Wireless communication system

Abstract

This wireless communication system includes a plurality of base stations and a plurality of M2M machines, and sets a plurality of tracking areas. The M2M machines include fixed M2M machines (for example, fixed terminals) that are fixedly installed and driven by batteries. The plurality of base stations are disposed such that the tracking areas include areas in which a plurality of cells and the fixed M2M machines are fixedly installed at positions where wireless communication therebetween is possible. The fixed M2M machines or the base stations include those configured to determine dedicated cells of which communication frequencies are higher than the other cells by learning the communication frequencies through machine learning, and fixate the wireless communication between said dedicated cells and the fixed M2M machines. As a result, the M2M machines fixedly installed at prescribed positions and driven by batteries can suitably suppress shortening of the service lives of the batteries for the M2M machines particularly even when installed in tracking areas in which the base stations are dispersed.

Description

wireless communication system

[0001] The present invention relates to a wireless communication system including a plurality of base stations and a plurality of M2M (Machine to Machine) devices, and in particular to a wireless communication system that enables good communication with a base station when the M2M devices include devices that are fixedly installed in predetermined positions and powered by batteries.

[0002] In a cellular mobile communication system, multiple base stations are deployed within a communication service area, and the communication area of ​​each base station constitutes multiple cells, and these multiple cells form a network within the communication service area. When a user equipment (UE) such as a mobile terminal moves within the communication service area, it selects one cell and communicates with the base station installed in that cell.

[0003] Furthermore, when the UE moves within the communication service area, the UE reselects a new cell suitable for communication. The UE performs a process of detecting a cell that provides good communication quality for the UE, i.e., a cell search, not only during such movement but also at other times such as startup, standby, and discontinuous reception during communication.

[0004] In recent years, attention has been focused not only on communication between people using mobile terminals and the like, but also on M2M (Machine to Machine) communication between devices via wired or wireless communication without human intervention. Like mobile terminals and the like, such M2M devices can be communicatively connected to a cellular mobile communication system. Some M2M devices are mobile within a communication service area, like mobile terminals, while others are fixedly installed at a predetermined location. For ease of explanation, the former will be referred to as "mobile M2M devices" and the latter as "fixed M2M devices."

[0005] An example of an installation situation for fixed M2M devices is installation in a tracking area where base stations are dispersed. In such a situation, the fixed M2M devices are located among dispersed cells. The fixed M2M devices use cell search to detect a cell among the dispersed cells that allows wireless communication with particularly good communication quality, and select or reselect that cell. For ease of explanation, cell selection or cell reselection by a UE including a fixed M2M device will be collectively referred to as a cell selection process.

[0006] An example of such a cell selection process by a fixed M2M device is the wireless communication system disclosed in Patent Literature 1. In this wireless communication system, cells are ranked based on the relationship between accessible coverage levels, any first cell and any second cell are ranked according to this ranking criterion, and whether or not the wireless device should perform a cell change from the first cell to the second cell is evaluated.

[0007] Although Patent Literature 1 primarily exemplifies typical mobile user equipment (UE) as wireless devices, it also exemplifies M2M devices. The M2M devices exemplified in Patent Literature 1 include "mobile M2M equipment" such as those contained in vehicles, as well as "fixed M2M equipment" such as power meters, industrial machinery, or household or personal electrical appliances.

[0008] Special table 2019-535159 publication

[0009] Here, the inventors' investigations have revealed that when a fixed M2M device is powered by an internal battery and the fixed M2M device is installed in a tracking area where base stations are dispersed, the current consumption may increase excessively, resulting in a shortened battery life.

[0010] In a tracking area where base stations are dispersed, fixed M2M devices are installed in locations that enable better wireless communication, as described above. However, when communication conditions such as cell reception sensitivity or traffic change due to the surrounding environment, the fixed M2M devices frequently perform cell search and cell selection processes. In particular, many battery-powered fixed M2M devices operate intermittently to maximize battery life. Therefore, if communication conditions change while the fixed M2M devices are in standby mode, cell search and cell selection processes are likely to occur. This causes the fixed M2M devices to consume unnecessary power, resulting in shorter battery life.

[0011] The present invention has been made to solve such problems, and aims to provide a wireless communication system that can effectively prevent the battery life of M2M devices that are fixedly installed at predetermined locations and powered by batteries from shortening, even when the M2M devices are installed in tracking areas where base stations are dispersed, in particular.

[0012] In order to solve the above-mentioned problems, the wireless communication system according to the present disclosure includes a plurality of base stations in which at least one cell is set, and a plurality of M2M (Machine to Machine) devices capable of wireless communication with the base stations, and also includes a plurality of tracking areas set, the M2M devices including fixed M2M devices that are fixedly installed and powered by batteries, the plurality of base stations being arranged so that the tracking areas include areas where the plurality of cells are fixedly installed in positions where wireless communication between the fixed M2M devices and the fixed M2M devices is possible, and the fixed M2M devices or the base stations are configured to use machine learning to learn the frequency of communication between the plurality of cells and the fixed M2M devices, to determine a dedicated cell that has a higher communication frequency with the fixed M2M device than other cells, and to fix the wireless communication between the dedicated cell and the fixed M2M device.

[0013] According to the above configuration, in a situation where a plurality of base stations are installed dispersedly within a tracking area, a fixed M2M device is configured and registered to be able to communicate only with a specific dedicated cell among a plurality of cells of the base station based on the results of machine learning. As a result, even if communication conditions change, the fixed M2M device will communicate wirelessly only with the dedicated cell of the specific base station, and the fixed M2M device will not have to randomly perform cell search and cell selection processing among a plurality of cells with which it can communicate wirelessly.

[0014] As a result, the fixed M2M device can effectively suppress its current consumption, effectively suppressing shortening of battery life, and also improves synchronous connection with the base station, suppressing a decrease in communication speed. Furthermore, suppressing shortening of battery life makes it easier to adjust the battery life of the fixed M2M device to the design value, and also makes it possible to substantially eliminate the need for battery replacement, thereby enabling product warranty for the fixed M2M device.

[0015] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.

[0016] With the above configuration, the present invention has the effect of providing a wireless communication system that can effectively prevent the battery life of M2M devices that are fixedly installed at predetermined locations and powered by batteries from shortening, even when the M2M devices are installed in tracking areas where base stations are dispersed, in particular.

[0017] FIG. 1 is a schematic diagram showing an example of a configuration of a wireless communication system according to a representative embodiment of the present disclosure. FIG. 2A is a schematic diagram showing a situation in which cell search and cell selection processing occur frequently in a conventional wireless communication system, and FIG. 2B is a schematic current waveform diagram showing the state of current consumption over time of a fixed M2M device in the situation shown in FIG. 2A. FIG. 3A is a schematic diagram showing a situation in which cell search and cell selection processing are suppressed in the wireless communication system shown in FIG. 1, and FIG. 3B is a schematic current waveform diagram showing the state of current consumption over time of a fixed M2M device (fixed terminal) in the situation shown in FIG. 3A. FIG. 4A is a schematic block diagram showing a typical example of a function for suppressing cell search and cell selection processing in a base station included in the wireless communication system shown in FIG. 1, and FIG. 4B is a schematic block diagram showing a typical example of a function for suppressing cell search and cell selection processing in a fixed M2M device (fixed terminal) included in the wireless communication system shown in FIG. 1. FIG. 5 is a flowchart showing an example of the function for suppressing cell search in the base station shown in FIG. 4A. FIG. 6 is a flowchart showing an example of a function for suppressing a cell search in the fixed M2M device (fixed terminal) shown in FIG. 4B.

[0018] [Knowledge, etc., that Forms the Basis of the Present Disclosure] In a wireless communication system, it is desirable for a user equipment (UE) to be able to communicate with a large number of cells, since this allows the UE to maintain a stable communication environment. However, according to the study by the present inventors, it has become clear that, in the case where the UE is a battery-powered fixed M2M device, being able to communicate with a large number of cells may, conversely, induce excessive cell search and cell selection processing, thereby shortening the battery life.

[0019] Therefore, as a result of further intensive research, the inventors independently discovered a configuration in which a specific cell (dedicated cell) is deliberately set among multiple cells and wireless communication is fixed between this dedicated cell and fixed M2M devices. This configuration not only effectively prevents the battery life of fixed M2M devices from shortening, but also ensures a good synchronous connection between the fixed M2M devices and base stations, thereby preventing a decrease in communication speed. Furthermore, this configuration makes it easier to adjust the battery life of fixed M2M devices to the design value and essentially eliminates the need for battery replacement, thereby enabling product warranty for fixed M2M devices. In this way, the inventors have completed the technology disclosed herein.

[0020] Representative embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description will be omitted.

[0021] [Configuration Example of Wireless Communication System] First, a representative example of a wireless communication system according to the present disclosure (a wireless communication system according to the present embodiment) will be specifically described with reference to Fig. 1. As schematically shown in Fig. 1, a wireless communication system 10 according to the present embodiment includes a plurality of base stations 20 and a plurality of fixed terminals 30 serving as M2M (Machine to Machine) devices. A plurality of tracking areas 11 are set in this wireless communication system 10. However, for ease of explanation, only one tracking area 11 is schematically shown by a dashed ellipse in Fig. 1.

[0022] In the schematic example shown in FIG. 1 , three base stations 20 are arranged within one tracking area 11, and each base station 20 has one cell 12 set therein. Note that in FIG. 1 , for the sake of convenience in explaining the main points of the present disclosure, the three base stations 20 are referred to as "base station 20A," "base station 20B," and "base station 20C," respectively, and the cells 12 set in each of the base stations 20A to 20C are referred to as "cell 12A," "cell 12B," and "cell 12C." For example, taking base station 20A as an example, cell 12A is actually a circle centered on base station 20A. However, in FIG. 1 , for the sake of convenience in illustrating one tracking area 11 as a circle, each of the cells 12A to 12C is illustrated as a sector, and the boundary lines between each of the cells 12A to 12C are schematically indicated by thin lines in FIG. 1 .

[0023] It is sufficient that at least one cell 12A is set for one base station 20A, but as will be described later, multiple cells 12A may be set for one base station 20. In particular, the present disclosure can be suitably applied even to a situation where multiple cells 12A are set for one base station 20A. The method of setting multiple cells 12A for one base station 20A is not particularly limited, and a known method can be used.

[0024] Taking LTE (Long Term Evolution, base station OFDM modulation) of 3GPP (registered trademark, Third Generation Partnership Project) as a representative example, the number of cells can be determined based on the occupied bandwidth of the base station. Specifically, for example, base stations correspond to various band frequencies, such as Band 8 (900 MHz band) and Band 1 (2 GHz band). Each base station is set with an occupied bandwidth of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz. Within the occupied bandwidth that can be handled for each base station band, a cell can be determined based on the desired number of resource blocks (RBs) that can be handled. Furthermore, the number of subcarriers (ch: number of users or data volume) can be increased within a resource block. Generally, Band 8 has a long radio wave propagation distance (large cell area) and a small data volume (band frequency: low, occupied bandwidth: small), while Band 1 has a short radio wave propagation distance (small cell area). The amount of data handled is large (band frequency: high, occupied bandwidth: large).

[0025] 1, in addition to the three base stations 20 (base stations 20A to 20C) that will be used to explain the main parts of the present disclosure, another base station 20 is also illustrated schematically outside the tracking area 11. This is intended to indicate that the wireless communication system 10 according to the present disclosure will also include base stations 20 other than the base stations 20A to 20C. Of course, one or more cells 12 are also set in this schematically illustrated base station 20, and this base station 20 is also located in another tracking area 11. The other tracking areas 11 are not illustrated in FIG. 1. As such, it goes without saying that an actual wireless communication system 10 will include a large number of base stations 20, a large number of cells 12 are set, and a large number of tracking areas 11 are set.

[0026] In a wireless communication system 10 according to the present disclosure, a plurality of base stations 20 (base stations 20A to 20C) are distributed. Specifically, by distributing the plurality of base stations 20, as shown in FIG. 1 , it is sufficient that one tracking area 11 includes an area in which a fixed terminal 30 is fixedly installed at a position where it can wirelessly communicate with a plurality of cells 12A to 12C. In the wireless communication system 10 according to the present disclosure, the base stations 20A to 20C do not need to be distributed in all of the plurality of tracking areas 11. For example, the system may include an area in which the plurality of base stations 20 are densely arranged, or may include an area in which the base stations 20 are arranged at a standard density that can be described as neither dense nor dispersed.

[0027] In the present disclosure, the specific conditions for distributing multiple base stations 20 are not particularly limited. A typical example is distributing the base stations 20 based on the cell ID (cell information of the base station 20) recognized by the UE and reception sensitivity. The reception sensitivity can be determined based on the number of accesses by the UE. The more accesses by the UE, the better the reception sensitivity of that cell, resulting in the best selection. The base station 20 can be determined based on the number of accesses between the cell ID of the base station 20 and the terminal information of the UE (fixed terminal 30), such as the ICCID (Integrated Circuit Card ID) and MYSDN (telephone number), as well as good reception sensitivity. Representative reception sensitivity reference indices include (1) -115 dBm or higher (out of range), (2) -115 dBm or lower to -110 dBm (weak field), (3) -110 dBm or lower to -90 dBm (normal), and (4) -90 dBm or lower (strong field). Basically, either (4) or (3) is selected.

[0028] The fixed terminal 30 is an M2M device that is fixedly installed at a desired location and is powered by a battery. There are no particular limitations on its specific configuration, as long as it is capable of transmitting and receiving data to and from other M2M devices via wireless communication. Specific examples of the fixed terminal 30 are not particularly limited, but in the present disclosure, examples include a gas meter or a water meter. Generally, gas meters and water meters are battery-powered and fixedly installed at a desired location. Therefore, if the fixed terminal 30 is a gas meter or a water meter, the wireless communication system 10 according to the present disclosure can be suitably applied.

[0029] In the wireless communication system 10 according to the present disclosure, the M2M devices capable of communicating with the base station 20 (the cell 12 set in the base station 20) are not limited to the fixed terminals 30. Generally, a "terminal (device)" often refers to a device connected to a communication network that is directly used by a user. Gas meters or water meters are generally installed in buildings or facilities that are gas or water users, and therefore, in the present disclosure, such meters are considered to be fixed terminals 30. However, the wireless communication system 10 according to the present disclosure may also be a fixed M2M device that is not a "terminal (device)," such as a meter or measuring device installed in a factory, etc.

[0030] Furthermore, the wireless communication system 10 according to the present disclosure may include "terminals (devices)" other than the fixed terminal 30 or the fixed M2M devices. For example, a mobile terminal (mobile M2M device) such as a mobile phone, smartphone, or tablet may be capable of communicating with the base station 20 (cell 12). Although such a mobile terminal does not fall under the category of M2M devices, the wireless communication system 10 according to the present disclosure may be configured to include wireless communication devices other than M2M devices. Furthermore, such a mobile terminal may be configured to be capable of communicating with the fixed terminal 30 or the fixed M2M devices.

[0031] Furthermore, the wireless communication system 10 according to the present disclosure may include mobile M2M devices in addition to fixed M2M devices or mobile terminals. Examples of such mobile M2M devices include, but are not limited to, M2M devices mounted on automobiles or light vehicles. Note that in this embodiment, for convenience of explanation, wireless communication between a fixed terminal 30 or the like and a base station 20 via a cell 12 may be abbreviated to "communicating between the fixed terminal 30 or the like and the cell 12."

[0032] [Example of communication between fixed M2M device and cell] Next, an example of wireless communication between a cell 12 set in a base station 20 and a fixed terminal 30 which is a fixed M2M device in the wireless communication system 10 according to the present disclosure will be specifically described with reference to Figures 2A, 2B, 3A, and 3B.

[0033] 2A and 3A schematically illustrate a case where multiple cells 12 are set for one base station 20. For example, in FIG. 2A, three cells 12, cells 12A-1 to 12A-3, are set for base station 20A. Each of cells 12A-1 to 12A-3 is illustrated as a circular symbol, arranged in a line. The fact that these cells 12A-1 to 12A-3 are set for one base station 20A is indicated by connecting the line of circular symbols with the symbol representing base station 20A with a thin line. The same applies to base station 20B and its set cells 12B-1 to 12B-3, and base station 20C and its set cells 12C-1 to 12C-3.

[0034] In addition, in Figures 2A and 3A, the symbols indicating base stations 20A to 20C, the symbols indicating cells 12A-1 to 12A-3, 12B-1 to 12B-3, and 12C-1 to 12C-3, and the block arrows CmA, CmB, and CmC that schematically indicate wireless communication described below all include both open and shaded symbols, which schematically indicate differences in the frequencies of wireless communication.

[0035] For example, cells 12A-1 to 12A-3 set in base station 20A are all shown as white, indicating that they use the same frequency. Similarly, cells 12B-1 to 12B-3 set in base station 20B are all shown as shaded, indicating that they use the same frequency. The difference between the white and shaded areas also indicates that cells 12A-1 to 12A-3 and cells 12B-1 to 12B-3 use different frequencies.

[0036] On the other hand, among the cells 12C-1 to 12C-3 set in the base station 20C, only the cell 12C-2 is shown shaded, and the cells 12C-1 and 12C-3 are shown as white. This indicates that a single base station 20C may be set with a mixture of cells 12C-1 to 12C-3 of different frequencies. It goes without saying that, in reality, three or more cells 12A to 12C may be set for each of the base stations 20A to 20C, and three or more types of frequencies may also be set.

[0037] The schematic communication example shown in Fig. 2A corresponds to the communication status between base stations 20A-20C and fixed terminal 30 in tracking area 11 shown schematically in Fig. 1. If fixed terminal 30 is, for example, a gas meter or water meter as described above, it is generally driven intermittently. Fig. 2B is a schematic current waveform diagram corresponding to Fig. 2A and showing the status of current consumption over time of fixed terminal 30.

[0038] 2B shows a signal (paging signal) sent from one of the base stations 20A to 20C to the overlap area terminal 30A, which is a UE, during synchronization (page) via downlink (DL) communication at an arbitrary period. This technique is a power-saving technology called eDRX (extended discontinuous reception), and it is confirmed that the overlap area terminal 30A is not out of range. In FIG. 2B, the arrow on the horizontal axis indicates the passage of time from the left to the right of the figure, and the vertical direction perpendicular to the horizontal axis indicates the magnitude of current consumption.

[0039] In general mobile communications, the UE is in a sleep state except when paging is being performed, and the UE's communications are usually switched to a cell of another base station based on the reception sensitivity of the paging signal. For example, if the reception sensitivity of the UE is not good, a cell search and cell selection process (reselection) is performed, and the UE is switched to a cell of a base station with a different TAC (Tracking Area Code) by handover.

[0040] In the present disclosure, the UE is a fixed terminal 30, and examples of the fixed terminal 30 include a gas meter or a water meter, as described above. For example, in a gas meter, communication occurs between a flow measurement unit that measures the gas flow rate and a wireless communication unit that performs wireless communication, regardless of paging or sleep mode. For convenience of explanation, this is referred to as "internal terminal communication." After the internal terminal communication ends, the fixed terminal 30 pages and synchronizes with the base stations 20A-20C, and then enters a sleep mode. Therefore, the fixed terminal 30 periodically performs such synchronization. Therefore, as shown on the left side of FIG. 2A , when the fixed terminal 30 is performing normal synchronization, elongated pulse-shaped synchronization operation current consumption i1, corresponding to short-term operation, occurs at regular intervals.

[0041] 2A, it is assumed that the fixed terminal 30 is capable of wireless communication with any of the cells 12A-1 to 12C-3 set in the base stations 20A to 20C. However, if the communication conditions change in the tracking area 11, the fixed terminal 30 will perform a cell search to detect a cell 12 with which it can communicate (cells 12A-1 to 12C-3 in the example shown in FIG. 2A), followed by a cell selection process (cell selection or cell reselection).

[0042] For example, as shown by the block arrow CmA in FIG. 2A , assume that the fixed terminal 30 is initially communicating wirelessly with cell 12A-1 of base station 20A. Later, when communication conditions change and the reception sensitivity between the fixed terminal 30 and cell 12A-1 deteriorates, the fixed terminal 30 initiates a cell search to detect cells 12 that use the same frequency and different frequencies. Assume that this cell search detects, for example, cell 12B-2 of base station 20B. This cell 12B-2 uses a different frequency from cell 12A-1. The fixed terminal 30 then performs a cell selection process (cell reselection) to initiate wireless communication with cell 12B-2. When cell 12B-2 is reselected, the fixed terminal 30 initiates wireless communication with cell 12B-2, as shown by the block arrow CmB.

[0043] The current consumption at this time is as shown in Figure 2B, where the current consumption corresponding to the cell search of fixed terminal 30 is the cell search current consumption i2, which is hatched vertically, and the power consumption corresponding to the cell selection process is the cell selection current consumption i3, which is hatched horizontally. It can be seen that the pulse shapes of cell search current consumption i2 and cell selection current consumption i3 are both larger than the pulse shape of synchronous operation current consumption i1, i.e., the current consumption is larger.

[0044] In the example shown in Figure 2B, the current consumption during cell search is greater per unit time than during synchronous operation, and the duration of the cell search is longer than during synchronous operation. Furthermore, the current consumption during cell selection is smaller per unit time than during synchronous operation, but the duration of the cell selection is significantly longer than the duration of the cell search. In other words, the current consumption required for cell search and cell selection is significantly greater than that during flow measurement, which is a synchronous operation.

[0045] If such cell search and cell selection processes occur infrequently, they will not significantly consume the battery charge of the fixed terminal 30. However, as shown in Figure 2A, if the fixed terminal 30 can wirelessly communicate with all of the cells 12A-1 to 12C-3, the cell search and cell selection processes will occur frequently. For example, if the fixed terminal 30 is wirelessly communicating with the cell 12B-2 and the communication conditions change again, causing the wireless communication with the cell 12B-2 to become poor, the cell search and cell selection processes will be executed.

[0046] Even if cell 12C-3 of base station 20C is subsequently reselected and wireless communication is established, as indicated by block arrow CmC, cell search and cell selection processing are executed each time communication conditions change. As a result, the battery charge of fixed terminal 30 is significantly depleted, shortening its battery life. For example, if fixed terminal 30 is a gas meter with a configuration in which the flow measurement unit and wireless communication unit are integrated and share a battery (integrated type), the Measurement Act requires that gas meters be replaced once every 10 years. Therefore, the battery life of gas meters is required to be at least 10 years. However, if cell search and cell selection processing are executed frequently, battery life may be significantly shortened, making it difficult to maintain a 10-year life.

[0047] In the case of a gas meter, when the battery life reaches the end, the gas meter itself is generally replaced rather than the battery being replaced. Therefore, a shortened gas meter battery life leads to a shortened life of the gas meter itself. A shortened gas meter battery life means that the battery life deviates from the design value at the time of designing the gas meter. This means that a shortened battery life can have a significant impact on the product warranty of the gas meter.

[0048] Even if the fixed terminal 30 is a gas meter, the flow rate measurement unit and the wireless communication unit are separate, and the wireless communication unit is configured to be powered by a dedicated battery (separate type), the battery life of the wireless communication unit is required to be at least 10 years, just as with an integrated gas meter. Therefore, even in a separate type fixed terminal 30, just as with an integrated gas meter, a shortened battery life of the wireless communication unit will lead to a shortened life of the gas meter itself, which will have a significant impact on the product warranty of the gas meter.

[0049] In contrast, in the wireless communication system 10 according to the present disclosure, a specific cell 12 among the cells 12A-1 to 12C-3 that can communicate with the fixed terminal 30 is set as a "dedicated cell," and the fixed terminal 30 is fixed so as to communicate wirelessly only with this dedicated cell. In general, in the wireless communication system 10, since the UE is generally a mobile terminal, in this case, it is advantageous to be able to communicate well with various cells 12. However, in a case where the base stations 20 are dispersed and the battery-powered fixed terminal 30 can communicate with many cells 12, as in the present disclosure, the inventors' intensive studies have revealed that it is advantageous to fix the fixed terminal 30 so as to communicate wirelessly only with a specific cell 12.

[0050] As shown by the block arrow CmA in FIG. 3A, for example, the fixed terminal 30 is fixed to communicate only with the cell 12A-1 of the base station 20A among the cells 12A-1 to 12C-3. That is, in this example, the cell 12A-1 is determined as a dedicated cell, and the wireless communication between this dedicated cell and the fixed terminal 30 is fixed. As a result, even if the communication conditions change, the fixed terminal 30 will only communicate wirelessly with the dedicated cell (cell 12A-1 in FIG. 3A) of a specific base station 20 (base station 20A in FIG. 3A). Therefore, the fixed terminal 30 is prevented from randomly performing cell search and cell selection processing for the multiple cells 12A-1 to 12C-3 with which it can communicate wirelessly.

[0051] In this way, if neither a cell search nor a cell selection process occurs, the fixed terminal 30 only generates short, evenly spaced pulses of synchronous operation current consumption i1, as shown in Figure 3B. As a result, the fixed terminal 30 can effectively suppress its current consumption, effectively suppressing shortening of battery life, and also achieves a good synchronous connection with a specific base station 20, thereby suppressing a decrease in communication speed. Furthermore, suppressing a shortening of battery life makes it easier to adjust the battery life of the fixed terminal 30 to the design value, and also makes it possible to substantially eliminate the need for battery replacement, thereby enabling product warranty for the fixed terminal 30.

[0052] In particular, as exemplified in this embodiment, if multiple cells 12 are set for one base station 20, the number of cells 12 with which wireless communication is possible will increase relatively for the fixed terminal 30. In contrast, if the fixed terminal 30 is fixed so as to be able to communicate only with a specific dedicated cell (e.g., cell 12A-1) among the multiple cells 12A-1 to 12C-3, the fixed terminal 30 can effectively avoid randomly performing cell search and cell selection processing even in a situation where the number of cells 12 has increased relatively.

[0053] [Example of Determining and Fixing a Dedicated Cell] Next, an example of determining and fixing a dedicated cell for wireless communication with a fixed terminal 30, which is a fixed M2M device, in the wireless communication system 10 according to the present disclosure will be specifically described with reference to Figures 4A, 4B, 5, and 6.

[0054] In the wireless communication system 10 according to the present disclosure, the dedicated cell may be randomly determined from among the cells 12A-1 to 12C-3 that are capable of wireless communication with the fixed terminal 30. However, in the present disclosure, a configuration may be exemplified in which machine learning is performed on the frequency of communication between the fixed terminal 30 and the cells 12A-1 to 12C-3, and a cell 12 having higher transmission / reception characteristics with the fixed terminal 30 than the other cells 12 is determined as the dedicated cell based on the learning results.

[0055] Here, in the present disclosure, the process of determining and fixing a dedicated cell may be executed by the fixed terminal 30 (fixed M2M device) or may be executed by the base station 20. Fig. 4A is a block diagram showing an example of the functional configuration of the base station 20 in this embodiment, and Fig. 4B is a block diagram showing an example of the functional configuration of the fixed terminal 30 in this embodiment.

[0056] 4A, base station 20 according to this embodiment includes antenna 21, communication unit 22, cell selection unit 23, communication quality determination unit 24, and cell setting unit 25. Fixed terminal 30 according to this embodiment includes antenna 31, communication unit 32, cell selection unit 33, and communication quality determination unit 34.

[0057] In the example of base station 20 shown in Fig. 4A, only one antenna 21 is schematically illustrated, but the present disclosure is not limited to this, and base station 20 may be equipped with multiple antennas 21. Similarly, in the example of fixed terminal 30 shown in Fig. 4B, only one antenna 31 is schematically illustrated, but the present disclosure is not limited to this, and fixed terminal 30 may be equipped with multiple antennas 31. The specific configuration of antenna 21 or antenna 31 is not particularly limited, and a configuration known in the field of wireless communications can be suitably used.

[0058] The specific configurations of the communication unit 22 of the base station 20 and the communication unit 32 of the fixed terminal 30 are not particularly limited, and configurations known in the field of wireless communications can be suitably used. Typically, the communication unit 22 of the base station 20 can be configured to perform Orthogonal Frequency Division Multiple Access (OFDMA) transmission and reception, and the communication unit 32 of the fixed terminal 30 can be configured to perform Single-carrier Frequency Division Multiple Access (SC-FDMA) transmission and reception.

[0059] The cell selection unit 23 of the base station 20 selects a dedicated cell, which is the optimal cell 12, by machine learning based on the frequency of communication between the fixed terminal 30 and the cell 12. The specific configuration of the machine learning is not particularly limited, but a representative example is deep learning. The communication quality determination unit 24 periodically checks the communication quality between the selected dedicated cell and the fixed terminal 30 and determines whether the communication quality is good or poor. The cell setting unit 25 sets and registers the dedicated cell selected by the cell selection unit 23 so as to establish fixed communication.

[0060] The cell selection unit 23, the communication quality determination unit 24, and the cell setting unit 25 may have functional configurations configured by a calculation device and a storage device included in the base station 20. A representative example of the calculation device and storage device included in the base station 20 is a configuration in which they are integrated into a base station server. More specifically, the cell selection unit 23, the communication quality determination unit 24, and the cell setting unit 25 may be configured such that the calculation device included in the base station server is a general-purpose processor, a dedicated processor, an integrated circuit, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), a GPU, or the like, either alone or in combination of two or more types, which operates to realize the functions of the control unit 20 according to a program stored in the storage device.

[0061] Such a processor as an arithmetic device is a hardware circuit (or processing circuit) because it includes a circuit configured with a large number of transistors, memories, etc. Integrated circuits or ASICs are also hardware circuits because they include processors or processing blocks such as CPUs. FPGAs are hardware circuits because they include a large number of integrated logic circuits (functional blocks). GPUs are hardware circuits because they include a large number of arithmetic circuits (cores) mounted in parallel. Software such as programs stored in a storage device is used to configure hardware circuits (processors, integrated circuits, FPGAs, ASICs, GPUs, etc.). Alternatively, the arithmetic device may be configured as a logic circuit or the like using known switching elements, subtractors, comparators, etc.

[0062] Similar to the cell selector 23 of the base station 20, the cell selector 33 of the fixed terminal 30 selects a dedicated cell, which is the optimal cell 12, by machine learning based on the frequency of communication between the fixed terminal 30 and the cell 12. Similar to the communication quality determiner 24 of the base station 20, the communication quality determiner 34 of the fixed terminal 30 periodically checks the communication quality between the selected dedicated cell and the fixed terminal 30 and determines whether the communication quality is good or poor. Similar to the cell selector 23 and communication quality determiner 24 of the base station 20, the cell selector 33 and communication quality determiner 34 of the fixed terminal 30 may also have functional configurations constituted by a calculation device and a storage device provided in the fixed terminal 30. The specific configuration is the same as that of the base station 20, so a detailed description thereof will be omitted.

[0063] In the wireless communication system 10 according to the present disclosure, the configuration for determining a dedicated cell may be provided in either the base station 20 or the fixed terminal 30. Therefore, as shown in Fig. 4A, if the base station 20 is provided with the cell selection unit 23, the communication quality determination unit 24, and the cell setting unit 25, the fixed terminal 30 may be provided with a configuration that does not include the cell selection unit 33 and the communication quality determination unit 34 shown in Fig. 4B.

[0064] However, the setting and registration of the dedicated cell is executed by the base station 20. Therefore, for example, if the fixed terminal 30 is configured to include a cell selector 33 and a communication quality determiner 34 as shown in Fig. 4B, the base station 20 may be configured to include a cell setter 25 but not to include the cell selector 23 and the communication quality determiner 24 shown in Fig. 4A. Note that both the base station 20 and the fixed terminal 30 may be configured to determine a dedicated cell (the configurations shown in Figs. 4A and 4B). In this case, it is sufficient that either the base station 20 or the fixed terminal 30 is configured to determine a dedicated cell during operation.

[0065] A typical example of the case where base station 20 determines a dedicated cell will be described with reference to Figures 4A and 5. First, as shown in Figure 5, fixed terminal 30 is fixedly installed at a suitable position in tracking area 11 and operated (step S01). The installation and operation of this fixed terminal 30 may be performed, for example, by starting construction to install fixed terminal 30, measuring the reception sensitivity of candidate positions, selecting a position with suitable reception sensitivity at that time, installing fixed terminal 30 at that position, conducting a connection test in which the installed fixed terminal 30 wirelessly communicates with any cell 12, and if the connection test results are satisfactory, completing construction and starting operation of fixed terminal 30.

[0066] When the fixed terminal 30 starts operating, the fixed terminal 30 initially performs wireless communication randomly with cells 12 with which it can communicate. At this time, the cell selection unit 23 of the base station 20 acquires and records communication data with the fixed terminal 30 via the antenna 21 and the communication unit 22 (step S02). The communication data includes the cell ID of the cell 12 with which the fixed terminal 30 communicated and the terminal ID of the fixed terminal 30. In the example shown in FIG. 3, the base station 20A acquires and records the terminal ID of the fixed terminal 30 and the cell IDs of the cells 12A-1 to 12C-3 with which the fixed terminal 30 communicated.

[0067] Thereafter, the cell selection unit 23 of the base station 20 selects a cell ID of a dedicated cell that is the optimal cell 12 by machine learning based on the communication frequency with the multiple cells 12 based on the recorded communication data (step S03). In the example shown in Fig. 3, the base station 20A selects the cell ID of the cell 12A-1 of the base station 20A as the optimal cell 12 based on the communication frequency between the cells 12A-1 to 12C-3 and the fixed terminal 30.

[0068] When the cell ID of the dedicated cell is selected, the cell selection unit 23 of the base station 20 outputs the cell ID to the cell setting unit 25, and the cell setting unit 25 fixes and registers communication between the cell ID of the dedicated cell and the terminal ID of the fixed terminal 30 (step S04). In the example shown in Fig. 3, the base station 20A fixes and registers the cell ID of the cell 12A-1 and the terminal ID of the fixed terminal 30.

[0069] Thereafter, the communication quality determination unit 24 of the base station 20 periodically checks the communication quality between the dedicated cell and the fixed terminal 30 (step S05). If the communication quality is determined to be "good," the communication quality is repeatedly checked periodically thereafter (return to step S05). However, if the communication quality is determined to be "poor," the cell selection unit 23 starts acquiring and recording communication data with the fixed terminal 30 in order to determine a new dedicated cell (return to step S02).

[0070] In this way, the base station 20 periodically determines the communication quality between the dedicated cell and the fixed terminal 30, so that the fixed terminal 30 can periodically determine whether or not a deterioration in communication quality due to a change in communication conditions is occurring. This effectively reduces the possibility that the base station 20 will perform too little or too much dedicated cell redetermining processing.

[0071] The specific method for checking the communication quality between the fixed terminal 30 and the dedicated cell is not particularly limited, and various known methods can be applied. A representative example is a method in which the transmission and reception characteristics between the fixed terminal 30 and the dedicated cell are compared with a reference value. The communication quality determination unit 24 compares the transmission and reception characteristics with the reference value, and if the transmission and reception characteristics are equal to or greater than the reference value, it is determined that the communication quality is maintained ("good quality" in step S05). If the transmission and reception characteristics are below the reference value, it is determined that the communication quality has deteriorated ("poor quality" in step S05), as described above. If it is determined that the communication quality has deteriorated, a new dedicated cell can be re-determined by machine learning the communication frequency between the multiple cells 12 and the fixed terminal 30, as described above (steps S02 to S04).

[0072] In this way, when communication conditions such as reception sensitivity or traffic change due to the surrounding environment and the communication quality of the dedicated cell with which communication has been taking place deteriorates, the base station 20 re-selects a new dedicated cell from among the multiple cells 12 based on the results of machine learning. This effectively avoids the risk of communication quality deterioration due to changes in communication conditions, and also avoids randomly executing cell search and cell selection processes to re-select a new dedicated cell, thereby effectively suppressing shortening of battery life.

[0073] The transmission and reception characteristics used to check communication quality are not particularly limited, and various known communication indices can be used, but a representative example is the field strength measured at the installation location of the fixed terminal 30. Other transmission and reception characteristics include the data transmission speed (particularly the downlink transmission speed) and reception sensitivity. As the transmission and reception characteristics, only the field strength may be used, or the field strength may be used in combination with one or more other communication indices. Therefore, it is sufficient that the transmission and reception characteristics include at least the field strength measured at the installation location of the fixed terminal 30.

[0074] Next, a typical example of the case where the fixed terminal 30 determines a dedicated cell will be described with reference to Fig. 4B and Fig. 6. First, as shown in Fig. 6, the fixed terminal 30 is fixedly installed and operated in a suitable position in the tracking area 11 (step S11). This step S11 is the same as step S01 in the determination of a dedicated cell by the base station 20 (see Fig. 5).

[0075] When the fixed terminal 30 starts operating, the fixed terminal 30 initially performs wireless communication randomly with the cells 12 with which it can communicate. At this time, the cell selection unit 33 of the fixed terminal 30 acquires and records communication data with the base station 20 via the antenna 31 and the communication unit 32 (step S12). The communication data includes the cell ID of the cell 12 with which the fixed terminal 30 communicates and the ID (base station ID) of the base station 20 in which the cell 12 is set. In the example shown in FIG. 3, the fixed terminal 30 acquires and records the base station IDs of the base stations 20A to 20C and the cell IDs of the cells 12A-1 to 12C-3 set in these base stations 20A to 20C.

[0076] Thereafter, the cell selection unit 33 of the fixed terminal 30 selects a cell ID of a dedicated cell that is the optimal cell 12 by machine learning based on the frequency of communication with the multiple cells 12 based on the recorded communication data (step S13). In the example shown in Fig. 3, the fixed terminal 30 selects the cell ID of the cell 12A-1 of the base station 20A as the optimal cell 12 based on the frequency of communication with the cells 12A-1 to 12C-3.

[0077] When the cell ID of the dedicated cell is selected, the cell selection unit 33 of the fixed terminal 30 transmits a command to the base station 20A to fix and register communication with the cell ID of the dedicated cell (step S14). When the base station 20A receives the command from the fixed terminal 30, the cell ID of the dedicated cell is output to the cell setting unit 25, and communication between the cell ID of the dedicated cell and the terminal ID of the fixed terminal 30 is fixed and registered. In the example shown in FIG. 3, in response to the command from the fixed terminal 30, the base station 20A fixes and registers the cell ID of cell 12A-1 and the terminal ID of the fixed terminal 30.

[0078] Thereafter, the communication quality determination unit 34 of the fixed terminal 30 periodically checks the communication quality between the dedicated cell and the fixed terminal 30 (step S15). If the communication quality is determined to be "good," the communication quality is repeatedly checked periodically thereafter (return to step S15). However, if the communication quality is determined to be "poor," the cell selection unit 33 starts acquiring and recording communication data with the fixed terminal 30 in order to determine a new dedicated cell (return to step S12).

[0079] In this way, the fixed terminal 30 periodically determines the communication quality with the dedicated cell, thereby making it possible to periodically determine whether a deterioration in communication quality has occurred due to a change in communication conditions. This effectively reduces the possibility that the fixed terminal 30 will perform too few or too many dedicated cell redetermining processes. Note that the specific method for checking communication quality in the fixed terminal 30 is the same as that in the base station 20 described above.

[0080] Furthermore, when the fixed terminal 30 determines the dedicated cell by machine learning, it is sufficient that a command is transmitted from the fixed terminal 30 to the base station 20 to fix and register communication with the dedicated cell. As a result, fixed communication with the dedicated cell is set and registered by the base station 20, so the fixed terminal 30 does not need to be provided with a configuration for setting and registering fixed communication. As a result, the fixed terminal 30 does not consume power for setting and registering fixed communication, and therefore it is possible to effectively avoid further shortening of battery life.

[0081] (Additional Notes) Based on the description of the above embodiments, the present specification discloses the following technologies: (Technology 1) A wireless communication system including a plurality of base stations in which at least one cell is set, and a plurality of M2M (Machine to Machine) devices capable of wireless communication with the base stations, and in which a plurality of tracking areas are set, the M2M devices include fixed M2M devices that are installed in a fixed position and powered by batteries, the plurality of base stations are arranged such that the tracking areas include areas where the plurality of cells are installed in fixed positions where wireless communication between the plurality of cells and the fixed M2M devices is possible, and the fixed M2M devices or the base stations are configured to perform machine learning on the frequency of communication between the plurality of cells and the fixed M2M devices, to determine a dedicated cell that has a higher communication frequency with the fixed M2M device than other cells, and to fix wireless communication between the dedicated cell and the fixed M2M device.

[0082] According to the above configuration, in a situation where a plurality of base stations are installed dispersedly within a tracking area, a fixed M2M device is configured and registered to be able to communicate only with a specific dedicated cell among a plurality of cells of the base station based on the results of machine learning. As a result, even if communication conditions change, the fixed M2M device will communicate wirelessly only with the dedicated cell of the specific base station, and the fixed M2M device will not have to randomly perform cell search and cell selection processing among a plurality of cells with which it can communicate wirelessly.

[0083] As a result, the fixed M2M device can effectively suppress its current consumption, effectively suppressing shortening of battery life, and also improves synchronous connection with the base station, suppressing a decrease in communication speed. Furthermore, suppressing shortening of battery life makes it easier to adjust the battery life of the fixed M2M device to the design value, and also makes it possible to substantially eliminate the need for battery replacement, thereby enabling product warranty for the fixed M2M device.

[0084] (Technology 2) The wireless communication system described in Technology 1, wherein the fixed M2M device or the base station compares the transmission and reception characteristics between the dedicated cell and the fixed M2M device with a reference value, and if the transmission and reception characteristics are below the reference value, determines that communication quality has deteriorated, and redetermines a new dedicated cell by machine learning the communication frequency between the multiple cells and the fixed M2M device within the learning period.

[0085] According to the above configuration, when communication conditions such as cell reception sensitivity or traffic change due to the surrounding environment and the communication quality of the dedicated cell with which communication was previously being performed deteriorates, a new dedicated cell is re-selected from among multiple cells based on the results of machine learning. This effectively avoids the risk of communication quality deterioration due to changes in communication conditions, and also avoids randomly executing cell search and cell selection processes to re-select a new dedicated cell, thereby effectively suppressing shortening of battery life.

[0086] (Technology 3) The wireless communication system according to Technology 2, wherein the evaluation of communication quality between the dedicated cell and the fixed M2M device is performed periodically.

[0087] According to the above configuration, by periodically evaluating the communication quality of the dedicated cell, it is possible to periodically determine whether or not a deterioration in communication quality has occurred due to a change in communication conditions, thereby effectively reducing the possibility that the fixed M2M device or the base station will perform too little or too much dedicated cell redetermining processing.

[0088] (Technology 4) The wireless communication system according to Technology 2 or Technology 3, wherein the transmission and reception characteristics include at least an electric field strength measured at an installation position of the fixed M2M device.

[0089] According to the above configuration, by measuring at least the electric field strength at the installation location of the fixed M2M device and evaluating this as the transmission / reception characteristics between the fixed M2M device and the cell, the fixed M2M device or the base station can more preferably determine a dedicated cell with better transmission / reception characteristics.

[0090] (Technology 5) The wireless communication system according to any one of Technology 1 to Technology 4, wherein a plurality of the cells are set in the base station.

[0091] According to the above configuration, since multiple cells are configured in one base station, the number of cells with which a fixed M2M device can communicate wirelessly increases relatively. In response to this, the fixed M2M device or the base station configures and registers the fixed M2M device so that it can communicate only with specific dedicated cells among the multiple cells based on the results of machine learning. Therefore, even in a situation where the number of cells is relatively increased, the fixed M2M device can effectively avoid randomly performing cell search and cell selection processes. This effectively prevents shortening of battery life, improves synchronous connection with the base station, and prevents a decrease in communication speed.

[0092] (Technology 6) A wireless communication system according to any one of Technology 1 to Technology 5, wherein, when the fixed M2M device determines the dedicated cell by machine learning, the fixed M2M device sends a command to the base station to fix and register communication with the dedicated cell.

[0093] According to the above configuration, since the fixed communication with the dedicated cell is set and registered by the base station, the fixed M2M device does not need to have a configuration for setting and registering the fixed communication. As a result, the fixed M2M device does not consume power for setting and registering the fixed communication, and therefore, it is possible to effectively avoid further shortening of the battery life.

[0094] (Technology 7) The wireless communication system according to any one of Technology 1 to Technology 6, wherein the tracking area includes areas in which the base stations are densely arranged.

[0095] (Technology 8) The wireless communication system according to any one of Technology 1 to Technology 7, wherein the fixed M2M device is a gas meter or a water meter.

[0096] According to the above configuration, since the fixed M2M device is a gas meter or a water meter, these meters that are battery-powered and fixedly installed can be suitably applied to a wireless communication system.

[0097] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Therefore, embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modifications are also included in the technical scope of the present invention.

[0098] Furthermore, many modifications and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention.

[0099] The present invention can be widely and suitably used in wireless communication fields including multiple base stations and multiple M2M devices, particularly in wireless communication fields where the M2M devices include fixed M2M devices that are fixedly installed in predetermined locations and powered by batteries.

[0100] 10: Wireless communication system 11: Tracking area 12A to 12C: Cell 12A-1 to 12A-3: Cell 12B-1 to 12B-3: Cell 12C-1 to 12C-3: Cell 20: Base station 20A to 20C: Base station 21: Antenna 22: Communication unit 23: Cell selection unit 24: Communication quality determination unit 25: Cell setting unit 30: Fixed terminal (fixed M2M device) 31: Antenna 32: Communication unit 33: Cell selection unit 34: Communication quality determination unit i1: Synchronization operation current consumption i2: Cell search current consumption i3: Cell selection current consumption

Claims

1. A wireless communication system comprising: a plurality of base stations in which at least one cell is set; and a plurality of M2M (Machine to Machine) devices capable of wireless communication with the base stations; and a plurality of tracking areas are set; the M2M devices include fixed M2M devices that are installed in a fixed position and powered by batteries; the plurality of base stations are arranged so that the tracking areas include areas where the plurality of cells are installed in fixed positions where wireless communication between the plurality of cells and the fixed M2M devices is possible; and the fixed M2M devices or the base stations include a device configured to determine a dedicated cell that has a higher communication frequency with the fixed M2M device than other cells by machine learning the communication frequency between the plurality of cells and the fixed M2M device, and to fix the wireless communication between the dedicated cell and the fixed M2M device.

2. The wireless communication system of claim 1, wherein the fixed M2M device or the base station compares the transmission and reception characteristics between the dedicated cell and the fixed M2M device with reference values, and if the transmission and reception characteristics are below the reference values, determines that communication quality has deteriorated, and redetermines a new dedicated cell by machine learning the frequency of communication between the multiple cells and the fixed M2M device within the learning period.

3. The wireless communication system according to claim 2, wherein the evaluation of communication quality between the dedicated cell and the fixed M2M device is performed periodically.

4. The wireless communication system according to claim 2, wherein the transmission and reception characteristics include at least a field strength measured at an installation position of the fixed M2M device.

5. The wireless communication system according to claim 1, wherein a plurality of said cells are set in said base station.

6. The wireless communication system according to claim 1, wherein, when the fixed M2M device determines the dedicated cell by machine learning, the fixed M2M device sends a command to the base station to fix and register communication with the dedicated cell.

7. The wireless communication system according to claim 1, wherein the tracking area includes areas in which the base stations are distributed.

8. The wireless communication system according to any one of claims 1 to 7, wherein the fixed M2M device is a gas meter or a water meter.

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