JP2018046545A - Communication method, wireless base station, server, and wireless distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication method capable of transmitting data in real time on a wireless network.SOLUTION: A communication method includes the steps of: generating a packet containing data with a preset priority; acquiring a channeled use time; calculating a channel usable time on the basis of the channeled use time; calculating a first channel use anticipated time; calculating a wireless transmission rate applied when a wireless base station 13 transmits a packet to the wireless terminals 14a and 14b on the basis of data priority included in the packet so that the first channel use anticipated time becomes less than or equal to the channel usable time; and transmitting the packet and information indicating the wireless transmission rate to the wireless base station 13.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a communication method, a radio base station, a server, and a radio distribution system.

  As a communication method used on a wireless network constructed by a wireless LAN (Local Area Network) defined by IEEE 802.11, there are unicast, multicast, and broadcast.

  Unicast is a communication method for transmitting and receiving packets on a one-to-one basis between a specific radio base station and a specific radio terminal, between two specific radio terminals, or the like.

  Multicast forms at least one group (hereinafter referred to as “multicast group”), and from a wireless base station or wireless terminal participating in any multicast group to another wireless base station or other participating in the same multicast group Is a communication method for transmitting a packet to a wireless terminal. This communication method is used, for example, when communication is performed by IP (Internet Protocol) multicast.

  Broadcast is a communication method for transmitting a packet without specifying a destination. This communication method is used, for example, when transmitting a beacon frame for advertisement from a wireless base station to a wireless terminal.

  In the above-described communication method using multicast and broadcast, reception confirmation using an Ack frame is not performed for transmission of a frame in a wireless LAN. For this reason, even when a frame transmission error occurs, frame retransmission in the wireless LAN is not automatically performed.

  Next, a method for transmitting a packet by IP multicast (hereinafter referred to as “multicast packet”) will be described. In IP multicast, communication is performed using an IP address called a multicast IP address for identifying a multicast group (see, for example, Patent Documents 1 and 2).

  Specifically, when the server transmits a multicast packet addressed to an arbitrary multicast group, the multicast IP address corresponding to the multicast group is designated as the destination address of the multicast packet.

  On the other hand, when a wireless terminal (client) receives a multicast packet transmitted to a multicast group, it receives a multicast packet addressed to a multicast IP address corresponding to the multicast group. Therefore, a wireless terminal notifies a multicast IP address to a wireless base station on an IP network connected to the wireless terminal using, for example, an IGMP (Internet Group Management Protocol) Join message for IPv4. To declare that the packet addressed to the multicast IP address is received.

  When the wireless base station receives the Join message, a distribution tree is constructed so that multicast packets addressed to the multicast IP address are transferred to the wireless terminal between the wireless base station on the IP network and the router. Thereby, the wireless base station and the router on the IP network transfer the multicast packet to the wireless terminal based on the constructed distribution tree.

Japanese Patent No. 4386292 JP 2007-329614 A

  However, the conventional multicast communication method may not be able to transmit multicast packets in real time on the wireless network.

  Therefore, the present disclosure provides a communication method, a radio base station, a server, and a radio distribution system that can transmit data in real time on a radio network.

  A communication method according to an aspect of the present disclosure includes a method of multicasting a packet via at least one radio terminal connected to a radio base station via a radio network using an arbitrary channel via the radio base station. A communication method in a server that transmits by broadcast, the step of generating the packet including data for which priority is set in advance, and a time during which the channel is used per unit time in the radio base station. A channel usage time that is a time during which the channel can be used per unit time for the wireless base station to transmit the packet to the wireless terminal based on the channel usage time; Calculating a possible time; and the radio base station sends the packet to the radio terminal. To calculate a first channel use expected time which is a time expected to use the channel, and so that the first channel use expected time is equal to or less than the channel usable time. Calculating a radio transmission rate to be applied when the radio base station transmits the packet to the radio terminal based on the priority of the data included in the data, and information indicating the packet and the radio transmission rate Transmitting to the radio base station.

  These comprehensive or specific modes may be realized by a recording medium such as a system, method, integrated circuit, computer program, or computer-readable CD-ROM (Compact Disc-Read Only Memory). The present invention may be realized by any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

  According to the communication method according to one aspect of the present disclosure, when data is transmitted by multicast or broadcast on a wireless network, the wireless transmission rate is adaptively controlled based on the priority of the data, whereby the data is real-time. Can be sent to.

FIG. 1 is a diagram illustrating a configuration of a wireless distribution system according to an embodiment. FIG. 2 is a block diagram showing a configuration of the radio base station according to the embodiment. FIG. 3 is a block diagram illustrating a configuration of the server according to the embodiment. FIG. 4 is a diagram illustrating an example of a wireless transmission rate control management table. FIG. 5 is a flowchart illustrating processing of the server according to the embodiment. FIG. 6 is a flowchart specifically showing the wireless transmission rate changing process in FIG. FIG. 7A is a diagram for explaining an example of the wireless transmission rate change process in FIG. FIG. 7B is a diagram for explaining an example of the wireless transmission rate change process in FIG. 5. FIG. 7C is a diagram for describing an example of the wireless transmission rate change process in FIG. 5.

(Knowledge that became the basis of this disclosure)
The present inventors have found that the following problems occur with respect to the technique described in the “Background Art” column.

  First, access control in a wireless LAN will be described. In wireless LAN, autonomously distributed access control based on CSMA / CA (Carrier Sense Multiple Access / Collision Aidance) called DCF (Distributed Coordination Function) using a preselected radio frequency (hereinafter referred to as “channel”). Is done. Hereinafter, access control using DCF in the wireless distribution system will be described.

  The wireless distribution system includes a server, a wireless base station, a first wireless terminal, and a second wireless terminal. The server is connected to the wireless base station via a wired network. The radio base station constructs a radio network using an arbitrary channel. The first wireless terminal and the second wireless terminal that are clients are connected to a wireless base station via a wireless network.

  When transmitting a packet to the server, the first wireless terminal transmits a frame including the packet to the wireless base station using an arbitrary channel. At this time, in order to prevent occurrence of channel interference on the wireless network, the wireless base station and the second wireless terminal transmit frames while the first wireless terminal transmits a frame using the channel. Can not do it. In addition, when the radio wave transmitted by the first wireless terminal reaches another wireless network that uses the same channel as the channel, the first wireless terminal transmits a frame using the channel. Meanwhile, the radio base station and the radio terminal that configure the other radio network cannot transmit the frame.

  Here, the wireless transmission rate in the wireless LAN will be described. In a wireless LAN, an arbitrary wireless transmission rate is selected from a plurality of wireless transmission rates and a frame is transmitted. For example, in the IEEE802.11a standard, an arbitrary wireless transmission rate can be selected from eight wireless transmission rates of 6, 9, 13, 18, 24, 36, 48, and 54 Mbps.

  In general, the lower the wireless transmission rate, the fewer transmission errors occur on the wireless network and the longer the frame can be reached. This increases the reliability of frame transmission. On the other hand, as the wireless transmission rate increases, more information can be transmitted in a shorter time. For this reason, when transmitting frames of the same length, the higher the wireless transmission rate, the shorter the time for using the channel.

  Next, a description will be given of a wireless transmission rate when a frame is transmitted by multicast on a wireless network in the wireless distribution system described above.

  When the server transmits a frame by multicast using IP multicast to the first wireless terminal and the second wireless terminal, the wireless base station transmits the frame received from the server via the wireless network. Transmit to the first wireless terminal and the second wireless terminal. Generally, when the distance between the radio base station and the second radio terminal is longer than the distance between the radio base station and the first radio terminal, the radio base station to the second radio terminal The attenuation amount of the radio wave reaching the first radio terminal is larger than the attenuation amount of the radio wave reaching the first radio terminal from the radio base station.

  As described above, when a frame is transmitted by multicast on the wireless network, the retransmission of the frame is not automatically performed when a frame transmission error occurs. Therefore, in order to ensure the reliability of frame transmission to a plurality of wireless terminals having different radio wave reception conditions, the slowest wireless transmission rate is selected so that the reachable range of the frame is widened. However, when the selected wireless transmission rate is low, it is difficult to transmit data with a high bit rate in real time.

  In order to deal with such a problem, the method disclosed in Patent Document 1 uses a multicast IP address to be used when a radio base station transmits a frame to a plurality of radio terminals by multicast, and to the multicast IP address. The bit rate information of the data included in the frame transmitted from the server is previously registered in the radio base station. When a radio base station receives a frame addressed to a registered multicast IP address from a server, the radio base station uses the radio transmission rate suitable for the bit rate of data included in the frame to multicast the frame to a plurality of radio Send to the terminal. Each of the plurality of wireless terminals selects a bit rate of data to be received according to radio wave reception status with the wireless base station, and transmits an IGMP Join message including a multicast IP address corresponding to the data. Thus, each of the plurality of wireless terminals can receive data at a bit rate suitable for the radio wave reception state in real time while maintaining the reliability of frame transmission.

  However, the method disclosed in Patent Document 1 does not consider the occurrence of channel interference. For example, when the wireless terminal starts transmitting a frame, the wireless base station cannot transmit the frame itself. For this reason, while the wireless terminal is transmitting frames, frames waiting for transmission are accumulated in the wireless base station. As a result, it becomes difficult for the server to transmit data in real time.

  Further, in the method disclosed in Patent Document 2, when a radio base station transmits a frame by multicast, a time during which the channel is not used (hereinafter referred to as “channel unused time”) and a multicast IP address are addressed. Is selected based on the bit rate of the data transmitted to the multicast IP address. Specifically, the radio base station calculates a channel unused time per unit time. Furthermore, the radio base station uses the channel when an arbitrary radio transmission rate is selected for frame transmission based on the bit rate of data transmitted from the server addressed to the multicast IP address, and is less than the channel unused time. The wireless transmission rate is selected so that

  However, the method disclosed in Patent Document 2 does not consider the case where the channel unused time is extremely short. Specifically, when the channel use time when the fastest wireless transmission rate is selected for frame transmission exceeds the channel unused time, frames waiting for transmission are accumulated in the radio base station. For this reason, it becomes difficult for the server to transmit data in real time.

  In order to solve such a problem, a communication method according to an aspect of the present disclosure is provided for at least one or more wireless terminals connected to a wireless base station via a wireless network using an arbitrary channel. A communication method in a server that transmits a packet by multicast or broadcast via a radio base station, the step of generating the packet including data in which priority is set in advance, and the unit per unit time in the radio base station Obtaining a channel use time, which is a time during which a channel is used, and, based on the channel use time, in order for the radio base station to transmit the packet to the radio terminal, per unit time Calculating a channel usable time which is a time during which the channel can be used; and the radio base station Calculating a first expected channel usage time, which is a time expected to use the channel, to transmit the packet to the wireless terminal; and Calculating a wireless transmission rate to be applied when the wireless base station transmits the packet to the wireless terminal based on the priority of the data included in the packet, so that And transmitting information indicating the radio transmission rate to the radio base station.

  According to this aspect, the server controls the wireless transmission rate based on the priority of the data included in the packet so that the first expected channel use time is equal to or shorter than the channel usable time. For example, when the channel usable time is relatively short, the first wireless base station applies a higher wireless transmission rate when transmitting a packet including low priority data on the wireless network. The channel use expected time can be shortened and data can be transmitted in real time. On the other hand, for example, when the channel usable time is relatively long, when a wireless base station transmits a packet including high priority data on a wireless network, by applying a lower wireless transmission rate, The reliability of data transmission can be improved.

  For example, the communication method further includes a step of setting an initial value of the wireless transmission rate, and in the step of calculating the wireless transmission rate, the first expected channel use time exceeds the available channel time. In addition, the initial value of the wireless transmission rate may be changed based on the priority of the data included in a specific packet.

  According to this aspect, when the first expected channel use time exceeds the available channel time, the initial value of the radio transmission rate is changed based on the priority of data. For example, by changing the initial value of the radio transmission rate corresponding to low priority data to a higher value, the first expected channel use time can be made shorter than the available channel time, and data is transmitted in real time. can do.

  For example, in the generating step, the plurality of packets each including a plurality of data having different priorities are generated, and in the step of calculating the first expected channel use time, the radio base station In the step of calculating the first channel use expected time, which is a time expected to use the channel in order to transmit a packet to the wireless terminal, and calculating the wireless transmission rate, the first channel use When the expected time exceeds the channel usable time, the specific packet including the data having the lowest priority is extracted from the plurality of packets, and the wireless transmission rate corresponding to the specific packet is extracted. The initial value may be changed to a higher value.

  According to this aspect, when the first expected channel use time exceeds the channel usable time, the initial value of the radio transmission rate corresponding to a specific packet including data having the lowest priority is changed to a higher value. . As a result, the first expected channel use time can be made equal to or less than the available channel time, and data can be transmitted in real time.

  For example, in the communication method, the wireless base station further transmits a plurality of packets including the specific packet to the wireless terminal after changing the wireless transmission rate in the step of calculating the wireless transmission rate. Calculating a second expected channel use time that is expected to use the channel; and if the second expected channel use time exceeds the available channel time, the specific packet is Determining whether or not to transmit to the radio base station.

  According to this aspect, when the second expected channel usage time exceeds the channel usable time, it is determined whether or not to transmit a specific packet to the radio base station. For example, when the channel usable time is extremely short, the server can transmit high priority data in real time by not transmitting a specific packet including data having the lowest priority to the radio base station. .

  For example, the communication method may further include a step of discarding the specific packet when it is determined in the determining step that the specific packet is not transmitted to the radio base station.

  According to this aspect, it is possible to suppress the accumulation of the specific packet in the radio base station by discarding the specific packet.

  For example, in the transmitting step, an identifier indicating the wireless transmission rate may be assigned to the packet.

  According to this aspect, it is possible to transmit information indicating the wireless transmission rate to the wireless base station by a simple method.

  A radio base station according to an aspect of the present disclosure is a radio base station that is connected to a server via a network and connected to at least one or more radio terminals via a radio network using an arbitrary channel. A receiving unit that receives a packet from the server, a determination unit that determines a wireless transmission rate to be applied when the received packet is transmitted to the wireless terminal, and a multicast or A transmitter that transmits the broadcast to the wireless terminal; and a measuring unit that measures a channel use time, which is a time during which the channel is used per unit time, in addition to the transmission of the packet.

  Further, the server according to one aspect of the present disclosure multicasts a packet to at least one or more wireless terminals connected to the wireless base station via a wireless network using an arbitrary channel via the wireless base station. Or a broadcast transmission server that generates the packet including data for which priority is set in advance, and a channeled time that is the time during which the channel is used per unit time in the radio base station Based on the channel usage time, an acquisition unit that acquires a usage time, and a channel usage that is a time during which the channel can be used per unit time for the radio base station to transmit the packet to the radio terminal A first calculation unit for calculating a possible time; and for the wireless base station to transmit the packet to the wireless terminal Based on the priority of the data included in the packet so that the expected channel usage time that is expected to use the channel is calculated, and the expected channel usage time is equal to or less than the available channel time. A second calculation unit that calculates a radio transmission rate to be applied when the radio base station transmits the packet to the radio terminal, and transmits information indicating the packet and the radio transmission rate to the radio base station A transmission unit.

  In addition, a wireless distribution system according to an aspect of the present disclosure is connected to a server, a wireless base station connected to the server via a network, and a wireless network using an arbitrary channel with the wireless base station. In addition, at least one or more wireless terminals, the server includes a generation unit that generates a packet including data for which priority is set in advance, and the unit per unit time in the wireless base station. An acquisition unit that acquires a channel use time that is a time during which a channel is used, and based on the channel use time, the wireless base station transmits the packet to the wireless terminal per unit time. A first calculation unit for calculating a channel usable time, which is a time during which the channel can be used, and the radio base station The data included in the packet is calculated such that an expected channel use time that is expected to use the channel for transmission to a wireless terminal is calculated and the expected channel use time is less than or equal to the available channel time. A second calculation unit for calculating a radio transmission rate to be applied when the radio base station transmits the packet to the radio terminal based on the priority, and information indicating the packet and the radio transmission rate A first transmitter configured to transmit to the radio base station, wherein the radio base station determines the radio transmission rate based on the information received from the server and the receiver that receives the packet and the information. A second determination unit configured to transmit the packet to the wireless terminal by multicast or broadcast according to the determined wireless transmission rate; And a transmission unit.

  Note that these comprehensive or specific aspects may be realized by a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, and the system, method, integrated circuit, computer. You may implement | achieve with arbitrary combinations of a program or a recording medium.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  It should be noted that each of the embodiments described below shows a comprehensive or specific example. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment)
[1. Configuration of wireless distribution system]
First, the configuration of the wireless distribution system according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a wireless distribution system according to an embodiment.

  As shown in FIG. 1, the wireless distribution system includes a server 12, a wireless base station 13, and a plurality of wireless terminals 14a and 14b.

  The server 12 is connected to the wireless base station 13 via a wired network 10 (an example of a network). The server 12 multicasts a multicast packet (an example of a packet) including data for which priority (described later) is set in advance to the plurality of wireless terminals 14 a and 14 b via the wireless base station 13. The wired network 10 may be configured with one or more routers or one or more switches.

  The radio base station 13 constructs a radio network 11 using an arbitrary channel. The radio base station 13 receives the multicast packet from the server 12, and transmits the received multicast packet to the plurality of radio terminals 14a and 14b by multicast.

  Each of the plurality of wireless terminals 14 a and 14 b is connected to the wireless base station 13 via the wireless network 11. Each of the plurality of wireless terminals 14 a and 14 b receives a multicast packet from the wireless base station 13.

  Note that the server 12 and the wireless base station 13 may be realized as a single physical device without the wired network 10.

[2. Configuration of radio base station]
Next, the configuration of the radio base station 13 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the radio base station 13 according to the embodiment.

  As shown in FIG. 2, the radio base station 13 includes a wired communication unit 1301 (an example of a reception unit), a radio transmission rate setting unit 1302, a packet processing unit 1303 (an example of a determination unit), and a channel use time measurement. A unit 1304 (an example of a measurement unit) and a wireless communication unit 1305 (an example of a transmission unit and a second transmission unit).

  The wired communication unit 1301 is connected to the server 12 via the wired network 10. The wired communication unit 1301 receives a multicast packet from the server 12. Further, the wired communication unit 1301 transmits the channel use time (described later) measured by the channel use time measurement unit 1304 to the server 12.

  The wireless transmission rate setting unit 1302 associates the identifier included in the multicast packet received by the wired communication unit 1301 with the wireless transmission rate applied when transmitting the multicast packet on the wireless network 11. This association is performed via the wired network 10 or the wireless network 11. The identifiers are, for example, a) VLAN ID (Virtual LAN Identifier) defined in IEEE802.1Q included in the Ethernet frame and PCP (Priority Code Point), B) TOS (Type Of Service) included in the IPv4 header, C) It is at least one of the traffic class included in the IPv6 header, and d) the source port number and the destination port number included in the UDP header.

  The wireless transmission rate setting unit 1302 associates any wireless transmission rate among 6, 9, 13, 18, 24, 36, 48, and 54 Mbps based on, for example, the IEEE 802.11a standard. Note that the wireless transmission rate setting unit 1302 may associate the wireless transmission rate set in advance with a fixed value with the identifier of the multicast packet.

  When the packet processing unit 1303 transmits a multicast packet on the wireless network 11, the packet processing unit 1303 determines the wireless transmission rate associated with the wireless transmission rate setting unit 1302 based on the identifier included in the multicast packet.

  The channel use time measuring unit 1304 measures a channel use time which is a time during which a channel is used per unit time (for example, 100 msec) in addition to transmission of a multicast packet.

  The wireless communication unit 1305 is connected to the plurality of wireless terminals 14 a and 14 b via the wireless network 11. The wireless communication unit 1305 uses the wireless transmission rate determined by the packet processing unit 1303 to transmit multicast packets to the plurality of wireless terminals 14a and 14b by multicast.

[3. Server configuration]
Next, the configuration of the server 12 will be described with reference to FIGS. 3 and 4. FIG. 3 is a block diagram illustrating a configuration of the server 12 according to the embodiment. FIG. 4 is a diagram illustrating an example of the wireless transmission rate control management table 30.

  As illustrated in FIG. 3, the server 12 includes a data generation unit 1201, a packet generation unit 1202 (an example of a generation unit), a wireless transmission rate calculation unit 1203 (an example of a second calculation unit), and a packet transmission unit 1204. A channel usable time calculation unit 1205 (an example of a first calculation unit), a channel use time acquisition unit 1206 (an example of an acquisition unit), and a wired communication unit 1207 (an example of a transmission unit and a first transmission unit). ).

  The data generation unit 1201 generates data with a fixed priority set in advance. The priority is information indicating the priority of data transmission, and is composed of, for example, three levels of “high”, “medium”, and “low”. For example, when the priority set for data is “high”, the priority for transmitting the data is the highest. When the priority set for the data is “medium”, the priority for transmitting the data is the second highest. When the priority set for data is “low”, the priority for transmitting the data is the lowest.

  The packet generation unit 1202 generates a multicast packet that includes the data generated by the data generation unit 1201. Note that the multicast IP addresses designated as the destinations of the multicast packets in the server 12 may all be the same. As a result, when the wired network 10 is configured with one or more routers or one or more switches, the number of times and the time at which a distribution tree for transferring multicast packets on the wired network 10 is constructed, This is less than when multiple multicast IP addresses are used. As a result, the plurality of wireless terminals 14a and 14b can receive the multicast packet transmitted by the server 12 more quickly.

  The channel use time acquisition unit 1206 acquires the channel use time measured by the channel use time measurement unit 1304 of the radio base station 13 from the radio base station 13.

  Based on the channel use time acquired by the channel use time acquisition unit 1206, the channel usable time calculation unit 1205 can use the channel per unit time in order for the radio base station 13 to transmit a multicast packet. The channel usable time is calculated. Specifically, the channel usable time calculation unit 1205 calculates the channel usable time using, for example, the following Equation 1.

  In the above equation 1, “Tstable” is a channel usable time, “α” is a real number greater than 0 and equal to or less than 1, “T” is a unit time when the radio base station 13 measures the channel use time, This is the channel usage time. The channel use time may be an average value of the channel use time measured this time and the channel use time measured in the past.

  The radio transmission rate calculation unit 1203 calculates the expected channel usage time. The expected channel use time is the time when the radio base station 13 is expected to use a channel when transmitting a multicast packet to a plurality of radio terminals 14a and 14b using an arbitrary radio transmission rate. Specifically, the wireless transmission rate calculation unit 1203 uses the following equations 2 and 3 to calculate the expected channel usage time based on, for example, a standard defined in IEEE 802.11a.

  In Equation 2, Test is the expected channel usage time, N is the number of multicast packets including data for which priority is set, tDIFS is the DCF IFS (Inter Frame Space) time interval, and tbackoff is Contention. The average back-off time interval based on Windows, tPLCP_preamble is the time required for preamble transmission of PLCP (Physical Layer Convergence Protocol) on the wireless network 11, and tPLCP_signal is required for transmission of the signal part of the PLCP header on the wireless network 11. The time variable is variable from the service part of the PLCP header described later on the wireless network 11 to the padding. The bit is the time required when transmitted by wireless transmission rate.

  In Equation 3, SPLCP_service is the number of bits in the service portion of the PLCP header, SPSDU is the number of bits in MAC (Media Access Control) including multicast packets, and Protocol is the tail bit indicating the end of the frame. , Spading is the number of bits in the padding part, Ssymble is the number of bits per symbol when a frame is transmitted on the wireless network 11 using the wireless transmission rate, and tsymble is the wireless network 11. This is the time required to transmit one symbol.

  The wireless transmission rate calculation unit 1203 transmits the multicast packet based on the number and size of the multicast packets and the priority of the data included in the multicast packet so that the expected channel use time is less than the channel usable time. The wireless transmission rate applied at the time is calculated. At this time, the wireless transmission rate calculation unit 1203 is included in the multicast packet when the wireless transmission rate applied when transmitting the multicast packet cannot be calculated so that the expected channel use time is less than the channel usable time. It is determined whether or not to transmit a multicast packet to the radio base station 13 based on the data priority.

  Further, the wireless transmission rate calculation unit 1203 stores a wireless transmission rate control management table 30 in which information regarding multicast packets to be transmitted is stored. Here, the wireless transmission rate control management table 30 will be described with reference to FIG. As illustrated in FIG. 4, the wireless transmission rate control management table 30 includes a priority column 301, a control target column 302, a transmission target column 303, and a wireless transmission rate column 304.

  The priority column 301 stores the priority of data included in the multicast packet. In the example illustrated in FIG. 4, information “high” indicating the highest priority is stored in the first row of the priority column 301. In the second row of the priority column 301, information “medium” indicating the second highest priority is stored. In the third row of the priority column 301, information “low” indicating the lowest priority is stored.

  The control target column 302 stores information indicating whether or not it is a target for changing a wireless transmission rate applied when a multicast packet is transmitted. In the example illustrated in FIG. 4, the first row of the control target column 302 stores information “false” indicating that the wireless transmission rate applied when transmitting a multicast packet is not a target to be changed. In the second and third rows of the control target column 302, information “true” indicating that the wireless transmission rate to be applied when a multicast packet is transmitted is changed is stored.

  The transmission target column 303 stores information indicating whether a multicast packet is to be transmitted. In the example illustrated in FIG. 4, information “true” indicating that a multicast packet is to be transmitted is stored in the first, second, and third rows of the transmission target column 303.

  The wireless transmission rate column 304 stores information indicating a wireless transmission rate applied when transmitting a multicast packet. In the example illustrated in FIG. 4, information “OFDM6 Mbps” indicating that the wireless transmission rate is 6 Mbps is stored in the first row of the wireless transmission rate column 304. The second row of the wireless transmission rate column 304 stores information “OFDM12 Mbps” indicating that the wireless transmission rate is 12 Mbps. In the third row of the wireless transmission rate column 304, information “OFDM24 Mbps” indicating that the wireless transmission rate is 24 Mbps is stored.

  If the radio base station 13 always wants to transmit a multicast packet including data with an arbitrary priority set at an initial value of a predetermined radio transmission rate, the control target column 302 is set to “false”. In addition, the wireless transmission rate column 304 may be set to the initial value of the wireless transmission rate.

  Returning to FIG. 3, based on the calculation result of the wireless transmission rate calculation unit 1203, the packet transmission unit 1204 identifies an identifier corresponding to the wireless transmission rate (an example of information indicating the wireless transmission rate) for the multicast packet to be transmitted. Is granted.

  The wired communication unit 1207 is connected to the wireless base station 13 via the wired network 10. The wired communication unit 1207 transmits the multicast packet processed by the packet transmission unit 1204 to the radio base station 13. At this time, since the identifier corresponding to the wireless transmission rate is assigned to the multicast packet, the wired communication unit 1207 transmits the multicast packet to the wireless base station 13 to transmit information indicating the wireless transmission rate to the wireless base station 13. The station 13 is notified. Also, the wired communication unit 1207 receives the channel use time from the radio base station 13 and outputs the received channel use time to the channel use time acquisition unit 1206.

[4. Server processing]
Next, processing of the server 12 according to the embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing processing of the server 12 according to the embodiment. FIG. 6 is a flowchart specifically showing the wireless transmission rate changing process (S20) in FIG. 7A to 7C are diagrams for explaining an example of the wireless transmission rate change process in FIG.

  7A to 7C, in order to simplify the explanation, it is assumed that α = 1 in the above equation 1 and that the numbers and sizes of the multicast packets P1, P2, and P3 are the same.

  As shown in FIG. 5, first, the packet generator 1202 generates a multicast packet including the data generated by the data generator 1201 (S11). Specifically, as shown in FIGS. 7A to 7C, the priority of data is configured in three stages of “high”, “medium”, and “low”, and the packet generation unit 1202 has a priority of “high”. A multicast packet P1 including data, a multicast packet P2 including data of priority “medium”, and a multicast packet P3 including data of priority “low” are generated.

  The wireless transmission rate calculation unit 1203 calculates the number and size of multicast packets for each of the priority levels “high”, “medium”, and “low” of the data included in the multicast packets P1, P2, and P3 generated by the packet generation unit 1202. Is counted (S12).

  Next, the wireless transmission rate calculation unit 1203 has priority levels “high”, “medium”, and “data” included in the multicast packets P1, P2, and P3 in which the transmission target column 303 illustrated in FIG. For each “low”, initial values R1, R2 and R3 of the wireless transmission rate are set (S13). That is, the wireless transmission rate calculation unit 1203 sets the initial value R1 of the wireless transmission rate for the priority “high”, sets the initial value R2 of the wireless transmission rate for the priority “medium”, and sets the initial value R2 for the priority “low”. An initial value R3 of the radio transmission rate is set. For convenience of explanation, it is assumed that the initial values R1, R2 and R3 of the radio transmission rate are all the same value.

  Next, the channel use time acquisition unit 1206 acquires the channel use time Tused from the radio base station 13 (S14). The channel usable time calculation unit 1205 calculates the channel usable time Tustable based on the channel use time Tused acquired by the channel use time acquisition unit 1206 (S15).

  Next, the wireless transmission rate calculation unit 1203 determines the expected channel usage time (first time) based on the initial values R1, R2, and R3 of the wireless transmission rate and the numbers and sizes of the multicast packets P1, P2, and P3. An example of the estimated channel usage time is calculated (S16).

  Next, the wireless transmission rate calculation unit 1203 determines whether or not the expected channel use time is less than or equal to the channel usable time Tusable (S17). As illustrated in FIG. 7A, when the wireless transmission rate calculation unit 1203 determines that the expected channel use time Test_1 is equal to or shorter than the channel usable time Tusable (YES in S17), the wireless transmission rate initial values R1, R2 And R3 is left unchanged. The packet transmission unit 1204 assigns identifiers corresponding to the initial values R1, R2, and R3 of the wireless transmission rate to the multicast packets P1, P2, and P3, respectively. Accordingly, the wired communication unit 1207 transmits the multicast packets P1, P2, and P3 processed by the packet transmission unit 1204 to the radio base station 13 at the initial values R1, R2, and R3 of the radio transmission rate, respectively (S18).

  On the other hand, as shown in (a) of FIG. 7B and (a) of FIG. 7C, the wireless transmission rate calculation unit 1203 determines that the expected channel use time Test_2 exceeds the available channel time Tusable (in S17). NO), by searching the wireless transmission rate control management table 30, there is a priority of data included in the multicast packets P1, P2, and P3 in which the control target column 302 and the transmission target column 303 are both “true”. It is determined whether or not to perform (S19). That is, the wireless transmission rate calculation unit 1203 determines whether there is a multicast packet that is a control target for changing the wireless transmission rate and that is a transmission target.

  In the example shown in FIGS. 4, 7B, and 7C, the wireless transmission rate calculation unit 1203 determines that multicast packets P2 and P3 that are control targets and transmission targets exist (YES in S19). In this case, the wireless transmission rate changing process based on the priority is executed (S20). The wireless transmission rate change process will be described in detail later.

  On the other hand, the wireless transmission rate calculation unit 1203 is a control target and there is no multicast packet to be transmitted. In other words, the wireless transmission rate calculation unit 1203 includes all multicast packets P1, P2, and P3 in the wireless transmission rate control management table 30. If at least one of the control target column 302 and the transmission target column 303 is “false” with respect to the priority of the data to be processed (NO in S19), the process ends.

  Here, the above-described wireless transmission rate change process (S20) will be specifically described with reference to FIG. As illustrated in FIG. 6, the wireless transmission rate calculation unit 1203 searches the wireless transmission rate control management table 30 so that both the control target column 302 and the transmission target column 303 are “true”. A multicast packet (an example of a specific packet) including low data is extracted (S41). In the example shown in FIGS. 4, 7B, and 7C, the wireless transmission rate calculation unit 1203 extracts a multicast packet P3 including data with a priority “low”.

  Next, whether or not the wireless transmission rate calculation unit 1203 can change the initial value R3 of the wireless transmission rate corresponding to the priority “low” of the extracted multicast packet P3 to a higher value in the wireless transmission rate control management table 30. Is determined (S42). If the wireless transmission rate calculation unit 1203 determines that the initial value R3 of the wireless transmission rate can be changed to a higher value (YES in S42), the wireless transmission rate calculation unit 1203 sets the initial value R3 of the wireless transmission rate to a higher value R3 ′ ( R3 <R3 ′) (S43).

  Next, the wireless transmission rate calculation unit 1203 determines the expected channel usage time (based on the initial values R1, R2 and the change value R3 ′ of the wireless transmission rate and the numbers and sizes of the multicast packets P1, P2, and P3, respectively. An example of the second expected channel use time) is calculated (S44). Note that the method for calculating the expected channel use time in step S44 is the same as the method for calculating the expected channel use time in step S16 described above.

  Next, the wireless transmission rate calculation unit 1203 determines whether or not the expected channel use time is less than or equal to the channel usable time Tusable (S45). As illustrated in (b) of FIG. 7B, when the radio transmission rate calculation unit 1203 determines that the expected channel use time Test_3 is equal to or shorter than the channel available time Tusable (YES in S45), step S21 in FIG. In step S20, it is determined whether or not the multicast packet P3 including the data with the lowest priority has been discarded.

  Returning to FIG. 5, when the wireless transmission rate calculation unit 1203 determines that the multicast packet P3 including the data with the lowest priority is not discarded (NO in S21), the wireless transmission rate is transmitted to the packet transmission unit 1204. The initial values R1, R2 and the changed value R3 ′ are notified. The packet transmission unit 1204 assigns identifiers corresponding to the initial values R1 and R2 of the wireless transmission rate to the multicast packets P1 and P2, and corresponds to the change value R3 ′ of the wireless transmission rate to the multicast packet P3. Give an identifier. As a result, the wired communication unit 1207 transmits the multicast packets P1 and P2 to the radio base station 13 with the initial values R1 and R2 of the radio transmission rate, respectively, and wirelessly transmits the multicast packet P3 with the change value R3 ′ of the radio transmission rate. It transmits to the base station 13 (S18).

  Returning to step S45 in FIG. 6, as illustrated in (b) in FIG. 7C, the wireless transmission rate calculation unit 1203 determines that the estimated channel use time Test_4 exceeds the channel usable time Tusable (NO in S45). ), The process returns to step S42. Thereby, the wireless transmission rate calculation unit 1203 determines whether or not the wireless transmission rate change value R3 ′ corresponding to the priority “low” of the multicast packet P3 can be changed to a higher value (S42). The wireless transmission rate calculation unit 1203 repeatedly executes the processes in steps S42 to S45 described above until the estimated channel use time becomes equal to or less than the channel usable time Tusable.

  On the other hand, when the wireless transmission rate calculation unit 1203 determines that the initial value R3 or the change value R3 ′ of the wireless transmission rate corresponding to the priority “low” of the multicast packet P3 cannot be changed to a higher value (in S42). NO), as shown in (c) of FIG. 7C, the multicast packet P3 including the data with the lowest priority is excluded from transmission targets (S46). Specifically, the wireless transmission rate calculation unit 1203 changes the transmission target column 303 corresponding to the priority “low” from “true” to “false” in the wireless transmission rate control management table 30. In addition, as a case where the initial value R3 or change value R3 ′ of the radio transmission rate corresponding to the priority “low” of the multicast packet P3 cannot be changed to a higher value, for example, the initial value R3 or change value R3 ′ of the radio transmission rate Is the upper limit of 54 Mbps in the IEEE 802.11a standard. The wireless transmission rate calculation unit 1203 discards the multicast packet P3 including the lowest priority data excluded from the transmission target (S47), and proceeds to step S21 in FIG.

  Returning to FIG. 5, when the wireless transmission rate calculation unit 1203 determines in step S20 that the multicast packet P3 including the data with the lowest priority has been discarded (YES in S21), the wireless transmission rate calculation unit 1203 returns to step S16 and returns to the wireless transmission rate. Based on the initial values R1 and R2 and the numbers and sizes of the multicast packets P1 and P2, the estimated channel use time Test_5 is calculated (S16). As shown in (c) of FIG. 7C, when the estimated channel use time Test_5 is equal to or shorter than the channel available time Tusable (YES in S17), the packet transmission unit 1204 transmits wireless data to the multicast packets P1 and P2. Identifiers corresponding to the initial values R1 and R2 of the transmission rate are respectively assigned. As a result, the wired communication unit 1207 transmits the multicast packets P1 and P2 to the radio base station 13 at the initial values R1 and R2 of the radio transmission rate, respectively (S18).

  If the expected channel use time Test_5 exceeds the available channel time Tusable (NO in S17), the above steps S16, S17 and S20 to S21 are performed until the expected channel use time becomes equal to or less than the usable channel time Tusable. Each process is repeatedly executed.

[5. effect]
As described above, the server 12 controls the wireless transmission rate based on the priority of the data included in the multicast packet so that the expected channel use time is less than the channel usable time. For example, when the channel usable time is relatively short, when the wireless base station 13 transmits a packet including low priority data on the wireless network 11, by applying a higher wireless transmission rate, The expected channel usage time can be shortened. As a result, data can be transmitted in real time.

(Other variations)
As mentioned above, although the communication method etc. which concern on the one or several aspect were demonstrated based on the said embodiment, this indication is not limited to the said embodiment. Unless it deviates from the gist of the present disclosure, various modifications conceived by those skilled in the art have been made in the embodiments, and forms constructed by combining components in different embodiments are also within the scope of one or more aspects. May be included.

  In the above embodiment, the case where the server 12 multicasts multicast packets to a plurality of wireless terminals 14a and 14b has been described. However, the present invention is not limited to this. For example, a broadcast packet (an example of a packet) is transmitted to a plurality of wireless terminals 14a. And 14b may be broadcast.

  In the above embodiment, the case where the wireless distribution system includes the two wireless terminals 14a and 14b has been described. However, the present invention is not limited to this, and for example, one or three or more wireless terminals may be included.

  In the above embodiment, the priority is configured with three levels of “high”, “medium”, and “low”. However, the priority is not limited to this, and for example, the priority may be configured with two levels or four or more levels. .

  In each of the above embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. Here, the software that realizes the server and the like of each of the above embodiments is the following program.

  That is, this program obtains, in a computer, a step of generating a packet including data for which priority is set in advance, and a channel use time that is a time during which a channel is used per unit time in a radio base station. And a step of calculating a channel available time, which is a time during which the channel can be used per unit time, in order for the radio base station to transmit a packet to the radio terminal based on the channel use time; Calculating a first expected channel usage time, which is a time expected to use the channel, to transmit a packet to the wireless terminal, and so that the first expected channel usage time is less than or equal to the available channel time Based on the priority of data contained in the packet, the wireless base station transmits the packet to the wireless terminal. Calculating a wireless transmission rate to be applied in, and a step of transmitting information indicating the packet and the wireless transmission rate to the radio base station.

  A part or all of the constituent elements constituting each of the above devices may be constituted by an IC card or a single module that can be attached to and detached from each device. The IC card or the module is a computer system including a microprocessor, a ROM, a RAM, and the like. The IC card or the module may include the super multifunctional LSI described above. The IC card or the module achieves its function by the microprocessor operating according to the computer program. This IC card or this module may have tamper resistance.

  The present invention may be the method described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the computer program. The present invention also provides a computer readable recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray (registered)). (Trademark) Disc), or recorded in a semiconductor memory or the like. Further, the digital signal may be recorded on these recording media. Further, the present invention may transmit the computer program or the digital signal via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like. The present invention may also be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program. In addition, the program or the digital signal is recorded on the recording medium and transferred, or the program or the digital signal is transferred via the network or the like, and is executed by another independent computer system. It is also good.

  The communication method, the radio base station, the server, and the radio distribution system according to the present disclosure are useful for, for example, a system for distributing a dynamic map indicating road conditions to an autonomous driving vehicle in real time.

DESCRIPTION OF SYMBOLS 10 Wired network 11 Wireless network 12 Server 13 Wireless base station 14a, 14b Wireless terminal 30 Wireless transmission rate control management table 301 Priority column 302 Control target column 303 Transmission target column 304 Wireless transmission rate column 1201 Data generation unit 1202 Packet generation unit 1203 Wireless transmission rate calculation unit 1204 Packet transmission unit 1205 Channel available time calculation unit 1206 Channel usage time acquisition unit 1207, 1301 Wired communication unit 1302 Wireless transmission rate setting unit 1303 Packet processing unit 1304 Channel usage time measurement unit 1305 Wireless communication unit P1, P2, P3 multicast packets

Claims (9)

A communication method in a server for transmitting a packet by multicast or broadcast to at least one wireless terminal connected to a wireless base station via a wireless network using an arbitrary channel via the wireless base station. ,
Generating the packet including data with priorities set in advance;
Obtaining a channel use time which is a time during which the channel is used per unit time in the radio base station;
Calculating a channel usable time, which is a time during which the channel can be used per unit time, in order for the wireless base station to transmit the packet to the wireless terminal based on the channel-used time;
Calculating a first expected channel use time that is expected to use the channel for the radio base station to transmit the packet to the radio terminal;
When the radio base station transmits the packet to the radio terminal based on the priority of the data included in the packet so that the first channel use expected time is equal to or less than the channel usable time. Calculating a radio transmission rate to be applied to
Transmitting information indicating the packet and the wireless transmission rate to the wireless base station. The communication method further includes a step of setting an initial value of the wireless transmission rate,
In the step of calculating the wireless transmission rate, when the estimated first channel use time exceeds the channel usable time, the wireless transmission rate is calculated based on the priority of the data included in a specific packet. The communication method according to claim 1, wherein the initial value is changed. In the generating step, a plurality of the packets each including a plurality of data having different priorities are generated,
In the step of calculating the first expected channel use time, the first channel use is a time at which the radio base station is expected to use the channel to transmit the plurality of packets to the radio terminal. Calculate the expected time,
In the step of calculating the radio transmission rate, the specific packet including the data having the lowest priority among the plurality of packets when the first expected channel use time exceeds the channel usable time. The communication method according to claim 2, wherein the initial value of the wireless transmission rate corresponding to the specific packet is changed to a higher value. The communication method further includes:
After changing the wireless transmission rate in the step of calculating the wireless transmission rate, the wireless base station is expected to use the channel to transmit a plurality of the packets including the specific packet to the wireless terminal. Calculating a second expected channel use time that is
The step of determining whether or not to transmit the specific packet to the radio base station when the second expected channel use time exceeds the channel usable time. Communication method. The communication method according to claim 4, further comprising a step of discarding the specific packet when the determination step determines that the specific packet is not transmitted to the radio base station. The communication method according to claim 1, wherein, in the transmitting step, an identifier indicating the wireless transmission rate is assigned to the packet. A wireless base station connected to a server via a network and connected to at least one or more wireless terminals via a wireless network using an arbitrary channel;
A receiving unit for receiving packets from the server;
A determination unit that determines a wireless transmission rate to be applied when transmitting the received packet to the wireless terminal;
A transmission unit that transmits the packet to the wireless terminal by multicast or broadcast according to the wireless transmission rate;
In addition to the transmission of the packet, a radio base station comprising: a measuring unit that measures a channel use time that is a time during which the channel is used per unit time. A server that transmits a packet by multicast or broadcast via the radio base station to at least one or more radio terminals connected to the radio base station via a radio network using an arbitrary channel,
A generating unit that generates the packet including data in which priority is set in advance;
An acquisition unit that acquires a channel use time that is a time during which the channel is used per unit time in the radio base station;
A first calculation for calculating a channel available time that is a time during which the channel can be used per unit time in order for the radio base station to transmit the packet to the radio terminal based on the channel use time And
Calculate a channel use expected time, which is a time when the radio base station is expected to use the channel to transmit the packet to the radio terminal, so that the channel use expected time is equal to or less than the channel usable time. A second calculation unit that calculates a radio transmission rate applied when the radio base station transmits the packet to the radio terminal based on the priority of the data included in the packet;
A transmission unit that transmits information indicating the packet and the wireless transmission rate to the wireless base station. A wireless distribution system comprising: a server; a wireless base station connected to the server via a network; and at least one or more wireless terminals connected to the wireless base station via a wireless network using an arbitrary channel Because
The server
A generation unit that generates a packet including data in which priority is set in advance;
An acquisition unit that acquires a channel use time that is a time during which the channel is used per unit time in the radio base station;
A first calculation for calculating a channel available time that is a time during which the channel can be used per unit time in order for the radio base station to transmit the packet to the radio terminal based on the channel use time And
Calculate a channel use expected time, which is a time when the radio base station is expected to use the channel to transmit the packet to the radio terminal, so that the channel use expected time is equal to or less than the channel usable time. A second calculation unit that calculates a radio transmission rate applied when the radio base station transmits the packet to the radio terminal based on the priority of the data included in the packet;
A first transmitter that transmits information indicating the packet and the wireless transmission rate to the wireless base station, and
The radio base station is
A receiving unit for receiving the packet and the information from the server;
A determination unit for determining the wireless transmission rate based on the information;
A second transmission unit configured to transmit the packet to the wireless terminal by multicast or broadcast according to the determined wireless transmission rate.

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