Patent Publication Number: US-10779279-B2

Title: Wireless station, network device, control method, storage medium storing program, and communication system for calculating an available bandwidth in a wireless link

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/JP2017/014177 filed Apr. 5, 2017, claiming priority based on Japanese Patent Application No. 2016-077734 filed Apr. 8, 2016, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a wireless station, a network device, a control method, and a program. 
     BACKGROUND ART 
     In a mobile network, a traffic having a high real-time characteristic such as Web browsing, video viewing, or communication is handled. Moreover, not only a traffic having a high real-time characteristic, but also various kinds of traffics such as a traffic having a low real-time characteristic including content downloading and application updating are equally handled in a mixed and undistinguished manner. Thus, there has been a problem that communication quality of all traffics deteriorates when a peak load is generated. 
     There is an off-peak data transfer technique of transferring a traffic having a low real-time characteristic such as content downloading by utilizing an available bandwidth of a wireless link. The off-peak data transfer technique makes it possible to equalize a peak load in a wireless link without deteriorating communication quality of a traffic having a high real-time characteristic such as Web browsing. 
     The off-peak data transfer technique has an issue of how precisely an available bandwidth (a currently available bandwidth, e.g., a value represented by bit/s) in a wireless link is estimated. 
     Furthermore, in a mobile network, in order to improve communication quality of a wireless link and maintain sufficient communication service quality, a network operator needs to investigate communication quality in a communication area, adjusts various parameters, and thereby improve the communication quality. Herein, communication quality refers to, for example, an available bandwidth of a wireless link, or the like. 
     Regarding a technique of estimating an available bandwidth, for example, NPL 1 discloses a method of sending out a measurement packet called a probe to a measurement target network, and, by use of information (such as one-way transfer delay time) thereby obtained, estimating an available bandwidth. 
     CITATION LIST 
     Non-Patent Literature 
     
         
         [NPL 1] “Packet-dispersion techniques and a capacity-estimation methodology” written by C. Dovrolis, P. Ramanathan, D. Moore, IEEE/ACM Transactions on Networking, Volume 12, Issue 6, pp. 963-977, December, 2004 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     A first problem is that, in a system according to NPL 1, it is not possible to precisely calculate an available bandwidth of a wireless link between a wireless base station and a measurement terminal. A reason for this is that the system according to NPL 1 operates in such a way as to estimate an available bandwidth of a bottleneck line between a measurement terminal and a measurement server, and therefore can not necessarily calculate an available bandwidth of a wireless link. 
     A second problem is that, in the method according to NPL 1, a communication load for measurement is imposed on a measurement terminal and a measurement target network. A reason for this is that it is necessary to send out a measurement packet to the measurement target network when estimating an available bandwidth. 
     Thus, in view of the problems described above, an exemplary embodiment is intended to provide a new arrangement which makes it possible to precisely calculate an available bandwidth in a wireless link while suppressing a communication load on a measurement terminal and a measurement target network. 
     Solution to Problem 
     A wireless station according to an exemplary embodiment comprises a processor. The processor is configured to calculate an available bandwidth in a wireless link from a bandwidth for the wireless link between a wireless station and another wireless station, a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     A network device according to another exemplary embodiment is configured to be able to communicate with a second wireless station connected to a first wireless station via a wireless link. The network device comprises a processor. The processor is configured to calculate an available bandwidth in the wireless link from a bandwidth for the wireless link, a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     A control method according to another exemplary embodiment comprises calculating an available bandwidth in a wireless link from a bandwidth for the wireless link between a first wireless station and a second wireless station, a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     A program according to another exemplary embodiment causes a computer to calculate an available bandwidth in a wireless link from a bandwidth for the wireless link between a first wireless station and a second wireless station, a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     Advantageous Effects of Invention 
     According to an exemplary embodiment, it is possible to precisely calculate an available bandwidth of a wireless link while suppressing a communication load. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual configuration diagram regarding a band estimation system according to an exemplary embodiment. 
         FIG. 2  is a schematic diagram of a method of calculating an estimated value A 1  of a bandwidth of a wireless link in  FIG. 1 . 
         FIG. 3  is a schematic diagram of a method of calculating an estimated value A 2  of a radio resource usage rate of the wireless link in  FIG. 1 . 
         FIG. 4  is a schematic diagram of a method of calculating an estimated value A 3  of an available bandwidth of a wireless link in  FIG. 1 . 
         FIG. 5A  is an explanatory diagram illustrating one example of a resource block configuration of a symbol targeted for measurement of quality indices such as total received power, reference signal received power, reference signal received quality, and a signal-to-interference noise power ratio of a reference signal. 
         FIG. 5B  illustrates one example of a resource block configuration when a number of antennas is 1. 
         FIG. 5C  illustrates one example of a resource block configuration when a number of antennas is 2. 
         FIG. 6  is a network configuration diagram when the present example embodiment is applied to a long term evolution (LTE) system. 
         FIG. 7  is a table illustrating an example of a correspondence relation between a channel quality indicator (CQI) and a signal-to-interference plus noise power ratio (SINR). 
         FIG. 8  is a table illustrating an example of a correspondence relation between a CQI, a total number of resource blocks, and a payload size per resource block. 
         FIG. 9  is a table illustrating an example of a correspondence relation between a CQI and throughput per resource block. 
         FIG. 10  is a table illustrating an example of a correspondence relation between an SINR and throughput per resource block. 
         FIG. 11  is a configuration diagram illustrating a band estimation system according to a first exemplary embodiment. 
         FIG. 12A  is a configuration diagram illustrating one example of a method of displaying an estimated available bandwidth of a wireless link. 
         FIG. 12B  is a configuration diagram illustrating another example of a method of displaying an estimated available bandwidth of a wireless link. 
         FIG. 12C  is a configuration diagram illustrating yet another example of a method of displaying an estimated available bandwidth of a wireless link. 
         FIG. 13  is a configuration diagram illustrating a band estimation system according to a second exemplary embodiment. 
         FIG. 14  is a conceptual diagram regarding a sixth exemplary embodiment. 
         FIG. 15  is a conceptual diagram regarding a seventh exemplary embodiment. 
         FIG. 16  is a diagram illustrating an overview of an experiment of estimating an available bandwidth of a wireless link. 
         FIG. 17  is a graph illustrating a result of an experiment of estimating an available bandwidth of a wireless link. 
     
    
    
     EXAMPLE EMBODIMENT 
     Overview of Exemplary Embodiment 
     Next, an exemplary embodiment is presented with reference to the drawings. In the respective drawings, identical or corresponding elements are given identical reference signs, and for clarification of a description, a repeated description is omitted as needed. A plurality of exemplary embodiments described below can be independently implemented, or suitably implemented in combination. 
     As illustrated in  FIG. 1 , according to the present example embodiment, an available bandwidth estimation function X 1  calculates (and/or estimates) an available bandwidth of a wireless link by use of at least one of a first quality index P 1  including total received power measured by a wireless station, a second quality index P 2  including reference signal received power, a third quality index P 3  including reference signal received quality, and a fourth quality index P 4  including a signal-to-interference noise power ratio of the reference signal. 
     Herein, a wireless station is a device having a wireless communication function in a wireless communication system. Note that a wireless station may be a wireless terminal, a user terminal, a mobile station, a user equipment (UE), a wireless base station, an evolved Node B (eNodeB or eNB), or the like. 
     The first quality index P 1  including the total received power (received signal strength) is, for example, a received signal strength indicator (RSSI) and the like. The second quality index P 2  including the reference signal received power is, for example, reference signal received power (RSRP) and the like. The third quality index P 3  including the reference signal received quality is, for example, reference signal received quality (RSRQ) and the like. The fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal is, for example, a signal-to-interference plus noise power ratio (SINR) and the like. 
     The available bandwidth estimation function X 1  may be provided in, for example, a wireless station or a network upper device managing a wireless station. The available bandwidth estimation function X 1  executes an available bandwidth estimation described next. 
     &lt;Available Bandwidth Estimation&gt; 
       FIG. 2  is a schematic diagram of a method of calculating an estimated value A 1  of a bandwidth of a wireless link in an exemplary embodiment. In  FIG. 2 , an available bandwidth estimation function X 1 - 1  calculates the estimated value A 1  of the bandwidth of the wireless link by use of the first quality index P 1  including the total received power measured at the wireless station, the second quality index P 2  including the reference signal received power, and the third quality index P 3  including the reference signal received quality. 
       FIG. 3  is a schematic diagram of a method of calculating an estimated value A 2  of a radio resource usage rate of a wireless link in an exemplary embodiment. In  FIG. 3 , an available bandwidth estimation function X 1 - 2  calculates the estimated value A 2  of the radio resource usage rate of the wireless link by use of the third quality index P 3  including the reference signal received quality, and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal. 
       FIG. 4  is a schematic diagram of a method of calculating an estimated value A 3  of an available bandwidth of a wireless link. In  FIG. 4 , an available bandwidth estimation function X 1 - 3  calculates the estimated value A 3  of the available bandwidth of the wireless link by use of the estimated value A 1  of the bandwidth of the wireless link, the estimated value A 2  of the radio resource usage rate of the wireless link, and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal. 
     Hereinafter, a basic procedure of the available bandwidth estimation is described taking, as an example, a long term evolution (LTE) system a specification of which is prescribed by third generation partnership project (3GPP) and the like. 
       FIG. 5A  is an explanatory diagram illustrating one example of a resource block configuration used for orthogonal frequency division multiple access (OFDMA). Note that  FIG. 5B  is an example of a resource block configuration when a number of antennas used for signal transmission is 1.  FIG. 5C  is an example of a resource block configuration when a number of antennas used for signal transmission is 2. In  FIGS. 5A to 5C , individual squares are equivalent to resource elements. An orthogonal frequency division multiplexing (OFDM) symbol at a certain time includes not only a data signal or a control signal, but also a reference signal. Moreover, when a number of antennas is 2 or more, an unused resource element is included in some cases, as illustrated in  FIG. 5C . 
       FIG. 6  is a network configuration diagram in the case of application to an LTE system. A wireless communication system including a wireless station D 1  which manages a cell, and a wireless station D 2  which receives a reference signal, a data signal, or a control signal from the wireless station D 1  is illustrated in  FIG. 6 . Herein, it is assumed that an available bandwidth of a wireless link seen from the wireless station D 2  is estimated. 
     The available bandwidth estimation function X 1  calculates the estimated value A 1  of the bandwidth of the wireless link by, for example, the following expression, using the RSSI (first quality index P 1 ), the RSRP (second quality index P 2 ), and the RSRQ (third quality index P 3 ) measured at the wireless station D 2 . 
               A   ⁢           ⁢   1     =       RSSI   ·   RSRQ     RSRP           
Herein, the estimated value A 1  of the bandwidth of the wireless link is represented by a total number of allocatable resource blocks. A resource block is a minimum allocation unit of a radio resource in a wireless link (cell).
 
     The available bandwidth estimation function X 1  may calculate, from time-series data A 1 ( t ) of an estimated value of a bandwidth of a wireless link, an average value thereof in a certain period, for example, and calculate the estimated value A 1  of the bandwidth of the wireless link. However, t represents a time when A 1 ( t ) are measured. 
     When the wireless station D 2  can obtain a true value of the bandwidth of the wireless link from exchange of a control signal with the wireless station D 1 , the available bandwidth estimation function X 1  may set the true value as A 1 . 
     Note that, when a center frequency (or E-UTRA absolute radio frequency channel number (EARFCN)) of a wireless link can be obtained (measured or detected), a bandwidth may be estimated from the center frequency (or EARFCN) by use of a fact that a relation between the center frequency (or EARFCN) and a bandwidth is fixed. In order to execute such processing, the available bandwidth estimation function X 1  may hold a table indicating a relation between the center frequency (or EARFCN) and a bandwidth. 
     Moreover, because a center frequency and a bandwidth of a wireless link are set for each wireless station D 1 , the wireless station D 2  may estimate or obtain a bandwidth of a wireless link at timing when the wireless station D 1  which is a connection destination of the wireless station D 2  changes. For example, the wireless station D 2  estimates or obtains a bandwidth of a wireless link at timing when handover is detected. At timing other than the timing described above, the wireless station D 2  utilizes a bandwidth of a wireless link estimated or obtained in the past. 
     The available bandwidth estimation function X 1  calculates the estimated value A 2  of the radio resource usage rate of the wireless link by, for example, the following expression, using the third quality index P 3  including the reference signal received quality measured at the wireless station D 1 , and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal. Note that it is assumed that a number of antennas used by the wireless station D 1  for signal transmission is N TX , and an adjustment term such as transmission power or a resource block structure when the wireless station D 1  transmits a signal is α. σ represents an adjustment term such as noise power. α and σ may be fixed values or variable values. 
     
       
         
           
             
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     Herein, the estimated value A 2  of the radio resource usage rate of the wireless link is represented by a resource block usage rate. A resource block is a minimum allocation unit of a radio resource in a wireless link. A resource block usage rate is a value obtained by dividing a resource block usage number of a wireless link by a total number of allocatable resource blocks. 
     The available bandwidth estimation function X 1  may calculate, from time-series data A 2 ( t ) of an estimated value of a radio resource usage rate, an average value thereof in a certain period, for example, and calculate the estimated value A 2  of the radio resource usage rate. However, t represents a time when A 2 ( t ) are measured. 
     The available bandwidth estimation function X 1  calculates the estimated value A 3  of the available bandwidth of the wireless link by, for example, the following procedure, using the estimated value A 1  of the bandwidth of the wireless link, the estimated value A 2  of the radio resource usage rate of the wireless link, and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal.
 
 A 3 =A 1·(1 −A 2)· F ( P 4)
 
Herein, F(P 4 ) is a function of the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal, and represents an expectation value of throughput [bit/s] per resource block.
 
     The available bandwidth estimation function X 1  may set, as a final available bandwidth value, a value obtained by performing predetermined computation processing on the estimated value A 3  of the available bandwidth calculated as described above. The available bandwidth estimation function X 1  may calculate, for example, a final estimated value of an available bandwidth as β×A 3 . Herein, β is a parameter changing in value depending on a bandwidth of a wireless link, a transmission mode of a wireless signal, a scheduling characteristic of a radio resource in the wireless station D 1 , and the like. β may be a fixed value or a variable value. 
     A function F (SINR) is more specifically described with P 4  as an SINR. 
     First, for example, the available bandwidth estimation function X 1  calculates a channel quality indicator (CQI) which is quality information of a downlink from an SINR[dB] of the downlink, using a reference table as illustrated in  FIG. 7 . Alternatively, quality information of a downlink may be represented by the SINR itself. Then, a payload size [bit] per resource block is calculated from the CQI and a total number of resource blocks, by use of a reference table as illustrated in  FIG. 8 . For this payload size, an expectation value of throughput [bit/s] per resource block needs only to be calculated on the basis of an averaging section defined by time, for example, transmission time interval (TTI) which is a minimum time interval of scheduling and the like. 
     Alternatively, as illustrated in  FIG. 9 , throughput [Mbit/s] per resource block may be directly calculated from a CQI, using data in which a CQI is associated with throughput [Mbit/s] per resource block. 
     Alternatively, as illustrated in  FIG. 10 , throughput [Mbit/s] per resource block may be directly calculated from an SINR, using data in which a range of an SINR is associated with throughput [Mbit/s] per resource block. 
     Note that the available bandwidth estimation function X 1  may calculate the estimated value A 3  of the available bandwidth of the wireless link by, for example, the following expression, using the estimated value A 1  of the bandwidth of the wireless link, the estimated value A 2  of the radio resource usage rate of the wireless link, and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal.
 
 A 3=(1 −A 2)· G ( P 4 ,A 1)
 
or
 
 A 3 =G ( P 4 ,A 1·(1 −A 2))
 
Herein, a function G(x, y) represents throughput at which the fourth quality index (SINR) is expected when a bandwidth (total number of resource blocks) is y. For example, with LTE, a modulation and coding scheme (MCS) used for transmission of a wireless signal is determined depending on the SINR. Further, a transport block size is determined by the determined MCS, and a number of resource blocks available at this time. On the basis of this transport block size, throughput of a wireless section can be calculated. The above-described function G may be a transport block size which is obtained under a predetermined MCS and a number of resource blocks, and which is previously held in a form such as a table.
 
     The available bandwidth estimation function X 1  may set, as a final estimated available bandwidth, a value obtained by performing predetermined computation processing on the estimated value A 3  of the available bandwidth calculated as described above. For example, the available bandwidth estimation function X 1  may calculate a final estimated value of an available bandwidth as β×A 3 . Herein, β is a parameter changing in value depending on a bandwidth of a wireless link, a transmission mode of a wireless signal, a scheduling characteristic of a radio resource in the wireless station D 1 , and the like. β may be a fixed value or a variable value. 
     For example, when a number of spatial multiplexing (a number of layers, a number of streams, or a number of ranks) by multiple-input multiple-output (MIMO) can be obtained (measured or detected) as a transmission mode, β may be set depending on a number of spatial multiplexing. For example, β=1 when a number of spatial multiplexing is 1, and β=2 when a number of spatial multiplexing is 2. Moreover, in general, when an SINR is better, there is a higher possibility that a higher number of spatial multiplexing can be used, and therefore, an SINR may be converted into β (a real number of 1 or more and N or less) by a function having a positive correlation with the SINR. Herein, N is a maximum number of spatial multiplexing. Note that MIMO is a scheme (multi-antenna transmission) which divides transmission data into a plurality of signals (streams) in advance, and simultaneously transfers the signals from a plurality of antennas (multi-antenna) on the same frequency band. 
     As another example of setting β, the following method may be used. For example, throughput (TP) between the wireless station D 1  and the wireless station D 2  is measured at timing when a communication by the wireless station D 2  occurs. Moreover, the estimated value A 3  of the available bandwidth is also calculated by the method described above. Then, a value of β is calculated by β=TP/A 3 . Once β is calculated, only the estimated value A 3  of the available bandwidth is calculated without measuring throughput (TP) between the wireless station D 1  and the wireless station D 2 , and thereby, an available bandwidth can be estimated by β×A 3 . 
     Note that estimated values are used for a radio resource usage rate and a bandwidth in the case described above, but when a radio resource usage rate and a bandwidth can be obtained (measured or detected) without performing estimation, the obtained values (measured or detected values) may be used instead of estimated values. 
     Furthermore, the wireless station D 1  or the wireless station D 2  may include a communication control function of controlling communication depending on an available bandwidth of a wireless link. For example, the wireless station D 1  or the wireless station D 2  performs predetermined communication processing when an available bandwidth of a wireless link satisfies a predetermined condition. 
     For example, when an available bandwidth of a wireless link is equal to or more than a predetermined value or more than a predetermined value, the wireless station D 2  downloads a predetermined file from a server. Thus, the wireless station D 2  may include a function of previously scheduling and holding processing executed when there is an enough available bandwidth of a wireless link. 
     As another example, the wireless station D 1  may instruct to switch a connection destination of the wireless station D 2  to another wireless station having a larger available bandwidth of a wireless link or another frequency when an available bandwidth of a wireless link regarding the wireless station D 2  requesting a communication start is less than a predetermined value or equal to or less than a predetermined value. A predetermined value of an available bandwidth may be an absolute value (e.g., 1 Mbps), or determined depending on an application or a quality class indicator (QCI). For example, a predetermined value of an available bandwidth may be set to a 5 Mbps when an application is a moving image, or 1 Mbps when an application is a Web. 
     As described above, communication control performed by the communication control function may be control performed by use of the same wireless link, or may be control of switching a wireless link itself. 
     As described above, according to the present example embodiment, an available bandwidth of a wireless link is estimated by the available bandwidth estimation function X 1  by use of the first quality index P 1  including the total received power measured at the wireless station D 2 , the second quality index P 2  including the reference signal received power, the third quality index P 3  including the reference signal received quality, and the fourth quality index P 4  including the signal-to-interference noise power ratio of the reference signal. This makes it possible to precisely calculate an available bandwidth of a wireless link without imposing a communication load. 
     In the above description, details of the conceptual configuration and operation according to the exemplary embodiment have been presented. Hereinafter, a specific configuration example according to an example embodiment is presented. 
     First Exemplary Embodiment 
     As illustrated in  FIG. 11 , a band estimation system according to a first exemplary embodiment is configured to include a wireless station D 1  and a wireless station D 2 , as well as an available bandwidth estimation unit Y 1 , a wireless communication unit Y 2 , and an available bandwidth estimation function X 1  in the wireless station D 2 . 
     According to the present example embodiment, an available bandwidth of a wireless link is calculated (estimated) by the available bandwidth estimation function X 1  of the available bandwidth estimation unit Y 1 , using a first quality index P 1  including total received power measured by the wireless communication unit Y 2  of the wireless station D 2 , a second quality index P 2  including reference signal received power, a third quality index P 3  including reference signal received quality, and a fourth quality index P 4  including a signal-to-interference noise power ratio of the reference signal. 
     Note that the wireless station D 2  may display an available bandwidth of a wireless link by use of a display means (e.g., a display unit or a display) of the wireless station D 2 . A display example of an available bandwidth of a wireless link is illustrated in  FIG. 12A ,  FIG. 12B , and  FIG. 12C . In  FIG. 12A , in a notification region  1000  in a display upper part, radio quality (e.g., reference signal received power and reference signal received quality) is displayed by a number of antennas  1001 , and an available bandwidth of a wireless link is displayed by numerical information  1002 . In  FIG. 12B , in a notification region  1000  in a display upper part, radio quality (e.g., reference signal received power and reference signal received quality) is displayed by a number of antennas  1001 , and an available bandwidth of a wireless link is displayed by an indicator  1003 . In  FIG. 12C , an available bandwidth of a wireless link is displayed by use of a number of antennas  1004 . 
     According to the present example embodiment, it is possible to precisely calculate (estimate) an available bandwidth of a wireless link without imposing a communication load. 
     Second Exemplary Embodiment 
     As illustrated in  FIG. 13 , a band estimation system according to a second exemplary embodiment is configured to include a wireless station D 1 , a wireless station D 2 , and a data processing device D 3 . The wireless station D 2  includes a wireless communication unit Y 2 . The data processing device D 3  includes an available bandwidth estimation unit Y 1  and an available bandwidth estimation function X 1 . 
     According to the present example embodiment, an available bandwidth of a wireless link is estimated by the available bandwidth estimation function X 1  of the available bandwidth estimation unit Y 1 , using a first quality index P 1  including total received power measured by the wireless communication unit Y 2  of the wireless station D 2 , a second quality index P 2  including reference signal received power, a third quality index P 3  including reference signal received quality, and a fourth quality index P 4  including a signal-to-interference noise power ratio of the reference signal. 
     According to the present example embodiment, it is possible to precisely calculate (estimate) an available bandwidth of a wireless link without imposing a communication load. 
     Third Exemplary Embodiment 
     According to the present example embodiment, statistical processing is performed on time-series data of a measured estimated value A 3  of an available bandwidth of a wireless link, in order to suppress variation of an estimation result of an available bandwidth of a wireless link. Specifically, time-series data of the estimated value A 3  of the available bandwidth of the wireless link are collected over a certain period (e.g., 1 second, 10 seconds, 1 minute, 1 hour or the like), and subjected to statistical processing. Average or weighting processing, or the like can be used as statistical processing. 
     According to the present example embodiment, it is possible to observe an available bandwidth fluctuation of a wireless link in a desired particle size. 
     Fourth Exemplary Embodiment 
     According to the present example embodiment, time-series data of an estimated value A 3  of an available bandwidth of a wireless link held by a plurality of wireless stations D 2  are collected by a server on a network, and subjected to statistical processing together with a place of measurement, and position information of a wireless station D 1  or a wireless station D 2 . Thereby, an available bandwidth of a wireless link is displayed on a map. For example, a communication area may be separated by colors depending on an available bandwidth of a wireless link, or color separation of a communication area may also be changed depending on a fluctuation of an available bandwidth of a wireless link, and thus displayed like animation. Time-series data may be collected by the server in a free time zone in which a wireless link is free. 
     According to the present example embodiment, it is possible to observe quality of a communication area by visualizing an available bandwidth fluctuation in a wireless link on a map. Further, by investigating communication quality in a communication area, and adjusting various parameters, it is possible to use as a means of improving the communication quality. 
     Fifth Exemplary Embodiment 
     According to the present example embodiment, a server on a network collects time-series data of an estimated value A 3  of an available bandwidth of a wireless link held by a plurality of wireless stations D 2 , and performs statistical processing on the time-series data of the estimated value A 3  of the available bandwidth of each wireless link collected from the plurality of wireless stations D 2 . Average or weighting processing, or the like can be used as statistical processing. 
     According to the present example embodiment, it is possible to more precisely estimate an available bandwidth of a wireless link by increasing a number of samples of the estimated value A 3  of the available bandwidth of the wireless link. 
     Sixth Exemplary Embodiment 
       FIG. 14  is a conceptual diagram illustrating a sixth exemplary embodiment. In  FIG. 14 , a wireless station  100  includes a processor  101 . The processor  101  is configured to calculate an available bandwidth in a wireless link from a bandwidth for a wireless link between the wireless station  100  and another wireless station  200 , a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     According to the present example embodiment, a wireless station can precisely calculate (estimate) an available bandwidth of a wireless link without imposing a communication load. 
     Seventh Exemplary Embodiment 
       FIG. 15  is a conceptual diagram illustrating a seventh exemplary embodiment. In  FIG. 15 , a network device  330  is configured to be able to communicate with a second wireless station  320  connected to a first wireless station  310  via a wireless link. Moreover, the network device  330  includes a processor  331 . The processor  331  is configured to calculate an available bandwidth in the wireless link described above from a bandwidth for a wireless link, a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and radio quality of the wireless link. 
     According to the present example embodiment, the network device can precisely calculate (estimate) an available bandwidth of a wireless link without imposing a communication load. 
     EXAMPLE 
     As illustrated in  FIG. 16 , an experiment was conducted on an actual LTE network, in which actual terminal received throughput was compared with an estimated value of an available bandwidth calculated by the bandwidth estimation method described above. As a result of this experiment, as illustrated in  FIG. 17 , a strong correlation was seen between the actual terminal received throughput and the estimated value of the available bandwidth calculated by the bandwidth estimation method described above (a correlation coefficient of 0.719). 
     Other Exemplary Embodiments 
     In the above description, an “available bandwidth” is also referred to as an available bandwidth, a surplus bandwidth, or a usable bandwidth. An “available bandwidth” can also be represented as an available bandwidth, an unoccupied bandwidth, a residual bandwidth, an excess bandwidth, a free bandwidth, or an unused bandwidth. 
     In the above description, the available bandwidth estimation function X 1  calculates the estimated value A 2  of the radio resource usage rate of the wireless link by use of the third quality index P 3  and the fourth quality index P 4 , but a method of calculating the estimated value A 2  is not limited thereto. The available bandwidth estimation function X 1  can calculate the estimated value A 2  of the radio resource usage rate of the wireless link by use of at least one of the first quality index P 1 , the third quality index P 3 , and the fourth quality index P 4 . Specifically, the estimated value A 2  can be calculated on the basis of one of the first quality index P 1 , the third quality index P 3 , and the fourth quality index P 4 . Alternatively, the estimated value A 2  can be calculated on the basis of the first quality index P 1  and the third quality index P 3 . Alternatively, the estimated value A 2  can be calculated on the basis of the third quality index P 3  and the fourth quality index P 4 . Alternatively, the estimated value A 2  can be calculated on the basis of the first quality index P 1  and the fourth quality index P 4 . Alternatively, the estimated value A 2  can be calculated on the basis of the first quality index P 1 , the third quality index P 3 , and the fourth quality index P 4 . Alternatively, the estimated value A 2  can be calculated on the basis of the first quality index P 1 , the second quality index P 2 , and the fourth quality index P 4 . 
     The first quality index P 1 , the second quality index P 2 , the third quality index P 3 , and the fourth quality index P 4  can be measured at a wireless station. Measured measurement information (the first quality index P 1 , the second quality index P 2 , the third quality index P 3 , and the fourth quality index P 4 ) can be transmitted to a network device from the wireless station. Measured measurement information (the first quality index P 1 , the second quality index P 2 , the third quality index P 3 , and the fourth quality index P 4 ) measured during a certain period is put together as time-series data, and then the time-series data may be transmitted to a network device from the wireless station. The network device may perform the above-described operation of calculating an estimated value of an available bandwidth by use of the measurement information received from the wireless station. 
     The network device described above may be a network upper device, a core network node, an upper device, a node, a management device, a management node, a server, or the like. 
     Although a target for calculating an available bandwidth is a wireless link in a down direction in the example embodiment described above, an available bandwidth of a wireless link in an up direction (uplink) may be calculated. 
     Moreover, although an LTE scheme wireless communication system is presented as an example in the example embodiment described above, at least some of methods and devices in various example embodiments are applicable to a wide range of communication systems including many non-LTE and/or non-cellular systems. For example, the example embodiment described above may be a universal mobile telecommunications system (UMTS) scheme. Alternatively, the example embodiment described above may be a wireless communication system which adopts a frequency division duplex (FDD) scheme that simultaneously uses different frequencies in an up line and a down line. Alternatively, the example embodiment described above may be a different wireless communication system which adopts a time division duplex (TDD) scheme that uses the same frequency in an up line and a down line by time. Alternatively, the example embodiment described above may be a wireless communication system which adopts a carrier aggregation (CA) scheme that accelerates communication by simultaneously utilizing radiowaves on a plurality of frequency bandwidths, and transmitting and receiving data in a distributed manner as one communication line. In the case of CA, an available bandwidth of a wireless link is calculated for each of a primary cell (PCELL) and a secondary cell (SCELL). 
     Alternatively, a computer program (hereinafter, referred to as a program) in which processing contents are described as a procedure may be recorded in a readable recording medium in each element (terminal, base station, or network device) constituting a communication system (wireless communication system), and the program recorded in the recording medium may be read into each component of the communication system and executed. 
     Alternatively, a computer program (hereinafter, referred to as a program) in which processing contents are described as a procedure may be recorded in a readable recording medium in each element constituting a communication system, and the program recorded in the recording medium may be read into each component of the communication system and executed. 
     The program recorded in the recording medium is read in a central processing unit (CPU) provided in each component of the communication system, and processing similar to that described above is performed under the control of the CPU. Herein, the CPU operates as a computer that executes the program read from the recording medium in which the program is recorded. 
     In the example described above, the program can be stored by use of various types of non-transitory computer readable media, and supplied to a computer. The non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include a magnetic recording medium (e.g., a flexible disc, a magnetic tape, and a hard disc drive), a magneto-optical recording medium (e.g., a magneto-optical disc), a compact disc (CD)-read only memory (ROM), a CD-R, a CD-R/W, a digital versatile disc (DVD), and a semiconductor memory (e.g., a mask ROM, a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, and a random access memory (RAM)). Moreover, a program may be supplied to a computer by various types of transitory computer readable media. Examples of transitory computer readable media include an electric signal, an optical signal, and an electromagnetic wave. A transitory computer readable medium can supply a program to a computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path. 
     Furthermore, the present invention is not limited solely to the example embodiments described above, and it goes without saying that various modifications can be made without departing from the spirit of the present invention already described. The functions or steps and/or operations according to each example embodiment described in the present description do not need to be executed in a particular order. Additionally, an element according to the present invention is described or claimed in a singular form in some cases, but may be in a plural form unless otherwise explicitly described as being limited to a singular form. 
     While the invention of the present application has been described with reference to the example embodiments, the invention of the present application is not limited to the example embodiments described above. Various changes that can be appreciated by a person skilled in the art can be made to a configuration and details of the invention of the present application within the scope of the invention of the present application. 
     &lt;Supplementary Note&gt; 
     Some or all of the example embodiments and examples described above can also be described as in Supplementary notes below, but are not limited to the followings. 
     (Supplementary note 1) 
     A communication system configured to 
     calculate an available bandwidth in a wireless link from 
     a bandwidth of the wireless link, 
     a radio resource usage rate of the wireless link, and 
     radio quality of the wireless link. 
     (Supplementary Note 32) 
     The communication system according to Supplementary note 1, wherein 
     at least any one of the bandwidth or the radio resource usage rate is estimated 
     by use of at least any one of 
     a first quality index including received signal strength total received power, 
     a second quality index including received power of a reference signal, 
     a third quality index including received quality of the reference signal, and 
     a fourth quality index including a signal-to-interference noise power ratio of the reference signal, 
     the first to fourth quality indices being measured regarding the wireless link. 
     (Supplementary note 3) 
     The communication system according to Supplementary note 2, wherein 
     the radio resource usage rate is estimated by use of at least one of the third quality index and the fourth quality index. 
     (Supplementary note 4) 
     The communication system according to Supplementary note 2 or 3, wherein 
     the bandwidth is estimated 
     from the first quality index, the second quality index, and the third quality index. 
     (Supplementary note 5) 
     The communication system according to any one of Supplementary notes 1 to 4, wherein 
     an estimated value of the available bandwidth is calculated further in consideration of a transmission mode of the wireless link. 
     (Supplementary note 6) 
     The communication system according to any one of Supplementary notes 1 to 5, wherein 
     the radio quality of the wireless link is a signal-to-interference noise power ratio of a reference signal. 
     (Supplementary note 7) 
     The communication system according to any one of Supplementary notes 1 to 6, wherein 
     the bandwidth is represented by a total number of frequency blocks. 
     (Supplementary note 8) 
     The communication system according to any one of Supplementary notes 1 to 7, wherein 
     the radio resource usage rate is a ratio of a number of frequency blocks used for signal transfer, to a total number of frequency blocks. 
     (Supplementary note 9) 
     The communication system according to any one of Supplementary notes 1 to 8, wherein 
     the available bandwidth represents an amount of data transmittable per unit time in a wireless link in a down direction. 
     (Supplementary note 10) 
     The communication system according to any one of Supplementary notes 5 to 9, wherein 
     a transmission mode of the wireless link is a transmission mode of multi-antenna transmission. 
     (Supplementary note 11) 
     The communication system according to any one of Supplementary notes 1 to 10, further comprising: 
     a communication control function which executes communication control when an estimated value of the available bandwidth satisfies a predetermined condition. 
     (Supplementary note 12) 
     The communication system according to any one of Supplementary notes 2 to 11, further comprising: 
     a display unit which displays at least one of 
     the calculated available bandwidth, and 
     radio quality of received reference signal. 
     (Supplementary note 13) 
     A control method comprising: 
     calculating an available bandwidth in a wireless link from 
     a bandwidth for the wireless link between a first wireless station and a second wireless station, 
     a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and 
     radio quality of the wireless link. 
     (Supplementary note 14) 
     The control method according to Supplementary note 13, wherein 
     at least one of the bandwidth and the radio resource usage rate is estimated 
     by use of at least one of 
     a first quality index including total received power measured at the first wireless station, 
     a second quality index including received power of a reference signal transmitted to the first wireless station from the second wireless station, 
     a third quality index including received quality of the reference signal, and 
     a fourth quality index including a signal-to-interference noise power ratio of the reference signal. 
     (Supplementary note 15) 
     The control method according to Supplementary note 14, wherein 
     the radio resource usage rate is estimated by use of at least one of the first quality index, the third quality index, and the fourth quality index. 
     (Supplementary note 16) 
     The control method according to Supplementary note 14 or 15, wherein 
     the bandwidth is estimated, 
     based on the first quality index, the second quality index, and the third quality index. 
     (Supplementary note 17) 
     The control method according to any one of Supplementary notes 13 to 16, wherein 
     the available bandwidth is calculated further in consideration of a transmission mode of multi-antenna transmission of the wireless link. 
     (Supplementary note 18) 
     The control method according to any one of Supplementary notes 13 to 17, wherein 
     the radio quality of the wireless link is a signal-to-interference noise power ratio of a reference signal transmitted to the first wireless station from the second wireless station. 
     (Supplementary note 19) 
     The control method according to any one of Supplementary notes 13 to 18, wherein 
     when the available bandwidth satisfies a predetermined condition, a wireless communication of the first wireless station is controlled. 
     (Supplementary note 20) 
     The control method according to any one of Supplementary notes 14 to 19, wherein 
     at least one of 
     the calculated available bandwidth, and 
     radio quality of a reference signal transmitted to the first wireless station from the second wireless station is displayed. 
     (Supplementary note 21) 
     A program which causes a computer to: 
     calculate an available bandwidth in a wireless link from 
     a bandwidth for the wireless link between a first wireless station and a second wireless station, 
     a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and 
     radio quality of the wireless link. 
     (Supplementary note 22) 
     The program according to Supplementary note 21, wherein 
     at least one of the bandwidth and the radio resource usage rate is estimated 
     by use of at least one of 
     a first quality index including total received power measured at the first wireless station, 
     a second quality index including received power of a reference signal transmitted to the first wireless station from the second wireless station, 
     a third quality index including received quality of the reference signal, and 
     a fourth quality index including a signal-to-interference noise power ratio of the reference signal. 
     (Supplementary note 23) 
     The program according to Supplementary note 22, wherein 
     the radio resource usage rate is estimated by use of at least one of the first quality index, the third quality index, and the fourth quality index. 
     (Supplementary note 24) 
     The program according to Supplementary note 22 or 23, wherein 
     the bandwidth is estimated, 
     based on the first quality index, the second quality index, and the third quality index. 
     (Supplementary note 25) 
     The program according to any one of Supplementary notes 21 to 24, wherein 
     the available bandwidth is calculated further in consideration of a transmission mode of multi-antenna transmission of the wireless link. 
     (Supplementary note 26) 
     The program according to any one of Supplementary notes 21 to 25, wherein 
     the radio quality of the wireless link is a signal-to-interference noise power ratio of a reference signal transmitted to the first wireless station from the second wireless station. 
     (Supplementary note 27) 
     The program according to any one of Supplementary notes 21 to 26, wherein 
     when the available bandwidth satisfies a predetermined condition, a wireless communication of the first wireless station is controlled. 
     (Supplementary note 28) 
     The program according to any one of Supplementary notes 22 to 27, wherein 
     at least one of 
     the calculated available bandwidth, and 
     radio quality of a reference signal transmitted to the first wireless station from the second wireless station is displayed. 
     (Supplementary note 29) 
     A network device configured to be able to communicate with a second wireless station connected to a first wireless station via a wireless link, the network device comprising: 
     a processor configured to calculate an available bandwidth in the wireless link from 
     a bandwidth for the wireless link, 
     a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and 
     radio quality of the wireless link. 
     (Supplementary note 30) 
     The network device according to Supplementary note 29, wherein 
     the processor estimates at least one of the bandwidth and the radio resource usage rate 
     by use of at least one of 
     a first quality index including total received power measured at the first wireless station, 
     a second quality index including received power of a reference signal transmitted to the first wireless station from the second wireless station, 
     a third quality index including received quality of the reference signal, and 
     a fourth quality index including a signal-to-interference noise power ratio of the reference signal. 
     (Supplementary note 31) 
     The network device according to Supplementary note 30, wherein 
     the radio resource usage rate is estimated by use of at least one of the first quality index, the third quality index, and the fourth quality index. 
     (Supplementary note 32) 
     The network device according to Supplementary note 30 or 31, wherein 
     the bandwidth is estimated, 
     based on the first quality index, the second quality index, and the third quality index. 
     (Supplementary note 33) 
     The network device according to any one of Supplementary notes 29 to 32, wherein 
     the processor calculates the available bandwidth further in consideration of a transmission mode of multi-antenna transmission of the wireless link. 
     (Supplementary note 34) 
     The network device according to any one of Supplementary notes 29 to 33, wherein 
     the radio quality of the wireless link is a signal-to-interference noise power ratio of a reference signal transmitted to the first wireless station from the second wireless station. 
     (Supplementary note 35) 
     The network device according to any one of Supplementary notes 29 to 34, wherein 
     when the available bandwidth satisfies a predetermined condition, a wireless communication of the first wireless station is controlled. 
     (Supplementary note 36) 
     A wireless station comprising: 
     a processor configured to calculate an available bandwidth in a wireless link from 
     a bandwidth for the wireless link between a wireless station and another wireless station, 
     a radio resource usage rate which is a ratio of a number of frequency blocks used for signal transfer, to a plurality of frequency blocks constituting the bandwidth, and 
     radio quality of the wireless link. 
     (Supplementary note 37) 
     The wireless station according to Supplementary note 36, wherein 
     the processor estimates at least one of the bandwidth and the radio resource usage rate 
     by use of at least one of 
     a first quality index including total received power measured at the wireless station, 
     a second quality index including received power of a reference signal received from the other wireless station, 
     a third quality index including received quality of the reference signal, and 
     a fourth quality index including a signal-to-interference noise power ratio of the reference signal. 
     (Supplementary note 38) 
     The wireless station according to Supplementary note 37, wherein 
     the radio resource usage rate is estimated by use of at least one of the first quality index, the third quality index, and the fourth quality index. 
     (Supplementary note 39) 
     The wireless station according to Supplementary note 37 or 38, wherein 
     the bandwidth is estimated, 
     based on the first quality index, the second quality index, and the third quality index. 
     (Supplementary note 40) 
     The wireless station according to any one of Supplementary notes 36 to 39, wherein 
     the processor calculates the available bandwidth further in consideration of a transmission mode of multi-antenna transmission of the wireless link. 
     (Supplementary note 41) 
     The wireless station according to any one of Supplementary notes 36 to 40, wherein 
     the radio quality of the wireless link is a signal-to-interference noise power ratio of a reference signal received from the other wireless station. 
     (Supplementary note 42) 
     The wireless station according to any one of Supplementary notes 36 to 41, wherein 
     when the available bandwidth satisfies a predetermined condition, a wireless communication of the wireless station is controlled. 
     REFERENCE SIGNS LIST 
     
         
         X 1 , X 1 - 1 , X 1 - 2 , X 1 - 3  Available bandwidth estimation function 
         P 1  First quality index 
         P 2  Second quality index 
         P 3  Third quality index 
         P 4  Fourth quality index 
         A 1  Estimated value of bandwidth of wireless link 
         A 2  Estimated value of radio resource usage rate of wireless link 
         A 3  Estimated value of available bandwidth of wireless link 
         D 1  Wireless station 
         D 2  Wireless station 
         Y 1  Available bandwidth estimation unit 
         Y 2  Wireless communication unit 
         D 3  Data processing device 
           100  Wireless station 
           101  Processor 
           200  Wireless station 
           310  Wireless station 
           320  Wireless station 
           330  Network device 
           331  Processor 
           1000  Notification region in display upper part of wireless station 
           1001  Number of antennas 
           1002  Numerical information 
           1003  Indicator 
           1004  Number of antennas