U.S. patent application number 16/537635 was filed with the patent office on 2019-11-28 for communication control method, communication system, and management server.
This patent application is currently assigned to Sony Corporation. The applicant listed for this patent is Sony Corporation. Invention is credited to Ryota KIMURA, Ryo SAWAI.
Application Number | 20190364514 16/537635 |
Document ID | / |
Family ID | 44711684 |
Filed Date | 2019-11-28 |
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United States Patent
Application |
20190364514 |
Kind Code |
A1 |
SAWAI; Ryo ; et al. |
November 28, 2019 |
COMMUNICATION CONTROL METHOD, COMMUNICATION SYSTEM, AND MANAGEMENT
SERVER
Abstract
A management server in a network including a first transmitting
device that communicates with a first receiving device and a second
transmitting device that communicates with a second receiving
device. The management server includes a network interface that
receives a parameter corresponding to a level of improvement of
communication quality at the second receiving device, and a
processor that calculates an allowable interference amount at the
first receiving device based on the parameter.
Inventors: |
SAWAI; Ryo; (Tokyo, JP)
; KIMURA; Ryota; (Tokyo, JP) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Sony Corporation |
Tokyo |
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JP |
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Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
44711684 |
Appl. No.: |
16/537635 |
Filed: |
August 12, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15434737 |
Feb 16, 2017 |
10420037 |
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16537635 |
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13580986 |
Aug 24, 2012 |
9609603 |
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PCT/JP2011/001507 |
Mar 15, 2011 |
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15434737 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 52/265 20130101;
H04W 52/245 20130101; H04W 16/10 20130101; H04W 16/14 20130101;
H04W 52/243 20130101; H04W 52/343 20130101; H04W 72/0453 20130101;
H04W 72/082 20130101 |
International
Class: |
H04W 52/24 20060101
H04W052/24; H04W 72/08 20060101 H04W072/08; H04W 72/04 20060101
H04W072/04; H04W 52/26 20060101 H04W052/26; H04W 16/14 20060101
H04W016/14; H04W 52/34 20060101 H04W052/34; H04W 16/10 20060101
H04W016/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2010 |
JP |
2010-075336 |
Claims
1. (canceled)
2. A management server in a second communication service including
a first communication device, wherein the first communication
device is configured to use a part or a whole of a spectrum
assigned to a first communication service, the management server
comprising: circuitry configured to: calculate an allowable
interference amount from the first communication device to the
first communication service; and set a transmission power of the
first communication device according to the allowable interference
amount, wherein the allowable interference amount is calculated
based on a pathloss of a communication link between a particular
communication device that belongs to the first communication
service and a second communication device that belongs to the
second communication service.
3. The management server of claim 2, wherein the first
communication device is a base station or a user equipment.
4. The management server of claim 2, wherein the management server
is incorporated into a base station.
5. The management server of claim 2, wherein the particular
communication device is a user equipment configured to communicate
with a base station as part of the first communication service.
6. The management server of claim 5, wherein a second management
server manages the first communication service.
7. The management server of claim 6, wherein the second management
server is configured to control communication between the base
station and the particular communication device using the spectrum
assigned to the first communication service
8. The management server of claim 7, wherein the second management.
server is configured to determine a second transmission power from
the base station to the particular communication device.
9. A cooperation server comprising circuitry configured to:
communicate with a first management server managing a first
electronic device serving a second electronic device; communicate
with a second management server managing a third electronic device
serving a fourth electronic device; and calculate a first
transmission parameter of the first electronic device, wherein the
first transmission parameter of the first electronic device is
calculated in consideration of a first communication quality
required for the second electronic device, the first communication
quality being calculated based at least in part on a second
communication quality required for the fourth electronic device and
an allowable interference amount at the second electronic device,
the allowable interference amount based at least in part on
receiving powers of the second and fourth electronic devices,
interferences at the second and fourth electronic devices, and
interference plus noise powers at the second and fourth electronic
devices.
10. The cooperation server of claim 9, wherein a second
transmission parameter of the third electronic device is calculated
in consideration of the first communication quality.
11. The cooperation server of claim 10, wherein the circuitry is
further configured to calculate the first transmission parameter of
the first electronic device to ensure the allowable interference
amount at the second electronic device from the first electronic
device and the third electronic device is achieved.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/434,737, filed Feb. 16, 2017, which is a continuation of
U.S. application Ser. No. 13/580,986, filed Aug. 24, 2012 (now U.S.
Pat. No. 9,609,603), which is based on PCT filing
PCT/JP2011/001507, filed Mar. 15, 2011, and claims priority to JP
2010-075336, filed Mar. 29, 2010, the entire contents of each are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a communication control
method, a communication system, and a management server.
BACKGROUND ART
[0003] In recent years, a heterogeneous network has been proposed
as a next-generation communication network. The heterogeneous
network is a network in which a plurality of kinds of
small-to-medium-sized base stations coexist in a macro cell by
performing underlay transmission or spectrum sharing. The
small-to-medium-sized base stations involve a RRH (Remote
RadioHead) cell base station, a hotzone base station (Pico/micro
cell eNB), a femtocell base station (Home eNB), a relay node (relay
base station) and the like.
[0004] In such a heterogeneous network, there is a concern that,
when different base stations, such as a macro cell base station and
a femtocell base, station, for example, use the same frequency,
improvement of an area capacity is hindered due to the occurrence
of interference. Regarding such a concern, Patent Literature 1 and
Patent Literature 2, for example, disclose techniques to overcome
the interference issue between different transmitting devices.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Patent Laid-open No. 2009-159452
[0006] PTL 2: Published Japanese Translation No. 2009-542043 of PCT
International Publication
SUMMARY OF INVENTION
[0007] According to one exemplary embodiment, the disclosure is
directed to a management server in a network including a first
transmitting device configured to communicate with a first
receiving device and a second transmitting device configured to
communicate with a second receiving device, the management server
comprising: a network interface configured to receive a parameter
corresponding to a level of improvement of communication quality at
the second receiving device; a processor configured to calculate an
allowable interference amount at the first receiving device based
on the parameter, wherein the network communication unit is
configured to output the calculated allowable interference
amount.
[0008] The second transmitting device and the second receiving
device may communicate using a frequency that overlaps with a
frequency used for communication between the first transmitting
device and the first receiving device.
[0009] The network interface may be configured to receive
management information indicating a state of a cell formed by the
first transmitting device.
[0010] The processor may be configured to control communication in
the cell formed by the first transmitting device based on the
received management information.
[0011] The network communication unit may be configured to output
the calculated allowable interference amount to a second management
server that controls communications between the second transmitting
device and the second receiving device.
[0012] The processor may be configured to calculate a maximum
allowable interference amount based on the parameter, and the
allowable interference amount may be calculated to be less than the
maximum allowable interference amount.
[0013] The processor may be configured to set at least one of a
transmitting power of the first transmitting device and a
transmission rate of the first transmitting device based on the
allowable interference amount.
[0014] The processor may be configured to calculate the allowable
interference amount based on at least one or more of a reception
power at the first receiving device, a reception power at the
second receiving device, interference from the first transmitting
device at the second receiving device, interference from the second
transmitting device at the first transmitting device, a power of
the first receiving device and a power of the second receiving
device.
[0015] According to another exemplary embodiment, the disclosure is
directed to management server in a network including a first
transmitting device configured to communicate with a first
receiving device and a second transmitting device configured to
communicate with a second receiving device, the management server
comprising: a processor configured to calculate a parameter
corresponding to a level of improvement of communication quality at
the second receiving device; a network interface configured to
transmit the calculated parameter to a another management server,
and receive an allowable interference amount at the first receiving
device from the another management server, wherein the processor is
configured to control communications between the second
transmitting device and the second receiving device based on the
allowable interference amount.
[0016] The second transmitting device and the second receiving
device may communicate using a frequency that overlaps with a
frequency used for communication between the first transmitting
device and the first receiving device.
[0017] The network interface may be configured to receive
management information indicating a state of a cell formed by the
second transmitting device.
[0018] The processor may be configured to control communication in
the cell formed by the second transmitting device based on the
received management information.
[0019] The processor may be configured to determine whether to
improve the receiving communication quality based on a comparison
between a current communication quality and a desired communication
quality.
[0020] The processor may be configured to calculate the parameter
based on a relationship between the current communication quality
and the desired communication quality.
[0021] The relationship between the current communication quality
and the desired communication quality may be a ratio between the
desired communication quality and the current communication
quality.
[0022] The processor may be configured to control communications
between the second transmitting device and the second receiving
device so that an amount of interference caused by the second
transmitting device at the first receiving device is less than the
allowable interference amount.
[0023] According to another exemplary embodiment the disclosure is
directed to network comprising: a first management server
configured to control communications between a first transmitting
device and a first receiving device; a second management server
configured to control communications between a second transmitting
device and a second receiving device; a first processor, at the
second management server, configured to calculate a parameter
corresponding to a level of improvement of communication quality at
the second receiving device; a first network interface, at the
second management server, configured to transmit the calculated
parameter to the first management server; a second processor, at
the first management server, configured to calculate an allowable
interference amount at the first receiving device based on the
parameter; a second network interface, at the first management
server, configured to transmit the calculated allowable
interference amount to the second management server, wherein the
processor of the second management server is configured to control
communications between the second transmitting device and the
second receiving device based on the allowable interference
amount.
[0024] According to another exemplary embodiment, the disclosure is
directed to method of controlling communications in a network
including a first management server configured to control
communications between a first transmitting device and a first
receiving device and a second management server configured to
control communications between a second transmitting device and a
second receiving device, the method comprising: calculating, at the
second management server, a parameter corresponding to a level of
improvement of communication quality at the second receiving
device; transmitting the calculated parameter from the second
management server to the first management server; calculating, by
the first management server, an allowable interference amount at
the first receiving device based on the parameter; transmitting the
calculated allowable interference amount front the first management
server to the second management server; and controlling
communications between the second transmitting device and the
second receiving device based on the allowable interference
amount.
TECHNICAL PROBLEM
[0025] Assume the case where there are a first network composed of
a receiving device and a transmitting device and a second network,
and the first network suffers interference from the, second
network. In this case, the receiving quality in the receiving
device of the first network can be improved by increasing the
transmission power of the transmitting device of the first network,
for example.
[0026] However, with the increase in the transmission power of the
transmitting device of the first network, the amount of
interference from the first network to the second network increases
accordingly. Therefore, it has been difficult, to increase the
total capacity of the entire network merely by unilaterally
increasing the transmission power in one local network.
[0027] In light of the foregoing, it is desirable to provide novel
and improved communication control method, communication system,
and management server capable of increasing the total capacity of
the entire network by controlling a transmission parameter of each
transmitting device of different networks in cooperation between
the networks.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is an explanatory view showing an exemplary
architecture of a heterogeneous network;
[0029] FIG. 2 is an explanatory view showing an overview of each
small-to-medium-sized base station;
[0030] FIG. 3 is an explanatory view showing an exemplary
configuration of a communication system according to an embodiment
of the present invention;
[0031] FIG. 4 is a functional block diagram showing a configuration
of a management. server;
[0032] FIG. 5 is a sequence chart showing an overall operation in a
communication system;
[0033] FIG. 6 is an explanatory view showing a relationship between
a receiving quality improvement level Mreq desired for a second
reviving device 20 and an allowable interference amount in a first
receiving device 20A;
[0034] FIG. 7 is an explanatory view showing a relationship between
an allowable interference amount M' and an average communication
capacity in the case of obtaining the allowable interference amount
M' by transmission power control; and
[0035] FIG. 8 is an explanatory view showing a relationship between
an allowable interference amount M' and an average communication
capacity in the case of obtaining the allowable interference amount
M' by transmission rate control.
DESCRIPTION OF EMBODIMENTS
[0036] 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 appended
drawings, structural elements that have substantially the same
function and structure are denoted with the same reference
numerals, and repeated explanation of these structural elements is
omitted.
[0037] Further, in this specification and the drawings, each of a
plurality of structural elements having substantially the same
function is distinguished by affixing a different alphabetical
letter to the same reference numeral in some cases. For example, a
plurality of structural elements having substantially the same
function are distinguished like user equipments 20A, 20B and 20C
where necessary. However, when there is no particular need to
distinguish between a plurality of structural elements having
substantially the same function, they are denoted by the same
reference numeral. For example, when there is no particular need to
distinguish between the user equipments 20A, 20B and 20C, they are
referred to simply as the user equipment 20.
[0038] A preferred embodiment of the present invention will be
described hereinafter in the following order.
[0039] 1. Exemplary Architecture of Heterogeneous Network
[0040] 2. Overview of Embodiment of Present Invention
[0041] 3. Detailed Description of Operation by Embodiment of
Present Invention
[0042] 3-1. Determination of Necessity of Receiving Quality
Improvement (Step 1)
[0043] 3-2. Calculation of Receiving Quality Improvement Level
Expected Value Mreq (Step 2)
[0044] 3-3. Calculation of Allowable interference amount M (Step
3)
[0045] 3-4. Control of Transmission Power Based on Allowable
interference amount M (Step 4)
[0046] 4. Advantageous Effects of Embodiment of Present Invention
Indicated by Numerical Analysis Results
[0047] 5. Supplementary Description
[0048] 6. Summary
1. Exemplary Architecture of Heterogeneous Network
[0049] An embodiment of the present invention is applicable to
communication systems in which a plurality of local networks using
the same frequency coexist, for example. An example of such
communication systems is a heterogeneous network.
[0050] A heterogeneous network is a network in which a plurality of
kinds of small-to-medium-sized base stations coexist in a macro
cell by performing underlay transmission or spectrum sharing. The
small-to-medium-sized base stations may be a RRH (Remote RadioHead)
cell base station, a hotzone base station (Pico/micro cell eNB), a
femtocell base station (Home eNB), a relay node (relay base
station) and the like. Note that the underlay transmission is a
transmission mode in which a transmitter and a receiver existing in
the range that interferes with each other's communication link
perform communication using the same frequency channel. It is
necessary for the transmitter on the side of making secondary usage
of the frequency by the underlay transmission to adjust the
interfering level so that it does not act as critical interference
for the communication link of the one making the primary usage. The
architecture of the heterogeneous network is specifically described
below.
[0051] FIG. 1 is an explanatory view showing an exemplary
architecture of a heterogeneous network. Referring to FIG. 1, the
heterogeneous network includes a macro cell base station 10 (which
is synonymous with a base station 10), a relay node 30, a hotzone
base station 31, a femtocell base station 32, an RRH cell base
station 33 and management servers 16A and 16B.
[0052] The management server 16A receives management information
indicating the state of a cell formed by the macro cell base
station 10 from the macro cell base station 10 and controls
communication in the cell formed by the macro cell base station 10
based on the management information. Likewise, the management
server 16B receives management information indicating the state of
a cell formed by the femtocell base station 32 from the femtocell
base station 32 and controls communication in the cell formed by
the femtocell base station 32 based on the management information.
Further, the management servers 16A and 16B have functions for the
macro cell base station 10 and the small-to-medium-sized base
stations to operate in cooperation with each other. Note that the
functions of the management server 16 may be incorporated into the
macro cell base station 10 or any one of the small-to-medium-sized
base stations.
[0053] The macro cell base station 10 manages scheduling
information of the small-to-medium-sized base station 30 and the
user equipment 20 located inside the macro cell and can communicate
with the small-to-medium-sized base station 30 and the user
equipment 20 according to the scheduling information.
[0054] The hotzone base station 31 (a pico cell base station, a
micro cell base station) has the smaller maximum transmission power
than the macro cell base station 10 and communicates with the macro
cell base station 10 with use of an interface such as X2 or S1 of a
core network. Note that the hotzone base station 31 creates OSG
(Open Subscriber Group) which is accessible from any user equipment
20.
[0055] The femtocell base station 32 has the smaller maximum
transmission power than the macro cell base station 10 and
communicates, with the macro cell base station 10 with use of a
packet exchange network such as ADSL. Alternatively, the femtocell
base station 32 may communicate with the macro cell base station 10
by a radio link. Note that the femtocell base station 32 creates
CSG (Closed Subscriber Group) which is accessible only from the
limited user equipments 20.
[0056] The RRH cell base station 33 is connected with the macro
cell base station 10 by an optical fiber. Thus, the macro cell base
station 10 transmits signals to the RRH cell base stations 33A and
33B installed in geographically different places through the
optical fiber and allows the RRH cell base stations 33A and 33B to
transmit signals by radio. For example, only the RRH cell base
stations 33 close to the position of the user equipment 20 may be
used. Note that functions related to a control system are
incorporated into the macro cell base station 10, and optimum
transmission mode is selected according to the distribution of the
user equipments 20. [0031]
[0057] FIG. 2 shows the overview of the respective
small-to-medium-sized base stations described above. The
small-to-medium-sized base stations such as the hotzone base
station 31 and the femtocell base station 32 can increase the total
capacity by making secondary usage of the frequency used by the
macro cell base station 10.
[0058] If the transmission power of the femtocell base station 32
increases, the receiving quality in the user equipment 20D can be
improved. However, with the increase in the transmission power of
the femtocell base station 32, the amount of interference from the
femtocell base station 32 to other communication in the macro cell
increases accordingly. Therefore, it has been difficult to increase
the total capacity of the entire macro cell merely by unilaterally
increasing the transmission power of the femtocell base station
32.
[0059] Given such circumstances, an embodiment of the present
invention has been invented. According to the embodiment of the
present invention, it is possible to increase the total capacity of
the entire network by controlling a transmission parameter of each
transmitting device (e.g. the macro cell base station 10 and the
femtocell base station 32) of different networks in cooperation
between the networks. Such an embodiment of the present invention
is described hereinafter in detail.
2. Overview of Embodiment of Present Invention
[0060] Firstly, a configuration of a communication system 1
according to the embodiment of the present invention which is
applicable to the above-described heterogeneous network, for
example, is described with reference to FIG. 3.
[0061] FIG. 3 is an explanatory view showing an exemplary
configuration of the communication system 1 according to the
embodiment of the present invention. Referring to FIG. 3 the
communication system 1 according to the embodiment of the present
invention includes a management server 16A (first management
server), a management server 16B (second management server), a
receiving device 20A (first receiving device), a receiving device
20B (second receiving device), a transmitting device 40A (first
transmitting device), and a transmitting device 40B (second
transmitting device). Note that the receiving device 20A and the
receiving device 20B correspond to each receiving device 20 shown
in FIG. 1, the transmitting device 40A corresponds to the macro
cell base station 10 shown in FIG. 1, for example, and the
transmitting device 40B corresponds to the femtocell base station
32 shown in FIG. 1, for example.
[0062] The management server 16A controls communication by the
transmitting device 40A and the receiving device 20A, and the
management server 16B controls communication by the transmitting
device 40B, which makes secondary usage of the same frequency as
the transmitting device 40A, and the receiving device 20B.
[0063] In the communication system 1, as shown in FIG. 3, a radio
signal transmitted from the transmitting device 40A acts as an
interference wave in the receiving device 20B, and a radio signal
transmitted from the transmitting device 40B acts as an
interference wave in the receiving device 20A. Therefore, it is
important to appropriately control transmission parameters by the
transmitting devices 40A and 40B for optimization of SINR in the
receiving devices 20A and 20B. Hereinafter, after the overall
operation in the communication system 1 is schematically described
with reference to FIGS. 4 and 5, each operation is described in
detail in "3. Detailed Description of Operation by Embodiment of
Present Invention".
[0064] FIG. 4 is a functional block diagram showing a configuration
of the management servers 16A and 16B. Referring to FIG. 4, the
managernent server 16A includes a network communication unit 110,
an allowable interference amount calculation unit 120, a
transmission parameter setting unit 130, and a communication
control unit 140. Further, the management server 16B includes a
network communication unit 210, an expected value calculation unit
220 (improvement level calculation unit), a transmission power
setting unit 230, and a communication control unit 240. The network
communication unit 110 of the management server 16A is an interface
for communication with the management server 16B and the
transmitting device 40A, and the network communication unit 210 of
the management server 16B is an interface for communication with
the management server 16A and the transmitting device 40B. The
other components are described in conjunction with the overall
operation in the communication system 1, which is described below
with reference to FIGS. 4 and 5.
[0065] FIG. 5 is a sequence chart showing the. overall operation in
the communication system 1. Referring to FIG. 5, the overall
operation in the communication system 1 includes the following step
1 to step 4.
[0066] Step 1:
[0067] The expected, value calculation unit 220 of the management
server 16B determines whether it is necessary to improve the
receiving quality of the receiving device 20B. If it is necessary
to improve the receiving quality of the receiving device 20B, the
operation after the step 2 is performed.
[0068] Step 2:
[0069] The expected value calculation unit 220 of the management
Server 16B calculates an improvement level Mreq of the receiving
quality desired for the receiving device 20B. Then, the calculated
Mreq is notified to the management server 16A. Note that the
processing may be performed by a cooperation manager for the
management servers 16A and 16B to operate in cooperation with each
other. The same applies to the processing after the step 3.
[0070] Step 3:
[0071] The allowable interference amount calculation unit 120 of
the management server 16A calculates an ideal allowable
interference amount M' in the receiving device 20A which is
necessary for achieving Mreq, and determines an allowable
interference amount M (or an increment M of an allowable
interference amount) to be actually applied from the allowable
interference, amount M'. Then, the transmission parameter setting
unit 130 sets a transmission parameter (a transmission power or a
transmission rate) of transmitting device 40A in such a way that
the allowable interference amount M is obtained in the receiving
device 20A. Further, the allowable interference amount M in the
receiving device 20A is notified to the management server 16B.
[0072] Step 4:
[0073] The transmission power setting unit 230 of the Management
server 16B sets the transmission power of the transmitting device
40B according to the allowable interference amount M determined by
the management server 16A.
[0074] It should be noted that the entity of performing each of the
above-described steps is not particularly limited. For example, the
entity of performing each of the above steps may involve the
transmitting device 40A, the transmitting device 40B or the like,
and may not involve the management server 16A or the management
server 16B. In more detail, the transmitting device 40B may perform
the first step, the second step and the four step, and the
transmitting device 40A may perform the third step. Further, any
one of the management server 16A, the management server 16B, the
transmitting device 40A and the transmitting device 40B may perform
all of the above steps.
3. Detailed Description of Operation by Embodiment of Present
Invention
[0075] Each of the step 1 to the step 4 described above is
described in detail hereinbelow.
(3-1. Determination of Necessity of Receiving Quality Improvement
(Step 1))
[0076] The expected value calculation unit 220 of the management
server 16B determines that it is necessary to improve the receiving
quality of the receiving device 20B in the following cases, for
example.
[0077] Case A:
[0078] Case where an actual receiving quality SINR (SINR_secondary)
of the receiving device 20B is lower than a required SINR
(SINR_required,secondary) required for the receiving device 20B.
Specifically, case where the following expression 1 is
satisfied.
SINR.sub.secondary<SMIR.sub.required,secondary Expression
(1)
[0079] Case B:
[0080] Case where a plurality of receiving devices 20B exist under
management of the management server 16B, and the receiving quality
SINR (SINR_secondary) of each of the receiving devices 20B is lower
than the required SINR (SINR_required,secondary) required for each
receiving device 20B. Specifically, case where the following
expression 2 is satisfied. Note that the suffix i in the expression
2 indicates a communication link of the i-th receiving device 20B
managed by the management server 16B.
SINR.sub.secondary,(i)<SINR.sub.required,secondary,(i)
Expression (2)
[0081] Case C:
[0082] Case where an average SINR of a certain level or higher is
necessary (for example, communication of a particular application
such as video transmission in need of QoS guarantee is expected) in
a given communication range, and capacity (C_secondary) of a
network managed by the management server 16B is insufficient, and
improvement (M times) of the capacity is expected as represented in
the following expression 3.
C.sub.secondary.fwdarw.MC.sub.required,secondary Expression (3)
(3-2. Calculation of Receiving Quality Improvement Level Expected
Value Mreq (Step 2))
[0083] The expected value calculation unit 220 of the management
server 16B calculates the improvement level Mreq of the receiving
quality desired for the receiving device 20B by the following
method, for example. Then, the network communication unit 210 of
the management server 16B notifies the Mreq calculated by the
expected value calculation unit 220 to the management server
16A.
[0084] Case A: The expected value calculation unit 220 calculates
the ratio of SINR_secondary and SINR_required,secondary as Mreq as
represented in the following expression 4.
M.sub.req=SINR.sub.required,secondary/SINR.sub.secondary Expression
(4)
[0085] Case B: The expected value calculation unit 220 calculates
the receiving quality improvement level Mreq for each communication
link as represented in the following expression 5.
M.sub.req,(t)=SINR.sub.required,secondary,(i)/SINR.sub.secondary,(i)
Expression (5)
[0086] Case C: Because the relationship between the capacity C and
SINR is generally represented as the following expression 6, the
required SINR_required,secondary can be calculated according to the
expression 7. The expected value calculation unit 220 can calculate
Mreq according to the expression 4 or 5 by using the required
SINR_required,secondary.
C=log.sub.2(1+SINR) Expression (6)
SINR=2.sup.c-1 Expression (7)
(3-3. Calculation of Allowable Interference Amount M (Step 3))
[0087] The allowable interference amount calculation unit 120 of
the management server 16A first calculates the allowable
interference amount M' in the receiving device 20A by the following
method so as to achieve the Mreq notified from the management
server 16B.
[0088] Case A: When a calculation target of the allowable
interference amount is a single link
[0089] Method A-1: Calculation of the allowable interference amount
M' by transmission power control
[0090] In the case of obtaining the allowable interference amount
corresponding to Mreq by increasing the transmission power of the
transmitting device 40A, the allowable interference amount
calculation unit 120 of the management server 16A calculates the
allowable interference amount M' according to the following
expression 8, for example Note that a method of deriving the
expression 8 is described later in "5. Supplementary
Description".
M ' = SINR primary ( P rx , secondary N primary ' + M reg SINR
secondary I secondary .fwdarw. primary N secondary ' ) P rx ,
primary P rx , secondary - M req SINR primary SINR secondary I
secondary .fwdarw. primary I primary .fwdarw. secondary ,
Expression ( 8 ) ##EQU00001##
where
[0091] P.sub.rx,primary: Receiving power of the receiving device
20A (before start of power control according to the
embodiment),
[0092] P.sub.rx,secondary: Receiving power of the receiving device
20B (before start of power control according to the
embodiment),
[0093] I.sub.primary.fwdarw.secondary: Interference from the
transmitting device 40A to the receiving device 20B,
[0094] I.sub.secondary.fwdarw.primary: Interference from the
transmitting device 40B to the receiving device 20A,
[0095] N'.sub.primary: (Interference+noise) power of the receiving
device 20A, and
[0096] N'.sub.secondary: (Interference+noise) power of the
receiving device 20B.
[0097] Note that the parameters in the expression 8 can be acquired
through sensing by the receiving device 20A, the receiving device
20B, the transmitting device 40A and the transmitting device 40B,
and transmitted and received via the management server 16A Or the
management server 16B.
[0098] Method A-2: Calculation of the allowable interference amount
M' by transmission rate control
[0099] In the case of obtaining the allowable interference amount
corresponding to Mreq by decreasing the transmission rate of the
transmitting device 40A, the allowable, interference amount
calculation unit 120 of the management server 16A calculates the
allowable interference amount M' according to the following
expression 9, for example. Note that a method of deriving the
expression 9 is described later in "5. Supplementary
Description".
M ' = SINR primary { P rx , secondary N primary ' + M req SINR
secondary I secondary -> primary ( I primary -> secondary + N
secondary ' ) } P rx , primary P rx , secondary Expression ( 9 )
##EQU00002##
[0100] Case B: When a calculation target of the allowable
interference amount is a multilink
[0101] Method B-1: Calculation of the allowable interference amount
M' by transmission power control
[0102] In the case of obtaining the allowable interference amount
by increasing the transmission power of the transmitting device
40A, the allowable interference amount calculation unit 120 of the
management server 16A calculates the total allowable interference
amount M' for communication links of a plurality of receiving
devices 20A according to the following expression 10, for
example.
M ' = i = 1 N B SINR primary ( P rx , secondary , ( i ) N primary '
+ M req SINR seconddary , ( i ) I secondary , ( i ) -> primary N
secondary , ( i ) ' ) P rx , primary P rx , secondary , ( i ) - M
req SINR primary SINR secondary , ( i ) I secondary , ( i ) ->
primary I primary -> secondary , ( i ) Expression ( 10 )
##EQU00003##
[0103] Method B-2: Calculation of the allowable interference amount
M' by transmission rate control
[0104] In the case of obtaining the allowable interference amount
by decreasing the transmission rate of the transmitting device 40A,
the allowable interference amount calculation unit 120 of the
management server 16A calculates the total allowable interference
amount M' for communication links of a plurality of receiving
devices 20A according to the following expression 11, for
example.
M ' = i = 1 N B SINR primary { P rx , secondary , ( i ) N primary '
+ M req SINR secondary , ( i ) I secondary , ( i ) -> primary (
I primary -> secondary , ( i ) + N secondary , ( i ) ' ) } P rx
, primary P rx , secondary , ( i ) Expression ( 11 )
##EQU00004##
[0105] After the allowable interference amount calculation unit 120
of the management server 16A calculates the ideal allowable
interference amount M' in the receiving device 20A for achieving
Mreq by the above method, it determines an allowable interference
amount M to be actually applied, with the ideal allowable
interference amount M' as an upper limit This is because the ease
where it is difficult to obtain the ideal allowable interference
amount M' is assumed according to circumstances.
[0106] For example, when the transmitting device 40A already
transmits a radio signal with the maximum transmission power or
with a power close to the maximum transmission power, it is unable
to sufficiently increase the transmission power and obtain the
ideal allowable interference amount M'. An alternative case is when
certain QoS guarantee is expected for the communication link of the
receiving device 20A, and the lower limit of a rate or latency is
restricted.
[0107] In such cases, the allowable interference amount calculation
unit 120 of the management server 16A determines the allowable
interference amount M to be actually applied in a best effort
manner, with the ideal allowable interference amount M' as the
upper limit. Note that the allowable interference amount
calculation unit 120 may determine the allowable interference
amount M which is closer to the ideal allowable interference amount
M' by combining the increase in transmission power and the decrease
in transmission rate. For example, when the allowable interference
amount obtained by the increase in transmission power is M1, and
the allowable interference amount obtained by the decrease in
transmission rate is M2, the allowable interference amount M=M1*M2
can be obtained by combining the increase in transmission power and
the decrease in transmission rate.
[0108] Then, the transmission parameter setting unit 130 of the
management server 16A changes the transmission parameter of the
transmitting device 40A in order to obtain the allowable
interference amount M determined by the allowable interference
amount calculation unit 120. For example, the transmission
parameter setting unit 130 may change the transmission power of the
transmitting device 40A to M times. Alternatively, the transmission
parameter setting unit 130 may change the transmission rate of the
transmitting device 40A so that the current transmission power of
the transmitting device 40A becomes M times the transmission power
necessary to satisfy the required SINR of the transmission rate
after change. Further, the transmission parameter setting unit 130
may increase the transmission power and decrease the transmission
rate so that the product of multiplying the allowable interference
amount M1 obtained by the increase in transmission power by the
allowable interference amount M2 obtained by the decrease in
transmission rate becomes M.
[0109] Further, the network communication unit 110 of the
management server 16A notifies the allowable interference amount M
determined by the allowable interference amount calculation unit
120 to the management server 16B.
(3-4 Control of Transmission Power Based on Allowable Interference
Amount M (Step 4))
[0110] The transmission power setting unit 230 of the management
server 16B increases the transmission power of the transmitting
device 40B within the range that the amount of interference from
the transmitting device 40B to the transmitting device 40A is the
allowable interference amount M or less, based on the allowable
interference amount M notified from the management server 16A.
[0111] (Setting of Transmission Power for Single Link)
[0112] Specifically, the transmission power setting unit 230
calculates a transmission power P'tx,secondary after update of the
transmitting device 40B as follows.
P tx , secondary ' = M req ' P tx , secondary = ( P rx , primary M
- SINR primary N primary ' ) P tx , secondary SINR primary I second
-> primary , Expression ( 12 ) where M req ' = P rx , primary M
- SINR primary N primary ' SINR primary I secondary -> primary
##EQU00005##
[0113] (Setting of Transmission Power for Multilink)
[0114] Further, when the allowable interference amount M is given,
the transmission power setting unit 230 can calculate the
transmission power of each communication link evenly as represented
in the following expression 13.
P tx , secondary , ( i ) ' = ( P rx , primary M - SINR primary N
primary ' ) P tx , secondary SINR primary I secondary -> primary
1 N B Expression ( 13 ) ##EQU00006##
[0115] Alternatively, the transmission power setting unit 230 may
calculate the transmission power of each communication link by
assigning weights according to the required allowable interference
amount (Mreq(i)) of each communication link as represented in the
following expression 14.
P tx , secondary , ( i ) ' = ( P rx , primary M - SINR primary N
primary ' ) P tx , secondary SINR primary I secondary -> primary
M req , ( i ) j = 0 N B M req , ( j ) Expression ( 14 )
##EQU00007##
4. Advantageous Effects of Embodiment of Present Invention
Indicated By Numerical Analysis Results
[0116] Since numerical analysis of the increasing amount of the
average communication capacity between the transmitting device 40A
and the receiving device 20A and between the transmitting device
40B and the receiving device 20B which is obtained by the
embodiment of the present invention is performed, results of the
numerical analysis are described hereinbelow. In the numerical
analysis, it is assumed that the distance between the transmitting
device 40A and the transmitting device 40B is 300 m, the receiving
devices 20A and 20B are located within the range of 50 m from the
transmitting device 40B, and M=M'.
[0117] FIG 6 is an explanatory view showing a relationship between
the receiving quality improvement level Mreq desired for the second
reviving device 20B and the allowable interference amount M' in the
receiving device 20A. Referring to FIG 6, it is verified that M'
increases exponentially with respect to Mreq with use of any of
transmission power control (TPC) and transmission rate control
(RC). Particularly, because M' increases abruptly when Mreq is 40
dB or higher, it is considered that the control of M' in this
region is effective.
[0118] Further, it is found that the increasing amount of M' with
respect to the same Mreq is greater when performing the
transmission power control than when performing the transmission
rate control. This is because, when performing the transmission
power control, both of the amount of interference from the
transmitting device 40A to the receiving device 20B and the amount
of interference from the transmitting device 40B to the receiving
device 20A increase, and it is thus necessary to further increase
the transmission power of the transmitting device 40A. In actual
operation, there is the upper limit of the transmission power of
each transmitting device 40, and the management server 16A controls
the value of M within the range not exceeding the upper limit.
[0119] FIG 7 is an explanatory view showing a relationship between
the allowable interference amount M' and the average communication
capacity in the case of obtaining the allowable interference amount
M' by transmission power control. Referring to FIG. 7, in the case
of obtaining the allowable interference amount M' by transmission
power control, the communication capacity (TPC, PS) between the
transmitting device 40A and the receiving device 20A is controlled
to be constant with respect to M'. Therefore, it is shown that the
increment of the communication capacity (TPC, SS) between the
transmitting device 40B and the receiving device 20B serves as the
increment of the total communication capacity.
[0120] Further, referring to FIG 7, the communication capacity
between the transmitting device 40B and the receiving device 20B
tends to be saturated when M' reaches approximately 5 dB.
Specifically, it is considered that an unlimited increase in M'
does not contribute to the increase in the total communication
capacity. Thus, the allowable interference amount calculation unit
120 of the management server 16A may determine the value of the
allowable interference amount M within the range that does not
exceed a predetermined upper limit (e.g. 5 dB).
[0121] FIG 8 is an explanatory view showing a relationship between
the allowable interference amount M' and the average communication
capacity in the case of obtaining the allowable interference amount
M' by transmission rate control. Referring to FIG 8, in the case of
obtaining the allowable interference amount M' by transmission rate
control, the transmission power of the transmitting device 40A is
kept constant, and therefore the communication capacity between the
transmitting device 40A and the receiving device 20A tends to
decrease with an increase in M'. However, because the increment of
the communication capacity between the transmitting device 40B and
the receiving device 20B is greater than the decrement of the
communication capacity between the transmitting device 40A and the
receiving device 20A, the total communication capacity
increases.
[0122] Further, just like the case of transmission power control,
the communication capacity between the transmitting device 40B and
the receiving device 20B tends to be saturated when M' reaches
approximately 5 dB. Specifically, it is considered that an
unlimited increase in M' does not contribute to the increase in the
total communication capacity. Thus, the allowable interference
amount calculation unit 120 of the management server 16A may
determine the value of the allowable interference amount M within
the range that does not exceed a predetermined upper limit (e.g. 5
dB) in the case of obtaining the allowable interference amount by
transmission rate control as well.
5. Supplementary Description
[0123] Hereinafter, processes of deriving the expression 8 and the
expression 9 for calculating the allowable interference amount M'
on the basis of Mreq are described.
[0124] Derivation of Expression 8
[0125] One example of a method of calculating an allowable
interference amount M' of the receiving device 20A and an actual
transmission power increasing amount M'req of the transmitting
device 40B from Mreq required by the management server 16B is to
solve the system of linear equations with two unknowns by SINR
condition of the receiving device 20A and SINR condition of the
receiving device 20B.
[0126] First, as the SINR condition of the receiving device 20A,
the following expression 15 can be used.
SINR primary = M ' P rx , primary M req ' I secondary -> primary
+ N primary ' Expression ( 15 ) ##EQU00008##
[0127] Further, as the SINR condition of the receiving device 20B,
the following expression 16 can be used.
SINR secondary , req = M req SINR secondary = M req ' P rx ,
secondary M ' I primary -> secondary + N secondary ' Expression
( 16 ) ##EQU00009##
[0128] Summarizing the expression 15 and the expression 16 yields
the simultaneous equations with respect to M' and M'req.
{ P rx , primary M ' - SINR primary I secondary -> primary M req
' = SINR primary N primary ' SINR secondary M req I primary ->
secondary M ' - P rx , secondary M req ' = - SINR secondary M req N
secondary ' Expression ( 17 ) ##EQU00010##
[0129] Solving the above expression 17 with respect to M' yields
the expression 8, and solving the expression 17 with respect to
M'req after M is determined in the above-described step 3 yields
the expression 12.
[0130] Note that the parameters in the expressions 15 to 17, the
expression 8 and the expression 12 can be also represented as
follows.
P rx , primary = L primary -> primary P tx , primary P rx ,
secondary = L secondary -> secondary P tx , secondary I primary
-> secondary = L primary -> secondary P tx , primary I
secondary -> primary = L secondary -> primary P tx ,
secondary SINR primary = P rx , primary I secondary -> primary +
N primary ' SINR secondary = P rx , secondary I primary ->
secondary + N secondary ' , Expression ( 18 ) ##EQU00011##
where
[0131] L.sub.primary.fwdarw.primary: Path loss of a communication
link between the transmitting device 40A and the receiving device
20A,
[0132] L.sub.secondary.fwdarw.secondary: Path loss of a
communication link between the transmitting device 40B and the
receiving device 20B,
[0133] L.sub.primary.fwdarw.secondary: Path loss of an interference
link between the transmitting device 40A and the receiving device
20B,
[0134] L.sub.secondary.fwdarw.primary: Path loss of an interference
link between the transmitting device 40B and the receiving device
20A,
[0135] P.sub.tx,secondary: Transmission power before change of the
transmitting device 40A, and
[0136] P.sub.tx,secondary: Transmission power before change of the
transmitting device 40B.
[0137] By substituting the respective parameters represented in the
above expression 18 into the expression 8 and the expression 12. M'
can be represented by the following expression 19, and M'req can be
represented by the following expression 20.
M ' = ( L primary -> secondary P tx , primary + N secondary ' )
N primary ' + M req L secondary -> primary P tx , secondary N
secondary ' ( L secondary -> primary P tx , secondary + N
primary ' ) ( L primary -> secondary P tx , primary + N
secondary ' ) - M req P tx , primary P tx , secondary L secondary
-> primary L primary -> secondary Expression ( 19 ) M req ' =
M ( L secondary -> primary P tx , secondary + N primary ' ) - N
primary ' L secondary -> primary P tx , secondary Expression (
20 ) ##EQU00012##
[0138] Derivation of Expression 9
[0139] In the case of obtaining the allowable interference amount
M' of the receiving device 20A and the actual transmission power
increasing amount M'req of the transmitting device 40B by
controlling the transmission rate also, M' and M'req can be
obtained by solving the system of linear equations with two
unknowns by SINR condition of the receiving device 20A and SINR
condition of the receiving device 20B.
[0140] First, as the SINR condition of the receiving device 20A,
the following expression 21 can be used.
SINR primary , req = 1 M ' SINR primary = P rx , primary M req ' I
secondary -> primary + N primary ' Expression ( 21 )
##EQU00013##
[0141] Further, as the SINR condition of the receiving device 20B,
the following expression 22 can be used.
SINR secondary , req = M req SINR secondary = M req ' P rx ,
secondary I primary -> secondary + N secondary ' Expression ( 22
) ##EQU00014##
[0142] Summarizing the expression 21 and the expression 22 yields
the following system of linear equations with two unknowns shown
below.
{ P rx , primary M ' - SINR primary I secondary -> primary M req
' = SINR primary N primary ' P rx , secondary M req ' = M req SINR
secondary ( I primary -> secondary + N secondary ' ) Expression
( 23 ) ##EQU00015##
[0143] Solving the above expression 23 with respect to M' yields
the expression 9, and solving the expression 23 with respect to
M'req after M is determined in the above-described step 3 yields
the expression 12.
[0144] Further, by substituting the respective parameters
represented in the above expression 18 into the expression 9 and
the expression 12, M' can be represented by the following
expression 24, and M'req can be represented by the following
expression 25.
M ' = M req L secondary -> primary P tx , secondary + N primary
' L secondary -> primary N tx , secondary + N primary '
Expression ( 24 ) M req ' = M ( L secondary -> primary P tx ,
secondary + N primary ' ) - N primary ' L secondary -> primary P
tx , secondary Expression ( 25 ) ##EQU00016##
6 Summary
[0145] As described above, according to the embodiment of the
present invention, the allowable interference amount M in the
receiving device 20A is obtained by increasing the transmission
power of the transmitting device 40A or decreasing the transmission
rate of the transmitting device 40A. Then, the transmitting device
40B sets the transmission power in the range that interference on
the receiving device 20A does not exceed the allowable interference
amount M. In such a configuration, as described above with
reference to FIGS. 7 and 8, it is possible to effectively increase
the communication capacity of the entire network.
[0146] Although a preferred embodiment of the present invention is
described in detail above with reference to the appended drawings,
the present invention is not limited thereto. It should be
understood by those skilled in the art that various modifications,
combinations, sub-combinations and alterations may occur depending
on design requirements and other factors insofar as they are within
the scope of the appended claims or the equivalents thereof.
[0147] Further, it is possible to create a computer program that
causes hardware such as a CPU, ROM and RAM incorporated in the
management server 16 to function equally to the respective elements
of the management server 16 described above. Further, a memory
medium that stores such a computer program may be provided.
[0148] It should be noted that the term "secondary usage" in this
specification typically means utilization of an additional or
alternative communication service (a second communication service)
using a part or whole of a spectrum assigned to a first
communication service. In this context about the meaning of the
term "secondary usage", the first communication service and the
second communication service may be services of different types or
the same type. The services of different types may be selected from
services such as digital TV broadcasting service, satellite
communication service, mobile communication service, wireless LAN
access service, P2P (Peer To Peer) connection service and the
like.
[0149] On the other hand, services of the same type may contain,
for example, a relationship between a service using the macro cell
provided by a communication carrier and a service using the
femtocell operated by users or MVNO (Mobile Virtual Network
Operator) in a mobile communication service. Additionally, services
of the same type may contain, for example, a relationship between a
service provided by a macro cell base station and a service
provided by a relay station (relay node) to cover a spectrum hole
in a communication service conforming to LTE-A (Long Term
Evolution-Advanced).
[0150] The disclosed concept is applicable in various different
types of communication systems. For example, in LTE-A, a control
area (PDCCH: Physical Downlink Control Channel) and data area
(PDSCH: Physical Downlink Shared Channel) are separately assigned
in a communication area. In this configuration, there are generally
two ways to solve the problem of interference between different
types of communication nodes.
[0151] A first solution is to reduce interference in both of the
control area (PDCCH) and the data area (PDSCH). This is a basic way
to reduce interference occurring between different types of
communication nodes.
[0152] A second solution is to reduce interference only in the
control area (PDCCH). This solution is based on the fact that the
scheduler in the node assigns data resources for a particular data
area. Here, the scheduler, which is normally implemented in a MAC
function of a base station, is the component that assigns the data
resources. In other words, with regard to the resource that
interference between different types of node's is estimated to
occur, interference can be avoided by assigning resources only to
one of the nodes. This can be realized by collaboration of
scheduler& running on the different types of nodes. On the
other hand, with regard to the control area (PDCCH), since the
scheduler can not change the resource allocation, it is important
to reduce interference in the control area from the beginning.
[0153] The configuration disclosed herein can be applied to both of
the control area and the data area as well as only to the control
area.
[0154] Further, the second communication service may be a service
utilizing a plurality of fragmentary frequency bands aggregated
using spectrum aggregation technology. Furthermore, the second
communication service may be a supplementary communication service
provided by femtocells, relay stations or small-to-medium-sized
base stations providing smaller service areas than a macro cell
base station, which are located within the service area provided by
the macro cell base station. The subject matter of each embodiment
of the present invention described in this specification is widely
applicable to every type of mode of such secondary usages.
REFERENCE SIGNS LIST
[0155] 16, 16A, 16B Management server
[0156] 20, 20A, 20B Receiving device
[0157] 40, 40A, 40B Transmitting device
[0158] 110, 210 Network communication unit
[0159] 120 Allowable interference amount calculation unit
[0160] 130 Transmission parameter setting unit
[0161] 140 Communication control unit
[0162] 220 Expected value calculation unit
[0163] 230 Transmission power setting unit
[0164] 240 Communication control unit
* * * * *