Description
Title of Invention
COMMUNICATION CONTROL METHOD, COMMUNICATION SYSTEM, AND
5 MANAGEMENT SERVER
Technical Field
[0001]
The present invention relates to a communication control method, a
10 communication system, and a management server.
Background Art
[0002]
Recently, a heterogeneous network has been suggested as the next-
15 generation communication network. This heterogeneous network is a network in
which a plurality of kinds of small-or-medium-scale base stations coexist in a macrocell
by performing underlay transmission or spectrum sharing. A Remote
RadioHead (RRH) cell base station, a hot zone base station (Pico/micro-cell eNB), a
femto-cell base station (Home eNB), a relay device (relay base station), and the like
20 are referred to as small-or-medium-scale base stations.
[0003]
Such a heterogeneous network has a problem that, when different base
stations such as a macro-cell base station and a femto-cell base station use the same
frequency, improvement in area capacity is degraded by occurrence of interference.
25 In this connection, for example, Patent Literature 1 and Patent Literature 2 disclose
technologies for the problem of interference between different transmission devices.
Citation List
Patent Literature
30 [0004]
Patent Literature 1: Japanese Unexamined Patent Application Publication
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No. 2009-159452
Patent Literature 2: Japanese Unexamined Patent Application Publication
(Translation of PCT application) No. 2009-542043
5 Summary of Invention
Technical Problem
[0005]
When a transmission device transmits a radio signal to a reception device by
beam steering, it is possible to suppress a case in which the radio signal becomes an
10 interference wave for another reception device, and thus beam steering is useful as
interference-avoidance control for increasing area capacity. However, calibration is
necessary for the transmission device to perform the beam steering, and there is a
problem that overhead increases.
[0006]
15 Here, the present invention has been achieved in consideration of these
problems, and is intended to provide a new and improved communication control
method, communication system and management server that can achieve
improvement in area capacity by suppressing a case of performing transmission
beam steering.
20 Solution to Problem
[0007]
According to the first aspect of the present invention in order to achieve the
above-mentioned object, there is provided a communication control method
including: determining whether or not reception quality of a second reception device
25 satisfies a predetermined reference in a communication system including a first
transmission device, a first reception device, a second transmission device
secondarily using a frequency having been assigned to the first transmission device,
and the second reception device; and when it is determined that the reception quality
of the second reception device does not satisfy the predetermined reference,
30 additionally performing reception beam steering by the first reception device, beam
steering by the first transmission device, reception beam steering by the second
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reception device, or transmission beam steering by the second transmission device in
a predetermined order.
[0008]
The predetermined order may be an order of the reception beam steering by
5 the second reception device, the transmission beam steering by the second
transmission device, the reception beam steering by the first reception device, and
the beam steering by the first transmission device.
[0009]
The predetermined order may be an order of the reception beam steering by
10 the second reception device, the reception beam steering by the first reception device,
the transmission beam steering by the second transmission device, and the beam
steering by the first transmission device.
[0010]
The reception beam steering by the second reception device may be
15 reception null-steering in a direction-of-arrival of a radio signal transmitted from the
first transmission device.
[0011]
The transmission beam steering by the second transmission device may be
transmission null-steering in a direction-of-presence of the first reception device.
20 [0012]
The reception beam steering by the first reception device may be reception
null-steering in a direction-of-arrival of a radio signal transmitted from the second
transmission device.
[0013]
25 The transmission beam steering by the first transmission device may be
transmission null-steering in a direction-of-presence of the second reception device.
[0014]
When reception quality of the first reception device is higher than a
predetermined reference due to additional performance of the reception beam
30 steering by the first reception device, transmission power of a radio signal from the
first transmission device to the first reception device may be reduced within a range
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in which the reception quality of the first reception device is not lower than a
predetermined reference.
[0015]
When reception quality of the first reception device is higher than a
5 predetermined reference due to additional performance of the reception beam
steering by the first reception device, transmission power of a radio signal from the
second transmission device to the second reception device may be increased within a
range in which the reception quality of the first reception device is not lower than a
predetermined reference.
10 [0016]
According to the second aspect of the present invention in order to achieve
the above-mentioned object, there is provided a communication system including: a
first management server for managing communication between a first transmission
device and a first reception device; and a second management server for managing
15 communication between a second transmission device, which secondarily uses a
frequency having been assigned to the first transmission device, and a second
reception device, in which the second management server determines whether or not
reception quality of the second reception device satisfies a predetermined reference
in a communication system including the first transmission device, the first reception
20 device, the second transmission device secondarily using the frequency having been
assigned to the first transmission device, and the second reception device, and in
which, when it is determined that the reception quality of the second reception device
does not satisfy the predetermined reference, the first management server or the
second management server additionally performs reception beam steering by the first
25 reception device, beam steering by the first transmission device, reception beam
steering by the second reception device, or transmission beam steering by the second
transmission device in a predetermined order.
Advantageous Effects of Invention
[0017]
30 According to the present invention as described above, it is possible to
achieve improvement in area capacity by suppressing a case of performing
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transmission beam steering.
Brief Description of Drawings
[0018]
5 [Fig. 1] Fig. 1 is an explanatory diagram showing an example of a configuration of a
heterogeneous network.
[Fig. 2] Fig. 2 is an explanatory diagram showing an outline of each small-ormedium-
scale base station.
[Fig. 3] Fig. 3 is an explanatory diagram showing an example of a configuration of a
10 communication system according to an embodiment of the present invention.
[Fig. 4] Fig. 4 is an explanatory diagram showing an example of a result of
estimating a direction of arrival using MUSIC.
[Fig. 5] Fig. 5 is an explanatory diagram showing a detailed example of reception
beam steering.
15 [Fig. 6] Fig. 6 is a flowchart illustrating operation according to a first embodiment of
the present invention.
[Fig. 7] Fig. 7 is a flowchart illustrating operation according to a second embodiment
of the present invention.
20 Description of Embodiments
[0019]
Hereinafter, preferred embodiments of the present invention will be
described in detail with reference to the appended drawings. Note that, in this
specification and the drawings, elements that have substantially the same function
25 and structure are denoted with the same reference signs, and repeated explanation is
omitted.
[0020]
In addition, in this specification and the drawings, a plurality of elements
having substantially the same functional configuration may be distinguished from
30 each other by each having a different letter added to the same reference numeral.
For example, a plurality of elements having substantially the same functional
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configuration are distinguished from each other as communication terminals 20A,
20B, and 20C, if necessary. However, if it is not particularly necessary to
distinguish each of a plurality of elements having substantially the same functional
configuration, only the same reference numeral is assigned. For example, if it is not
5 particularly necessary to distinguish the communication terminals 20A, 20B, and
20C, they are simply referred to as the communication terminal 20.
[0021]
According to an order of items shown below, "Embodiments for
Implementing Invention" will be described.
10 1. Example of Configuration of Heterogeneous Network
2. Outline of Embodiments of Present Invention
3. Methods of Performing Respective Beam Steering Operations
4. First Embodiment of Present Invention
5. Second Embodiment of Present Invention
15 6. Conclusion
[0022]

[0023]
<1. Example of Configuration of Heterogeneous Network >
20 An embodiment of the present invention can be applied to, for example, a
communication system in which a plurality of local networks coexist using the same
frequency. An example of such a communication system is a heterogeneous
network.
[0024]
25 The heterogeneous network is a network in which a plurality of kinds of
small-or-medium-scale base stations coexist in a macro-cell by performing underlay
transmission or spectrum sharing. A Remote RadioHead (RRH) cell base station, a
hot zone base station (Pico/micro-cell eNB), a femto-cell base station (Home eNB), a
relay device (relay base station), and the like are referred to as small-or-medium-
30 scale base stations. Here, underlay transmission is a form of transmission in which
transceivers present within a range at which the transceivers interfere with mutual
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communication links perform communication using the same frequency channel. A
transmitter on a side that secondarily uses a frequency according to underlay
transmission needs to adjust an extra interference level in order not to cause fatal
interference in a communication link of a primary user. A configuration of a
5 heterogeneous network will be described in detail below.
[0025]
Fig. 1 is an explanatory diagram showing an example of a configuration of a
heterogeneous network. As shown in Fig. 1, a heterogeneous network includes a
macro-cell base station 10 (which has the same meaning as a base station 10), a relay
10 device 30, a hot zone base station 31, a femto-cell base station 32, RRH cell base
stations 33, and management servers 16Aand 16B.
[0026]
The management server 16A receives management information indicating a
state of a cell formed by the macro-cell base station 10 from each base station 10,
15 and controls communication in a cell formed by each base station 10 on the basis of
the management information. Likewise, the management server 16B receives
management information indicating a state of a cell formed by the femto-cell base
station 32 from the femto-cell base station 32, and controls communication in the cell
formed by the femto-cell base station 32 on the basis of the management information.
20 Also, the management servers 16A and 16B have functions for the macro-cell base
station 10 and a small-or-medium-scale base station to operate in cooperation.
Functions of the management servers 16 may be installed in the macro-cell base
station 10 or some small-or-medium-scale base stations. Also, the management
servers 16 may have functions of Mobile Management Entities (MMEs) or gateway
25 devices.
[0027]
The macro-cell base station 10 manages small-or-medium-scale base
stations and communication terminals 20 in a macro-cell. For example, the macrocell
base station 10 manages communication between the relay device 30 and the
30 communication terminals 20 present in the cell formed by the macro-cell base station
10. For example, the macro-cell base station 10 manages scheduling information
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for communication between the relay device 30 and the communication terminals 20
present in the cell.
[0028]
The hot zone base station 31 (pico-cell base station and micro-cell base
5 station) has lower maximum transmission power than the macro-cell base station 10,
and communicates with the macro-cell base station 10 using an interface such as X2,
SI and the like of a core network. In addition, the hot zone base station 31 forms an
Open Subscriber Group (OSG) that can be accessed from any of the communication
terminals 20.
10 [0029]
The femto-cell base station 32 has lower maximum transmission power than
the macro-cell base station 10, and communicates with the macro-cell base station 10
using a packet switching network such as ADSL. Alternatively, the femto-cell base
station 32 can also communicate with the macro-cell base station 10 through a
15 wireless link. In addition, the femto-cell base station 32 forms a Closed Subscriber
Group (CSG) that can be accessed from the limited communication terminals 20 only.
[0030]
The RRH cell base stations 33 are connected with the macro-cell base
station 10 through optical fibers. For this reason, the macro-cell base station 10 can
20 transmit a signal to the RRH cell base stations 33A and 33B disposed in different
geographical locations through the optical fibers, and cause the radio signal to be
transmitted from the RRH cell base stations 33A and 33B. For example, only an
RRH cell base station 33 close to the location of a communication terminal 20 can be
used. In addition, functions of a control system are installed in the macro-cell base
25 station 10 to select an optimum transmission form according to distribution of the
communication terminals 20.
[0031]
Outlines of the respective small-or-medium-scale base stations described
above are shown in Fig. 2. These small-or-medium-scale base stations such as the
30 hot zone base station 31 and the femto-cell base station 32 may increase the total
capacity by secondarily using a frequency used by the macro-cell base station 10.
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[0032]
For example, when the femto-cell base station 32 transmits a radio signal to
a communication terminal 20D by performing transmission beam steering, it is
possible to suppress the amount of interference that is imposed on other
5 communication in the macro-cell by the femto-cell base station 32, and thus the total
capacity in the whole macro-cell can be increased. However, calibration is
necessary for the femto-cell base station 32 to perform transmission beam steering,
and there is a problem that overhead increases.
[0033]
10 Here, embodiments of the present invention have been created based on the
above fact. According to the embodiments of the present invention, it is possible to
achieve improvement in area capacity by suppressing cases of performing
transmission beam steering. Such embodiments of the present invention will be
described below.
15 [0034]
<2. Outline of Embodiments of Present Invention >
First, a configuration of a communication system 1 according to an
embodiment of the present invention, which can be applied to the above-described
heterogeneous network, will be described with reference to Fig. 3.
20 [0035]
Fig. 3 is an explanatory diagram showing an example of a configuration of a
communication system 1 according to an embodiment of the present invention. As
shown in Fig. 3, the communication system 1 according to the embodiment of the
present invention includes a management server 16A (first management server), a
25 management server 16B (second management server), a reception device 20A (first
reception device), a reception device 20B (second reception device), a transmission
device 40A (first transmission device), and a transmission device 40B (second
transmission device). Here, the reception device 20A and the reception device 20B
correspond to, for example, the respective communication terminals 20 shown in Fig.
30 1, the transmission device 40A corresponds to, for example, the macro-cell base
station 10 shown in Fig. 1, and the transmission device 40B corresponds to, for
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example, the femto-cell base station 32 shown in Fig. 1.
[0036]
The management server 16A implements a first communication service by
controlling communication between the transmission device 40A and the reception
5 device 20A, and the management server 16B implements a second communication
service by controlling communication between the transmission device 40B, which
uses the same frequency as the transmission device 40A, and the reception device
20B.
[0037]
10 In this communication system 1, as shown in Fig. 3, a radio signal
transmitted from the transmission device 40A acts as an interference wave for the
communication terminal 20B, and a radio signal transmitted from the transmission
device 40B acts as an interference wave for the communication terminal 20A.
[0038]
15 Here, when it is desired to improve reception quality of the reception device
20B, the management server 16B causes some devices to additionally perform
transmission beam steering or reception beam steering in a predetermined order,
thereby achieving improvement in the reception quality of the reception device 20B.
[0039]
20 Specifically, the management server 16B determines whether or not the
reception quality of the reception device 20B satisfies a predetermined reference, and
causes reception beam steering by the reception device 20A, reception beam steering
by the reception device 20B, transmission beam steering by the transmission device
40A and transmission beam steering by the transmission device 40B in a
25 predetermined order. Due to this configuration, it is possible to obtain the reception
; quality of the reception device 20B that satisfies the predetermined reference while
suppressing cases of performing transmission beam steering.
[0040]
Here, reception beam steering by the reception device 20A is reception null-
30 steering in a direction-of-arrival of the radio signal transmitted from the transmission
device 40B. Likewise, reception beam steering by the reception device 20B is
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reception null-steering in a direction-of-arrival of the radio signal transmitted from
the transmission device 40A.
[0041]
Also, transmission beam steering by the transmission device 40A is
5 transmission null-steering in a direction-of-presence of the reception device 20B.
Likewise, transmission beam steering by the transmission device 40B is transmission
null-steering in a direction-of-presence of the reception device 20A.
[0042]
A method of performing each of these beam steering operations will be
10 described below prior to descriptions of a first embodiment and a second
embodiment.
[0043]
<3. Methods of Performing Respective Beam Steering Operations>
(Reception Beam Steering by Reception Device 20A)
15 On the basis of an instruction from the management server 16A or 16B, the
reception device 20A performs reception beam steering for suppressing a reception
level of an interference wave from the transmission device 40B according to, for
example, a method described below.
[0044]
20 First, the management server 16A assigns a slot through which the reception
device 20A and the transmission device 40B perform communication for
beamforming to the reception device 20A, and requests the management server 16B
to assign the slot to the transmission device 40B.
[0045]
25 The reception device 20A receives a preamble signal, a pilot signal or a
reference signal transmitted from the transmission device 40B through the assigned
slot, and acquires a channel matrix indicating a propagation path response between
the reception device 20A and the transmission device 40B. The reception device
20A may construct a covariance matrix using the transmission signal from the
30 transmission device 40B and use the covariance matrix as the channel matrix.
[0046]
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Using a direction-of-arrival estimation algorithm, such as MUSIC, and
cyclostationary, the reception device 20A estimates a direction-of-arrival of the
interference wave and a feature quantity of the signal, and performs reception beam
steering by which a null is steered in the direction-of-arrival of the interference wave.
5 [0047]
Fig. 4 is an explanatory diagram showing an example of a result of
estimating a direction of arrival using MUSIC. As shown in Fig. 4, according to
MUSIC, it is possible to estimate a direction-of-arrival of a desired wave (0 degrees
in the example shown in Fig. 4) and a direction-of-arrival of an interference wave (70
10 degrees in the example shown in Fig. 4).
[0048]
Fig. 5 is an explanatory diagram showing a detailed example of reception
beam steering. As shown in Fig. 5, a null is set in the direction-of-arrival of the
interference wave by reception beam steering to suppress a reception level of the
15 interference wave, and thereby a reception gain (difference in reception level
between the desired wave and the interference wave) of 55 dB is obtained in the
example shown in Fig. 5.
[0049]
Although the example in which the management servers 16A and 16B
20 assign a slot through which communication for beamforming is performed has been
described above, a method of performing reception beam steering is not limited to
such an example. For example, the reception device 20A may receive a PBCH or a
PDCCH transmitted by the transmission device 40B to know a transmission slot of
the transmission device 40B, and perform reception beam steering on the basis of a
25 signal received from the transmission device 40B through the transmission slot.
Alternatively, the reception device 20A may acquire information, such as the
transmission slot of the transmission device 40B or a reference pattern, from the
management server 16B via the management server 16A.
[0050]
30 Alternatively, the reception device 20A may perform reception beam
steering using a reception beamforming algorithm, such as Minimum Mean Square
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Error (MMSE), on the basis of Recursive Least Squares (RLS) or Least Mean
Squares (LMS) from the estimation results of the direction of arrival and the feature
quantity.
[0051]
5 When location information on the reception device 20A and the
transmission device 40B can be acquired by a location estimation technology such as
GPS, the reception device 20A may estimate the direction-of-arrival of the
interference wave from the transmission device 40B on the basis of the location
information on the reception device 20A and the transmission device 40B.
10 [0052]
(Reception Beam Steering by Reception Device 20B)
On the basis of an instruction from the management server 16A or 16B, the
reception device 20B performs reception beam steering for suppressing a reception
level of an interference wave from the transmission device 40A according to, for
15 example, a method described below.
[0053]
First, the management server 16B assigns a slot through which the reception
device 20B and the transmission device 40A perform communication for
beamforming to the reception device 20B, and requests the management server 16A
20 to assign the slot to the transmission device 40A.
[0054]
The reception device 20B receives a preamble signal, a pilot signal or a
reference signal transmitted from the transmission device 40A through the assigned
slot, and acquires a channel matrix indicating a propagation path response between
25 the reception device 20B and the transmission device 40A. The reception device
20B may construct a covariance matrix using the transmission signal from the
transmission device 40A and use the covariance matrix as the channel matrix.
[0055]
Using a direction-of-arrival estimation algorithm, such as MUSIC, and
30 cyclostationary, the reception device 20B estimates a direction-of-arrival of the
interference wave and a feature quantity of the signal, and performs reception beam
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steering by which a null is steered in the direction-of-arrival of the interference wave.
[0056]
Although the example in which the management servers 16A and 16B
assign a slot through which communication for beamforming is performed has been
5 described above, a method of performing reception beam steering is not limited to
such an example. For example, the reception device 20B may receive a PBCH or a
PDCCH transmitted by the transmission device 40A to know a transmission slot of
the transmission device 40A, and perform reception beam steering on the basis of a
signal received from the transmission device 40A through the transmission slot.
10 Alternatively, the reception device 20B may acquire information, such as the
transmission slot of the transmission device 40A or a reference pattern, from the
management server 16A via the management server 16B.
[0057]
Alternatively, the reception device 20B may perform reception beam
15 steering using a reception beamforming algorithm, such as MMSE, on the basis of
RLS or LMS from the estimation results of the direction of arrival and the feature
quantity.
[0058]
When location information on the reception device 20B and the
20 transmission device 40A can be acquired by a location estimation technology such as
GPS, the reception device 20B may estimate the direction-of-arrival of the
interference wave from the transmission device 40A on the basis of the location
information on the reception device 20B and the transmission device 40A.
[0059] ]
25 (Transmission Beam Steering by Transmission Device 40A)
On the basis of an instruction from the management server 16A or 16B, the
transmission device 40A performs transmission beam steering for suppressing an
interference level imposed on the reception device 20B according to, for example, a j
method described below. i
30 [0060]
First, the management server 16A assigns a slot through which the I
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transmission device 40A and the reception device 20B perform communication for
beamforming to the transmission device 40A, and requests the management server
16B to assign the slot to the reception device 20B.
[0061]
5 The transmission device 40A receives a preamble signal, a pilot signal or a
reference signal transmitted from the reception device 20B through the assigned slot,
and acquires a channel matrix indicating a propagation path response between the
reception device 20B and the transmission device 40A. The transmission device
40A may construct a covariance matrix using the transmission signal from the
10 reception device 20B and use the covariance matrix as the channel matrix.
[0062]
Using a direction-of-arrival estimation algorithm, such as MUSIC, and
cyclostationary, the transmission device 40A estimates a direction-of-arrival of the
signal from the reception device 20B and a feature quantity of the signal, and
15 performs transmission beam steering by which a null is steered in the direction-ofarrival
of the signal.
[0063]
Although the example in which the management servers 16A and 16B
assign a slot through which communication for beamforming is performed has been
20 described above, a method of performing transmission beam steering is not limited to
such an example. For example, the transmission device 40A may receive a PBCH
or a PDCCH transmitted by the reception device 20B to know a slot through which
the reception device 20B performs transmission, and perform transmission beam
steering on the basis of a signal received from the reception device 20B through the
25 slot. Alternatively, the transmission device 40A may acquire information, such as
the transmission slot of the transmission device 20B or a reference pattern, from the
management server 16B via the management server 16A.
[0064]
Alternatively, the transmission device 40A may perform transmission beam
30 steering using a transmission beamforming algorithm such as Minimum Mean
Square Error (MMSE) on the basis of Recursive Least Squares (RLS) or Least Mean
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Squares (LMS) from the estimation results of the direction of arrival and the feature
quantity of the signal from the reception device 20B.
[0065]
When location information on the reception device 20B and the
5 transmission device 40A can be acquired by a location estimation technology such as
GPS, the transmission device 40A may estimate a direction-of-presence of the
reception device 20B on the basis of the location information on the reception device
20B and the transmission device 40A.
[0066]
10 (Transmission Beam Steering by Transmission Device 40B)
On the basis of an instruction from the management server 16A or 16B, the
transmission device 40B performs transmission beam steering for suppressing an
interference level imposed on the reception device 20A according to, for example, a
method described below.
15 [0067]
First, the management server 16B assigns a slot through which the
transmission device 40B and the reception device 20A perform communication for
beamforming to the transmission device 40B, and requests the management server
16B to assign the slot to the reception device 20A.
20 [0068]
The transmission device 40B receives a preamble signal, a pilot signal or a
reference signal transmitted from the reception device 20A through the assigned slot,
and acquires a channel matrix indicating a propagation path response between the
reception device 20A and the transmission device 40B. The transmission device
25 40B may construct a covariance matrix using the transmission signal from the
reception device 20A and use the covariance matrix as the channel matrix. I
[0069]
Using a direction-of-arrival estimation algorithm, such as MUSIC, and cyclostationary, the transmission device 40B estimates a direction-of-arrival of the
30 signal from the reception device 20A and a feature quantity of the signal, and
performs transmission beam steering by which a null is steered in the direction-offe
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arrival of the signal.
[0070]
Although the example in which the management servers 16A and 16B
assign a slot through which communication for beamforming is performed has been
5 described above, a method of performing transmission beam steering is not limited to
such an example. For example, the transmission device 40B may receive a PBCH
or a PDCCH transmitted by the reception device 20A to know a slot through which
the reception device 20A performs transmission, and perform transmission beam
steering on the basis of a signal received from the reception device 20B through the
10 slot. Alternatively, the transmission device 40B may acquire information, such as
the transmission slot of the transmission device 20A or a reference pattern, from the
management server 16A via the management server 16B.
[0071]
Alternatively, the transmission device 40B may perform transmission beam
15 steering using a transmission beamforming algorithm such as Minimum Mean
Square Error (MMSE) on the basis of Recursive Least Squares (RLS) or Least Mean
Squares (LMS) from the estimation results of the direction of arrival and the feature
quantity of the signal from the reception device 20A.
[0072]
20 When location information on the reception device 20A and the
transmission device 40B can be acquired by a location estimation technology such as
GPS, the transmission device 40B may estimate a direction-of-presence of the
reception device 20A on the basis of the location information on the reception device
20A and the transmission device 40B.
25 [0073]
<4. First Embodiment of Present Invention> {
Examples of methods of performing respective beam steering operations j
have been described above. Next, a first embodiment of the present invention for
performing the above-described respective operations of beam steering stage by
30 stage will be described in detail.
[0074]
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An SINR of the reception device 20B is indicated below as SINR_B, and a
required SINR of the reception device 20B is indicated below as SINRreq. Also, a
reception gain of the reception device 20B that is obtained when the transmission
device 40A performs transmission beam steering is indicated as GtxABF, and a
5 reception gain of the reception device 20B that is obtained when the reception device
20A performs reception beam steering is indicated as GrxABF. Likewise, a
reception gain of the reception device 20B that is obtained when the transmission
device 40B performs transmission beam steering is indicated as GtxBBF, and a
reception gain of the reception device 20B that is obtained when the reception device
10 20B performs reception beam steering is indicated as GrxBBF.
[0075]
For example, the reception gain GrxBBF of the reception device 20B that
is obtained when the reception device 20B performs reception beam steering
corresponds to a difference in reception level between the desired wave and the
15 interference wave shown in Fig. 5. Also, the reception gain GtxABF of the
reception device 20B that is obtained when the transmission device 40A performs
transmission beam steering is a gain that is obtained from a reduction in an
interference level imposed on the reception device 20B by the transmission device 40A.
20 [0076] [
If the transmission device 40B performs transmission beam steering, the J
amount of interference imposed on the reception device 20A is reduced when a radio
signal is transmitted using the same transmission power, and thus the transmission
device 40B can improve SINRB of the reception device 20B by increasing the j
25 transmission power. Alternatively, since the amount of interference imposed on the
reception device 20A is reduced when the transmission device 40B performs !
transmission beam steering, the transmission device 40A that transmits the radio
signal to the reception device 20A can reduce the transmission power, and as a result,
can improve SINRB of the reception device 20B. In this way, the reception gain
30 GtxABF of the reception device 20B that is obtained when the transmission device
40A performs transmission beam steering includes a gain that is obtained from an
£ SP262848WO00
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increase in the transmission power of the transmission device 40B or a reduction in
the transmission power of the transmission device 40A within a range in which an
SINR of the reception device 20A is not lower than a required SINR.
[0077]
5 Also, when the reception device 20A performs reception beam steering, the
SINR of the reception device 20A improves. As a result, within a range in which an
SINR of the reception device 20A is not lower than the required SINR, the
transmission device 40A can reduce the transmission power, or the transmission
device 40B can increase the transmission power. In this way, the reception gain
10 GrxABF of the reception device 20B that is obtained when the reception device
20A performs reception beam steering includes a gain obtained from an increase in
the transmission power of the transmission device 40B or a reduction in the
transmission power of the transmission device 40A. j
[0078]
15 Fig. 6 is a flowchart illustrating operation according to the first embodiment
of the present invention. As illustrated in Fig. 6, first, the management server 16B !
determines whether or not SINRB of the reception device 20B reported from the
transmission device 40B satisfies SINRreq of the reception device 20B (S204). A I
subject of each operation including the determination is not particularly limited, and
20 for example, any one of the reception device 20B, the transmission device 40B and the management server 16A may perform each operation. S212 [
[0079]
When SINRB is lower than SINRreq, the management server 16B
instructs the reception device 20B to perform reception beam steering, and the
25 reception device 20B starts reception beam steering (S208). Then, the management
server 16B determines whether or not SINRBBF (SINRBGrxBBF) of the S
reception device 20B after the reception beam steering satisfies SINRreq (S212).
[0080]
When SINR_B_BF (SINR_BG_rxB_BF) is lower than SINRreq in S212,
30 the management server 16B instructs the transmission device 40B to perform
transmission beam steering, and the transmission device 40B starts transmission
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beam steering (S216). Then, the management server 16B determines whether or
not SINR_B_BF (SINR_BG_rxB_BFG_txB_BF) of the reception device 20B after
the transmission beam steering satisfies SINRreq (S220).
[0081]
5 When SINRBBF (SINR_BG_rxB_BFG_txB_BF) is lower than
SINRreq in S220, the management server 16B instructs the reception device 20A to
perform reception beam steering, and the reception device 20A starts reception beam
steering (S224). Then, the management server 16B determines whether or not
SINRBBF (SINR_B-G_rxB_BF-G_txB_BFG_rxA_BF) of the reception device ;
10 20B after the reception beam steering satisfies SINRreq (S228).
[0082]
When SINR_B_BF (SINR_BG__rxB_BFG_txB_BFG_rxA_BF) is lower
than SINRreq in S228, the management server 16B instructs the transmission
device 40A to perform transmission beam steering, and the transmission device 40A f
15 starts transmission beam steering (S232). Then, the management server 16B
determines whether or not SINRBBF (SINRBGrxBBFGtxBBFG rxABFGtxABF) of the reception device 20B j
after the transmission beam steering satisfies SINRreq (S236).
[0083] j
20 When SINRBBF
(SINR_BG_rxB_BFG_txB_BFG_rxA_BFG_txA_BF) is lower than SINR_req in
S236, the management server 16B performs control for lowering the required SINR
of the reception device 20B (S240). For example, the management server 16B
instructs the transmission device 40B to reduce a transmission rate, or lowers a QoS
25 level. After this, the process is finished.
[0084] J
As described above, in the first embodiment of the present invention, beam
steering is additionally performed according to a necessity in the order of reception
beam steering by the reception device 20B, transmission beam steering by the
30 transmission device 40B, reception beam steering by the reception device 20A and
transmission beam steering by the transmission device 40A. In this way, by
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performing reception beam steering prior to transmission beam steering, cases of
performing transmission beam steering that involve overhead can be suppressed.
[0085]
In addition, SINRBBF of the reception device 20B mentioned above may
5 be a value estimated through numerical analysis or a value measured from the
reception device 20B after actual beamforming. The above-described process of
Fig. 6 is performed once and then finished, but may be repeatedly performed. Also,
when a predetermined period elapses at each branch (S212, S220, and the like)
shown in Fig. 6, the process may be finished.
10 [0086]
<5. Second Embodiment of Present Invention>
Fig. 7 is a flowchart illustrating operation according to a second
embodiment of the present invention. As illustrated in Fig. 7, first, the management
server 16B determines whether or not SINRB of the reception device 20B reported j
15 from the transmission device 40B satisfies SINRreq of the reception device 20B
(S304). A subject of each operation including the determination is not particularly
limited, and for example, any one of the reception device 20B, the transmission
device 40B and the management server 16A may perform each operation. S212
[0087]
20 When SINRB is lower than SINRreq, the management server 16B
instructs the reception device 20B to perform reception beam steering, and the
reception device 20B starts reception beam steering (S308). Then, the management
server 16B determines whether or not SINRBJBF (SINR_BG_rxB_BF) of the
reception device 20B after the reception beam steering satisfies SINRreq (S312). 25 [0088]
When SINR B_BF (SINR_BG_rxB_BF) is lower than SINR_req in S312,
the management server 16B instructs the reception device 20A to perform reception
beam steering, and the reception device 20A starts transmission beam steering (S316).
Then, the management server 16B determines whether or not SINRBBF
30 (SINR_B-G_rxB_BF-G_rxA_BF) of the reception device 20B after the reception
beam steering satisfies SINRreq (S320).
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[0089] I
When SINR_B_BF (SINR_B-G_rxB_BFG_rxA_BF) is lower than
SINR_req in S320, the management server 16B instructs the transmission device
40B to perform transmission beam steering, and the transmission device 40B starts
5 transmission beam steering (S324). Then, the management server 16B determines
whether or not SINR_B_BF (SINR_BG_rxB_BFG_rxA_BFG_txB_BF) of the
reception device 20B after the transmission beam steering satisfies SINRreq (S328).
[0090]
When SINRBBF (SrNR_BG_rxB_BF-G_rxA_BFG_txB_BF) is lower
10 than SINR_req in S328, the management server 16B instructs the transmission •
device 40A to perform transmission beam steering, and the transmission device 40A
starts transmission beam steering (S332). Continuously, the management server
16B determines whether or not SINRBBF
(SINRBGrxBBFGrxABFGtxBBFGtxABF) of the reception device 20B j
15 after the transmission beam steering satisfies SINRreq (S336).
[0091] !
When SINR_B_BF j
(SINR_BG_rxB_BFG_rxA_BFG_txB_BFG_txA_BF) is lower than SINR_req in j
S336, the management server 16B performs control for lowering the required SINR 20 of the reception device 20B (S340). For example, the management server 16B
instructs the transmission device 40B to reduce a transmission rate, or lowers a QoS
level. After this, the process is finished. [0092]
As described above, in the second embodiment of the present invention,
25 beam steering is additionally performed according to a necessity in the order of
reception beam steering by the reception device 20B, reception beam steering by the
reception device 20A, transmission beam steering by the transmission device 40B
and transmission beam steering by the transmission device 40A. In this way, in the
second embodiment of the present invention, reception beam steering is performed 30 with a higher priority than in the first embodiment, so that a case of performing 1
transmission beam steering that involves overhead can be further suppressed.
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[0093]
In addition, SINRBBF of the reception device 20B mentioned above may
be a value estimated through numerical analysis or a value measured from the
reception device 20B after actual beamforming. The above-described process of
5 Fig. 7 is performed once and then finished, but may be repeatedly performed. Also,
when a predetermined period elapses at each branch (S312, S320, and the like)
shown in Fig. 7, the process may be finished.
[0094]
<6. Conclusion>
10 As described above, in each embodiment of the present invention, reception
beam steering is performed prior to transmission beam steering, so that cases of
performing transmission beam steering can be suppressed. As a result, it is possible
to suppress overhead that results from calibration for transmission beam steering.
[0095]
15 The preferred embodiments of the present invention have been described
above with reference to the accompanying drawings, whilst the present invention is
not limited to the above examples, of course. A person skilled in the art may find
various alternations and modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the
20 present invention. For example, the respective steps in the process of the
communication system 1 do not have to be processed in a sequence described as a
flowchart according to time. For example, the respective steps in the process of the <
communication system 1 may be processed in a different sequence from a sequence I
described as a flowchart, or in parallel. Also, a computer program for causing
25 hardware, such as a CPU, a ROM and a RAM, embedded in the management servers
16, the transmission devices 40 and the reception devices 20 to perform the same
function as the management servers 16, the transmission devices 40 and the reception
devices 20 mentioned above can be written.
[0096]
30 In addition, "secondary use" in this specification denotes performing an
additional or substitutional communication service (a second communication service)
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using a portion or all of a frequency band assigned to a first communication service.
Here, the first communication service and the second communication service may be
communication services of different types or the same type. The communication
services of different types may be two or more different types of communication
5 services that are selected from a plurality of types of communication services, for ?
example, a digital TV broadcasting service, a satellite communication service, a
mobile communication service, a wireless LAN access service and a Peer-to-Peer
(P2P) connection service.
[0097]
10 Meanwhile, the communication services of the same type may include, for ;
example, a relationship between a service based on a macro-cell provided by a communication service provider and a service based on a femto-cell managed by a
user or a Mobile Virtual Network Operator (MVNO) in a mobile communication
service. Also, the communication services of the same type may include a
15 relationship between a service provided by a macro-cell base station and a service l
provided in order to cover a spectrum hole by a relay station (relay node) in a communication service based on Long Term Evolution-Advanced (LTE-A).
[0098]
The second communication service may use a plurality of fragmented I
20 frequency bands that are aggregated using spectrum aggregation technology. Also,
the second communication service may be a supplementary communication service
provided by a group of femto-cells, a group of relay stations or a group of small-or- }
medium-scale base stations, which provide a smaller service area than a macro-cell i
base station, present within a service area of the macro-cell base station. The ?
25 outline of each embodiment of the present invention described above can be extensively applied to all types of such secondary uses.
Reference Signs List [0099]
30 16,16A, 16B Management server
20, 20A, 20B Reception device
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40, 40A, 40B Transmission device

CLAIMS
Claim 1
A communication control method comprising:
determining whether or not reception quality of a second reception device
5 satisfies a predetermined reference in a communication system including a first
transmission device, a first reception device, a second transmission device
secondarily using a frequency having been assigned to the first transmission device,
and the second reception device; and
vv'hen it is determined that the reception quality of the second reception
10 device does not satisfy the predetermined reference, additionally performing
reception beam steering by the first reception device, beam steering by the first
transmission device, reception beam steering by the second reception device, or
transmission beam steering by the second transmission device in a predetermined
order.
15
Claim 2
The communication control method according to claim 1,
wherein the predetermined order is an order of the reception beam steering
by the second reception device, the transmission beam steering by the second
20 transmission device, the reception beam steering by the first reception device, and
the beam steering by the first transmission device.
Claim 3
The communication control method according to claim 1,
25 wherein the predetermined order is an order of the reception beam steering
by the second reception device, the reception beam steering by the first reception
device, the transmission beam steering by the second transmission device, and the
beam steering by the first transmission device.
30 Claim 4
The communication control method according to claim 2,
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wherein the reception beam steering by the second reception device is
reception null-steering in a direction-of-arrival of a radio signal transmitted from the
first transmission device.
5 Claim 5
The communication control method according to claim 4,
wherein the transmission beam steering by the second transmission device is
transmission null-steering in a direction-of-presence of the first reception device.
10 Claim 6
The communication control method according to claim 5,
wherein the reception beam steering by the first reception device is
reception null-steering in a direction-of-arrival of a radio signal transmitted from the
second transmission device.
15
Claim 7
The communication control method according to claim 6,
wherein the transmission beam steering by the first transmission device is
transmission null-steering in a direction-of-presence of the second reception device.
20
Claim 8
The communication control method according to claim 7,
wherein, when reception quality of the first reception device is higher than
the predetermined reference due to additional performance of the reception beam
25 steering by the first reception device, transmission power of a radio signal from the
first transmission device to the first reception device is reduced within a range in
which the reception quality of the first reception device is not lower than the
predetermined reference.
30 Claim 9
The communication control method according to claim 7,
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wherein, when reception quality of the first reception device is higher than
the predetermined reference due to additional performance of the reception beam
steering by the first reception device, transmission power of a radio signal from the
second transmission device to the second reception device is increased within a range
- ••-^- 5 •"•• in which the reception quality of the first reception device is not lower than the
' . • predetermined reference.
Claim 10
A comrnunication system comprising:
10 a first management server for managing communication be^A'een a first
transmission device and a first reception device; and
a second management server for managing communication between a
second transmission device, which secondarily uses a frequency having been
assigned to the first transmission device, and a second reception device,
15 wherein the second management server determines whether or not reception
quality of the second reception device satisfies a predetermined reference in a
communication system including the first transmission device, the first reception
\ ....
device,'the second transmission device secondarily using the frequency having been
assigned to the first transmission device, and the second reception device, and
20 wherein, when it is determined that the reception quality of the second
reception device does not satisfy the predetermined reference, the first management
server or the second management server additionally performs reception beam
steering by the first reception device, beam steering by the first transmission device,
reception beam steering by the second reception device, or transmission beam
•' 25 steering by the second transmission device in a predetermined order.