JP7489718B2 - Wireless communication device, communication control method and program - Google Patents

Description

The present invention relates to a wireless communication device, a communication control method, and a program.

A wireless communication device has been proposed that communicates using a modulation and coding scheme (MCS) selected from among a plurality of coding schemes and modulation schemes based on the success rate of transmitting frames corresponding to each of the plurality of MCSs to other wireless communication devices (see, for example, Patent Document 1).

JP 2018-093296 A

However, in a wireless communication device such as that described in Patent Document 1, there is a demand for increasing the amount of data that can be transmitted within a unit time by increasing the communication rate while maintaining a high level of success rate in transmitting frames to other wireless communication devices.

The present invention has been made in consideration of the above-mentioned reasons, and aims to provide a wireless communication device, a communication control method, and a program that can reduce frame loss while increasing the amount of data that can be transmitted within a unit time.

In order to achieve the above object, a wireless communication device according to the present invention comprises:
a size determination unit that determines a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
a symbol number calculation unit that calculates a number of symbols necessary to transmit the transmission data frame, for each of a plurality of preset modulation and coding schemes, based on the transmission data size and a symbol unit data size that can be included in one symbol in each of the plurality of modulation and coding schemes;
A selection unit that selects, from the plurality of types of modulation and coding schemes, a modulation and coding scheme that minimizes the calculated number of symbols,
When there are multiple modulation and coding schemes that result in the smallest calculated number of symbols, the selection unit selects one modulation and coding scheme from the multiple modulation and coding schemes that result in the smallest number of symbols, excluding the modulation and coding scheme that results in the largest symbol-unit data size.

A communication control method according to another aspect of the present invention comprises:
Identifying a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
calculating a number of symbols required to transmit the transmission data frame based on the transmission data size and a symbol-unit data size that can be included in one symbol in each of a plurality of preset modulation and coding schemes;
selecting a modulation and coding scheme that minimizes the calculated number of symbols from among the plurality of types of modulation and coding schemes;
and when there are a plurality of modulation and coding schemes which result in the smallest calculated number of symbols, selecting one modulation and coding scheme from the plurality of modulation and coding schemes which result in the smallest number of symbols excluding the modulation and coding scheme which results in the largest symbol-unit data size.

From another aspect, the program according to the present invention is
Computer,
a size determination unit that determines a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
a symbol number calculation unit that calculates, for each of a plurality of preset modulation and coding schemes, a number of symbols necessary to transmit the transmission data frame based on the transmission data size and a symbol unit data size that can be included in one symbol in each of the plurality of modulation and coding schemes;
a selection unit that selects, from the plurality of types of modulation and coding schemes, a modulation and coding scheme with which the calculated number of symbols is the smallest, and, when there are a plurality of modulation and coding schemes with which the calculated number of symbols is the smallest, selects one modulation and coding scheme from the plurality of modulation and coding schemes with which the number of symbols is the smallest, excluding the modulation and coding scheme with which the symbol-unit data size is the largest;
Function as.

According to the wireless communication device of the present invention, the symbol number calculation unit calculates the number of symbols required to transmit the transmission data frame for each of the plurality of preset modulation and coding methods based on the transmission data size included in the transmission data frame to be transmitted to another wireless communication device and the symbol unit data size that can be included per symbol for each of the plurality of modulation and coding methods. The selection unit also selects the modulation and coding method that minimizes the calculated number of symbols from among the plurality of modulation and coding methods. Then, when there are a plurality of modulation and coding methods that minimize the calculated number of symbols, the selection unit selects one modulation and coding method from among the plurality of modulation and coding methods that minimize the number of symbols, excluding the modulation and coding method that maximizes the symbol unit data size that can be included per symbol. This makes it possible to reduce the number of symbols required to transmit the transmission data frame while minimizing the symbol unit data size in transmitting the transmission data frame. Therefore, it is possible to reduce frame loss by minimizing the symbol unit data size in transmitting the transmission data frame while reducing the number of symbols required to transmit the transmission data frame and increasing the amount of data that can be transmitted within a unit time.

1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention; FIG. 2 is a diagram illustrating a hardware configuration of a wireless communication device according to an embodiment. FIG. 2 is a diagram illustrating a functional configuration of a wireless communication device according to an embodiment. 4 is a diagram showing the contents of information stored in a DBPS storage unit according to the embodiment; FIG. 5 is a flowchart showing a flow of a communication control process executed by the wireless communication device according to the embodiment. FIG. 1A is a diagram showing the number of symbols corresponding to each MCS when a wireless communication device according to an embodiment transmits 100 bytes of information; FIG. 1B is a diagram showing the number of symbols corresponding to each MCS when a wireless communication device according to an embodiment transmits 170 bytes of information; and FIG. 1C is a diagram showing the number of symbols corresponding to each MCS when a wireless communication device according to an embodiment transmits 6 bytes of information. FIG. 13 is a diagram showing the contents of information stored in a DBPS storage unit according to a modified example. FIG. 13 is a diagram showing the contents of information stored in a DBPS storage unit according to a modified example.

A wireless communication device according to an embodiment of the present invention will be described in detail below with reference to the drawings. The wireless communication device according to this embodiment includes a data size determination unit that determines a transmission data size included in a frame to be transmitted to another wireless communication device, a symbol number calculation unit, and a selection unit that selects an MCS suitable for communication with another wireless communication device from among a plurality of types of modulation and coding schemes (hereinafter referred to as "MCSs"). Here, the symbol number calculation unit calculates the number of symbols required to transmit the frame for each of the plurality of types of MCS based on the transmission data size and the symbol unit data size that can be included per symbol in each MCS. In addition, the selection unit specifies an MCS with the smallest calculated number of symbols from among the plurality of types of MCS, and if there are multiple specified MCSs, selects an MCS with the smallest symbol unit data size from among the specified plurality of MCSs.

For example, as shown in FIG. 1, wireless communication devices 1 and 2 according to this embodiment are used to construct a wireless LAN (Local Area Network) to which a PC (Personal Computer) 3 having wireless communication capabilities is connected. The wireless communication device 1 functions as a station connected to a wide area network NW1 such as the Internet via, for example, a data circuit-terminating equipment (hereinafter referred to as "DCE") 4. The wireless communication device 2 functions as an access point that relays data transmitted and received between, for example, the PC 3 and the wireless communication device 1. Here, the PC 3 obtains data from a server (not shown) connected to the wide area network NW1 via the DCE 4 and the wireless communication devices 1 and 2, and transmits data to the server via the wireless communication devices 2 and 1, the DCE 4, and the wide area network NW1.

Next, as shown in FIG. 2, the wireless communication devices 1 and 2 according to the present embodiment include a CPU (Central Processing Unit) 101, a main memory unit 102, an auxiliary memory unit 103, and a wireless module 105. The wireless communication device 1 also includes an interface (not shown) that is connected to the DCE 4 by wire. The main memory unit 102 is composed of a volatile memory such as a RAM (Random Access Memory), and is used as a working area for the CPU 101. The auxiliary memory unit 103 is composed of a non-volatile memory such as a ROM (Read Only Memory), or an SSD (Solid State Drive), HDD (Hard Disk Drive), etc., and stores a program for controlling the wireless communication devices 1 and 2. The CPU 101 reads the program stored in the auxiliary memory unit 103 into the main memory unit 102 and executes it.

The wireless module 105 communicates in a communication method conforming to the wireless LAN standard of, for example, IEEE802.11. The wireless module 105 has an antenna (not shown), a receiving circuit (not shown), a signal processing unit (not shown), and a transmitting circuit (not shown). The receiving circuit receives a wireless signal via an antenna, demodulates a signal corresponding to the received wireless signal to generate a baseband signal, and outputs the baseband signal to the signal processing unit. The transmitting circuit generates a wireless signal corresponding to a transmission frame by modulating a carrier signal using a baseband signal input from the signal processing unit, and transmits the generated wireless signal via the antenna. Here, the transmitting circuit modulates the carrier signal with a modulation method corresponding to the MCS information based on the MCS information instructed by the CPU 101. The signal processing unit is realized by, for example, a DSP (Digital Signal Processor), and generates a frame corresponding to the wireless signal received by the receiving circuit based on the baseband signal input from the receiving circuit, and sends it to the bus 109. The signal processing unit also generates a baseband signal based on the frame transferred from the main memory unit 102 via the bus 109 and outputs it to the transmission circuit.

In the wireless communication device 1, the CPU 101 loads the program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a frame acquisition unit 111, a size determination unit 112, a symbol number calculation unit 113, a selection unit 114, and a frame transfer unit 115, as shown in FIG. 3. The wireless communication device 2 is similar. The auxiliary storage unit 103 shown in FIG. 2 also has a DBPS (Data Bit Per Symbol) storage unit 131. As shown in FIG. 4, for example, the DBPS storage unit 131 stores DBPS, which is the symbol unit data size that can be included per symbol, in association with an MCS identification number that identifies each MCS. The example shown in FIG. 4 shows an example in which the wireless communication devices 1 and 2 transmit frames with one stream and a bandwidth of 4 MHz. Furthermore, the main storage unit 102 shown in FIG. 2 also functions as a frame buffer 121 that temporarily stores frames acquired from the wireless module 105 or DCE4, as shown in FIG. 3.

The frame acquisition unit 111 of wireless communication device 1 acquires frames transmitted to wireless communication device 2 from the wireless module 105 or an interface connected to DCE4. Meanwhile, the frame acquisition unit 111 of wireless communication device 2 acquires transmission data frames transmitted to wireless communication device 1 from the wireless module 105. The frame acquisition units 111 of wireless communication devices 1 and 2 each store the acquired transmission data frames in the frame buffer 121.

The size specification unit 112 specifies the transmission data size, which is the size of the data contained in the frame stored in the frame buffer 121. Here, the size specification unit 112 of wireless communication device 1 specifies the transmission data size of the transmission data frame to be transmitted to wireless communication device 2. Meanwhile, the size specification unit 112 of wireless communication device 2 specifies the transmission data size of the transmission data frame to be transmitted to wireless communication device 1. Then, the size specification unit 112 notifies the symbol number calculation unit 113 of the transmission data size information indicating the specified transmission data size.

The symbol number calculation unit 113 refers to the DBPS information corresponding to each MCS stored in the DBPS storage unit 131, and calculates the number of symbols required to transmit a transmission data frame for each of the multiple types of MCS, based on the transmission data size indicated by the transmission data size information notified by the size specification unit 112 and the DBPS for each of the multiple types of MCS. Specifically, the symbol number calculation unit 113 calculates the number of symbols SYM required to transmit a transmission data frame for each of the multiple types of MCS, using the relational expression shown in the following formula (1).

Here, Nt indicates the transmission data size (number of bits) contained in the transmission data frame, and Ndbps indicates the symbol-unit data size (number of bits) that can be contained per symbol. Roundup(*) indicates a function that rounds up the argument to the nearest whole number and outputs it. Furthermore, the symbol number calculation unit 113 notifies the selection unit 114 of symbol number information indicating the calculated number of symbols SYM corresponding to each MCS.

Based on the symbol number information notified by the symbol number calculation unit 113, the selection unit 114 identifies the MCS with the smallest calculated number of symbols from among multiple types of MCS. If there are multiple identified MCSs, the selection unit 114 selects the MCS with the smallest DBPS from among the multiple identified MCSs. The selection unit 114 then generates MCS information indicating the selected MCS and transfers it to the wireless module 105. After transferring the generated MCS information to the wireless module 105, the selection unit 114 notifies the frame transfer unit 115 of MCS transfer notification information notifying that the MCS information has been transferred to the wireless module 105.

When the frame forwarding unit 115 receives the MCS forwarding notification information from the selection unit 114, it forwards the transmission data frame stored in the frame buffer 121 to the wireless module 105.

Next, the communication control process executed by the wireless communication devices 1 and 2 according to the present embodiment will be described in detail with reference to FIG. 5 and FIG. 6. The values shown in FIG. 6 in the present embodiment are based on the IEEE 802.11ah standard, but are not limited thereto. This communication control process is started, for example, when the wireless communication devices 1 and 2 are powered on. First, in the case of the wireless communication device 1, the frame acquisition unit 111 determines whether or not a transmission data frame has been acquired from the wireless communication device 1 or the DCE 4 via the wireless module 105 or the interface (step S1). In the case of the wireless communication device 2, the frame acquisition unit 111 determines whether or not a frame has been acquired from the wireless communication device 2 via the wireless module 105. Here, the frame acquisition unit 111 repeatedly executes the process of step S1 as long as it determines that a frame has not been acquired (step S1: No).

On the other hand, when the frame acquisition unit 111 determines that it has acquired a transmission data frame (step S1: Yes), it stores the acquired transmission data frame in the frame buffer 121. Then, the size determination unit 112 determines the transmission data size of the transmission data frame stored in the frame buffer 121 (step S2). Here, the size determination unit 112 notifies the symbol number calculation unit 113 of transmission data size information indicating the determined transmission data size.

Next, the symbol number calculation unit 113 calculates the number of symbols required to transmit the transmission data frame for each of the multiple types of MCSs, based on the transmission data size indicated by the transmission data size information notified by the size specification unit 112 and the DBPS of each of the multiple types of MCSs, using the above-mentioned formula (1) (step S3). Here, the number of symbols for each MCS calculated by the symbol number calculation unit 113 is, for example, as shown in FIG. 6(A) when the transmission data frame is transmitted with one stream and a bandwidth of 4 MHz, when the transmission data size is 100 Byte, as shown in FIG. 6(B) when the transmission data size is 170 Byte, and as shown in FIG. 6(C) when the transmission data size is 6 Byte. Then, the symbol number calculation unit 113 notifies the selection unit 114 of the symbol number information indicating the calculated number of symbols corresponding to each MCS.

Returning to FIG. 5, the selection unit 114 then identifies the MCS with the smallest calculated number of symbols from among the multiple types of MCSs based on the symbol number information notified by the symbol number calculation unit 113 (step S4). For example, as shown in FIG. 6(A), when the transmission data size is 100 Bytes, the selection unit 114 identifies MCSs with MCS identification numbers of "5" to "9" (MCSs with two symbols). For example, as shown in FIG. 6(B), when the transmission data size is 170 Bytes, the selection unit 114 identifies only MCSs with MCS identification number "9" (MCSs with two symbols). For example, as shown in FIG. 6(C), when the transmission data size is 6 Bytes, the selection unit 114 identifies all MCSs (MCSs with one symbol).

Returning to FIG. 5, the selection unit 114 then determines whether there are multiple MCSs with the smallest number of symbols (step S5). Here, it is assumed that the selection unit 114 determines that there is only one MCS with the smallest number of symbols (step 5: No). For example, as shown in SM2 in FIG. 6(B), there is only one MCS with the minimum number of symbols, "2". In this case, the processing of step S7 described below is executed, and MCS information indicating the MCS corresponding to the MSC identification number shown in SM2 in FIG. 6(B) is transferred to the wireless module 105.

On the other hand, suppose that the selection unit 114 determines that there are multiple MCSs with the smallest number of symbols, as shown in FIG. 5 (step S5: Yes). For example, as shown in FIG. 6(A) or FIG. 6(C), there are multiple MCSs with the smallest number of symbols. In this case, the selection unit 114 selects the MCS with the smallest DBPS from the multiple MCSs identified, as shown in FIG. 5 (step S6). Specifically, when the transmission data size is 100 Bytes, the selection unit 114 selects the MCS with MCS identification number "5" with DBPS of the minimum value of 432 bits from the MCSs with the number of symbols "2", as shown in SM1 in FIG. 6(A). Also, when the transmission data size is 6 Bytes, the selection unit 114 selects the MCS with MCS identification number "0" with DBPS of the minimum value of 54 bits from all MCSs with the number of symbols "1", as shown in SM3 in FIG. 6(C).

Returning to FIG. 5, next, the selection unit 114 generates MCS information indicating the selected MCS and transfers it to the wireless module 105 (step S7). At this time, after transferring the generated MCS information to the wireless module 105, the selection unit 114 notifies the frame transfer unit 115 of MCS transfer notification information notifying that the MCS information has been transferred to the wireless module 105.

Next, when the frame forwarding unit 115 receives the MCS forwarding notification information from the selection unit 114, it forwards the transmission data frame stored in the frame buffer 121 to the wireless module 105 (step S8). After that, the process of step S1 is executed again.

In Japan, there are strict restrictions on wireless transmission time, such as a 10% duty cycle regulation in the 900 MHz band. For example, when communicating according to the 802.11ah wireless LAN standard, in an environment with such restrictions, it is important to suppress the wireless transmission time. When it is desired to transmit many transmission data frames within a unit time, it is common to communicate with an MCS with a high transmission rate. However, when wireless communication is performed with an MCS with a high transmission rate and a large DBPS, it is susceptible to the influence of noise, and the probability that the transmission data frame will arrive is lower than with an MCS with a low transmission rate and a small DBPS. Furthermore, if the transmission data frame does not arrive, the transmission data frame will be retransmitted, resulting in the allocation of wireless transmission time being consumed in excess. In addition, wireless communication devices that comply with the IEEE 802.11 wireless LAN standard generally automatically select an MCS with the highest possible transmission rate and attempt to transmit. In this case, even in an environment where it is not appropriate to use an MCS with a high transmission rate, transmission is attempted using an MCS with an unnecessarily high transmission rate, resulting in frequent retransmissions of the transmitted data frame, and as a result, the allocated wireless transmission time is wasted.

In contrast, according to the wireless communication devices 1 and 2 of the present embodiment, the symbol number calculation unit 113 calculates the number of symbols required to transmit the transmission data frame for each of the multiple types of MCSs based on the transmission data size included in the transmission data frame and the DBPS of each of the multiple types of MCSs. Then, the selection unit 114 identifies the MCS with the smallest calculated number of symbols from among the multiple types of MCSs. Here, if there are multiple identified MCSs, the selection unit 114 selects the MCS with the smallest DBPS from among the multiple identified MCSs. This makes it possible to reduce the number of symbols required to transmit the transmission data frame while minimizing the DBPS in frame transmission as much as possible. Therefore, while reducing the number of symbols required to transmit the transmission data frame and increasing the amount of data that can be transmitted within a unit time, stable frame transmission can be achieved by minimizing the DBPS in the transmission of the transmission data frame as much as possible, and as a result, frame loss can be reduced. Therefore, the frequency of retransmission of the transmission data frame is reduced, and wasteful consumption of the allocated wireless transmission time can be suppressed.

Although the embodiment of the present invention has been described above, the present invention is not limited to the configuration of the above-mentioned embodiment. For example, when there are multiple MCSs with the smallest number of symbols calculated by the symbol number calculation unit 113, the selection unit 114 may select any one MCS from the multiple MCSs with the smallest number of symbols, excluding the MCS with the largest DBPS.

In the embodiment, an example has been described in which the wireless communication devices 1 and 2 each have only one antenna and communicate with one stream and a bandwidth of 4 MHz. However, this is not limited to the above, and for example, the wireless communication devices 1 and 2 may each have two antennas and communicate with four streams and a bandwidth of 16 MHz. In this case, the DBPS storage unit 131 may store DBPS information such as that shown in FIG. 7 in association with the MCS identification number. Alternatively, the wireless communication devices 1 and 2 may each have one antenna as in the embodiment and communicate with one stream and a bandwidth of 1 MHz. In this case, the DBPS storage unit 131 may store DBPS information such as that shown in FIG. 8 in association with the MSC identification number. In addition, the DBPS storage unit 131 may store multiple patterns of DBPS information in accordance with these various aspects.

In the embodiment, an example has been described in which the frame acquisition unit 111 selects an MCS for transmitting a frame each time the frame acquisition unit 111 acquires the transmission data frame. However, this is not limiting, and for example, each time the frame acquisition unit 111 acquires a preset reference number of transmission data frames, the size determination unit 112 may identify the transmission data size of each of the reference number of frames acquired by the frame acquisition unit 111 and calculate the average value or median value of the identified transmission data sizes. Then, the symbol number calculation unit 113 may calculate the number of symbols for each MCS using the calculated average value or median value of the transmission data sizes.

Alternatively, each time a preset size determination time arrives, the size determination unit 112 may determine the transmission data size of each transmission data frame acquired by the frame acquisition unit 111 between that time and the previous size determination time, and calculate the average or median of the determined transmission data sizes.

With this configuration, by selecting an MCS with a higher transmission success rate depending on the transmission data size, the frequency of retransmissions in the wireless module 105 can be reduced, and the time required to transmit a data frame is reduced, which has the advantage of ensuring more time that can be used for frame transmission.

The various functions of the wireless communication device 1 according to the present invention can be realized by using a computer system equipped with a wireless communication module, without relying on a dedicated system. For example, a program for executing the above operations may be stored on a non-transitory recording medium (such as a CD-ROM) that can be read by a computer system and distributed to a computer connected to a network, and the program may be installed in the computer system to configure the wireless communication device 1 to execute the above-mentioned processes.

The method of providing the program to the computer is arbitrary. For example, the program may be uploaded to a server on a communication line and distributed to the computer via the communication line. The computer then starts up the program and executes it under the control of the OS in the same way as other applications. In this way, the computer functions as a wireless communication device 1 that executes the above-mentioned processing.

Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to these. The present invention includes suitable combinations of the embodiments and modifications, and suitable modifications thereto.

The wireless communication device of the present invention is suitable as an access point and station for use in a wireless LAN.

1, 2: Wireless communication device, 3: PC, 4: DCE, 101: CPU, 102: Main memory, 103: Auxiliary memory, 105: Wireless module, 111: Frame acquisition unit, 112: Size determination unit, 113: Symbol number calculation unit, 114: Selection unit, 115: Frame transfer unit, 121: Frame buffer, 131: DBPS storage unit, NW1: Network

Claims (5)

a size determination unit that determines a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
a symbol number calculation unit that calculates a number of symbols necessary to transmit the transmission data frame, for each of a plurality of preset modulation and coding schemes, based on the transmission data size and a symbol unit data size that can be included in one symbol in each of the plurality of modulation and coding schemes;
A selection unit that selects, from the plurality of types of modulation and coding schemes, a modulation and coding scheme that minimizes the calculated number of symbols,
the selection unit, when there are a plurality of modulation and coding schemes with the smallest calculated number of symbols, selects one modulation and coding scheme from the plurality of modulation and coding schemes with the smallest number of symbols, excluding the modulation and coding scheme with the largest symbol-unit data size.
Wireless communication device. the selection unit, when there are a plurality of modulation and coding schemes with the smallest calculated number of symbols, selects a modulation and coding scheme with the smallest symbol-unit data size from among the plurality of modulation and coding schemes with the smallest number of symbols.
The wireless communication device of claim 1 . The symbol number calculation unit calculates the number of symbols for each of the plurality of modulation and coding schemes, using the following relational expression (1), where Nt (bit) is the data size included in the transmission data frame, Ndbps (bit) is the symbol unit data size that can be included in one symbol, and SYM is the number of symbols.
3. A wireless communication device according to claim 1 or 2.
Identifying a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
calculating a number of symbols required to transmit the transmission data frame based on the transmission data size and a symbol-unit data size that can be included in one symbol in each of a plurality of preset modulation and coding schemes;
selecting a modulation and coding scheme that minimizes the calculated number of symbols from among the plurality of types of modulation and coding schemes;
and when there are a plurality of modulation and coding schemes with the smallest calculated number of symbols, selecting one modulation and coding scheme from the plurality of modulation and coding schemes with the smallest number of symbols, excluding the modulation and coding scheme with the largest symbol-unit data size.
Communications control method. Computer,
a size determination unit that determines a transmission data size included in a transmission data frame to be transmitted to another wireless communication device;
a symbol number calculation unit that calculates, for each of a plurality of preset modulation and coding schemes, a number of symbols necessary to transmit the transmission data frame based on the transmission data size and a symbol unit data size that can be included in one symbol in each of the plurality of modulation and coding schemes;
a selection unit that selects, from the plurality of types of modulation and coding schemes, a modulation and coding scheme with which the calculated number of symbols is the smallest, and, when there are a plurality of modulation and coding schemes with which the calculated number of symbols is the smallest, selects one modulation and coding scheme from the plurality of modulation and coding schemes with which the number of symbols is the smallest, excluding the modulation and coding scheme with which the symbol-unit data size is the largest;
A program to function as a

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