10 acquires a detection result of
15 the interference component which is obtained from the uplink signal through RS
measurement in the UE 20, and the RSRP holding unit 170 stores the detection result
of the interference component. A specific inethod of acquiring the interference
component in each of the UEs 20 is as follows: for example, a correlation with a
reception signal is obtained by using an RS (Reference Signal) of each of the
20 eNodeBs 10 as a Icnown signal, and the interference amount of each eNodeB 10 can
be acquired by using the magnitude of the correlation. It can be said that the
inethod of acquiring the magnitude of this interference component and the method of
acquiring the magnitude of the desired component among the reception signals are
the same.
25 [0129]
Moreover, each step in the processing performed by the eNodeB 10 and the
UE 20 of the present description is not necessarily processed in a time series manner
along the order described in the sequence diagram. For instance, each step in the
processing of the eNodeB 10 and the UE 20 may be processed in order different from
30 the order described in the sequence diagram or may be processed in parallel.
[0130]
Moreover, it is possible to produce a computer program which causes
hardware built in the eNodeB 10 and the UE 20, such as a CPU, ROM, and RAM to
perform the same functions as those of the respective components of the eNodeB 10
and the UE 20 that have been described above. Moreover, a storage medium having
5 the computer program stored therein is provided.
[0131]
Additionally, the present technology may also be configured as below.
(1)
A communication control device including:
10 a setting unit configured to set a timing at which a predetermined signal is
transmitted only from one of a plurality of base stations having an identical cell ID;
and
a determining unit configured to, based on a reception result of a
communication device at the timing, determine a combination of base stations from
15 the plurality of base stations, the combination of the base stations being used for
transmitting a signal to the con~municationd evice.
(2)
The coinmunication control device according to (I),
wherein the setting unit sets a tiining at which the predetermined signal is
20 transmitted only from each of two or more base station groups, for each of the base
station groups that compose the plurality of base stations, and
wherein the determining unit detennines a base station that is used for
transi~litting a signal to the communication device, based on the reception result of
the cnrnrnunication device at the timi~gse t for each zf the twc cr more base station
25 groups.
(3
The comi~~unicatioconn trol device according to (2),
wherein the setting unit selects at least any one of the base station groups
based on the reception result of the con~munication device at the tiining set for each
30 of the two or more base station groups, and sets a timing at which a predetermined
signal is transmitted only from one, or two or more base stations that compose the
selected base station group.
(4)
The coininunication control device according to any one of (1) to (3),
wherein the timing corresponds to a subframe that composes a radio frame,
5 and
wherein the setting unit sets the subfraine as an almost blank subframe
(ABS), the subframe corresponding to the timing of a base station that is not included
in a base station group for which transinission is set at the timing.
(5)
The coinmunication control device according to (4),
wherein the setting unit further sets the subfraine as an MBSFN subframe,
the subframe corresponding to the timing of the base station that is not included in
the base station group for which the transinission is set at the timing.
(6)
15 The colnmunication control device according to any one of (1) to (5),
wherein the predetermined signal is a reference signal in a. data region in
which a physical down link shared channel (PDSCH) is transmitted.
(7)
The conlmunication control device according to (2) or (3),
wherein the setting unit sets different radio frames as the timing, the
different radio frames being used for transinitting the predetermined signal to each of
the two or inore base station groups.
(8)
Thc coixi~~riicatioconn trol dcvicc according to (71,
2 5 wherein the predetermined signal is a channel state information reference
signal (CSI-RS).
(9)
The coinlnunication control device according to (8),
wherein the setting unit stops CSI-RS transmission at the timing of a base
30 station that is not included in a base station group for which transmission is set at the
timing.
(10)
The communication control device according to any one of (1) to (9),
wherein the plurality of base stations include a base station of a remote radio
hed (RRH).
5 (11)
The conlmunication control device according to (lo),
wherein the communication control device is a lnacrocell base station, and
wherein the macrocell base station supplies a signal that is transmitted to the
communication device to the RRH that composes the combination of the base
10 stations determined by the determining unit.
(12)
The communication control device according to any one of (1) to (ll),
wherein at least any one of the plurality of base stations notifies the
communication device of information indicating the timing beforehand.
15 (13)
A communication control method including:
setting a timing at which a predetermined signal is transmitted only from
one of a plurality of base stations having an identical cell ID; and
determining, based on a reception result of a communication device at the
20 timing, a combination of base stations from the plurality of base stations, the
combination of the base stations being used for transmitting a signal to the
communication device.
(14)
A prograin f ~cra~ singa comp~tztro fiiiicti~na s:
25 a setting unit configured to set a timing at which a predetermined signal is
transmitted only from one of a plurality of base stations having an identical cell ID;
and
a determining unit configured to, based on a reception result of a
communication device at the timing, determine a combination of base stations from
30 the plurality of base stations, the combination of the base stations being used for
transmitting a signal to the communication device.
(15)
A communication control device including:
a setting unit configured to set a timing at which a predetermined signal is
transmitted only from one of a plurality of base stations having an identical cell ID;
5 and
an acquisition unit configured to acquire a detection result obtained by a
con~inunicationd evice detecting an interference component at the timing.
Reference Signs List
10 [0132]
10, 10-1, 10-2 eNodeB
12 core network
20, 20-1,20-2 UE
3 0 RRH
15 104,204, 304 antenna group
11 0, 2 10, 3 10 wireless processing unit
120, 220DAlAD converter
130 UL signal detector
140 scheduler
20 150 DL signal generator
160 ABS setting holding unit
162 CSI-RS period setting holding unit
170, 172RSRP holding unit
180, ! 82CoMP set determining unit
25 230 DL signal detector
240 UL signal generator
250 ABS setting position holding unit
252 CSI-RS period holding unit

CLAIMS
Claim 1
A communication control device comprising:
a setting unit configured to set a timing at which a predetermined signal is
5 transmitted only from one of a plurality of base stations having an identical cell ID;
and -
a determining unit configured to, based on a reception result of a
conlmunication device at the timing, determine a combination of base stations from
the plurality of base stations, the combination of the base stations -being used for
10 transmitting a signal to the communication device.
Claim 2
The coininunication control device according to claim 1,
wherein the setting unit sets a timing at which the predetermined signal is
15 transmitted only from each of two or more base station groups, for each of the base
station groups that conlpose the plurality of base stations, and
wherein the determining unit deternlines a base station that is used for
transmitting a signal to the coinmunication device, based on the reception result of
the conlmunication device at the timing set for each of the two or more base station
20 groups.
Claim 3
The coinmunication control device according to claim 2,
iiihei-eiii the settiiig uiiii selects at least ally one ol' the base siaiion groups
25 based on the reception result of the coinmunication device at the timing set for each
of the two or more base station groups, and sets a timing at which a predetermined
signal is transmitted only from one, or two or more base stations that compose the
selected base station group.
30 Claim 4
The coinmunication control device according to claim 1,
wherein the timing corresponds to a subframe that composes a radio frame,
and
wherein the setting unit sets the subframe as an almost blank subframe
(ABS), the subframe corresponding to the timing of a base station that is not included r
in a base station group for which transmission is set at the timing.
Claim 5
The communication control device according to claim 4,
wherein the setting unit further sets the subframe as an MBSFN subframe,
the subframe corresponding to the timing of the base station that is not included in
the base station group for which the transmission is set at the timing.
Claiin 6
The coininunication control device according to claim 1,
wherein the predetermined signal is a reference signal in a data region in
which a physical down link shared channel (PDSCH) is transmitted.
Claim 7
The communication control device according to claiin 2,
wherein the setting unit sets different radio frames as the timing, the
different radio frames being used for transmitting the predetermined signal to each of
the two or more base station groups:
Ckiiiii s
The coinmunication control device according to claiiil 7,
wherein the predetermined signal is a channel state information reference
signal (CSI-RS).
Claim 9
The communication control device according to claim 8,
wherein the setting unit stops CSI-RS transmission at the timing of a base *
station that is not included in a base station group for which transmission is set at the
timing. .I
Claim 10
5 The communication control device according to claim 1,
wherein the plurality of base stations include a base station of a remote radio
hed (RRH) .
Claim 11
10 The communication control device according to claim 10,
wherein the communication control device is a inacrocell base station, and
wherein the macrocell base station supplies a signal that is transmitted to the
communication device to the RRH that composes the combination of the base
stations determined by the determining unit.
15
Claim 12
The coinmunication control device according to claim 1,
wherein at least any one of the plurality of base stations notifies the
communication device of inforination indicating the timing beforehand.
20
Claim 13
A communication control method comprising:
setting a timing at which a predetermined signal is transmitted only from
Gile of a pliiraliiy of base ~ i ~ i ihoan~~iii ga ii ideiliical cell ID; aid
2 5 determining, based on a reception result of a communication device at the
timing, a combination of base stations from the plurality of base stations, the
combination of the base stations being used for transmitting a signal to the
coinmunication device.
v
30 Claim 14
A program for causing a computer to f~~nctioasn:
a setting unit configured to set a timing at which a predetennined signal is
transmitted only from one of a plurality of base stations having an identical cell ID;
and
a determilling unit configured to, based on a reception result of a
5 conimunication device at the timing, detennine a coinbination of base stations from
the plurality of base stations, the combination of the base stations being used for
transmitting a signal to the coinmunication device.
Claim 15
A colllmunication control device comprising:
a setting unit configured to set a timing at which a predetennined signal is
transmitted only from one of a plurality of base stations having an identical cell ID;
and
an acquisition unit configured to acquire a detection result obtained by a
15 co~l~municatiodne vice detecting an interference coinponent at the timing.
Dated this December 3 1, 20 13
ATTORNEY FOR THE APPLICANT[S]