WO2011070733A1 - 無線通信システム、基地局装置、基地局制御装置、基地局の送信電力制御方法、及びコンピュータ可読媒体 - Google Patents
無線通信システム、基地局装置、基地局制御装置、基地局の送信電力制御方法、及びコンピュータ可読媒体 Download PDFInfo
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Definitions
- the present invention relates to a radio communication system including a base station, and more particularly to a transmission power adjustment method for a base station.
- a femtocell The range covered by such a base station is called a femtocell because it is extremely small compared to the coverage of a base station installed outdoors (hereinafter referred to as a macro base station).
- a cell means the coverage (communication area satisfying required quality) of a base station.
- this ultra-small base station is referred to as a femtocell base station.
- femtocell base stations As an operation mode of the femtocell base station, it is considered that only a pre-registered mobile station connects to the femtocell base station for communication.
- femtocell base stations can be installed in places where radio waves do not reach, such as high floors of buildings and underground malls, they are attracting attention as means for expanding coverage.
- the femtocell base station is considered to be used in systems such as W-CDMA (Wideband Code Division Multiple Access), E-UTRA (Evolved Universal Terrestrial Radio Access, also referred to as LTE: Long Term Evolution), IEEE 802.16m, etc.
- W-CDMA and E-UTRA are wireless communication standards for mobile phones.
- IEEE 802.16m is a wireless communication standard for wireless MAN (Wireless Metropolitan Area Network).
- a scheduler arranged in the base station assigns a physical resource block (PRB), and data transmission using the assigned PRB is performed.
- the PRB is a basic unit of radio resources in the downlink of E-UTRA adopting OFDMA (Orthogonal Frequency Division Multiple Access), includes a plurality of OFDM subcarriers in the frequency domain, and includes at least one symbol time in the time domain. .
- OFDMA is also adopted for the IEEE 802.16m downlink.
- a scheduler arranged in the base station assigns subcarriers, and data transmission using the assigned subcarriers is performed.
- a base station in an existing mobile communication network transmits a control signal called a pilot signal toward an area (coverage) covered by the base station.
- the mobile station establishes synchronization with the base station and estimates a channel by receiving the pilot signal, and transmits / receives data to / from the base station. Therefore, it is possible to provide good communication quality by allowing the mobile station to receive the pilot signal transmitted from the base station with good quality.
- a base station receives a radio signal transmitted from a neighboring base station, and the base station itself uses a traffic situation of the neighboring base station and a measurement result of received power of a transmitted signal from the neighboring base station. It is disclosed that the transmission power is adjusted.
- the base station described in Patent Document 1 has its own transmission power when the traffic of the neighboring base stations is low and the reception power of the radio signal from the neighboring base stations satisfies a predetermined quality. Reduce or stop.
- Patent Document 2 discloses a technique for adjusting the transmission power of a base station similar to that of Patent Document 1 described above. Specifically, in Patent Document 2, in order to efficiently cover an area (insensitive area) that is not sufficiently covered by a neighboring base station, a complementary base station receives a radio signal transmitted from the neighboring base station. It discloses that the power is measured and the transmission power of the own station is adjusted according to the measurement result.
- Patent Document 3 discloses a technique for optimizing the radio parameters (including transmission power) of a newly installed base station when a new base station is installed. Specifically, in Patent Document 3, in order to optimize the radio parameters of the new base station, the mobile station measures the received power of radio waves from the new base station and its surrounding base stations. Then, the new base station adjusts its own radio parameters based on the measurement result of the mobile station.
- Patent Document 4 discloses a technique related to handover of a mobile station to a femto cell. Specifically, the mobile station disclosed in Patent Document 4 receives a radio signal from a neighboring base station, measures reception quality, and acquires a group identifier of the neighboring base station. Then, the mobile station identifies whether the acquired group identifier corresponds to a femtocell base station to which the mobile station can be connected. Is sent to the connected base station. Thereby, it is suppressed that the handover of the mobile station to the femtocell base station that cannot be connected is started.
- Patent Documents 1 and 2 have the following problems. That is, in Patent Documents 1 and 2, when the transmission power of the base station is increased or decreased in order to change the coverage size of the base station, only the reception quality of the neighboring cells (peripheral base stations) at the location where the base station is installed is considered. Absent. In other words, when determining the coverage size of a base station, it is not considered whether a place where a mobile station connected to the base station is located (around the base station) is sufficiently covered by neighboring cells. For this reason, there is a possibility that a dead area that is not sufficiently covered by any base station occurs, and the communication quality of the mobile station may deteriorate.
- Each femtocell has a mobile station (registered mobile station) 95 and communicates with the femtocell base station 93 in response to a user communication request.
- registered mobile station means a mobile station permitted to connect to the femtocell.
- a mobile station that is not permitted to connect to the femtocell is referred to as a “non-registered mobile station” in this specification.
- FIG. 19A shows a case where the femtocell 94 is completely included in the macrocell 92. At this time, it is considered that the received power of the radio signal from the macro base station 91 at the installation location of the femtocell base station 93 is large. If it is assumed that the traffic of the macro base station 91 is low and the technique described in Patent Document 1 is followed, the femtocell base station 93 stops operating, and the mobile station 95 communicates with the macro base station 91.
- FIG. 19B shows a case where the femtocell 94 does not overlap with the macrocell 92 at all. At this time, it is considered that the reception power of the radio signal from the macro base station 91 at the installation location of the femtocell base station 93 is very small or cannot be received. Assuming that the traffic of the macro base station 91 is small and following the technique described in Patent Document 1, the femtocell base station 93 is activated, and the mobile station 95 communicates with the femtocell base station 93.
- FIG. 19C shows a case where a part of the femtocell 94 overlaps with the macrocell 92 and the installation location of the femtocell base station 93 is covered by the macrocell 92. That is, the femtocell base station 93 is arranged at the cell edge of the macrocell 92. At this time, the received power of the radio signal from the macro base station 91 at the installation location of the femtocell base station 93 is considered to be a communicable level although it is relatively small. If it is assumed that the traffic of the macro base station 91 is low and the technique described in Patent Document 1 is followed, the femtocell base station 93 stops its operation.
- the location of the mobile station 95 is outside the macro cell 92. Therefore, if the femtocell base station 93 stops operating on the condition that the installation location of the femtocell base station 93 is covered by the macrocell 92, the mobile station 95 cannot communicate with any base station.
- Patent Document 4 discloses that the mobile station measures the received power of radio waves arriving from the newly installed base station and its surrounding base stations, and the radio parameters of the newly installed base station based on the measurement results of the mobile station. Is disclosed. However, Patent Document 4 does not include a description related to the above-described problem, and does not disclose how to specifically adjust the transmission power of the newly installed base station.
- the present invention has been made based on the above-described knowledge, and an object of the present invention is to provide a wireless communication system, a base station control device, a base station device, and a wireless communication system capable of effectively suppressing the generation of a dead area at a cell boundary.
- a base station transmission power control method and program are provided.
- a radio communication system includes a first base station that transmits a first radio signal, a second base station that transmits a second radio signal, and the first and second radios. It includes at least one wireless terminal capable of receiving a signal and a control unit.
- the control unit based on a measurement result of the reception quality of the first radio signal by the at least one radio terminal, at the radio terminal position where the reception quality of the first radio signal is lower than a first reference, The transmission power of the second radio signal by the second base station is controlled so that the reception quality of the second radio signal exceeds the second reference.
- the base station apparatus includes a radio communication unit that performs radio communication with at least one mobile station, and a control unit that controls transmission power of the radio communication unit.
- the control unit based on a measurement result of reception quality by the at least one mobile station of a neighboring cell signal arriving from a neighboring cell, at the wireless terminal position where the reception quality of the neighboring cell signal is lower than a first reference, The transmission power of the own cell signal by the radio communication unit is controlled so that the reception quality of the own cell signal transmitted from the communication unit exceeds the second reference.
- the reception quality of the neighboring cell signal is lower than the first reference based on the measurement result by at least one mobile station of the reception quality of the neighboring cell signal reaching from the neighboring cell.
- the base station transmission power control method includes the following steps (a) and (b). (A) obtaining a measurement result by at least one mobile station of the reception quality of the neighboring cell signal arriving from the neighboring cell; and (b) based on the measurement result, the reception quality of the neighboring cell signal is a first reference. Transmission power of the own cell signal so that the reception quality of the own cell signal transmitted from the base station that performs radio communication with the at least one mobile station exceeds the second reference To control.
- a fifth aspect of the present invention relates to a program for causing a computer to execute control processing related to a base station device that performs wireless communication with a mobile station.
- the control process performed by the computer that executes the program includes the following steps (a) and (b). (A) obtaining a measurement result by at least one mobile station of the reception quality of the neighboring cell signal arriving from the neighboring cell; and (b) based on the measurement result, the reception quality of the neighboring cell signal is a first reference. Transmission power of the own cell signal so that the reception quality of the own cell signal transmitted from the base station that performs radio communication with the at least one mobile station exceeds the second reference To control.
- a radio communication system a base station control device, a base station device, a base station transmission power control method, and a program capable of effectively suppressing the generation of dead areas at cell boundaries are provided. it can.
- FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment.
- the radio communication system according to the present embodiment includes at least one femtocell base station 1, at least one radio terminal 6, and at least one peripheral base station 7.
- the femtocell base station 1 forms a femtocell 81 and performs wireless communication with the wireless terminal 6.
- the peripheral base station 7 forms a peripheral cell 82.
- the peripheral base station 7 is, for example, a base station (macro cell base station) that forms a macro cell.
- the wireless terminal 6 is a terminal that can communicate with the femtocell base station 1 and can receive a wireless signal transmitted from the neighboring base station 7.
- the wireless terminal 6 includes, for example, a mobile station such as a mobile phone terminal and a fixed terminal that is fixedly installed. In the following description, it is assumed that the wireless terminal 6 is a mobile station.
- the femtocell base station 1 performs access restriction that permits connection only to a specific terminal group (CSG: Closed Subscriber Group)
- the mobile station 6 is regarded as a “registered mobile station” included in the CSG to which access is permitted. That's fine.
- FIG. 2 is a block diagram illustrating a configuration example of the femtocell base station 1.
- a wireless communication unit 10 performs bidirectional wireless communication with a mobile station 6.
- the radio communication unit 10 transmits a downlink radio signal encoded with control data and user data to the mobile station 6, and receives an uplink radio signal transmitted from the mobile station 6.
- the radio communication unit 10 decodes received data from the uplink radio signal.
- the radio communication unit 10 decodes the measurement report of the “neighboring cell reception quality” and supplies it to the transmission control unit 11.
- Information on the transmission frequency and transmission timing of the measurement report by the mobile station 6 may be determined in advance by the femtocell base station 1 or the upper network side, and the femtocell base station 1 may inform the mobile station 6.
- “Neighboring cell reception quality” includes information on the reception quality of the radio signal from the neighboring base station 7 measured by the mobile station 6.
- the reception quality is, for example, reception power such as a pilot signal or a reference signal, or SIR (Signal-to-Interference-Ratio).
- the reception quality of neighboring cells may be, for example, reception power (CPICH RSCP: Received Sign Code Power) or reception quality (CPICH Ec / No) of a common pilot channel (CPICH: Common : Pilot Channel).
- the reception quality of neighboring cells may be, for example, the reception power (RSRP: Reference Signal Received Power) or the reception quality (RSRQ: Reference Signal Received Quality) of the downlink reference signal (Downlink Reference Signal). .
- RSRP Reference Signal Received Power
- RSRQ Reference Signal Received Quality
- the transmission control unit 11 controls the transmission power of the radio communication unit 10 using the “neighboring cell reception quality” reported from the mobile station 6. Specifically, the transmission control unit 11 may determine transmission power so that the mobile station 6 can receive radio waves from at least one cell over the movement range of the mobile station 6. For example, the transmission control unit 11 reduces the transmission power of the wireless communication unit 10 or performs wireless communication on the condition that the mobile station 6 can communicate with at least one neighboring cell 82 even when the femtocell base station 1 stops. The transmission of the unit 10 may be stopped.
- FIG. 3 is a block diagram illustrating a configuration example of the mobile station 6.
- the wireless communication unit 60 performs bidirectional wireless communication with the femtocell base station 1.
- the radio communication unit 60 transmits an uplink radio signal encoded with control data and user data to the base station 1 and receives a downlink radio signal transmitted from the base station 1.
- the radio communication unit 60 decodes received data from the downlink radio signal.
- the radio communication unit 60 supplies this to the measurement unit 61.
- the measurement unit 61 measures the reception quality of neighboring cells in response to a measurement instruction from the femtocell base station 1.
- the measurement unit 61 may cause the radio communication unit 60 to receive a downlink radio signal (for example, a pilot signal) from the neighboring base station 7 and measure reception quality such as neighboring cell received power and SIR.
- a downlink radio signal for example, a pilot signal
- the reporting unit 62 reports the measurement results of the neighboring cell reception quality to the femtocell base station 1 via the wireless communication unit 60.
- the transmission frequency and transmission timing of the measurement report may be determined according to information determined in advance by the femtocell base station 1 or the upper network side.
- FIG. 4 is a flowchart showing a specific example of the output adjustment procedure of the femtocell base station 1.
- the transmission control unit 11 receives a measurement result of neighboring cell reception quality from the mobile station 6.
- the transmission control unit 11 may receive measurement reports from the plurality of mobile stations 6.
- the transmission control unit 11 may receive a plurality of neighboring cell reception qualities measured at different positions at the same time by the same mobile station 6. Further, when the mobile station 6 can receive radio waves from the plurality of neighboring cells 82, the transmission control unit 11 may receive the neighboring cell reception quality related to the plurality of neighboring cells 82 from the mobile station 6.
- the transmission control unit 11 measures the representative value of the reception quality for each of the plurality of neighboring cells 82.
- the representative value may be, for example, a value (X is an arbitrary number between 0 and 100) at which the cumulative probability becomes X percent when the measured values are aggregated in ascending order of reception quality.
- the representative value may be another statistical value such as a minimum value or an average value among a plurality of reception quality measurement values.
- step S103 the transmission control unit 11 selects a maximum value from the representative values of the reception quality of the neighboring cells calculated for each neighboring cell 82, and compares this maximum value with the threshold value A.
- the threshold A may be determined in advance with reference to a quality level at which the mobile station 6 can maintain wireless communication with the base station. The fact that the maximum value selected from the representative values of the reception quality of the neighboring cells for each neighboring cell 82 falls below the threshold A indicates that the reception of the neighboring cell 82 is performed at the position of the mobile station 6 connected to the femtocell base station 1. It means that the quality is not enough for maintaining communication.
- the transmission control unit 11 maintains the transmission power of the wireless communication unit 10 at a relatively high state (step S104). . That is, the transmission of the femtocell base station 1 is continued.
- the transmission control unit 11 maintains the transmission power of the wireless communication unit 10 in a relatively low state (step S105).
- the transmission power of the wireless communication unit 10 may be stopped. Further, the transmission power of the wireless communication unit 10 may be gradually reduced step by step. In this embodiment, transmission power is controlled in a state where the maximum value exceeds the threshold A and in a state where the maximum value does not exceed the threshold A, but the control may be performed in either one of the states.
- the maximum value is selected from the representative values of the reception quality of the neighboring cells for each neighboring cell 82.
- the minimum value may be selected here, or another statistical value such as an average value may be used.
- the femtocell base station 1 does not have to use all the measurement values of the reception quality reported from the mobile station 6. For example, when there are a plurality of mobile stations 6, the femtocell base station 1 may select and use a measurement value reported from a specific mobile station. Further, the femtocell base station 1 may select and use a measurement value at a specific time or time zone.
- FIG. 5 is a flowchart showing another example of the output adjustment procedure of the femtocell base station 1.
- the transmission of the wireless communication unit 10 is continued (step S106).
- the maximum value among the plurality of representative values exceeds the threshold A (YES in step S103)
- the transmission of the wireless communication unit 10 is stopped (step S107).
- the femtocell base station 1 controls the output of the femtocell base station 1 using the neighboring cell reception quality at the mobile station position measured by the mobile station 6.
- the transmission of the femtocell base station 1 can be continued. Therefore, when a dead area occurs only in the neighboring cell 82, it can be expected that the reception quality in the dead area exceeds the predetermined quality standard by the transmission of the femtocell base station 1. For this reason, the deterioration of the communication quality of the mobile station 6 can be suppressed.
- the femtocell base station 1 can use the neighboring cell reception quality at the position of the subordinate mobile station 6 for the transmission stop determination of the radio communication unit 10. For this reason, the femtocell base station 1 can accurately determine whether or not the subordinate mobile station 6 can communicate with the neighboring base station 7 when transmission is stopped. For example, if the neighboring cell 82, femtocell base station 1 and mobile station 6 in this embodiment are in the same positional relationship as the macro cell 92, femtocell base station 93 and mobile station 95 shown in FIG. Since the reception quality of neighboring cells at the station 6 is not sufficient, the transmission of the femtocell base station 1 can be continued. Therefore, it is possible to prevent the mobile station 6 from communicating with any base station.
- the femtocell base station 1 may stop transmission. This is because the influence on the coverage is small. Therefore, the femtocell base station 1 can determine its own stop while maintaining the coverage combined with the neighboring cell 82. Moreover, power consumption can be reduced by stopping.
- the femtocell base station 1 itself may measure the reception quality of neighboring cells. In this case, the femtocell base station 1 stops the transmission of the femtocell base station 1 when both the neighboring cell reception quality at the mobile station position and the neighboring cell reception quality at the installation location of the femtocell base station 1 are good. The transmission of the femtocell base station 1 may be continued when the reception quality of either one is lower than the reference.
- the transmission power adjustment procedure shown in FIG. 4 can be realized by causing a computer such as a microprocessor to execute a program for base station control. That is, the computer that executes the base station control program may be configured to refer to the measurement value of the neighboring cell reception quality, compare with a predetermined threshold value, and determine whether or not transmission power can be reduced (including whether or not to stop).
- FIG. 6 is a block diagram illustrating a configuration example of the femtocell base station 1 according to the present embodiment.
- the transmission control unit 11 shown in FIG. 6 has a function of measuring the reception quality of neighboring cells by the femtocell 81 itself in addition to the function of the transmission control unit 11 of FIG.
- the measurement report acquisition unit 111 receives the measurement report from the mobile station 6 decoded by the wireless communication unit 10.
- the measurement unit 112 measures the reception quality of a radio signal (for example, a pilot signal) that reaches the radio communication unit 10 from the neighboring cell 82.
- the stop determination unit 113 determines the transmission stop of the radio communication unit 10 using the neighbor cell reception quality measured by the mobile station 6 and the neighbor cell reception quality measured by the femtocell base station 1 (measurement unit 112). To do.
- the transmission control unit 114 controls the wireless communication unit 10 according to the determination result by the stop determination unit 113.
- the transmission control unit 114 may reduce the transmission power of the radio communication unit 10 by a certain amount, or may stop transmission of all radio signals including pilot signals.
- FIG. 7 is a flowchart showing a specific example of the transmission power control procedure of the femtocell base station 1 according to the present embodiment.
- FIG. 7 shows a case where received power is measured as a specific example of the reception quality of neighboring cells.
- Steps S ⁇ b> 201 and S ⁇ b> 202 relate to transmission control using neighboring cell reception quality at the installation location of the femtocell base station 1.
- the measurement unit 112 measures the received power P1 (i) of the N neighboring cells 82 (where i is an integer from 1 to N). When only radio waves arriving from one neighboring cell 82 can be received, the measuring unit 112 may measure the one neighboring cell 82.
- radio waves arriving from a plurality of neighboring cells 82 when radio waves arriving from a plurality of neighboring cells 82 can be received, all of them may be measured, or a predetermined number of neighboring cells 82 may be measured. Further, the measurement unit 112 may measure the neighboring cell 82 whose received power is equal to or higher than a predetermined reference.
- step S202 the stop determination unit 113 selects a maximum value from the N received powers P (i) to P (N) obtained for the N neighboring cells 82 to be measured, and uses this as a threshold value. Compare with B.
- the threshold value B may be the same as or different from the threshold value A for the neighboring cell reception quality (received power P2 in this case) measured by the mobile station 6.
- the stop determination unit 113 continues the transmission of the wireless communication unit 10 (step S206).
- stop determination unit 113 proceeds to step S203.
- Steps S203 to S207 in FIG. 7 are the same as the procedure shown in FIG. 5 except that the neighboring cell received power is specifically used as the neighboring cell reception quality.
- the transmission power may be reduced as compared with the case of continuous transmission (S206) without stopping the transmission of the wireless communication unit 10.
- the transmission power reduction of the wireless communication unit 10 may be performed in stages.
- FIG. 8 is a flowchart showing a specific example of the procedure for measuring and reporting the reception quality of neighboring cells by the mobile station 6.
- FIG. 8 shows a case where received power is measured as a specific example of the reception quality of neighboring cells.
- the measurement unit 61 receives a measurement instruction from the femtocell base station 1 via the wireless communication unit 60.
- the measurement instruction may include information on the transmission frequency of the measurement report and transmission in timing.
- the measurement unit 61 measures the received power P2 (i) of the wireless signal that reaches from the M neighboring cells 82 (where i is an integer from 1 to M).
- the measuring unit 61 may measure the one neighboring cell 82.
- the measurement unit 61 may measure all the neighboring cells, or may measure a predetermined number of neighboring cells 82. Good. Further, the measurement unit 61 may measure a neighboring cell 82 whose received power is equal to or higher than a predetermined reference.
- step S303 the reporting unit 62 reports the measurement result of the received power P2 (i) by the measuring unit 61 to the femtocell base station 1 through the wireless communication unit 60.
- the femtocell base station 1 continues transmission when at least one of the neighboring cell reception quality measured by the mobile station 6 and the neighboring cell reception quality measured by itself is not sufficient. That is, in addition to the coverage situation of the mobile station position by the neighboring cell 82, the coverage situation of the installation location of the femtocell base station 1 by the neighboring cell 82 is also considered, so that the coverage of the neighboring cell 82 can be determined more accurately.
- the mobile station 6 described in the present embodiment may be a wireless terminal that does not have mobility.
- the overall configuration of the radio communication system according to the present embodiment may be the same as the configuration shown in FIG.
- the femtocell base station 1 determines the coverage of the neighboring cell 82 using the measurement result of the neighboring cell reception quality.
- the mobile station 6 performs part of the coverage determination of the neighboring cell 82.
- the mobile station 6 determines whether or not the mobile station 6 is located in a place that is not covered by the neighboring cell 82 and is only covered by the femtocell 81, and sends a message including the determination result to the femtocell base station 1. Send.
- the femtocell base station 1 finally determines whether to reduce transmission power or stop transmission based on the message contents reported from the plurality of mobile stations 6.
- the mobile station 6 described in the present embodiment may be a wireless terminal that does not have mobility.
- Steps S401 and S402 in FIG. 9 are the same as steps S301 and S302 in FIG.
- the reporting unit 62 selects the maximum value from the received power P2 (i) measured for the M neighboring cells 82, and compares this with the threshold value A.
- the measurement unit 61 may measure the received power P (i) for each of the M neighboring cells a plurality of times.
- the reporting unit 62 calculates the representative value of the received power P (i) for each of the M neighboring cells, and selects the maximum value from the plurality of representative values calculated for each of the plurality of neighboring cells.
- the representative value may be an X percentage value calculated using a plurality of reception quality measurements, or may be another statistical value such as a minimum value or an average value.
- the reporting unit 62 creates a message (control information) that the femtocell base station may be stopped (step S404). This is because when the belonging femtocell base station 1 stops, it can belong to the neighboring cell 82 and it is considered that the mobile station 6 itself does not affect the coverage. Note that the reporting unit 62 may create a transmission stop message with a content that is gradually reduced by a certain amount until the transmission power is stopped.
- the reporting unit 62 creates a message (control information) requesting continued transmission of the femtocell base station 1 ( Step S405).
- the content of the transmission continuation message may be, for example, a request for continuation of transmission with the same transmission power.
- the reception quality of the radio signal from the femtocell base station 1 in the mobile station 6 exceeds a predetermined standard
- the content of the transmission continuation message decreases the transmission power. It may be a request to continue transmission. In the latter case, the mobile station 6 may measure the femtocell reception quality.
- the maximum value is selected from the received power P (i).
- the minimum value may be selected, or another statistical value such as an average value may be used. .
- Steps S501 and S502 in FIG. 10 are steps related to measurement of reception quality of neighboring cells by the femtocell base station 1 itself. These steps are the same as steps S201 and S202 of FIG. 7 described in the second embodiment.
- step S503 the transmission control unit 11 performs the process of step S503 to further determine whether or not transmission can be stopped. That is, in step S503, the measurement report acquisition unit 111 receives a message (control information) created by the mobile station 6 belonging to the femtocell 81. The stop determination unit 113 totals the received messages.
- step S504 the stop determination unit 113 compares the number of transmission stop messages included in the tabulated messages with a predetermined threshold C. This threshold determination may be performed on the ratio of the transmission stop message to the previous message. When the number of transmission stop messages is equal to or less than the threshold value C, the stop determination unit 113 determines to continue transmission (step S505). On the other hand, when the number of transmission stop messages exceeds the threshold C, the stop determination unit 113 determines transmission stop (step S506).
- a procedure for detecting a dead area that is not sufficiently covered by the neighboring cell 82 using the measurement result of the neighboring cell reception quality by the mobile station 6. May be appropriately shared between the femtocell base station 1 and the mobile station 6.
- ⁇ Embodiment 4 of the Invention> a transmission power control method of the femtocell base station 1 that uses the reception quality of the femtocell 81 at the mobile station point in addition to the reception quality of the neighboring cell 82 at the mobile station point will be described. Thereby, it is possible to suppress interference from the femtocell 81 to the neighboring cell 82 while maintaining the coverage.
- the overall configuration of the wireless communication system according to the present embodiment may be the same as the configuration shown in FIG.
- the mobile station 6 of this embodiment measures the neighboring cell reception quality and the femtocell reception quality.
- FIG. 11 is a flowchart showing a specific example of the operation of the mobile station 6.
- the neighboring cell received power P2 (i) is measured as the neighboring cell received quality
- the femtocell received power P_femto is measured as the femtocell received quality.
- P_femto is the received power of a radio signal (such as a pilot signal) transmitted from the femtocell base station 1.
- the measurement unit 61 receives a measurement instruction from the femtocell base station 1 via the wireless communication unit 60.
- the measurement instruction may include information on the transmission frequency and transmission timing of the measurement report.
- the measurement unit 61 measures the received power P2 (i) of the radio signal reaching from the M neighboring cells 82 (where i is an integer from 1 to M).
- the measuring unit 61 may measure the one neighboring cell 82.
- the measurement unit 61 may measure all the neighboring cells, or may measure a predetermined number of neighboring cells 82. Good. Further, the measurement unit 61 may measure a neighboring cell 82 whose received power is equal to or higher than a predetermined reference.
- step S603 the measurement unit 61 measures the received power P_femto of the radio signal reaching from the femtocell 81.
- step S604 the report unit 62 reports the measurement results of the received power P2 (i) and P_femto by the measurement unit 61 to the femtocell base station 1 through the radio communication unit 60.
- FIG. 12 is a flowchart showing a specific example of the transmission power control procedure of the femtocell base station 1 according to the present embodiment.
- the difference between the femtocell received power P_femto measured by the mobile station 6 and the neighboring cell received power P2 (i) is used for transmission power adjustment of the femtocell base station 1 will be described.
- step S701 the transmission control unit 11 receives femtocell received power P_femto and neighboring cell received power P2 (i) from the mobile station 6 belonging to the femtocell 81. Note that the transmission control unit 11 may receive the difference between P_femto and P2 (i) from the mobile station 6.
- step S702 the transmission control unit 11 determines the amount of transmission power reduction using the difference between the femtocell received power P_femto and the neighboring cell received power P2 (i).
- step S703 the transmission control unit 11 controls the wireless communication unit 10 so as to reduce the transmission power by the determined reduction amount.
- Procedure (1-1) First, among the results measured at different times and different mobile station positions by one or more mobile stations 6, P2 (i) exceeds a predetermined quality criterion (threshold A) and P_femto is P2 (I) For the above, the difference between P_femto and P2 (i) is calculated.
- the representative value of the difference may be, for example, a value (Y is an arbitrary number between 0 and 100) at which the cumulative probability becomes Y percent when the differences are arranged in ascending order.
- the representative value may be a minimum value of at least one difference calculated in the procedure (1-1).
- the representative value may be another statistical value such as an average value of at least one difference calculated in the procedure (1-1).
- the determination of the representative value of the difference in the procedure (1-2) may be appropriately determined according to whether priority is given to suppressing interference from the femtocell 81 to the neighboring cell 82 or ensuring the coverage.
- the representative value of the difference is set to the minimum value, the transmission power reduction amount of the femtocell base station 1 is small. For this reason, although the interference suppression effect is moderate, it is easy to maintain the coverage of the femtocell 81 and the peripheral cell 82 together.
- the difference representative value is set to the maximum value, the suppression of interference becomes significant, but the coverage may be temporarily lost.
- the average value or the Y percent value is used as the representative value of the difference, an intermediate effect can be obtained. Note that, when any representative value is selected, it is possible to obtain appropriate coverage by repeating the transmission power adjustment procedure.
- 13 and 14 are graphs showing the state of interference suppression when the minimum value included in a plurality of differences is selected as the representative value in the above procedure (1-2).
- the horizontal axis of the graph in FIG. 13 indicates the position of the mobile station 6, and the vertical axis indicates the received power at the mobile station 6.
- the solid line graph of FIG. 13 shows the femtocell received power P_femto at the mobile station position.
- the one-dot chain line graph of FIG. 13 shows the neighboring cell received power P2 (i) at the mobile station position.
- FIG. 14 shows a case where the minimum value ⁇ 1 of the four differences is selected as a representative value, and the transmission power of the femtocell base station 1 is reduced by ⁇ 1.
- control for increasing the transmission power of the femtocell base station 1 may be further performed.
- a specific example of a method for determining the increase amount of transmission power is shown below.
- the representative value of the difference may be, for example, a value (Y is an arbitrary number between 0 and 100) at which the cumulative probability becomes Y percent when the differences are arranged in ascending order.
- the representative value may be the maximum value of at least one difference calculated in the procedure (2-1).
- the representative value may be another statistical value such as an average value of at least one difference calculated in the procedure (2-1).
- Procedure (2-3) Based on the representative value of the difference determined in the procedure (2-2), the transmission power of the femtocell base station 1 is increased. Specifically, the transmission power may be increased by the difference value. Thereby, a dead area can be reduced and the coverage which combined the femtocell 81 and the peripheral cell 82 can be improved.
- FIG. 15 and FIG. 16 are graphs showing the state of coverage improvement when the maximum value included in a plurality of differences is selected as a representative value in the above steps (2-2) to (2-3).
- FIG. 16 shows a case where the maximum value ⁇ 4 among the four differences is selected as a representative value, and the transmission power of the femtocell base station 1 is increased by ⁇ 4.
- the femtocell to the area covered by the peripheral cell 82 is improved while improving the combined coverage of the femtocell 81 and the peripheral cell 82, as is apparent from FIG.
- the overhang of 81 can be suppressed. In other words, unnecessary overlapping at the cell boundary between the femtocell 81 and the peripheral cell 82 can be suppressed, and the cell boundary can be matched.
- Procedure (3-1) First, P2 (i) is below a predetermined quality standard (threshold A) among the results measured at different times and different mobile station positions by one or more mobile stations 6, and P_femto is a predetermined value. For those that exceed the quality criterion (threshold A), the difference between P_femto and the quality criterion (threshold A) is calculated.
- the representative value of the difference may be, for example, a value (Y is an arbitrary number between 0 and 100) at which the cumulative probability becomes Y percent when the differences are arranged in ascending order.
- the representative value may be the minimum value of at least one difference calculated in the procedure (3-1).
- the representative value may be another statistical value such as an average value of at least one difference calculated in the procedure (3-1).
- Procedure (3-3) Based on the representative value of the difference determined in the procedure (3-2), the transmission power of the femtocell base station 1 is reduced. Specifically, the transmission power may be reduced by the difference value representative value. Thereby, the interference from the femtocell 81 to the peripheral cell 82 can be suppressed while maintaining the coverage of the femtocell 81 and the peripheral cell 82 together. For example, when an unregistered mobile station exists in the vicinity of the femtocell base station 1, the unregistered mobile station performs wireless communication with the neighboring cell 82. According to the present embodiment, it is possible to suppress interference from the femtocell 81 to an unregistered mobile station.
- FIG. 17 and 18 are graphs showing the state of interference suppression when the minimum value included in a plurality of differences is selected as a representative value in the above procedure (3-2).
- FIG. 18 shows a case where the minimum value ⁇ 5 of the four differences is selected as a representative value, and the transmission power of the femtocell base station 1 is reduced by ⁇ 5.
- At least one of the femtocell base station 1 and the peripheral base station 7 may support service provision in a plurality of frequency bands (frequency channels).
- the service provision in a plurality of frequency bands (frequency channels) includes a frequency hopping technique and a dual cell technique for providing a communication service in two cells having different frequency channels.
- the measurement of the neighboring cell reception quality and the femtocell reception quality in the mobile station 6 and the measurement of the neighboring cell reception quality in the femtocell base station 1 may be performed for each frequency channel.
- the transmission power adjustment of the femtocell base station 1 may be performed for each frequency channel using the measurement result for each frequency channel. Thereby, even if the signal propagation characteristic has frequency dependence, the transmission power of the femtocell base station 1 can be accurately adjusted.
- the femtocell base station 1 may stop the transmission of the femtocell base station 1 when the reception quality of any one of a plurality of frequency channels exceeds the threshold A. Further, for example, in Embodiments 4 and 5 capable of suppressing interference with neighboring cells, measurement results of neighboring cell received power at the mobile station position for the same frequency channel as the frequency channel used by the femtocell base station 1 are obtained. It may be used to determine the increase / decrease amount of the transmission power of the femtocell base station 1.
- the configuration of the femtocell base station 1 described in the first to sixth embodiments of the present invention is an example, and other configurations are possible.
- the stop determination using the measurement report of the mobile station 6 may be executed by a device arranged in the upper network of the femtocell base station 1, for example, an RNC (Radio Network Controller).
- the stop determination unit 113 may be arranged in the RNC.
- the stop determination unit 113 arranged in the RNC may receive the measurement report of the neighboring cell reception quality from the femtocell base station 1 and perform the stop determination.
- the transmission control unit 114 may be arranged in the RNC similarly to the stop determination unit 113.
- the transmission control unit 114 arranged in the RNC according to the determination result of the stop determination unit 113 may create a transmission power control instruction and transmit it to the femtocell base station 1.
- the reception power measurement, stop determination, and transmission power control of the femtocell base station 1 can be arbitrarily shared between the femtocell base station 1 and the upper network to which the femtocell base station 1 is connected.
- Embodiments 1 to 7 of the invention described above can be applied to various wireless communication systems including the W-CDMA system, the E-UTRA system, and IEEE 802.16m.
- the femtocell base station 1 measures the reception quality of the neighboring cells.
- the femtocell base station 1 does not have to measure the neighboring cell reception quality.
- the transmission power control of the femtocell base station 1 described in the first to seventh embodiments of the invention is performed by other base stations other than the femtocell base station, for example, a pico base station that covers a wider area than the femtocell base station, You may apply to a micro base station and a macro base station.
- the procedure for adjusting the transmission power of the femtocell base station 1 described in the second to seventh embodiments of the invention is the same as that described in the first embodiment of the invention. You may implement
- 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.
- Femtocell base station 6 Wireless terminal (mobile station) 7 peripheral base station 10 wireless communication unit 11 transmission control unit 111 measurement report reception unit 112 measurement unit 113 stop determination unit 114 transmission control unit 60 wireless communication unit 61 measurement unit 62 reporting unit 81 femtocell 82 peripheral cell
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Abstract
Description
フェムトセル基地局がW-CDMAで使用される場合は、上りリンクと下りリンクにおける送信電力制御された個別チャネルを用いたデータ送信や、下りリンクにおける共用チャネルを用いたデータ送信が行われる。
フェムトセル基地局がE-UTRAで使用される場合は、基地局に配置されたスケジューラが物理リソースブロック(PRB;Physical Resource Block)の割当を行ない、割り当てられたPRBを用いたデータ送信が行われる。PRBは、OFDMA(Orthogonal Frequency Division Multiple Access)を採用するE-UTRAの下りリンクにおける無線リソースの基本単位であり、周波数領域で複数のOFDMサブキャリアを含み、時間領域で少なくとも1つのシンボル時間を含む。
また、IEEE 802.16mの下りリンクにもOFDMAが採用されている。フェムトセル基地局がIEEE 802.16mで使用される場合は、基地局に配置されたスケジューラがサブキャリアの割当を行ない、割り当てられたサブキャリアを用いたデータ送信が行われる。
(a)周辺セルから到達する周辺セル信号の受信品質の少なくとも1つの移動局による測定結果を取得すること、及び
(b)前記測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る移動局位置において、前記少なくとも1つの移動局との間で無線通信を行う基地局から送信される自セル信号の受信品質が第2の基準を上回るように、前記自セル信号の送信電力を制御すること。
(a)周辺セルから到達する周辺セル信号の受信品質の少なくとも1つの移動局による測定結果を取得すること、及び
(b)前記測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る移動局位置において、前記少なくとも1つの移動局との間で無線通信を行う基地局から送信される自セル信号の受信品質が第2の基準を上回るように、前記自セル信号の送信電力を制御すること。
図1は、本実施の形態にかかる無線通信システムの構成例を示す図である。本実施の形態にかかる無線通信システムは、少なくとも一台のフェムトセル基地局1、少なくとも一台の無線端末6、及び少なくとも一台の周辺基地局7を含む。フェムトセル基地局1は、フェムトセル81を形成し、無線端末6との間で無線通信を行う。周辺基地局7は、周辺セル82を形成する。周辺基地局7は、例えば、マクロセルを形成する基地局(マクロセル基地局)である。無線端末6は、フェムトセル基地局1と通信可能であり、周辺基地局7から送信される無線信号を受信可能な端末である。無線端末6は、例えば、携帯電話端末等の移動局、固定的に設置された固定端末を含む。なお、以下では、無線端末6は移動局であるとして説明を行う。フェムトセル基地局1が、特定の端末グループ(CSG:Closed Subscriber Group)のみに接続を許可するアクセス制限を行う場合、移動局6は、アクセス許可されたCSGに含まれる「登録移動局」とすればよい。
本実施の形態では、移動局6に加えてフェムトセル基地局1自身も周辺セル受信品質を測定する例について説明する。なお、本実施の形態の無線通信システムの全体構成は、実施の形態1に関して図1に示した構成と同様とすればよい。図6は、本実施の形態にかかるフェムトセル基地局1の構成例を示すブロック図である。図6に示す送信制御部11は、図2の送信制御部11が有する機能に加えて、フェムトセル81自身による周辺セル受信品質の測定機能を有する。
本実施の形態では、上述した実施の形態2の変形例について説明する。本実施の形態の無線通信システムの全体構成は、実施の形態1に関して図1に示した構成と同様とすればよい。上述した実施の形態2では、周辺セル受信品質の測定結果を用いた周辺セル82のカバレッジの判定をフェムトセル基地局1が行う例を示した。これに対して本実施の形態では、この周辺セル82のカバレッジの判定の一部を移動局6が行う例について説明する。すなわち、本実施形態では、周辺セル82によってカバーされずフェムトセル81によってのみカバーされる場所に位置しているか否かを移動局6が判定し、判定結果を含むメッセージをフェムトセル基地局1に送信する。フェムトセル基地局1は、複数の移動局6から報告されたメッセージ内容に基づいて、最終的に送信電力の低減や送信の停止の実施を判断する。
本実施の形態では、移動局地点における周辺セル82の受信品質に加えて、移動局地点におけるフェムトセル81の受信品質を利用するフェムトセル基地局1の送信電力制御方法について説明する。これにより、カバレッジを維持しながらフェムトセル81から周辺セル82への干渉を抑制することが可能となる。なお、本実施の形態の無線通信システムの全体構成は、実施の形態1に関して図1に示した構成と同様とすればよい。
手順(1-1):
初めに、1又は複数の移動局6によって異なる時間および異なる移動局位置にて測定された結果のうち、P2(i)が所定の品質基準(閾値A)を超えており、かつ、P_femtoがP2(i)以上であるものについて、P_femtoとP2(i)の差分を計算する。
次に、手順(1-1)で計算された少なくとも1つの差分の代表値を決定する。差分の代表値は、例えば、差分を小さい順に並べたときに累積確率がYパーセントとなる値(Yは0~100の間の任意の数)としてもよい。また、代表値は、手順(1-1)で計算された少なくとも1つの差分の最小値としてもよい。また、代表値は、手順(1-1)で計算された少なくとも1つの差分の平均値等の他の統計値としてもよい。
手順(1-2)で決定された差分の代表値に基づいて、フェムトセル基地局1の送信電力を低減する。具体的には、差分の代表値の分だけ送信電力を低減してもよい。これにより、フェムトセル81と周辺セル82との重複が抑制される。したがって、フェムトセル81及び周辺セル82をあわせたカバレッジを維持しながら、フェムトセル81から周辺セル82への干渉を抑制できる。例えば、フェムトセル基地局1の近隣に非登録移動局が存在する場合、非登録移動局は周辺セル82と無線通信を行う。本実施の形態によれば、フェムトセル81から非登録移動局への干渉を抑制できる。
手順(2-1):
初めに、1又は複数の移動局6によって異なる時間および異なる移動局位置にて測定された結果のうち、P2(i)及びP_femtoがともに所定の品質基準(閾値A)を下回っているものについて、品質基準(閾値A)とP_femtoの差分を計算する。
次に、手順(2-1)で計算された少なくとも1つの差分の代表値を決定する。差分の代表値は、例えば、差分を小さい順に並べたときに累積確率がYパーセントとなる値(Yは0~100の間の任意の数)としてもよい。また、代表値は、手順(2-1)で計算された少なくとも1つの差分の最大値としてもよい。また、代表値は、手順(2-1)で計算された少なくとも1つの差分の平均値等の他の統計値としてもよい。
手順(2-2)で決定された差分の代表値に基づいて、フェムトセル基地局1の送信電力を増加する。具体的には、差分の代表値の分だけ送信電力を増加してもよい。これにより、不感エリアを減少させ、フェムトセル81と周辺セル82を合わせたカバレッジを改善できる。
本実施の形態では、フェムトセル81から周辺セル82への干渉を抑制することが可能なフェムトセル基地局1の送信電力制御手順の他の例について説明する。上述の実施の形態4では、P_femtoとP2(i)の差分に基づいて、フェムトセル基地局1の送信電力低減量を決める例を示した。本実施の形態では、P_femtoと品質基準(閾値A)との差分に基づいてフェムトセル基地局1の送信電力低減量を決める例を説明する。
初めに、1又は複数の移動局6によって異なる時間および異なる移動局位置にて測定された結果のうち、P2(i)が所定の品質基準(閾値A)を下回っており、かつP_femtoが所定の品質基準(閾値A)を上回っているものについて、P_femtoと品質基準(閾値A)の差分を計算する。
次に、手順(3-1)で計算された少なくとも1つの差分の代表値を決定する。差分の代表値は、例えば、差分を小さい順に並べたときに累積確率がYパーセントとなる値(Yは0~100の間の任意の数)としてもよい。また、代表値は、手順(3-1)で計算された少なくとも1つの差分の最小値としてもよい。また、代表値は、手順(3-1)で計算された少なくとも1つの差分の平均値等の他の統計値としてもよい。
手順(3-2)で決定された差分の代表値に基づいて、フェムトセル基地局1の送信電力を低減する。具体的には、差分の代表値の分だけ送信電力を低減してもよい。これにより、フェムトセル81及び周辺セル82をあわせたカバレッジを維持しながら、フェムトセル81から周辺セル82への干渉を抑制できる。例えば、フェムトセル基地局1の近隣に非登録移動局が存在する場合、非登録移動局は周辺セル82と無線通信を行う。本実施の形態によれば、フェムトセル81から非登録移動局への干渉を抑制できる。
上述した発明の実施の形態1~5では、フェムトセル基地局1及び周辺基地局7のうち少なくとも1つは、複数の周波数帯域(周波数チャネル)でのサービス提供をサポートしてもよい。複数の周波数帯域(周波数チャネル)でのサービス提供には、周波数ホッピング技術や、周波数チャネルの異なる2つのセルで通信サービスを提供するデュアルセル技術も含まれる。この場合、移動局6における周辺セル受信品質およびフェムトセル受信品質の測定、並びにフェムトセル基地局1における周辺セル受信品質の測定を周波数チャネルごとに実施してもよい。そして、フェムトセル基地局1の送信電力調整を、周波数チャネル毎の測定結果を用いて周波数チャネル毎に行えばよい。これにより、信号伝搬特性に周波数依存性が存在する場合であっても、フェムトセル基地局1の送信電力を正確に調整することができる。
上述した発明の実施の形態1~6で述べたフェムトセル基地局1の構成は一例であり、それ以外の構成も可能である。例えば、移動局6の測定報告を用いた停止の判定は、フェムトセル基地局1の上位ネットワークに配置された装置、例えばRNC(Radio Network Controller)によって実行されてもよい。この場合、停止判定部113はRNCに配置すればよい。RNCに配置された停止判定部113は、周辺セル受信品質の測定報告をフェムトセル基地局1から受信し、停止の判定を実施すればよい。また、送信制御部114も停止判定部113と同様にRNCに配置してもよい。すなわち、停止判定部113の判定結果に応じてRNCに配置された送信制御部114が送信電力の制御指示を作成し、フェムトセル基地局1に送信してもよい。このように、受信電力の測定、停止判定、及びフェムトセル基地局1の送信電力制御は、フェムトセル基地局1とこれが接続される上位ネットワークとの間で任意に分担させることが可能である。
上述した発明の実施の形態1~7は、W-CDMA方式、E-UTRA方式、IEEE 802.16mを含む多様な無線通信システムに適用可能である。
6 無線端末(移動局)
7 周辺基地局
10 無線通信部
11 送信制御部
111 測定報告受信部
112 測定部
113 停止判定部
114 送信制御部
60 無線通信部
61 測定部
62 報告部
81 フェムトセル
82 周辺セル
Claims (44)
- 第1の無線信号を送信する第1の基地局と、
第2の無線信号を送信する第2の基地局と、
前記第1及び第2の無線信号を受信可能な少なくとも1つの無線端末と、
前記少なくとも1つの無線端末による前記第1の無線信号の受信品質の測定結果に基づき、前記第1の無線信号の受信品質が第1の基準を下回る無線端末位置において、前記第2の無線信号の受信品質が第2の基準を上回るように、前記第2の基地局による前記第2の無線信号の送信電力を制御する制御手段と、
を備える無線通信システム。 - 前記制御手段は、前記第1の無線信号の受信品質が前記第1の基準を上回る無線端末位置において、前記第2の無線信号の受信品質が前記第1の無線信号の受信品質以下となるように、前記第2の無線信号の送信電力を制御する、請求項1に記載の無線通信システム。
- 前記少なくとも1つの無線端末は、前記第1の無線信号に加えて前記第2の無線信号の受信品質の測定を行うよう構成され、
前記制御手段は、前記少なくとも1つの無線端末によって測定された前記第1の無線信号の受信品質と前記第2の無線信号の受信品質の差分に基づいて、前記第2の無線信号の送信電力を制御する、請求項1又は2に記載の無線通信システム。 - 前記差分は、前記第1の無線信号の受信品質が前記第1の基準を上回り、かつ前記第2の無線信号の受信品質が前記第1の無線信号の受信品質を上回る少なくとも1つの無線端末位置に関して計算され、
前記制御手段は、前記差分に応じて前記第2の無線信号の送信電力を低減するよう制御する、請求項3に記載の無線通信システム。 - 前記制御手段は、
前記第1の無線信号の受信品質が前記第1の基準を上回り、かつ前記第2の無線信号の受信品質が前記第1の無線信号の受信品質を上回る少なくとも1つの無線端末位置における受信品質の差分の複数の計算値を集計して得られる代表値を求め、
前記代表値に応じて前記第2の無線信号の送信電力を低減するよう制御する、請求項3に記載の無線通信システム。 - 前記代表値は、前記複数の計算値の最大値、最小値、平均値、又はXパーセント値(ただし、Xは0以上、100以下の数値)である、請求項5に記載の無線通信システム。
- 前記制御手段は、前記第1の無線信号の受信品質が前記第1の基準を上回る無線端末位置において、前記第2の無線信号の受信品質が前記第2の基準以下とように、前記第2の無線信号の送信電力を制御する、請求項1に記載の無線通信システム。
- 前記制御手段は、前記少なくとも1つの無線端末によって測定された複数の測定値の中から、前記第1の無線信号の受信品質が前記第1の基準以上かつ前記第1の基準に最も近い測定値を選び、その無線端末地点における前記第2の無線信号の受信品質が前記第1の無線信号の受信品質に近づくように、前記第2の無線信号の送信電力を制御する、請求項1又は2に記載の無線通信システム。
- 前記制御手段は、前記第1の無線信号の受信品質が前記第1の基準と等しくなる無線端末位置における、前記第2の無線信号の受信品質と前記第2の基準との差に応じて、前記第2の無線信号の送信電力を制御する、請求項1に記載の無線通信システム。
- 前記制御手段は、前記第1の無線信号の受信品質が前記第1の基準を下回る無線端末位置において、前記第2の無線信号の受信品質が前記第2の基準に近づくように前記第2の無線信号の送信電力を制御する、請求項1又は2に記載の無線通信システム。
- 前記制御手段は、前記少なくとも1つの無線端末によって測定された複数の測定値の中から、前記第1の無線信号の受信品質が前記第1の基準以下かつ前記第1の基準に最も近い測定値を選び、その無線端末地点における前記第2の無線信号の受信品質が前記第2の基準に近づくように、前記第2の無線信号の送信電力を制御する、請求項10に記載の無線通信システム。
- 前記制御手段は、前記少なくとも1つの無線端末によって測定された前記第1の無線信号の受信品質の複数の測定値を集計して得られる代表値が前記第1の基準を上回る場合に、前記第2の無線信号の送信を停止するように前記第2の基地局を制御する、請求項1に記載の無線通信システム。
- 前記第2の無線信号の送信停止は、段階的に送信電力を低減することにより行われる、請求項12に記載の無線通信システム。
- 前記制御手段は、前記代表値が前記第1の基準を下回る場合に、前記第2の無線信号の送信が継続されるよう前記第2の基地局を制御する、請求項12又は13に記載の無線通信システム。
- 前記代表値は、前記複数の測定値の最大値、最小値、平均値、又はXパーセント値(ただし、Xは0以上、100以下の数値)である、請求項12~14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、前記少なくとも1つの無線端末によって測定された前記第1の無線信号の受信品質の複数の測定値の中に前記第1の基準を下回る測定値が含まれることを条件として、前記第2の無線信号の出力が継続されるよう前記第2の基地局を制御する、請求項1に記載の無線通信システム。
- 前記第1の基地局は、複数の基地局を含み、
前記少なくとも1つの無線端末の各々は、前記複数の基地局から送信される複数の第1の無線信号の受信品質を測定し、
前記制御手段は、前記複数の基地局のうち前記少なくとも1つの移動局における前記第1の無線信号の受信品質が最も良好と推定される1の基地局を決定し、前記1の基地局に関する前記第1の無線信号の測定結果を前記第2の無線信号の送信電力制御に使用する、請求項1~16のいずれか1項に記載の無線通信システム。 - 前記少なくとも1つの無線端末は、前記第1の無線信号の受信品質に基づいて前記第2の無線信号の送信電力の調整要否を示す制御情報を送信し、
前記制御手段は、前記制御情報に基づいて前記第2の無線信号の送信電力を制御する、請求項1に記載の無線通信システム。 - 前記制御情報は、前記第2の無線信号の送信継続を示し、
前記少なくとも1つの無線端末は、前記第1の無線信号の受信品質が前記第1の基準を下回る場合に前記制御信号を送信する、請求項18に記載の無線通信システム。 - 前記制御情報は、前記第2の無線信号の送信停止を示し、
前記少なくとも1つの無線端末は、前記第1の無線信号の受信品質が前記第1の基準を上回る場合に前記制御信号を送信する、請求項18に記載の無線通信システム。 - 前記制御手段は、前記少なくとも1つの無線端末から送信される複数の前記制御情報を集計し、前記制御情報の集計結果に基づいて前記第2の無線信号の送信電力を制御する、請求項18~20のいずれか1項に記載の無線通信システム。
- 前記第1の基地局は複数の周波数チャネルを使用し、前記第1の無線信号は前記複数の周波数チャネルの各々において送信され、
前記制御手段は、前記複数の周波数チャネルで送信される複数の前記第1の無線信号のうち少なくとも1つの信号の受信品質の測定結果に基づいて、前記第2の無線信号の送信を制御する、請求項1~21のいずれか1項に記載の無線通信システム。 - 前記第1の基地局は複数の周波数チャネルを使用し、前記第1の無線信号は前記複数の周波数チャネルの各々において送信され、
前記制御手段は、前記複数の周波数チャネルで送信される複数の前記第1の無線信号のうち、前記第2の無線信号と同一の周波数チャネルで送信される1つの信号の受信品質の測定結果に基づいて前記第2の無線信号の送信を制御する、請求項1~21のいずれか1項に記載の無線通信システム。 - 前記第2の基地局は、前記第1の無線信号の受信品質を測定可能に構成され、
前記制御手段は、前記少なくとも1つの無線端末によって測定された前記第1の無線信号の受信品質又はこれらの代表値が前記第1の基準を下回る場合、または、前記第2の基地局によって測定された前記第1の無線信号の測定結果が第3の基準を下回る場合に、前記第2の無線信号の送信が継続されるよう前記第2の基地局を制御する、請求項1に記載の無線通信システム。 - 前記第2の基地局は、前記第1の無線信号の受信品質を測定可能に構成され、
前記制御手段は、前記少なくとも1つの無線端末によって測定された前記第1の無線信号の受信品質又はこれらの代表値が前記第1の基準を上回る場合、かつ、前記第2の基地局によって測定された前記第1の無線信号の測定結果が第3の基準を上回る場合に、前記第2の無線信号の送信を停止するように前記第2の基地局を制御する、請求項1に記載の無線通信システム。 - 前記第1の無線信号の受信品質は、前記第1の無線信号の受信電力を含む、請求項1~25のいずれか1項に記載の無線通信システム。
- 前記第2の基準は、前記第1の基準と同じ値である、請求項1~26のいずれか1項に記載の無線通信システム。
- 前記少なくとも1つの無線端末は、前記第1及び第2の基地局との間で無線による双方向通信が可能な移動無線局、予め設置された位置で前記第1及び第2の無線信号を受信する固定無線局を含む、請求項1~27のいずれか1項に記載の無線通信システム。
- 少なくとも1つの移動局との間で無線通信を行う無線通信手段と、
前記無線通信部の送信電力を制御する制御手段と、
を備え、
前記制御手段は、周辺セルから到達する周辺セル信号の前記少なくとも1つの移動局による受信品質の測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る無線端末位置において、前記無線通信手段から送信される自セル信号の受信品質が第2の基準を上回るように、前記無線通信手段による前記自セル信号の送信電力を制御する、
基地局装置。 - 前記制御手段は、前記周辺セル信号の受信品質が前記第1の基準を上回る移動局位置において、前記自セル信号の受信品質が前記周辺セル信号の受信品質以下となるように、前記自セル信号の送信電力を制御する、請求項29に記載の基地局装置。
- 前記少なくとも1つの移動局は、前記第1の無線信号に加えて前記第2の無線信号の受信品質の測定を行うよう構成され、
前記制御手段は、前記少なくとも1つの移動局によって測定された前記周辺セル信号の受信品質と前記自セル信号の受信品質の差分に基づいて、前記自セル信号の送信電力を制御する、請求項29又は30に記載の基地局装置。 - 前記差分は、前記周辺セル信号の受信品質が前記第1の基準を上回り、かつ前記自セル信号の受信品質が前記周辺セル信号の受信品質を上回る少なくとも1つの移動局位置に関して計算され、
前記制御手段は、前記差分に応じて前記自セル信号の送信電力を低減するよう制御する、請求項31に記載の基地局装置。 - 前記制御手段は、
前記周辺セル信号の受信品質が前記第1の基準を上回り、かつ前記自セル信号の受信品質が前記周辺セル信号の受信品質を上回る少なくとも1つの移動局位置における受信品質の差分の複数の計算値を集計して得られる代表値を求め、
前記代表値に応じて前記自セル信号の送信電力を低減するよう制御する、請求項31に記載の基地局装置。 - 前記制御手段は、前記周辺セル信号の受信品質が前記第1の基準を上回る移動局位置において、前記自セル信号の受信品質が前記第2の基準以下となるように、前記第2の無線信号の送信電力を制御する、請求項29に記載の基地局装置。
- 前記制御手段は、前記周辺セル信号の受信品質が前記第1の基準と等しくなる移動局位置における、前記自セル信号の受信品質と前記第2の基準との差に応じて、前記自セル信号の送信電力を制御する、請求項29に記載の基地局装置。
- 前記制御手段は、前記周辺セル信号の受信品質が前記第1の基準を下回る移動局位置において、前記自セル信号の受信品質が前記第2の基準に近づくように前記自セル信号の送信電力を制御する、請求項29又は30に記載の基地局装置。
- 前記制御手段は、前記少なくとも1つの移動局によって測定された複数の測定値の中から、前記周辺セル信号の受信品質が前記第1の基準以下かつ前記第1の基準に最も近い測定値を選び、その移動局地点における前記自セル信号の受信品質が前記第2の基準に近づくように、前記自セル信号の送信電力を制御する、請求項36に記載の基地局装置。
- 前記制御手段は、前記少なくとも1つの移動局によって測定された前記周辺セル信号の受信品質の複数の測定値を集計して得られる代表値が前記第1の基準を上回る場合に、前記自セル信号の送信を停止するように前記無線通信手段を制御する、請求項29に記載の基地局装置。
- 前記自セル信号の送信停止は、段階的に送信電力を低減することにより行われる、請求項38に記載の基地局装置。
- 前記制御手段は、前記代表値が前記第1の基準を下回る場合に、前記自セル信号の送信が継続されるよう前記無線通信手段を制御する、請求項38又は39に記載の基地局装置。
- 前記無線通信手段は、前記周辺セル信号の受信品質を測定可能に構成され、
前記制御手段は、前記少なくとも1つの移動局によって測定された前記周辺セル信号の受信品質又はこれらの代表値が前記第1の基準を上回る場合、かつ、前記無線通信手段によって測定された前記周辺セル信号の測定結果が第3の基準を上回る場合に、前記自セル信号の送信を停止するように前記無線通信手段を制御する、請求項29に記載の基地局装置。 - 周辺セルから到達する周辺セル信号の受信品質の少なくとも1つの移動局による測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る移動局位置において、前記少なくとも1つの移動局との間で無線通信を行う基地局から送信される自セル信号の受信品質が第2の基準を上回るように、前記自セル信号の送信電力を制御する制御手段を備える基地局制御装置。
- 周辺セルから到達する周辺セル信号の受信品質の少なくとも1つの移動局による測定結果を取得すること、及び
前記測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る移動局位置において、前記少なくとも1つの移動局との間で無線通信を行う基地局から送信される自セル信号の受信品質が第2の基準を上回るように、前記自セル信号の送信電力を制御すること、
を備える基地局の送信電力制御方法。 - 移動局との間で無線通信を行う基地局機器に関する制御処理をコンピュータに実行さ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、
前記制御処理は、
周辺セルから到達する周辺セル信号の受信品質の少なくとも1つの移動局による測定結果を取得すること、及び
前記測定結果に基づき、前記周辺セル信号の受信品質が第1の基準を下回る移動局位置において、前記少なくとも1つの移動局との間で無線通信を行う基地局から送信される自セル信号の受信品質が第2の基準を上回るように、前記自セル信号の送信電力を制御すること、
を備えるコンピュータ可読媒体。
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CN201080056109.7A CN102648655B (zh) | 2009-12-08 | 2010-11-24 | 无线电通信系统、基站装置、基站控制装置、控制基站发送功率的方法以及计算机可读介质 |
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US13/514,455 US8805398B2 (en) | 2009-12-08 | 2010-11-24 | Radio communication system, base station apparatus, base station control apparatus, method of controlling transmission power of base station, and computer readable medium |
JP2011545062A JP5720578B2 (ja) | 2009-12-08 | 2010-11-24 | 無線通信システム、基地局装置、基地局制御装置、基地局の送信電力制御方法、及びプログラム |
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JPWO2011070733A1 (ja) | 2013-04-22 |
CN102648655B (zh) | 2015-04-15 |
EP2512191A1 (en) | 2012-10-17 |
US20120252479A1 (en) | 2012-10-04 |
US8805398B2 (en) | 2014-08-12 |
KR20140113707A (ko) | 2014-09-24 |
JP5720578B2 (ja) | 2015-05-20 |
KR101507529B1 (ko) | 2015-04-07 |
KR20120091261A (ko) | 2012-08-17 |
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CN102648655A (zh) | 2012-08-22 |
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