JP5855551B2 - Wireless communication system and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication system and a wireless communication method in which a plurality of wireless LAN standard base stations and wireless LAN terminals sharing the same frequency resource in a target area perform wireless communication with a priority according to the wireless LAN standard. . Here, as wireless LAN standards sharing the same frequency resource, for example, there are IEEE802.11b, IEEE802.11g, IEEE802.11n, and the like.

  In a wireless communication system, a standard having a higher transmission speed while maintaining backward compatibility with the wireless LAN standard is standardized and shares the same frequency resource. In the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method that realizes wireless communication evenly for such wireless LAN terminals compliant with the wireless LAN standard, a DCF (Distributed Coordination Function) transmission method is adopted. . Each wireless LAN terminal performs carrier sense of the channel before transmission, generates a random number from the contention window (CW) range when the channel is idle, and only a period (backoff time) corresponding to the random number. Wait, recheck that the channel is idle and send the packet. When the channel becomes busy before the back-off time period elapses, no packet is transmitted, and when the channel becomes idle next time, carrier sensing is performed according to the remaining waiting time.

  On the other hand, the base station that has received the packet normally transmits an ACK signal to notify the wireless LAN terminal that is the transmission source of the fact. Therefore, if the ACK signal is not received within a predetermined time, the wireless LAN terminal that is the transmission source determines that transmission has failed and expands the CW, thereby expanding the range for generating random numbers and performing retransmission processing. Do. That is, whenever the number of retransmissions increases, it is determined that the channel is congested, and collision avoidance is performed by expanding the CW.

  However, in wireless LAN communication, a state in which the wireless signals do not reach each other (a radio wave environment in which carrier sense does not function) may occur due to the distance between radio stations or the influence of obstacles that do not transmit radio waves. In this case, since carrier sense does not function effectively, in the CSMA / CA system, the frequency of frame collision increases, which causes a deterioration in throughput characteristics.

  Therefore, in the wireless LAN standard, a countermeasure function called RTS (Request to Send) / CTS (Clear to Send) is defined to cope with a propagation environment in which carrier sense does not function effectively.

FIG. 4 shows an operation procedure of RTS / CTS.
In FIG. 4, before transmitting a data frame, terminal A carries out carrier sense of the backoff time in addition to DIFS, and transmits RTS to the base station that is the destination of the data frame. Since the terminal A and the terminal B are in a propagation environment where carrier sense can be performed, the terminal B also receives the RTS transmitted by the terminal A. The RTS and CTS frames have a duration field in which the reservation period for using the channel is described. The terminal B prohibits transmission only during the NAV (Network Allocation Vector) period set by the reservation signal of the RTS frame to prevent collision. To do. However, it is assumed that this RTS does not reach the terminal C.

  The base station that is the destination of the data frame returns a CTS to terminal A after a SIFS time interval after receiving the RTS. Since the CTS transmitted by the base station can also be received by the terminal C, the terminal C prohibits transmission for the NAV period set by the reservation signal of the CTS frame to prevent collision. The terminal A that has received the CTS transmits a data frame after the SIFS time, and the base station that has received the data frame also transmits an ACK signal after the SIFS time and ends the communication. Here, since SIFS and DIFS have a relationship of SIFS <DIFS, by giving priority using SIFS for a short time, once RTS is normally received, the frame is disturbed during the subsequent procedure. The data frame and the ACK signal are exchanged without any change.

  The terminal A that is the transmission source of the data frame and the peripheral radio stations (terminal B and terminal C) other than the base station that is the reception destination use the radio line for the period described in the duration field after receiving the RTS or CTS. Therefore, transmission is prohibited during the NAV period set by the reservation signal to prevent a collision.

IEEE standard for Local and metropolitan area networks Part 11: Wireless LAN MAC and PHY Specifications, June 2007

  In recent wireless communication systems, a large number of base stations and wireless LAN terminals of various wireless LAN standards exist in a target area and become denser. In particular, when the same frequency resource is shared, the frequency of frame collisions As a result, throughput characteristics are significantly degraded. On the other hand, since the existing access method (CSMA / CA) is equal to various wireless LAN standards, QoS control for each wireless LAN standard cannot be performed.

  The present invention performs QoS control by setting priority and channel utilization for each wireless LAN standard within a target area where a plurality of wireless LAN standard base stations and wireless LAN terminals sharing the same frequency resource exist. An object of the present invention is to provide a wireless communication system and a wireless communication method.

A first aspect of the present invention is a plurality of base stations and the wireless LAN terminal to share the same frequency resources in a wireless communication system that performs wireless LAN terminal and the wireless communication corresponding to the wireless LAN standard in which each base station uses each one The base station of the wireless LAN standard designates the NAV period based on the priority and the channel utilization rate according to the one wireless LAN standard for the base station and the wireless LAN terminal that perform wireless communication with another wireless LAN standard. And a base station that has transmitted the reservation signal performs wireless communication with a wireless LAN terminal corresponding to one wireless LAN standard during the NAV period specified by the reservation signal , Base stations and wireless LAN terminals that perform wireless communication according to other wireless LAN standards receive the reservation signal and prohibit transmission during the NAV period specified by the reservation signal.

  In the wireless communication system of the first invention, the reservation signal is set with a NAV period having a length corresponding to the priority and channel utilization rate for each wireless LAN standard.

  In the wireless communication system of the first invention, the reservation signal is transmitted at a transmission rate corresponding to the priority and channel utilization rate for each wireless LAN standard.

  In the wireless communication system of the first invention, each base station of each wireless LAN standard transmits and receives a notification signal for reporting the wireless LAN standard supported by each other, and the priority and channel according to the wireless LAN standard supported by the base station This is a configuration for setting the utilization rate.

A second invention is, a plurality of base stations and the wireless LAN terminal to share the same frequency resources in a wireless communication method for performing wireless LAN terminal and the wireless communication corresponding to the wireless LAN standard in which each base station uses each one The base station of the wireless LAN standard designates the NAV period based on the priority and the channel utilization rate according to the one wireless LAN standard for the base station and the wireless LAN terminal that perform wireless communication with another wireless LAN standard. Then, the base station that has transmitted the reservation signal for reserving the channel performs wireless communication with the wireless LAN terminal corresponding to one wireless LAN standard during the NAV period specified by the reservation signal, and transmits the other wireless signal. A base station and a wireless LAN terminal that perform wireless communication in accordance with the LAN standard receive a reservation signal and prohibit transmission during the NAV period designated by the reservation signal.

  In the wireless communication method of the second invention, the reservation signal is set with a NAV period having a length corresponding to the priority and channel utilization factor for each wireless LAN standard.

  In the wireless communication method of the second invention, the reservation signal is transmitted at a transmission rate corresponding to the priority and channel utilization rate for each wireless LAN standard.

  In the wireless communication method of the second invention, the base stations of each wireless LAN standard transmit and receive a notification signal for notifying the wireless LAN standard supported by each other, and the priority and channel according to the wireless LAN standard supported by the base station Set the usage rate.

  The present invention uses a reservation signal in which a NAV period is designated corresponding to the priority and channel utilization rate set for each wireless LAN standard, so that priority transmission and transmission according to the NAV period for each wireless LAN standard are performed. Prohibition is controlled. As a result, QoS control for each wireless LAN standard becomes possible, and a good communication environment can be realized and throughput can be improved.

It is a figure which shows the structural example of the base station in the radio | wireless communications system of this invention. 5 is a flowchart showing an example of processing of a wireless LAN standard control unit 4; It is a time chart which shows the operation example of the radio | wireless communications system of this invention. It is a time chart which shows the operation | movement procedure of RTS / CTS.

  The wireless communication system according to the present invention includes a plurality of base stations and wireless LAN terminals. Each base station supports only one wireless LAN standard, and here, it will be described as any one of IEEE802.11b, IEEE802.11g, and IEEE802.11n sharing the same frequency resource. Each wireless LAN terminal corresponding to each wireless LAN standard communicates with a base station that supports the same wireless LAN standard.

FIG. 1 shows a configuration example of a base station in a wireless communication system of the present invention.
In FIG. 1, the base station includes a data signal input / output unit 1, a broadcast signal generation unit 2, a reservation signal generation unit 3, a wireless LAN standard control unit 4, a transmission / reception control unit 5, and an antenna 6. The data signal input / output unit 1, the notification signal generation unit 2, and the reservation signal generation unit 3 are connected to the transmission / reception control unit 5 via the wireless LAN standard control unit 4.

  The data signal input / output unit 1 performs input / output processing of data signals transmitted and received according to the supported wireless LAN standard. The notification signal generation unit 2 performs notification signal generation processing for notifying information related to the supported wireless LAN standard. The reservation signal generator 3 generates a reservation signal (NAV) for reserving a channel. The transmission / reception control unit 5 performs transmission / reception processing of the notification signal, the reservation signal, and the data signal via the antenna 6. Note that the broadcast signal and the reservation signal are signals that can be transmitted and received with each other regardless of the wireless LAN standard supported by each base station.

  As shown in FIG. 2, the wireless LAN standard control unit 4 recognizes each wireless LAN standard notified from each base station by a broadcast signal, and priorities and channels according to the wireless LAN standard supported by the base station. A utilization rate is set, and transmission / reception control of a reservation signal and a data signal based on the priority and the channel utilization rate is performed. In this embodiment, it is assumed that the NAV period having a length corresponding to the channel utilization rate is set as the reserved signal. For example, when IEEE802.11n, IEEE802.11g, and IEEE802.11b are set in order from the wireless LAN standard with the highest priority, IEEE802.11n can transmit and receive data signals for four times, and IEEE802.11n. In 11g, a data signal can be transmitted and received twice, and in IEEE802.11b, a NAV period in which data signal can be transmitted and received once is set.

FIG. 3 shows an operation example of the wireless communication system of the present invention.
In FIG. 3, the base station 10 of the wireless LAN standard IEEE802.11n, the base station 20 of the wireless LAN standard IEEE802.11g, and the base station 30 of the wireless LAN standard IEEE802.11b each notify information related to the supported wireless LAN standard. Send a signal periodically. Each base station recognizes each wireless LAN standard notified by the broadcast signal, and sets a priority and a NAV period corresponding to the channel utilization rate according to the wireless LAN standard supported by the base station.

  On the other hand, the wireless LAN terminal recognizes the wireless LAN standard supported by each base station from the notification signal, thereby recognizing the base station that matches the wireless LAN standard of the terminal itself and specifying the base station that performs communication. Here, the base station 10 and the wireless LAN terminals 11 and 12 communicate with the wireless LAN standard IEEE802.11n, the base station 20 and the wireless LAN terminals 21 and 22 communicate with the wireless LAN standard IEEE802.11g, and the base station 30 wirelessly. The LAN terminal 31 communicates with the wireless LAN standard IEEE802.11g.

  First, the base station 10 of the first priority wireless LAN standard IEEE802.11n transmits a reservation signal in which a NAV period for transmitting and receiving data signals for four times is set. The reservation signal is also received by the base station 20 and the wireless LAN terminals 21 and 22, the base station 30 and the wireless LAN terminal 31 of other wireless LAN standards, and the base stations 20 and 30 and the wireless LAN terminals 21, 22 and 31 are received. Then, transmission of the NAV period by the reservation signal is prohibited.

  On the other hand, the wireless LAN terminals 11 and 12 under the base station 10 ignore the reservation signal transmitted by the base station 10. That is, the NAV period by the reservation signal is set in the base station 20 and the wireless LAN terminals 21 and 22 of other wireless LAN standards, the base station 30 and the wireless LAN terminal 31, and the base station 10 of the wireless LAN standard IEEE802.11n. 4 data signals can be preferentially transmitted and received between the wireless LAN terminals 11 and 12. In FIG. 3, DIFS, SIFS, back-off, ACK, etc. are omitted, and only the data signal is displayed. The same applies hereinafter.

  Next, when the NAV period set by the base station 10 ends, the base station 20 of the second priority wireless LAN standard IEEE802.11g transmits a reservation signal in which the NAV period for transmitting and receiving three data signals is set. To do. This reservation signal is also received by the base station 10 and the wireless LAN terminals 11 and 12, the base station 30 and the wireless LAN terminal 31 of other wireless LAN standards, and the base stations 10 and 30 and the wireless LAN terminals 11, 12, 31. Then, transmission of the NAV period by the reservation signal is prohibited.

  On the other hand, the wireless LAN terminals 21 and 22 under the base station 20 ignore the reservation signal transmitted by the base station 20. That is, the NAV period by the reservation signal is set in the base station 10 and the wireless LAN terminals 11 and 12 of other wireless LAN standards, the base station 30 and the wireless LAN terminal 31, and the base station 20 of the wireless LAN standard IEEE802.11g. And wireless LAN terminals 21 and 22 can preferentially transmit and receive data signals for three times.

  Next, when the NAV period set by the base station 20 ends, the base station 30 of the third priority wireless LAN standard IEEE802.11b transmits a reservation signal in which the NAV period for transmitting and receiving one data signal is set. To do. The reservation signal is also received by the base station 10 and the wireless LAN terminals 11 and 12 of the other wireless LAN standards, the base station 20 and the wireless LAN terminals 21 and 22, and the base stations 10 and 20 and the wireless LAN terminals 11 and 12 are received. , 21 and 22 prohibit transmission of the NAV period by the reservation signal.

  On the other hand, the wireless LAN terminal 31 under the base station 30 ignores the reservation signal transmitted by the base station 30. That is, the NAV period by the reservation signal is set in the base station 10 and the wireless LAN terminals 11 and 12 of the other wireless LAN standards and the base station 20 and the wireless LAN terminals 21 and 22, and the base of the wireless LAN standard IEEE802.11b is set. A data signal for one time can be preferentially transmitted and received between the station 30 and the wireless LAN terminal 31.

  Similarly, the reservation signals are repeatedly transmitted in the order of priority of the base stations 10, 20, and 30, and data signals can be transmitted and received preferentially during the NAV period set for each wireless LAN standard.

  In the embodiment described above, the example in which the length of the NAV period is set as the priority and the channel usage rate according to the wireless LAN standard has been shown. However, for example, the NAV period set by one reservation signal is constant, The transmission ratio of the reservation signal may be set so as to correspond to the priority and the channel usage rate according to the wireless LAN standard.

DESCRIPTION OF SYMBOLS 1 Data signal input / output part 2 Information signal generation part 3 Reservation signal generation part 4 Wireless LAN standard control part 5 Transmission / reception part 6 Antenna 10, 20, 30 Base station 11, 12, 21, 22, 31 Wireless LAN terminal

Claims (8)

In a wireless communication system in which a plurality of base stations and a wireless LAN terminal share the same frequency resource, and wireless communication is performed with a wireless LAN terminal corresponding to the wireless LAN standard used by each base station ,
A base station of one wireless LAN standard has a NAV period based on a priority and a channel utilization rate according to the one wireless LAN standard, with respect to a base station and a wireless LAN terminal that perform wireless communication with another wireless LAN standard. A means for transmitting a reservation signal for specifying and reserving a channel ;
The base station that has transmitted the reservation signal performs wireless communication with a wireless LAN terminal corresponding to the one wireless LAN standard during the NAV period specified by the reservation signal ,
A base station and a wireless LAN terminal that perform wireless communication according to the other wireless LAN standards receive the reservation signal and prohibit transmission during the NAV period specified by the reservation signal. The wireless communication system according to claim 1, wherein
The reservation signal is set with a NAV period having a length corresponding to a priority and a channel usage rate for each wireless LAN standard. The wireless communication system according to claim 1, wherein
The wireless communication system, wherein the reservation signal is transmitted at a transmission rate corresponding to a priority and a channel usage rate for each wireless LAN standard. The wireless communication system according to claim 1, wherein
Each of the wireless LAN standard base stations is configured to transmit and receive a notification signal for notifying each other of the wireless LAN standards supported by each other, and to set a priority and a channel usage rate according to the wireless LAN standard supported by the base station. A wireless communication system. In a wireless communication method in which a plurality of base stations and wireless LAN terminals share the same frequency resource and wireless communication is performed with wireless LAN terminals corresponding to wireless LAN standards used by each base station ,
A base station of one wireless LAN standard has a NAV period based on a priority and a channel utilization rate according to the one wireless LAN standard, with respect to a base station and a wireless LAN terminal that perform wireless communication with another wireless LAN standard. Send a reservation signal to reserve the channel by specifying ,
The base station that has transmitted the reservation signal performs wireless communication with a wireless LAN terminal corresponding to the one wireless LAN standard during the NAV period specified by the reservation signal ,
A base station and a wireless LAN terminal that perform wireless communication in accordance with the other wireless LAN standard receive the reservation signal and prohibit transmission during a NAV period specified by the reservation signal. The wireless communication method according to claim 5, wherein
The reservation signal is set with a NAV period having a length corresponding to the priority and channel utilization rate for each wireless LAN standard. The wireless communication method according to claim 5, wherein
The wireless communication method, wherein the reservation signal is transmitted at a transmission rate corresponding to a priority and a channel usage rate for each wireless LAN standard. The wireless communication method according to claim 5, wherein
Each of the wireless LAN standard base stations transmits and receives a notification signal for reporting a wireless LAN standard supported by each other, and sets a priority and a channel usage rate according to the wireless LAN standard supported by the base station. Wireless communication method.

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