JP2006033070A - Data transmission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transmission control method whereby no packet collision takes place even when many wireless terminals are going to transmit a huge amount of data. <P>SOLUTION: A plurality of master units 1-1 to 1-8 are connected by a wired LAN 4. Slave units corresponding to the master units are connected by a wirless LAN. The master units mutually transmit channels used for communication with the slave units via the wired LAN. A plurality of the master units using the same channel respectively assign time slots to a plurality of the master units under the same rule and inform the corresponding slave units about the time slots. When data to be transmitted take place in each master unit or the slave units, the data are transmitted for a communication time zone assigned to their own units. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a data transmission method for preventing congestion when a large number of terminal devices are connected to a network by a wireless LAN.

  Conventionally, wireless LAN systems have been standardized and standardized as IEEE802.11a, 11b, and 11g, and in these standards, transmission packet collision avoidance means called CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) is defined. Has been.

  CSMA / CA is a procedure for monitoring the presence of radio waves transmitted at the communication frequency for a certain period of time and confirming the absence of radio waves to avoid collision of transmitted packets by transmitting its own packet. Yes (see Non-Patent Document 1).

In this procedure, if Ack is received from the partner station after transmission of the packet, it is determined that normal communication has been completed. If Ack cannot be received, the packet is retransmitted as communication failure.
Tutorial of draft Standard IEEE 802.11 Part 3: the MAC entity (Phil Belanger and Wim Diepstraten), "Search July 9, 2004", Internet <ftp://stdsbbs.ieee.org/pub/802_main/802.11/tutorial /tutmac3.ppt>

  However, in the above procedure, the frequency is watched in advance to check whether or not a packet is currently being transmitted. However, when a plurality of devices start transmitting simultaneously, a collision cannot be avoided. Packet collisions are likely to occur during high loads when many terminals are trying to transmit a large amount of data at the same time. In such a high-load situation, retransmission of packets due to collisions causes further collisions, and the network as a whole There was a problem that the throughput was extremely lowered.

  An object of the present invention is to provide a data transmission control method that does not generate a packet even when a large number of wireless terminals attempt to transmit a large amount of data at the same time.

  The invention of claim 1 is a communication system having a plurality of master units connected by a wired network, and a plurality of slave units corresponding to any of the plurality of master units and communicating with the corresponding master units wirelessly. A method in which each parent device transmits a radio frequency channel used for communication with a corresponding child device via a wired LAN to each other, and a plurality of methods using the same radio frequency channel. A procedure in which the parent device assigns a communication time zone to each of the plurality of parent devices using the same radio frequency channel according to the same rule, and each parent device is assigned to the corresponding child device and the communication assigned to the own device. A procedure for notifying the time zone, and a procedure for transmitting the data during the communication time zone assigned to the own device when data to be transmitted to each of the parent device and the corresponding slave device is generated. Features.

  A plurality of parent devices communicate in advance via a wired LAN, and a communication time zone (allocation time slot) in which each parent device communicates wirelessly with the child device is determined. This communication time zone is determined independently by each parent device, but since the communication time zones are assigned based on the same rules (for example, assigned in the order of identification numbers) The communication time zones are assigned in the same order. Therefore, packet collision does not occur in wireless communication without providing a host device that controls the entire network.

  The invention of claim 2 is characterized in that each slave unit includes a procedure for putting the radio communication circuit unit in a dormant state except for a communication time zone assigned to the own unit.

  When the slave unit is battery-driven, power consumption by the wireless communication circuit unit that is an analog circuit becomes a problem. This power consumption is not greatly different between the transmission mode and the reception mode. Therefore, in the present invention, the communication time zone is determined as described above, and data transmission / reception is not performed outside the communication time zone, so that the wireless communication circuit unit does not receive or transmit data outside the communication time zone. Power consumption is reduced by setting the mode.

  According to the present invention, by assigning the time zones in which wireless transmission is possible to each device so as not to overlap, packet transmission collision does not occur, and the problem of reduced throughput does not occur even when the network is heavily loaded.

  Further, since the packet does not arrive except for the allocated time, the LAN interface circuit can be in a dormant state during that period, and the power consumption can be reduced.

  A network system according to an embodiment of the present invention will be described with reference to the drawings. This network system includes a plurality of parent devices connected via a wired LAN and a plurality of child devices connected to the wired LAN via a wireless LAN. Each slave unit corresponds to each master unit. This system is applied to, for example, a large-scale karaoke box having a large number of rooms. The parent device is a karaoke device installed in each room, and the child device reserves a song for the karaoke device. It is a multi-function remote control device that checks the reservation status.

  In FIG. 1, for simplicity of explanation, a system in which eight master units and slave units are provided and two wireless LAN access points are provided is illustrated. A system is assumed in which about tens to 100 master devices and slave devices are provided.

  FIG. 1 is a block diagram of the network system. In each room, a master unit 1 (1-1 to 1-8) as a karaoke device and a slave unit 2 (2-1 to 2-8) as a multi-function remote controller are installed. Master units 1-1 to 1-8 are connected to each other via a wired LAN 4. Two wired LAN access points 3 (3-1, 3-2) are connected to the wired LAN 4. The slave units 2-1 to 2-8 communicate with the nearest access point 3, but in this figure, the slave units 2-1 to 2-4 communicate with the access point 3-1, and the slave unit 2- 5 to 2-8 communicate with the access point 3-2.

  With the above configuration, the slave unit 2 communicates with the corresponding master unit 1 via the access point 3 and the wired LAN 4. The subunit | mobile_unit 2 transmits the request information of a karaoke song with respect to the main | base station 1, and requests | requires the information of a reservation status, the lyrics of the karaoke song in performance, etc. The base unit 1 registers the received request information in the reservation list and transmits the contents of the reservation list to the handset 2 as reservation status information. Also, lyrics of karaoke songs are transmitted in response to a request from the slave unit 2.

  Since the access points 3-1 and 3-2 are set to use different channels (radio frequency bands), they can perform wireless communication with the slave unit 2 that is in charge at the same time without interfering with each other. However, since the subunit | mobile_units 2-1 to 2-4 communicate with the same access point 3-1, if it communicates simultaneously, a radio wave will collide and it will become impossible to communicate. In order to avoid this, the time slot (time zone) is divided and assigned. Similarly, time slots are divided and assigned to the slave units 2-5 to 2-8 communicating with the access point 3-2.

  FIG. 2 is a block diagram of the master unit 1 and the slave unit 2.

  The base unit 1 includes a wired LAN interface unit 11 that performs packet communication via the wired LAN 4, an application function unit 13 that executes a function as the base unit, and a control unit 12 that controls the operation of the apparatus. The control unit 12 controls the wired LAN interface unit 11 and the application function unit 13 to control communication and application operations. The control unit 12 includes an allocated time slot storage unit 121 that stores an allocated time slot that is a communication time zone with the access point 3 allocated to the own device, and a clock 122 that measures time. The clock 122 is synchronized with the entire network (all parent devices 1).

  In addition, the control unit 12 controls the wired LAN interface unit 11 to share the wireless LAN channel used when communicating with its own identification information and the corresponding slave unit via the wired LAN 4 to all other master units. Based on the identification information / used channel transmitted from each parent device, and allocates the assigned time slot of the own device and stores it in the assigned time slot storage unit 121, and stores the assigned time slot in its own child device. Send. In addition, time synchronization processing is performed to synchronize the clock 122 with all the parent devices and the corresponding child devices.

  In the case of a karaoke apparatus, the application function unit 13 is a sound source unit that performs a performance of a karaoke song, a video playback unit that plays back a background video, or the like. The control unit 12 controls the application function unit 13 in response to a request from the handset 2, and performs performance of karaoke music, display of background video / lyrics, and the like.

  The subunit | mobile_unit 2 is battery drive, the wireless LAN interface part 21 which performs packet communication via the access point 3, the application function part 23 which performs a predetermined function, and the control part 22 which controls operation | movement of an apparatus are included. I have. The control unit 22 controls the wireless LAN interface unit 21 and the application function unit 23 to control the communication function and the application function. The control unit 22 includes an assigned time slot storage unit 221 that stores the assigned time slot of the own device and a clock 222 that measures time. The clock 222 is synchronized with the time notified from the parent device 1 (synchronized with the entire network).

  The control unit 22 controls the application function unit 23 and also controls the wireless LAN interface unit 21 to receive the allocation time slot transmitted from the base unit 1 and store it in the allocation time slot storage unit 221. The clock 222 is synchronized with the parent device 1 by time synchronization processing from the parent device 1. The application function unit 23 includes a reservation status transmitted from the parent device 1, display of lyrics, display of a song name list for music selection, and the like.

  The wireless LAN interface unit 21 is configured by (mainly) an analog circuit that performs wireless communication with an access point, and consumes about 1 W of power in the normal mode of transmission mode / reception mode. In the power saving mode in which the transmission / reception function is stopped, the power consumption can be suppressed to about 0.1 W.

In the network system configured as described above, each parent device 1 determines an assigned time slot by the following processing. (1) All parent devices 1 on the wired LAN 4 synchronize the time of the built-in clock 122 and correspond to this synchronized time. It transmits to the subunit | mobile_unit 2. This synchronizes the time of all terminal devices on the wired LAN / wireless LAN. This process is performed at time slot allocation or periodically.

  (2) Each parent device 1-1 to 1-8 controls the wired LAN interface unit 11 of the transmission / reception control unit 12, and obtains its own identification information and access point information of wireless LAN to be used (channel information to be used). , Broadcast to all the parent devices 1.

  (3) Each parent device receives the identification information and channel information transmitted from all other parent devices by broadcast, and selects a parent device that uses the same channel as the own device from among the identification information and channel information. The parent devices (including the own device) that use the same channel are arranged in the order of identification numbers, and time slots are assigned in that order. The time slot assigned to the own device is stored in the assigned time slot storage unit 121 as the assigned time slot.

  The time slots are sequentially and cyclically assigned at intervals of 10 milliseconds from the hour at every hour on the hour, and a predetermined time immediately before the hour is a pause time.

  By determining the assigned time slot of each parent device by this method, even if each parent device independently determines its own assigned time slot, they do not overlap each other.

  In this embodiment, four of the parent devices 1-1 to 1-4 use the same channel (access point), and four of the parent devices 1-5 to 1-8 use the same channel (access point). Since it is used, as shown in FIG. 3, four time slots arranged along the time axis are assigned to each parent device for each of the four units.

  (4) Subsequently, each parent device 1 transmits information on its own assigned time slot to the corresponding child device 2. This information is sent from the parent device 1 to the child device 2 via the wired LAN 4 and the access point 3 by wireless LAN. This communication is not performed according to the time slot, but is performed at random. However, since the amount of data to be communicated is small, it can be avoided by a general collision avoidance procedure (CSMA / CA or the like).

  (5) Thereafter, the control unit 22 of the slave unit 2 waits for a packet transmission request from the application function unit 23 until the assigned time slot is reached. When the assigned time slot is reached, the control unit 22 passes through the wireless LAN interface unit 21. Packet transmission. Similarly, in the base unit 1, the control unit 12 waits for packet transmission to the handset 2 until an assigned time slot arrives.

  As described above, since packet transmission between each set of the master unit 1 and the slave unit 2 is executed only for the time slot assigned to the set of the master unit and the slave unit, packets transmitted from different sets of devices are transmitted. Does not collide on the LAN.

  In addition, the control unit 22 of the slave unit sets the wireless LAN interface unit 21 to the power saving mode and sets the sleep mode except for the assigned time slot. Thereby, the power consumption of the subunit | mobile_unit 2 can be suppressed significantly.

  The operations of the master unit and the slave unit in the above-described allocation time slot setting procedure will be described with reference to the flowchart of FIG.

  FIG. 4A is a flowchart showing the operation of the master unit. First, the clocks are synchronized between the parent devices on the wired LAN 4 (s1). This clock synchronization may be performed not only at this timing but also at an arbitrary timing. Next, all base units exchange the identification number and the information of the channel used in the broadcast communication (s2). At this time, each parent device transmits the identification number and channel information of the own device and receives the identification number and channel information of the other parent device. After the exchange of the identification number / channel information, the master units using the same channel are arranged in order of identification number, and time slots are assigned in order of identification number (s3). Since the clocks are synchronized and the time frame of each time slot is predetermined at 10 milliseconds from the hour every second, even if each parent unit independently determines its own assigned time slot, The time slots are assigned in the same way on the machine, and the assigned time slots are assigned to the respective parent machines without overlapping each other.

  When the time slot is determined, the slave unit is informed of the time slot and the clock of the slave unit is synchronized (s4). Thereafter, the operation according to this schedule is started.

  In the operation mode of each master unit 1, if there is data to be transmitted, it is transmitted within the time frame of its own allocated time slot, and otherwise (in its own allocated time slot), it waits in the reception state. It is a form to do.

  On the other hand, the operation mode of each slave unit 2 is: “Receive mode is set in its own assigned time slot, and the wireless LAN interface unit 21 is set in the power saving mode in other time zones. When there is, this is transmitted within the time frame of its own assigned time slot. "

  As described above, according to this embodiment, by automatically setting the corresponding master unit and the slave unit to perform communication only in the time slot assigned to the own unit, a large number of master units and slave units can perform streaming or the like. Even when a large amount of data is transmitted and received, it is possible to prevent a reduction in communication efficiency due to a collision.

  In addition, since the slave unit 2 can set the wireless LAN interface unit 21 with high power consumption in the analog circuit to the power saving mode in the time zone other than the assigned time slot of its own unit, the power consumption is greatly increased. Can be improved.

  In this embodiment, the slave unit 2 communicates with the master unit 1 via the access point 3 and the wired LAN 4. However, the same applies to a system in which the slave unit 2 and the master unit 1 communicate directly. If there is a possibility of communication collision using the communication channel, the present invention can be similarly applied.

Block diagram of a network system according to an embodiment of the present invention Block diagram of the parent and slave units of the network system A diagram showing the time slots assigned to each master unit and slave unit Flow chart showing the operation of the master unit and slave unit

Explanation of symbols

1 (1-1 to 1-8) ... Master unit 2 (2-1 to 2-8) ... Slave unit 3 (3-1, 3-2) ... Wireless LAN access point 4 ... Wired LAN
DESCRIPTION OF SYMBOLS 11 ... Wired LAN interface part 12 ... Control part 13 ... Application function part 21 ... Wireless LAN interface part 22 ... Control part 23 ... Application function part

Claims (2)

A method executed in a communication system having a plurality of master units connected by a wired network and a plurality of slave units corresponding to any of the plurality of master units and communicating with the corresponding master units wirelessly. ,
Procedures for each parent device to transmit a radio frequency channel used for communication with the corresponding child device to each other via a wired LAN,
A procedure in which a plurality of master units using the same radio frequency channel allocate communication time zones to a plurality of master units using the same radio frequency channel according to the same rule,
Procedure for each parent device to notify the corresponding child device of the communication time zone assigned to itself
When data to be transmitted to each parent device and any of the corresponding child devices occurs, a procedure for transmitting the data during the communication time zone assigned to the own device,
A data transmission control method comprising:   A data transmission control method comprising: a procedure in which each slave unit puts a wireless communication circuit unit into a dormant state except for a communication time zone assigned to the own unit.

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