JP4786970B2 - Real-time signal priority method in wireless LAN and access point in wireless LAN - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To send a beacon frame and a sound signal which are desired to be sent at a regular sending time, more preferentially than a general data in a wireless LAN. <P>SOLUTION: Even if an AP receives an RTS signal which means a long packet length just prior to the regular sending time, the AP does not respond to a CTS, does not permit the long packet to be sent, sends a dummy signal just prior to the regular sending time further, and controls sending the data from other wireless LAN terminal. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a wireless communication system such as a wireless LAN (Local Area Network), and in particular, a real-time signal such as a voice signal or transmission from an access point (hereinafter, also referred to as AP) to a wireless LAN terminal in a power saving mode. The present invention relates to a method for preferentially transmitting a beacon frame that periodically notifies the presence or absence of data to be transmitted at a predetermined time.

  In recent years, wireless LANs have become widespread as one of computer communication networks, and are actively used in offices, homes, urban areas (for example, stations, airports, fast food restaurants) and the like. As is well known, in such a wireless LAN, wireless communication is performed between a wireless LAN connection device called an access point and a wireless LAN terminal. In many wireless LANs, IEEE (Institute of Electrical and Electronics Engineers) 802.11, which is one of the international standards, is used as a data link layer protocol, and IP (Internet Protocol) is used as a network layer protocol. ) Is used.

Regarding the wireless LAN, the following is known.
(1) Information to be transmitted wirelessly includes a data signal such as a PC and a real time signal such as voice. Control signals for smoothing these information transmissions, beacon frames that periodically notify the start / end of connection between the wireless LAN terminal and the AP, and the existence of data to be transmitted to the wireless LAN terminal in the power saving mode, etc. It is also known that there is a management signal.
(2) In radio, transmission errors often occur due to noise on the transmitted signal due to characteristics of the transmission medium and interference between a plurality of radio signals having different transmission paths. Therefore, in the wireless LAN, the influence of transmission errors is reduced by the following error retransmission. That is, a header indicating a destination and a signal type and a transmission error detection code are added to the signal, and the packet is transmitted as a packet. When the device (wireless LAN terminal or AP) receiving the packet receives the packet, it determines the presence or absence of a transmission error using a transmission error detection code or the like. If it is determined that the packet has been normally received without detecting a transmission error, an ACK frame is returned. If a transmission error is detected, an ACK frame is not returned. If the ACK frame is not returned, the sending device sends again the same packet as the sent packet. If a transmission error is detected even in a packet retransmitted on the receiving side and an ACK frame is not returned, the transmitting side repeats retransmission up to a predetermined number of times.
(3) If a radio is used for a long period for sending and retransmitting such packets, radio signals cannot be sent from other wireless LAN terminals or APs during that period. Further, even when the packet length itself is long, the wireless signal is used for a long period of time, so that wireless signals cannot be transmitted from other wireless LAN terminals or APs.
(4) Currently, the data transmitted by the wireless LAN is mainly data, but it is expected that the audio signal and the data will be mixed in the future. The audio signal is obtained by encoding audio, adding a header and a transmission error detection code to a packet, and sending the packet at a constant period (for example, 20 ms). Since the audio signal is a real-time signal, if the transmission time of the audio signal is delayed due to the wireless use of another device, audio delay, sound fluctuations, and sound interruptions due to packet loss occur, causing a great psychological burden on the user. It is also known that
(5) Wireless LAN terminals often operate on batteries in order to facilitate movement. When not using data or voice wireless communication to extend the battery standby time, the power saving mode is set. When there is data or a voice signal to be transmitted from the AP to the wireless LAN terminal, the AP notifies that there is a data or voice signal to be transmitted using a beacon frame that is one of the management signals. The wireless LAN terminal activates the wireless transmission / reception function only at the time when the beacon frame is received and intercepts the beacon frame. Wirelessly communicates with each other and transmits and receives data and audio signals addressed to the wireless LAN terminal. When there is no data or voice addressed to the own wireless LAN terminal, the wireless transmission / reception function is immediately stopped to save power.

  Due to the above (3), if the time at which the audio signal is transmitted is delayed, audio delay, sound fluctuation, and sound interruption due to packet loss occur, which is a great psychological burden on the user.

  Due to the above (4), if the time when the beacon frame is transmitted from the AP is delayed from a predetermined time, the time during which the wireless LAN terminal in the power saving mode starts the wireless transmission / reception function becomes longer, and the battery is consumed. It is also known that there is a problem that the waiting time is shortened by increasing the amount.

  Therefore, it is desired to transmit an audio signal or a beacon frame from the AP at a predetermined time in the wireless LAN. However, if a wireless signal from another device is being transmitted, an audio signal or a beacon frame cannot be transmitted even at the predetermined time. In particular, if there is retransmission of a transmission error or data having a long packet length, the data is transmitted with a delay significantly from the above-defined time.

  On the other hand, there is an interference radio wave from a microwave oven or the like that should be given higher priority than an audio signal, a beacon frame or data. In other words, the microwave oven heats food with electromagnetic waves of 2.475 GHz, which is the same frequency band as that used in wireless LAN and Bluetooth. Part of this electromagnetic wave leaks out of the microwave oven, affecting wireless LAN and Bluetooth wireless signals, making transmission impossible.

  This leakage electromagnetic wave repeats the presence or absence at a period of 5 ms or 10 ms with a 50 Hz power supply (a period of 4.2 ms or 8.3 ms with a 60 Hz power supply). Therefore, wireless transmission / reception is possible in 50% of time (see, for example, Patent Document 1).

  Of course, the above-described jamming radio wave does not follow the rule that the wireless LAN presupposes, “when another device is transmitting radio, it does not transmit radio from itself”. When competing with jamming, the following problems can occur.

  When a wireless LAN terminal or AP starts sending long packets and if all long packets become invalid due to transmission errors, wireless transmission and reception is possible from the start of sending long packets until the start of jamming. Time is consumed ineffectively.

  There is a hidden terminal that is visible to the AP but is not affected by the jamming signal from the microwave oven. Even after the jamming signal has stopped, it starts to send long packets while the jamming signal from the microwave oven is generated. There is a case where the long packet is continuously transmitted. The packet cannot be received after all due to a transmission error, and the wireless transmission / reception available time is invalidally consumed only by the transmission time of the long packet that protrudes after the jamming wave stops.

(1) The above problem is shown by numerical examples. According to Patent Document 1, when the power source is 50 Hz, the interference radio wave of the inverter type microwave oven repeats “present” and “absent” in a cycle of 5 ms.
(2) If the data length is 2000 bytes, for example, as a long packet, and the preamble and radio header are combined with this data and transmitted at a transmission rate of 11 Mbit / s, the total packet length is 1.7 ms.
(3) Therefore, when this long packet is transmitted / received 1.7 ms before the start of “presence” of the jamming radio wave and immediately before the start of “non-existence”, the time during which a radio signal can be effectively transmitted / received is at least 5 ms−1. .7 ms-1.7 ms = 1.6 ms.
(4) Therefore, it is necessary for the wireless LAN to perform wireless transmission control in order to minimize the influence of jamming radio waves.

  In view of the above problems, the present invention eliminates a significant delay in the time for outputting a beacon frame from an AP to a wireless LAN terminal in a wireless LAN composed of a plurality of wireless LAN terminals connected via an access point (AP). It is an object of the present invention to reduce the waiting time for the wireless LAN terminal to receive a beacon frame to prevent unnecessary battery consumption.

  That is, an object of the present invention is to reduce the power consumption when a wireless LAN terminal is waiting for a beacon frame in a wireless LAN composed of a plurality of wireless LAN terminals connected via an AP, bringing the beacon frame transmission time closer to the scheduled time. There is.

  Another object of the present invention is to ensure voice quality in a wireless LAN including a plurality of wireless LAN terminals connected via an AP.

  Furthermore, another object of the present invention is to provide a system capable of giving priority to beacon frame transmission and voice communication over data transmission in a wireless LAN composed of a plurality of wireless LAN terminals connected via an AP. is there.

In addition, another object of the present invention is to provide a system capable of avoiding communication failure due to leakage electromagnetic waves such as a microwave oven in a wireless LAN composed of a plurality of wireless LAN terminals connected via an AP.
JP 2002-319946 A

In order to solve the above-described problems, the present invention provides an access point in a wireless LAN system including an access point and a plurality of wireless LAN terminals connected to the access point via a wireless LAN. From the wireless LAN terminal, a time measuring means for measuring a fixed time for transmitting an audio signal or a beacon, a signal transmitting means for preferentially transmitting the audio signal or beacon at a fixed time for transmitting the audio signal or beacon, and the wireless LAN terminal The time when the maximum duration time described in the RTS has elapsed from the current time when the RTS (Request To Send: transmission permission request) transmission prior to data transmission is received is before the scheduled time at which the audio signal or beacon is transmitted. Data receiving end time judging means for judging whether or not The means is a means for preferentially transmitting the audio signal or beacon when the time at which the maximum duration time described in the RTS has elapsed from the current time is not before the scheduled time for transmitting the audio signal or beacon. characterized in that there.

In the present invention, when the RTS transmission prior to data transmission is received from the wireless LAN terminal, the time when the maximum duration described in the RTS has elapsed from the current time is earlier than the scheduled time at which the voice signal or beacon is transmitted. Data reception end time determination means for determining whether or not
The signal transmission means preferentially transmits the audio signal or beacon when the time when the maximum duration time described in the RTS has elapsed from the current time is not before the scheduled time for transmitting the audio signal or beacon. Then, when RTS is received again from the wireless LAN terminal, CTS (Clear To Send: transmission permission) is transmitted to the wireless LAN terminal .

In the present invention, when the RTS transmission prior to data transmission is received from the wireless LAN terminal, the time when the maximum duration described in the RTS has elapsed from the current time is earlier than the scheduled time at which the voice signal or beacon is transmitted. Data reception end time determination means for determining whether or not
When the received data with the RTS is abnormal, the signal transmission means determines that the time when the maximum duration time described in the RTS has elapsed from the current time of the data to be retransmitted is the audio signal or beacon. It is a means for sending a dummy signal that ends before the scheduled time for sending the audio signal or beacon when it is not before the scheduled time for sending .

In the present invention, when data transmission is received from the wireless LAN terminal, it is determined whether or not the time when the maximum duration time without RTS has elapsed from the current time is before the scheduled time for transmitting the voice signal or beacon. A data reception end time determination means for performing the voice reception when the time when the maximum duration time without RTS has elapsed from the current time is not before the scheduled time for sending the voice signal or beacon. It is a means for sending a dummy signal that ends before the scheduled time for sending a signal or a beacon .

  According to the present invention, in a wireless LAN composed of a plurality of wireless LAN terminals connected via an access point (AP), the beacon frame transmission time is brought close to the scheduled time, and the power consumption of the wireless LAN terminal when waiting for the beacon frame is reduced. Can be reduced.

  According to the present invention, in a wireless LAN composed of a plurality of wireless LAN terminals connected via an AP, the beacon frame transmission time can be brought close to the scheduled time, and the power consumption of the wireless LAN terminal when waiting for the beacon frame can be reduced. it can.

  ADVANTAGE OF THE INVENTION According to this invention, the quality of an audio | voice can be ensured in the wireless LAN which consists of a some wireless LAN terminal connected via AP.

  According to the present invention, transmission of a beacon frame and voice communication can be prioritized over data transmission in a wireless LAN including a plurality of wireless LAN terminals connected via an AP.

  ADVANTAGE OF THE INVENTION According to this invention, in the wireless LAN which consists of several wireless LAN terminal connected via AP, the failure | damage of communication by leakage electromagnetic waves, such as a microwave oven, can be avoided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram showing a computer network system configuration including a wireless LAN to which an embodiment of the present invention is applied.

  In FIG. 1, in this computer network system, a LAN 1 and a LAN 2 are connected by an IP (Internet Protocol) network 5. The LAN 1 includes wireless LAN terminals 1-1, 1-2, 1-3, access points 2-1, 2-2, personal computers 4-1, 4-2, and a router 3-1. The wireless LAN terminals 1-1, 1-2, and 1-3 are information communication terminals having a wireless LAN communication function that operate in conformity with IEEE 802.11. For example, an information processing apparatus such as a personal computer, a PDA (Personal An information terminal such as Digital Assistant) or a telephone terminal such as a wireless IP telephone performs wireless LAN communication with the access points 2-1 and 2-2.

  The access points 2-1 and 2-2 have a wireless LAN communication function that operates in conformity with IEEE 802.11 and a wired LAN communication function such as Ethernet (registered trademark) that operates in conformity with IEEE 802.3. Wireless LAN communication is performed with the LAN terminals 1-1, 1-2, and 1-3, and other communication devices (PCs 4-1, 4-2, and router 3-1) connected to the LAN 1 are also performed. Etc.) and LAN communication.

  The router 3-1 is connected to the LAN 1 and the IP network 5, and monitors IP (Internet Protocol) packets flowing on the LAN 1 and IP packets obtained from the IP network 5, and IP header information (destination) of the IP packets If it is determined that the IP packet flowing on the LAN 1 is to be routed to the IP network 5 side, this is the IP network 5 side. If the IP packet obtained from the IP network 5 is determined to be routed to the LAN 1 side, it is sent to the LAN 1 side.

  Further, the personal computers 4-1 and 4-2 have a normal wired LAN board, and are connected to the LAN 1 to transmit and receive IP packets and perform IP communication (LAN communication).

  The LAN 2 has the same configuration as the LAN 1 and includes wireless LAN terminals 1-4, 1-5, 1-6, access points 2-3, 2-4, personal computers 4-3, 4-4, and a router 3- 2. Wireless LAN terminals 1-4, 1-5, 1-6 are terminal devices having a wireless LAN communication function that operate in conformity with IEEE 802.11, and are composed of a personal computer, a PDA, a wireless IP telephone device, etc. Wireless LAN communication is performed between the points 2-3 and 2-4.

  The access points 2-3 and 2-4 have a wireless LAN communication function that operates in accordance with IEEE 802.11 and a wired LAN communication function such as Ethernet (registered trademark) that operates in accordance with IEEE 802.3. Wireless LAN communication is performed with the wireless LAN terminals 1-4, 1-5, and 1-6, and other communication devices connected to the LAN 2 (the personal computers 4-3 and 4-4 and the router 3-3 2) and the like.

  The router 3-2 is connected to the LAN 2 and the IP network 5, and monitors the IP packet flowing on the LAN 2 and the IP packet obtained from the IP network 5, and IP header information (destination IP address information and It is a communication device that routes IP packets based on port number information and the like. When it is determined that the IP packet flowing on the LAN 2 is to be routed to the IP network 5 side, this is sent to the IP network 5 side, and the IP packet obtained from the IP network 5 is to be routed to the LAN 2 side If it is determined that, it is sent to the LAN 2 side.

  Furthermore, the personal computers 4-3 and 4-4 have a normal wired LAN board, and are connected to the LAN 1 to transmit and receive IP packets and perform IP communication (LAN communication).

  With the above configuration, the wireless LAN terminals 1-1, 1-1, 1-3 on the LAN 1 side perform IP communication with other wireless LAN terminals on the LAN 1 side and the personal computers 4-1, 4-2, and routers 3-1, IP communication is performed with the wireless LAN terminals 1-4, 1-5, and 1-6 on the LAN 2 side and the personal computers 4-3 and 4-4 via the IP network 5 and the router 3-2. This is possible.

  Similarly, the wireless LAN terminals 1-4, 1-5, 1-6 on the LAN 2 side perform IP communication with other wireless LAN terminals on the LAN 2 side and the personal computers 4-3, 4-4. 2. Perform IP communication with the wireless LAN terminals 1-1, 1-2, 1-3 and the personal computers 4-1, 4-2 on the LAN 1 side via the IP network 5 and the router 3-1. It has a possible configuration.

  Next, the configuration of an access point to which the present invention is applied will be described. FIG. 2 is a block diagram showing the internal structure of the access points 2-1, 2-2, 2-3, 2-4 to which the present invention is applied.

The access point includes a router unit 2A and a radio unit 2B. The radio unit 2B includes an antenna 21, an RF (Radio Frequency) unit 22, a baseband unit 23, a MAC (Media Access Controller) layer processing unit 24, a communication processing unit 20, a program memory 20-1, a work memory, And a memory 20-2.
The RF unit 22, the baseband unit 23, and the MAC layer processing unit 24 are connected to the communication processing unit 20 via the bus 29. Then, the communication processing unit 20 includes the RF unit 22, the baseband unit 23, and the MAC layer processing unit 24 while using the work memory 20-2 according to the control program and setting data in the program memory 20-1. The entire wireless unit 2B is controlled.

  In such a configuration, the router unit 2A has an IP (Internet Protocol) address, a TCP (Transmission Control Protocol) port number, or a UDP (User Datagram Protocol) IP number including an IP packet received from the network (LAN1 or LAN2). The IP packet is routed based on a preset rule with reference to the header. An IP packet to be transmitted to the wireless unit 2B is transmitted to the MAC layer processing unit 24.

  The MAC layer processing unit 24 performs conversion processing between the data link layer of IEEE802.3 that is an Ethernet (registered trademark) standard and the data link layer of IEEE802.11 that is a wireless LAN standard.

  The baseband unit 23 modulates an IP packet subjected to MAC processing for IEEE802.11 into a baseband signal, or demodulates the baseband signal to restore the original IP packet.

  The RF unit 22 uses the baseband signal received from the baseband unit 23 according to IEEE 802.11, for example, a carrier radio frequency specified by a DS-SS (Direct Sequence Spread Spectrum) method or an FH-SS method (Frequency Hopping Spread Spectrum). Is transmitted as a radio signal from the antenna 21. On the contrary, the carrier radio frequency is removed from the radio signal received from the antenna 21 to restore the original baseband signal, which is sent to the baseband unit 23.

  Hereinafter, an operation when an IP packet is transmitted from the network (LAN 1 or LAN 2) via the antenna 21 will be described. The MAC layer processing unit 24 converts the MAC layer of the IP packet received from the network (LAN1 or LAN2) via the router unit 2A from IEEE802.3 for Ethernet (registered trademark) to IEEE802.11 for wireless, The data is sent to the baseband unit 23.

  The baseband unit 23 modulates the received IP packet in accordance with wireless IEEE 802.11, generates a baseband signal, and sends the baseband signal to the RF unit 22.

  The RF unit 22 puts the baseband signal from the baseband unit 23 on the carrier radio frequency, and transmits the wireless LAN terminal 1-1, 1-2, 1-3, 1-4, 1-5 as a radio signal from the antenna 21. Send to 1-6.

  Next, an operation when a wireless signal is received from a wireless LAN terminal will be described. When the antenna 21 receives the radio signal received from the wireless LAN terminals 1-1, 1-2, 1-3, 1-4, 1-5, and 1-6, the antenna 21 transmits the signal to the RF unit 22.

  The RF unit 22 removes the carrier radio frequency from the radio signal, restores the original baseband signal, and sends it to the baseband unit 23. The baseband unit 23 demodulates the baseband signal, restores the original IP packet, and sends it to the MAC layer processing unit 24. The MAC layer processing unit 24 converts the MAC layer of the IP packet from IEEE802.11 for wireless to IEEE802.3 for Ethernet (registered trademark), and sends it to the router unit 2A. The router unit 2A transfers the received IP packet to a LAN or the like using the IP address of the received IP packet.

  Next, the configuration of a wireless LAN terminal to which the present invention is applied will be described. FIG. 3 is a block diagram showing the internal configuration of the wireless LAN terminals 1-1, 1-2, 1-3, 1-4, 1-5, and 1-6 to which the present invention is applied.

  In FIG. 3, the wireless LAN terminal includes an information communication terminal unit 1A and a wireless unit 1B. The radio unit 1B includes an antenna 11, an RF (Radio Frequency) unit 12, a baseband unit 13, a MAC (Media Access Controller) layer processing unit 14, an upper layer processing unit 15, a terminal interface unit 16, a communication A processing unit 10, a program memory 10-1, and a work memory 10-2 are provided.

  The RF unit 12, the baseband 13, the MAC layer processing unit 14, the upper layer processing unit 15, and the terminal interface unit 16 are connected to the communication processing unit 10 via the bus 19.

  The communication processing unit 10 uses the work memory 10-2 according to the control program and setting data in the program memory 10-1, and uses the RF unit 12, the baseband processing unit 13, the MAC layer processing unit 14, The entire radio unit 1B including the layer processing unit 15 and the terminal interface unit 16 is controlled.

  The information communication terminal unit 1A is an information processing device such as a personal computer, an information terminal such as a PDA (Personal Digital Assistant), or a telephone terminal such as an IP telephone, and data and voice encoding sent from these information terminals or telephone terminals A signal is transmitted to the terminal interface unit 16, or data and a voice encoded signal from the terminal interface unit 16 are received and transmitted to the information terminal or the telephone terminal.

  In the radio unit 1B, the terminal interface unit 16 performs processing related to an interface for transferring data and speech encoded signals between the information communication terminal unit 1A and the radio unit 1B.

  The upper layer processing unit 15 performs IP packet processing related to the network layer / transport layer and transmits the packet between the network layer / transport layer, and includes an IP header including an IP address, a TCP port number, or a UDP port number. The process of giving / deleting is performed.

  The MAC layer processing unit 14 performs IP packet processing related to the data link layer, and assembles or disassembles IP packets in which data and voice bucket data are stored in accordance with IEEE 802.11, and transmits the data packets between the data link layers. MAC address assignment / deletion processing is performed.

  The baseband unit 13 modulates the IP packet to generate a baseband signal, or demodulates the baseband signal to restore the original IP packet.

  The RF unit 12 places the baseband signal received from the baseband unit 13 on the carrier radio frequency in accordance with IEEE 802.11, and transmits it from the antenna 11 as a radio signal. On the contrary, the carrier radio frequency is removed from the radio signal received from the antenna 11 to restore the baseband signal, which is then sent to the baseband unit 13.

  Next, an operation when data generated by the information communication terminal unit 1 </ b> A and a voice encoded signal are transmitted via the antenna 11 will be described. The terminal interface unit 16 sends data and a voice encoded signal from the information communication terminal unit 1 </ b> A to the upper layer processing unit 15.

  The upper layer processing unit 15 generates an IP packet by performing IP header processing such as IP address assignment / TCP / UDP port number assignment, and then sends the IP packet to the MAC layer processing unit 14.

  The MAC layer processing unit 14 subjects the IP packet from the upper layer processing unit 15 to MAC processing such as MAC address assignment according to the IEEE 802.11 processing procedure, and sends the IP packet to the baseband unit 13.

  The baseband unit 13 modulates the received IP packet according to IEEE 802.11, generates a baseband signal, and sends the baseband signal to the RF unit 12.

  The RF unit 12 places the baseband signal from the baseband unit 13 on the carrier radio frequency in accordance with IEEE 802.11, and transmits the radio signal from the antenna 11 to the access points 2-1, 2-2, 2-3 and 2-4. Send out.

  Next, an operation when a radio signal transmitted from an access point is received and output to the information communication terminal unit will be described. The antenna 11 transmits the radio signal received from the access points 2-1, 2-2, 2-3 and 2-4 to the RF unit 12.

  The RF unit 12 removes the carrier radio frequency from the received radio signal, restores it to the original baseband signal, and sends it to the baseband unit 13.

  The baseband unit 13 demodulates the received baseband signal, restores it to the original IP packet, and sends it to the MAC layer processing unit 14.

  The MAC layer processing unit 14 deletes the MAC address from the received IP packet according to IEEE 802.11, and sends the MAC address to the upper layer processing unit 15.

  The upper layer processing unit 15 deletes the TCP / UDP header and the IP header from the IP packet from the MAC layer processing unit 14 based on the setting data, and communicates the obtained data and the voice encoded signal via the terminal interface unit 16. Send to terminal unit 1A.

[Embodiment 1] Next, means for suppressing beacon frame and voice signal transmission delay due to error retransmission, which is Embodiment 1 of the present invention, will be described.

  The first embodiment is an access point that constitutes a wireless LAN system including an access point and a plurality of wireless LAN terminals connected to the access point via a wireless LAN. An audio signal or beacon is directed to the wireless LAN terminal. This is an example provided with time measuring means for measuring a fixed time for sending a frame, and signal sending means for preferentially sending the audio signal or beacon frame when the fixed time for sending the audio signal or beacon frame is reached. Also, in the first embodiment, in the access point, when the data transmitted from the wireless LAN terminal is abnormal, the signal transmission means causes the voice signal or beacon frame to be transmitted before the wireless LAN terminal retransmits the data. It is an example as a means to send out. Further, in the first embodiment, at the access point, when the signal transmission means starts transmitting data and reaches the scheduled time, even if data transmission fails, the audio signal or beacon frame is transmitted as the data signal. This is an example of means for sending with priority over retransmission.

  In order to facilitate the explanation of the present invention, a conventional transmission control time chart defined in section 9.2 of the international standard IEEE 802.11 will be described first with reference to FIG. A case where one AP and two wireless LAN terminals A and B perform wireless communication using one wireless space is taken as an example. The horizontal axis is time.

(1) First, the wireless LAN terminal A sends a Data1 signal to the AP.
(2) At the time when the AP should transmit a beacon frame while receiving Data1, the AP waits for the completion of reception of Data1 in order to avoid interference with the radio of Data1.
(3) When the reception of Data1 is completed, the AP determines whether Data1 is normal, and if normal, sends an ACK frame to the wireless LAN terminal A to notify normal reception. The AP continues to send out beacon frames. As a result, transmission of the beacon frame is delayed by a maximum of one packet from the scheduled time.

(4) Next, the wireless LAN terminal B sends Data2 to AP2.
(5) The AP receives the audio signal while receiving Data2, but waits for the completion of reception of Data2 in order to avoid interference with the radio of Data2.
(6) When the reception of Data2 is completed, the AP determines whether Data2 is normal, and if normal, sends an ACK frame to the wireless LAN terminal B to notify normal reception. The AP continues to send audio signals. As a result, the transmission of the audio signal is delayed by a maximum of one packet from the scheduled time.

Next, FIG. 16 shows a time chart when the error retransmission defined in the international standard 9.2.5.3 is added to FIG. Here, a case where a transmission error occurs in data addressed to the AP from the wireless LAN terminals A and B and the data is retransmitted will be described with reference to FIG.
(1) First, the wireless LAN terminal A sends a Data1 signal to the AP.
(2) At the time when the AP should transmit a beacon frame while receiving Data1, the AP waits for the completion of reception of Data1 in order to avoid interference with the radio of Data1.
(3) When the reception of Data1 is completed, the AP determines whether Data1 is normal, and does not return an ACK frame to the wireless LAN terminal A because it is abnormal.
(4) Since the wireless LAN terminal A cannot receive the ACK frame for Data1, it retransmits Data1.
(5) When the reception of Data1 is completed, the AP determines whether the retransmitted Data1 is normal, and if normal, returns an ACK frame to the wireless LAN terminal A to notify normal reception. The AP continues to send out beacon frames. As a result, transmission of the beacon frame is delayed by a maximum of two packets from the scheduled time.

Next, the wireless LAN terminal B sends Data2 to AP2.
(1) The AP receives a voice signal while receiving Data2, but waits for completion of reception of Data2 in order to avoid interference with the radio of Data2.
(2) When the reception of Data2 is completed, the AP determines whether Data2 is normal, and does not return an ACK frame to the wireless LAN terminal B because it is abnormal.
(3) Since the wireless LAN terminal B cannot receive the ACK frame for Data2, it retransmits Data2.
(4) Upon completion of the reception of Data2, the AP determines whether the retransmitted Data2 is normal. If the AP is normal, the AP returns an ACK frame to the wireless LAN terminal B to notify normal reception. The AP continues to send audio signals. As a result, the transmission of the audio signal is delayed by a maximum of two packets from the scheduled time.

  As described above, in the conventional method, when the AP receives data from any of the wireless LAN terminals at the beacon frame transmission scheduled time or the voice transmission time, the reception of the data is not performed. After successfully completing and transmitting the ACK frame, the beacon frame or voice is transmitted, and the transmission of the beacon frame or voice is delayed by a maximum of two packets. During this delay time, each wireless LAN terminal powers on and waits for reception of a beacon frame, leading to unnecessary power consumption. In addition, during the delay time, voice transmission from the AP is delayed, and the quality of voice communication is deteriorated.

  Next, a time chart in the case of preventing a delay due to a retransmission signal in Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 4 shows a case where a transmission error occurs in data transmitted from the wireless LAN terminals A and B to the AP. FIG. 5 shows a case where a transmission error occurs in data transmitted from the AP to the wireless LAN terminals A and B. The time chart of FIG. 4 is as follows.

(1) First, the wireless LAN terminal A sends a Data1 signal to the AP.
(29AP waits for the completion of the reception of Data1 in order to avoid interference with the radio of Data1 at the scheduled time when the beacon frame should be transmitted while receiving Data1.
(3) When the reception of Data1 is completed, the AP determines whether Data1 is normal, and does not return an ACK frame to the wireless LAN terminal A because it is abnormal. Instead, a beacon frame that is a feature of this embodiment is transmitted. As a result, transmission of the beacon frame is delayed by a maximum of one packet from the scheduled time, as in the case where there is no transmission error.
(4) The wireless LAN terminal A receives a beacon frame while waiting to receive an ACK frame for Data1. According to the above stipulations for the ACK frame of International Standard Section 9.2.8, “When receiving a signal other than the ACK frame while waiting for the ACK frame for the transmitted data, the received signal is processed, and the transmitted data is "It is determined that the message has not been sent normally". Therefore, after processing the received beacon frame, Data1 is retransmitted.
(5) The AP after sending out the beacon frame determines whether it is normal after completing the reception of the retransmitted Data1, and if normal, returns an ACK frame to the wireless LAN terminal A to notify normal reception. To do.

(6) Next, the wireless LAN terminal B sends Data2 to the AP.
(7) The AP waits for the completion of the reception of Data2 in order to avoid interference with the radio of Data2 at the scheduled time when the audio signal should be transmitted while receiving Data2.
(8) When the reception of Data2 is completed, the AP determines whether Data2 is normal, and does not return an ACK frame to the wireless LAN terminal B because it is abnormal. Instead, an audio signal which is a feature of the present embodiment is also sent here. As a result, voice transmission is delayed by a maximum of one packet from the scheduled time, as in the case where there is no transmission error.
(9) Since the wireless LAN terminal B receives the audio signal instead of the ACK frame for Data2, the wireless LAN terminal B retransmits Data2 after processing the audio signal.
(10) After completing the reception of the retransmitted Data2, the AP determines whether it is normal. If it is normal, the AP returns an ACK frame to the wireless LAN terminal B to notify normal reception.

  As described above, according to this method, when there is an error in the reception of Data1 or Data2 shown in FIG. 17, the beacon frame transmission or the voice transmission is delayed by a maximum of two packets, but is limited by a maximum of one packet. be able to.

Next, a time chart when data is transmitted from the AP to the wireless LAN terminals A and B will be described with reference to FIG.
(1) First, the AP sends a Data1 signal to the wireless LAN terminal A.
(29AP waits for the completion of the transmission of Data1 because it becomes the scheduled time when the beacon frame should be transmitted during the transmission of Data1, but cannot be transmitted simultaneously with the wireless transmission of Data1.
(3) When the reception of Data1 is completed, the wireless LAN terminal A determines whether Data1 is normal, and does not return an ACK frame to the AP because it is abnormal.
(4) The AP waits for a certain period of time to receive an ACK frame for Data1, and determines that a transmission error has occurred if reception is not possible. At that time, a beacon frame is transmitted first, and then Data1 is retransmitted. As a result, beacon frame transmission is delayed by a maximum of one packet from the scheduled time, as in the case where there is no transmission error.
(5) Since the wireless LAN terminal A does not send back an ACK frame to the first Data1, it expects retransmission of Data1, but receives a beacon frame instead, receives and processes the beacon frame, and then Wait for retransmission of Data1. When the reception of the retransmitted Data 1 is completed, the wireless LAN terminal A determines whether it is normal. If normal, the wireless LAN terminal A returns an ACK frame to the AP and notifies normal reception.

(6) Next, the AP sends a Data2 signal to the wireless LAN terminal B.
(7) The AP comes at a fixed time when the voice is to be transmitted during the transmission of Data2, but cannot wait for the simultaneous transmission of Data2, and therefore waits for the completion of the transmission of Data2.
(8) When the reception of Data2 is completed, the wireless LAN terminal B determines whether Data2 is normal, and does not return an ACK frame to the AP because it is abnormal.
(9) The AP waits for a certain period of time to receive the ACK frame for Data2, and determines that a transmission error has occurred if reception is not possible. At that time, the AP first transmits an audio signal, and then retransmits Data2. As a result, voice signal transmission is delayed by a maximum of one packet from the scheduled time, as in the case where there is no transmission error.
(10) When receiving the audio signal instead of the retransmitted Data2, the wireless LAN terminal B receives and processes the audio signal, and waits for the retransmission of Data2.
(11) When the reception of the retransmitted Data 2 is completed, the wireless LAN terminal A determines whether it is normal. If normal, the wireless LAN terminal A returns an ACK frame to the AP and notifies normal reception.

  As described above, according to this method, when the AP has a beacon frame or voice transmission time at the time of data transmission and the data transmission is abnormal, the beacon frame is transmitted before the data is retransmitted. Since transmission or voice transmission is executed, a beacon frame or voice can be transmitted within a maximum of one packet delay.

  Next, the detailed operation of each embodiment will be described with reference to a flowchart. FIG. 6 is a flowchart of the AP in the first embodiment. As shown in the upper part of FIG. 6, the AP activates a voice timer or a beacon frame timer as an initial value. Since the AP often has a voice signal transmission cycle of 20 ms, the voice timer is set to, for example, 20 ms, and the beacon frame timer is set to 102.4 ms, and is set to, for example, 102.4 ms. The AP clears FLAG indicating that the voice timer or the beacon frame timer has expired to 0 (S1).

The AP also sets a transmission timer value as an initial value. Since the transmission timer value is important as a parameter in the flowchart, it will be described first. International Standard Section 9.2.3.1 specifies that the transmission timer is used as follows in order to acquire the transmission right of the wireless LAN terminal or AP. That is, in order to acquire a transmission right with another wireless LAN terminal after reception of a certain wireless signal is completed, it is confirmed that there is no wireless signal with a predetermined waiting time, and the transmission right is confirmed after the confirmation. As a result, wireless transmission is started. As this waiting time, international standard 9.2.3.1 defines two values.
a) (DIFS + random number) period b) SIFS

  DIFS is a normal waiting time, and by adding a random number generated independently by the AP and each wireless LAN terminal, the times when the waiting time ends differ from each other, and the AP and each wireless LAN terminal simultaneously transmit radio. This reduces the probability of crosstalk.

  SIFS (Short Inter-Frame Space) is a shorter value than DIFS (Distributed Inter-Frame Space), and is used for preferential transmission because the waiting time ends earlier. For example, in order to confirm that the transmission of data or the like is normal over the radio, the data receiving side returns an ACK frame (response frame) to the transmitting side. In order to return the ACK frame preferentially, it is specified that when the data is normally received, the ACK frame is returned after the SIFS wait time.

  International Standard Section 9.2.3.1 specifies that both the AP and the wireless LAN terminal set the waiting time to (DIFS + random number). However, in practice, the waiting time is set to SIFS in order to prioritize the transmission right of the AP over the wireless LAN terminal in many applications. Therefore, here, the transmission timer is set to SIFS and the waiting time of the AP is set to SIFS. Explain the case.

(1) The AP starts the transmission timer according to the value set in the transmission timer (S2).
(2) The AP receives a radio signal and monitors whether radio is received from another wireless LAN terminal (S3). When the AP receives the radio signal, the AP proceeds to step S12. When the wireless signal has not been received, the AP checks whether the transmission timer has expired (S4), and if not, returns to step S3. If the transmission timer has expired, it is determined that the own AP has obtained the transmission right.

(3) The AP checks the value of FLAG (S5), and if it is 2 or more (≧ 2), the AP determines that the scheduled transmission time of the audio signal has been exceeded, and proceeds to step S25. If the FLAG value is 1 (= 1), the AP determines that the scheduled transmission time of the beacon frame has been exceeded, and proceeds to step S24. When the FLAG value is 0, the AP determines that neither the audio signal nor the beacon frame has exceeded the scheduled transmission time. Next, the AP checks whether there is data to be transmitted (here, data includes a control signal, a management signal, etc.) (S6), and if there is no data to be transmitted, the transmission timer has expired. The process proceeds to step S3.

(4) If there is data to be sent in step S6, the data is sent (S7).

(5) Next, the AP receives a radio signal and waits for the completion of reception of the next radio signal (S8). When the AP completes the reception of the radio signal, the AP checks whether it is an ACK frame for the transmitted data (S9), and determines that the data transmission is successful if it is an ACK frame (S10). If it is not an ACK frame, it is determined that the data transmission is unsuccessful (S11). Depending on the success / failure of data transmission, retransmission control etc. are applied according to the judgment of the upper protocol. Regardless of whether or not an ACK frame is received, the process proceeds to step S22.

(6) The AP sets SIFS in the transmission timer (S22), and proceeds to step S2.

(7) If FLAG ≧ 2 in step S5, the AP sends the voice signal as if the scheduled time at which the voice signal should be sent has been exceeded, subtracts 2 from FLAG (S25), and proceeds to step S22. .

(8) When FLAG = 1 in step S5, the AP transmits a beacon frame on the assumption that the scheduled time for transmitting the beacon frame has passed, clears FLAG to 0 (S24), and proceeds to step S22. Transition.

(9) When the wireless signal is being received in step S3 (Yes), the reception of the wireless signal is awaited (S12). When the reception is completed, it is determined whether or not the signal is a normal signal addressed to the own AP (S13). If the signal is a normal signal addressed to the own AP, the process proceeds to step S17.

(10) In step S13, if the signal is addressed to the own AP and is not normal or not addressed to the own AP (in the wireless LAN using the AP, there is essentially no radio signal other than addressed to the own AP. Is not normal by itself, the FLAG is determined to determine whether the scheduled time for transmitting the audio signal or the beacon frame has passed (S14). When FLAG is 0, the AP transmits the retransmission data after (SIFS + ACK + DIFS + random number) time from the transmission source wireless LAN terminal that has transmitted the data to its own AP. For example, (SIFS + ACK + DIFS + random number) is set as the timer value (S16), and the process proceeds to step S2.

(11) In step S14, when FLAG is 1 or more, the AP determines that the scheduled time at which the voice signal or beacon frame should be transmitted has been exceeded. In order for the AP to transmit a voice signal or a beacon frame before transmission, SIFS that is the shortest transmission timer value is set in the transmission timer (S15), and the process proceeds to step S2.

(12) In step S17, the AP normally receives and processes a signal addressed to its own AP. At the same time, SIFS is set in the transmission timer and started (S18), and the end of the transmission timer is awaited (S19).
(13) When the transmission timer expires, the AP determines whether the received signal is RTS () (S20). If it is not RTS, the AP returns an ACK frame (S21), and proceeds to step S22. In step S20, if it is RTS, the AP sends a CTS instead of an ACK frame as a response, permits transmission to the wireless LAN terminal that is the transmission source of RTS, and sets a large value in the transmission timer to wait for the corresponding data. For example, (SIFS + ACK + DIFS + random number) is set (S23), and the process proceeds to step S2.

(14) When a beacon frame timer interrupt occurs (S31), the AP adds 1 to FLAG as shown in FIG. 7, starts the beacon frame timer (S32), and then returns from the interrupt (S33). .

(15) When a voice timer interrupt occurs (S41), the AP adds 2 to FLAG, starts the voice timer (S42), and then returns from the interrupt (S43).

[Embodiment 2] In the embodiment 2, when the access point receives RTS transmission prior to data transmission from the wireless LAN terminal, the time when the maximum duration time described in the RTS has elapsed from the current time is A data reception end time determining means for determining whether or not a predetermined time for transmitting an audio signal or a beacon frame is received, and the signal transmitting means has a maximum duration described in the RTS elapses from the current time; This is an example in which the voice signal or the beacon frame is preferentially sent when the received time is not before the scheduled time for sending the voice signal or the beacon frame.

  Furthermore, in the second embodiment, when the access point receives an RTS transmission prior to data transmission from the wireless LAN terminal, the time when the maximum duration time described in the RTS has elapsed from the current time is the audio signal or A data reception end time determination unit that determines whether or not a scheduled time for transmitting a beacon frame is reached, and the signal transmission unit has a time when the maximum duration time described in the RTS has elapsed from the current time. When the voice signal or beacon frame is not transmitted before the scheduled time, the voice signal or beacon frame is sent with priority, and then when the RTS is received again from the wireless LAN terminal, the CTS is sent to the wireless LAN terminal. It is an example as a means to send out.

  A method for suppressing transmission of a beacon frame or an audio signal due to a long packet, which is Embodiment 2 of the present invention, will be described. As is well known, International Standard 9.2 stipulates that a wireless LAN terminal requests an AP to occupy radio before sending a packet longer than a predetermined threshold. In order to facilitate the subsequent explanation, a wireless occupation permission request and a permission method for the same that are defined in International Standard 9.2 are briefly described.

  According to International Standard 9.2, when a packet whose packet length is longer than the threshold is transmitted, the wireless LAN terminal transmits a control signal called RTS to the AP, and the AP transmits a CTS (Clear to the wireless LAN terminal. It is defined that a control signal called “To Send: transmission permission” is returned. RTS and CTS include the sum of “the time for which a long packet occupies the radio”, “the time for which the ACK frame as a response occupies”, and “the period in which there is no radio signal between both packets” (Referred to as duration) is included as a parameter. Another wireless LAN terminal intercepts the above RTS and CTS, and prevents interference without sending out radio during the duration included therein.

  The second embodiment utilizes the fact that a long packet duration is included in the above RTS, and returns a CTS when it is determined that the long packet is not completely used by the beacon frame or voice signal transmission time. It is characterized by postponing transmission of a long packet. Hereinafter, the time chart of Example 2 is demonstrated using FIG.

(1) The wireless LAN terminal A sends an RTS to the AP in order to send a long packet Data1. The RTS includes a duration that occupies the radio for the transmission of Data1.
(2) The AP that has received the RTS adds the current time and the duration described above, compares it with the scheduled time at which a beacon frame or audio signal should be transmitted, and before the scheduled time as illustrated in FIG. When it is determined that the radio occupation for sending Data1 is finished, CTS is sent to allow sending Data1. Then, at the scheduled time, the AP sends out a beacon frame and an audio signal.
(3) As illustrated in FIG. 9, when the AP that has received the RTS determines that the radio occupation for sending Data1 ends after the scheduled time, the AP does not return the CTS and does not return the Data1. Do not allow sending. When the beacon frame or voice transmission time is reached, the AP sends a beacon frame or voice signal. After that, when the RTS is received again from the wireless LAN terminal A, the AP returns a CTS and permits the transmission of Data1.

  Next, the detailed operation of the second embodiment will be described with reference to FIG. FIG. 10 is a diagram in which the condition determination according to the second embodiment is inserted immediately before the CTS transmission part in the lower right of FIG.

(1) The AP determines whether the received signal is RTS (S20), and if it is not RTS, it returns an ACK frame as in FIG. 6 (S21).
(2) In the case of RTS, the AP determines whether the value obtained by adding the duration requested by RTS and the current time exceeds the scheduled time at which a beacon frame or a voice signal should be transmitted. Is determined (S51). If it is determined that the number does not exceed, the AP sends a CTS as in FIG. 6 (S23). If the AP is determined to be exceeded, the AP, which is the object of the present embodiment, “does not send the CTS because the RTS transmission source is not allowed to send data, and gives priority to sending the voice signal / beacon frame from the AP. The transmission timer is set to SIFS "(S23).

[Third Embodiment] In the third embodiment, when the access point receives RTS transmission prior to data transmission from the wireless LAN terminal, the time when the maximum duration time described in the RTS has elapsed from the current time is expressed as A data reception end time determination means for determining whether or not the scheduled time for sending an audio signal or a beacon frame is received, and the signal sending means is used when the received data with the RTS is abnormal; When the time when the maximum duration time described in the RTS has elapsed from the current time of the data to be retransmitted is not before the scheduled time for transmitting the voice signal or beacon frame, the scheduled time for transmitting the voice signal or beacon frame This is an example of means for sending a dummy signal that ends before time.

  Further, in the third embodiment, at the access point, when the data transmission is received from the wireless LAN terminal, the time when the maximum duration time that does not require RTS has elapsed from the current time is the regular time when the voice signal or beacon frame is transmitted. A data reception end time determination unit that determines whether the time is earlier than the current time, and the signal transmission unit transmits the audio signal or the beacon frame at the time when the maximum duration time without RTS has elapsed from the current time. This is an example of means for sending a dummy signal that ends before the scheduled time for transmitting the audio signal or beacon frame when it is not before the scheduled time.

  As a third embodiment, a time chart when a packet that does not transmit an RTS due to a short packet length is prevented from delaying the transmission of a beacon frame or an audio signal will be described with reference to FIG.

(1) The AP that has finished receiving Data1 from the wireless LAN terminal A without RTS sends the current time and “the maximum packet length within the range in which RTS is not sent (the RTS− described in International Standard 9.2). "Duration when sending a packet equivalent to Threshold") is added to determine whether this time exceeds the scheduled time at which a beacon frame or audio signal should be sent.
(2) When the added value exceeds the scheduled time and the radio is not transmitted from another device, the AP transmits a dummy signal and suppresses the radio from being transmitted from another wireless LAN terminal, A beacon frame or audio signal is sent at a fixed time.

  According to this method, the AP can suppress the transmission from the wireless LAN terminal of Data exceeding the scheduled time of the beacon frame and voice transmission, and can transmit the beacon frame and the voice at the scheduled time.

  Next, the detailed operation of the third embodiment is shown in a flowchart with reference to FIG. FIG. 13 is a diagram in which a condition determination according to the third embodiment is inserted when the transmission data is determined to be “absent” by the determination of “transmission data present?” In step S6 in the left center of FIG.

(1) If the transmission data is determined to be “absent” based on the determination of “transmission data present?” In step S6, the AP determines “packets that do not require RTS transmission (international standard 9. It is determined whether the maximum duration in the range of RTS-Threshold in Section 2 and the current time are added and whether the beacon frame / voice transmission scheduled time is exceeded (S61). If not exceeded, the AP proceeds to “receive radio signal” (S3) as in FIG. When exceeding, the AP performs “transmission of a dummy signal until the time obtained by subtracting the SIFS time from the scheduled transmission time of the beacon frame / audio signal”, which is the object of the third embodiment. That is, (transmission time of beacon frame / voice-current time-SIFS) is set in the transmission timer, the transmission timer is started (S62), and a dummy signal is transmitted until the transmission timer expires (S64) ( S63).

  Here, since the dummy signal only needs to suppress wireless transmission from another wireless LAN terminal, it may have any content as long as it does not adversely affect the wireless LAN terminal or the like.

(2) Next, in order to transmit a beacon frame or a voice signal after the SIFS wait time, the process proceeds to a block for setting SIFS in the transmission timer of FIG. 6 (S22).

  You may implement combining Example 1- Example 3 demonstrated above. That is, in order to prevent a long packet from being sent immediately before the scheduled time at which a beacon frame or audio signal is to be sent, the sending of a long packet is not permitted without sending a CTS for RTS (Example 2), In order to prevent a short packet that does not require RTS from being sent immediately before the time when a beacon frame or audio signal should be sent, a dummy signal is sent from the AP immediately before the scheduled transmission time (Example 3). Anyway.

  The third embodiment may be applied to the transmission error retransmission described in the first embodiment. That is, in the first embodiment, the initial data is allowed to exceed the scheduled time at which the beacon frame and the audio signal should be transmitted, and the retransmission data is transmitted after the beacon frame and the audio signal are transmitted. As illustrated in FIG. 12, the transmission of the first data ends before the scheduled time, but the data to be retransmitted in response to the transmission error is expected to exceed the scheduled time and continue to use the radio. The AP may send a dummy signal and send a beacon frame or audio signal at a fixed time to prevent a beacon frame or audio transmission delay due to retransmission data. The wireless LAN terminal A retransmits Data1 after receiving the beacon frame and the audio signal.

  In the above example, a case where a voice signal or a beacon frame is transmitted from the AP at a fixed time is shown. However, the AP may transmit a control command for transmitting a voice signal to the wireless LAN terminal at a fixed time. As a result, the wireless LAN terminal can send an audio signal to the AP at a fixed time.

[Embodiment 4] In Embodiment 4, in the above-mentioned access point, the signal sending means has a time when the maximum duration time of data to be sent has passed before a scheduled time at which the voice signal or beacon frame is sent. Data transmission end time determination means for determining whether or not the signal transmission means is configured to cause the time when the maximum duration time has elapsed from the current time to be before the scheduled time for transmitting the audio signal or beacon frame. This is an example of means for suppressing transmission of data to be transmitted.

  In the above first to third embodiments, the packet addressed to the AP from the wireless LAN terminal is prevented from sending out the audio signal or the beacon frame with a delay from the scheduled time. Next, an example in which a packet addressed to a wireless LAN terminal from an AP is prevented from transmitting a voice signal or a beacon frame with a delay from a fixed time will be described as a fourth embodiment with reference to a time chart of FIG.

(1) As shown in FIG. 14, before the AP sends Data1 to the wireless LAN terminal A, it calculates the duration time required for sending Data1, adds it to the current time, and sends a beacon frame or audio signal. Determine whether the scheduled time is exceeded.
(2) If it is determined that it does not exceed, the AP transmits Data 1 and receives an ACK frame from the wireless LAN terminal A to confirm that normal transmission has been completed. Send the frame.

(3) Next, before sending Data2 to the wireless LAN terminal B, the AP calculates the duration time of Data2 as in the case of Data1, adds it to the current time, and sends a beacon frame or voice signal at a fixed time. Determine if the time is exceeded.
(4) If the AP is determined to be exceeded, the AP postpones sending Data2 (indicated by a broken line), and sends the audio signal when the scheduled time for sending the audio signal comes. Accordingly, if Data2 is transmitted, the ACK frame (indicated by a broken line) addressed to the AP is not returned from the wireless LAN terminal B.
(5) Although not shown, the AP transmits Data2 after transmitting the audio signal.

  The data to be transmitted from the AP includes a packet having a long packet length and a short packet. If it is determined that the short packet does not exceed the scheduled time for transmitting the beacon frame or the audio signal, the short packet is transmitted. Of course.

  Next, with reference to FIG. 15, the detailed operation of the fourth embodiment is shown in a flowchart. FIG. 15 is a diagram in which a condition determination according to the fourth embodiment is inserted when the transmission data is “present” by the determination of “transmission data present?” In step S6 in the upper left of FIG.

(1) In FIG. 15, when it is determined that the data to be transmitted from the AP is “present”, the sum of the duration time of the transmission data and the current time, which is a feature of the present embodiment, is the scheduled time of transmission of the beacon frame / voice. Is determined (S81).

(2) If it is exceeded in step S81, the AP postpones sending data to be sent from the AP, which is the object of this embodiment, and the sum of the maximum duration without RTS and the current time is the same as in FIG. Determines whether or not the beacon frame / sound scheduled transmission time is exceeded (S61), it is determined whether or not a dummy signal needs to be transmitted.

(3) If it is not exceeded in step S81, the AP sends data as in FIG. 6 (S7).

  In the above-described embodiments, the method in which the AP and the wireless LAN terminal transmit the audio signal and the beacon frame signal with priority over the data in order to transmit the audio signal and the beacon frame signal on a regular basis has been described.

  As described above, there is an interference radio wave from a microwave oven or the like that should be given higher priority than an audio signal, a beacon frame, or data. In order to minimize the influence of this jamming radio wave, it is necessary for the wireless LAN to perform wireless transmission control. When the AP detects the presence or absence of jamming radio waves and obtains the frequency and phase, it is possible to predict the time when the jamming radio waves will next be “present” and the time when “jamming” will be next. Therefore, the embodiment described above may be applied as follows.

(Application example) When sending data, a voice signal, or a beacon frame as a packet, the AP includes the packet transmission time and the response time of the ACK frame, if the response time of the ACK frame is required. It is determined whether transmission / reception is completed before becoming “present”, and when transmission / reception is completed before the next jamming radio wave is “present”, the packet is transmitted. However, if transmission / reception is not completed before the next jamming signal “exists”, transmission is not performed. If there is a shorter packet and transmission / reception is completed before the next jamming signal “exists”, AP Sends the short packet with priority.

  In order to prevent the hidden terminal that cannot receive the jamming signal from the microwave when the jamming signal is “present”, the AP may send a dummy signal during the period when the jamming signal is “present”.

1 is a diagram showing a system configuration diagram of a general wireless LAN. FIG. The figure which shows the hardware block diagram of general AP. The hardware block diagram of a general wireless LAN terminal is shown. FIG. 6 is a time chart for sending out a beacon frame and an audio signal when a transmission error occurs in data sent from a wireless LAN terminal in the first embodiment. In Example 1, the transmission time chart of a beacon frame and an audio | voice signal when the transmission error generate | occur | produces in the data which AP transmitted is shown. 6 is a flowchart of an AP that prioritizes beacon frames and audio signals over retransmission data according to the first exemplary embodiment. 6 is a flowchart of an AP that prioritizes beacon frames and audio signals over retransmission data according to the first exemplary embodiment. In Example 2, the time chart in case AP permits data transmission by transmitting CTS is shown. In Example 2, the time chart when AP transmits CTS and does not permit data transmission is shown. 9 shows an operational flowchart of an AP in the second embodiment. In Example 3, it shows the time chart in the case of suppressing that AP transmits a dummy signal and another wireless LAN terminal transmits just before a beacon frame and an audio | voice signal. In Example 3, it shows the time chart when AP transmits a dummy signal and it suppresses that another wireless LAN terminal transmits resending data just before a beacon frame and an audio | voice signal. 10 shows an operational flowchart of an AP in the third embodiment. In Example 4, the time chart which suppresses that the packet transmitted from AP generate | occur | produces the fixed transmission delay of a beacon frame and an audio | voice signal is shown. 14 shows an operation flowchart of an AP in the fourth embodiment. The transmission time chart of the beacon frame and audio | voice signal in the conventional DCF (Distributed Coordination Function) is shown. A transmission time chart of beacon frames and audio signals when retransmission occurs in the conventional DCF is shown.

Explanation of symbols

1-1, 1-2, 1-3, 1-4, 1-5, 1-6: wireless LAN terminals 2-1, 2-2, 2-3, 2-4: access points 3-1, 3 -2: Router 4-1, 4-2, 4-3, 4-4: Personal computer (wired LAN terminal)
5: Internet (IP) network 1A: Information communication terminal unit 1B: Radio unit 10: Communication processing unit 10-1: Program memory 10-2: Work memory 11: Antenna 12: RF unit 13: Baseband unit 14: MAC processing Unit 15: Upper layer processing unit 16: Terminal interface unit 19: Bus 2A: Router unit 2B: Radio unit 20: Communication processing unit 20-1: Program memory 20-2: Work memory 21: Antenna 22: RF unit 23: Base Band unit 24: MAC processing unit 29: Bus

Claims (4)

An access point in a wireless LAN system comprising an access point and a plurality of wireless LAN terminals connected to the access point via a wireless LAN,
A clocking means for clocking a fixed time for sending an audio signal or a beacon toward the wireless LAN terminal;
When the scheduled time for transmitting the audio signal or beacon comes, signal transmission means for preferentially transmitting the audio signal or beacon;
When the wireless LAN terminal receives an RTS (Request To Send: transmission permission request) prior to data transmission, the time when the maximum duration time described in the RTS has elapsed from the current time is transmitted as the voice signal or beacon. A data reception end time determining means for determining whether or not it is before the scheduled time,
The signal transmission means preferentially transmits the audio signal or beacon when the time when the maximum duration time described in the RTS has elapsed from the current time is not before the scheduled time for transmitting the audio signal or beacon. Is a means to
An access point characterized by that. The access point according to claim 1 ,
Whether or not the time when the maximum duration time described in the RTS has elapsed from the current time when the RTS transmission prior to data transmission is received from the wireless LAN terminal is before the scheduled time at which the voice signal or beacon is transmitted A data reception end time determination means for determining whether or not
The signal transmission means preferentially transmits the audio signal or beacon when the time when the maximum duration time described in the RTS has elapsed from the current time is not before the scheduled time for transmitting the audio signal or beacon. The access point is a means for sending CTS (Clear To Send) to the wireless LAN terminal when an RTS is received again from the wireless LAN terminal thereafter . The access point according to claim 1 ,
Whether or not the time when the maximum duration time described in the RTS has elapsed from the current time when the RTS transmission prior to data transmission is received from the wireless LAN terminal is before the scheduled time at which the voice signal or beacon is transmitted A data reception end time determination means for determining whether or not
When the received data with the RTS is abnormal, the signal transmission means determines that the time when the maximum duration time described in the RTS has elapsed from the current time of the data to be retransmitted is the audio signal or beacon. An access point, characterized in that it is a means for transmitting a dummy signal that ends before the scheduled time for transmitting the audio signal or beacon when it is not before the scheduled time for transmission . The access point according to claim 1 ,
End of data reception to determine whether or not the time when the maximum duration time without RTS has elapsed from the current time when receiving data transmission from the wireless LAN terminal is before the scheduled time for transmitting the voice signal or beacon A time determination means,
The signal transmission means is configured to send the audio signal or the beacon before the scheduled time when the time when the maximum duration time without RTS has elapsed from the current time is not before the scheduled time to transmit the audio signal or the beacon. An access point, which is a means for sending a dummy signal to end .

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