JP5857723B2 - COMMUNICATION SYSTEM, COMMUNICATION METHOD, AND BASE STATION - Google Patents

Description

  The present case relates to a communication system, a communication method, and a base station.

  In recent years, with the rapid spread of smartphones and the like, the communication amount of mobile stations has increased. Therefore, communication carriers are considering introducing LTE (Long Term Evolution) as the amount of communication increases.

  In LTE, OFDMA (Orthogonal Frequency Division Multiple Access) is scheduled to be adopted in the downlink. OFDMA is a technique in which a plurality of mobile stations share subcarriers, and each mobile station allocates subcarriers with the highest transmission efficiency.

  The mobile station can use the most efficient subcarrier each time by OFDMA. Furthermore, the communication carrier can improve the frequency utilization efficiency.

  Further, there is one-cell frequency repetition as a countermeasure technique against an increase in communication amount. Since different frequencies are not allocated between adjacent base stations in one-cell frequency repetition, each base station can use all the frequency bands allocated to each operator. Therefore, 1-cell frequency repetition is an important technique for dealing with an increase in communication traffic.

  As described above, introduction of LTE and 1-cell frequency repetition are expected to provide high-speed data communication to mobile stations and support the ever-increasing mobile broadband demand.

  However, when 1-cell frequency repetition is applied to OFDMA, there is a possibility of causing interference in a cell overlap portion between adjacent base stations. Due to such interference, there is a problem that communication provided to the mobile station becomes slow.

  In order to solve the above problem, there is a technique called FFR (Fractional Frequency Reuse). FFR is a technology that prevents interference by dividing one frequency band and using different frequencies between adjacent base stations. Examples of FFR are given below.

  FIG. 1 is an example in which FFR is applied to an OFDMA cellular system (see, for example, Patent Document 1).

  As shown in FIG. 1, when FFR is applied to an OFDMA cellular system, each cell is divided into a priority channel and a non-priority channel, and the frequency band is divided into three.

  The frequency allocation of each cell will be described. The frequency is assigned so that the priority channel does not have the same frequency between adjacent cells. Then, a frequency other than the frequency assigned to the priority channel in each cell is assigned to the non-priority channel.

  For example, when the frequency F1 is assigned to the priority channel 11, the frequency F2 + F3 is assigned to the non-priority channel 12. The priority channel 13 is assigned a frequency F2, which is a different frequency from the priority channel 11, and the non-priority channel 14 is assigned F1 + F3.

  As described above, by assigning different frequencies to the priority channels between adjacent base stations, it is possible to reduce interference of cell overlapping portions between adjacent base stations.

JP2009-171288

  However, operators need a lot of additional investment to apply the above-described technology. Furthermore, even after application of the above-described technology, it is expected that the burden on the operator will increase every time the user's needs are met.

  Therefore, while satisfying mobile broadband demand, it is necessary to reduce the burden on operators.

  In the above-described technique, frequency allocation is designed so that each base station does not interfere. That is, each base station divides the frequency band by estimating the distance from the center.

  For example, as a result of estimating the distance from the mobile station, the base station can be found that the mobile station exists only in the central portion of the own station. Here, if the cell range is shortened by reducing the transmission power of each base station, the mobile station is not assigned to the priority channel. That is, the base station uses only the non-priority channel among all the allocated frequencies.

  As can be seen from the above, when the power is saved, the communication capacity decreases accordingly.

  One of the purposes of this case was created in view of such problems, and is to reduce the burden on the operator while maintaining the communication capacity.

  It should be noted that the present invention is not limited to the above-mentioned object, and it is also positioned as another object of the present case that the effects shown in the embodiments for implementing the invention to be described later are obtained and are not obtained by the prior art. be able to.

  In order to solve the above-described problem, the communication system according to the present disclosure allocates power information related to received power of a signal received from a base station to a mobile station according to the mobile station transmitting to the base station and the transmission power of the local station. An allocation condition for determining a frequency is set, and either the first frequency or the second frequency is set for the mobile station according to the power information received from the mobile station and the set allocation condition. And a base station to be allocated.

  Further, in order to solve the above problem, the communication method of the present disclosure sets an allocation condition for determining a frequency to be communicated according to the transmission power of the base station, and power related to the reception power of the signal received by the mobile station. One of the first frequency and the second frequency is selected according to the information and the allocation condition, and the base station and the mobile station communicate with each other at the selected frequency.

  In order to solve the above-described problem, the base station of the present disclosure includes a receiving unit that receives power information related to received power of a signal received by the mobile station from the mobile station, and an allocation for determining a frequency to be allocated to the mobile station. Depending on the setting unit that sets the condition according to the transmission power of the own station, the received power information, and the set allocation condition, the first frequency and the first frequency are set for the mobile station that is the transmission source of the power information. An allocating unit that allocates one of the two frequencies.

  According to the communication system, the communication method, and the base station disclosed in the present disclosure, it is possible to control the communication so that the frequency band is maintained regardless of the transmission power, thereby realizing the power saving and the maintenance of the communication capacity.

Diagram showing an example of applying FFR to an OFDMA cellular system Overall view of cellular system according to first embodiment Frequency allocation example of cellular system according to first embodiment Overview of the first embodiment Example of frequency boundary change of the first embodiment Functional block diagram / hardware configuration diagram of network management device according to first embodiment Functional block diagram / hardware configuration diagram of base station according to the first embodiment Example of determination table of cell boundary value of base station according to first embodiment Functional block diagram / hardware configuration diagram of mobile station according to the first embodiment The flowchart which shows the process and operation | movement of the mobile station which concerns on 1st Embodiment. The flowchart which shows the process and operation | movement of the base station which concerns on 1st Embodiment. Flowchart 1 showing the processing and operation of the base station and network management apparatus according to the first embodiment Flowchart 2 showing the processing and operation of the base station and network management apparatus according to the first embodiment The flowchart which shows the process and operation | movement of the mobile station which concerns on 2nd Embodiment. The flowchart which shows the process and operation | movement of the base station which concerns on 2nd Embodiment.

Hereinafter, embodiments of the disclosed communication system, communication method, and base station will be described with reference to the drawings. Configurations shown in the drawings of the following embodiments are examples, and the present invention is not limited to such configurations.
Each embodiment considers power saving of a base station with a low communication processing load as one method of reducing the burden on the operator. This can reduce the power consumption of the base station, so that not only the communication environment load can be reduced, but also the operation cost can be greatly reduced for the communication carrier.

<First Embodiment>
The first embodiment will be described with reference to FIGS.

  FIG. 2 is an overall view of the network according to the first embodiment.

  As shown in FIG. 2, when FFR is applied to an OFDMA cellular system, each cell is divided into a cell center region and a cell edge region by frequency allocation.

  First, the OFDMA frequency band is divided into three at the time of cell design and assigned to cell edge regions so that adjacent channels do not overlap. A frequency other than the frequency assigned to the cell edge region is assigned to the cell center region of each cell.

  For example, as shown in FIG. 3, it is assumed that the frequency f1 to f3 is divided. At this time, if the frequency f 1 is assigned to the cell edge region 21 a of the cell 21, the frequency f 2 is assigned to the cell edge region 22 a of the cell 22, and the frequency f 3 is assigned to the cell edge region 23 a of the cell 23. Further, the frequency f2 and the frequency f3 that are not assigned to the cell edge region 21a are assigned to the cell center region 21b of the cell 21. Similarly, the frequency f1 and the frequency f3 are assigned to the cell center region 22b, and the frequency f1 and the frequency f2 are assigned to the cell center region 23b.

  Referring to FIG. 3, it can be seen that the frequency of the cell edge region in each cell is different. Therefore, since the same frequency is not used in the cell edge region where the cells may overlap, it can be seen that no interference occurs even if FFR is applied to OFDMA.

Here, the boundary between the cell edge region and the cell center region will be described.
The cell radius is determined according to the magnitude of the transmission power of the reference signal of the base station. A mobile station existing in the vicinity of the base station has a large received power of a signal received from the base station. Similarly, a mobile station located far from the base station has a small reception power of a signal received from the base station. Utilizing these facts, the base station determines whether to allocate a cell center area frequency or a cell edge area frequency to the mobile station.

The base station sets a condition for the path loss value, and determines a frequency to be allocated to the mobile station according to the path loss value of the mobile station. Path loss is the difference between the transmission power of the base station and the reception power of the mobile station. For example, it is calculated using the following formula.

As described above, the cell formed by the base station according to the first embodiment divides the frequency band into the cell center region and the cell edge region.

  FIG. 4 is a schematic diagram of the first embodiment.

  The base station 41 and the base station 42 are controlled by a network management device described later. The operation of the base station described below is determined by the network management device. However, the service provider or the like may be changed via the network management device.

  As shown in FIG. 4, the base station 41 transitions from a normal operation to a dormant operation. For example, the operator causes the base station 41 to be suspended when the system of the base station 41 is updated or when the power of the base station 41 is saved.

  Referring to FIG. 5, when the base station 41 is in normal operation, the cell edge region between adjacent base stations uses different frequencies. Therefore, as shown in FIG. 4, the overlapping portion of the cells formed by the two base stations is the cell edge region of each base station. Therefore, since the frequencies of the cell edge regions are different, the two base stations do not cause interference.

  Hereinafter, the operation of the base station 41 will be described.

  The base station 41 controls the transmission power of the reference signal and reduces the entire cell. At this time, the base station 41 changes the condition at the boundary between the cell center region and the cell edge region. Thereby, even if the cell is reduced, the base station 41 can divide the frequency band into the cell center region and the cell edge region and communicate with the mobile station.

In addition, when it is determined that the base station 41 is suspended, the network management device controls the base stations 42 to cooperate. That is, the cell center region and the cell edge region of the base station 41 and the cell center region and the cell edge region of the base station 42 are operated in cooperation with each other.
By doing so, even if the base station 41 reduces the cell, the cells of the base station 41 and the base station 42 are kept in a state where only the cell edge regions overlap. Therefore, no interference occurs between the base station 41 and the base station 42. Furthermore, since the base station 41 and the base station 42 operate in cooperation, the base station 42 covers the range covered by the base station 41, and no dead zone occurs.
As described above, the mobile station 44 that is performing communication within the cell formed by the base station 41 is handed over to the base station 42 even if the base station 41 performs a dormant operation. Communication can be maintained.
In addition, the mobile station 43 exists in the cell center area before the base station 41 reduces the cell, but exists in the cell edge area after the base station 41 reduces the cell.
In addition, the base station 41 can know the approximate position of the mobile station by using the path loss notified from the mobile station. Therefore, the transmission power may be suppressed to a place where the mobile station is considered to exist, and the base station 42 may not cover.

  As a result, radio waves can be delivered only to the area where the mobile station exists, so that the base station can be operated with the minimum necessary power consumption.

  FIG. 6 is a hardware configuration diagram / function block diagram of the network management device according to the first embodiment.

  The network management device 60 according to the first embodiment controls the transmission power of each base station.

  The network management device 60 includes an interface unit 61, an operation management unit 62, an SP management unit 63, and a schedule management unit 64.

  The functional unit as described above is realized by a CPU or the like, for example.

  The interface unit 61 receives the traffic amount from each base station and outputs it to the operation management unit 62. Also, the changed SP (System Parameter) input from the operation management unit 62 is transmitted to the corresponding base station. For example, the changed SP includes reference signal transmission power, neighboring cell information, and the like. The base station that has received the changed SP changes each SP according to the changed SP.

  The operation management unit 62 controls the entire network management device 60. Various function units to be described later are controlled by the operation management unit 62. The operation management unit 62 outputs the traffic amount input from the interface unit 61 to the SP management unit 63. In addition, the operation management unit 62 outputs the operation schedule input from the schedule management unit 64 to the interface unit 61.

The SP management unit 63 creates and manages an SP for each base station. The SP management unit 63 determines a base station to be degenerated according to the traffic amount in each base station input from the operation management unit 62.
For example, the SP management unit 63 determines the base station with the smallest traffic volume as a degenerate base station. By degenerating base stations with a small amount of traffic, useless power consumption can be suppressed. When the base station to be degenerated is determined, the SP of the degenerate base station and the changed value of the SP of the base station that performs an emphasis operation with the base station are output to the schedule management unit 64 as the changed SP.

  Here, the base station to be degenerated is determined, but if necessary, the base station to be expanded may be determined or the base station for adjusting the cell range may be determined.

  The scheduling management unit 64 is a functional unit that schedules the operation of each base station, and creates an operation schedule for the corresponding base station based on the changed SP input from the SP management unit 63. The creation of the operation schedule will be described later.

  Thus, the network management device 60 can operate each base station in a coordinated manner. In addition, as described above, the cooperative operation may determine not to cover not only the configuration covered by the other base station when one of them degenerates. For example, if the location is allowed to be out of service, the base stations cooperate by saving power.

  FIG. 7 is a hardware configuration diagram / function block diagram of the base station according to the first embodiment.

  The base station 70 is a base station that communicates with a mobile station using the first frequency and the second frequency. Furthermore, every time the transmission power is changed, the base station 70 transmits information on the changed transmission power to the mobile station. Then, the base station 70 sets conditions for the first frequency and the second frequency according to the changed transmission power. Furthermore, the base station 70 assigns frequencies to the mobile stations according to the set conditions.

  The configuration of the base station 70 will be described.

  The base station 70 includes an antenna 71, an RF unit 72, a BB unit 73, and a CNT unit 74.

  The antenna 71 transmits a transmission signal output from the RF unit 72 using a radio wave as a medium, receives a signal transmitted from the mobile station using the radio wave as a medium, and outputs a reception signal to the RF unit 72.

  The RF (Radio Frequency) unit 72 is a functional unit that processes a high-frequency signal. The RF unit 72 includes a DUP unit 720, an LNA unit 721, an RF → BB signal conversion unit 722, a BB → RF signal conversion unit 723, and an AMP unit 724.

  The DUP (Duplexer) unit 720 is a circuit in which the transmission circuit and the reception circuit share the same antenna, outputs the reception signal input from the antenna 71 to the LNA unit 721, and transmits the transmission signal input from the AMP unit 724 to the antenna. Input to 71.

  An LNA (Low Noise Amplifier) unit 721 is a low noise amplifier circuit that amplifies extremely poor radio waves after reception without increasing noise as much as possible. The LNA unit 721 amplifies the signal input from the DUP unit 720 and outputs the amplified signal to the RF → BB signal conversion unit 722.

  An RF (Radio Frequency) → BB (BaseBand) signal converter 722 is a frequency converter, and converts a received signal into an intermediate frequency that is easy to process. Further, the RF → BB signal conversion unit 722 also performs A / D (Analog / Digital) conversion.

  The RF → BB signal conversion unit 722 converts the received signal input from the LNA unit 721 from an analog signal to a digital signal, further converts it to an intermediate frequency, and outputs the intermediate signal to the BB unit 73.

  The BB → RF signal conversion unit 723 is a circuit that raises the target frequency. Further, the BB → RF signal conversion unit 723 also performs D / A (Digital / Analog) conversion.

  The BB → RF signal conversion unit 723 converts the modulated transmission signal (digital signal) input from the BB unit 73 into an analog signal, raises it to a target frequency, and outputs it to the AMP unit 724.

  The AMP (Amplifier) unit 724 is a circuit that amplifies the transmission signal to a necessary level. The AMP unit 724 amplifies the transmission signal input from the BB → RF signal conversion unit 723 to a target level and outputs the amplified signal to the DUP unit 720.

  The BB (BaseBand) unit 73 is a functional unit that processes a baseband signal that is an intermediate frequency.

  The BB unit 73 includes a demodulation unit 730, a decoding unit 731, a PL data extraction unit 732, a PL calculation unit 733, an SP management unit 734, a cell region determination unit 735, a schedule management unit 736, and a radio resource allocation. Unit 737, an encoding unit 738, and a modulation unit 739.

  The demodulator 730 is a circuit that performs demodulation in order to extract a target data signal. The demodulator 730 demodulates the digital signal input from the RF unit 72 and outputs the demodulated signal to the decoder 731.

  The decoding unit 731 is a circuit for decoding an encoded data signal based on a certain rule and extracting the original data. The decoding unit 731 is a demodulated digital signal input from the demodulation unit 730. Is output to the PL data extraction unit 732.

  A PL (Pass Loss) data extraction unit 732 is controlled by an operation management unit 740, which will be described later, and extracts information (hereinafter referred to as PL information) related to the path loss notified from the mobile station from the digital signal. The PL data extraction unit 732 extracts PL information from the digital signal input from the decoding unit 731, and outputs the extracted PL information to the PL calculation unit 733.

The PL information is, for example, PH (Power Headroom), and the mobile station calculates PH from the PL calculated by the mobile station and notifies PH to the base station.

The PL data calculation unit 733 is controlled by an operation management unit 740 to be described later, and estimates the PL of the mobile station using the PL information extracted by the PL data extraction unit 732.

  The PL data calculation unit 733 calculates the PL based on the PL information input from the PL data extraction unit 732. For example, if the PL information is PH, the path loss can be calculated by the calculation formula (2).

  Therefore, the PL data calculation unit 733 requests the SP management unit 734 for information on the maximum transmission power and the current transmission power of the base station 70, the PH input from the PL data extraction unit 732, and the SP management unit 734. The path loss calculated by the above equation using the input maximum transmission power and the current transmission power is output to the cell region determination unit 735.

  The PL data calculation unit 733 outputs the PL calculated by the above formula to the SP management unit 734 and the cell region determination unit 735.

  An SP (System Parameter) management unit 734 is a functional unit that is controlled by an operation management unit 740, which will be described later, and manages all SPs necessary for system operation. The SP includes, for example, an ID, frequency, timer, channel setting, power setting, and the like in the base station 70.

  Further, the SP management unit 734 determines the boundary between the cell center region and the cell edge region of the cell formed by the base station 70 based on the current transmission power and the maximum transmission power in the base station 70 (PL ( Thereafter, the boundary PL value) is periodically updated.

For example, the boundary PL value can be calculated by updating the table shown in FIG. The boundary PL value can be calculated by the following formula.


Further, the SP management unit 734 outputs the SPs in response to requests from the PL calculation unit 733, the cell region determination unit 735, and the scheduling management unit 736, respectively.

  For example, the SP management unit 734 outputs the maximum transmission power of the reference signal and the current transmission power to the PL calculation unit 733. The SP management unit 734 outputs the boundary PL value to the cell region determination unit 735. Then, the SP management unit 734 outputs an SP necessary for scheduling such as frequency and power setting to the schedule management unit 736.

The cell region determination unit 735 is a functional unit that is controlled by an operation management unit 740 to be described later and determines the cell region of the mobile station based on the boundary PL value and the PL estimation value in the mobile station.
When the PL in the mobile station is input from the PL data calculation unit 733, the cell area determination unit 735 requests information on the boundary PL value from the SP management unit 734.
When a boundary PL value is input from the SP management unit 734, the boundary PL value input from the SP management unit 734 is compared with the PL input from the PL data calculation unit 733, and the cell in which the mobile station exists is compared. It is determined whether the area is a cell edge area or a cell center area. Then, the cell region determination unit 735 outputs the determination result to the scheduling management unit 736. The cell region determination method will be described later with reference to the flowchart of FIG.

  This makes it possible to determine whether the mobile station that has transmitted the signal exists in the cell center region or the cell edge region in the own cell.

The scheduling management unit 736 is a functional unit that determines radio resource allocation. When a determination result is input from the cell region determination unit 735, a radio resource used for communication with the mobile station based on the determination result Make assignments.
That is, when the mobile station exists in the cell center area, the schedule management unit 736 causes the mobile station to use radio resources in the cell center area. When the mobile station exists in the cell edge area, the schedule management unit 736 Use radio resources in the area.
When the schedule management unit 736 determines which of the two frequencies is used for communication, the schedule management unit 736 determines radio resource allocation and outputs the determined radio resource information to the radio resource allocation unit 737.

  In LTE, OFDMA is used for the downlink, and resource units (RB) surrounded by a frequency axis and a time axis are allocated to different users for radio resources. That is, the scheduling function unit 736 determines which RB (Resource Block) to allocate and outputs the determined resource block to the radio resource allocation unit 737.

The radio resource allocation unit 737 is a functional unit that executes radio resource allocation instructed by the scheduling management unit 736.
When radio resource information is input from the scheduling management unit 736, radio resource allocation is executed based on the radio resource information. When the schedule management unit 736 executes radio resource allocation, the schedule management unit 736 outputs a transmission signal for the mobile station to the encoding unit 738.

  The encoding unit 738 encodes the transmission signal input from the radio resource allocation unit 737 according to a certain rule. Then, encoding section 738 outputs the encoded transmission signal to modulating section 739.

  The modulation unit 739 is a circuit that puts information to be transmitted on a radio wave, modulates the transmission signal input from the encoding unit 738, and outputs the modulated transmission signal to the RF unit 73.

  A CNT (Control) unit 74 controls and manages the entire base station 70.

  The CNT unit 74 includes an operation management unit 740 and an interface unit 741.

  The operation management unit 740 performs monitoring control of the base station. For example, when the base station 70 is installed, control is performed so that each function unit is activated, or when each base unit 70 is stopped, control is performed so that each function unit is stopped. It also manages whether various functional units are operating normally.

  Then, the operation of the base station 70 is managed according to the changed SP output from the interface unit 741. For example, the operation management unit 740 changes the transmission power of the reference signal. When the transmission power of the reference signal is changed, the operation management unit 740 performs control so as to notify the current transmission power by broadcast information or the like.

  Furthermore, the operation management unit 740 calculates the traffic volume in the own station. The calculation amount of the traffic amount may be data obtained by tabulating the number of users using radio resources in the own station in time units. The operation management unit 740 outputs the aggregated traffic volume to the interface unit 741.

  The interface unit 741 outputs the traffic volume at the base station 70 to the network management device. At this time, the interface unit 741 may periodically transmit the traffic amount to the network management device, or may transmit the traffic amount in response to a request from the network management device. Also, the change parameter input from the network management device is output to the operation management unit 740.

  With the above configuration, the base station can control transmission power in cooperation with neighboring base stations. Furthermore, the mobile station can be scheduled according to the transmission power to be changed.

  FIG. 9 is a hardware configuration diagram / functional block diagram of the mobile station according to the first embodiment.

  When the mobile station 90 receives the reference signal from the base station, the mobile station 90 transmits PH to the base station.

  As shown in FIG. 9, the mobile station 90 includes an antenna 91, an RF unit 92, a BB unit 93, and a CNT unit 94.

  For example, the antenna 91 transmits a transmission signal output from the RF unit 92 using a radio wave as a medium, receives a signal transmitted from the base station using a radio wave as a medium, and outputs the received signal to the RF unit 92. To do.

  The RF unit 92 is a functional unit that processes high-frequency signals. The RF unit 92 includes a DUP unit 920, an LNA unit 921, an RF → BB signal conversion unit 922, an RSRP measurement unit 923, a BB → RF signal conversion unit 924, and an AMP unit 925.

  The DUP unit 920 is a circuit in which a transmission circuit and a reception circuit share the same antenna. The DUP unit 920 outputs a reception signal input from the antenna 91 to the LNA unit 921 and inputs a transmission signal input from the AMP unit 925 to the antenna 91. To do.

  The LNA unit 921 amplifies the reception signal input from the DUP 920 unit and outputs the amplified signal to the RF → BB signal conversion unit 922.

  The RF → BB signal conversion unit 922 converts the reception signal input from the LNA unit 921 into an intermediate frequency, further converts the analog signal into a digital signal, and outputs the converted signal to the BB unit 93 and the RSRP measurement unit 923.

  An RSRP (Reference Signal Received Power) measurement unit 923 measures received power of a reference signal received from a base station. When a digital signal is input from the RF → BB signal conversion unit 922, the RSRP measurement unit 923 extracts a reference signal from the digital signal and measures received power of the reference signal. Then, the measurement result is output to the BB unit 93.

  The BB → RF signal conversion unit 924 converts the transmission signal input from the BB unit 93 from a digital signal to an analog signal, increases the frequency to a target frequency, and outputs the signal to the AMP unit 925.

  The AMP unit 925 amplifies the transmission signal input from the BB → RF signal conversion unit 924 to a target level and outputs the amplified signal to the DUP unit 920.

  The BB unit 93 is a functional unit that processes a baseband signal that is an intermediate frequency.

  The BB unit 93 includes a demodulation unit 930, a decoding unit 931, an SP data extraction unit 932, an SP management unit 933, a PL calculation unit 934, a schedule management unit 935, a radio resource allocation unit 936, and an encoding unit. 937 and a modulator 938.

  The demodulator 930 demodulates the digital signal input from the RF unit 92 and outputs the demodulated signal to the decoder 931. The decoding unit 931 decodes the demodulated digital signal input from the demodulation unit 930 and outputs it to the SP data extraction unit 932.

  An SP (System Parameter) data extraction unit 932 is controlled by an operation management unit 940, which will be described later, and extracts a SP (ID, frequency, transmission power of a reference signal, etc. in a communicating base station) from a received signal. The SP notified from the base station is extracted from the received signal. It is assumed that the base station is transmitting the transmission power of the current reference signal with broadcast information.

  The SP data extraction unit 932 extracts the SP from the digital signal input from the decoding unit 931 and outputs the extracted SP to the SP management unit 933.

  The SP management unit 934 is controlled by an operation management unit 940, which will be described later, and manages SP (ID, frequency, transmission power of a reference signal in a base station that performs communication) required when the mobile station 90 performs communication. It is a functional part to do.

  The SP management unit 934 updates the SP of the base station that is performing communication based on the SP input from the SP data extraction unit 932. The SP management unit 934 outputs the SP in response to requests from the PL calculation unit 634 and the schedule management unit 635, respectively.

  The PL calculation unit 934 is controlled by an operation management unit 940, which will be described later, and calculates the PL from the transmission power of the reference signal at the base station with which communication is performed and the reception power of the reference signal at the local station. The PL calculation unit 934 calculates the PL based on the transmission power of the reference signal of the base station input from the SP data extraction unit 932 and the reception power of the reference signal input from the RF unit 92 (RSRP measurement unit 923). To do. For example, PL can be calculated by using equation (1).

Furthermore, the PL calculation unit 934 calculates PH from the calculated PL using equation (2).
Then, the calculated PH is output to the SP management unit 933 and the schedule management unit 935.

  The scheduling management unit 935 is a functional unit that determines allocation of radio resources used by the mobile station 90 for communication. When a PH is input from the PL calculation unit 934, the scheduling management unit 935 requests SP information from the SP management unit 933. . And according to the request | requirement, the radio | wireless resource used for communication of the mobile station 90 is determined based on SP input from SP management part 933. The determined radio resource information is output to radio resource allocation section 936.

  When the radio resource information is input from the scheduling management unit 935, the radio resource allocation unit 936 performs radio resource allocation. When the radio resource allocation is executed, the radio resource allocation unit 936 outputs the transmission signal to the encoding unit 937.

  The encoding unit 937 encodes the transmission signal output from the radio resource allocation unit 936 and outputs the encoded transmission signal to the modulation unit 938. The modulation unit 938 modulates the transmission signal input from the encoding unit 937 and outputs the modulated transmission signal to the RF unit 92.

  The CNT unit 94 controls and manages the entire mobile station 90.

  The CNT unit 94 includes an operation management unit 940.

  The operation management unit 940 is a functional unit that performs monitoring control of the mobile station, and controls and manages various functional units in the mobile station 90.

  With the above mobile station configuration, even if the base station changes the transmission power of the reference signal, it is possible to obtain an SP such as the current transmission power from the base station. You can be notified.

  FIG. 10 is a flowchart showing operations and processing when the mobile station according to the present embodiment notifies the base station of the PL.

The RSRP measurement unit 923 of the mobile station 90 measures the received power of the reference signal received from the base station 70 and outputs it to the PL calculation unit 934. (S101)
The PL calculation unit 934 calculates the PL for the base station 70 by performing the following processing. (S102)
The mobile station 90 acquires information on the transmission power of the current reference signal from the base station 70 using broadcast information or the like. Then, PL is calculated based on the received power of the reference signal input from the RSRP measurement unit 623 and the acquired transmission power of the reference signal.
PL = Reference signal transmission power−Reference signal reception power Next, the PL calculation unit 934 calculates PH (PowerHeadroom) in order to notify the base station of the calculated PL. It is known that path loss is generally converted to PH and notified to a base station. It can be calculated by using equation (2).

The PL calculation unit 934 outputs the calculated PH to the scheduling management unit 935. Then, the mobile station 90 notifies the base station of the PH using the radio resource determined by the scheduling manager 935. (S103)
Through the processing and operation as described above, the mobile station can notify the base station of the PL.

  FIG. 11 is a flowchart showing processing / operation in cell area determination of the base station according to the present embodiment.

  Hereinafter, a method in which the base station determines the cell area in which the mobile station exists based on the PH received from the mobile station will be described.

When the PH is input from the PL data extraction unit 732 (S111), the PL calculation unit 733 calculates the PL from the input PH. PL can be calculated by applying a value to equation (2). (S112)
On the other hand, the SP management unit 734 updates the SP based on the notification from the operation management unit 740. (S113)
When the operation management unit 740 receives the operation schedule from the network management device 60, the operation management unit 740 notifies the SP management unit 734 of the final reference signal transmission power indicated by the operation schedule.

The SP management unit 734 determines whether or not it is necessary to change a boundary PL value that is a condition of a boundary between the cell center region and the cell edge region in the SP. (S114)
If it is determined in step S114 that the boundary PL value needs to be corrected, the boundary PL value is calculated by the calculation formulas (3) and (4). (S115)
The boundary PL value needs to be corrected when the transmission power after execution of the schedule is compared with the current transmission power, and the boundary PL value is changed by a predetermined threshold value or more.

The SP management unit 734 updates the boundary PL value of the cell region table (see FIG. 8) to the calculated boundary PL value. (S116)
The cell region determination unit 735 compares the PL calculated from the PH notified from the mobile station 90 with the boundary PL value of the cell region table, so that the mobile station 90 exists in the cell edge region or the cell central region. Check if it exists. (S117)
If it is not necessary to correct the boundary PL value in step S84, the processing / operation of step S117 is performed without updating the boundary PL value.

  If it is determined in step S117 that the mobile station 90 exists in the cell edge region, the fact is output to the schedule management unit 736, and the mobile station 90 uses the frequency assigned to the cell edge region by the radio resource assignment unit 737. 90 radio resources are allocated.

  If it is determined in step S117 that the mobile station exists in the cell edge region, the fact is output to the schedule management unit 736, and the mobile station 90 uses the frequency allocated to the cell center region by the radio resource allocation unit 537. Allocate radio resources.

  According to the above flow, even when the base station according to the present embodiment controls the transmission power of the own station, the base station can change the cell boundary condition according to the control.

  12 and 13 are sequence diagrams illustrating operations and processing when the communication system according to the first embodiment performs a cooperative operation.

  First, a case where one base station transitions from normal operation to degenerate operation in the communication system according to the first embodiment will be described with reference to FIG.

Each of the base stations A to C operates the base station as usual. (S1201)
Then, the base station A monitors the situation at itself and reports the monitoring result to the network management device. An example of the monitoring result is traffic. Since the base station A knows the number of mobile stations connected to the base station A, it calculates traffic from the number of mobile stations and the like and reports it to the network management apparatus. (S1202)
Base station B and base station C also report their own monitoring results to the network management device. (S1203, S1204)
Base stations A to C share their cell states. The base stations A to C perform schedule control while checking the cell state between the base stations. The cell state is information such as an operation state, dormancy, expansion, and expansion, and each base station shares the cell state of each base station using the X2 interface. At this time, the cell states of the base stations A to C are “normal”. Therefore, the base stations A to C share that the cell state of each base station is “normal”. In addition, information may be distributed from a base station whose cell state has been changed to an adjacent base station. (S1205)
On the other hand, the network management apparatus receives periodic reports on the monitoring results of the base stations managed by the network management apparatus. For example, the report may be received at a periodic time, or the report may be received when the traffic situation in the base station changes significantly.

  When the network management device determines that the cell state of the base station needs to be changed, it creates an operation schedule. At this time, the network management device may determine that it is necessary to change the cell state when traffic is biased, or may determine based on the control of the operator or the like. In addition, it may be when a base station failure is detected. Also, the network management device determines which base station and how to change the cell state.

  For example, in the example shown in FIG. 12, it is assumed that the base station B is suspended. Accordingly, the base station A and the base station C expand the cell to cover the cell range of the base station B. At this time, when the traffic received from the base station B is extremely small, the network management apparatus can save power and reduce costs by suspending the base station B.

  Furthermore, the operation schedule is, for example, reference signal transmission power at the cell state transition start time and start time, and reference signal transmission power at the cell state transition end time and end time. Here, the reference signal for normal operation is determined for each base station by station design such as time transition prediction of load (mobile station) and area cover (reference signal adjustment, antenna tilt adjustment). The reference signal is changed based on the transmission power of the reference signal.

As described above, the network management device creates an operation schedule for each base station. (S1206)
The network management device transmits the created operation schedule to the base station A. (S1218)
Similarly, the network management apparatus transmits the created operation schedule to the base station B and the base station C. (S1208, S1209)
In the example of FIG. 12, the network management apparatus instructs the base station B to reduce the cell range, but the base station B does not change the cell state even though the cell state of the other base station has not changed. If this is reduced, a dead zone will occur until another base station expands the cell range. Therefore, first, it is desirable that the base station that has received an instruction to expand the cell range expands the cell range, and then the base station that reduces the cell range transitions the cell state. The network management apparatus can control the order of cell transition based on the start time and end time in the operation schedule.

Based on the operation schedule, the base station A changes the transmission power of the reference signal. Here, since the base station A extends the cell range, the transmission power of the reference signal is increased. (S1210)
Similarly, the base station C increases the transmission power of the reference signal in order to expand the cell. (S1211)
Here, each base station shares a cell state. Here, by sharing the cell state, the base station B can confirm whether or not the own station may be suspended. (S1212)
Next, since the base station A has changed the transmission power of the reference signal, it changes the cell boundary PL value used for the determination of the cell area. (S1213)
Similarly, the base station C also changes the cell boundary determination PL value. (S1214)
Each base station shares a cell state. Here, it can be confirmed that the transition has ended. (S1215)
Then, the base station B decreases the transmission power of the reference signal in order to reduce the cell according to the operation schedule, and finally pauses. (S1216)
Finally, when the cell state of each base station is confirmed, it can be seen that base station A and base station C are expanded and base station B is suspended. (S1217)
With the above flow, each base station can perform a cooperative operation under the control of the network management apparatus. Also, in the above description, the base station that expands the cell completes the cell transition, and then the base station that contracts the cell transitions the cell state, but it increases by 1 dB on the expansion side and decreases by 1 dB on the reduction side. It is also possible to carry out at the same time.

  The case where all base stations transition to the normal operation from the cell state at the end of the cooperative operation in FIG. 12 will be described using FIG.

Base station A and base station C are expanded and base station B is suspended. (S1301)
Then, the base station A monitors the situation at itself and reports the monitoring result to the network management device. (S1302)
Base station B and base station C also report their own monitoring results to the network management device. (S1303, S1304)
Base stations A to C share their cell states. (S1305)
On the other hand, the network management apparatus receives periodic reports on the monitoring results of the base stations managed by the network management apparatus.

When the network management device determines that the cell state of the base station needs to be changed, the network management device creates an operation schedule for each base station. (S1306)
The network management device transmits the created operation schedule to the base station A. (S1307)
Similarly, the network management apparatus transmits the created operation schedule to the base station B and the base station C. (S1308, S1309)
Based on the operation schedule, the base station B changes the transmission power of the reference signal. Here, since the base station B extends the cell range, the transmission power of the reference signal is increased. Further, the base station B returns to normal operation. The cell boundary PL value at this time is a boundary PL value during normal operation, and is set in advance, so it is not necessary to change it. (S1310)
If the change in the transmission power of the base station is not equal to or greater than the predetermined threshold, it is not necessary to correct the boundary PL value. However, as can be seen by referring to step S1310, the base station that has been completely suspended has When the operational status returns to, the boundary PL value does not need to be changed.

Here, each base station shares a cell state. (S1311)
Based on the operation schedule, the base station A changes the transmission power of the reference signal. (S1312)
Based on the operation schedule, the base station C changes the transmission power of the reference signal. (S1313)
Each base station shares a cell state. (S1314)
Next, since the base station A has changed the transmission power of the reference signal, the base station A changes the boundary PL value used for determining the cell region. (S1215)
Similarly, the base station C also changes the boundary PL value. (S1216)
Each base station shares a cell state. Here, it can be seen that each base station is in normal operation.

(S1217)
With the above flow, each base station can perform an emphasis operation under the control of the network management apparatus.

  According to the first embodiment, since the base station can determine the boundary of the cell region according to the current transmission power, even when the transmission power is controlled cooperatively between adjacent base stations, Cell region boundaries can be set.

Second Embodiment
The second embodiment will be described with reference to FIGS. 14 and 15. Here, except for FIG. 10 and FIG. 11 in the first embodiment, it is the same as that of the first embodiment, so that the description is omitted.

  The base station according to the second embodiment is different from the first embodiment in that it does not notify the mobile station even if the transmission power of the reference signal is changed.

  FIG. 14 is a flowchart showing operations and processing when the mobile station according to the second embodiment notifies the base station of the PL.

The RSRP measurement unit 923 of the mobile station 90 measures the received power of the reference signal received from the base station 70 and outputs it to the PL calculation unit 934. (S141)
The PL calculation unit 934 calculates the PL for the base station 70 by performing the following processing. (S142)
The mobile station 90 has already acquired the transmission power information of the reference signal from the base station 70 by the broadcast information or the like when the mobile station 90 is activated. Then, PL is calculated based on the received power of the reference signal input from RSRP measuring section 623 and the transmitted power of the acquired reference signal. Next, the PL calculation unit 934 calculates PH (PowerHeadroom) in order to notify the calculated PL to the base station. It is known that path loss is generally converted to PH and notified to a base station.

The PL calculation unit 934 outputs the calculated PH to the scheduling management unit 935. Then, the mobile station 90 notifies the base station of the PH using the radio resource determined by the scheduling manager 935. (S143)
Through the processing and operation as described above, the mobile station can notify the base station of the PL.

  FIG. 11 is a flowchart showing processing / operation in cell area determination of the base station according to the present embodiment.

  That is, a method will be described in which the base station determines the cell area where the mobile station exists based on the PH received from the mobile station.

  The PL calculation unit 733 receives PH from the PL data extraction unit 732 (S151).

When the operation management unit 740 receives the operation schedule from the network management device 60, the operation management unit 740 notifies the SP management unit 734 of the final reference signal transmission power indicated by the operation schedule.
The SP management unit 734 updates the SP based on the notification from the operation management unit 740. In addition, the SP management unit 734 notifies the PL calculation unit 733 of the SP update value. For example, this notifies the initial transmission power of the reference signal of the base station 70 and the final transmission power of the reference signal indicated by the operation schedule. (S152)
At this time, the initial transmission power value and the final transmission power value are compared, and when there is no need to correct the PL of the mobile station 70, it is not necessary to notify.

The PL calculation unit 733 determines that the correction of the PL notified from the mobile station 70 is necessary when the SP update value is notified from the SP management unit 734. (S153)
If it is determined in step S153 that PL correction is necessary, a PL correction value is calculated. The correction value of PL can be calculated by equation (3). (S154)
The PL calculation unit 733 calculates the PL from the input PH (using the expression (2)) and the calculated correction value of the PL (using the expression (4)). PL can be calculated by applying a value to the following equation. (S155)
In step S153, if it is not necessary to correct the PL, the PL is calculated from the input PH.

On the other hand, the SP management unit 734 determines whether or not it is necessary to change a boundary PL value that is a boundary condition between the cell center region and the cell edge region in the SP. (S156)
If it is determined in step S156 that the boundary PL value needs to be corrected, the boundary PL value is calculated by the equations (3) and (4). (S157)
The boundary PL value needs to be corrected when the transmission power after execution of the schedule is compared with the current transmission power, and the boundary PL value is changed by a predetermined threshold value or more.

The SP management unit 734 updates the boundary PL value of the cell region table (see FIG. 8) to the calculated boundary PL value. (S158)
The cell area determination unit 735 confirms whether the mobile station 90 exists in the cell edge area or the cell center area by comparing the calculated PL with the boundary PL value of the cell area table. (S159)
If it is not necessary to correct the boundary PL value in step S156, the processing / operation in step S159 is performed without updating the boundary PL value.

If it is determined in step S159 that the mobile station 90 exists in the cell edge region, the fact is output to the schedule management unit 736, and the mobile station 90 uses the frequency assigned to the cell edge region by the radio resource assignment unit 737. 90 radio resources are allocated. (S160)
If it is determined in step S159 that the mobile station exists in the cell edge region, the fact is output to the schedule management unit 736, and the mobile station uses the frequency allocated to the cell central region by the radio resource allocation unit 537. 90 radio resources are allocated. (S161)
With the above flow, even when the base station according to the present embodiment controls the transmission power of the own station, the base station condition can be changed according to the control.

According to the second embodiment, when the base station changes the transmission power, it is possible to appropriately perform frequency allocation to the mobile station without notifying the mobile station.

11.13 Preferred channel
12.14 Non-priority channels
21.22.23 Radio base station
21a.22a.23a Cell edge region
21b.22b.23b Cell center area
41.42 Base station
43.44 Mobile station
61 Interface section
62 Operation Management Department
63 SP Management Department
64 Schedule Management Department
70 base station
71.91 Antenna
72.92 RF section
73.93 BB Department
74.94 CNT section

Claims (5)

In a communication system having a base station that can use a first frequency and a second frequency,
A mobile station that transmits power information about received power of a signal received from the base station to the base station;
Depending on the change in the transmit power of the own station, and change the setting of the assignment condition for determining the frequency to be allocated to the mobile station, the power information received from the mobile station, and the assignment condition, in accordance with the movement A base station that assigns one of the first frequency and the second frequency to a station;
A communication system comprising: A management device for controlling the transmission power of the base station;
The base station
According to the control of the management device, change the transmission power of its own station,
The communication system according to claim 1 . The base station
Sending communication information about the traffic of its own station to the management device,
The management device
Determining transmission power of the base station based on communication information received from the base station;
The communication system according to claim 2 . In a base station that can use the first frequency and the second frequency,
A receiver that receives power information about the received power of a signal received by the mobile station from the mobile station;
A setting unit for changing an allocation condition for determining a frequency to be allocated to a mobile station according to a change in transmission power of the own station; and
An allocating unit that allocates one of the first frequency and the second frequency to a mobile station that is a transmission source of the power information according to the received power information and the allocation condition;
A base station characterized by comprising: In the communication method between the mobile station and the base station performed using either one of the first frequency and the second frequency,
Change the allocation condition for determining the frequency to communicate between the mobile station and the base station according to the change in the transmission power of the base station,
According to the power information related to the received power of the signal received by the mobile station and the allocation condition, select one of the first frequency and the second frequency,
Communicating with the base station and the mobile station at the selected frequency;
A communication method characterized by the above.