JP2016058913A - Wireless master device, wireless slave device, wireless communication system, and wireless communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve use efficiency of a wireless channel.SOLUTION: A master station 1 comprises: a primary buffer 11 serving as an acquisition unit for acquiring a data packet including addresses of a plurality of slave stations 2; a creation unit 13 for creating, on the basis of the data packet, a plurality of wireless frames to be transmitted to the plurality of slave stations 2; a carrier sense unit 14 serving as a determination unit for performing carrier sense in a plurality of wireless channels by which the plurality of wireless frames are to be transmitted and which differ from each other to determine the propriety of transmitting the wireless frames; and a transmission unit 15 for transmitting the plurality of wireless frames by using a plurality of wireless channels determined to be capable of transmitting the wireless frames by the carrier sense unit 14 at timing not overlapping with timing of receiving a response from a wireless slave station in any of the plurality of wireless channels.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wireless master station device capable of communicating with a plurality of wireless slave station devices, a wireless slave station device, a wireless communication system including the wireless master station device and a plurality of wireless slave station devices, and a wireless communication method.

  Conventionally, wireless LANs that can transmit and receive data via wireless lines have been widely used. In a wireless LAN, text data, between an access point (hereinafter referred to as a master station) connected to a communication line such as the Internet and a data processing device (hereinafter referred to as a slave station) such as a computer, a smartphone, and a tablet, Various data such as image data and audio data can be transmitted and received.

  In a wireless LAN, radio communication is performed while sharing a radio wave environment with other radio systems installed in the vicinity, and thus radio wave interference may occur. Therefore, a wireless system using carrier sense is known as one mechanism for mitigating radio wave interference. Non-Patent Document 1 describes a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) system as an autonomous distributed access control system. Patent Document 1 discloses a technique for performing data communication simultaneously with a plurality of slave stations while preventing mutual interference by spatial multiplexing.

JP 2005-94337 A

“IEEE 802.11 wireless LAN MAC layer technology”, [online], [searched on September 1, 2014], Internet (URL: http://www.cqpub.co.jp/interface/toku/2003/ 200302 / toku3.htm)

  According to the conventional CSMA / CA method, each wireless device performs carrier sense when attempting to transmit radio waves, and confirms that the wireless channel is not being used (hereinafter referred to as an idle state). . Then, when another wireless device uses the wireless channel, the wireless device waits until the wireless device that is transmitting the radio wave finishes transmitting the radio wave. The wireless device waits for a certain time (IFS (Inter Frame Space) time) when the wireless channel becomes idle. The radio device further performs carrier sense after an indefinite length of back-off time has elapsed, confirms that the radio channel is in an idle state, and then starts transmitting radio waves.

  However, when the number of slave stations with which the master station communicates is large, the overhead associated with the communication procedure required to start the transmission of radio waves is large with respect to the time required for data transmission to each slave station, and the effective transmission rate is high. There was a problem of lowering. For example, when 50 bytes of data are transmitted at a transmission rate of 433 Mbps defined in the IEEE 802.11ac system, the transmission time of the data itself is 50 × 8 ÷ 433 = about 0.9 (μs). On the other hand, the transmission required time of the PHY header and the MAC (Media Access Control) header is 44 + 28 × 8 ÷ 433 + 0.9 = about 45.4 (μs), which is 50 times or more the transmission required time of the data itself. .

  Considering the random access waiting time, the time required to transmit one data frame is: DIFS time + data frame transmission time + SIFS time + ACK frame transmission time = 34 + 45.4 + 16 + (44 + 14 × 8 ÷ 433) = 139. 7 (μs). Note that the indefinite length of back-off time is not considered here. The overhead when the master station sends data to the four slave stations is 139.7 × 4-0.9 = 557.9 (μs) in consideration of the waiting time for transmission to other slave stations. Thus, a waiting time of about 620 times as long as the required transmission time of the data itself is required. It should be noted that DIFS (DCF Inter Frame Space) time is a time for a radio to wait before transmitting a data frame, and SIFS (Short Inter Frame Space) time is for a radio that has received data to transmit an ACK frame. It is time to wait before.

  According to the technique described in Patent Document 1, interference of radio waves can be suppressed by spatial multiplexing using an antenna beam forming technique. However, in order to direct the antenna beam to the partner terminal that transmits data, overhead is caused by exchanging control signals in advance. Further, since spatial multiplexing cannot be performed in the direction in which the slave station transmits the ACK frame, a control signal for adjusting the transmission timing of the ACK frame of each slave station is further required. These overheads are 1646 (μs), and the time required for data transmission including exchange of control signals is 1600 times or more of 0.9 (μs), which is the time required for transmission of data itself. As described above, when the conventional method is used, it is difficult to efficiently use the radio channel, and the effective transmission rate cannot be improved.

  Therefore, the present invention has been made in view of these points, and an object thereof is to improve the use efficiency of a radio channel.

  In the first aspect of the present invention, a wireless master station device that wirelessly transmits data to a plurality of wireless slave station devices, the acquisition unit acquiring data packets including addresses of the plurality of wireless slave station devices; Generating a plurality of radio frames to be transmitted to a plurality of radio slave station devices based on the data packet, and performing carrier sense in a plurality of different radio channels for transmitting the plurality of radio frames, A determination unit configured to determine whether or not to transmit a radio frame; and the plurality of radio channels determined by the determination unit to be capable of transmitting the radio frame, from the radio slave station device in any of the plurality of radio channels. Provided is a wireless master station device comprising: a transmission unit that transmits the plurality of wireless frames at a timing that does not overlap a response reception timing That.

  The generating unit is configured to transmit the plurality of radio frames at a timing that does not overlap a timing at which a response from the radio slave station apparatus is received on any of the plurality of radio channels. The plurality of radio frames may be generated by adjusting the transmission time length of the radio frames.

  In addition, for example, the generation unit generates the plurality of radio frames having the same transmission time length in the plurality of radio channels, and the transmission unit starts transmitting the plurality of radio frames at the same timing. The generation unit may generate the plurality of radio frames having the same transmission time length by multiple connection of the plurality of data packets. Further, the generation unit adds the additional data to at least some of the plurality of data packets transmitted to the plurality of slave station devices, thereby the plurality of radio frames having the same transmission time length. May be generated.

  Further, the generation unit changes the transmission rate of data constituting at least a part of the plurality of data packets to be transmitted to the plurality of slave station devices, whereby the transmission time length is the same. A plurality of radio frames may be generated.

  The generation unit generates the radio frame including time difference information indicating a difference between a transmission time length of each of the plurality of radio frames and a longest transmission time length among the transmission time lengths of the plurality of radio frames. May be.

  The acquisition unit may acquire a plurality of types of data packets having different priorities, and the transmission unit may transmit the plurality of radio frames including the data packets having the same priority at the same timing. . The acquisition unit includes a plurality of buffers for temporarily storing the data packets, and the generation unit stores a predetermined amount of the data packets in any of the buffers. The radio frame including the data packet thus generated may be generated.

  In the second aspect of the present invention, a slave station receiving unit that receives the plurality of radio frames transmitted through the plurality of radio channels from the radio master station device, and among the plurality of radio frames, And a wireless slave station device having an extraction unit that extracts a wireless frame including the address of the wireless slave station.

  According to a third aspect of the present invention, there is provided a radio communication system comprising a radio master station device and a plurality of radio slave station devices capable of radio communication with the radio master station device, wherein the radio master station device An acquisition unit that acquires data packets including addresses of a plurality of wireless slave station devices, a generation unit that generates a plurality of wireless frames to be transmitted to the plurality of wireless slave station devices based on the data packets, and the plurality of wireless devices A determination unit that performs carrier sense in a plurality of different radio channels that transmit frames, and determines whether the radio frame can be transmitted, and the plurality of radio channels that the determination unit determines to be able to transmit the radio frame The plurality of radios at a timing that does not overlap with a timing at which a response from the radio slave station device is received on any of the plurality of radio channels. Each of the plurality of wireless slave station devices includes a slave station receiver that receives the plurality of wireless frames transmitted through the plurality of wireless channels, and the plurality of wireless slave stations. There is provided a radio communication system having an extraction unit that extracts a radio frame including its own address from a frame.

  The transmission unit of the wireless master station device includes time difference information indicating a difference between a transmission time length of each of the plurality of wireless frames and a longest transmission time length among transmission time lengths of the plurality of wireless frames. The radio slave station device transmits the radio frame, and after the time based on the time difference information included in the radio frame has elapsed after the extraction unit has extracted the radio frame, the radio slave station device normally receives the radio frame. You may further have a sub_station | mobile_unit transmission part which transmits the radio | wireless frame containing the confirmation response information which shows having performed.

  According to a fourth aspect of the present invention, there is provided a wireless transmission method for wirelessly transmitting data to a plurality of wireless slave station devices, the step of obtaining a data packet including addresses of the plurality of wireless slave station devices, Based on the data packet, generating a plurality of radio frames to be transmitted to a plurality of radio slave station devices, performing carrier sense in a plurality of different radio channels for transmitting the plurality of radio frames, A response from the wireless slave station device is received in any of the plurality of radio channels in the plurality of radio channels determined to be able to transmit the radio frame in the determining step and the determining step. Transmitting the plurality of radio frames at a timing that does not overlap with the timing to perform, To provide a radio transmission method for.

  According to the present invention, it is possible to improve the use efficiency of a radio channel.

It is a figure which shows the structure of the radio | wireless communications system which concerns on 1st Embodiment. It is a figure which shows the mode of data transmission / reception typically. It is a figure which shows the structure of the main | base station which concerns on 1st Embodiment. It is a figure which shows the structure of the subunit | mobile_unit which concerns on 1st Embodiment. It is a figure which shows the adjustment method of the radio | wireless frame length in a frame production | generation part. It is a figure which shows the method of adjusting the transmission time length of a radio | wireless frame by changing a transmission rate. It is a figure which shows the other adjustment method of the transmission time length of a radio | wireless frame. It is a figure which shows the other adjustment method of the transmission time length of a radio | wireless frame. It is a figure which shows the structure of the main | base station which concerns on 2nd Embodiment. It is a figure which shows the structure of the main | base station which concerns on 3rd Embodiment.

<First Embodiment>
[Overview of this embodiment]
FIG. 1 is a diagram illustrating a configuration of a wireless communication system S according to the first embodiment. The radio communication system S includes a master station 1 and a plurality of slave stations 2 (2a, 2b, 2c, 2d). The master station 1 is a wireless LAN access point, and can transmit and receive data to and from a plurality of slave stations 2 using a radio channel of a predetermined frequency band. The slave station 2 is a communication terminal such as a computer, a smartphone, or a tablet.

  The master station 1 can transmit and receive data to and from the plurality of slave stations 2 simultaneously using a plurality of radio channels having different frequencies. In the present embodiment, the plurality of radio channels are F1, F2, F3, and F4. Each radio channel is assigned to a frequency band obtained by dividing a frequency band that can be used by the master station 1 and the plurality of slave stations 2. When the frequency band that can be used by the master station 1 and the plurality of slave stations 2 is 80 MHz, the frequency band of each radio channel is 20 MHz.

  FIG. 2 is a diagram schematically showing a state of data transmission / reception when the master station 1 and the plurality of slave stations 2 communicate simultaneously. The master station 1 transmits a radio frame with a predetermined header attached to data to be transmitted. The radio frame includes a data frame including data to be transmitted and an ACK frame for responding that the data frame has been received. In this specification, when a matter common to the data frame and the ACK frame is described, it is referred to as a radio frame, and when a matter different between the data frame and the ACK frame is described, a “data frame”, “ It may be used separately from “ACK frame”.

  The master station 1 confirms that each radio channel is idle during the DIFS time before transmitting the radio frame. The master station 1 transmits a radio frame in each of the radio channels F1, F2, F3, and F4 after the DIFS time and the backoff time have elapsed. Each wireless frame may be addressed to a different slave station 2 or may be addressed to the same slave station 2. Here, the length of time for which the master station 1 transmits the radio frame is controlled so as to be substantially the same regardless of the radio channel. Details of the method for controlling the transmission time length of the radio frame will be described later.

  When the slave station 2 receives the radio frame transmitted by the master station 1, the slave station 2 extracts a radio frame addressed to the slave station from the received radio frame. The slave station 2 transmits an ACK frame to the master station 1 when the received radio frame is a data frame addressed to the slave station 2. The slave station 2 waits before transmitting the ACK frame, and transmits the ACK frame after the SIFS time has elapsed.

In the present embodiment, the transmission time lengths of the plurality of radio frames transmitted by the master station 1 are substantially the same, so the timings at which each slave station 2 starts transmitting the ACK frame is substantially the same. Therefore, as shown in FIG. 2, the timing at which the plurality of slave stations 2 transmit ACK frames does not overlap with the timing at which the master station 1 attempts to transmit radio frames. As a result, in the wireless communication system S, reception / demodulation of the ACK frame is caused by radio wave interference between transmission and reception by receiving the ACK frame on the adjacent wireless channel at the timing when the master station 1 transmits the wireless frame. Can be prevented. Therefore, the radio communication system S can improve the use efficiency of the radio channel when the master station 1 transmits and receives data simultaneously with the plurality of slave stations 2.
Hereinafter, the configuration and operation of the master station 1 and the slave station 2 will be described in detail.

[Configuration of master station 1]
FIG. 3 is a diagram illustrating a configuration of the master station 1. The master station 1 includes a control unit 10, a primary buffer 11, a secondary buffer 12, a generation unit 13, a carrier sense unit 14, a transmission unit 15, a reception unit 16, a restoration unit 17, and data generation. A unit 18, a buffer 19, and a parallel / serial converter 20.

  The control unit 10 is a CPU, for example. The control unit 10 controls each unit of the master station 1. The control unit 10 manages the transmission rate when data is transmitted to the plurality of slave stations 2 in association with the slave station 2. For example, the control unit 10 refers to a memory (not shown) in which information about a transmission rate that can be used by the slave station 2 is stored, and instructs the generation unit 13 of a transmission rate to be used.

  The primary buffer 11 acquires a data packet sequence to be transmitted to the slave station 2 and distributes the data packet according to the destination of the data packet based on the control of the control unit 10. The data packet is, for example, an IP frame including the IP address of any slave station 2. The primary buffer 11 acquires a plurality of data packets including the address of the slave station 2 and, based on the address included in each data packet, of the plurality of buffer memories included in the secondary buffer 12 Store the data packet in the corresponding buffer memory.

  The secondary buffer 12 has a plurality of buffer memories corresponding to each of a plurality of radio channels, and after temporarily storing data packets input from the primary buffer 11 based on the control of the control unit 10, The data is output to the generation unit 13. The secondary buffer 12 temporarily stores the data packet input from the primary buffer 11 after the data frame including the data packet output immediately before to the generation unit 13 is transmitted. The secondary buffer 12 outputs the data packet to the generation unit 13 in preparation for the case where the data frame needs to be retransmitted, and then completes transmission of the data packet to the slave station 2. The data packet is stored until an ACK frame is received.

  The generation unit 13 generates a plurality of radio frames to be transmitted to the plurality of slave stations 2 based on the data packet. The generation unit 13 includes a plurality of frame generation units corresponding to the plurality of radio channels. Each of the plurality of frame generation units included in the generation unit 13 adds a predetermined wireless header to the data packet output from the corresponding buffer memory included in the secondary buffer 12. The radio header includes a preamble used by the slave station 2 to acquire synchronization, and information for the slave station 2 to specify a transmission rate during transmission of data included in the radio frame.

  The generation unit 13 generates a plurality of radio frames having substantially the same transmission time length by adding additional data to at least some of the plurality of data packets transmitted to the plurality of slave stations 2. Specifically, the generation unit 13 obtains a transmission rate for transmitting a radio frame to the slave station 2 from the control unit 10, and a time required for transmitting the radio frame with the radio header added at the transmission rate ( Hereinafter, the transmission time length is calculated. The generation unit 13 calculates a transmission time length for each of the plurality of radio channels and specifies the maximum transmission time length (Tmax). The generation unit 13 adds the additional data to the data transmitted on the radio channel whose transmission time length is smaller than Tmax, so that the transmission time lengths of the radio frames transmitted on all the radio channels become substantially the same. The transmission time length of the radio frame is within a range that does not overlap with the timing of receiving the ACK frame as a response from the slave station 2 in any of the plurality of radio channels while transmitting the radio frame until Tmax elapses. It may be a different length.

  FIG. 5 is a diagram illustrating a method of adjusting the radio frame length in the generation unit 13. FIG. 5A shows a data frame corresponding to each radio channel before the radio frame length is adjusted. The transmission time length of the data frame corresponding to the wireless channel F1 is the longest, and the transmission time length of the data frame corresponding to the wireless channel F2 is the shortest. When each data frame is transmitted in this state, an ACK frame may be transmitted from the slave station 2 in the radio channel F2 while the master station 1 is transmitting the data frame in the radio channel F1. As described above, when the transmission timing of the data frame and the transmission timing of the ACK frame in a plurality of radio channels are asynchronous, the master station 1 may not complete the transmission of the data frame and the ACK frame may arrive at the timing. There is a disadvantage that the ACK frame cannot be received / decoded due to radio wave interference between transmission and reception in the adjacent channel.

  FIG. 5B shows a state in which the transmission time lengths of the data frames corresponding to the respective radio channels are the same by adding the additional data (PAD). As described above, the generation unit 13 makes the transmission time length of the data frame the same, thereby avoiding the inconvenience that the ACK frame arrives at the timing when the master station 1 has not completed the transmission of the data frame. .

  Returning to FIG. 3, the carrier sense unit 14 will be described. The carrier sense unit 14 is a determination unit that performs carrier sense in a plurality of different radio channels that transmit radio frames and determines whether or not radio frames can be transmitted. The carrier sense unit 14 uses a carrier detection unit (CS unit in FIG. 3) provided corresponding to each radio channel to measure the signal level observed in the corresponding radio channel before transmitting the radio frame. To do.

  When the signal level is continuously lower than the predetermined value until the DIFS time elapses, the carrier sense unit 14 allows the transmission unit 15 to transmit a radio frame on the radio channel. When the carrier sense unit 14 detects a signal level equal to or higher than a predetermined value in any of the radio channels before the DIFS time elapses, the carrier sense unit 14 sets the back-off time timer of the radio channel to the maximum value, Wait until the backoff time has elapsed. When the carrier sense unit 14 no longer detects a carrier after the back-off time has elapsed, the carrier sense unit 14 causes the generation unit 13 to transmit a radio frame. When the carrier sense unit 14 detects a carrier even after a predetermined time has elapsed, the carrier sense unit 14 causes the generation unit 13 not to transmit a radio frame until the next transmission timing.

  The transmission unit 15 includes a modulation circuit that modulates a wireless frame to be transmitted, and a high-frequency circuit (transmission side) corresponding to a plurality of wireless channels. The transmission unit 15 finishes the carrier sense in the carrier sense unit 14, and the plurality of radio frames generated by the generation unit 13 in the plurality of radio channels determined by the carrier sense unit 14 to be able to transmit the radio frame, Transmission is performed at a timing that does not overlap with the timing of receiving an ACK frame (response) from the slave station 2 in any of the plurality of radio channels.

  For example, the transmission unit 15 transmits a plurality of radio frames generated by the generation unit 13 at substantially the same timing. When the transmission time lengths of the data frames transmitted in the respective radio channels are substantially the same, the transmission unit 15 starts transmitting the data frame at approximately the same timing, so that the transmission of the data frame is performed at approximately the same timing. finish. As a result, it is possible to avoid the inconvenience that the ACK frame arrives at the timing when the master station 1 has not completed transmission of the data frame.

  In addition, when the transmission time lengths of the data frames transmitted through the respective radio channels are not substantially the same, the transmission unit 15 matches the timing at which the transmission of the data frame is completed through the respective radio channels, so that the master station 1 The inconvenience of arrival of an ACK frame at a timing when transmission is not completed may be avoided.

Next, the configuration on the receiving side in the master station 1 will be described.
The receiving unit 16 includes a high-frequency circuit (receiving side) corresponding to a plurality of radio channels and a demodulation circuit that demodulates received radio frames. For example, the receiving unit 16 receives ACK frames transmitted from the plurality of slave stations 2. The receiving unit 16 may receive a radio frame including a data packet transmitted from the slave station 2.

  The restoration unit 17 restores the MAC frame included in the radio frame received by the reception unit 16 and performs error checking. When the received MAC frame is normal, the restoration unit 17 analyzes the address in the MAC header included in the MAC frame, and determines whether the MAC frame is addressed to itself. If the received MAC frame is not a MAC frame addressed to itself, the restoration unit 17 discards the MAC frame. When the received MAC frame is a MAC frame addressed to itself and the MAC frame is an ACK frame, the restoration unit 17 determines that the wireless frame transmitted by the data generation unit 18 has been successfully delivered. Thus, the data packet stored in the secondary buffer 12 is deleted.

  The restoration unit 17 determines that the delivery has failed when the transmission unit 15 has not received the ACK frame after the transmission unit 15 transmits the data frame until a predetermined time elapses, and stores it in the secondary buffer 12. The data packet is retransmitted at the next transmission timing. When data is retransmitted, there is a possibility that it will fail again if it is transmitted on the same wireless channel. Therefore, the restoration unit 17 may input the data packet stored in the secondary buffer 12 to a frame generation unit different from the previous one so that the data packet can be transmitted on a radio channel different from the previous radio channel.

  When the data received from the slave station 2 is not an ACK frame, the data generation unit 18 generates an IP packet based on the received radio frame. The IP packet generated by the data generation unit 18 is input to the parallel / serial conversion unit 20 via the buffer 19, converted into serial data, and output to the subsequent functional unit.

[Configuration of slave station 2]
FIG. 4 is a diagram illustrating a configuration of the slave station 2. The slave station 2 includes a control unit 21, a generation unit 22, a carrier sense unit 23, a transmission unit 24, a reception unit 25, a restoration unit 26, a data generation unit 27, and a parallel / serial conversion unit 28. Have.

The control unit 21 is a CPU, for example. The control unit 21 controls each unit of the slave station 2.
The generation unit 22 includes a frame generation unit that generates a frame to be transmitted to the master station 1 corresponding to each of the plurality of radio channels. Each frame generation unit generates a data frame to be transmitted to the master station 1. In addition, each frame generation unit generates an ACK frame to be transmitted to the master station 1 in response to receiving a radio frame from the master station 1. When generating the ACK frame, the generation unit 22 sets the transmission source MAC address in the radio frame received from the master station 1 as the transmission destination MAC address. The generation unit 22 generates a radio frame in a frame generation unit corresponding to a radio channel that transmits a radio frame among the plurality of frame generation units.

  The carrier sense unit 23 corresponds to the carrier sense unit 14 in the master station 1 and performs carrier sense before transmitting a radio frame. The carrier sense unit 23 is provided corresponding to each radio channel, and observes the signal level in the corresponding radio channel before transmitting the radio frame. The carrier sense unit 23 has a countdown timer for setting a predetermined waiting time after the slave station 2 receives a radio frame from the master station 1. The carrier sense unit 23 waits for a time corresponding to, for example, the SIFS time after the slave station 2 receives the radio frame, and then transmits the radio frame generated by the generation unit 22 to the transmission rate specified by the control unit 21. To transmit to the transmission unit 24.

  The transmission unit 24 corresponds to the transmission unit 15 in the master station 1 and includes a modulation circuit that modulates a radio frame to be transmitted and a high-frequency circuit (transmission side) corresponding to a plurality of radio channels. The transmission unit 24 transmits the radio frame generated by the generation unit 22 in each radio channel after the carrier sense in the carrier sense unit 23 is completed.

  The receiving unit 25 corresponds to the receiving unit 16 in the master station 1 and includes a high frequency circuit (receiving side) corresponding to a plurality of radio channels and a demodulation circuit that demodulates the received radio frame. The receiving unit 25 identifies the transmission rate of the radio frame by analyzing the radio header after capturing synchronization based on the preamble in the received radio frame. Thereafter, the receiving unit 25 demodulates the data portion of the radio frame based on the specified transmission rate. The receiving unit 25 can demodulate a plurality of radio frames received through a plurality of radio channels in parallel.

  The restoration unit 26 restores the MAC frame included in the radio frame received by the reception unit 25 and performs error checking. The restoration unit 26 restores a MAC frame included in a plurality of radio frames received by each of a plurality of radio channels, analyzes contents of the normally received MAC frame, and extracts a MAC frame including its own address. To do. Specifically, the restoration unit 26 confirms the destination field of the MAC header, and discards the received MAC frame if the MAC frame is not addressed to itself. The restoration unit 26 outputs the MAC frame to the data generation unit 27 when the MAC frame is addressed to itself.

The data generation unit 27 deletes the MAC header from the MAC frame received from the restoration unit 26, generates an IP packet, and outputs the IP packet to the parallel / serial conversion unit 28.
The parallel / serial conversion unit 28 converts the IP packet received from the data generation unit 27 into serial data, and transfers it to a subsequent functional unit as one data stream.

[Other adjustment method 1 of radio frame transmission time length]
In the above description, the method of generating a plurality of radio frames having the same transmission time length by adding the additional data to the generation unit 13 has been described. However, the method of adjusting the radio frame transmission time length is not limited thereto. The generating unit 13 changes a plurality of data packets transmitted to the plurality of slave stations 2 by changing a transmission rate of data constituting at least some of the data packets, thereby generating a plurality of radio frames having the same transmission time length. It may be generated.

  FIG. 6 is a diagram illustrating a method of adjusting the transmission time length of a radio frame by changing the transmission rate. FIG. 6A is a diagram showing the transmission time length of a radio frame in each radio channel when the transmission rate is not changed. The wireless header is transmitted at the same transmission rate (for example, 6 Mbps), and the data is assumed to be transmitted at a different transmission rate for each wireless channel. In the wireless channel F1, data is transmitted at 6 Mbps, and the transmission time length is the maximum among the four wireless channels. In the radio channel F2, data is transmitted at 18 Mbps, and the transmission time length is the smallest among the four radio channels.

  FIG. 6B is a diagram showing the transmission time length of the radio frame in each radio channel after changing the transmission rate. In the radio channel F2, the transmission rate is changed from 18 Mbps to 6 Mbps, so that the transmission time length is the same as the radio frame transmission time length of the radio channel F1. In the radio channel F3, the transmission rate is changed from 18 Mbps to 12 Mbps, so that the transmission time length is the same as the transmission time length of the radio frame of the radio channel F1.

  The generation unit 13 may change the transmission time length by changing the transmission rate and adding the additional data described with reference to FIG. Even if the transmission rate is changed from 12 Mbps to 6 Mbps, the wireless channel F4 has a shorter transmission time length than the transmission time length in the wireless channel F1. Therefore, the generation unit 13 adds the additional data to the radio frame after changing the transmission rate, so that the transmission time length of the radio frame of the radio channel F4 is the same as the transmission time length of the radio frame of the radio channel F1. It is trying to become.

[Other adjustment method 2 of radio frame transmission time length]
FIG. 7 is a diagram illustrating another method for adjusting the transmission time length of a radio frame. As illustrated in FIG. 7, the generation unit 13 may generate a plurality of radio frames having substantially the same transmission time length by connecting a plurality of data packets and performing multiple connection.

  Specifically, the generation unit 13 acquires a plurality of data packets whose transmission destination is the same slave station 2 from the secondary buffer 12 and multiplex-links them. In FIG. 7, the generation unit 13 multiplex-connects data packets from MAC frame 1 to MAC frame n, and a wireless header is added. If the transmission time length of a radio frame generated by multiplexing a plurality of data packets is smaller than the maximum transmission time length of a radio frame of another radio channel, the generation unit 13 may add additional data. Good. By doing in this way, the generation unit 13 generates a radio frame having a transmission time length almost the same as the transmission time length of the radio frame transmitted on another radio channel even when each data packet is short. Can do.

Here, it is assumed that the time length of the radio header is t _h (μs), the size of each MAC frame including the MAC header is B _m (byte) (m is a MAC frame number), and the transmission rate is DR (Mbps). The control unit 10 determines that t _h + (B ₁ + B ₂ +... + B _n-1 ) × 8 / DR> 10000 so that the transmission time length of the radio frame is 10 milliseconds = 10000 (μs). -Select _{n that is} B _n × 8 / DR, concatenate data packets, and fill the portion that is less than 10 milliseconds with additional data, thereby reducing the transmission time length of the radio frame to 10 milliseconds. The control unit 10 performs the same processing on the buffer memory of the secondary buffer 12 assigned to each slave station 2, and generates concatenated data of the buffer memory that can align the radio frame length to 10 milliseconds. To wait until transmission is possible.

When using a wireless system in which the slave station 2 that receives the radio frame responds with an ACK frame after a predetermined waiting time (t _w ), if 10000−t _w <transmission time length ≦ 10000, the transmission time length It is not necessary to fill in the additional data with less than 10 milliseconds. In the case of a wireless LAN, t _w = 16 (μs). As a result, since the transmission of the data frame with the slowest transmission completion in the master station 1 and the reception of the ACK frame with the earliest start of reception do not overlap in time, the master station 1 uses the ACK frame as an adjacent channel. Can be received without interference between transmission and reception.

[Other adjustment method 3 of radio frame transmission time length]
FIG. 8 is a diagram illustrating another method for adjusting the transmission time length of a radio frame. As illustrated in FIG. 8, the generation unit 13 includes a radio frame including time difference information indicating a difference between each transmission time length of the plurality of radio frames and the longest transmission time length among the transmission time lengths of the plurality of radio frames. May be generated. In FIG. 8, the time difference information in the radio channel F2 is Td1, the time difference information in the radio channel F3 is Td2, and the time difference information in the radio channel F4 is Td3. The slave station 2 that has received the radio frame including the time difference information extracts the radio frame including its own address, and then transmits an ACK frame after the time based on the time difference information has elapsed. In this case, the transmission time length of the radio frame itself does not increase, but the slave station 2 does not transmit an ACK frame during the time indicated by the time difference information. Therefore, the radio frame including the time difference information can produce substantially the same effect as the radio frame changed so that the transmission time length is increased.

[Effect in the first embodiment]
As described above, in the master station 1 according to the first embodiment, the carrier sense unit 14 performs carrier sense in a plurality of different radio channels that transmit radio frames, and determines whether radio frames can be transmitted. To do. Then, the transmission unit 15 transmits a plurality of radio frames at the same timing in a plurality of radio channels determined that the carrier sense unit 14 can transmit the radio frame. By doing so, since radio frames addressed to the plurality of slave stations 2 are transmitted at the same timing in a plurality of radio channels, there is a case where data transmission to the plurality of slave stations 2 is necessary. Compared with the prior art in which data can be transmitted only to a single slave station 2 at the timing, the time utilization efficiency of the radio channel is improved.

  Specifically, in this embodiment, data packets are transmitted to the four slave stations 2 simultaneously by multiplexing in the frequency direction. When the master station 1 divides a wireless channel having a band corresponding to a transmission rate of 433 Mbps into four and transmits a data packet using an approximately 87 Mbps × 4 channel defined in the IEEE 802.11ac system, the transmission rate is The time required for one data stream of 87 Mbps to send 50 bytes of data is 50 × 8 ÷ 87 = 4.6 (μs). The required time including overhead is DIFS time + data frame transmission time + SIFS time + ACK frame reception time = 34 + (44 + 28 × 8 ÷ 87 + 4.6) +16+ (44 + 14 × 8 ÷ 87) = 146.5 (μs). Since the required time does not change even when there are data packets to be transmitted to all of the four slave stations 2, the waiting time is approximately one-quarter compared with the required time of 557.9 (μs) in the conventional method. Can be sent in time.

  As described above, the radio communication system S according to the present embodiment can reduce the communication time when communicating with a plurality of slave stations 2 and has the same throughput as when communicating with only one slave station 2. Can be maintained. Further, since the radio communication system S can reduce the occupation time of the radio space to about a quarter of the conventional time, the use of the radio space itself can be made more efficient, and the influence on the surrounding radio devices can be reduced. This is preferable in that it can be performed.

<Second Embodiment>
FIG. 9 is a diagram illustrating a configuration of the master station 1 according to the second embodiment. The secondary buffer 12 according to the first embodiment has one buffer memory corresponding to each radio channel, whereas the secondary buffer 12 according to the second embodiment has a radio that can be used. It has more buffer memory than the number of channels. Further, the master station 1 according to the second embodiment inputs data packets stored in a buffer memory larger than the number of radio channels to the frame generation unit corresponding to one of the radio channels in the generation unit 13. The point which has the selection part 30 for this also differs from 1st Embodiment.

Hereinafter, a description will be given focusing on differences from the first embodiment.
The secondary buffer 12 corresponds to each of the plurality of slave stations 2 and has a plurality of buffer memories for temporarily storing data packets. That is, the secondary buffer 12 sequentially stores data packets having the same transmission destination in one buffer memory. When the data packet with the same destination reaches the time length for configuring the radio frame scheduled for transmission, the secondary buffer 12 stores the data packet in another buffer memory. For example, when only data packets destined for the slave station 2a continue, the secondary buffer 12 sequentially stores the data packets to be transmitted to the slave station 2a in a plurality of buffer memories.

  When a predetermined amount of data packets are stored in one of the buffer memories and the number of radio packets to be transmitted can be prepared, the secondary buffer 12 transmits the data packet to the slave station 2 corresponding to the buffer memory. A radio frame to be generated is generated. Specifically, when the transmission of the radio frame generated immediately before by the generation unit 13 is completed, the secondary buffer 12 inputs to the generation unit 13 in order from the data packet in the buffer memory storing a predetermined amount or more of data packets. To do. If the generation unit 13 generates a radio frame and the carrier sense unit 14 determines that transmission is possible, the generation unit 13 transmits the radio frame. At this time, the transmission unit 15 may transmit a plurality of radio frames to the same slave station 2 (for example, the slave station 2a) using a plurality of radio channels. As described with reference to FIG. 4, the slave station 2 can simultaneously receive radio frames transmitted via a plurality of radio channels. Therefore, in this way, even when it is necessary to transmit data to many connected slave stations, the master station 1 can transmit data addressed to the slave stations ready for transmission regardless of the order. The transmission of the radio frame can be processed.

[Effects of Second Embodiment]
In the master station 1 according to the second embodiment, the secondary buffer 12 has more buffer memories than the number of radio channels. In this way, when data packets flow from the primary buffer 11 in a random order when connected to many slave stations, the data in the secondary buffer 12 ready for transmission is sequentially transmitted. Thus, it is possible to process radio frame transmissions to many slave stations 2 regardless of the arrival order of data from the primary buffer 11.

<Third Embodiment>
FIG. 10 is a diagram illustrating a configuration of the master station 1 according to the third embodiment. The master station 1 according to the first embodiment assembles and transmits a radio frame in the order in which the primary buffer 11 acquires the data packet regardless of the type of the data packet. The master station 1 is different in that the priority of transmitting a radio frame is controlled according to the type of data packet. Here, the type of data packet is determined based on, for example, the necessity of real-time property of data included in the data packet, and the priority is higher in the order of audio>video>image> text.

  As shown in FIG. 10, the primary buffer 11 includes a distribution unit 111 and a plurality of transmission queues 112 (112a, 112b, 112c). The master station 1 also has a plurality of secondary buffers 12 (12a, 12b, 12c) corresponding to the respective transmission queues 112.

  The distribution unit 111 acquires a plurality of types of data packets having different priorities, and distributes each data packet to one of the plurality of transmission queues 112 based on the priority types of the acquired data packets. For example, the transmission queue 112a is an audio memory, the transmission queue 112b is a video memory, and the transmission queue 112c is an image memory. The data packet distributed to each transmission queue 112 is input to the corresponding secondary buffer 12.

  When the transmission of the radio frame is completed, the control unit 10 checks which secondary buffer 12 among the plurality of secondary buffers 12 stores the data packet. When data packets are stored in the plurality of secondary buffers 12, the control unit 10 reads out the data packets stored in the secondary buffer 12 having a higher priority and inputs the data packets to the generation unit 13. Here, the control unit 10 generates data packets in other secondary buffers 12 even when some of the buffer memories included in the secondary buffer 12 from which the data packets have been read are empty. 13 is not written. In this way, the generation unit 13 can generate a plurality of radio frames corresponding to data packets having the same priority, so that the carrier sense unit 14 responds to the priority of the data packet to be transmitted during carrier sense. Back-off time can be used.

  When the carrier sense unit 14 determines that the radio channel to transmit the radio frame is in an idle state, the transmission unit 15 transmits a plurality of data frames including data packets with the same priority at the same timing.

  In the above description, an example in which the master station 1 has a plurality of secondary buffers 12 (12a, 12b, 12c) associated with the priority of the data packet has been described. However, the present invention is not limited to this. The master station 1 may have a plurality of buffer memories that are not associated with the priority of the data packet, like the secondary buffer 12 according to the second embodiment shown in FIG. In this case, when the control unit 10 inputs the data packet having the highest priority among the data packets stored in any of the buffer memories to the generation unit 13, the control unit 10 stores the same priority stored in the other buffer memory. Are also input to the generation unit 13. In this way, the master station 1 can transmit a plurality of data frames including data packets having the same priority at the same timing.

[Effect in the third embodiment]
The master station 1 according to the third embodiment can simultaneously transmit high priority data packets in a plurality of radio frames. Therefore, the master station 1 can preferentially transmit data that has a large influence on quality due to data interruption, such as audio and video.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. In particular, the specific embodiments of the distribution / integration of the devices are not limited to those illustrated above, and all or a part thereof may be added in arbitrary units according to various additions or according to functional loads. It can be configured functionally or physically distributed and integrated. For example, other multiplexing techniques such as a spatial multiplexing technique may be applied to the wireless communication system S.

DESCRIPTION OF SYMBOLS 1 Master station 2 Slave station 10 Control part 11 Primary buffer 12 Secondary buffer 13 Generation part 14 Carrier sense part 15 Transmission part 16 Reception part 17 Restoration part 18 Data generation part 19 Buffer 20 Parallel / serial conversion part 21 Control part 22 Generation Unit 23 carrier sense unit 24 transmission unit 25 reception unit 26 restoration unit 27 data generation unit 28 parallel / serial conversion unit 30 selection unit 111 distribution unit 112 transmission queue

Claims (13)

A wireless master station device that wirelessly transmits data to a plurality of wireless slave station devices,
An acquisition unit for acquiring a data packet including addresses of the plurality of wireless slave station devices;
Based on the data packet, a generator that generates a plurality of radio frames to be transmitted to a plurality of radio slave station devices;
A determination unit that performs carrier sense in a plurality of different radio channels that transmit the plurality of radio frames, and determines whether the radio frame can be transmitted;
In the plurality of radio channels determined by the determination unit to be able to transmit the radio frame, the plurality of radio channels at a timing that does not overlap with a timing of receiving a response from the radio slave station device in any of the plurality of radio channels. A transmission unit for transmitting a radio frame of
A wireless master station device. The generating unit is configured to transmit the plurality of radio frames at a timing that does not overlap a timing at which a response from the radio slave station apparatus is received on any of the plurality of radio channels. Generating the plurality of radio frames by adjusting the transmission time length of the radio frames of
The wireless master station device according to claim 1. The generation unit generates the plurality of radio frames having the same transmission time length in the plurality of radio channels,
The transmitting unit starts transmitting the plurality of radio frames at the same timing;
The wireless master station device according to claim 2. The generation unit generates the plurality of radio frames having the same transmission time length by multiple connection of the plurality of data packets.
The wireless master station device according to claim 3. The generation unit generates the plurality of radio frames having the same transmission time length by adding additional data to at least some of the plurality of data packets transmitted to the plurality of slave station devices. To
The radio | wireless master station apparatus of Claim 3 or 4. The generation unit changes the transmission rate of data constituting at least a part of the plurality of data packets to be transmitted to the plurality of slave station devices, whereby the plurality of transmission time lengths are the same. Generate radio frames,
The radio | wireless master station apparatus of any one of Claim 3 to 5. The generation unit generates the radio frame including time difference information indicating a difference between a transmission time length of each of the plurality of radio frames and a longest transmission time length among transmission time lengths of the plurality of radio frames.
The radio | wireless master station apparatus of any one of Claim 1 to 6. The acquisition unit acquires a plurality of types of the data packets having different priorities,
The transmitter transmits the plurality of radio frames including the data packets having the same priority at the same timing;
The radio | wireless master station apparatus of any one of Claim 1 to 7. The acquisition unit has a plurality of buffers for temporarily storing the data packets,
When the predetermined amount of the data packet is stored in any of the buffers, the generation unit generates the radio frame including the data packet stored in the buffer.
The radio | wireless master station apparatus of any one of Claim 1 to 8. A slave station receiver that receives the plurality of radio frames transmitted by the plurality of radio channels from the radio master station device according to any one of claims 1 to 9,
An extracting unit that extracts a radio frame including its own address from the plurality of radio frames;
A wireless slave station device. A wireless communication system comprising a wireless master station device and a plurality of wireless slave station devices capable of wireless communication with the wireless master station device,
The wireless master station device
An acquisition unit for acquiring a data packet including addresses of the plurality of wireless slave station devices;
Based on the data packet, a generator that generates a plurality of radio frames to be transmitted to a plurality of radio slave station devices;
A determination unit that performs carrier sense in a plurality of different radio channels that transmit the plurality of radio frames, and determines whether the radio frame can be transmitted;
In the plurality of radio channels determined by the determination unit to be able to transmit the radio frame, the plurality of radio channels at a timing that does not overlap with a timing of receiving a response from the radio slave station device in any of the plurality of radio channels. A transmission unit for transmitting a radio frame of
Have
Each of the plurality of wireless slave station devices is
A slave station receiver that receives the plurality of radio frames transmitted through the plurality of radio channels;
An extracting unit that extracts a radio frame including its own address from the plurality of radio frames;
A wireless communication system. The transmission unit of the wireless master station device includes time difference information indicating a difference between a transmission time length of each of the plurality of wireless frames and a longest transmission time length among transmission time lengths of the plurality of wireless frames. Send radio frames,
The wireless slave station device confirms that the wireless frame has been normally received after a time based on the time difference information included in the wireless frame has elapsed since the extraction unit extracted the wireless frame. A slave station transmitter that transmits a radio frame including information;
The wireless communication system according to claim 11. A wireless transmission method for wirelessly transmitting data to a plurality of wireless slave station devices,
Obtaining a data packet including addresses of the plurality of wireless slave station devices;
Generating a plurality of radio frames to be transmitted to a plurality of radio slave station devices based on the data packet;
Performing carrier sense in a plurality of different radio channels for transmitting the plurality of radio frames, and determining whether the radio frame can be transmitted;
In the plurality of wireless channels determined to be able to transmit the wireless frame in the determining step, the timing is not overlapped with the timing of receiving a response from the wireless slave station device in any of the plurality of wireless channels. Transmitting a plurality of radio frames;
A wireless transmission method comprising:

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