JP7038878B2 - Wireless device, antenna selection method and program - Google Patents

Description

The present disclosure relates to wireless devices, antenna selection methods and programs.

Generally, a preamble consisting of a specific bit string is added to the head of a data unit (packet) exchanged by wireless communication. In recent years, the preamble length (preamble length) of a data unit has become shorter due to the demand for higher speed and power saving of wireless communication. For example, the preamble length used to be about 16 octets, but in recent years it has become less than 4 octets.

On the other hand, diversity technology for improving the reliability, stability, etc. of wireless communication by using a plurality of antennas is known. One method of diversity technology is so-called switchable diversity (for example, Patent Documents 1 and 2).

In switchable diversity, generally, while receiving a radio signal corresponding to a preamble of a data unit, a plurality of antennas are switched and the received signal strength (RSSI: Received Signal Strength Indicator) of each antenna is evaluated. Then, based on the evaluation, the optimum antenna for receiving the radio signal after the preamble is selected.

Japanese Patent Application Laid-Open No. 2003-309501 Japanese Unexamined Patent Publication No. 2005-341079

As the data unit becomes shorter in preamble in the switchable diversity, it becomes difficult to evaluate the RSSI of each antenna while receiving the radio signal corresponding to the preamble. If the RSSI of each antenna cannot be evaluated, the optimum antenna used for wireless communication cannot be selected, and good wireless communication may not be possible.

The present disclosure has been made in view of the above problems, and its main purpose is to perform good wireless communication even when the preamble length of the data unit is short in a wireless device equipped with a plurality of antennas and adopting switchable diversity. To do.

The wireless device according to one embodiment of the present disclosure for achieving the above object is
It is a wireless device that constitutes a network conforming to the communication standard of IEEE802.1.5 together with a plurality of external devices.
With multiple antennas
Signal processing means for processing radio signals and
An antenna switching means for connecting any of the plurality of antennas to the signal processing means,
A storage means for storing a data group relating to a signal strength of a radio wave signal received by each of the plurality of antennas, and a storage means.
Before starting communication with each of the plurality of external devices via the data unit including the preamble, a data group relating to the signal strength of the radio wave signal received by each of the plurality of antennas is stored in the storage means in advance, and the storage means is described. One antenna is selected from the plurality of antennas based on the data group stored in advance in the storage means, and the selected antenna is connected to the signal processing means by controlling the antenna switching means. Control means and
Equipped with
The data group includes first table data which is information on signal strength of radio wave signals from each of the plurality of external devices received by each of the plurality of antennas.
When transmitting a radio wave signal to the external device, the control means selects a first antenna, which is one of the plurality of antennas, based on the first table data .

According to the wireless device having the above configuration, good wireless communication can be performed even when the preamble length of the data unit is short.

It is a schematic diagram which shows the communication network system schematically. It is a block diagram which shows the structure of a wireless device. It is a table explaining the table data. (A) is the transmission table data, and (B) is the reception table data. It is a flowchart which shows the transmission process. It is a flowchart which shows a part of the modification of a transmission process. It is a flowchart which shows a part of the modification of a transmission process. It is a flowchart which shows the reception process in a table data creation mode. It is a flowchart which shows the modification of the reception processing in a table data creation mode. It is a flowchart which shows the reception process in a table data update mode. It is a flowchart which shows the 1st modification of the reception process in a table data update mode. It is a flowchart which shows the 2nd modification of the reception processing in a table data update mode. It is a flowchart which shows the antenna switching process. It is a flowchart which shows the modification of the reception process.

Hereinafter, the wireless device according to the embodiment will be described with reference to the drawings. The wireless device according to the embodiment constitutes a part of a communication network system.

[System configuration]
As shown in FIG. 1, the communication network system 1 according to the embodiment includes a plurality of wireless devices 2 to 4. In the present embodiment, the communication network system 1 includes, for example, three wireless devices 2 to 4.

The wireless devices 2 to 4 constitute a mesh-type, star-type, or tree-type network system that transmits and receives radio signals to and from each other. The wireless devices 2 to 4 mutually perform wireless communication in accordance with a wireless communication standard called, for example, IEEE802.1.5. The radio wave signal is, for example, a high frequency signal in the 920 MHz band. The preamble of the data unit included in the radio signal is, for example, 4 octets.

A measuring device 2a is connected to the wireless device 2. The measuring device 2a measures, for example, the amount of gas (volume) consumed by a gas appliance such as a water heater or a heater. The measuring device 2a may be a device for measuring the amount of electricity (power consumption) consumed by the electric device, or may be a device for measuring the amount of clean water, sewage, etc. used. .. The wireless device 2 and the measuring device 2a may be integrally configured.

The wireless device 2 periodically transmits the information measured by the measuring device 2a (measurement information of the measuring device 2a) to the wireless device 4 by wireless communication. The measurement information may be transmitted to the wireless device 4 via the wireless device 3 or may be directly transmitted to the wireless device 4.

Similarly, the measuring device 3a is connected to the wireless device 3. The measuring device 3a measures, for example, the amount of gas consumed by the gas appliance. The wireless device 3 periodically transmits the information measured by the measuring device 3a (measurement information of the measuring device 3a) to the wireless device 4 via the wireless device 2 or directly to the wireless device 4. do. The wireless device 3 and the measuring device 3a may be integrally configured.

The wireless device 4 transfers the measurement information received by the wireless device 4 to the aggregation device 5 through the network. The aggregation device 5 aggregates the measurement information acquired via the network. The tabulation device 5 is, for example, a general computer.

The communication network system 1 has been described above. Hereinafter, the details of the wireless devices 2 to 4 constituting the communication network system 1 will be described. For ease of understanding, the wireless devices 2 to 4 all have the same hardware configuration and functional configuration. However, the wireless devices 2 to 4 may have different hardware configurations and functional configurations. Hereinafter, the hardware configuration and the functional configuration of the wireless device 2 will be described as an example.

[Wireless device configuration]
As shown in FIG. 2, the wireless device 2 mainly includes a plurality of antennas 21a, 21b, 21c and an antenna (AN) switch element (antenna switching means) 22 for switching the connection of the plurality of antennas 21a, 21b, 21c. , A communication controller (signal processing means) 23 that processes radio waves, a CPU (Central Processing Unit) 24 that performs various arithmetic processing and comprehensively controls the overall operation of the wireless device 2, and a memory (storage means) that stores various information. ) 25 and an I / F (interface) controller (connecting means) 26 for controlling the connection with the measuring device 2a. The CPU 24 and the memory 25, the CPU 24, the I / F (interface) controller 26, or all of them may constitute one microcomputer chip.

In the present embodiment, an example in which the wireless device 2 includes three antennas 21a, 21b, and 21c will be described, but the number of antennas may be two or four or more. The AN switch 22 connects any of the three antennas 21a, 21b, 21c to the communication controller 23 based on the control signal from the CPU 24.

The three antennas 21a, 21b, and 21c may be collectively referred to as an antenna 21. Further, the antenna 21a may be referred to as a first antenna (first antenna), the antenna 21b may be referred to as a second antenna (second antenna), and the antenna 21c may be referred to as a third antenna (third antenna).

The communication controller 23 mainly includes a transmission / reception switching unit 231 that switches between transmission and reception of radio wave signals, a modulation unit 232 that modulates the baseband signal transmitted from the CPU 24, and a demodulation unit 233 that demodulates the input radio wave signal. Includes a measuring unit 234 that measures the signal strength of the input radio signal. The communication controller 23 may also include an arithmetic processing unit (processor), a storage unit (memory), and the like.

The transmission / reception switching unit 231 includes, for example, a high frequency switch circuit. The transmission / reception switching unit 231 passes the radio wave signal transmitted from the modulation unit 232 to the AN switch 22 or the radio wave signal transmitted from the AN switch 22 to the demodulation unit 233 based on the control signal from the CPU 24.

The modulation unit 232 includes a modulation circuit and superimposes a baseband signal transmitted from the CPU 24 on the carrier wave. The demodulation unit 233 includes a demodulation circuit, removes a carrier wave component from the input radio wave signal, and extracts a baseband signal. The measurement unit 234 includes, for example, a voltage rectifier circuit, measures and quantifies (quantifies) the magnitude of the amplitude of the input radio wave signal. The magnitude of the amplitude of the quantified radio wave signal is read out to the CPU 24 (calculation means 24c) as RSSI (received signal strength).

The CPU 24 reads out various programs stored in the memory 25, performs arithmetic processing for realizing various functions, control processing for various hardware units, and the like. For example, the CPU 24 performs various operations and controls for transmitting the measurement information acquired from the measuring device 2a to the external devices (wireless devices 3 and 4) by wireless communication according to the program 252 stored in the memory 25. .. The CPU 24 supports multi-thread processing, and can execute a plurality of processes in parallel.

The memory 25 includes a volatile memory such as a DRAM (Dynamic Random Access Memory) or a non-volatile memory such as a flash memory. In the memory 25, for example, a data group 251 which is information related to the signal strength of the radio wave signal received by each of the antennas 21, a program 252 related to various calculations and controls enabling wireless communication with an external device, and the like are stored. To.

The I / F controller 26 is, for example, a serial controller such as RS-232C or a USB (Universal Serial Bus) controller, and communicates with the measuring device 2a in accordance with a standardized communication standard. The I / F controller 26 may be a wireless communication controller, and may wirelessly communicate with the measuring device 2a, for example, in accordance with a short-range wireless communication standard called Bluetooth (registered trademark).

Subsequently, the functional configuration of the CPU 24 of the wireless device 2 will be described. The CPU 24 mainly receives radio waves received by each of the transmitting means 24a that unitizes (packets) the information transmitted to the external device, the receiving means 24b that reads and analyzes the information (data unit) received from the external device, and the antenna 21. It functions as a calculation means 24c that generates information related to the signal strength of the signal, a control means 24d that selects an antenna 21 to be connected to the communication controller 23 based on the data group 251 and a timekeeping means 24e that measures the time and time. ..

The CPU 24, which functions as the transmission means 24a, generates, for example, a data unit (DU) including the measurement information of the measurement device 2a acquired via the I / F controller 26. The data unit contains, for example, ID information indicating that the transmission source is the wireless device 2. The CPU 24 as the transmission means 24a outputs the generated data unit as a baseband signal.

The CPU 24 functioning as the receiving means 24b reads the input baseband signal as a data unit representing the status of the wireless devices 3 and 4, the request to the wireless device 2, and the like. The CPU 24 as the receiving means 24b performs various operations and controls based on their status, requests, and the like. Further, the received data unit is analyzed to determine whether the transmission source of the data unit is the wireless devices 3 and 4.

The CPU 24, which functions as the arithmetic means 24c, acquires the RSSI of the radio wave signal received by each of the antennas 21 from the measuring unit 234, and acquires the information indicating the source of the received radio wave signal from the receiving means 24b. Then, the CPU 24 as the calculation means 24c calculates the average signal strength value of the radio wave signal from each of the wireless devices 3 and 4 received by each of the antennas 21.

As shown in FIG. 3A, the CPU 24 as the calculation means 24c calculates the average RSSI of the radio wave signal from the radio device 3 received by the antenna 21a as the average signal strength value TD11. Similarly, the average RSSI of the radio wave signal from the radio wave device 4 received by the antenna 21a is set as the average signal strength value TD21, and the average RSSI of the radio wave signal from the radio wave device 3 received by the antenna 21b is set as the average signal strength value. As TD12, the average RSSI of the radio wave signal from the radio wave device 4 received by the antenna 21b is the average signal strength value TD22, and the average RSSI of the radio wave signal from the radio wave device 3 received by the antenna 21c is the average signal strength value. As TD13, the average RSSI of the radio wave signal from the radio wave device 4 received by the antenna 21c is calculated as the average signal strength value TD23. Further, the calculation means 24c stores the calculated average signal strength values TD11 to TD23 in the memory 25 as the first table data (transmission TD) 251a. The first table data 251a constitutes a part of the data group 251 stored in the memory 25.

For ease of understanding, in the following description, it is assumed that the average signal strength values TD11 to TD13 have a magnitude relationship that TD11 is smaller than TD12 and TD12 is smaller than TD13 (TD11 <TD12 <TD13). Further, the average signal strength values TD21 to TD23 have a magnitude relationship that TD21 is larger than TD22 and TD22 is larger than TD23 (TD21> TD22> TD23).

The antenna 21 having a high RSSI of the received radio wave signal on average, that is, having a high average signal strength value, means that the wireless communication environment is good. When communicating with an external device, it is usually preferable to use an antenna having a higher average signal strength value. Here, when communicating with the wireless device 3, it is preferable to use the antenna 21c having the maximum average signal strength value TD13 among the average signal strength values TD11 to TD13. Further, when communicating with the wireless device 4, it is preferable to use the antenna 21a having the maximum average signal strength value TD21 among the average signal strength values TD21 to TD23.

As shown in FIG. 3B, the CPU 24 as the arithmetic means 24c may create the second table data (reception TD) 251b different from the first table data 251a and store it in the memory 25. The average signal strength value TD31 constituting the second table data 251b is an average value of the total signal strength of the radio wave signal received by the antenna 21a, and is calculated as (TD11 + TD21) / 2, for example. Similarly, the average signal strength value TD32 is calculated as, for example, (TD12 + TD22) / 2, and the average signal strength value TD33 is calculated as, for example, (TD13 + TD23) / 2. The second table data 251b constitutes a part of the data group 251 stored in the memory 25.

Such second table data 251b may be created and used when selecting the antenna 21. In order to facilitate understanding, in the following description, the average signal strength values TD31 to TD33 have a magnitude relationship that the TD31 is smaller than the TD32 and the TD32 is smaller than the TD33 (TD31 <TD32 <TD33). do.

The explanation will be continued by returning to FIG.

The CPU 24 functioning as the control means 24d selects an antenna 21 to be used for communication based on the data group 251 stored in the memory 25, controls the AN switch 22, and connects any of the antennas 21 to the communication controller 23. do. For example, when transmitting a radio wave signal to the wireless device 3, the antenna 21c having the maximum average signal strength value TD13 among the average signal strength values TD11 to TD13 is connected to the communication controller 23. Further, when transmitting a radio wave signal to the wireless device 4, the antenna 21a having the maximum average signal strength value TD21 among the average signal strength values TD21 to TD23 is connected to the communication controller 23.

The CPU 24, which functions as the time measuring means 24e, measures the time and time. The time measuring means 24e measures the time elapsed since the calculation means 24c calculates the data group 251 and notifies the calculation means 24c when, for example, 2 hours have elapsed (at the time of reset timing described later). Upon receiving the notification, the arithmetic means 24c regenerates the data group 251 and rewrites the data group 251 stored in the memory 25 to the new data group 251.

The CPU 24 has the above functions. It should be noted that these functions may be realized by, for example, a processor included in the communication controller 23.

Next, the process related to the wireless communication of the wireless device 2 will be described. The wireless device 2 mainly executes transmission processing and reception processing. Further, it is assumed that the reception process includes a table data creation mode and a table data update mode. Hereinafter, the transmission process, the reception process in the table data creation mode, and the reception process in the table data update mode of the wireless device 2 will be described in order.

The table data creation mode is a mode in which RSSIs of radio wave signals received from each of the wireless devices 3 and 4 received by each of the antennas 21 are positively collected to create the first table data 251a and the second table data 251b. By executing this mode, it is possible to more efficiently grasp the antenna 21 having a good wireless communication environment. Further, the table data update mode is a mode for updating the first table data 251a and the second table data 251b based on RSSI acquired in normal wireless communication, and by this mode, the first table data 251a And even if the wireless communication environment changes after the second table data 251b is created, the evaluation of the wireless communication environment can be modified.

[Wireless device transmission processing]
FIG. 4 shows a flowchart of the transmission process executed by the CPU 24 of the wireless device 2. Hereinafter, the transmission process executed by the CPU 24 will be described with reference to the flowchart. The CPU 24 starts this process, for example, when transmitting the measurement information of the measuring device 2a to the wireless devices 3 and 4, when transferring the received radio wave signal to the wireless devices 3 and 4, and the like.

In the antenna selection / connection step S101, the CPU 24 selects the antenna 21 to be used for communication with reference to the first table data 251a of the data group 251. Then, the CPU 24 connects the selected antenna 21 to the communication controller 23 by controlling the AN switch 22.

Specifically, when transmitting a radio wave signal to the wireless device 3, the CPU 24 selects an antenna 21c having the maximum average signal strength value TD13 among the average signal strength values TD11 to TD13, and uses the antenna 21c as the communication controller 23. Connect to. Further, when transmitting a radio wave signal to the wireless device 4, the CPU 24 selects an antenna 21a having the maximum average signal strength value TD21 among the average signal strength values TD21 to TD23, and connects the antenna 21a to the communication controller 23. ..

It is assumed that the first table data 251a is created in advance by the reception process in the table data creation mode described later. However, if the first table data 251a has not yet been created in step S101, a predetermined antenna 21 or a randomly determined antenna 21 may be connected to the communication controller 23.

In the signal transmission step S102, the CPU 24 electrically connects the AN switch 22 and the modulation unit 232 by controlling the transmission / reception switching unit 231. Then, the CPU 24 outputs the baseband signal corresponding to the data unit to the modulation unit 232. The baseband signal is converted into a modulated wave (radio wave signal) in the modulation unit 232. The modulated wave is transmitted via the antenna 21c when transmitted to the wireless device 3 and via the antenna 21a when transmitted to the wireless device 4.

As a result, the CPU 24 ends this process. The CPU 24 selects the antenna 21 to be used for communication based on the data group 251 stored in advance. Therefore, even if the preamble length of the data unit exchanged by wireless communication is short, the situation that the optimum antenna 21 cannot be selected does not occur, and the wireless device 2 can perform wireless communication satisfactorily.

[Transformation example of transmission processing]
The wireless communication environment can always change due to external factors. Therefore, even if a radio wave signal is transmitted / received using an antenna having the maximum average signal strength value, good wireless communication may not be possible. Hereinafter, as a modification of the transmission process, the process when the transmission of the radio wave signal fails will be described.

5 and 6 show a flowchart according to a modified example of the transmission process. Hereinafter, a modified example of the transmission process executed by the CPU 24 will be described with reference to the flowchart.

In step S111, the CPU 24 defines the variables n, m, and L, and assigns '0' to the variables n, m, and L, respectively. In step S112, the CPU 24 refers to the first table data 251a, selects an antenna 21 to be used for communication, and controls the AN switch 22 to connect the selected antenna 21 to the communication controller 23.

In step S113, the CPU 24 transmits a radio wave signal via the antenna 21 connected to the communication controller 23. Note that steps S112 and S113 of the flowchart according to this modification are the same steps as steps S101 and S102 of the flowchart according to the embodiment (FIG. 4).

In the transmission success confirmation step S114, the CPU 24 determines whether or not the ACK (ACKnowledgement) signal transmitted from the external device to which the radio wave signal is transmitted has been received to notify that the radio wave signal has been received. Specifically, when it is determined that the ACK signal has been received (S114; Yes), the CPU 24 determines that the transmission has been successful and ends this process. If it is determined that the ACK signal has not been received (S114; No), the CPU 24 determines that the radio wave signal should be retransmitted, proceeds to step S115, and counts the total number of signal transmissions m.

In step S115, the CPU 24 increments the variable m and determines whether or not the variable m is equal to a preset constant c1 (upper limit of the number of signal transmissions, for example, '20'). Specifically, when the CPU 24 determines that the variable m is equal to the constant c1 (S115; Yes), it determines that the signal transmission has failed, and terminates this process. If the CPU 24 determines that the variable m is smaller than the constant c1 (S115; No), the CPU 24 proceeds to step S116 and counts the number of signal transmissions n by the antenna 21 connected to the communication controller 23.

In step S116, the CPU 24 increments the variable n and determines whether the variable n is equal to a preset constant c2 (upper limit of the number of retransmissions in the same antenna 21, for example, '3'). do. Specifically, when the CPU 24 determines that the variable n is smaller than the constant c2 (S116; No), the CPU 24 returns to step S113 and retransmits the radio wave signal. Further, when the CPU 24 determines that the variable n is equal to the constant c2 (S116; Yes), the CPU 24 proceeds to step S117.

In step S117, the CPU 24 determines whether the variable L is equal to the constant Na ('3' in this embodiment) -1, which is equal to the number of antennas 21. Specifically, the CPU 24 proceeds to step S120 when the variable L is equal to the constant (Na-1) (S117; Yes). Further, when the variable L is smaller than the constant (Na-1) (S117; No), the CPU 24 proceeds to step S118.

In step S118, the CPU 24 masks the antenna 21 connected to the communication controller 23 at that time. The mask processing means an operation of preventing the antenna 21 to be masked from being selected when the antenna 21 to be connected to the communication controller 23 is selected next in step S112. By performing the masking process, when the antenna 21 is selected in step S112, the same antenna 21 is prevented from being continuously connected to the communication controller 23.

In step S119, the CPU 24 increments the variable L. Further, the CPU 24 assigns '0' to the variable n. The CPU 24 returns to step S112 after step S119.

In step S120, the CPU 24 cancels the mask processing of all the antennas 21. Also, ‘0’ is assigned to the variable L.

The above is the flow according to the modified example of the transmission process executed by the CPU 24. According to the above flow, the antenna 21 connected to the communication controller 23 is sequentially switched to the antenna 21 having the best average signal strength value among the antennas 21 not subjected to the mask processing. For example, when transmitting a radio wave signal to the wireless device 4, the antenna 21 connected to the communication controller 23 includes a first antenna 21a, a second antenna 21b, a third antenna 21c, a first antenna 21a, a second antenna 21b, and a first antenna. The antenna 21a and the third antenna 21c are switched in this order.

Any method can be adopted as the method of determining the order of switching the antennas 21 connected to the communication controller 23. Further, for example, in the above-mentioned process, the process may proceed to step S119 after step S120, and in step S119, only the process of substituting '0' for the variable n may be performed without incrementing the variable L. In this way, all the antennas are evenly switched in descending order of the average signal strength value. For example, when transmitting a radio wave signal to the wireless device 4, the antenna 21 connected to the communication controller 23 is the first antenna. The 21a, the second antenna 21b, the third antenna 21c, the first antenna 21a, the second antenna 21b, and the third antenna 21c are switched in this order.

The wireless device 2 may perform such a transmission process. By executing such a transmission process, it is possible to confirm whether or not wireless communication can be performed with another antenna even if the wireless communication environment changes due to an external factor and wireless communication cannot be performed with one antenna.

[Reception processing of wireless device in table data creation mode]
FIG. 7 shows a flowchart of reception processing in the table data (TD) creation mode executed by the CPU 24 of the wireless device 2. Hereinafter, the reception process in the TD creation mode will be described with reference to the flowchart. The CPU 24 starts this process when the wireless device 2 is first turned on. Further, the CPU 24 starts this process periodically (for example, every day, every week, every two hours, etc.). Hereinafter, the timing at which the main processing (reception processing in the TD creation mode) is periodically started is referred to as a reset timing.

In step S201, the CPU 24 defines the variable x and assigns '1' to the variable x. In step S202, the CPU 24 defines the variable n and assigns '0' to the variable y.

In step S203, the CPU 24 connects the xth antenna 21 to the communication controller 23. For example, the first antenna 21 corresponds to the antenna 21a, the second antenna 21 corresponds to the antenna 21b, and the third antenna 21 corresponds to the antenna 21c. The order of the antennas 21 connected to the communication controller 23 may be any order.

In step S204, the CPU 24 determines whether or not a radio wave signal has been received. Specifically, when the CPU 24 determines that the radio wave signal has not been received (S204; No), the CPU 24 returns to step S204 and waits for the reception of the radio wave signal. If the CPU 24 determines that the radio wave signal has been received (S204; Yes), the CPU 24 proceeds to step S205. The CPU 24 determines that the radio wave signal has been received when the signal strength measured by the measuring unit 234 is equal to or higher than a certain level or when the receiving means 24b reads a meaningful data unit.

In step S205, the CPU 24 analyzes the data unit (DU) included in the received radio wave signal and acquires information representing the source of the radio wave signal. Further, the CPU 24 acquires the RSSI of the radio wave signal from the measurement unit 234.

In step S206, the CPU 24 increments the variable y and determines whether or not the variable y is equal to the preset constant c3 (the upper limit of the number of RSSI acquisitions, for example 100). Specifically, when the CPU 24 determines that the variable y is smaller than the constant c3 (S206; No), the CPU 24 returns to step S204. Further, when the CPU 24 determines that the variable y is equal to the constant c3 (S206; Yes), the CPU 24 proceeds to step S207.

In step S207, the CPU 24 calculates the average signal strength value of the radio wave signal from each of the radio devices 3 and 4 received by the xth antenna based on the number of RSSIs equal to the constant c3. For example, the CPU 24 has average signal strength values TD11, TD21 and TD31 when x = 1, average signal strength values TD12, TD22 and TD32 when x = 2, and an average signal when x = 3. The intensity values TD13, TD23 and TD33 are calculated. Then, the CPU 24 stores the calculated average signal strength value in the memory 25 as the first table data 251a and the second table data 251b.

In step S208, the CPU 24 increments the variable x to determine whether or not the average signal strength values of all the antennas 21 have been calculated. Specifically, when the CPU 24 determines that the variable x is equal to or less than the constant Na ('3' in this embodiment) equal to the number of antennas 21 (S208; No), the process returns to step S202. Further, when the CPU 24 determines that the variable x is larger than the constant Na (S208; Yes), the CPU 24 proceeds to step S209.

When proceeding to step S209, the average signal strength values TD11 to TD23 are calculated, and the first table data 251a is completed. In addition, the second table data 251b is also created at the same time.

In step S209, the CPU 24 selects the antenna 21 to be connected to the communication controller 23 based on the second table data 251b. Then, the CPU 24 connects the selected antenna 21 to the communication controller 23 by controlling the AN switch 22. In the present embodiment, the antenna 21c having the largest average signal strength value TD33 among the average signal strength values TD31 to TD33 is connected to the communication controller 23.

As a result, the CPU 24 ends this process. After the completion of this processing, the CPU 24 starts the reception processing in the TD update mode described later. Therefore, the next time the radio signal is received, the antenna 21 selected in step S209, which is presumed to have a relatively good wireless communication environment, is used. Since a suitable antenna 21 is selected before receiving the radio signal, even if the preamble length of the data unit included in the radio signal is short, the situation that the antenna 21 cannot be selected does not occur, and the wireless device 2 is satisfactorily selected. Can perform wireless communication. That is, even if the optimum antenna cannot be selected during preamble reception due to the shortened preamble, the wireless device 2 controls the antenna switching cycle by CPU control while determining the RSSI acquisition status (table data creation status). Table data is created efficiently so that the optimum antenna can be selected.

The timing of switching the antenna 21 may be any timing. In this embodiment, the first antenna 21a acquires the number of RSSIs equal to the constant c3, then the second antenna 21b acquires the number of RSSIs equal to the constant c3, and then the third antenna 21c acquires the constant. The process of acquiring the RSSI of the number equal to c3 was performed. For example, the RSSI was acquired by the first antenna 21a, then the RSSI was acquired by the second antenna 21b, and then the RSSI was acquired by the third antenna 21a. The process of acquiring the above may be repeated a number of times equal to the constant c3.

[Modification example of reception processing in table data creation mode]
FIG. 8 shows a flowchart based on a modified example of the reception process in the TD creation mode. Hereinafter, a modified example of the reception process in the TD creation mode will be described with reference to the flowchart.

The flowchart according to this modification is equivalent to the flowchart in which steps S202, S204 and S206 of the flowchart according to the embodiment (FIG. 7) are replaced with steps S212, S214 and S216, respectively. Therefore, in this modification, the description of the same steps as the flowchart according to the embodiment will be omitted. As described above, the CPU 24 starts this process when the wireless device 2 is first turned on and periodically (at the time of reset timing).

In step S212, the CPU 24 starts timing by the timing means 24e. Further, in step S214, when the CPU 24 determines that the radio wave signal has been received (S214; Yes), the process proceeds to step S205, and when it is determined that the radio wave signal has not been received (S214; No), the process proceeds to step S216. ..

In step S216, the CPU 24 determines whether or not a certain time (for example, 10 s) has elapsed since the start of time counting. Specifically, when the CPU 24 determines that a certain time has not elapsed since the start of timekeeping (S216; No), the process returns to step S214. If the CPU 24 determines that a certain time has elapsed since the start of timekeeping (S216; Yes), the CPU 24 proceeds to step S207.

The wireless device 2 may perform reception processing in such a TD creation mode. When the reception processing in the TD creation mode described in [Reception processing in the table data creation mode of the wireless device] and [Variation example of reception processing in the table data creation mode] is executed for the second time or later, the memory 25 The first table data 251a and the second table data 251b stored in the memory 25 may be deleted and a new data group 251 may be recreated, or the first table data 251a and the second table stored in the memory 25 may be recreated. The data group 251 may be created by taking over all or part of the data 251b.

[Reception processing of wireless device in table data update mode]
FIG. 9 shows a flowchart of reception processing in the table data (TD) update mode executed by the CPU 24 of the wireless device 2. Hereinafter, the reception process in the TD update mode will be described with reference to the flowchart. The CPU 24 starts this process after the reception process in the TD creation mode is completed.

In step S301, the CPU 24 determines whether or not a radio wave signal has been received. Specifically, when the CPU 24 determines that the radio wave signal has not been received (S301; No), the CPU 24 returns to step S301 and waits for the reception of the radio wave signal. If the CPU 24 determines that the radio wave signal has been received (S301; Yes), the CPU 24 proceeds to step S302.

In step S302, the CPU 24 analyzes the data unit (DU) included in the received radio wave signal and acquires information representing the source of the radio wave signal. Further, the CPU 24 acquires the RSSI of the radio wave signal from the measurement unit 234.

In step S303, the CPU 24 updates the first table data 251a based on the information representing the source of the radio wave signal and the acquired RSSI. For example, when the radio wave signal is transmitted from the radio device 3 and the radio wave signal is received by the antenna 21c, the average signal strength value TD13 is updated to the value calculated by (TD13 + acquired RSSI) / 2. Further, when the radio wave signal is transmitted from the radio device 4 and the radio wave signal is received by the antenna 21a, the average signal strength value TD21 is updated to the value calculated by (TD21 + acquired RSSI) / 2.

At the same time, the CPU 24 updates the second table data 251b based on the information representing the source of the radio wave signal and the acquired RSSI. For example, when the radio wave signal is received by the antenna 21c, the average signal strength value TD33 is updated to the numerical value calculated by (TD33 + acquired RSSI) / 2.

The average signal strength value of the radio wave signal received by the antenna 21 may be calculated and updated by any method. For example, when the radio wave signal is transmitted from the radio device 3 and the radio wave signal is received by the antenna 21c, the average signal strength value TD13 is set to (the radio wave signal from the radio wave device 3 received by the antenna 21c). It may be updated to the numerical value calculated by the total of the RSSIs acquired up to now + the acquired RSSI) / (the number of RSSIs acquired so far of the radio wave signal from the radio device 3 received by the antenna 21c + 1). Further, for example, the average signal strength value TD13 is updated to a moving average value calculated based on the most recently acquired predetermined number (for example, 100) RSSI of the radio wave signal from the radio device 3 received by the antenna 21c. You may.

In step S304, the CPU 24 selects the antenna 21 to be connected to the communication controller 23 based on the comparison between the acquired RSSI and the second table data 251b. For example, when the acquired RSSI is the signal intensity value of the radio wave signal received by the antenna 21c, the CPU 24 has the acquired RSSI equal to both the average signal intensity values TD31 and TD32 of the antennas 21a and 21b excluding the antenna 21c. When it is large (step S304; No), the process proceeds to step S306 without switching the antenna 21. Further, when the acquired RSSI is smaller than either of the average signal strength values TD31 and TD32 (step S304; Yes), the CPU 24 proceeds to step S305.

In step S305, the CPU 24 further selects an antenna 21 to be connected to the communication controller 23. For example, when the antenna 21c is connected to the communication controller 23, the CPU 24 determines that the antenna 21c connected to the communication controller 23 is either the antenna 21a or the antenna 21b and has a larger average signal strength value. In the embodiment, the antenna is changed to the antenna 21b. Note that step S304 may not be provided, and step S305 may always be executed after step S303. In step S304, the latest RSSI and TD are compared, but in step S305, since the TD reference, the influence of only the latest RSSI is small, and the antenna having the maximum average value of RSSI is selected.

In step S306, the CPU 24 determines whether or not it is the reset timing. That is, the CPU 24 determines whether or not a certain time (for example, one day, one week, two hours, etc.) has elapsed since the end of the TD creation mode. Specifically, when the CPU 24 determines that it is not the reset timing (S306; No), the CPU 24 returns to step S301 and waits for the reception of the radio wave signal. Further, when the CPU 24 determines that the reset timing is reached (S306; Yes), the CPU 24 ends this process. After the completion of this processing, the CPU 24 starts the reception processing in the above-mentioned TD creation mode.

As a result, the CPU 24 ends this process. When receiving the radio wave signal in step S301, the antenna 21 selected in step S304 or step S305, which is presumed to have a relatively good wireless communication environment, is used. Since a suitable antenna 21 is selected before receiving the radio signal, even if the preamble length of the data unit included in the radio signal is short, the situation that the antenna 21 cannot be selected does not occur, and the wireless device 2 is satisfactorily selected. Can perform wireless communication.

[First modification of reception processing in table data update mode]
FIG. 10 shows a flowchart according to the first modification of the reception process in the TD update mode. The CPU 24 may receive the radio wave signal and update the table data by the following processing.

The flowchart according to this modification is equivalent to the flowchart in which step S304 and step S305 of the flowchart according to the embodiment (FIG. 9) are replaced with step S314. Therefore, in this modification, the description of the same steps as the flowchart according to the embodiment will be omitted.

In step S314, the CPU 24 changes the antenna 21 (for example, the antenna 21a) connected to the communication controller 23 to another antenna 21 (for example, the antenna 21b or the antenna 21c) without being based on the data group 251. The order in which the antennas 21 are changed may be any order. However, it is preferable that each of the antennas 21 is evenly connected to the communication controller 23.

The flowchart according to the first modification of the reception processing in the TD update mode has been described above. Such processing does not contribute to the optimum selection of the antenna at the time of reception, but the table data for selecting the antenna at the time of transmission can be updated at any time. Therefore, since the length of the preamble included in the received radio signal is short, the situation that the antenna 21 cannot be selected at the time of transmission does not occur, and the wireless device 2 can perform good wireless communication.

[Second modification of reception processing in table data update mode]
FIG. 11 shows a flowchart according to a second modification of the reception process in the TD update mode. The CPU 24 may receive a radio wave signal by the following processing.

In the flowchart according to this modification, step S304 and step S305 according to the embodiment (FIG. 9) are eliminated, step S321 is added before step S301, and step S322 is inserted between steps S301 and S302. It is equivalent to the added flowchart. Therefore, in this modification, the description of the same steps as the flowchart according to the embodiment will be omitted.

In step S321, the CPU 24 starts the antenna switching process described later. In step S322, the CPU 24 stops the antenna switching process described later.

FIG. 12 shows a flowchart of the antenna switching process that is processed in parallel with the reception process in the TD update mode. The CPU 24 starts this process when step S321 in the receive process is executed.

In step S401, the CPU 24 connects any of the antennas 21 to the communication controller 23. The order of the antennas 21 connected to the communication controller 23 may be any order.

In step S402, the CPU 24 starts timing by the timing means 24e. In step S403, the CPU 24 determines whether or not a certain time (for example, 500 μs) has elapsed since the start of timekeeping. Specifically, when the CPU 24 determines that a certain time has not elapsed since the start of timekeeping (S403; No), the CPU 24 returns to step S403 and waits for the elapse of a certain time. If the CPU 24 determines that a certain time has elapsed since the start of timekeeping (S403; Yes), the CPU 24 proceeds to step S404.

In step S404, the CPU 24 determines whether or not to stop the antenna switching. Specifically, if the CPU 24 has not yet executed step S322 in the reception process (S404; No), the CPU 24 returns to step S401 and changes the antenna 21 connected to the communication controller 23. Further, when the step S322 in the reception process is executed (S404; Yes), the CPU 24 ends this process.

In this modification, the connection between the antenna 21 and the communication controller 23 is periodically switched. Therefore, as in [the first modification of the reception process in the table data update mode], the antenna 21 cannot be selected at the time of transmission because the length of the preamble included in the received radio signal signal is short, and the radio wave is used. The device 2 can perform wireless communication satisfactorily.

As described above, the function realized by the CPU 24 can also be realized by the communication controller 23. Therefore, for example, the CPU 24 may perform the reception process (TD update mode) shown in FIG. 11, and the communication controller 23 may perform the antenna switching process shown in FIG. 12. At that time, in the reception process (TD update mode) shown in FIG. 11, even if the CPU 24 performs steps S321, S302, S303 and S306 and the communication controller 23 performs steps S301 and S322 (the communication controller 23 that has received the radio wave signal). However, the process shown in FIG. 12 may be stopped by itself). Any step of the various processes may be processed by either the communication controller 23 or the CPU 24.

The transmission process and the reception process related to the wireless communication of the wireless device 2 have been described above. Further, regarding the reception process, the TD creation mode and the TD update mode have been described. The combination of embodiments and modifications of each process / mode can be appropriately selected.

Further, in the reception process, it is not necessary to distinguish between the TD creation mode and the TD update mode. Hereinafter, as a modification of the reception process, a reception process without mode separation will be described.

[Modification example of reception processing]
FIG. 13 shows a flowchart based on a modified example of the reception process. Hereinafter, a modified example of the reception process executed by the CPU 24 will be described with reference to the flowchart. The CPU 24 starts this process when the power is turned on to the wireless device 2.

The flowchart according to this modification is equivalent to the flowchart in which step S303 of the flowchart (FIG. 10) according to the first modification of the reception process in the TD update mode is replaced with step S333 and step S306 is eliminated. Therefore, in this modification, the same steps as the flowchart according to the first modification of the reception process in the TD update mode will be omitted.

In step S333, the CPU 24 creates or updates the first table data 251a based on the information representing the source of the radio wave signal and the acquired RSSI. For example, the CPU 24 stores the RSSI of the radio wave signal from the radio device 3 first received by the antenna 21a in the memory 25 as the table data TD11. Then, the numerical value calculated based on the RSSI of the radio wave signal from the radio device 3 received by the antenna 21a for the second time and the table data TD11 (first RSSI) stored in the memory 25 is used as the average signal strength value TD11. As a result, it is saved in the memory 25. After that, the CPU 24 updates the average signal strength value TD11 based on the RSSI of the radio wave signal from the radio device 3 received by the antenna 21a. The CPU 24 performs the same processing on the radio wave signals from each of the wireless devices 3 and 4 received by each of the antennas 21, and creates or updates the first table data 251a composed of the average signal strength values TD11 to TD11-23.

In this modification, the CPU 24 returns to step S301 after executing step S314. After that, the CPU 24 repeats the reception of the radio wave signal and the creation / update of the first table data 251a.

The CPU 24 may execute such a reception process. Further, the CPU 24 replaces step S303 with step S333 in the flowchart (FIG. 11) according to the second modification of the reception process in the TD update mode, eliminates step S306, and returns to step S321 after step S333. By changing the mode, it is possible to execute the reception process without switching between the TD creation mode and the TD update mode, as in the above-mentioned modification of the reception process (FIG. 13). The CPU 24 may execute a reception process of repeatedly receiving a radio wave signal and creating / updating the first table data 251a according to the flowchart changed in this way.

[Other variants]
In the embodiment described above and the modified example thereof, an example in which the wireless device 2 has three antennas 21 has been described. However, the number of antennas 21 may be two or four or more.

Further, in the embodiment described above and the modified example thereof, an example in which two external devices communicate with the wireless device 2 have been described. However, there may be three or more external devices.

In addition to these, the information (average signal strength values TD11 to TD23) constituting the first table data 251a is not limited to six. Similarly, the information (average signal strength values TD31 to TD33) constituting the second table data 251b is not limited to three. Further, the information constituting the data group 251 is not limited to the average signal strength value, and may be other parameters representing the status of the wireless communication environment, for example, the communication success rate with an external device.

Further, the table data creation mode may not be implemented in the reception process. Even when only the table data update mode is implemented, the data group 251 can be created / updated. However, if the table data creation mode is not implemented, the wireless communication environment of each of the antennas 21 may not be accurately evaluated unless the information regarding the signal strength of the radio wave signal is accumulated more than a certain amount. Therefore, it is preferable that the table data creation mode is implemented.

Further, in the reception process in the above-mentioned TD creation mode, the passive scan function of IEEE802.1.5 may be started at the beginning of the process, and the passive scan function may be terminated at the end of the process. Passive scan is a function to check the wireless devices that have already entered the network in the vicinity by continuing to receive (standby) only the transmission signal from the external device, from the start to the end of the passive scan. During that time, no signal is transmitted from the own radio, only the transmission signal from the external device is received and monitored. Therefore, by using the passive scan function in the reception processing in the TD creation mode, the RSSI of the radio wave signal from the surrounding wireless devices is efficiently acquired, and the optimum antenna is selected and operated immediately from the start of operation. be able to.

Further, in the embodiment described above and the modified example thereof, an example in which the CPU 24 performs operations related to various functions, control of various hardware units, and the like by software has been described. However, those operations and controls may be performed by hardware, for example, by a dedicated logic circuit.

Although the present disclosure has been described above with reference to the embodiments and variations thereof, the present disclosure is not limited thereto. It is obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

1 Communication network system 2 Wireless device 21 Antenna 22 Antenna (AN) switch element (antenna switching means)
23 Communication controller (signal processing means)
231 Transmission / reception switching unit 232 Modulation unit 233 Demodulation unit 234 Measurement unit 24 CPU
24a Transmitting means 24b Receiving means 24c Arithmetic means 24d Control means 24e Timekeeping means 25 Memory (storage means)
251 Data group 252 Program 26 I / F controller (connection means)
3 Wireless device 4 Wireless device 5 Aggregator

Claims (10)

It is a wireless device that constitutes a network conforming to the communication standard of IEEE802.1.5 together with a plurality of external devices.
With multiple antennas
Signal processing means for processing radio signals and
An antenna switching means for connecting any of the plurality of antennas to the signal processing means,
A storage means for storing a data group relating to a signal strength of a radio wave signal received by each of the plurality of antennas, and a storage means.
Before starting communication with each of the plurality of external devices via the data unit including the preamble, a data group relating to the signal strength of the radio wave signal received by each of the plurality of antennas is stored in the storage means in advance, and the storage means is described. One antenna is selected from the plurality of antennas based on the data group stored in advance in the storage means, and the selected antenna is connected to the signal processing means by controlling the antenna switching means. Control means and
Equipped with
The data group includes first table data which is information on signal strength of radio wave signals from each of the plurality of external devices received by each of the plurality of antennas.
When transmitting a radio wave signal to the external device, the control means selects a first antenna, which is one of the plurality of antennas, based on the first table data.
Wireless device. The data group includes, as the first table data, an average signal strength value calculated based on a plurality of past signal strengths.
The wireless device according to claim 1. The data group includes the second table data which is information about the signal strength of the radio wave signal from the plurality of external devices received by each of the plurality of antennas.
When transmitting a radio wave signal to the external device, the control means selects the first antenna based on the first table data, and when receiving the radio wave signal, the plurality of control means is based on the second table data. Select one of the antennas in the
The wireless device according to claim 1 or 2. The data group includes, as the second table data, an average signal strength value calculated based on the plurality of past signal strengths.
The wireless device according to claim 3. The signal processing means includes a measuring unit for measuring the signal strength of an input radio wave signal.
Further comprising an arithmetic means for generating the data group based on the information on the signal strength measured by the measuring unit of the radio wave signal received by each of the plurality of antennas.
The wireless device according to any one of claims 1 to 4. The arithmetic means updates the data group based on the information about the signal strength measured by the measuring unit.
The wireless device according to claim 5. The control means selects an antenna to be connected to the signal processing means from the plurality of antennas based on a comparison between the information regarding the signal strength measured by the measuring unit and the updated data group. ,
The wireless device according to claim 6. When receiving a radio wave signal, the control means connects each of the plurality of antennas to the signal processing means in order without being based on the data group.
The wireless device according to claim 1 or 2. It is an antenna selection method for a wireless device that comprises a network conforming to the communication standard of IEEE802.154 together with a plurality of external devices and has a plurality of antennas and a signal processing means for processing a radio wave signal.
Before starting communication with each of the plurality of external devices via the data unit including the preamble, a data group relating to the signal strength of the radio wave signal received by each of the plurality of antennas is stored in advance in the storage means and stored in advance. Based on the data group, one of the plurality of antennas is selected as the antenna to be used for wireless communication.
The data group includes first table data which is information on signal strength of radio wave signals from each of the plurality of external devices received by each of the plurality of antennas.
When transmitting a radio wave signal to the external device, a first antenna, which is one of the plurality of antennas, is selected based on the first table data.
Antenna selection method. For a computer of a wireless device that constitutes a network conforming to the communication standard of IEEE802.154 together with a plurality of external devices and is equipped with a plurality of antennas and a signal processing means for processing a radio wave signal.
Before starting communication with each of the plurality of external devices via the data unit including the preamble, a data group relating to the signal strength of the radio wave signal received by each of the plurality of antennas is stored in advance in the storage means and stored in advance. Based on the data group, one antenna is selected from the plurality of antennas as an antenna to be used for wireless communication.
The data group includes first table data which is information on signal strength of radio wave signals from each of the plurality of external devices received by each of the plurality of antennas.
When transmitting a radio wave signal to the external device, the first antenna, which is one of the plurality of antennas, is selected based on the first table data.
program.

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