JP5471343B2 - Base station and quality measurement method - Google Patents

Description

  The present invention relates to a base station that communicates with a mobile terminal and a quality measurement method.

  In LTE (Long Term Evolution), also called Super3G, SRS (Sounding Reference Signal) that handles communication quality of uplink signals between a base station and a mobile terminal is used (for example, see Patent Document 1 below). The SRS is periodically mapped to a part of the uplink signal from the mobile terminal. Based on the received SRS, the base station performs communication quality calculation processing such as power measurement, interference measurement, fading estimation, and TA (Timing Adjustment) value.

JP 2008-177965 A JP 2009-060596 A

  However, in the above-described conventional technology, when the number of mobile terminals that measure communication quality in the base station increases, it becomes impossible to measure the communication quality within a specified time. For this reason, there is a problem that the number of mobile terminals that can be measured is limited by the processing amount that can be processed within a specified time, and communication quality cannot be measured efficiently.

  The disclosed base station and quality measurement method are intended to solve the above-described problems and to efficiently measure communication quality.

  In order to solve the above-described problems and achieve the object, the disclosed technology is configured to receive a reference signal transmitted from the mobile terminal in a base station that measures communication quality for each mobile terminal, and to convert the received reference signal into the received reference signal. On the basis of this, it is a requirement to periodically perform the measurement at the measurement interval set in the mobile terminal and set the measurement interval based on the measured communication quality.

  According to the disclosed base station and quality measurement method, it is possible to efficiently measure the communication quality.

1 is a block diagram showing a configuration of a base station according to a first exemplary embodiment. 3 is a flowchart showing an example of the operation of the base station shown in FIG. It is a block diagram which shows the structure of the base station concerning Embodiment 2. FIG. It is a figure which shows an example of the order of the process by the SRS process part shown in FIG. It is a block diagram which shows the structural example of the fd estimation process part shown in FIG. It is a flowchart which shows an example of the operation | movement by the fd estimation process part shown in FIG. It is FIG. (1) which shows the periodic fd estimation process by an fd estimation process part. It is FIG. (2) which shows the periodic fd estimation process by an fd estimation process part. It is FIG. (3) which shows the periodic fd estimation process by an fd estimation process part. It is FIG. (4) which shows the periodic fd estimation process by an fd estimation process part. It is a figure which shows the measurement interval of UE added newly. It is a figure which shows a process when fd estimated value of UE changes. FIG. 4 is a block diagram illustrating a configuration example of a TA calculation processing unit illustrated in FIG. 3. It is a flowchart which shows an example of the operation | movement by the TA calculation process part shown in FIG. It is FIG. (1) which shows the periodic TA calculation process by a TA calculation process part. It is FIG. (2) which shows the periodic TA calculation process by a TA calculation process part. It is FIG. (3) which shows the periodic TA calculation process by a TA calculation process part. It is FIG. (4) which shows the periodic TA calculation process by a TA calculation process part. It is a figure which shows the measurement interval of UE added newly. It is a figure which shows a process when TA value of UE changes. FIG. 6 is a block diagram illustrating a configuration of an fd estimation processing unit according to a third embodiment. It is a flowchart which shows an example of operation | movement of the fd estimation process part shown in FIG. FIG. 6 is a block diagram illustrating a configuration of a TA calculation processing unit according to a third embodiment. It is a flowchart which shows an example of operation | movement of the TA calculation process part shown in FIG. It is a figure which shows an example of the table memorize | stored in the table memory | storage part shown in FIG. 21 and FIG. It is a figure (the 1) which shows each threshold value change based on the number of UEs. It is a figure (the 2) which shows the change of each threshold value based on the number of UEs. It is a figure (the 3) which shows the change of each threshold value based on the number of UEs. FIG. 10 is a block diagram illustrating a configuration of an fd estimation processing unit according to a fourth embodiment. It is a flowchart which shows an example of the threshold value setting operation | movement of the fd estimation process part shown in FIG. FIG. 10 is a block diagram illustrating a configuration of a TA calculation processing unit according to a fourth embodiment. It is a flowchart which shows an example of the threshold value setting operation | movement of TA calculation process part shown in FIG. It is a figure which shows an example of the table memorize | stored in the table memory | storage part shown in FIG. 27 and FIG. It is a flowchart which shows an example of operation | movement of the fd estimation process part shown in FIG. It is a flowchart which shows an example of operation | movement of the TA calculation process part shown in FIG. It is a figure which shows the change of the measurement interval using a some threshold value.

  Exemplary embodiments of a disclosed base station and quality measurement method will be described below in detail with reference to the accompanying drawings. The disclosed base station and quality measurement method measure the communication quality periodically at a measurement interval set for each mobile terminal and set a relatively long measurement interval for a mobile terminal with a relatively high communication quality. Distribute processing temporally and efficiently measure communication quality.

(Embodiment 1)
FIG. 1 is a block diagram of the configuration of the base station according to the first embodiment. A communication system 100 illustrated in FIG. 1 is a system that performs wireless communication between a base station 110 and UE # 0 to UE # 2. UE # 0 to UE # 2 are mobile terminals capable of mobile communication such as mobile phones. The UEs # 0 to # 2 periodically transmit a reference signal (for example, SRS) for measuring communication quality in the base station 110 to the base station 110.

  The base station 110 measures communication quality for each UE. Specifically, the base station 110 includes a reception unit 111, a measurement unit 112, a comparison unit 113, and a setting unit 114. Hereinafter, the UEs to be processed by the reception unit 111, the measurement unit 112, the comparison unit 113, and the setting unit 114 among the UEs # 0 to # 2 are referred to as target UEs. The receiving unit 111 receives a reference signal transmitted from the target UE. The receiving unit 111 outputs the received reference signal to the measuring unit 112.

  The measuring unit 112 measures the communication quality of the target UE based on the reference signal output from the receiving unit 111. Specifically, the measurement interval is set by the setting unit 114 for each of the UE # 0 to UE # 2. The measurement unit 112 periodically measures the communication quality of the target UE at a measurement interval set for the target UE. The measurement of communication quality includes, for example, fading (hereinafter referred to as fd) estimation, TA value calculation, and the like. The measurement unit 112 outputs the measured communication quality to the comparison unit 113.

  The comparison unit 113 compares the communication quality output from the measurement unit 112 with the quality threshold value. The comparison unit 113 outputs the comparison result to the setting unit 114. The setting unit 114 sets a measurement interval based on the comparison result output from the comparison unit 113. Specifically, if the comparison unit 113 determines that the communication quality is less than the quality threshold, the setting unit 114 sets the first interval as the measurement interval of the target UE, and the communication quality is equal to or higher than the quality threshold. If determined, the second interval is set as the measurement interval of the target UE. The second interval is an interval longer than the first interval.

  Here, the configuration in which the communication quality measured by the measurement unit 112 is compared with the quality threshold value by the comparison unit 113 and the setting unit 114 sets the measurement interval based on the comparison result has been described. However, the configuration is not limited thereto. Absent. For example, the setting unit 114 may be configured to acquire the communication quality measured by the measurement unit 112 and set the measurement interval calculated using mathematical formulas or the like based on the acquired communication quality.

  FIG. 2 is a flowchart showing an example of the operation of the base station shown in FIG. Base station 110 performs each step shown, for example in FIG. 2 for each of UE # 0 to UE # 2. First, the measurement unit 112 determines whether or not the elapsed time from the previous communication quality measurement is the measurement interval of the target UE (step S201), and waits until the elapsed time reaches the measurement interval of the target UE (step S201: No loop).

  When the elapsed time reaches the measurement interval of the target UE in step S201 (step S201: Yes), the measurement unit 112 measures the communication quality of the target UE (step S202). Next, the comparison unit 113 compares the communication quality measured in step S202 with the quality threshold (step S203).

  Next, the setting unit 114 sets the measurement interval of the target UE based on the comparison result in step S203 (step S204), and returns to step S201. By performing the above steps for UE # 0 to UE # 2, it is possible to lengthen the measurement interval and distribute the measurement processing in time for UEs with relatively high communication quality (hereinafter referred to as load distribution). Can be called). When there are a plurality of communication qualities to be measured, for example, the above steps are performed for each communication quality to be measured.

  As described above, according to the base station 110 according to the first embodiment, for a UE having a relatively high measured communication quality, the measurement process is temporally distributed by increasing the measurement interval, and the frequency of the measurement process is changed. Can be lowered. Thereby, the time margin of the measurement process can be expanded and the communication quality can be measured efficiently. In addition, a UE having a relatively high communication quality has a lower probability that the communication quality changes abruptly than a UE having a relatively low communication quality. For this reason, it is possible to suppress deterioration in communication performance caused by reducing the frequency of measurement processing by reducing the frequency of measurement processing of UEs having relatively high communication quality.

(Embodiment 2)
(Base station configuration)
FIG. 3 is a block diagram of the configuration of the base station according to the second embodiment. A base station 300 illustrated in FIG. 3 is, for example, an S3G (Super 3G) base station (eNB, Evolved NodeB, or the like). Base station 300 communicates with UE # 0 to UE # 2.

<Configuration of base station DL>
In FIG. 3, the structure regarding DL (Down Link) of the base station 300 is demonstrated. As illustrated in FIG. 3, the base station 300 includes a wireless communication unit 301, a CNT unit 302, and a baseband processing unit 303. The wireless communication unit 301 includes an antenna, an amplifier, and the like, and transmits and receives signals to and from UE # 0 to UE # 2. For example, the radio communication unit 301 outputs UL (Up Link) reception data received from the UE # 0 to UE # 2 to the CNT unit 302. The UL received data includes, for example, SRS. Radio communication section 301 transmits the transmission data output from CNT section 302 to UE # 0 to UE # 2.

  The CNT unit 302 performs interface control of the base station 300. For example, the CNT unit 302 transmits UL reception data output from the wireless communication unit 301 to the IP network 350 and outputs it to the baseband processing unit 303. In addition, the CNT unit 302 outputs the transmission data output from the baseband processing unit 303 to the wireless communication unit 301.

  The baseband processing unit 303 performs baseband processing of signals. Specifically, the baseband processing unit 303 includes an IF control unit 304, a CP removal unit 305, a UL scheduler 306, a PUSCH processing unit 307, a PUCCH processing unit 308, a RACH processing unit 309, and an SRS processing unit. 310, a DL scheduler 311, and a DL processing unit 312.

  The IF control unit 304 controls input / output between the CNT unit 302 and the baseband processing unit 303. For example, the IF control unit 304 outputs the UL reception data output from the CNT unit 302 to the CP removal unit 305 and the UL scheduler 306. Further, the IF control unit 304 outputs allocation information output from the UL scheduler, transmission data output from the DL processing unit, and the like to the CNT unit 302.

  CP removing section 305 removes the CP (Cyclic Prefix) of UL received data output from IF control section 304. CP removing section 305 outputs the UL received data from which CP has been removed to PUSCH processing section 307, PUCCH processing section 308, RACH processing section 309, and SRS processing section 310.

  The UL scheduler 306 performs scheduling of UL communication of UE # 0 to UE # 2. For example, the UL scheduler 306 performs scheduling based on UL reception data from the IF control unit 304, processing results from the PUSCH processing unit 307, PUCCH processing unit 308, and RACH processing unit 309, and quality information from the SRS processing unit 310. I do.

  The UL scheduler 306 outputs the allocation information obtained by scheduling to the PUSCH processing unit 307, the PUCCH processing unit 308, and the SRS processing unit 310. The allocation information includes, for example, information on each UE that is scheduled by the UL scheduler 306. Further, the UL scheduler 306 outputs the quality information from the SRS processing unit 310 to the DL scheduler 311.

  The PUSCH processing unit 307 performs processing of PUSCH (Physical Up Shared Channel) such as payload processing, and outputs the processing result to the UL scheduler 306. The PUCCH processing unit 308 performs PUCCH (Physical Uplink Control Channel) processing such as scheduling and ACK / NACK processing, and outputs the processing result to the UL scheduler 306. The RACH processing unit 309 performs RACH (Random Access Channel) processing such as call setting and outputs the processing result to the UL scheduler 306.

  The SRS processing unit 310 measures the communication quality based on the SRS included in the communication quality of the UL reception data output from the CP removal unit 305. In addition, the SRS processing unit 310 measures the communication quality using, for example, allocation information output from the UL scheduler 306. The SRS processing unit 310 outputs the quality information obtained by the measurement to the UL scheduler 306.

  The DL scheduler 311 performs scheduling for feeding back the quality information and the like output from the UL scheduler 306 to the UE # 0 to UE # 2. The DL scheduler 311 outputs the quality information output from the UL scheduler 306 to the DL processing unit 312 based on the scheduling result. The DL processing unit 312 performs DL processing such as quality information output from the DL scheduler 311 and outputs the DL processing to the IF control unit 304. Thereby, quality information etc. are fed back to UE # 0 to UE # 2.

<Configuration of SRS processing unit>
Next, the configuration of the SRS processing unit 310 will be described. The SRS processing unit 310 includes a reception information processing unit 313, an FFT unit 314, a base sequence removal unit 315, a CH estimation processing unit 316, an fd estimation processing unit 317, a power measurement unit 318, an IFFT unit 319, A power determination processing unit 320, a TA calculation processing unit 321, and a processing result transfer unit 322 are provided.

  The reception information processing unit 313 performs reception information processing on the UL reception data output from the CP removal unit 305 and outputs the received information to the FFT unit 314. The FFT unit 314 performs fast Fourier transform (Fast Fourier Transform) on the UL received data output from the reception information processing unit 313 and outputs the result to the base sequence removal unit 315.

  Base sequence removal section 315 removes the base sequence of the UL received data output from FFT section 314 and outputs the result to CH estimation processing section 316 and IFFT section 319. The CH estimation processing unit 316 and the fd estimation processing unit 317 perform processing along the frequency axis (frequency axis processing). The CH estimation processing unit 316 performs channel estimation of the UL reception data output from the base sequence removal unit 315. The CH estimation processing unit 316 outputs the channel estimation result to the fd estimation processing unit 317 and the power measurement unit 318.

  The fd estimation processing unit 317 performs fd estimation processing based on the channel estimation result output from the CH estimation processing unit 316. Specifically, the fd estimation processing unit 317 performs fd estimation by calculating a time-series correlation of frequencies indicated by the channel estimation result. The fd estimation processing unit 317 outputs the fd estimation value obtained by the fd estimation process to the processing result transfer unit 322.

  The power measuring unit 318 measures received power based on the channel estimation result output from the CH estimation processing unit 316. The power measurement unit 318 outputs the received power value obtained by the measurement to the processing result transfer unit 322.

  IFFT section 319 performs inverse fast Fourier transform (Inverse FFT) on the UL reception data output from base sequence removal section 315 and outputs the result to power determination processing section 320. The power determination processing unit 320 and the TA calculation processing unit 321 perform processing along the time axis (time axis processing). The power determination processing unit 320 performs power determination processing on the UL reception data output from the IFFT unit 319 and outputs the data to the TA calculation processing unit 321.

  The TA calculation processing unit 321 performs TA calculation processing based on the UL reception data output from the power determination processing unit 320. Specifically, the SRS processing unit 310 calculates the temporal position information of the data mapped to the UL reception data output from the power determination processing unit 320, so that the base station 300 and the UE Measure the synchronization timing shift. Then, the SRS processing unit 310 calculates a TA value for correcting the measured deviation. The TA calculation processing unit 321 outputs the TA value obtained by the TA calculation processing to the processing result transfer unit 322.

  The processing result transfer unit 322 includes an UL including the fd estimation value output from the fd estimation processing unit 317, the received power value output from the power measurement unit 318, and the TA value output from the TA calculation processing unit 321. The quality information of the received data is output to the UL scheduler 306. Thereby, the fd estimated value, the TA value, and the like are fed back to UE # 0 to UE # 2. UE # 0 to UE # 2 correct the setting for transmitting UL data to base station 300 based on the received fd estimation value and TA value.

  FIG. 4 is a diagram illustrating an example of a processing order by the SRS processing unit illustrated in FIG. 3. In FIG. 4, the horizontal axis represents time. An SRS processing interval 401 indicates a unit time (subframe) of communication quality measurement processing in the SRS processing unit 310. Reception information processing 410 indicates reception information processing by the reception information processing unit 313.

  Received power processing 420 indicates received power measurement processing by the power measurement unit 318. The fd estimation process 430 shows the fd estimation process by the fd estimation processing unit 317. The power profile processing 440 indicates power determination processing by the power determination processing unit 320. A TA calculation process 450 indicates a TA calculation process performed by the TA calculation processing unit 321. A transfer process 460 indicates a quality information transfer process by the process result transfer unit 322.

  The SRS processing interval 401 is received information processing 410, received power processing 420, fd estimation processing 430, power profile processing 440, TA calculation processing for one or a plurality of UEs every SRS processing interval 401 (one subframe). 450 and transfer processing 460 are performed. UE # 0 to UE # 2 are periodically assigned to any of the consecutive SRS processing intervals 401, and the communication quality is measured at the assigned SRS processing interval 401.

(Fd estimation processing unit)
FIG. 5 is a block diagram illustrating a configuration example of the fd estimation processing unit illustrated in FIG. 3. As shown in FIG. 5, the fd estimation processing unit 317 includes an fd threshold storage unit 501, a flag storage unit 502, and processing units 510A, 510B, 510C,. The fd threshold value storage unit 501 stores an fd threshold value for comparison with the fd estimated value.

  The flag storage unit 502 indicates whether or not to perform load distribution for increasing the measurement interval for UEs whose fd estimated values of the UEs # 0, # 1, # 2,. A flag is stored. For example, when load distribution is performed, the load distribution execution flag is set to “1”, and when load distribution is not performed, the load distribution execution flag is set to “0”.

  Processing units 510A, 510B, 510C,... Are processing units that perform fd estimation processing for UEs # 0, # 1, # 2,. For example, the processing unit 510A that performs the fd estimation process of UE # 0 includes an estimated value storage unit 511, a processing timing storage unit 512, an fd determination unit 513, a processing timing determination unit 514, and an fd estimation unit 515. I have. The estimated value storage unit 511 stores the fd estimated value output from the fd estimating unit 515. The processing timing storage unit 512 stores the processing timing of the fd estimation process output from the fd estimation unit 515.

  The fd determination unit 513 acquires an fd threshold value for comparison with the fd estimated value from the fd threshold value storage unit 501. The fd determination unit 513 compares the acquired fd threshold value with the previous fd estimated value stored in the estimated value storage unit 511. Then, the fd determination unit 513 determines whether the UE # 0 is “high fd” or “low fd” based on the comparison result. For example, “high fd” is a UE whose fd estimate is greater than the fd threshold (communication quality is less than the quality threshold), and “low fd” is a UE whose fd estimate is less than or equal to the fd threshold (communication quality is greater than or equal to the quality threshold). It is.

  When it is determined that the UE # 0 is “high fd”, the fd determination unit 513 outputs the first interval as the measurement interval to the processing timing determination unit 514. In addition, when it is determined that UE # 0 is “low fd”, the fd determination unit 513 outputs the second interval to the processing timing determination unit 514 as the measurement interval. The second interval is a period longer than the first interval. For example, the first interval is an interval of 2 subframes, and the second interval is an interval of 4 subframes.

  The process timing determination unit 514 sets the measurement interval output from the fd determination unit 513 as the measurement interval of the fd estimation process of UE # 0. The processing timing determination unit 514 outputs a trigger signal to the fd estimation unit 515 at the set measurement interval. Specifically, the processing timing determination unit 514 outputs a trigger signal every time the elapsed time from the previous processing timing stored in the processing timing storage unit 512 to the present reaches the set measurement interval.

  When the trigger signal is output from the processing timing determination unit 514, the fd estimation unit 515 performs the fd estimation process for the UE # 0 based on the channel estimation result (see FIG. 3) output from the fd estimation unit 515. When the fd estimation unit 515 performs the fd estimation process, the fd estimation process outputs the processing timing at which the fd estimation process is performed to the processing timing storage unit 512, and the fd estimation value obtained by the fd estimation process is output to the processing result transfer unit 322 and the estimation. The data is output to the value storage unit 511.

  For example, a UE that is on a train or a vehicle and has a high moving speed has a high fd estimated value. Also, a UE with a high moving speed has a large amount of change in the fd estimated value. On the other hand, for example, a UE whose movement speed is low due to a user walking or riding a bicycle has a low fd estimated value. In addition, the UE having a low moving speed has a small amount of change in the fd estimated value.

  Although the configuration of the processing unit 510A has been described here, the same applies to the processing units 510B, 510C,. Thereby, the fd estimation processing unit 317 can perform the fd estimation process for each of the UE # 0 to UE # 2. Further, the comparison by the processing timing storage unit 512 and the setting of the measurement interval by the processing timing determination unit 514 are also performed for each UE.

  FIG. 6 is a flowchart illustrating an example of an operation performed by the fd estimation processing unit illustrated in FIG. The fd estimation processing unit 317 repeatedly performs the following steps for each UE that performs the fd estimation process (for the number of UEs). Hereinafter, the UE to be processed is referred to as a target UE. First, the fd determination unit 513 determines whether or not the load distribution execution flag stored in the flag storage unit 502 is “1” (step S601). When the load distribution execution flag is not “1” (step S601: No), the process proceeds to step S605.

  In step S601, when the load distribution execution flag of the target UE is “1” (step S601: Yes), the fd determination unit 513 determines whether the fd estimation process of the target UE is the second time or later. (Step S602). In step S602, for example, if the fd estimated value of the target UE is stored in the estimated value storage unit 511, it is determined to be the second time or later, and if not stored, it is determined to be the first time. If it is not the second or subsequent fd estimation process (step S602: No), the process proceeds to step S605.

  In step S602, when it is the second or subsequent fd estimation process (step S602: Yes), the fd determination unit 513 acquires the previous fd estimated value of the target UE from the estimated value storage unit 511 (step S603). Next, the fd determination unit 513 determines whether or not the fd estimated value acquired in step S603 is equal to or less than the fd threshold (step S604). When the fd estimation value is larger than the fd threshold (step S604: No), the fd determination unit 513 determines that the target UE is “high fd” (step S605).

  Next, the process timing determination unit 514 sets two subframes for the measurement interval of the target UE (step S606), and proceeds to step S609. When the fd estimated value is equal to or less than the fd threshold (step S604: Yes), the fd determination unit 513 determines that the target UE is “low fd” (step S607). Next, the process timing determination unit 514 sets 4 subframes as the measurement interval of the target UE (step S608).

  Next, the process timing determination unit 514 acquires the previous process timing of the fd estimation process of the target UE from the process timing storage unit 512 (step S609). Next, the processing timing determination unit 514 determines whether or not the elapsed time from the previous processing timing acquired in step S609 is the measurement interval set in step S606 or step S608 (step S610).

  In step S610, when the elapsed time from the previous processing timing is not the measurement interval (step S610: No), the series of operations ends. When the elapsed time from the previous process timing is the measurement interval (step S610: Yes), the fd estimation unit 515 performs the fd estimation process of the target UE (step S611). Next, the fd estimated value obtained by the fd estimating process in step S611 is stored in the estimated value storage unit 511 (step S612). Next, the processing timing by step S611 is memorize | stored in the processing timing memory | storage part 512 (step S613), and a series of operation | movement is complete | finished.

  By repeatedly performing the above steps, the fd estimation value estimated last time and the fd threshold value are compared for each UE, and the measurement interval of the fd estimation process can be set based on the comparison result. Specifically, when the previously estimated fd estimated value is equal to or less than the fd threshold, the period of the fd estimating process can be made longer than when the previously estimated fd estimated value is larger than the fd threshold. Therefore, a UE with a low fd estimate has a relatively long fd estimate measurement interval, and a UE with a high fd estimate has a relatively short fd estimate measurement interval.

  7 to 10 are diagrams (No. 1) to (No. 4) illustrating periodic fd estimation processing by the fd estimation processing unit. 7 to 10, the horizontal axis indicates the number of SRS processes. The vertical axis indicates the amount of fd estimation processing. The SRS processing interval 701 is the SRS processing interval 401 (one subframe) shown in FIG. The periods A to E,... Are each period for each SRS processing interval 701. Each step shown in FIG. 6 is performed, for example, every SRS processing interval 701. The maximum processing amount 702 indicates the upper limit of the processing amount that can be processed by the fd estimation processing unit 317 in the SRS processing interval 701.

  The UEs # 0 to # 9 are UEs for which the fd estimation processing unit 317 performs fd estimation processing. Each of the UEs # 0 to # 9 performs fd estimation processing at a measurement interval of 2 subframes in the initial state. For example, the UE # 0 performs the fd estimation process in the periods A, C, E,. Further, the UE # 4 performs the fd estimation process in the periods B, D,.

  “UE #? Low fd” in the figure indicates the fd estimation process of the UE in which the fd estimated value is determined to be equal to or less than the fd threshold. Also, “UE #? High fd” in the figure indicates the fd estimation process of the UE that has been determined that the fd estimated value is greater than the fd threshold. As illustrated in FIG. 7, the greater the number of UEs that perform the fd estimation process in the SRS process interval 701, the greater the processing amount of the fd estimation process.

  Therefore, the number of UEs whose fd estimation processing amount reaches the maximum processing amount 702 becomes the upper limit of the number of UEs that can perform fd estimation processing in the SRS processing interval 701. For example, in the periods B, D,..., The number of UEs that perform fd estimation processing is 6, and the processing amount of fd estimation processing reaches the maximum processing amount 702. Therefore, no more fd estimation processing of the UE can be performed in the periods B, D,.

  In the state illustrated in FIG. 7, the processing timing determination unit 514 lengthens the measurement interval of the UE determined to be “low fd”. For example, the processing timing determination unit 514 changes the measurement interval of the UE determined as “low fd” from 2 subframes to 4 subframes. Specifically, since the UEs # 2, # 3, # 8, and # 9 are “low fd”, the processing timing determination unit 514 sets the measurement intervals of the UEs # 2, # 3, # 8, and # 9 to 4 Set to subframe.

  As a result, as indicated by reference numeral 801 in FIG. 8, the fd estimation process for UE # 2 is not performed in the period C,. Further, as indicated by reference numeral 802, the UE # 3 fd estimation process is not performed in the periods A, E,. Further, as indicated by reference numeral 803, the fd estimation process of UE # 8 is not performed in the period D,. Further, as indicated by reference numeral 804, the fd estimation process of UE # 9 is not performed in the period B,.

  The hatched portions 901 to 905 in FIG. 9 indicate processing time vacancies caused by setting the measurement intervals of the UEs # 2, # 3, # 8, and # 9 to 4 subframes. As a result, for example, as indicated by reference numerals 1001 and 1002 in FIG. 10, it is possible to assign a new fd estimation process for UE # 10 in periods B and D.

  FIG. 11 is a diagram illustrating a measurement interval of a newly added UE. 11, the same parts as those shown in FIGS. 7 to 10 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 11, a case will be described in which a new UE # 10 is added in a state where the fd estimation process is performed for UEs # 0 to # 9.

  For example, the fd estimation process of UE # 10 is first assigned to period A as indicated by reference numeral 1101. In this case, since the fd estimation process of UE # 10 is the first in period A, UE # 10 is determined to be “high fd”, and two subframes are set in the measurement period. Next, it is assumed that UE # 10 is determined to be “low fd” in period B.

  In this case, 4 subframes are set in the measurement cycle of UE # 10. Therefore, as indicated by reference numeral 1102, the fd estimation process of UE # 10 is not performed in period C two subframes after period A. And as shown to the code | symbol 1103, in the period E 4 sub-frames after the period A, fd estimation process of UE # 10 is performed.

  FIG. 12 is a diagram illustrating processing when the UE fd estimation value changes. In FIG. 12, the same parts as those shown in FIGS. 7 to 10 are denoted by the same reference numerals, and description thereof is omitted. As indicated by reference numeral 1201, it is assumed that UE # 2 is determined to be “low fd” in period A. In this case, the fd estimation process for UE # 2 is performed after period A, as shown by reference numeral 1202, in period E after four subframes of period A.

  Then, it is assumed that the fd estimated value of UE # 2 increases between period A and period E, and UE # 2 is determined to be “high fd” in period E. In this case, two subframes are set in the measurement interval of UE # 2 in period E. Therefore, the UE # 2 fd estimation process is performed after the period E in a period G after two subframes of the period E, as indicated by reference numeral 1203.

  Also assume that UE # 2 is determined to be “high fd” in period G as well. In this case, the UE # 2 fd estimation process is performed after the period G in a period I two subframes after the period E, as indicated by reference numeral 1204. Thus, by repeatedly performing each step shown in FIG. 6, the UE measurement interval can be dynamically set even if the UE fd estimation value changes. For this reason, fd estimation processing of each UE can be performed at an appropriate frequency.

(TA calculation processing part)
FIG. 13 is a block diagram illustrating a configuration example of the TA calculation processing unit illustrated in FIG. 3. As shown in FIG. 13, the TA calculation processing unit 321 includes a TA threshold storage unit 1301, a flag storage unit 1302, and processing units 1310A, 1310B, 1310C,. The TA threshold storage unit 1301 stores a TA threshold for comparison with the TA value.

  The flag storage unit 1302 includes a load distribution execution flag indicating whether or not to perform load distribution for increasing the measurement interval for UEs having a TA value equal to or greater than the TA threshold among UE # 0, # 1, # 2,. It is remembered. For example, when load distribution is performed, the load distribution execution flag is set to “1”, and when load distribution is not performed, the load distribution execution flag is set to “0”.

  Processing units 1310A, 1310B, 1310C,... Are processing units that perform TA calculation processing for UEs # 0, # 1, # 2,. For example, the processing unit 1310A that performs the TA calculation process for UE # 0 includes an estimated value storage unit 1311, a processing timing storage unit 1312, a TA determination unit 1313, a processing timing determination unit 1314, and a TA calculation unit 1315. I have. The estimated value storage unit 1311 stores the TA value output from the TA calculation unit 1315. The processing timing storage unit 1312 stores the processing timing of the TA calculation process output from the TA calculation unit 1315.

  The TA determination unit 1313 acquires a TA threshold for comparison with the TA value from the TA threshold storage unit 1301. The TA determination unit 1313 compares the acquired TA threshold value with the previous TA value stored in the estimated value storage unit 1311. Then, the TA determination unit 1313 determines whether the UE # 0 is “high TA value” or “low TA value” based on the comparison result. For example, “TA value high” is a UE whose TA value is greater than the TA threshold (communication quality is less than the quality threshold), and “TA value small” is a UE whose TA value is the TA threshold or less (communication quality is the quality threshold or more). It is.

  If the TA determination unit 1313 determines that UE # 0 is “TA value high”, the TA determination unit 1313 outputs the first interval to the processing timing determination unit 1314 as the measurement interval. Also, when the TA determination unit 1313 determines that UE # 0 is “TA value small”, the TA determination unit 1313 outputs the second interval to the processing timing determination unit 1314 as the measurement interval. The second interval is a period longer than the first interval. For example, the first interval is an interval of 2 subframes, and the second interval is an interval of 4 subframes.

  The process timing determination unit 1314 sets the measurement interval output from the TA determination unit 1313 as the measurement interval of the TA calculation process. The processing timing determination unit 1314 outputs a trigger signal to the TA calculation unit 1315 at the set measurement interval. Specifically, the processing timing determination unit 1314 outputs a trigger signal every time the elapsed time from the previous processing timing stored in the processing timing storage unit 1312 to the present reaches the set measurement interval.

  When the trigger signal is output from the processing timing determination unit 1314, the TA calculation unit 1315 performs a TA calculation process for UE # 0 based on the UL reception data (see FIG. 3) from the power determination processing unit 320. When the TA calculating unit 1315 performs the TA calculating process, the TA calculating unit 1315 outputs the processing timing at which the TA calculating process is performed to the processing timing storage unit 1312, and the TA value obtained by the TA calculating process is output to the processing result transfer unit 322 and the estimated value. The data is output to the storage unit 1311.

  A UE having a large amount of change in the distance to the base station 300 has a high TA value and a large amount of change in the TA value. On the other hand, a UE having a small amount of change in the distance to the base station 300 has a low TA value and a small amount of change in the TA value.

  Although the configuration of the processing unit 1310A has been described here, the same applies to the processing units 1310B, 1310C,. Thereby, the TA calculation process part 321 can perform TA calculation process for every UE. Further, the comparison by the processing timing storage unit 1312 and the setting of the measurement interval by the processing timing determination unit 1314 are also performed for each UE.

  FIG. 14 is a flowchart illustrating an example of operations performed by the TA calculation processing unit illustrated in FIG. The TA calculation processing unit 321 repeatedly performs the following steps for each UE that performs TA calculation processing (for the number of UEs). Hereinafter, the UE to be processed is referred to as a target UE. First, the TA determination unit 1313 determines whether or not the load distribution execution flag of the target UE stored in the flag storage unit 1302 is “1” (step S1401). When the load distribution execution flag is not “1” (step S1401: No), the process proceeds to step S1405.

  In step S1401, when the load distribution execution flag of the target UE is “1” (step S1401: Yes), the TA determination unit 1313 determines whether the TA calculation process of the target UE is the second time or later. (Step S1402). In step S1402, for example, if the TA value of the target UE is stored in the estimated value storage unit 1311, it is determined to be the second time or later, and if not stored, it is determined to be the first time. If it is not the second or subsequent TA calculation process (step S1402: No), the process proceeds to step S1405.

  In step S1402, in the case of the second or subsequent TA calculation process (step S1402: Yes), the TA determination unit 1313 acquires the previous TA value of the target UE from the estimated value storage unit 1311 (step S1403). Next, the TA determination unit 1313 determines whether or not the TA value acquired in step S1403 is equal to or less than the TA threshold (step S1404). When the TA value is larger than the TA threshold (step S1404: No), the TA determination unit 1313 determines that the target UE is “TA value large” (step S1405).

  Next, the processing timing determination unit 1314 sets two subframes for the measurement interval of the target UE (step S1406), and proceeds to step S1409. When the TA value is equal to or smaller than the TA threshold (step S1404: Yes), the TA determination unit 1313 determines that the target UE is “TA value small” (step S1407). Next, the process timing determination unit 1314 sets 4 subframes as the measurement interval of the target UE (step S1408).

  Next, the processing timing determination unit 1314 acquires the previous processing timing of the TA calculation processing of the target UE from the processing timing storage unit 1312 (step S1409). Next, the processing timing determination unit 1314 determines whether or not the elapsed time from the previous processing timing acquired in step S1409 is the measurement interval set in step S1406 or step S1408 (step S1410).

  In step S1410, when the elapsed time from the previous processing timing is not the measurement interval (step S1410: No), the series of operations ends. When the elapsed time from the previous processing timing is the measurement interval (step S1410: Yes), the TA calculation unit 1315 performs the TA calculation process for the target UE (step S1411). Next, the TA value obtained by the TA calculation process in step S1411 is stored in the estimated value storage unit 1311 (step S1412). Next, the processing timing in step S1411 is stored in the processing timing storage unit 1312 (step S1413), and the series of operations is terminated.

  By repeating the above steps, the TA value calculated last time and the TA threshold value are compared for each UE, and the measurement interval of the TA calculation process can be set based on the comparison result. Specifically, when the previously calculated TA value is equal to or less than the TA threshold, the TA calculation processing cycle can be made longer than when the previously calculated TA value is greater than the TA threshold. Therefore, a UE with a low TA value has a relatively long TA value measurement interval, and a UE with a high TA value has a relatively short TA value measurement interval.

  15 to 18 are diagrams (No. 1) to (No. 4) illustrating periodic TA calculation processing by the TA calculation processing unit. 15 to 18, the horizontal axis indicates the number of SRS processes. The vertical axis represents the amount of TA calculation processing. The SRS processing interval 1501 is the SRS processing interval 401 (one subframe) shown in FIG.

  An averaging time 1503 is an averaging time in the TA calculation. The TA calculation unit 1315 calculates, for example, an average value of timing deviations during the averaging time 1503 as a TA value. Here, the averaging time 1503 is 4 subframes long. The periods A to E,... Are each period for each SRS processing interval 1501. Each step shown in FIG. 14 is performed, for example, every SRS processing interval 1501. The maximum processing amount 1502 indicates the upper limit of the processing amount that can be processed by the TA calculation processing unit 321 in the SRS processing interval 1501.

  The UEs # 0 to # 9 are UEs for which the TA calculation processing unit 321 performs TA calculation processing. Each of the UEs # 0 to # 9 performs the TA calculation process at a measurement interval of 2 subframes in the initial state. For example, the UE # 0 performs TA calculation processing in the periods A, C, E,. In addition, UE # 4 performs TA calculation processing in cycles B, D,.

  “UE #? TA value small” in the figure indicates the TA calculation process of the UE whose TA value is determined to be equal to or less than the TA threshold. Also, “UE #? TA value high” in the figure indicates the TA calculation processing of the UE that has been determined that the TA value is greater than the TA threshold. As illustrated in FIG. 15, the greater the number of UEs that perform the TA calculation process in the SRS process interval 1501, the greater the amount of TA calculation process.

  Therefore, the number of UEs whose TA calculation processing amount reaches the maximum processing amount 1502 is the upper limit of the number of UEs that can perform TA calculation processing in the SRS processing interval 1501. For example, in the periods B, D,..., The number of UEs that perform the TA calculation process is 6, and the processing amount of the TA calculation process reaches the maximum processing amount 1502. Therefore, in the periods B, D,..., No further TA calculation processing of the UE can be performed.

  In the state illustrated in FIG. 15, the processing timing determination unit 1314 increases the measurement interval of the UE determined to be “TA value small”. For example, the processing timing determination unit 1314 changes the measurement interval of the UE determined as “TA value small” from 2 subframes to 4 subframes. Specifically, since the UEs # 2, # 3, # 8, and # 9 are “TA value small”, the processing timing determination unit 1314 sets the measurement intervals of the UEs # 2, # 3, # 8, and # 9. Set to 4 subframes.

  As a result, as shown by reference numeral 1601 in FIG. 16, the TA calculation process of UE # 2 is not performed in the period C,. Further, as indicated by reference numeral 1602, the TA calculation process of UE # 3 is not performed in the periods A, E,. Further, as indicated by reference numeral 1603, the TA calculation process of UE # 8 is not performed in the period D,. Further, as indicated by reference numeral 1604, the TA calculation process of UE # 9 is not performed in the period B,.

  17 indicate empty processing time caused by setting the measurement intervals of UEs # 2, # 3, # 8, and # 9 to 4 subframes. As a result, for example, as indicated by reference numerals 1801 and 1802 in FIG. 18, it is possible to perform TA calculation processing for a new UE # 10 in periods B and D.

  FIG. 19 is a diagram illustrating a measurement interval of a newly added UE. 19, parts that are the same as the parts shown in FIGS. 15 to 18 are given the same reference numerals, and descriptions thereof will be omitted. As illustrated in FIG. 19, a case will be described in which a new UE # 10 is added in a state where the TA calculation processing of the UEs # 0 to # 9 is performed.

  For example, the TA calculation process of UE # 10 is first assigned to period A as indicated by reference numeral 1901. In this case, since the TA calculation process of UE # 10 is the first time in period A, UE # 10 is determined to be “large TA value”, and two subframes are set in the measurement period. Next, in cycle B, it is assumed that UE # 10 is determined to be “TA value small”.

  In this case, 4 subframes are set in the measurement cycle of UE # 10. Therefore, as indicated by reference numeral 1902, the TA estimation process for UE # 10 is not performed in period C two subframes after period A. Then, as indicated by reference numeral 1903, the TA estimation process for UE # 10 is performed in period E four subframes after period A.

  FIG. 20 is a diagram illustrating processing when the TA value of the UE changes. 20, parts that are the same as the parts shown in FIGS. 15 to 18 are given the same reference numerals, and descriptions thereof will be omitted. As indicated by reference numeral 2001, it is assumed that UE # 2 is determined to be “TA value small” in period A. In this case, the TA calculation process for UE # 2 is performed after period A, as indicated by reference numeral 2002, in period E after four subframes of period A.

  Then, assume that the TA value of UE # 2 increases between period A and period E, and UE # 2 is determined to be “TA value large” in period E. In this case, two subframes are set in the measurement interval of UE # 2 in period E. Accordingly, the TA calculation process for UE # 2 is performed after period E, as indicated by reference numeral 2003, in period G two subframes after period E.

  Further, it is assumed that UE # 2 is determined to be “large TA value” also in period G. In this case, the TA calculation process for UE # 2 is performed after period G, as indicated by reference numeral 2004, in period I after two subframes of period G. Thus, by repeatedly performing each step shown in FIG. 14, even if the TA value of the UE changes, the UE measurement interval can be set dynamically. For this reason, TA calculation processing of each UE can be performed at an appropriate frequency.

  As described above, according to the base station 300 according to the third embodiment, the measurement process is temporally dispersed by increasing the measurement interval for the UE having a relatively low fd estimated value (high communication quality), and the measurement is performed. The frequency of processing can be reduced. Thereby, the time margin of the measurement process can be expanded, and the fd estimation process (communication quality measurement) can be performed efficiently.

  Further, a UE having a low fd estimated value is considered to have a low moving speed because, for example, the user is walking or riding a bicycle. For this reason, UE with a low fd estimated value is less likely to change the fd estimated value abruptly than a UE with a high fd estimated value. For this reason, it is possible to suppress deterioration in communication performance due to lowering the frequency of the measurement process by lowering the frequency of the measurement process of the UE having a low fd estimated value.

  For UEs with relatively low TA values (high communication quality), the measurement process can be dispersed in time by increasing the measurement interval, and the frequency of the measurement process can be reduced. Thereby, the time margin of the measurement process can be expanded, and the TA calculation process (communication quality measurement) can be performed efficiently. In addition, a UE with a low TA value is considered to have a small change in distance from the base station 300, for example. For this reason, UE with a low TA value is less likely to change the TA value abruptly than a UE with a high TA value. For this reason, it is possible to suppress deterioration in communication performance caused by reducing the frequency of the measurement process by reducing the frequency of the measurement process of the UE having a low TA value.

(Embodiment 3)
(Fd estimation processing unit)
FIG. 21 is a block diagram of the configuration of the fd estimation processing unit according to the third embodiment. In FIG. 21, the same components as those shown in FIG. As illustrated in FIG. 21, the fd estimation processing unit 317 according to the third embodiment includes a table storage unit 2111, a threshold setting unit 2112, and a distributed execution determination unit 2113 in addition to the configuration illustrated in FIG. I have. In FIG. 21, the fd determination unit 513 in the configuration of the processing unit 510A is illustrated.

  The fd estimation processing unit 317 acquires information on the number of UEs (number of mobile terminals) performing the SRS process in each cycle of the SRS process. For example, the fd estimation processing unit 317 acquires the number of UEs based on the allocation information output from the UL scheduler 306. The table storage unit 2111 stores a table that associates the number of UEs with the fd threshold. The threshold setting unit 2112 sets the fd threshold based on the acquired number of UEs. For example, the threshold setting unit 2112 sets a higher fd threshold when the number of UEs is relatively large than when the number of UEs is relatively small.

  Specifically, the threshold setting unit 2112 acquires the fd threshold corresponding to the number of UEs in the table stored in the threshold setting unit 2112. The threshold value setting unit 2112 outputs the acquired fd threshold value to the fd threshold value storage unit 501. The fd threshold value storage unit 501 stores the fd threshold value output from the threshold value setting unit 2112.

  Accordingly, the fd determination unit 513 (see FIG. 5) can use the fd threshold set by the threshold setting unit 2112 for comparison. For this reason, when the number of UEs is large and the amount of processing of the SRS processing increases, the fd threshold value is increased to facilitate the distribution of the fd estimation processing, thereby improving the processing efficiency. On the other hand, when the number of UEs is small, the fd threshold value is lowered so that the fd estimation process is frequently performed, and the communication performance can be improved.

  The distribution execution determination unit 2113 determines whether to perform load distribution of the fd estimation process based on the acquired number of UEs. The distributed execution determination unit 2113 outputs the determination result to the flag storage unit 502 as a load distribution execution flag. The flag storage unit 502 stores the load distribution execution flag output from the distributed execution determination unit 2113.

  For example, the distribution execution determination unit 2113 determines that load distribution is performed when the number of UEs is greater than a predetermined threshold, and determines that load distribution is not performed when the number of UEs is equal to or less than the predetermined threshold. Thereby, the process timing determination part 514 can set a measurement interval to a 1st interval, when the number of UE is below a predetermined threshold value. Thereby, when the number of UEs is small, the fd estimation process is frequently performed, and the communication performance can be improved.

  FIG. 22 is a flowchart illustrating an example of the operation of the fd estimation processing unit illustrated in FIG. The fd estimation processing unit 317 executes, for example, each step illustrated in FIG. 22 as an operation common to the UE # 0 to UE # 2,. First, the number of UEs is acquired (step S2201). Next, the distributed execution determination unit 2113 determines whether or not the number of UEs acquired in step S2201 is greater than or equal to a predetermined threshold (step S2202).

  In step S2202, when the number of UEs is not equal to or greater than the predetermined threshold (step S2202: No), the distributed execution determination unit 2113 sets the load distribution execution flag in the flag storage unit 502 to “0” (step S2203), End the operation. When the number of UEs is equal to or greater than the predetermined threshold (step S2202: Yes), the threshold setting unit 2112 sets the fd threshold based on the number of UEs (step S2204).

  Next, the distributed execution determination unit 2113 sets the load distribution execution flag in the flag storage unit 502 to “1” (step S2205), and ends the series of operations. By repeatedly performing the above steps, the load distribution execution flag can be set according to the number of UEs, and the fd threshold can be set according to the number of UEs.

(TA calculation processing part)
FIG. 23 is a block diagram of the configuration of the TA calculation processing unit according to the third embodiment. In FIG. 23, the same components as those shown in FIG. As illustrated in FIG. 23, the TA calculation processing unit 321 according to the third embodiment includes a table storage unit 2311, a threshold setting unit 2312, and a distributed execution determination unit 2313 in addition to the configuration illustrated in FIG. I have. Note that in FIG. 23, the TA determination unit 1313 in the configuration of the processing unit 1310A is illustrated.

  The TA calculation processing unit 321 acquires the number of UEs that perform the SRS process in each cycle of the SRS process. For example, the TA calculation processing unit 321 acquires the number of UEs that perform SRS processing based on the allocation information output from the UL scheduler 306. The table storage unit 2311 stores a table that associates the number of UEs with the TA threshold. The threshold setting unit 2312 sets the TA threshold based on the acquired number of UEs. For example, when the number of UEs is relatively large, the threshold setting unit 2312 sets a higher TA threshold than when the number of UEs is relatively small.

  Specifically, the threshold setting unit 2312 acquires the TA threshold corresponding to the number of UEs in the table stored in the threshold setting unit 2312. The threshold setting unit 2312 outputs the acquired TA threshold to the TA threshold storage unit 1301. The TA threshold storage unit 1301 stores the TA threshold output from the threshold setting unit 2312.

  Accordingly, the TA determination unit 1313 (see FIG. 13) can use the TA threshold set by the threshold setting unit 2312 for comparison. For this reason, when the number of UEs is large and the amount of processing of the SRS processing increases, the TA threshold value is increased to facilitate the distribution of the TA calculation processing, and the processing efficiency can be improved. On the other hand, when the number of UEs is small, the TA threshold value is lowered so that the TA calculation process is frequently performed, and the communication performance can be improved.

  The distribution execution determination unit 2313 determines whether or not to perform load distribution in the TA calculation process based on the acquired number of UEs. The distributed execution determination unit 2313 outputs the determination result to the flag storage unit 1302 as a load distribution execution flag. The flag storage unit 1302 stores the load distribution execution flag output from the distributed execution determination unit 2313.

  For example, the distribution execution determination unit 2313 determines that load distribution is performed when the number of UEs is greater than a predetermined threshold, and determines that load distribution is not performed when the number of UEs is equal to or less than the predetermined threshold. Thereby, the process timing determination part 514 can set a measurement interval to a 1st interval, when the number of UE is below a predetermined threshold value. As a result, when the number of UEs is small, TA calculation processing is frequently performed, and communication performance can be improved.

  FIG. 24 is a flowchart illustrating an example of the operation of the TA calculation processing unit illustrated in FIG. The TA calculation processing unit 321 executes, for example, each step shown in FIG. 24 as an operation common to UE # 0 to UE # 2,. First, the number of UEs is acquired (step S2401). Next, the distributed execution determining unit 2313 determines whether or not the number of UEs acquired in step S2401 is greater than or equal to a predetermined threshold (step S2402).

  In step S2402, if the number of UEs is not equal to or greater than the predetermined threshold (step S2402: No), the distributed execution determination unit 2313 sets the load distribution execution flag in the flag storage unit 1302 to “0” (step S2403), End the operation. When the number of UEs is equal to or greater than the predetermined threshold (step S2402: Yes), the threshold setting unit 2312 sets the TA threshold based on the number of UEs (step S2404).

  Next, the distributed execution determination unit 2313 sets the load distribution execution flag in the flag storage unit 1302 to “1” (step S2405), and the series of operations ends. By repeatedly performing the above steps, it is possible to set the load distribution execution flag according to the number of UEs and set the TA threshold according to the number of UEs.

  FIG. 25 is a diagram illustrating an example of a table stored in the table storage unit illustrated in FIGS. 21 and 23. A table 2510 illustrated in FIG. 25 is a table stored in the table storage unit 2111 of the fd estimation processing unit 317. The table 2510 associates the number of UEs with the fd threshold. In the table 2510, the fd threshold values “0”, “0”, “0”, “P4”, “P4”, “P3”, and “P3” are associated with the UE numbers “0” to “6”, respectively (0 < P4 <P3).

  In this way, by associating a relatively high fd threshold value with a relatively large number of UEs, the threshold setting unit 2112 has a higher fd value when the UE number is relatively large than when the UE number is relatively small. The threshold can be set high (ie, the quality threshold is low). Here, the predetermined threshold value compared in step S2202 of FIG. 22 is “3”. Therefore, when the number of UEs is less than “3”, the load distribution of the fd estimation process is not performed, and therefore, the fd threshold “0” is associated with the number of UEs “0” to “2”.

  The table 2520 is a table stored in the table storage unit 2311 of the TA calculation processing unit 321. The table 2520 associates the number of UEs with the TA threshold. In the table 2520, the TA thresholds “0” “0” “0” “P4” “P4” “P3” “P3” are associated with the UE numbers “0” to “6”, respectively. Here, the predetermined threshold value compared in step S2402 of FIG. 24 is “3”. Therefore, when the number of UEs is less than “3”, the load distribution of the TA calculation process is not performed, so the TA threshold “0” is associated with the number of UEs “0” to “2”.

  In this manner, by associating a relatively high TA threshold with a relatively large number of UEs, the threshold setting unit 2312 may have a relatively large number of UEs than a relatively small number of UEs. The TA threshold can be set high (ie, the quality threshold is low).

  FIGS. 26-1 to 26-3 are diagrams (No. 1) to (No. 3) illustrating changes in threshold values based on the number of UEs. In FIGS. 26A to 26C, the same parts as those shown in FIG. In the period A, since the number of UEs is 2 and less than the predetermined threshold “3”, the load distribution execution flag is set to “0”, and the load distribution of the fd estimation process and the TA calculation process is not performed. UE # 1 has both the fd estimated value and the TA value of P3, and is determined to be “high fd” and “TA value large”. For this reason, UE # 1 is not the target of load distribution.

  Next, it is assumed that the SRS processing of UE # 6 and # 7 is assigned in period C as indicated by reference numeral 2601. It is assumed that both the fd estimated value and the TA value of UE # 6 are P4. Further, it is assumed that the fd estimated value and the TA value of UE # 7 are both P5. In this case, since the number of UEs is 4, the load distribution execution flag is set to “1”, and both the fd threshold and the TA threshold are set to P4 (see FIG. 25).

  Therefore, the UEs # 6 and # 7 are determined to be “low fd” and “low TA value”, respectively, and are subject to load distribution. Specifically, UE # 6 is assigned to period E,... As indicated by reference numeral 2602, and UE # 7 is assigned to periods G,.

  Next, it is assumed that the SRS process of the UEs # 8 and # 9 is assigned in the cycle H as indicated by reference numeral 2604. It is assumed that both the fd estimated value and the TA value of UE # 8 are P0. Further, it is assumed that both the fd estimated value and the TA value of UE # 9 are P1. In this case, since the number of UEs is 6, both the fd threshold and the TA threshold are set to P3 (see FIG. 25).

  Therefore, UE # 1 that has been determined to be “high fd” and “TA value large” is determined to be “low fd” and “TA value small”, and is subject to load distribution. Specifically, as indicated by reference numeral 2605, UE # 1 is assigned to the period L,.

  Next, in the period O, it is assumed that the allocation of the SRS process of the UEs # 6 to # 9 is canceled as indicated by reference numeral 2606. In this case, since the number of UEs is 2 and less than the predetermined threshold “3”, the load distribution execution flag is set to “0”, and load distribution is not performed. Therefore, for example, UE # 1 that has been determined to be “low fd” and “small TA value” is determined to be “high fd” and “large TA value” and is excluded from load balancing. Specifically, as indicated by reference numerals 2607, 2608, and 2609, UE # 1 is assigned to periods Q, S, U,.

  As described above, according to the base station 300 according to the third embodiment, by setting the quality threshold (fd threshold or TA threshold) based on the number of UEs, the communication quality is efficiently measured according to the number of UEs. be able to. Specifically, when the number of UEs is relatively large, the quality threshold is set lower (the fd threshold and the TA threshold are set higher) than when the number of UEs is relatively small.

  Thereby, when the base station 300 is installed in an urban area or the like and the number of UEs is large and the processing amount of the SRS processing increases, the measurement processing can be easily distributed and the processing efficiency can be improved. In addition, when the base station 300 is installed on an expressway or the like and the number of UEs is small but frequent measurement processing is necessary, the measurement processing is frequently performed to improve communication performance. In addition, when the number of UEs is equal to or less than a predetermined threshold, the measurement interval is set to the first interval. When the number of UEs is small, the measurement process is frequently performed, and communication performance can be improved.

(Embodiment 4)
(Fd estimation processing unit)
FIG. 27 is a block diagram of a configuration of the fd estimation processing unit according to the fourth embodiment. In FIG. 27, the same components as those shown in FIG. As illustrated in FIG. 27, the fd estimation processing unit 317 according to the fourth embodiment includes a table storage unit 2711, a threshold / interval setting unit 2712, and a threshold / interval storage unit 2713 in addition to the configuration illustrated in FIG. Yes.

  In this case, the table storage unit 2111, the threshold setting unit 2112, and the distributed execution determination unit 2113 illustrated in FIG. 21 may be omitted. In FIG. 27, the fd determination unit 513 and the processing timing determination unit 514 in the configuration of the processing unit 510A are illustrated. The table storage unit 2711 stores a table that associates the number of UEs, the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval.

  The threshold / interval setting unit 2712 sets the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval based on the acquired number of UEs. Specifically, the threshold / interval setting unit 2712 displays the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval corresponding to the number of UEs in the table stored in the threshold / interval setting unit 2712. get. The threshold / interval setting unit 2712 outputs the acquired fd threshold to the threshold / interval storage unit 2713. The threshold / interval storage unit 2713 stores the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval output from the threshold / interval setting unit 2712.

  The fd determination unit 513 acquires the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval stored in the threshold / interval storage unit 2713. Then, the fd determination unit 513 determines “high fd” when the previous fd estimated value is larger than the first fd threshold value, and outputs two subframes to the processing timing determination unit 514 as the measurement interval. Further, when the previous fd estimated value is between the first fd threshold value and the second fd threshold value, the fd determination unit 513 determines “medium fd”, and the processing timing determination unit 514 determines 4 subframes as the measurement interval. Output to. Further, the fd determination unit 513 determines “low fd” when the previous fd estimated value is equal to or less than the second fd threshold, and outputs 6 subframes as the measurement interval to the processing timing determination unit 514.

  FIG. 28 is a flowchart illustrating an example of a threshold setting operation of the fd estimation processing unit illustrated in FIG. The fd estimation processing unit 317 executes, for example, each step illustrated in FIG. 28 as an operation common to the UE # 0 to UE # 2,. First, the number of UEs is acquired (step S2801). Next, the distributed execution determining unit 2113 determines whether or not the number of UEs acquired in step S2801 is equal to or greater than a predetermined threshold (step S2802).

  If the number of UEs is not greater than or equal to the predetermined threshold in step S2802 (step S2802: No), the distributed execution determination unit 2113 sets the load distribution execution flag in the flag storage unit 502 to “0” (step S2803), and a series of operations Exit. When the number of UEs is equal to or greater than the predetermined threshold (step S2802: Yes), the threshold / interval setting unit 2712 sets a plurality of fd thresholds and measurement intervals based on the number of UEs (step S2804). The plurality of fd thresholds and measurement intervals are a first fd threshold, a first measurement interval, a second fd threshold, and a second measurement interval.

  Next, the distributed execution determination unit 2113 sets the load distribution execution flag in the flag storage unit 502 to “1” (step S2805), and the series of operations ends. By repeatedly performing the above steps, the load distribution execution flag can be set according to the number of UEs, and the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval can be set.

(TA calculation processing part)
FIG. 29 is a block diagram of a configuration of a TA calculation processing unit according to the fourth embodiment. 29, the same components as those illustrated in FIG. 23 are denoted by the same reference numerals, and description thereof is omitted. As illustrated in FIG. 29, the TA calculation processing unit 321 according to the fourth embodiment includes a table storage unit 2911, a threshold / interval setting unit 2912, and a threshold / interval storage unit 2913 in addition to the configuration illustrated in FIG. Yes.

  In this case, the table storage unit 2311, the threshold setting unit 2312, and the distributed execution determination unit 2313 illustrated in FIG. 23 may be omitted. In FIG. 29, the TA determination unit 1313 and the processing timing determination unit 1314 in the configuration of the processing unit 1310A are illustrated. The table storage unit 2911 stores a table that associates the number of UEs, the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval.

  The threshold / interval setting unit 2912 sets the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval based on the acquired number of UEs. Specifically, the threshold / interval setting unit 2912 displays the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval corresponding to the number of UEs in the table stored in the threshold / interval setting unit 2912. get. The threshold / interval setting unit 2912 outputs the acquired TA threshold to the threshold / interval storage unit 2913. The threshold / interval storage unit 2913 stores the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval output from the threshold / interval setting unit 2912.

  The TA determination unit 1313 acquires the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval stored in the threshold / interval storage unit 2913. Then, the TA determination unit 1313 determines “TA value is large” when the previous TA value is larger than the first TA threshold, and outputs two subframes to the processing timing determination unit 1314 as the measurement interval. Further, when the previous TA value is between the first TA threshold value and the second TA threshold value, the TA determination unit 1313 determines “in the TA value” and sets 4 subframes as the measurement interval as the processing timing determination unit 1314. Output to. Further, when the previous TA value is equal to or smaller than the second TA threshold, the TA determination unit 1313 determines “TA value is small”, and outputs 6 subframes as a measurement interval to the processing timing determination unit 1314.

  FIG. 30 is a flowchart illustrating an example of a threshold setting operation of the TA calculation processing unit illustrated in FIG. The TA calculation processing unit 321 executes, for example, each step shown in FIG. 30 as an operation common to UE # 0 to UE # 2,. First, the number of UEs is acquired (step S3001). Next, the distributed execution determining unit 2313 determines whether or not the number of UEs acquired in step S3001 is greater than or equal to a predetermined threshold (step S3002).

  If the number of UEs is not equal to or greater than the predetermined threshold in step S3002 (step S3002: No), the distributed execution determination unit 2313 sets the load distribution execution flag in the flag storage unit 1302 to “0” (step S3003), and the series of operations is performed. finish. When the number of UEs is equal to or greater than the predetermined threshold (step S3002: Yes), the threshold / interval setting unit 2912 sets a plurality of TA thresholds and measurement intervals based on the number of UEs (step S3004). The plurality of TA thresholds and measurement intervals are a first TA threshold, a first measurement interval, a second TA threshold, and a second measurement interval.

  Next, the distributed execution determination unit 2313 sets the load distribution execution flag in the flag storage unit 1302 to “1” (step S3005), and the series of operations ends. By repeatedly performing the above steps, the load distribution execution flag can be set according to the number of UEs, and the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval can be set.

  FIG. 31 is a diagram illustrating an example of a table stored in the table storage unit illustrated in FIGS. 27 and 29. A table 3110 illustrated in FIG. 31 is a table stored in the table storage unit 2711 of the fd estimation processing unit 317. The table 3110 associates the number of UEs with the first fd threshold, the first measurement interval, the second fd threshold, and the second measurement interval. Here, the first measurement interval and the second measurement interval are indicated by the number of subframes.

  In the table 3110, the first fd threshold values “0”, “0”, “0”, “P3”, “P3”, “P2”, and “P2” are associated with the UE numbers “0” to “6”, respectively ( 0 <P4 <P3). In the table 3110, the first measurement intervals “2”, “2”, “2”, “4”, “4”, “4”, and “4” are associated with the UE numbers “0” to “6”, respectively. Yes. Further, in the table 3110, the second fd threshold values “0”, “0”, “0”, “P5”, “P5”, “P4”, “P4”, and the second measurement interval for the UE numbers “0” to “6”, respectively. “2” “2” “2” “4” “4” “4” “4” are associated with each other.

Thus, by associating a measurement interval longer than the first measurement interval corresponding to the first fd threshold with the second fd threshold lower than the first fd threshold, the lower the fd estimated value (the higher the communication quality), The measurement interval can be set longer. Here, the predetermined threshold value compared in step S2802 of FIG. 28 is “3”. Therefore, when the number of UEs is less than “3”, the load distribution of the fd estimation process is not performed. Therefore, the first fd threshold, the first measurement interval, the second fd threshold, and the number of UEs “0” to “2” The second measurement interval “0” is associated.

  The table 3120 associates the number of UEs with the first TA threshold, the first measurement interval, the second TA threshold, and the second measurement interval. In the table 3120, the first TA threshold values “0”, “0”, “0”, “P3”, “P3”, “P2”, “P2”, and the first measurement interval “2” for the UE numbers “0” to “6”, respectively. "2" "2" "4" "4" "4" "4" are associated with each other. Further, in the table 3120, the second TA threshold values “0”, “0”, “0”, “P5”, “P5”, “P4”, “P4”, and the second measurement interval are respectively set for the UE numbers “0” to “6”. “2” “2” “2” “4” “4” “4” “4” are associated with each other.

Thus, by associating a measurement interval longer than the first measurement interval corresponding to the first TA threshold with the second TA threshold lower than the first TA threshold, the lower the TA calculated value (the higher the communication quality), The measurement interval can be set longer. Here, the predetermined threshold value compared in step S3002 of FIG. 30 is “3”. Therefore, when the number of UEs is less than “3”, the load distribution of the TA estimation process is not performed. Therefore, the number of UEs “0” to “2” includes the first TA threshold, the first measurement interval, the second TA threshold, and The second measurement interval “0” is associated.

  FIG. 32 is a flowchart illustrating an example of the operation of the fd estimation processing unit illustrated in FIG. Steps S3201 to S3203 shown in FIG. 32 are the same as steps S601 to S603 shown in FIG. Following step S3203, the fd determination unit 513 determines whether or not the fd estimated value acquired in step S3203 is equal to or less than the first fd threshold (step S3204).

  In step S3204, when the fd estimated value is larger than the first fd threshold (step S3204: No), the fd determination unit 513 determines that the target UE is “high fd” (step S3205). Next, the process timing determination unit 514 sets two subframes for the measurement interval of the target UE (step S3206), and proceeds to step S3212.

  In step S3204, when the fd estimated value is equal to or smaller than the first fd threshold (step S3204: Yes), the fd determination unit 513 determines whether the fd estimated value acquired in step S3203 is equal to or smaller than the second fd threshold. (Step S3207). When the fd estimated value is larger than the second fd threshold (step S3207: No), the fd determination unit 513 determines that the target UE is “medium fd” (step S3208). Next, the process timing determination unit 514 sets four subframes as the measurement interval of the target UE (step S3209), and proceeds to step S3212.

  In step S3207, when the fd estimated value is equal to or smaller than the second fd threshold (step S3207: Yes), the fd determination unit 513 determines that the target UE is “low fd” (step S3210). Next, the process timing determination unit 514 sets 6 subframes as the measurement interval of the target UE (step S3211). Steps S3212 to S3216 shown in FIG. 32 are the same as steps S609 to S613 shown in FIG.

  FIG. 33 is a flowchart showing an example of the operation of the TA calculation processing unit shown in FIG. Steps S3301 to S3303 shown in FIG. 33 are the same as steps S1401 to S1403 shown in FIG. Following step S3303, the TA determination unit 1313 determines whether the TA value acquired in step S3303 is equal to or less than a first TA threshold (step S3304).

  In step S3304, when the TA value is larger than the first TA threshold (step S3304: No), the TA determination unit 1313 determines that the target UE is “TA value large” (step S3305). Next, the process timing determination unit 514 sets two subframes for the measurement interval of the target UE (step S3306), and proceeds to step S3312.

  In step S3304, when the TA value is equal to or smaller than the first TA threshold (step S3304: Yes), the TA determination unit 1313 determines whether the TA value acquired in step S3303 is equal to or smaller than the second TA threshold (step S3304). S3307). When the TA value is larger than the second TA threshold (step S3307: No), the TA determination unit 1313 determines that the target UE is “in the TA value” (step S3308). Next, the process timing determination unit 514 sets 4 subframes as the measurement interval of the target UE (step S3309), and proceeds to step S3312.

  In step S3307, when the TA value is equal to or smaller than the second TA threshold (step S3307: Yes), the TA determination unit 1313 determines that the target UE is “TA value small” (step S3310). Next, the processing timing determination unit 514 sets 6 subframes as the measurement interval of the target UE (step S3311). Steps S3312 to S3316 illustrated in FIG. 33 are the same as steps S1409 to S1413 illustrated in FIG.

  FIG. 34 is a diagram illustrating a change in measurement interval using a plurality of threshold values. 34, the same parts as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof is omitted. In FIG. 34, it is assumed that the fd estimated value and the TA value of each UE are always equal. In the example shown in FIG. 31, since the fd threshold value and the TA threshold value are equal, the fd estimated value and the fd estimated value of the TA values will be described here. In the periods A to O, since the number of UEs is 3 or 4, the first fd threshold is P3, and the second fd threshold is P5.

  The estimated fd values of UE # 2, # 3, # 4, # 5, # 8, and # 9 are P1, P1, P2, P2, P0, and P1, which are larger than the first fd threshold “P3”, respectively. The interval is set to 2 subframes (no load distribution). Here, the fd estimation processing of UE # 2, # 3, # 4, and # 5 is assigned to periods B, D,. Also, the fd estimation processing of UE # 8, # 9 is assigned to periods A, C,.

  Since the estimated fd values of the UEs # 0 and # 1 are P3 and P4 which are equal to or smaller than the first fd threshold “P3” and larger than the second fd threshold “P5”, respectively, the measurement interval is set to 4 subframes (load) With dispersion). Here, the fd estimation process of UE # 0 is assigned to periods A, E,. Further, the fd estimation process of UE # 1 is assigned to the cycles C, G,.

  Since the estimated fd values of the UEs # 6 and # 7 are P5 and P6 below the second fd threshold “P5”, the measurement interval is set to 6 subframes. Here, the SAS processing of UE # 6 is assigned to periods A, G,. Also, the SAS processing of UE # 7 is assigned to cycles C, I,. In this way, by comparing the communication quality such as the fd estimated value and the TA value with a plurality of threshold values and measuring the measurement interval based on the comparison result, the frequency of the measurement process can be flexibly changed. Thereby, communication quality can be measured more efficiently.

  Thus, according to the base station 300 according to the fourth embodiment, the measured communication quality is compared with a plurality of quality thresholds, and the measurement processing interval is set based on the comparison result. The frequency can be changed flexibly. Thereby, communication quality can be measured more efficiently. In addition, although the case where a plurality of quality threshold values are switched according to the number of UEs has been described here, a configuration in which the plurality of quality threshold values are constant may be employed.

  As described above, according to the base station and the quality measurement method, it is possible to efficiently measure the communication quality. The following additional notes are disclosed with respect to the embodiment described above.

(Supplementary Note 1) In a base station that measures communication quality for each mobile terminal,
A receiver for receiving a reference signal transmitted from the mobile terminal;
A measurement unit that periodically performs the measurement at a measurement interval set in the mobile terminal based on a reference signal received by the reception unit;
A setting unit that sets the measurement interval based on the communication quality measured by the measurement unit;
A base station comprising:

(Supplementary Note 2) A comparison unit that compares the communication quality measured by the measurement unit with a quality threshold is provided.
The base station according to supplementary note 1, wherein the setting unit sets the measurement interval based on a comparison result by the comparison unit.

(Additional remark 3) The said setting part sets a 1st space | interval to the said measurement interval of the mobile terminal determined that the said communication quality is less than a quality threshold value by the said comparison part, and the said communication quality is more than a quality threshold value The base station according to appendix 2, wherein a second interval longer than the first interval is set as the measurement interval of the determined mobile terminal.

(Supplementary note 4) The base station according to any one of Supplementary notes 1 to 3, wherein the measurement unit estimates fading based on the reference signal as the communication quality.

(Supplementary note 5) The base station according to any one of Supplementary notes 1 to 4, wherein the measurement unit calculates a TA (Timing Adjustment) value based on the reference signal as the communication quality.

(Supplementary Note 6) A threshold setting unit that sets the quality threshold based on the number of the mobile terminals,
The base station according to supplementary note 2, wherein the comparison unit compares the quality threshold set by the threshold setting unit with the communication quality.

(Supplementary note 7) In the supplementary note 6, the threshold value setting unit sets the quality threshold value lower when the number of mobile terminals is relatively larger than when the number of mobile terminals is relatively small. The listed base station.

(Supplementary note 8) The base station according to supplementary note 3, wherein the setting unit sets the measurement interval to the first interval when the number of the mobile terminals is equal to or less than a predetermined threshold.

(Supplementary Note 9) The comparison unit compares the communication quality with a plurality of quality thresholds,
The base station according to supplementary note 2, wherein the setting unit sets the measurement interval based on a comparison result between the communication quality and a plurality of quality threshold values.

(Supplementary Note 10) In a quality measurement method of a base station that measures communication quality for each mobile terminal,
Receiving a reference signal transmitted from the mobile terminal;
Based on the reference signal received by the reception step, a measurement step of periodically performing the measurement at a measurement interval set in the mobile terminal;
A setting step for setting the measurement interval based on the communication quality measured by the measurement step;
A quality measurement method comprising:

# 0 to # 10 UE
100 communication system 301 wireless communication unit 401, 701, 1501 SRS processing interval

Claims (5)

In a base station that calculates a TA (Timing Adjustment) value for each mobile terminal,
A receiver for receiving a reference signal transmitted from the mobile terminal;
A measurement unit that periodically performs the calculation at a measurement interval set in the mobile terminal based on a reference signal received by the reception unit;
A first interval is set to the measurement interval of the mobile terminal for which the TA value calculated by the measurement unit is greater than a predetermined value, and the first interval is set to the measurement interval of the mobile terminal for which the TA value is less than or equal to the predetermined value. A setting section for setting a long second interval;
A base station comprising: In a quality measurement method of a base station that calculates a TA (Timing Adjustment) value for each mobile terminal,
Receiving a reference signal transmitted from the mobile terminal;
Based on the reference signal received by the reception step, a measurement step for performing the calculation periodically at a measurement interval set in the mobile terminal;
A first interval is set for the measurement interval of the mobile terminal for which the TA value calculated by the measurement step is greater than a predetermined value, and the first interval is set for the measurement interval of the mobile terminal for which the TA value is less than or equal to the predetermined value. A setting process for setting a long second interval;
A quality measurement method comprising: In the base station that measures the communication quality for each mobile terminal,
A receiver for receiving a reference signal transmitted from the mobile terminal;
A measurement unit that periodically performs the measurement at a measurement interval set in the mobile terminal based on a reference signal received by the reception unit;
When the number of mobile terminals is relatively large, a threshold setting unit that sets a quality threshold value lower than when the number of mobile terminals is relatively small;
A comparison unit that compares the communication quality measured by the measurement unit with the quality threshold set by the threshold setting unit;
A setting unit for setting the measurement interval based on a comparison result by the comparison unit;
A base station comprising:   The base station according to claim 3, wherein the measurement unit estimates fading based on the reference signal as the communication quality. In a quality measurement method for measuring communication quality for each mobile terminal,
Receiving a reference signal transmitted from the mobile terminal;
Based on the reference signal received by the reception step, a measurement step of periodically performing the measurement at a measurement interval set in the mobile terminal;
When the number of mobile terminals is relatively large, a threshold setting step for setting a quality threshold value lower than when the number of mobile terminals is relatively small;
A comparison step for comparing the communication quality measured by the measurement step with the quality threshold set by the threshold setting step;
A setting step for setting the measurement interval based on a comparison result by the comparison step;
A quality measurement method comprising:

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