WO2013108315A1 - 無線通信システム、送信電力制御装置、基地局装置、パラメータ供給装置、及び送信電力制御方法 - Google Patents
無線通信システム、送信電力制御装置、基地局装置、パラメータ供給装置、及び送信電力制御方法 Download PDFInfo
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- WO2013108315A1 WO2013108315A1 PCT/JP2012/006935 JP2012006935W WO2013108315A1 WO 2013108315 A1 WO2013108315 A1 WO 2013108315A1 JP 2012006935 W JP2012006935 W JP 2012006935W WO 2013108315 A1 WO2013108315 A1 WO 2013108315A1
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- transmission power
- uplink
- power control
- base station
- cell
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/06—TPC algorithms
- H04W52/14—Separate analysis of uplink or downlink
- H04W52/146—Uplink power control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
- H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
- H04W52/244—Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
- H04W16/32—Hierarchical cell structures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/04—Large scale networks; Deep hierarchical networks
- H04W84/042—Public Land Mobile systems, e.g. cellular systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/04—Large scale networks; Deep hierarchical networks
- H04W84/042—Public Land Mobile systems, e.g. cellular systems
- H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B
Definitions
- the present invention relates to uplink transmission power control in a wireless communication system.
- the femtocell base station not only accommodates the above-mentioned high-demand traffic, but can also be installed in places where radio waves do not reach, such as high floors of buildings and underground malls, so it is also attracting attention as a means of expanding coverage (communication area that satisfies the required quality) Has been.
- Femtocell base stations are used in 3GPP (3rd Generation Partnership Project) W-CDMA and E-UTRA mobile phone wireless communication standards, and IEEE 802.16m wireless MAN (Wireless Metropolitan Area Network) wireless communication standards To be considered.
- W-CDMA Wideband Code Division Multiple Access
- a femtocell base station is called Home NodeB (HNB).
- HNB Wideband Code Division Multiple Access
- E-UTRA Evolved Universal Terrestrial Radio Access
- LTE Long Term Evolution
- LTE Long Term Evolution
- the femtocell base station is connected to an upper network (e.g. a core network of an e.g. carrier) directly or via a femto GW (gateway).
- the Femto GW is called Home NodeB Gateway in the W-CDMA standard and Home eNodeB Gateway in the E-UTRA standard.
- a mobile station that communicates by connecting to a femtocell base station is called a “femtocell mobile station”, and a mobile station that communicates by connecting to a macro base station is called a “macro mobile station”. .
- femtocell base stations When femtocell base stations are used in W-CDMA, data transmission / reception using dedicated channels with transmission power control in uplink (uplink) and downlink (downlink), and data using downlink shared channels Transmission / reception is performed.
- a femtocell base station When a femtocell base station is used in E-UTRA, the radio frequency band and time are divided into a plurality of resource blocks (PRBs), and a scheduler provided in the base station assigns PRBs. And data transmission / reception using the assigned PRB is performed.
- PRBs resource blocks
- OFDMA Orthogonal Frequency Division Multiple Multiple Access
- CSG ClosedCloseSubscriber Group
- CSG cell a cell to which only the mobile station belonging to the CSG is allowed.
- CSG when a mobile station is located in a femtocell, a mobile station registered in the femtocell base station can connect to the network via the femtocell base station.
- a mobile station that is not registered in the femtocell base station cannot be connected to the network via the femtocell base station, or communication with the femtocell base station is restricted compared to a registered mobile station.
- uplink interference means interference that the uplink reception of the base station (in other words, uplink transmission of the mobile station) suffers from the uplink transmission of the mobile station of another cell. That is, in this interference scenario, the interference that the uplink transmission of the femtocell mobile station has on the uplink reception of the macro base station (in other words, the uplink transmission of the macro mobile station) is targeted.
- This interference scenario is particularly problematic when the upstream frequency bands of the femto cell and the macro cell are the same, the femto cell is a CSG cell, and the femto cell base station is located near the macro base station.
- the transmission power of the macro mobile station located near the femtocell base station is relatively small, the interference of the uplink transmission of the femtocell mobile station on the uplink transmission of the macro mobile station becomes serious.
- Non-Patent Documents 1 and 2 and Patent Document 1 disclose techniques for suppressing uplink interference from a femto cell to a macro cell.
- Non-Patent Documents 1 and 2 disclose that the uplink transmission power of the femtocell is controlled in consideration of the propagation loss between the femtocell and the macrocell. Specifically, Non-Patent Document 1 measures the propagation loss between the femtocell base station and the macro base station, and the transmission power control is performed so that the uplink transmission power of the femtocell mobile station is smaller as the propagation loss is smaller. Is disclosed.
- Non-Patent Document 2 measures the propagation loss between the femtocell mobile station and the macro base station, and performs transmission power control so that the uplink transmission power of the femtocell mobile station is smaller as the propagation loss is smaller.
- the transmission power control includes adjustment of the uplink target reception power in the femtocell base station and adjustment of the maximum uplink transmission power in the femtocell mobile station.
- Patent document 1 pays attention to the fact that the number of femtocell base stations arranged in a macro cell changes, and from a plurality of femtocells arranged in a macrocell to a macrocell regardless of the number of femtocell base stations in the macrocell.
- the purpose is to suppress uplink interference.
- Patent Document 1 discloses the following technique. That is, the number of femtocell base stations having a femtocell mobile station in communication among a plurality of femtocell base stations arranged in the macro cell is obtained.
- the upper limit of the uplink interference allowed per femtocell base station is calculated. Then, the maximum uplink transmission power of the femtocell mobile station is set using the calculated upper limit value of the uplink interference amount and the propagation loss between the femtocell mobile station and the macro base station.
- Patent Document 1 obtains the number of femtocell base stations having femtocell mobile stations that are arranged in a macro cell and is in communication, and uses this number to determine the uplink of the femtocell mobile station. Control transmission power.
- Patent Document 1 only considers the number of femtocell base stations having a femtocell mobile station in communication, and does not sufficiently consider the use status of uplink resources in the femtocell base station.
- Non-Patent Documents 1 and 2 do not disclose any solution for this problem.
- the uplink resources actually used in a plurality of femtocells arranged in the macrocell are small. If the uplink resource usage of the plurality of femtocells arranged in the macro cell is small, the total uplink interference amount experienced by the macro base station may be small. Alternatively, the macro base station may avoid the use of uplink resources with large uplink interference from the femtocell and may select and use uplink resources with small uplink interference. If the method of Patent Document 1 is used in these cases, the transmission power of the femtocell mobile station is excessively reduced, and the uplink communication quality of the femtocell may be unnecessarily lowered.
- Patent Document 1 is not limited to an environment using a macro cell and a femto cell, and can generally occur in an environment in which a plurality of small cells overlap with a large cell.
- Such an environment is called a hierarchical cell structure (Hierarchical Cell Structure (HCS)) or Heterogeneous Network (HetNet).
- HCS Hierarchical Cell Structure
- HetNet Heterogeneous Network
- the present invention has been made based on the above-mentioned knowledge obtained by the inventors. That is, according to the present invention, in an environment in which a plurality of small cells overlap with a large cell, the uplink communication quality of the small cell is excessively deteriorated due to suppression of uplink interference to the large cell. It is an object of the present invention to provide a wireless communication system, a transmission power control device, a base station device, a parameter supply device, a transmission power control method, and a program that can contribute to prevention of noise.
- the first aspect of the present invention includes a wireless communication system.
- the wireless communication system includes a first base station, a plurality of second base stations, and a control device.
- the first base station forms a first cell.
- Each of the plurality of second base stations forms a second cell that is smaller than the first cell and at least partially overlaps the first cell.
- the control device uses a resource parameter that increases or decreases according to a sum of uplink resource usage amounts or a sum of uplink resource usage rates of a plurality of second cells formed by the plurality of second base stations.
- uplink transmission power control is performed on target cells included in the plurality of second cells.
- the second aspect of the present invention includes a transmission power control device used in a wireless communication system.
- the wireless communication system includes: a first base station forming a first cell; and a plurality of second cells each of which forms a second cell that is smaller than the first cell and at least partially overlaps the first cell Includes a second base station.
- the transmission power control apparatus sets a resource parameter that increases or decreases according to a sum of uplink resource usage amounts or a sum of uplink resource usage rates of a plurality of second cells formed by the plurality of second base stations. And configured to perform uplink transmission power control for target cells included in the plurality of second cells.
- the third aspect of the present invention includes a base station apparatus.
- the base station apparatus includes the above-described transmission power control apparatus according to the second aspect of the present invention and a radio communication unit capable of communicating with mobile stations belonging to the target cell.
- the 4th aspect of this invention contains the parameter supply apparatus used with a radio
- the wireless communication system includes: a first base station that forms a first cell; and a plurality of second cells each of which forms a second cell that is smaller than the first cell and at least partially overlaps the first cell And a control device that performs uplink transmission power control on a target cell included in a plurality of second cells formed by the second base station and the plurality of second base stations.
- the parameter supply device is configured to increase or decrease a resource parameter according to a sum of uplink resource usage amounts or a sum of uplink resource usage rates of the plurality of second cells for the uplink transmission power control. It is configured to supply to.
- the fifth aspect of the present invention includes a transmission power control method used in a wireless communication system.
- the wireless communication system includes: a first base station forming a first cell; and a plurality of second cells each of which forms a second cell that is smaller than the first cell and at least partially overlaps the first cell Includes a second base station.
- a resource parameter that increases or decreases according to a sum of uplink resource usage amounts or a sum of uplink resource usage rates of a plurality of second cells formed by the plurality of second base stations is set. And performing uplink transmission power control on target cells included in the plurality of second cells.
- the sixth aspect of the present invention includes a program for causing a computer to perform the transmission power control method according to the fifth aspect of the present invention described above.
- the uplink communication quality of the small cell is reduced due to the suppression of uplink interference to the large cell. It is possible to provide a wireless communication system, a transmission power control device, a base station device, a parameter supply device, a transmission power control method, and a program that can contribute to prevention of excessive reduction.
- FIG. 4 is a block diagram showing a configuration example of a transmission power control apparatus shown in FIGS.
- FIG. 4 is a block diagram showing a configuration example of a parameter supply device shown in FIGS. It is a flowchart which shows the specific example of the uplink transmission power control by a transmission power control apparatus.
- FIG. 1 shows a network configuration example of a radio communication system according to Embodiment 1 of the present invention.
- the wireless communication system according to the present embodiment includes a plurality of femtocell base stations 1 and macro base stations 3.
- Each femtocell base station 1 forms a femtocell 5 and performs wireless communication with the femtocell mobile station 2.
- the macro base station 3 forms a macro cell 6 and performs wireless communication with the macro mobile station 4.
- Each femtocell 5 at least partially overlaps the macrocell 6.
- the plurality of femtocell base stations 1 includes two femtocell base stations 1-1 and 1-2. Femtocell base stations 1-1 and 1-2 form femtocells 5-1 and 5-2, respectively.
- the femtocells 5-1 and 5-2 at least partially overlap the macrocell 6.
- the femtocell base station 1-1 performs radio communication with the femtocell mobile station 2-1 in the femtocell 5-1.
- the femtocell base station 1-2 performs radio communication with the femtocell mobile station 2-2 in the femtocell 5-2.
- the femtocells 5-1 and 5-2 that overlap with the macrocell 6 exert uplink interference on the macrocell 6. That is, the uplink transmissions of the femtocell mobile stations 2-1 and 2-2 interfere with uplink reception of the macro base station 3 (in other words, uplink transmission of the macro mobile station 4).
- the transmission power control apparatus 10 performs uplink transmission power control (uplink TPC (Transmission Power Control)) of the femtocell 5.
- uplink TPC Transmission Power Control
- the transmission power control apparatus 10 may be configured to control the uplink transmission power of a plurality of femtocells 5 (for example, the cells 5-1 and 5-2). Moreover, in order to perform uplink transmission power control of the plurality of femtocells 5, a separate transmission power control apparatus 10 may be arranged for each femtocell 5.
- Transmission power control unit 10 similarly to the method described in Non-Patent Documents 1 and 2, taking into consideration the propagation loss L M between the femtocell 5-1 and the macrocell 6, be subjected to uplink transmission power control Good.
- the propagation loss L M may be used the propagation loss between the femto cell mobile station 2-1 and the macro base station 3, using a propagation loss between the femto cell base station 1-1 and the macro base station 3 May be.
- the transmission power controller 10 may perform transmit power control to reduce the transmission power of the femtocell mobile station 2-1 as the propagation loss L M is small.
- the transmission power of the femtocell mobile station 2-1 may be adjusted according to the uplink transmission power control method defined by W-CDMA, E-UTRA, IEEE 802.16m, and the like.
- the transmission power control apparatus 10 may adjust the uplink target received power PO_H in the femtocell base station 1-1.
- the femtocell base station 1-1 controls the transmission power of the femtocell mobile station 2-1 so that the received power of the uplink signal from the femtocell mobile station 2-1 approaches the uplink target received power PO_H .
- the femtocell base station 1-1 may notify the uplink target received power PO_H to the femtocell mobile station 2-1. Further, the femtocell base station 1-1 may instruct the femtocell mobile station 2-1 to increase or decrease the transmission power so as to approach the uplink target reception power PO_H by so-called closed loop transmission power control. Further, the transmission power control apparatus 10 may adjust the maximum transmission power P MAX, H of the femtocell mobile station 2-1 instead of the uplink target reception power PO_H .
- the transmission power control apparatus 10 uses the resource parameter R1 in the uplink transmission power control of the femtocell 5-1.
- the resource parameter R1 corresponds to the sum of uplink resource usage or the sum of uplink resource usage rates of a plurality of femtocells 5 (for example, the cells 5-1 and 5-2) arranged at least partially overlapping the macro cell 6. Parameter to increase or decrease.
- the uplink resource is a radio resource used for transmission of an uplink signal in the femtocell 5.
- Uplink resources are generally defined by frequency, time, spreading code, or any combination thereof.
- the unit of the uplink resource is a physical resource block (PRB) divided by frequency and time.
- PRB physical resource block
- OFDMA Orthogonal Frequency-Division-Multiple.Access
- the unit of uplink resource is an OFDM subcarrier.
- CDMA Code Division Multiple Access
- the unit of uplink resources is a spreading code (i.e..channelization code) or a physical channel distinguished by a spreading code.
- the transmission power control apparatus 10 increases the uplink transmission power of the femtocell mobile station 2-1 belonging to the target femtocell 5-1 as the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5 increases.
- the uplink transmission power control is performed so as to decrease.
- the resource parameter R1 is transmitted in the uplink transmission of the femtocell mobile station 2-1 belonging to the target femtocell 5-1, as the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5 increases.
- the power is determined to decrease.
- the transmission power control apparatus 10 may decrease the uplink target received power PO_H as the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5 increases. Further, the transmission power control apparatus 10 decreases the maximum transmission power P MAX, H of the femtocell mobile station 2-1 as the sum of the uplink resource usage amounts or the sum of the uplink resource usage rates of the plurality of femtocells 5 increases. You may let them.
- the parameter supply device 20 receives the uplink resource usage (uplink Resource ⁇ Usage Amount (RUA)) or the uplink resource usage rate (uplink Resource Usage Rate (RUR)) of each femtocell 5 from each of the plurality of femtocells 5. . Then, the parameter supply device 20 generates a resource parameter R1 by aggregating a plurality of received uplink resource usages or usage rates, and uses the generated parameter R1 for uplink transmission power control of the target femtocell 5-1. To the transmission power control apparatus 10. Note that the parameter supply device 20 may supply the resource parameter R1 to each of the plurality of transmission power control devices 10 for uplink transmission power control of the plurality of femtocells 5.
- RUA uplink Resource ⁇ Usage Amount
- RUR uplink Resource Usage Rate
- the resource parameter R1 includes a value that increases or decreases according to the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5.
- the resource parameter R1 may be defined as a function that monotonously increases or monotonously decreases with respect to the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5.
- the resource parameter R1 may include a parameter based on the sum of uplink resource usage rates of the plurality of femtocells 5. More specifically, the resource parameter R1 may include at least one of the following (a) to (d).
- A Sum of uplink resource usage rates of multiple femtocells 5
- b Average value of sum of uplink resource usage rates of multiple femtocells 5 and number of femtocells 5
- c Multiple femtocells 5 Sum of uplink resource usage amount
- d Average value of sum of uplink resource usage amounts of a plurality of femtocells 5 and the number of femtocells 5
- the transmission power control apparatus 10 has a plurality of femtocells arranged at least partially overlapping the macrocell 6 for uplink transmission power control in the target femtocell 5-1.
- a resource parameter R1 that increases or decreases according to the sum of the uplink resource usage or the usage rate of 5 (for example, the cells 5-1 and 5-2) is used.
- uplink transmission power control in the target femtocell 5-1 is performed in consideration of the uplink resource usage of the entire plurality of femtocells 5 (for example, the cells 5-1 and 5-2). Specifically, the transmission power control apparatus 10 detects the femtocell mobile station 2-1 belonging to the target femtocell 5-1 as the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5 increases. Uplink transmission power control may be performed so that the uplink transmission power of the network decreases.
- the uplink resources actually used in the plurality of femtocells 5 arranged in the macrocell 6 are small. Is done. If the uplink resource usage of the plurality of femtocells 5 arranged in the macro cell 6 is small, the total uplink interference amount experienced by the macro base station may be small. Alternatively, the macro base station 3 may be able to select and use an uplink resource with small uplink interference from the femtocell.
- the uplink transmission power control in the present embodiment considers the uplink resource usage of the plurality of femtocells 5, and therefore the uplink communication quality of the femtocell 5-1 is reduced due to the suppression of uplink interference to the macrocell 6. It can prevent falling too much.
- the arrangement of the transmission power control device 10 and the parameter supply device 20 is appropriately determined based on the design concept of the network architecture or according to the wireless communication standard.
- the transmission power control apparatus 10 may be disposed integrally with the femtocell base station 1.
- the parameter supply device 20 may be arranged in the management server 151 that can communicate with the plurality of femtocell base stations 1 via the upper network 150.
- the upper network 150 includes, for example, a radio access network and a core network of a communication carrier, an IP (Internet Protocol) leased line, and the public Internet.
- both the transmission power control device 10 and the parameter supply device 20 may be arranged integrally with the femtocell base station 1. Further, the functions of the transmission power control apparatus 10 may be separately arranged in the wireless communication system. For example, the function of uplink transmission power control by the transmission power control apparatus 10 may be realized by the femtocell mobile station 2, the femtocell base station 1, and a control apparatus (eg RNC (Radio Network Controller)) in the upper network 150. Good.
- RNC Radio Network Controller
- the transmission power control apparatus 10 may be arranged in the femtocell mobile station 2-1.
- the femtocell mobile station 2-1 may receive the resource parameter R1 from the femtocell base station 1-1 or the management server 151, and correct its own uplink transmission power using the parameter R1.
- FIG. 4 is a block diagram illustrating a configuration example of the transmission power control apparatus 10.
- the transmission power control apparatus 10 includes an uplink transmission power control unit 11.
- the uplink transmission power control unit 11 receives the resource parameter R1 from the parameter supply device 20. Then, the uplink transmission power control unit 11 performs uplink transmission power control of the femtocell mobile station 2 belonging to the target femtocell 5 using the parameter R1.
- the uplink transmission power control includes, for example, adjustment of the uplink target reception power PO_H in the femtocell base station 1, or adjustment of the maximum transmission power PMAX , H of the femtocell mobile station 2-1.
- FIG. 5 is a block diagram illustrating a configuration example of the parameter supply device 20.
- the parameter supply device 20 includes a resource / parameter generation unit 21 and a resource / parameter transmission unit 22.
- the resource parameter generation unit 21 receives the uplink resource usage or usage rate of each of the plurality of femtocells 5 and generates the resource parameter R1 by aggregating the plurality of uplink resource usage or usage rates.
- a plurality of uplink resource usage or usage rates are devices that manage uplink radio resources, specifically, a plurality of femtocell base stations 1 (for example, base stations 1-1 and 1-2) or a control device such as an RNC, Are sent to the resource / parameter generating unit 21.
- the resource parameter transmission unit 22 supplies the generated resource parameter R1 to the transmission power control apparatus 10.
- FIG. 6 is a flowchart showing a specific example of uplink transmission power control by the transmission power control apparatus 10.
- the transmission power control apparatus 10 receives the resource parameter R ⁇ b> 1 from the parameter supply apparatus 20.
- the transmission power control apparatus 10 performs uplink transmission power control on the target femtocell 5 using the resource parameter R1.
- FIG. 7 is a flowchart showing the operation of the parameter supply device 20.
- the parameter supply device 20 receives the uplink resource usage or usage rate of each of the plurality of femtocells 5.
- the parameter supply device 20 generates a resource parameter R ⁇ b> 1 by aggregating a plurality of uplink resource usages or usage rates for the plurality of femtocells 5.
- the parameter supply device 20 transmits the resource parameter R ⁇ b> 1 to the transmission power control device 10.
- the total number of the plurality of femtocell base stations 1 including the femtocell base station 1-1 to be controlled is N.
- an estimated value ⁇ of SINR (Signal to Interference plus Noise Ratio) per uplink PRB transmitted by the macro mobile station 4 when it is assumed that the macro mobile station 4 is in the vicinity of the femtocell base station 1-1 to be controlled is defined [dB]. Assume that ⁇ must be greater than or equal to ⁇ MIN .
- ⁇ MIN [dB] is the minimum SINR value required for the uplink communication quality of the macro mobile station 4 to satisfy a predetermined quality. ⁇ MIN is set in advance.
- interference power the interference power I H [dBm] that the femtocell mobile station 2-1 belonging to the femtocell base station 1-1 to be controlled gives to the uplink reception (desired wave) of the macro base station 3,
- other femtocell mobile stations such as mobile station 2-2 located in the macrocell 6.
- a plurality of macro mobile stations 4 located in one macro cell 6 use different PRBs. Therefore, it can be assumed that interference from other macro mobile stations located in one macro cell 6 is zero.
- ⁇ can be approximately defined by the following equation (1).
- S M [dBm] is the desired wave power, that is, the uplink received power from the macro mobile station 4 in the macro base station 3.
- the resource parameter R1 is logarithmically displayed so as to be in dB unit. It is also assumed that thermal noise is negligible. Note that it is assumed that the uplink interference power per femtocell mobile station is I H regardless of the position of the femtocell mobile station in the macro cell, and Equation (1) is assumed to be satisfied by any femtocell.
- the resource parameter R1 may be a value that increases or decreases according to the sum of the radio resource usage or the usage rate of the plurality of femtocells 5.
- the resource parameter R1 is defined as a function that monotonously increases with respect to the sum of the usage amounts or the usage rates of the radio resources of the plurality of femtocells 5.
- the sign of R1 in Equation (1) may be changed from negative to positive.
- the resource parameter R1 may be defined as the sum of the radio resource usage rates U H, i of each femtocell 5, for example, as shown in Equation (2).
- uplink transmission power control is performed so that the average uplink transmission power P UL, j [dBm] per PRB follows the following equation (3).
- j is a subscript representing M or H, and corresponds to the macro mobile station 4 or the femtocell mobile station 2, respectively.
- P MAX, j [dBm] is the maximum uplink transmission power.
- P O — j [dBm] is the uplink target received power.
- L j is the propagation loss L H between the propagation loss L M or femto cell base station 1-1 and the femto cell mobile station 2-1, between the macro base station 3 and the femto cell mobile station 2-1.
- the propagation loss between the macro base station 3 and the macro mobile station 4 is the same as that of the macro base station 3 and the femto cell base station 1-1. assumed to be equal to the propagation loss L M between cells the mobile station 2-1.
- ⁇ j is a correction value applied to the propagation losses L M and L H.
- S M and I H can be expressed by the following equations (4-1) and (4-2).
- the condition that the equal sign of Expression (1) is satisfied corresponds to a situation in which the SINR of the desired wave signal in the macro base station 3 is minimized.
- the condition for satisfying the equality in equation (1) corresponds to a situation where the sum of the uplink interference power from the plurality of femtocell mobile stations 2 is the upper limit. That is, in this situation, the transmission power of the femtocell mobile station 2-1 is the maximum value allowed.
- the uplink target received power PO_H can be reduced as the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5 increases.
- R1 may be defined so that the size of the resource parameter R1 is always 1 or more in order to prevent P O_H from becoming excessive.
- the resource parameter R1 may be limited to a minimum value of 1, or a value obtained by adding 1 to the sum of the radio resource usage rates of the plurality of femtocells 5. Then, the resource parameter R1 is always a value of 1 or more.
- the uplink interference power per femtocell mobile station 2 is made the same regardless of the position of the femtocell mobile station 2 in the macro cell 6, Uplink interference exerted on the macrocell 6 from the plurality of femtocells 5 overlapping with the macrocell 6 can be suppressed to a certain level or less. Further, regardless of the total number N of the plurality of femtocells 5, when the sum of the uplink PRB usage rates of the plurality of femtocells 5 is relatively small, the uplink transmission power of the femtocell mobile station 2-1 is relatively Can be set high. Therefore, by using the equation (5), it is possible to suppress the uplink communication quality of the femtocell mobile station 2-1 from being excessively lowered due to the suppression of the uplink interference to the macro cell 6.
- the upper limit value of all uplink interference in the macro base station 3 reaches the macro base station 3 from the macro mobile station 4 regardless of the number of femtocell base stations 1 installed. This value is determined by subtracting ⁇ MIN from the reception power S M of the upstream signal (desired wave). Therefore, the communication quality (ie SINR) of the uplink signal of the macro cell 6 can be expected to be equal to or higher than ⁇ MIN .
- Patent Document 1 The idea of Patent Document 1 is that the uplink resource usage rate U H, i is always set to 1 for a femtocell base station 1 having a connected femtocell mobile station 2, and the connected femtocell mobile station This corresponds to setting the uplink resource usage rate U H, i to 0 for a femtocell base station 1 that does not have 2.
- this embodiment is the same as Patent Document 1 in that the uplink resource usage rate U H, i is 0 for a femtocell base station 1 that does not have a connected femtocell mobile station 2.
- the uplink resource usage rate U H, i for the femtocell base station 1 having the connected femtocell mobile station 2 varies depending on the usage amount of the uplink resource, and is greater than 0 and 1 It becomes the following values.
- the resource parameter R1 reflecting the sum of the PRB usage rates is smaller in this embodiment than in the concept of Patent Document 1. Therefore, the present embodiment can increase the uplink target received power PO_H by using, for example, the equation (5) as compared with the case of complying with the idea of Patent Document 1. As a result, this embodiment can set the uplink transmission power of the femtocell mobile station 2-1 higher than that of Patent Document 1.
- FIG. 8 is a block diagram showing a configuration example of a radio communication system according to the present embodiment.
- the femtocell base station 1-1 has the function of the transmission power control apparatus 10 (uplink transmission power control unit 11).
- the uplink transmission power control unit 11 illustrated in FIG. 8 includes an R1 acquisition unit 110 and an uplink TPC setting unit 111.
- the R1 acquisition unit 110 receives the resource parameter R1 from the resource parameter transmission unit 22 arranged in the management server 151.
- the uplink TPC setting unit 111 generates uplink target received power PO_H in which the resource parameter R1 is reflected, and supplies this to the radio communication unit 100.
- the radio communication unit 100 transmits a downlink signal encoded with control data and user data to the femtocell mobile station 2-1. Also, the radio communication unit 100 receives an uplink signal transmitted from the femtocell mobile station 2-1, and decodes received data from the uplink signal. Further, the radio communication unit 100 transmits the uplink target received power PO_H to the femtocell mobile station 2-1.
- the broadcast information acquisition unit 101 receives a broadcast signal transmitted from the macro base station 3 into the macro cell 6 via the radio. Broadcast information acquisition section 101 restores broadcast information from the received broadcast signal, and acquires macro cell transmission power information included in the broadcast information.
- the macro cell transmission power information includes (1) a transmission power P TX_M [dBm] of a downlink reference signal transmitted from the macro base station 3, and (2) an uplink target reception power used for determining an uplink transmission power in the macro mobile station 4.
- P O_M [dBm] and (3) a correction coefficient ⁇ M for the propagation loss used for determining the uplink transmission power in the macro mobile station 4.
- the broadcast information acquisition unit 101 is, for example, in Network Listening Mode (NLM) that is activated periodically (eg, several hours to 1 day) during the initial installation of the femtocell base station 1 or during operation of the femtocell base station 1.
- NLM Network Listening Mode
- the notification information acquisition operation may be performed.
- the measurement report acquisition unit 102 receives received power (RSRP: Reference Signal Received Power) P RX_H [dBm] of the downlink reference signal transmitted from the femtocell base station 1-1 and the downlink reference signal transmitted from the macro base station 3.
- the measurement report including the measurement result of the received power P RX_M [dBm] is received from the femtocell mobile station 2-1.
- the uplink RUR reporting unit 103 transmits the uplink PRB usage rate in the femtocell base station 1-1 to the resource / parameter generating unit 21 of the management server 151 as the uplink resource usage rate (uplink RUR).
- the uplink PRB usage rate may be defined as the ratio of the PRB actually allocated to the mobile station 2-1 to the total uplink PRB that can be allocated to the femtocell mobile station 2-1. All uplink PRBs that can be allocated to the femtocell mobile station 2-1 are determined depending on the frequency bandwidth (e.g. 10 MHz) applied to the uplink.
- the femtocell base station 1-1 may measure the uplink PRB usage rate reported to the management server 151, for example, periodically (e.g.
- the reported usage rate of uplink PRB may be a moving average value calculated using a plurality of periodic measurement values.
- the uplink RUR reporting unit 103 may report the uplink PRB usage rate to the management server 151 using a reporting cycle (e.g. about 10 seconds) longer than the uplink PRB usage rate measurement cycle.
- the radio communication unit 200 transmits an uplink signal in which control data and user data are encoded to the femtocell base station 1-1.
- Radio communication section 200 receives a downlink signal transmitted from femtocell base station 1-1, and decodes received data from the downlink signal. Further, the radio communication unit 200 supplies the uplink target received power PO_H received from the femtocell base station 1-1 to the uplink transmission power determination unit 202.
- Received power measuring unit 201 measures the femtocell base station 1-1 RSRP (P RX_H), the macro base station 3 RSRP the (P RX_M). These measurements may be performed at a predetermined cycle (eg about 100 milliseconds).
- the base station to be measured (the femtocell base station 1-1 and the macro base station 3) and the measurement item (RSRP) are specified by the femtocell base station 1-1 sending a Measurement Control message to the femtocell mobile station 2-1. To do so. Then, the reception power measurement unit 201 reports the measurement results of P RX_H and P RX_M to the femtocell base station 1-1 via the wireless communication unit 200.
- the report may be performed in a predetermined cycle (eg about 1 second).
- the reported measurement results of P RX_H and P RX_M may be values filtered using a predetermined weighting factor. Further, the reported measurement result of P RX_H and P RX_M may be a moving average value calculated using a plurality of measurement values.
- Uplink transmission power determining section 202 determines uplink transmission power P UL, H by radio communication section 200 using uplink target received power PO_H received from femtocell base station 1-1.
- the uplink transmission power determination unit 202 may determine the uplink transmission power P UL, H according to the above equation (3).
- the operations of the resource / parameter generation unit 21 and the transmission unit 22 arranged in the management server 151 are basically the same as those described with reference to FIG. 5 in the first embodiment of the invention.
- the resource parameter transmission unit 22 may transmit the resource parameter R1 to the plurality of femtocell base stations 1 (e.g. base stations 1-1 and 1-2).
- the cycle in which the transmission unit 22 transmits the resource parameter R1, that is, the update cycle of the resource parameter R1 is an arbitrary cycle (eg 100) longer than the reporting cycle of the uplink resource usage rate from the plurality of femtocell base stations 1. About seconds).
- FIG. 9 is a flowchart showing a specific example of uplink transmission power control by femtocell base station 1-1 according to the present embodiment.
- the femtocell base station 1-1 transmits the uplink PRB usage rate of the femtocell 5-1 managed by itself to the management server 151.
- parameters necessary for calculating the uplink target received power PO_H are obtained or generated using the above-described equation (5).
- the femtocell base station 1-1 receives broadcast information transmitted from the macro base station 3, and acquires macro cell transmission power information included in the broadcast information.
- the macro cell transmission power information includes P TX_M , P O_M , and ⁇ M.
- the femtocell base station 1-1 receives the RSRP (P RX_M and P RX_H) of the femto cell 5-1 managed by the macro cell 6 and itself from the femto cell mobile station 2-1.
- the femtocell base station 1-1 determines the propagation loss L M between the macro base station 3 and the femtocell mobile station 2-1, and itself (base station 1-1) and the femtocell mobile station 2-1. calculating the propagation loss L H between.
- Propagation loss L M can be calculated by the difference between the RSRP (P RX_M) of P TX_M and macro 6 included in the macro cell transmission power information.
- the propagation loss L H can be calculated from the difference between the transmission power P TX_H of the base station 1-1 itself and RSRP (P RX_H ).
- P RX_H the propagation loss L H is strictly a propagation loss of the downlink, assuming that there is no significant difference in the loss characteristics in the frequency of the downlink uplink, uplink It is used as a propagation loss.
- step S35 the femtocell base station 1-1 receives the resource parameter R1 from the management server 151.
- step S36 the femtocell base station 1-1 uses the values obtained in steps S32 to S35 to calculate the uplink target received power PO_H according to equation (5).
- FIG. 10 is a flowchart showing a specific example of the operation of the femtocell mobile station 2-1.
- the femtocell mobile station 2-1 measures the RSRP (P RX_M and P RX_H ) of the macro cell 6 and the femto cell 5-1 to which the femto cell 5-1 belongs.
- the femtocell mobile station 2-1 transmits the measurement result of RSRP (P RX_M and P RX_H ) to the femtocell base station 1-1.
- step S43 the femtocell mobile station 2-1 determines whether or not the updated value of the uplink target received power PO_H has been received from the femtocell base station 1-1.
- femtocell mobile station 2-1 performs the adjustment of uplink transmission power P UL, H using the updated value of the uplink transmission power P UL, H (step S44).
- Adjusting uplink transmission power P UL, H, using the updated value of P O_H may be performed by calculating the updated value of the uplink transmission power P UL, H according to equation (3).
- FIG. 11 is a flowchart showing a specific example of the supply procedure of the resource parameter R1 by the management server 151.
- the management server 151 receives the uplink PRB usage rate of each femtocell 5 from each of the plurality of femtocell base stations 1.
- the management server 151 aggregates a plurality of uplink PRB usage rates related to the plurality of femtocells 5 and generates a resource parameter R1.
- the management server 151 transmits the resource parameter R1 to the target femtocell base station 1-1.
- the femtocell 5 while maintaining the condition that the total uplink interference amount in the macro base station 3 is a certain level or less, the femtocell 5 depends on the uplink resource (PRB) usage amount or usage rate for each femtocell 5. A difference is provided in the control content of each uplink transmission power. That is, the femtocell 5 having a large uplink resource usage amount or usage rate can reduce transmission power preferentially compared to the femtocell 5 having a low uplink resource usage amount or usage rate.
- PRB uplink resource
- the correction parameter ⁇ i is used in addition to the resource parameter R1 for uplink transmission power control in the femtocell 5-1.
- the resource parameter R1 includes a value that increases or decreases according to the sum of the uplink resource usage or the usage rate of the plurality of femtocells 5.
- the correction parameter ⁇ i is defined as a value that increases or decreases according to the uplink resource usage or usage rate of the target femtocell 5-1 (that is, not a sum related to a plurality of femtocells). Further, the correction parameter ⁇ i is determined so that the sum of ⁇ i over the plurality of femtocells 5 is substantially constant.
- ⁇ i is determined as a monotonically decreasing function of the upstream PRB usage rate U H, i .
- the reason is to make the uplink interference exerted on the macro base station 3 fair among the plurality of femtocells 5 regardless of the uplink PRB usage rate of each femtocell 5. That is, the femtocell 5 having a large uplink resource usage amount or usage rate can reduce transmission power preferentially compared to the femtocell 5 having a low uplink resource usage amount or usage rate.
- ⁇ i is the maximum value ⁇ max when U H, i is 0 which is the minimum value
- ⁇ i is the minimum value ⁇ max when U H, i is 1 which is the maximum value.
- I a linear function.
- ⁇ i can be formulated as shown in Equation (8).
- ⁇ max is obtained by substituting equation (8) into equation (7).
- Formula (8) is an example, and if ⁇ i satisfies the condition that the relationship of Formula (7) and the monotone decreasing function are satisfied, the formulation of ⁇ i is arbitrary.
- the uplink target received power PO_H can be formulated as shown in Expression (9).
- each femtocell 5 is maintained while maintaining the condition that the total uplink interference amount given to the macro base station 3 by the plurality of femtocells 5 arranged so as to overlap the inside of the macrocell 6 is below a certain level.
- the calculation formula of the uplink target received power PO_H can be changed for each femtocell base station 1 in accordance with the uplink PRB usage rate. That is, the femtocell 5 with a high uplink resource usage or usage rate can preferentially reduce the transmission power compared to the femtocell 5 with a low uplink resource usage or usage rate.
- FIG. 12 is a flowchart showing a specific example of uplink transmission power control by femtocell base station 1-1 according to the present embodiment. Steps S31 to S34 shown in FIG. 12 are the same as steps S31 to S34 shown in FIG.
- the femtocell base station 1-1 receives the resource parameter R1 and the correction parameter ⁇ i from the management server 151.
- the femtocell base station 1-1 calculates the uplink target received power PO_H according to equation (9) using the values obtained in steps S32 to S34 and step S65.
- FIG. 13 is a flowchart showing a specific example of a procedure for supplying the resource parameter R1 and the correction parameter ⁇ i by the management server 151.
- Steps S51 to S52 shown in FIG. 13 are the same as steps S51 to S52 shown in FIG.
- the management server 151 generates the correction parameter ⁇ i according to, for example, the equations (7) and (8).
- step S74 the management server 151 transmits the resource parameter R1 and the correction parameter ⁇ i to the target femtocell base station 1-1.
- FIG. 14 is a block diagram showing a configuration example of the wireless communication system according to the present embodiment.
- the femtocell base station 1-1 has the functions of a transmission power control device 10 (uplink transmission power control unit 11) and a parameter supply device 20 (resource / parameter generation unit 21).
- the resource parameter generation unit 21 receives the uplink PRB usage rate of each femtocell 5 from another femtocell base station 1 instead of the management server 151, and generates a resource parameter R1.
- the uplink transmission power control unit 11 illustrated in FIG. 14 includes an uplink TPC setting unit 111.
- the uplink TPC setting unit 111 generates the uplink target received power PO_H in which the resource parameter R1 generated by the generation unit 21 is reflected, and supplies this to the radio communication unit 100.
- the uplink RUR reporting unit 103 shown in FIG. 14 transmits the uplink PRB usage rate of the femtocell 5-1 to the other femtocell base station 1 instead of the management server 151.
- FIG. 15 is a flowchart showing a specific example of uplink transmission power control by the femtocell base station 1-1 according to the present embodiment. Steps S32 to S34 and Step S36 shown in FIG. 15 are the same as Steps S32 to S34 and Step S36 shown in FIG.
- the femtocell base station 1-1 transmits the uplink PRB usage rate of the own cell 5-1 to each of the other femtocell base stations 1.
- the femtocell base station 1-1 receives the uplink PRB usage rate of each femtocell 5 from each of the other femtocell base stations 1.
- the femtocell base station 1-1 generates the resource parameter R1 by counting the uplink PRB usage rate of the other femtocell 5 and the uplink PRB usage rate of the own cell 5-1.
- this embodiment has an advantage that the management server 151 is not required.
- the configuration example in which one management server 151 exists for one macro cell 6 is shown.
- the number of management servers 151 per macro cell 6 is not limited to one.
- the management server 151 may supply the resource parameter R1 with respect to the plurality of macro cells 6 and the plurality of femto cells 5 overlapping with these.
- the number of management servers 151 per macro cell 6 is less than one. It is also possible that the number of management servers 151 per macro cell 6 is 1 or more.
- a set of femtocell base stations 1 managed by one management server 151 becomes a part of the plurality of femtocell base stations 1 arranged in the macro cell 6.
- the resource parameter R1 may be exchanged between the plurality of management servers 151.
- the parameter supply device 20 may be arranged in another device.
- the parameter supply device 20 may be arranged in an OAM (Operation & Maintenance) server corresponding to the management server 151, or may be an MME (Mobility Management Entity), S-GW (Serving Gateway). ) Or HeNB GW.
- OAM Operaation & Maintenance
- MME Mobility Management Entity
- S-GW Serving Gateway
- HeNB GW HeNB GW
- the parameter supply device 20 may be arranged in the HNB GW or in the RNC.
- ⁇ Other embodiment C> In the fourth embodiment of the invention, an example has been described in which information on uplink resource usage or usage rate is exchanged between a plurality of femtocell base stations 1.
- the plurality of femtocell base stations 1 are in an equal relationship with each other.
- the relationship between the plurality of femtocell base stations 1 is not necessarily equal, and for example, at least one femtocell base station 1 serving as an anchor may be set in advance in the macro cell 6. In this case, each femtocell base station 1 may report the resource usage or usage rate to the anchor femtocell base station 1.
- the anchor femtocell base station 1 may generate the resource parameter R1 and notify the femtocell base station 1 of this, similarly to the management server 151.
- the role of the anchor may be always performed by a specific femtocell base station 1 or may be changed between a plurality of femtocell base stations 1 at a predetermined period.
- Embodiments 2 to 4 of the invention have described the case where the number of femtocell mobile stations 2 connected to the femtocell base station 1 is one. However, the number of femtocell mobile stations 2 connected to the femtocell base station 1 may be plural. In this case, first, the femtocell base station 1 may obtain the uplink target received power PO_H for each femtocell mobile station 2 as in any of Embodiments 2 to 4. In the LTE scheme, generally, the uplink target reception power PO_H for each mobile station is set by adding correction for each mobile station to the reference value of the uplink target reception power for each cell.
- the femtocell base station 1 next obtains the average value (or median value) of the uplink target received power that is commonly applied to the plurality of femtocell mobile stations 2, and calculates the difference with respect to this average value for each femtocell movement What is necessary is just to obtain
- ⁇ Other embodiment E> In the first to fourth embodiments of the invention, a HetNet environment in which a macro cell and a plurality of femto cells are arranged in an overlapping manner has been described.
- the application destination of the present invention is not limited to an environment including a macro cell and a plurality of femto cells.
- an environment in which a plurality of pico cells and macro cells having a communication area larger than that of a femto cell base station are mixed may be used.
- the uplink transmission power control described in Embodiments 1 to 4 of the invention can be applied for uplink transmission power control of a pico cell.
- the picocell base station may acquire necessary information from the macro base station using the inter-base station interface (eg X2 interface) without depending on the broadcast information from the macro base station.
- the present invention can be applied to any HetNet environment such as a mixed environment of macro cells, pico cells, and femto cells, and a mixed environment of macro cells and micro cells.
- the resource parameter R1 is reflected on the uplink target received power PO_H .
- the target that reflects the resource parameter R1 in the uplink transmission power control of the femtocell 5 is not limited to the uplink target received power PO_H .
- the resource parameter R 1 may be reflected in the maximum transmission power P MAX, H of the femtocell mobile station 2.
- the uplink interference given to the macro base station 3 is allowed even if the uplink transmission power fluctuation of the femtocell mobile station 2 may be large. It can be stably suppressed below the value.
- Equation (4-1) and (4-2) are changed to the following equations (10-1) and (10): It can be replaced as shown in 10-2).
- P MAX, M [dBm] is the maximum uplink transmission power of the macro mobile station 4.
- Equation (1) the maximum uplink transmission power P MAX of the femtocell mobile station 2-1 , H can be formulated as in equation (11).
- P MAX, M a value (for example, 23 dBm) defined in 3GPP as the maximum transmission power of the mobile station may be used.
- Embodiments 2 to 4 of the invention an example in which all of the plurality of femtocell base stations 1 arranged in the macrocell 6 report the uplink resource usage rate has been described.
- the femtocell base station 1 that reports the resource usage rate may be a part of the plurality of femtocell base stations 1 arranged in the macro cell 6.
- only the activated femtocell base station 1 among the plurality of femtocell base stations 1 arranged in the macro cell 6 may report the uplink resource usage rate.
- the femtocell base station 1 need not always be activated.
- the femtocell base station 1 can stop the function.
- the reception function is often left active.
- the femtocell base station 1 communicating with the femtocell mobile station 2-1 among the plurality of femtocell base stations 1 arranged in the macrocell 6 may report the uplink resource usage rate. Good.
- the correction parameter ⁇ i is determined as a monotonically decreasing function of the upstream PRB usage rate U H, i has been described.
- the correction parameter ⁇ i can also be determined as a monotonically increasing function of U H, i . The reason for this is to increase the uplink communication quality of the femtocell mobile station 2 by increasing the uplink target reception power for the femtocell mobile station 2 having a high uplink PRB usage rate and a high communication load.
- ⁇ i is the minimum value ⁇ max when U H, i is the minimum value 0, and ⁇ i is the maximum value ⁇ max when U H, i is the maximum value 1.
- ⁇ i can be formulated as shown in Equation (12).
- Formula (12) is an example, and if ⁇ i satisfies the condition that the relationship of Formula (7) and the monotonically increasing function are satisfied, the formulation of ⁇ i is arbitrary.
- the wireless communication system to which the present invention is applied is not particularly limited.
- a W-CDMA system may be used, or a wireless communication system that employs a TDD (Time Division Duplex) system in which the same radio frequency is divided in time in the uplink and downlink (eg, WiMAX, IEEE 802.16)
- TDD Time Division Duplex
- ⁇ Other embodiment J> The processing of the transmission power control device 10 and the parameter supply device 20 described in the first to fourth embodiments of the invention is implemented using a semiconductor processing device including an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), and the like. May be. These devices may be mounted by causing a computer such as a microprocessor to execute a program. Specifically, a program including a group of instructions for causing the computer to execute the algorithm shown in any of FIGS. 6, 7, 9, 11, 12, 13, and 15 is created, and the program is supplied to the computer. That's fine.
- ASIC Application Specific Integrated Circuit
- DSP Digital Signal Processor
- Non-transitory computer readable media include various types of tangible storage media (tangible storage medium). Examples of non-transitory computer-readable media include magnetic recording media (eg flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg magneto-optical discs), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable ROM), flash ROM, RAM (random access memory)) are included.
- the program may also be supplied to the computer by various types of temporary computer-readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves.
- the temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.
- Uplink transmission power control unit 20 Parameter supply device 21 Resource parameter generation unit 22 Resource parameter transmission unit 100 Wireless communication unit 101 Broadcast information acquisition unit 102 Measurement report acquisition unit 103 Uplink RUR report unit 110 Resource parameter (R1) Acquisition unit 111 Uplink TPC setting unit 150 Host network 151 Management server 200 Wireless communication unit 201 Received power measurement unit 202 Uplink transmission power determination unit
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Abstract
Description
図1は、本発明の実施の形態1に係る無線通信システムのネットワーク構成例を示している。本実施の形態の無線通信システムは、複数のフェムトセル基地局1、及びマクロ基地局3を有する。各フェムトセル基地局1は、フェムトセル5を形成し、フェムトセル移動局2との間で無線通信を行う。マクロ基地局3は、マクロセル6を形成し、マクロ移動局4との間で無線通信を行う。各フェムトセル5は、マクロセル6と少なくとも一部が重なり合っている。
(a)複数のフェムトセル5の上りリソース使用率の和
(b)複数のフェムトセル5の上りリソース使用率の和の平均値、及び複数のフェムトセル5の数
(c)複数のフェムトセル5の上りリソース使用量の和
(d)複数のフェムトセル5の上りリソース使用量の和の平均値、及び複数のフェムトセル5の数
本実施の形態では、上述した発明の実施の形態1の具体例について説明する。本実施の形態では、LTE方式の無線通信システムに関して説明する。また、本実施の形態では、図2の構成例のように、送信電力制御装置10の機能がフェムトセル基地局1に配置され、パラメータ供給装置20の機能が管理サーバ151に配置された例について説明する。さらに、本実施の形態では、フェムトセル5の上り送信電力制御のために、リソース・パラメータR1をフェムトセル基地局1における上り目標受信電力PO_Hに反映させる例について説明する。
本実施の形態では、上述した実施の形態2の変形について説明する。本実施の形態では、マクロ基地局3における全上り干渉量が一定レベル以下になる条件を維持しながらも、フェムトセル5毎の上りリソース(PRB)使用量又は使用率に応じて、フェムトセル5毎の上り送信電力の制御内容に差を設ける。つまり、上りリソース使用量又は使用率が多いフェムトセル5は、上りリソース使用量又は使用率が少ないフェムトセル5に比べて、優先的に送信電力を低減できるようにする。
本実施の形態では、上述した発明の実施の形態1の具体例について説明する。本実施の形態では、図3の構成例のように、送信電力制御装置10及びパラメータ供給装置20の機能が共にフェムトセル基地局1に配置された例について説明する。すなわち、複数のフェムトセル基地局1は、上りリソース(PRB)の使用量又は使用率をお互いに交換する。上りリソース(PRB)の使用量又は使用率を複数の基地局1間で送受信するためには、基地局間で使用可能な通信インタフェース、例えば3GPPで標準化されているX2インタフェースを用いればよい。
発明の実施の形態2及び3では、1つのマクロセル6に対して1つの管理サーバ151が存在する構成例を示した。しかしながら、マクロセル6当たり管理サーバ151の数は1つに限定されるものではない。例えば、管理サーバ151は、複数のマクロセル6とこれらと重なり合う複数のフェムトセル5に関して、リソース・パラメータR1の供給を行ってもよい。この場合、マクロセル6当たりの管理サーバ151の数は1未満となる。また、マクロセル6当たりの管理サーバ151の数が1以上となる場合も可能である。この場合は、1つの管理サーバ151によって管理されるフェムトセル基地局1の集合は、マクロセル6内に配置された複数のフェムトセル基地局1の一部となる。マクロセル6内の全フェムトセル基地局1からの上り干渉を把握するために、複数の管理サーバ151の間でリソース・パラメータR1を交換してもよい。
発明の実施の形態2及び3では、パラメータ供給装置20が管理サーバ151に配置される例を示した。しかしながら、パラメータ供給装置20は、他の装置に配置されてもよい。例えば、LTE方式の無線通信システムでは、パラメータ供給装置20は、管理サーバ151に相当するOAM(Operation & Maintenance) サーバに配置されてもよいし、MME(Mobility Management Entity)、S-GW(Serving Gateway)、又はHeNB GWに配置されもよい。また、W-CDMA方式の無線通信システムでは、パラメータ供給装置20は、HNB GWに配置されてもよいし、又はRNCに配置されてもよい。
発明の実施の形態4では、複数のフェムトセル基地局1の間で上りリソース使用量又は使用率の情報を交換する例を示した。この例では、複数のフェムトセル基地局1は、互いに対等の関係であった。しかしながら、複数のフェムトセル基地局1の関係は必ずしも対等である必要はなく、例えばアンカーとなるフェムトセル基地局1をマクロセル6内で少なくとも1台予め設定してもよい。この場合、各フェムトセル基地局1は、アンカーのフェムトセル基地局1にリソース使用量又は使用率を報告すればよい。また、アンカーのフェムトセル基地局1は、管理サーバ151と同様に、リソース・パラメータR1を生成し、これを各フェムトセル基地局1に通知すればよい。アンカーの役割は、特定のフェムトセル基地局1が常に行ってもよいし、複数のフェムトセル基地局1の間で所定の周期で交代してもよい。
発明の実施の形態2~4では、フェムトセル基地局1に接続するフェムトセル移動局2の数が1つの場合を説明した。しかしながら、フェムトセル基地局1に接続するフェムトセル移動局2の数は複数であってもよい。この場合、まず、フェムトセル基地局1は、フェムトセル移動局2毎に、実施形態2~4のいずれかのようにして上り目標受信電力PO_Hを求めればよい。LTE方式では、一般的に、セル毎の上り目標受信電力の基準値に移動局毎の補正を加えることで、移動局毎の上り目標受信力PO_Hを設定する。したがって、フェムトセル基地局1は、次に、複数のフェムトセル移動局2に共通に適用される上り目標受信電力の平均値(または中央値)を求め、この平均値に対する差分を各フェムトセル移動局に対する補正として求めればよい。最後に、フェムトセル基地局1は、求めた平均値と差分を各フェムトセル移動局2に通知すればよい。なお、フェムトセル基地局1は、各フェムトセル移動局2に対して、複数のフェムトセル移動局2の間で共通の上り目標受信力として平均値のみを通知してもよい。
発明の実施の形態1~4では、マクロセルと複数のフェムトセルが重なり合って配置されたHetNet環境について説明した。しかしながら、本発明の適用先は、マクロセルと複数のフェムトセルを含む環境に限定されるものではない。例えば、フェムトセル基地局より通信エリアが大きい複数のピコセルとマクロセルとが混在する環境であってもよい。この場合、発明の実施の形態1~4で説明した上り送信電力制御をピコセルの上り送信電力制御のために適用することができる。また、ピコセル基地局は、マクロ基地局からの報知情報によらず、基地局間インタフェース(e.g. X2インタフェース)を用いて、マクロ基地局から必要な情報を取得してもよい。また、マクロセルとピコセルの混在環境以外にも、マクロセル、ピコセル、及びフェムトセルの混在環境、マクロセル及びマイクロセルの混在環境など、任意のHetNet環境に対して本発明を適用することができる。
発明の実施の形態2~4では、リソース・パラメータR1を上り目標受信電力PO_Hに反映する例を示した。しかしながら、発明の実施の形態1で述べた通り、フェムトセル5の上り送信電力制御においてリソース・パラメータR1を反映する対象は、上り目標受信電力PO_Hに限られない。例えばフェムトセル移動局2の最大送信電力PMAX,Hにリソース・パラメータR1を反映してもよい。上り最大送信電力PMAX,Hをリソース・パラメータR1に基づいて調整することにより、フェムトセル移動局2の上り送信電力の変動が大きい場合があっても、マクロ基地局3に与える上り干渉を許容値以下に安定して抑えることができる。
発明の実施の形態2~4では、マクロセル6内に配置された複数のフェムトセル基地局1の全てが上りリソース使用率の報告を行う例について説明した。しかしながら、リソース使用率の報告を行うフェムトセル基地局1は、マクロセル6内に配置された複数のフェムトセル基地局1の一部であってもよい。例えば、マクロセル6内に配置された複数のフェムトセル基地局1のうち、起動しているフェムトセル基地局1のみが上りリソース使用率の報告を行なってもよい。フェムトセル基地局1は常に起動している必要はなく、例えば、ユーザが不在の場合には、フェムトセル基地局1は機能を停止することもできる。ただし、停止後にユーザ(移動局2)の存在を検知して自動的に起動するために、受信機能は起動したままにすることが多い。
発明の実施の形態3では、上りPRB使用率UH,iの単調減少関数として補正パラメータΔiを決定する例について説明した。しかしながら、補正パラメータΔiはUH,iの単調増加関数として決定することもできる。その理由は、上りPRB使用率が高く通信負荷が高いフェムトセル移動局2に対して上り目標受信電力を大きくすることにより、当該フェムトセル移動局2の上り通信品質を高くするためである。単調増加関数の最も簡単な例の1つは、UH,iが最小値の0のときにΔiが最小値-Δmaxとなり、UH,iが最大値の1のときにΔiが最大値Δmaxとなる一次関数である。この場合、Δiは、式(12)のように定式化できる。ただし、式(12)は一例であり、Δiが式(7)の関係と単調増加関数であるとの条件を満たせば、Δiの定式化は任意である。
発明の実施の形態2~4は、LTE(E-UTRA)方式の無線通信システムに本発明を適用する場合について説明した。しかしながら、発明の実施の形態1でも述べた通り、本発明の適用先の無線通信方式は特に限定されるものではない。例えば、W-CDMA方式であってもよいし、上り回線と下り回線で同一の無線周波数を時間的に分けて使用するTDD(Time Division Duplex)方式を採用する無線通信システム(例えばWiMAX、IEEE 802.16m)にも本発明は適用可能である。
発明の実施の形態1~4で述べた送信電力制御装置10及びパラメータ供給装置20の処理は、ASIC(Application Specific Integrated Circuit)、DSP(Digital Signal Processor)などを含む半導体処理装置を用いて実装されてもよい。また、これらの装置は、マイクロプロセッサ等のコンピュータにプログラムを実行させることによって実装されてもよい。具体的には、図6、7、9、11、12、13、及び15のいずれかに示したアルゴリズムをコンピュータに行わせるための命令群を含むプログラムを作成し、当該プログラムをコンピュータに供給すればよい。
2、2-1、2-2 フェムトセル移動局
3 マクロ基地局
4 マクロ移動局
5、5-1、5-2 フェムトセル
6 マクロセル
10 送信電力制御装置
11 上り送信電力制御部
20 パラメータ供給装置
21 リソース・パラメータ生成部
22 リソース・パラメータ送信部
100 無線通信部
101 報知情報取得部
102 測定報告取得部
103 上りRUR報告部
110 リソース・パラメータ(R1)取得部
111 上りTPC設定部
150 上位ネットワーク
151 管理サーバ
200 無線通信部
201 受信電力測定部
202 上り送信電力決定部
Claims (47)
- 第1のセルを形成する第1の基地局と、
前記第1のセルより小さく且つ前記第1のセルと少なくとも一部が重なり合う第2のセルを各々が形成する複数の第2の基地局と、
前記複数の第2の基地局により形成される複数の第2のセルの上りリソース使用量の和又は上りリソース使用率の和に応じて増減するリソース・パラメータを用いて、前記複数の第2のセルに含まれる対象セルに関する上り送信電力制御を行う制御手段と、
を備える無線通信システム。 - 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和が増加するにつれて、前記対象セルに属する移動局の上り送信電力が低下するように決定される、請求項1に記載の無線通信システム。
- 前記リソース・パラメータは、前記上りリソース使用率の和に基づくパラメータを含む、請求項1又は2に記載の無線通信システム。
- 前記リソース・パラメータは、(a)前記上りリソース使用率の和、又は(b)前記上りリソース使用率の和の平均値及び前記複数の第2のセルの数、を含む、請求項1~3のいずれか1項に記載の無線通信システム。
- 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和に関して単調増加又は単調減少する関数として定義される、請求項1~4のいずれか1項に記載の無線通信システム。
- 前記制御手段は、前記第1のセルと前記対象セルの間の伝搬損を表す第1の損失パラメータをさらに用いて前記上り送信電力制御を行う、請求項1~5のいずれか1項に記載の無線通信システム。
- 前記第1の損失パラメータは、前記第1の基地局と前記対象セルに属する移動局の間の伝播損として定義される、請求項6に記載の無線通信システム。
- 前記制御手段は、前記第1の基地局における上り許容干渉電力を示すパラメータをさらに用いて前記上り送信電力制御を行う、請求項1~7のいずれか1項に記載の無線通信システム。
- 前記上り送信電力制御は、前記対象セルに属する移動局から送信される上り信号が前記第1の基地局に与える上り干渉を前記上り許容干渉電力以下に抑えるように制御することを含む、請求項8に記載の無線通信システム。
- 前記制御手段は、前記対象セルの上りリソース使用量又は使用率に関して単調減少する関数として定義された補正パラメータをさらに用いて前記上り送信電力制御を行い、
前記補正パラメータは、前記複数の第2のセルにわたる和が実質的に一定となるように決定される、
請求項1~9のいずれか1項に記載の無線通信システム。 - 前記制御手段は、前記対象セルの上りリソース使用量又は使用率に関して単調増加する関数として定義された補正パラメータをさらに用いて前記上り送信電力制御を行い、
前記補正パラメータは、前記複数の第2のセルにわたる和が実質的に一定となるように決定される、
請求項1~9のいずれか1項に記載の無線通信システム。 - 前記上り送信電力制御は、前記対象セルに属する移動局から送信される上り信号の前記対象セルを形成する対象基地局における目標受信電力を調整することを含む、請求項1~11のいずれか1項に記載の無線通信システム。
- 前記上り送信電力制御は、前記対象セルに属する移動局による上り送信電力の最大値を調整することを含む、請求項1~11のいずれか1項に記載の無線通信システム。
- 各第2のセルのリソース使用量又は使用率を収集し、前記リソース・パラメータを生成し、前記リソース・パラメータを前記制御手段に供給する供給手段をさらに備える、請求項1~13のいずれか1項に記載の無線通信システム。
- 前記供給手段は、前記複数の第2の基地局と通信可能な制御装置に配置され、
前記制御手段は、前記複数の第2の基地局の各々に配置される、
請求項14に記載の無線通信システム。 - 前記供給手段は、前記複数の第2の基地局のうち少なくとも1つに配置され、
前記制御手段は、前記複数の第2の基地局の各々に配置される、
請求項14に記載の無線通信システム。 - 前記上り送信電力制御は、前記対象セルに属する複数の移動局に関する前記目標受信電力の平均値を前記複数の移動局に通知することを含む、請求項12に記載の無線通信システム。
- 前記上り送信電力制御は、前記対象セルに属する複数の移動局に関する前記目標受信電力の平均値、及び前記目標受信電力の平均値に対する移動局毎の差分を、前記複数の移動局の各々に通知することを含む、請求項12に記載の無線通信システム。
- 前記複数の第2の基地局の各々は、移動局と通信可能に起動されている基地局である、請求項1~18のいずれか1項に記載の無線通信システム。
- 前記複数の第2の基地局の各々は、移動局と通信中の基地局である、請求項1~18のいずれか1項に記載の無線通信システム。
- 無線通信システムで使用される送信電力制御装置であって、
前記無線通信システムは、第1のセルを形成する第1の基地局、及び前記第1のセルより小さく且つ前記第1のセルと少なくとも一部が重なり合う第2のセルを各々が形成する複数の第2の基地局を含み、
前記送信電力制御装置は、前記複数の第2の基地局により形成される複数の第2のセルの上りリソース使用量の和又は上りリソース使用率の和に応じて増減するリソース・パラメータを用いて、前記複数の第2のセルに含まれる対象セルに関する上り送信電力制御を行う制御手段を備える、
送信電力制御装置。 - 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和が増加するにつれて前記対象セルに属する移動局の上り送信電力が低下するように決定される、請求項21に記載の送信電力制御装置。
- 前記リソース・パラメータは、前記複数の第2のセルの上りリソース使用率の和に基づくパラメータを含む、請求項21又は22に記載の送信電力制御装置。
- 前記リソース・パラメータは、(a)前記上りリソース使用率の和、又は(b)前記上りリソース使用率の和の平均値及び前記複数の第2のセルの数、を含む、請求項21~23のいずれか1項に記載の送信電力制御装置。
- 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和に関して単調増加又は単調減少する関数として定義される、請求項21~24のいずれか1項に記載の送信電力制御装置。
- 前記制御手段は、前記第1のセルと前記対象セルの間の伝搬損を表す第1の損失パラメータをさらに用いて前記上り送信電力制御を行う、請求項21~25のいずれか1項に記載の送信電力制御装置。
- 前記第1の損失パラメータは、前記第1の基地局と前記対象セルに属する移動局の間の伝播損として定義される、請求項26に記載の送信電力制御装置。
- 前記制御手段は、前記第1の基地局における上り許容干渉電力を示すパラメータをさらに用いて前記上り送信電力制御を行う、請求項21~27のいずれか1項に記載の送信電力制御装置。
- 前記上り送信電力制御は、前記対象セルに属する移動局から送信される上り信号が前記第1の基地局に与える上り干渉を前記上り許容干渉電力以下に抑えるように制御することを含む、請求項28に記載の送信電力制御装置。
- 前記制御手段は、前記対象セルの上りリソース使用量又は使用率に関して単調減少する関数として定義された補正パラメータをさらに用いて前記上り送信電力制御を行い、
前記補正パラメータは、前記複数の第2のセルにわたる和が実質的に一定となるように決定される、
請求項21~29のいずれか1項に記載の送信電力制御装置。 - 前記制御手段は、前記対象セルの上りリソース使用量又は使用率に関して単調増加する関数として定義された補正パラメータをさらに用いて前記上り送信電力制御を行い、
前記補正パラメータは、前記複数の第2のセルにわたる和が実質的に一定となるように決定される、
請求項21~29のいずれか1項に記載の送信電力制御装置。 - 前記上り送信電力制御は、前記対象セルに属する移動局から送信される上り信号の前記対象セルを形成する対象基地局における目標受信電力を調整することを含む、請求項21~31のいずれか1項に記載の送信電力制御装置。
- 前記上り送信電力制御は、前記対象セルに属する移動局による上り送信電力の最大値を調整することを含む、請求項21~31のいずれか1項に記載の送信電力制御装置。
- 前記上り送信電力制御は、前記対象セルに属する複数の移動局に関する前記目標受信電力の平均値を前記複数の移動局に通知することを含む、請求項32に記載の送信電力制御装置。
- 前記上り送信電力制御は、前記対象セルに属する複数の移動局に関する前記目標受信電力の平均値、及び前記目標受信電力の平均値に対する移動局毎の差分を、前記複数の移動局の各々に通知することを含む、請求項32に記載の送信電力制御装置。
- 前記複数の第2の基地局の各々は、移動局と通信可能に起動されている基地局である、請求項21~35のいずれか1項に記載の送信電力制御装置。
- 前記複数の第2の基地局の各々は、移動局と通信中の基地局である、請求項21~35のいずれか1項に記載の送信電力制御装置。
- 請求項21~37のいずれか1項に記載の送信電力制御装置と、
前記対象セルに属する移動局と通信可能な無線通信手段と、
を備える、基地局装置。 - 無線通信システムで使用されるパラメータ供給装置であって、
前記無線通信システムは、
第1のセルを形成する第1の基地局と、
前記第1のセルより小さく且つ前記第1のセルと少なくとも一部が重なり合う第2のセルを各々が形成する複数の第2の基地局と、
前記複数の第2の基地局により形成される複数の第2のセルに含まれる対象セルに関する上り送信電力制御を行う制御手段と、
を含み、
前記パラメータ供給装置は、
前記複数の第2のセルの上りリソース使用量の和又は上りリソース使用率の和に応じて増減するリソース・パラメータを、前記上り送信電力制御のために前記制御手段に供給する手段と、
を備える、パラメータ供給装置。 - 無線通信システムで使用される送信電力制御方法であって、
前記無線通信システムは、第1のセルを形成する第1の基地局、及び前記第1のセルより小さく且つ前記第1のセルと少なくとも一部が重なり合う第2のセルを各々が形成する複数の第2の基地局を含み、
前記送信電力制御方法は、前記複数の第2の基地局により形成される複数の第2のセルの上りリソース使用量の和又は上りリソース使用率の和に応じて増減するリソース・パラメータを用いて、前記複数の第2のセルに含まれる対象セルに関する上り送信電力制御を行うことを備える、
送信電力制御方法。 - 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和が増加するにつれて前記対象セルに属する移動局の上り送信電力が低下するように決定される、請求項40に記載の方法。
- 前記リソース・パラメータは、前記複数の第2のセルの上りリソース使用率の和に基づくパラメータを含む、請求項40又は41に記載の方法。
- 前記リソース・パラメータは、(a)前記上りリソース使用率の和、又は(b)前記上りリソース使用率の和の平均値及び前記複数の第2のセルの数、を含む、請求項40~42のいずれか1項に記載の方法。
- 前記リソース・パラメータは、前記上りリソース使用量の和又は前記上りリソース使用率の和に関して単調増加又は単調減少する関数として定義される、請求項40~43のいずれか1項に記載の方法。
- 前記上り送信電力制御を行うことは、前記第1のセルと前記対象セルの間の伝搬損を表す第1の損失パラメータをさらに用いて前記上り送信電力制御を行うことを含む、請求項40~44のいずれか1項に記載の方法。
- 前記第1の損失パラメータは、前記第1の基地局と前記対象セルに属する移動局の間の伝播損として定義される、請求項45に記載の方法。
- 無線通信システムで使用される送信電力制御方法をコンピュータに行わせるためのプログラムが格納された非一時的なコンピュータ可読媒体であって、
前記無線通信システムは、第1のセルを形成する第1の基地局、及び前記第1のセルより小さく且つ前記第1のセルと少なくとも一部が重なり合う第2のセルを各々が形成する複数の第2の基地局を含み、
前記送信電力制御方法は、前記複数の第2の基地局により形成される複数の第2のセルの上りリソース使用量の和又は上りリソース使用率の和に応じて増減するリソース・パラメータを用いて、前記複数の第2のセルに含まれる対象セルに関する上り送信電力制御を行うことを含む、
コンピュータ可読媒体。
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