KR102133465B1 - Method for transmitting and receiving frame in wireless local area network system and apparatus for the same - Google Patents

Abstract

Disclosed is a method and apparatus for transmitting and receiving frames in a wireless LAN system. The method of generating a list of interference/non-interference stations comprises: receiving a first frame from a second station, obtaining a receiver address of a first frame from a first frame, and a preset time from the time when the reception of the first frame is completed. And setting the third station as an interfering station or a non-interfering station based on whether the second frame, which is the response of the first frame, is received from the third station indicated by the receiver address. Therefore, the performance of the communication system can be improved.

Description

METHOD FOR TRANSMITTING AND RECEIVING FRAME IN WIRELESS LOCAL AREA NETWORK SYSTEM AND APPARATUS FOR THE SAME}

The present invention relates to a frame transmission and reception technology in a wireless LAN system, and more particularly, to a frame transmission and reception technology in an exposed node state or a blocked node state.

With the development of information and communication technology, various wireless communication technologies have been developed. Among them, a wireless local area network (WLAN) is a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), smart based on radio frequency technology. It is a technology that allows you to access the Internet wirelessly at home, at a business, or in a specific service providing area using a portable terminal such as a smart phone or a tablet PC.

The standard for wireless LAN technology is being developed as an IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard. The wireless LAN technology according to the IEEE 802.11a standard operates based on an orthogonal frequency division multiplexing (OFDM) method, and can provide a transmission speed of up to 54 Mbps in the 5 GHz band. The wireless LAN technology according to the IEEE 802.11b standard operates based on a direct sequence spread spectrum (DSSS) method and can provide a transmission speed of up to 11 Mbps in the 2.4 GHz band. The wireless LAN technology according to the IEEE 802.11g standard operates based on an OFDM method or a DSSS method, and can provide a transmission speed of up to 54 Mbps in the 2.4 GHz band.

The wireless LAN technology according to the IEEE 802.11n standard operates in the 2.4 GHz band and the 5 GHz band based on the OFDM scheme, and when using the multiple input multiple output-OFDM (MIMO-OFDM) scheme, four spatial streams ( It is possible to provide transmission speeds of up to 300 Mbps for spatial streams. The wireless LAN technology according to the IEEE 802.11n standard can support a channel bandwidth of up to 40 MHz, and in this case, a transmission speed of up to 600 Mbps.

As the spread of such a wireless LAN is activated and applications using it are diversified, the need for a new wireless LAN technology to support a higher throughput than the data processing speed supported by IEEE 802.11n is increasing. Very high throughput (VHT) wireless LAN technology is one of the IEEE 802.11 wireless LAN technologies proposed to support a data processing speed of 1 Gbps or higher. Among them, IEEE 802.11ac is being developed as a standard for providing ultra high throughput in the 5 GHz or lower band, and IEEE 802.11ad is being developed as a standard for providing ultra high throughput in the 60 GHz band.

In a system based on such a wireless LAN technology, there is a problem in that the performance of the wireless LAN system is deteriorated due to exposed nodes and blocked nodes.

An object of the present invention for solving the above problems is to provide a method for transmitting and receiving a frame in an exposed node state.

Another object of the present invention for solving the above problems is to provide a method for transmitting and receiving a frame in a blocking node state.

A method of generating a list of interference/non-interference stations performed in a first station according to an embodiment of the present invention for achieving the above object comprises: receiving a first frame from a second station, and receiving the first frame from the first frame Obtaining a receiver address of a frame, based on whether a second frame, which is the response of the first frame, is received from a third station indicated by the receiver address within a preset time from the time when the reception of the first frame is completed, And setting the third station as an interfering station or a non-interfering station.

Here, the setting of the interference station or the non-interference station may set the third station as the interference station when the second frame is normally received within the preset time from the third station.

Here, the setting of the interference station or the non-interference station may set the third station as a non-interference station if the second frame is not normally received within the preset time from the third station.

Here, the method of generating a list of interference/non-interference stations further includes generating a list of interference/non-interference stations including the third station identification information and received power information of the second frame measured by the first station. can do.

Here, the first frame may be a probe request frame, an authentication request frame, a connection request frame, a reconnection request frame, an RTS frame, a data frame, or a BAR frame.

Here, the preset time may be SIFS.

A frame transmission method performed in a first station according to another embodiment of the present invention for achieving the above object comprises: receiving a first frame from a second station, and receiving a receiver address of the first frame from the first frame. And determining whether the third station indicated by the receiver address is an interfering station or a non-interfering station based on the acquiring step and the pre-generated interference/non-interference station list.

Here, the first frame may be an RTS frame, a data frame, or a BAR frame.

Here, the interference station list of the interference / non-interference station list includes at least one station that transmits the response of the first frame within a first preset time, the non-interference station list of the interference / non-interference station list is It may include at least one station that failed to transmit the response of the first frame within a first preset time.

Here, the first preset time may be SIFS.

Here, the frame transmission method may further include transmitting a third frame after a second preset time from a point in time when the first frame is received, when the third station is determined to be a non-interfering station. have.

Here, the step of transmitting the third frame includes: obtaining received power information for the second frame transmitted by the third station from the interference/non-interference station list, and receiving power for the second preset time And searching for a channel in consideration of information, and transmitting a third frame after the second preset time if there is no signal exceeding a preset signal size during the second preset time. have.

Here, the second preset time may be DIFS, PIFS, or AIFS.

Here, the third frame may be a frame requesting to stop transmitting the frame to the first station.

Here, the third frame may include at least one of a transmitter address of the third frame, information on a period during which transmission of the frame is stopped, and a receiver address of the third frame.

A first station according to another embodiment of the present invention for achieving the above object includes a processor, a memory in which at least one program instruction executed through the processor is stored, and the at least one program instruction comprises a second Receiving a first frame from a station, obtaining a receiver address of the first frame from the first frame, and a third station represented by the receiver address based on a pre-generated list of interference/non-interference stations, the interference station Alternatively, it is possible to perform the step of determining whether it is a non-interfering station.

Here, the interference station list of the interference / non-interference station list includes at least one station that transmits the response of the first frame within a first preset time, the non-interference station list of the interference / non-interference station list is It may include at least one station that failed to transmit the response of the first frame within a first preset time.

Here, when the third station determines that the third station is a non-interfering station, the at least one program command further performs the step of transmitting the third frame after a second preset time from the time when the reception of the first frame is completed. can do.

Here, the step of transmitting the third frame includes: obtaining received power information for the second frame transmitted by the third station from the interference/non-interference station list, and receiving power for the second preset time Searching for a channel in consideration of information, and when there is no signal exceeding a preset signal size during the second preset time, transmitting the third frame after the second preset time may be performed. have.

Here, the third frame may be a frame requesting to stop transmitting the frame to the first station.

According to the present invention, a station in an exposed node state can transmit a frame. On the other hand, a station in the blocking node state may request to stop transmission of a frame destined for it, and thereby prevent a frame destined for it from being transmitted. Therefore, the performance of the wireless LAN system can be improved.

1 is a block diagram showing an embodiment of a station for performing the methods according to the present invention.
2 is a conceptual diagram illustrating an embodiment of a configuration of a wireless LAN system according to IEEE 802.11.
3 is a flowchart illustrating a terminal connection procedure in the infrastructure BSS.
4 is a conceptual diagram illustrated to describe an exposed node problem.
5 is a conceptual diagram for explaining a case where a solution to an exposed node problem is applied.
6 is a conceptual diagram for explaining a case where another solution to an exposed node problem is applied.
7 is a conceptual diagram illustrating a blocking node problem.
8 is a conceptual diagram illustrated to explain an effect of a blocking node on a communication system.
9 is a block diagram showing the configuration of a processor constituting a station.
10 is a flowchart illustrating a method of generating a list of interference/non-interference stations according to an embodiment of the present invention.
11 is a flowchart illustrating a frame transmission method according to an embodiment of the present invention.
12 is a conceptual diagram showing an embodiment of a data frame transmission method according to the present invention.
13 is a conceptual diagram illustrating an embodiment of a PTS frame transmission method according to the present invention.
14 is a conceptual diagram showing another embodiment of a data frame transmission method according to the present invention.
15 is a conceptual diagram showing another embodiment of a PTS frame transmission method according to the present invention.
16 is a conceptual diagram showing another embodiment of a data frame transmission method according to the present invention.
17 is a conceptual diagram illustrating another embodiment of a PTS frame transmission method according to the present invention.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. The term and/or includes a combination of a plurality of related described items or any one of a plurality of related described items.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. It should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

The terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the overall understanding in describing the present invention, the same reference numerals are used for the same components in the drawings, and duplicate descriptions for the same components are omitted.

Throughout the specification, a station (STA) is a physical layer for a medium access control (MAC) and a wireless medium that conforms to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. It means any functional medium including an interface. The station STA may be divided into a station STA that is an access point (AP) and a station STA that is a non-AP. A station STA that is an access point (AP) may simply be called an access point (AP), and a station STA that is a non-access point (AP) may simply be called a terminal.

The station (STA) may include a processor (processor) and a transceiver (transceiver), may further include a user interface and a display (display) device. The processor refers to a unit designed to generate a frame to be transmitted through a wireless network or to process a frame received through a wireless network, and may perform various functions for controlling a station (STA). The transceiver is functionally connected to the processor, and means a unit designed to transmit and receive frames through a wireless network for a station (STA).

The access point (AP) is a centralized controller, a base station (BS), a radio access station, a node B (node B), an advanced node B (evolved node B), a relay, a MMR (mobile) multihop relay (BS)-BS, a base transceiver system (BTS), or a site controller, and may include some or all of them.

A terminal (ie, a non-access point) includes a wireless transmit/receive unit (WTRU), user equipment (UE), user terminal (UT), access terminal (access terminal, AT), Refers to a mobile station (MS), a mobile terminal, a subscriber unit, a subscriber station (SS), a wireless device, or a mobile subscriber unit. And can include some or all of them.

Here, the terminal is a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, and a smart watch capable of communication. (smart watch), smart glass, e-book reader, portable multimedia player (PMP), portable game machine, navigation device, digital camera, digital multimedia broadcasting (DMB) player, digital voice Digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player ).

1 is a block diagram showing an embodiment of a station for performing the methods according to the present invention.

Referring to FIG. 1, the station 100 may include at least one processor 110, a memory 120, and a network interface device 130 connected to a network to perform communication. In addition, the station 100 may further include an input interface device 140, an output interface device 150, a storage device 160, and the like. Each component included in the station 100 may be connected by a bus 170 to communicate with each other.

The processor 110 may execute program commands stored in the memory 120 and/or the storage device 160. The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to the present invention are performed. The memory 120 and the storage device 160 may be composed of volatile storage media and/or non-volatile storage media. For example, the memory 120 may be composed of read only memory (ROM) and/or random access memory (RAM).

The embodiments of the present invention are applied to a wireless LAN system according to IEEE 802.11, and may be applied to other communication systems as well as a wireless LAN system according to IEEE 802.11.

For example, embodiments of the present invention include a wireless personal area network (WPAN), a wireless body area network (WBAN), a wireless broadband internet (WiBro), or a wireless intercomability for microwave access (WiMax), a global system (GSM). 2G mobile networks such as for mobile communication (code division multiple access) or CDMA, 3G mobile networks such as wideband code division multiple access (WCDMA) or cdma2000, high speed downlink packet access (HSDPA) or high speed uplink (HSUPA) It can be applied to a 3.5G mobile communication network such as packet access, a long term evolution (LTE) or a 4G mobile communication network such as LTE-Advanced, a 5G mobile communication network.

2 is a conceptual diagram illustrating an embodiment of a configuration of a wireless LAN system according to IEEE 802.11.

Referring to FIG. 2, a wireless LAN system according to IEEE 802.11 may include at least one basic service set (BSS). BSS refers to a set of stations (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2), STA6, STA7, STA8) that can successfully communicate with each other by synchronizing, and not a concept of a specific area .

The BSS can be divided into an infrastructure BSS (Infrastructure BSS) and an independent BSS (Independent BSS). Here, BSS1 and BSS2 mean infrastructure BSS, and BSS3 means IBSS.

BSS1 is a first terminal (STA1), a first access point providing a distribution service (distribution service) (STA2 (AP1)) and a plurality of access points (STA2 (AP1), STA5 (AP2)) distribution system connecting ( distribution system, DS). In BSS1, the first access point STA2 (AP1) may manage the first terminal STA1.

BSS2 connects a third terminal (STA3), a fourth terminal (STA4), a second access point (STA5(AP2)) and a plurality of access points (STA2(AP1), STA5(AP2)) that provide distribution services. It may include a distribution system (DS). In BSS2, the second access point STA5 (AP2) may manage the third terminal STA3 and the fourth terminal STA4.

BSS3 means IBSS operating in an ad-hoc mode. In BSS3, there is no access point that is a centralized management entity. That is, in BSS3, the terminals STA6, STA7, and STA8 are managed in a distributed manner. In BSS 3, all the terminals STA6, STA7, and STA8 may refer to a mobile terminal, and since access is not allowed through the distribution system DS, a self-contained network is formed.

The access points STA2 (AP1) and STA5 (AP2) may provide access to the distributed system DS through a wireless medium for the terminals STA1, STA3, and STA4 coupled to them. In BSS1 or BSS2, communication between terminals STA1, STA3, and STA4 is generally performed through an access point (STA2(AP1), STA5(AP2)), but when a direct link is established, the terminals ( Direct communication between STA1, STA3, and STA4) is possible.

Multiple infrastructure BSSs may be interconnected through a distribution system (DS). A plurality of BSSs connected through a distribution system (DS) is referred to as an extended service set (ESS). The entities included in the ESS (STA1, STA2 (AP1), STA3, STA4, STA5 (AP2)) can communicate with each other, and any terminal (STA1, STA3, STA4) within the same ESS communicates without interruption. You can move from one BSS to another.

The distribution system (DS) is a mechanism for one access point to communicate with another access point, whereby the access point transmits a frame for the terminals coupled to the BSS it manages or moves to another BSS. A frame can be transmitted for any terminal. In addition, the access point can transmit and receive frames with an external network such as a wired network. Such a distribution system (DS) is not necessarily a network, and if it can provide a predetermined distribution service defined in the IEEE 802.11 standard, there is no limitation on its form. For example, the distribution system may be a wireless network, such as a mesh network, or a physical structure that connects access points to each other.

In the intrastructure BSS, the terminal STA may be connected to an access point AP. The terminal STA may transmit/receive data when connected to the access point AP.

3 is a flowchart illustrating a terminal connection procedure in the infrastructure BSS.

Referring to FIG. 3, the connection procedure of the terminal (STA) in the infrastructure BSS is largely a step (probe step) of detecting an access point (AP), an authentication step (authentication step) with the detected access point (AP), an authentication procedure It may be divided into an association step (association step) with the access point (AP).

The terminal STA may first detect neighboring access points APs using a passive scanning method or an active scanning method. When using the manual scanning method, the terminal STA may detect neighboring access points APs by overhearing the beacon transmitted by the access points APs. In the case of using the active scanning method, the terminal STA transmits a probe request frame and receives a probe response frame that is a response to the probe request frame from access points APs. One access point (APs) can be detected.

When the terminal STA detects neighboring access points APs, the terminal STA may perform an authentication step with the detected access point AP. In this case, the terminal STA may perform an authentication step with a plurality of access points APs. The authentication algorithm according to the IEEE 802.11 standard may be divided into an open system algorithm exchanging two authentication frames, a shared key algorithm exchanging four authentication frames, and the like.

Based on the authentication algorithm according to the IEEE 802.11 standard, the terminal (STA) transmits an authentication request frame and receives an authentication response frame that is a response to the authentication request frame from the access point (AP). By doing so, authentication with the access point (AP) can be completed.

The terminal STA may perform a connection step with the access point AP when authentication is completed. In this case, the terminal STA may select one of the access points (APs) that has performed the authentication step with itself, and may perform a connection step with the selected access point (AP). That is, the terminal STA transmits an association request frame to the selected access point AP and receives an association response frame that is a response to the connection request frame from the selected access point AP. The connection with the selected access point (AP) can be completed.

4 is a conceptual diagram illustrated to describe an exposed node problem.

Referring to FIG. 4, the first access point 410 and the first terminal 411 may configure the first infrastructure BSS 401, and the second access point 420 and the second terminal 421 may The second infrastructure BSS 402 may be configured. The first access point 410 may receive a frame transmitted from the first terminal 411, but cannot receive a frame transmitted from the second access point 420 and the second terminal 421.

The first terminal 411 may receive a frame transmitted from the first access point 410 and the second terminal 421, but may not receive a frame transmitted from the second access point 420. The second terminal 421 may receive a frame transmitted from the first terminal 411 and the second access point 420, but cannot receive a frame transmitted from the first access point 410. The second access point 420 may receive a frame transmitted from the second terminal 421, but cannot receive a frame transmitted from the first access point 410 and the first terminal 411.

Here, an exposed node problem is described in an environment where two infrastructure BSSs are adjacent to each other (or an overlapped environment), but an exposed node problem may also occur in an environment in which at least two Ad-hoc networks exist. . In the following, the effect of the first infrastructure BSS 401 on the second infrastructure BSS 402 when the first terminal 411 is connected to the first access point 410 and transmits a frame will be described.

Each of the communication entities (ie, access point and terminal) may search for a channel before transmitting a frame based on a carrier sense multiple access (CSMA) scheme. Therefore, the second terminal 421 may confirm that the first terminal 411 is transmitting the frame through channel search before transmitting the frame, and the frame until the frame transmission of the first terminal 411 ends. It may not send.

For example, according to the IEEE 802.11 standard, the second terminal 421 may receive a request to send (RTS) frame transmitted from the first terminal 411 based on a clear channel assessment (CCA) method of the MAC layer. have. The second terminal 421 may set a network allocation vector (NAV) based on a period indicated by a duration field included in a MAC header of the RTS frame, and do not transmit a frame for a period during which the NAV is set. It may not.

Meanwhile, when the first access point 410 receiving the frame transmitted from the first terminal 411 is located outside the interference area of the second terminal 421 (ie, the frame transmitted from the second terminal 421) When the first access point 410 is not normally received), the second terminal 421 transmits the frame to the second access point 420 while the first terminal 411 transmits the frame to the first access point 410. ), the first access point 410 can normally receive the frame transmitted from the first terminal 411, and the second access point 420 also receives the frame transmitted from the second terminal 421. You can receive normally.

As described above, the reason why only one terminal 411 or 421 should transmit a frame even though each of the access points 410 and 420 can simultaneously receive the frame is to search the channel before transmitting the frame according to the CSMA method. This is because the procedure is performed first. This is called an exposed node problem.

Since the exposed node problem is a case where frames are not transmitted despite being able to transmit frames, the transmission capacity of the communication system can be reduced by that amount. In the case of the CSMA method in which the RTS frame and the clear to send (CTS) frame are exchanged, a solution to the exposed node problem is conceptually known. That is, if the communication entity receives the RTS frame but does not receive the CTS frame in response to the RTS frame, the communication entity may transmit the frame within the signal range of the communication entity transmitting the RTS frame. However, when this solution is applied to a real system, the CSMA method, which is based on the LBT (listen before talk) method, does not have enough time to listen, so the communication object can simultaneously frame with other communication objects. It cannot be transmitted. These problems will be described in detail below.

5 is a conceptual diagram for explaining a case in which a solution to an exposed node problem is applied, and FIG. 6 is a conceptual diagram for explaining a case in which another solution to an exposed node problem is applied.

5 and 6, the first station STA1 and the second station STA2 may configure the first infrastructure BSS 401 of FIG. 4. The third station STA3 and the fourth station STA4 may configure the second infrastructure BSS 402 of FIG. 4. Each of the stations STA1, STA2, STA3, and STA4 may mean an access point or a terminal.

For example, the first station STA1 may be the same as the first terminal 411 of FIG. 4, and the second station STA2 may be the same as the first access point 410 of FIG. 4. The third station STA3 may be the same as the second terminal 421 of FIG. 4, and the fourth station STA4 may be the same as the second access point 420 of FIG. 4.

First, the first station STA1 may search for a channel during a distributed coordination function (DCF) inter-frame space (DIFS), and when a search does not detect a signal exceeding a preset signal size (ie, the channel is After the contention window (CW) according to the random backoff procedure, the RTS frame 501 may be transmitted to the second station STA2. When the RTS frame 501 is normally received, the second station STA2 may transmit the CTS frame 502 to the first station STA1 in response to the RTS frame 501. At this time, the second station STA2 may transmit the CTS frame 502 after the short inter-frame space (SIFS) from the end of the reception of the RTS frame 501.

When the CTS frame 502 is normally received, the first station STA1 may transmit the data frame 503 to the second station STA2 after SIFS from the end of reception of the CTS frame 502. When the data station 503 is normally received, the second station STA2 may transmit an acknowledgment (ACK) frame 504 to the first station STA1 in response to the data frame 503. In this case, the second station STA2 may transmit the ACK frame 504 after SIFS from the end of the reception of the data frame 503. When the first station STA1 receives the ACK frame 504, the second station STA2 may determine that the data frame 503 has been normally received.

Meanwhile, the third station STA3 receives the RTS frame 501 but does not receive the CTS frame 502 in response to the RTS frame 501 (that is, when it is determined that it is an exposed node), the CTS frame. A frame transmission may be attempted after the end point of reception of 502. In this case, the third station STA3 transmits the frames for a period from the end of reception of the CTS frame 502 to the start of reception of the ACK frame 504 (ie, 2×IFS + data frame 503 transmission time). Can transmit.

That is, the third station STA3 may search for a channel during DIFS after the end of the reception of the CTS frame 502, and when a search does not detect a signal exceeding a preset signal size (ie, the channel is idle) State) RTS frame 505 may be transmitted to the fourth station STA4 after the contention window CW according to the random backoff procedure. However, the data frame 503 is transmitted from the first station STA1 after SIFS (generally, SIFS <DIFS) has passed since the end of the reception of the CTS frame 502, and the third station STA3 is in the channel search. The data frame 503 can be detected.

Since the data frame 503 on the side of the third station STA3 corresponds to a high interference signal, the third station STA3 acquires a sufficient signal to noise ratio (SNR) for a frame transmitted from another communication entity. It is difficult. Accordingly, it is difficult for the third station STA3 to accurately check the channel state (ie, busy or idle) during DIFS after the end of the reception of the CTS frame 502. That is, since the third station STA3 cannot secure DIFS, which is a time for checking the channel status, the third station STA3 cannot transmit the frame at the same time as the first station STA1.

If the time for checking the channel state is defined as SIFS shorter than DIFS, the third station STA3 may transmit the frame simultaneously with the first station STA1. However, defining the time to check the channel status as SIFS does not conform to the CSMA method because the third station STA3 is given the same priority as the communication entity that has won the competition. Therefore, it is not easy to apply the solution of the above-mentioned exposure node problem directly to the communication system according to the CSMA method.

As another example, the third station STA3 may directly transmit the data frame 509 to the fourth station STA4 without using the RTS-CTS protocol. That is, the third station STA3 receives the CTS frame 502 that is the response of the RTS frame 501 when the channel is in an idle state for a predetermined period (XIFS) from the end of the reception of the RTS frame 501. If not, the data frame 509 may be transmitted to the fourth station STA4 after the contention window CW according to the random backoff procedure. Here, the length of the data frame 509 may be smaller than the length of the'transmission period of the third station STA3'.

When receiving the data frame 509, the fourth station STA4 may transmit the ACK frame 510 in response to the data frame 509 to the third station STA3. At this time, the fourth station STA4 may transmit the ACK frame 510 after the transmission of the data frame 503 is completed to prevent collision between the data frame 503 and the ACK frame 510. Alternatively, when a response to the success or failure of receiving the data frame 509 between the third station STA3 and the fourth station STA4 is set not to be transmitted/received, the fourth station STA4 receives the data frame 509 Also, the ACK frame 510 in response to the data frame 509 may not be transmitted to the third station STA3.

On the other hand, the block node problem is a problem that occurs because the exposed node problem is not solved, and thus the transmission capacity of the communication system may be reduced.

7 is a conceptual diagram illustrating a blocking node problem.

Referring to FIG. 7, the first access point 610 and the first terminal 611 may configure the first infrastructure BSS 601, and the second access point 620 and the second terminal 621 may The second infrastructure BSS 602 may be configured. The first access point 610 may receive a frame transmitted from the first terminal 611, but cannot receive a frame transmitted from the second access point 620 and the second terminal 621.

The first terminal 611 may receive a frame transmitted from the first access point 610 and the second terminal 621, but cannot receive a frame transmitted from the second access point 620. The second terminal 621 may receive a frame transmitted from the first terminal 611 and the second access point 620, but cannot receive a frame transmitted from the first access point 610. The second access point 620 may receive a frame transmitted from the second terminal 621, but cannot receive a frame transmitted from the first access point 610 and the first terminal 611.

Here, although the blocking node problem is described in an environment where two infrastructure BSSs are adjacent to each other (or an overlapped environment), a blocking node problem may also occur in an environment in which at least two Ad-hoc networks exist.

The first terminal 611 may transmit the RTS frame to the first access point AP1. In this case, since the second terminal 621 can receive the RTS frame transmitted from the first terminal 611, the NAV can be set based on the period indicated by the duration field included in the MAC header of the RTS frame, and the NAV May not transmit the frame for a set period. At this time, the second terminal 621 may correspond to a blocking node because frame transmission is stopped by the NAV setting.

Meanwhile, since the second access point 620 cannot receive the RTS frame transmitted from the first terminal 611, the second access point 620 may transmit the frame regardless of the NAV set based on the RTS frame. That is, when the second terminal 621 operates in a state in which the frame cannot be transmitted by the NAV setting, the second access point 620 transmits the RTS frame to the second terminal (if there is data to be transmitted to the second terminal 621) 621).

In this case, the second terminal 621 may face two situations. The first is that the second terminal 621 is transmitted from the second access point 620 by colliding the RTS frame or data frame transmitted from the first terminal 611 and the RTS frame transmitted from the second access point 620 It is the case that RTS frame cannot be received normally. Second, when the second terminal 621 normally receives the RTS frame transmitted from the second access point 620, the response of the RTS frame by the NAV set based on the RTS frame received from the first terminal 611 This is a case where the CTS frame cannot be transmitted to the second access point 620.

In both cases, the second access point 620 does not receive the CTS frame in response to the RTS frame from the second terminal 621, so the RTS frame is retransmitted to the second terminal 621. Due to this, time is wasted as much as the time to retransmit the RTS frame to the second terminal 621, which is called a blocking node problem.

8 is a conceptual diagram illustrated to explain an effect of a blocking node on a communication system.

Referring to FIG. 8, the first station STA1 and the second station STA2 may configure the first infrastructure BSS 601 of FIG. 6. The third station STA3 and the fourth station STA4 may configure the second infrastructure BSS 602 of FIG. 6. Each of the stations STA1, STA2, STA3, and STA4 may mean an access point or a terminal.

For example, the first station STA1 may be the same as the first terminal 611 of FIG. 6, and the second station STA2 may be the same as the first access point 610 of FIG. 6. The third station STA3 may be the same as the second terminal 621 of FIG. 6, and the fourth station STA4 may be the same as the second access point 620 of FIG. 6.

First, the first station STA1 can search for a channel during DIFS, and if a signal exceeding a preset signal size is not detected as a result of the search (ie, when the channel is in an idle state), the competition according to the random backoff procedure After the window CW, the RTS frame 701 may be transmitted to the second station STA2. When the RTS frame 701 is normally received, the second station STA2 may transmit the CTS frame 702 to the first station STA1 in response to the RTS frame 701. At this time, the second station STA2 may transmit the CTS frame 702 after SIFS from the end of reception of the RTS frame 701.

When the CTS frame 702 is normally received, the first station STA1 may transmit the data frame 703 to the second station STA2 after SIFS from the end of reception of the CTS frame 702. When the second station STA2 normally receives the data frame 703, the second station STA2 may transmit the ACK frame 704 to the first station STA1 in response to the data frame 703. At this time, the second station STA2 may transmit the ACK frame 704 after SIFS from the end of the reception of the data frame 703. When the first station STA1 receives the ACK frame 704, the first station STA1 may determine that the data frame 703 is normally received from the second station STA2.

Meanwhile, when the RTS frame 701 is received from the first station STA1, the third station STA3 may set the NAV based on the period indicated by the duration field included in the MAC header of the RTS frame 701. However, the frame may not be transmitted for a period indicated by the set NAV. Since the fourth station STA4 cannot normally receive the RTS frame 701 or the CTS frame 702, it does not set the NAV based on the RTS frame 701 or the CTS frame 702. Therefore, regardless of the NAV set based on the RTS frame 701 or the CTS frame 702, the fourth station STA4 transmits the RTS frame 705 to the third station when there is data to be transmitted to the third station STA3. Station STA3. At this time, the fourth station STA4 searches for a channel during DIFS, and if a signal exceeding a preset signal size is not detected as a result of the search (that is, when the channel is in an idle state), a competition window according to a random backoff procedure ( For example, after CW=2), the RTS frame 705 may be transmitted to the third station STA3.

The third station STA3 may receive the RTS frame 705 from the fourth station STA4. However, since the third station STA3 cannot transmit the frame by the NAV set based on the RTS frame 701 received from the first station STA1, the CTS frame 706 that is a response to the RTS frame 705 ) To the fourth station STA4. In this case, the fourth station STA4 transmits the CTS frame 706 to the third station STA3 until the end of reception of the CTS frame 706 (ie, CTS timeout) in response to the RTS frame 705. ), it is possible to perform the retransmission process of the RTS frame.

That is, the fourth station STA4 can search for a channel during DIFS from the end of reception of the CTS frame 706, and when a search does not detect a signal exceeding a preset signal size (ie, the channel is idle) In case), the RTS frame 707 may be transmitted to the third station STA3 after the contention window (eg, C=4) according to the random backoff procedure. At this time, since the transmission of the RTS frame 705 has failed, the contention window (CW) used for the transmission of the RTS frame 707 may be twice the contention window (CW) used for the transmission of the RTS frame 705. . On the other hand, since the third station STA3 collides with the data frame 703 transmitted from the first station STA1 and the RTS frame 707 transmitted from the second access point AP2, the RTS frame 707 is normally used. You may not be able to receive. In this case, the fourth station STA4 does not receive the CTS frame 708 from the third station STA3 until the end of reception of the CTS frame 708, which is a response to the RTS frame 707, and thus, The retransmission process can be performed again.

In this way, the fourth station STA4 wastes unnecessary time by retransmitting the RTS frame. That is, the performance of the communication system may be significantly deteriorated due to a blocking node problem.

In the following, solutions to the exposed node problem and the blocking node problem will be described in detail. The station performing the methods according to the invention may be the same as the station shown in FIG. 1. In particular, the configuration of the processor constituting the station shown in FIG. 1 may be as follows.

9 is a block diagram showing the configuration of a processor constituting a station.

Referring to FIG. 9, the processor 110 may include a channel access management unit 111, an interference/non-interference station list management unit 112, and a simultaneous transmission management unit 113. Here, the channel access management unit 111 may mean a configuration in charge of conventional transmission among stations. The channel access management unit 111 and the interference/non-interference station list management unit 112 may be connected through the first interface 110-1 and the second interface 110-2. The channel connection management unit 111 and the simultaneous transmission management unit 113 may be connected through the third interface 110-3 and the fourth interface 110-4. The interference/non-interference station list management unit 112 and the simultaneous transmission management unit 113 may be connected through the fifth interface 110-5.

The interference/non-interference station list management unit 112 generates, manages, and updates the interference station list and non-interference station list based on the information transmitted from the channel access management unit 111 through the first interface 110-1. It can be done. In addition, the interference/non-interference station list management unit 112 may request at least one of the interference station list and the non-interference station list according to the request of the channel access management unit 111 through the first interface 110-1. It can be transmitted to the channel access management unit 111 through -2). In addition, the interference/non-interference station list management unit 112 concurrently manages at least one of the interference station list and the non-interference station list through the fifth interface 110-5 at the request of the simultaneous transmission management unit 113. ).

The simultaneous transmission management unit 113 may determine whether simultaneous transmission is possible based on at least one of the interference station list and the non-interference station list obtained from the interference/non-interference station list management unit 112, and if simultaneous transmission is possible, other communication Transmission can be performed simultaneously with the object.

10 is a flowchart illustrating a method of generating a list of interference/non-interference stations according to an embodiment of the present invention.

Referring to FIG. 10, the first station may receive the first frame from the second station through channel discovery (eg, CCA) (S910). The first station and the second station may mean an access point or a terminal, respectively. Here, the first frame may be a probe request frame, an authentication request frame, a connection request frame, a reassociation request frame, an RTS frame, a data frame, or a block acknowledgment request (BAR) frame.

The first station may obtain a receiver address (RA) of the first frame from an address field included in the MAC header of the first frame (S920). The first station may determine whether the station indicated by the receiver address of the first frame is itself (S930). If the station indicated by the receiver address of the first frame is itself, the first station may transmit a response to the first frame to the second station after SIFS from the end point of reception of the first frame (S940).

On the other hand, if the station indicated by the receiver address of the first frame is a third station other than itself, the first station may generate a list of interference/non-interference stations as follows. The first station may determine whether to receive the second frame, which is a response of the first frame transmitted from the third station indicated by the receiver address of the first frame, within a preset time from the end time of the reception of the first frame (S950). . Here, the third station may mean an access point or a terminal, and the preset time may mean SIFS. The second frame may be a probe response frame, an authentication response frame, a connection response frame, a reassociation response frame, a CTS frame, an ACK frame, or a block acknowledgment (BA) frame.

When the second frame is normally received within a preset time, the first station may set the third station as an interference station (S960). The first station is the interference station including the identification information of the third station (eg, MAC address, association identifier (AID), partial association identifier (PAID), etc.) and received power information of the second frame measured at the first station. A list may be generated (S970).

On the other hand, if the second frame is not normally received within a preset time, the first station may set the third station as a non-interfering station (S980). The first station may generate a list of non-interfering stations including identification information of the third station and received power information of the second frame measured at the first station (S990).

In the following, a frame transmission method based on the interference station list and the non-interference station list will be described.

11 is a flowchart illustrating a frame transmission method according to an embodiment of the present invention.

Referring to FIG. 11, the first station may receive the first frame from the second station through channel discovery (eg, CCA) (S1010). The first station and the second station may mean an access point or a terminal, respectively. Here, the first frame may be an RTS frame, a data frame, or a BAR frame.

The first station may obtain the receiver address of the first frame from the address field included in the MAC header of the first frame (S1020). The first station may determine whether the station indicated by the receiver address of the first frame is itself (S1030). If the station indicated by the receiver address of the first frame is itself, the first station may transmit a response to the first frame to the second station after SIFS from the end point of the reception of the first frame (S1040).

On the other hand, if the station indicated by the receiver address of the first frame is a third station other than itself, the first station may transmit the frame as follows. The first station interferes with the third station indicated by the receiver address of the first frame (that is, the third station transmitting the second frame in response to the first frame) based on the pre-generated interference station list and the non-interference station list. Whether it is a station or a non-interfering station may be determined (S1050). Here, the third station may mean an access point or a terminal. The second frame may be a CTS frame, ACK frame or BA frame.

The interference station list and the non-interference station list may be the same as the interference station list and the non-interference station list described with reference to FIG. 10, respectively. The interference station list may include identification information of the interference station and received power information of a frame transmitted from the interference station. The non-interference station list may include identification information of the non-interference station and received power information of a frame transmitted from the non-interference station.

If the identification information of the third station is included in the interference station list (ie, the third station is the interference station), the first station can receive the second frame transmitted from the third station, and the second The NAV may be set based on the period indicated by the duration field included in the MAC header of the frame, and the frame may not be transmitted during the period indicated by the NAV (S1060).

On the other hand, when the identification information of the third station is included in the non-interference station list (that is, when the third station is a non-interference station), the first station may transmit the third frame to another communication entity. Specifically, the first station may obtain the received power information for the frame transmitted by the third station from the non-interference station list (S1070).

The first station may search for a channel for a preset time in consideration of the received received power information (S1080). That is, the first station determines a predetermined signal size (ie, the idle state of the channel) based on the received power information obtained from the non-interfering station list in order to remove the influence of the frame transmitted from the third station when searching for a channel. Signal size). For example, the first station may set a difference between the preset signal size and the received power indicated by the received power information to a new preset signal size, and determine whether a signal exceeding the new preset signal size is detected through channel search can do. Here, the preset time may be DIFS, point coordination function (PCF) inter-frame space (PIFS) or arbitration inter-frame space (AIFS).

The first station may determine that the channel is in an idle state when a signal exceeding a new preset signal size is not detected for a preset time, and may transmit a third frame to another communication entity (S1090). Here, the third frame may be an RTS frame or a frame requesting to stop transmission of a frame to a first station (hereinafter referred to as a'prevent to send (PTS) frame'). The PTS frame may include at least one of a transmitter address (TA) of the PTS frame, information on a period during which transmission of the frame is stopped, and a receiver address of the PTS frame.

When the first station has data to be transmitted to another communication entity, the RTS frame may be transmitted to another communication entity as a third frame. In this case, the first station may transmit the data frame to another communication entity through the exchange of the RTS frame and the CTS frame. Through this, the problem of the exposed node can be solved.

On the other hand, if the first station does not have data to be transmitted to another communication entity, it may transmit a PTS frame as a third frame. At this time, the first station may transmit a PTS frame in a broadcast method, a multicast method, or a unicast method. Each of the communication entities that have received the PTS frame may acquire the transmitter address of the PTS frame included in the PTS frame, and may not transmit the frame to the first station indicated by the transmitter address. In addition, each of the communication entities that have received the PTS frame can further acquire period information in which the frame transmission included in the PTS frame is stopped, and transmit the frame to the first station for a period indicated by the period information in which the frame transmission is stopped. You may not. Through this, the blocking node problem can be solved.

12 is a conceptual diagram showing an embodiment of a data frame transmission method according to the present invention, and FIG. 13 is a conceptual diagram showing an embodiment of a PTS frame transmission method according to the present invention.

12 and 13, the first station STA1 and the second station STA2 may configure the first infrastructure BSS 401 of FIG. 4 or the first infrastructure BSS 601 of FIG. 6. have. The third station STA3 and the fourth station STA4 may configure the second infrastructure BSS 402 of FIG. 4 or the second infrastructure BSS 602 of FIG. 6. Each of the stations STA1, STA2, STA3, and STA4 may mean an access point or a terminal.

For example, the first station STA1 may be the same as the first terminal 411 of FIG. 4 or the first terminal 611 of FIG. 6, and the second station STA2 may be the first access point of FIG. 4 It may be the same as 410 or the first access point 610 of FIG. 6. The third station STA3 may be the same as the second terminal 421 of FIG. 4 or the second terminal 621 of FIG. 6, and the fourth station STA4 may be the second access point 420 of FIG. 4 or It may be the same as the second access point 620 of FIG. 6.

First, the first station STA1 can search for a channel during DIFS, and if a signal exceeding a preset signal size is not detected as a result of the search (ie, when the channel is in an idle state), the competition according to the random backoff procedure After the window, the RTS frame 1101 may be transmitted to the second station STA2. When the RTS frame 1101 is normally received, the second station STA2 may transmit the CTS frame 1102 to the first station STA1 in response to the RTS frame 1101. At this time, the second station STA2 may transmit the CTS frame 1102 after SIFS from the end of reception of the RTS frame 1101.

When the CTS frame 1102 is normally received, the first station STA1 may transmit the data frame 1103 to the second station STA2 after SIFS from the end of reception of the CTS frame 1102. The second station STA2 may transmit the ACK frame 1104 to the first station STA1 in response to the data frame 1103 when the data frame 1103 is normally received. At this time, the second station STA2 may transmit the ACK frame 1104 after SIFS from the end of the reception of the data frame 1103. When the first station STA1 receives the ACK frame 1104, the first station STA1 may determine that the data frame 1103 is normally received from the second station STA2.

Meanwhile, when the RTS frame 1101 is received, the third station STA3 may acquire the receiver address of the RTS frame 1101 from the address field included in the MAC header of the RTS frame 1101. The third station STA3 may determine whether the second station STA2 indicated by the receiver address is an interfering station or a non-interfering station based on the previously generated interference station list and the non-interference station list. Here, the interference station list and the non-interference station list may be the same as the interference station list and the non-interference station list described above with reference to FIG. 10, respectively. That is, the interference station list may include identification information of the interference station and received power information of a frame transmitted by the interference station. Also, the non-interference station list may include identification information of the non-interference station and received power information of a frame transmitted by the non-interference station.

If the identification information of the second station STA2 is included in the interference station list, the third station STA3 may determine the second station STA2 as the interference station. In this case, the third station STA3 may set the NAV based on the RTS frame 1101, and may not transmit the frame to another communication entity during a period indicated by the set NAV.

On the other hand, if the identification information of the second station STA2 is included in the non-interference station list, the third station STA3 may determine the second station STA2 as a non-interference station. The third station STA3 may search for a channel for a preset time (XIFS) from the end of reception of the RTS frame 1101 and determine the presence of a signal exceeding a preset signal size through the channel search. . Here, the preset time (XIFS) may be DIFS, PIFS, or AIFS. In addition, the preset time (XIFS) may be smaller than the available channel idle period, and the available channel idle period may be from the end of reception of the RTS frame 1101 to the start of reception of the data frame 1103.

Specifically, the third station STA3 receives the received power information from the third station STA3 for the frame transmitted by the second station STA2 (for example, the CTS frame in response to the RTS frame) from the non-interference station list. Can be obtained. The third station STA3 may search for a channel for a preset time (XIFS) in consideration of the received received power information. That is, the third station STA3 is based on received power information for the frame transmitted by the second station STA2 in order to remove the influence of the CTS frame 1102 transmitted from the second station STA2 when searching for a channel. The preset signal size can be adjusted. For example, the third station STA3 may set the difference between the preset signal size and the received power indicated by the received power information to a new preset signal size, and a signal exceeding the new preset signal size through channel search It can be determined whether it is detected.

When the channel is idle for a preset time (XIFS) (that is, when a signal exceeding a new preset signal size is not detected), the third station STA3 is configured according to the presence or absence of data to be transmitted to another communication entity. It can work like this.

When there is data to be transmitted to another communication object

When the third station STA3 has data to be transmitted to the fourth station STA4, the RTS frame 1105 is transmitted to the fourth station AP4 after a preset time (XIFS) from the end of reception of the RTS frame 1101. Can transmit. At this time, the third station STA3 may transmit the RTS frame 1105 to the fourth station STA4 after the contention window according to the random backoff procedure.

When the RTS frame 1105 is normally received, the fourth station STA4 may transmit the CTS frame 1106 to the third station STA3 in response to the RTS frame 1105. At this time, the fourth station STA4 may transmit the CTS frame 1106 after SIFS from the end of reception of the RTS frame 1105.

When the CTS frame 1106 is normally received, the third station STA3 may transmit the data frame 1107 to the fourth station STA4 after SIFS from the end of reception of the CTS frame 1106. The fourth station STA4 may transmit the ACK frame 1108 to the third station STA3 in response to the data frame 1107 when the data frame 1107 is normally received. In this case, the fourth station STA4 may transmit the ACK frame 1108 after SIFS from the end of the reception of the data frame 1107. When receiving the ACK frame 1108, the third station STA3 may determine that the ACK frame 1108 is normally received by the fourth station STA4.

Here, the transmission and reception of the RTS frame 1105, the CTS frame 1106, the data frame 1107, and the ACK frame 1108 is performed within the reception start time of the ACK frame 1104 from the reception end time of the RTS frame 1101. Can be.

When there is no data to be transmitted to another communication object

The third station STA3 may transmit the PTS frame 1109 after a preset time (XIFS) from the end of reception of the RTS frame 1101. The PTS frame 1109 may refer to a frame requesting to stop frame transmission to the third station STA3. The PTS frame 1109 may include at least one of a transmitter address (that is, an address of the third station STA3), a period information in which transmission of the frame is stopped, and a receiver address. The PTS frame 1109 may be transmitted in a broadcast method, a multicast method, or a unicast method.

Meanwhile, the fourth station STA4 may receive the PTS frame 1109 from the third station STA3. The fourth station STA4 may obtain the transmitter address from the PTS frame 1109 and may not transmit the frame to the third station STA3 indicated by the transmitter address. In addition, the fourth station STA4 may further acquire period information in which the transmission of the frame is stopped from the PTS frame 1109, in this case, the third station STA3 indicated by the transmitter address during the period in which the transmission of the frame is stopped. It may not transmit the frame. The period information in which the transmission of the frame is stopped may indicate from the end of reception of the PTS frame 1109 to the start of reception of the ACK frame 1104.

14 is a conceptual diagram illustrating another embodiment of a data frame transmission method according to the present invention, and FIG. 15 is a conceptual diagram illustrating another embodiment of a PTS frame transmission method according to the present invention.

14 and 15, the first station STA1 and the second station STA2 may configure the first infrastructure BSS 401 of FIG. 4 or the first infrastructure BSS 601 of FIG. 6. have. The third station STA3 and the fourth station STA4 may configure the second infrastructure BSS 402 of FIG. 4 or the second infrastructure BSS 602 of FIG. 6. Each of the stations STA1, STA2, STA3, and STA4 may mean an access point or a terminal.

For example, the first station STA1 may be the same as the first terminal 411 of FIG. 4 or the first terminal 611 of FIG. 6, and the second station STA2 may be the first access point of FIG. 4 It may be the same as 410 or the first access point 610 of FIG. 6. The third station STA3 may be the same as the second terminal 421 of FIG. 4 or the second terminal 621 of FIG. 6, and the fourth station STA4 may be the second access point 420 of FIG. 4 or It may be the same as the second access point 620 of FIG. 6.

The first station STA1 may continuously transmit data frames during a transmission opportunity (TXOP). Also, the first station STA1 may transmit a data frame without exchanging RTS frames and CTS frames, such as frame burst transmission or frame fragmentation transmission.

That is, the first terminal STA1 can search for a channel during DIFS, and if a signal exceeding a preset signal size is not detected as a result of the search (ie, when the channel is in an idle state), the competition according to the random backoff procedure After the window CW, the data frame 1301 may be transmitted to the second station STA2. When the data station 1301 is normally received, the second station STA2 may transmit the ACK frame 1302 to the first station STA1 after SIFS from the end of reception of the data frame 1301. When receiving the ACK frame 1302, the first station STA1 may determine that the data frame 1301 is normally received by the second station STA2.

The first station STA1 may transmit the data frame 1303 to the second station STA2 after SIFS from the end of reception of the ACK frame 1302. The second station STA2 may transmit the ACK frame 1304 to the first station STA1 after SIFS from the end of reception of the data frame 1303 when the data frame 1303 is normally received. When receiving the ACK frame 1304, the first station STA1 may determine that the data frame 1303 is normally received by the second station STA2.

On the other hand, when receiving the data frame 1301, the third station STA3 may acquire the receiver address of the data frame 1301 from the address field included in the MAC header of the data frame 1301. The third station STA2 may determine whether the second station STA2 indicated by the receiver address is an interfering station or a non-interfering station based on the previously generated interference station list and the non-interference station list. Here, the interference station list and the non-interference station list may be the same as the interference station list and the non-interference station list described above with reference to FIG. 10, respectively. That is, the interference station list may include identification information of the interference station and received power information of a frame transmitted by the interference station. Also, the non-interference station list may include identification information of the non-interference station and received power information of a frame transmitted by the non-interference station.

If the identification information of the second station STA2 is included in the interference station list, the third station STA3 may determine the second station STA2 as the interference station. In this case, the third station STA3 may set the NAV based on the data frame 1301 and may not transmit the frame to another communication entity during a period indicated by the set NAV.

On the other hand, if the identification information of the second station STA2 is included in the non-interference station list, the third station STA3 may determine the second station STA2 as a non-interference station. The third station STA3 may search for a channel for a preset time (XIFS) from the end of reception of the data frame 1301, and may determine the existence of a signal exceeding a preset signal size through the channel search. . Here, the preset time (XIFS) may be DIFS, PIFS, or AIFS. In addition, the preset time (XIFS) may be smaller than the available channel idle period, and the available channel idle period may be from a reception end time of the data frame 1301 to a reception start time of the data frame 1303.

Specifically, the third station STA3 receives the received power information from the third station STA3 for the frame transmitted by the second station STA2 (for example, the ACK frame in response to the data frame) from the non-interference station list. Can be obtained. The third station STA3 may search for a channel for a preset time (XIFS) in consideration of the received received power information. That is, the third station STA3 has a preset signal size based on the received power information obtained from the non-interfering station list to remove the influence of the ACK frame 1302 transmitted from the second station STA2 when searching for a channel. Can be adjusted. For example, the third station STA3 may set the difference between the preset signal size and the received power indicated by the received power information to a new preset signal size, and a signal exceeding the new preset signal size through channel search It can be determined whether it is detected.

When the channel is idle for a preset time (XIFS) (that is, when a signal exceeding a new preset signal size is not detected), the third station STA3 is configured according to the presence or absence of data to be transmitted to another communication entity. It can work like this.

When there is data to be transmitted to another communication object

When the third station STA3 has data to be transmitted to the fourth station STA4, the RTS frame 1305 is transmitted to the fourth station STA4 after a preset time (XIFS) from the end of reception of the data frame 1301. Can transmit. At this time, the third station STA3 may transmit the RTS frame 1305 to the fourth station STA4 after the contention window according to the random backoff procedure.

When the RTS frame 1305 is normally received, the fourth station STA4 may transmit the CTS frame 1306 to the third station STA3 in response to the RTS frame 1305. At this time, the fourth station STA4 may transmit the CTS frame 1306 after SIFS from the end of reception of the RTS frame 1305.

When the CTS frame 1306 is normally received, the third station STA3 may transmit the data frame 1307 to the fourth station STA4 after SIFS from the end of the reception of the CTS frame 1306. When the data station 1307 is normally received, the fourth station STA4 may transmit the ACK frame 1308 to the third station STA3 in response to the data frame 1307. In this case, the fourth station STA4 may transmit the ACK frame 1308 after SIFS from the end of the reception of the data frame 1307. When receiving the ACK frame 1308, the third station STA3 may determine that the data frame 1307 has been normally received by the fourth station STA4.

Here, the transmission/reception of the RTS frame 1305, CTS frame 1306, data frame 1307, and ACK frame 1308 is performed within the reception start time of the ACK frame 1304 from the reception end time of the data frame 1301. Can be.

When there is no data to be transmitted to another communication object

The third station STA3 may transmit the PTS frame 1309 after a preset time (XIFS) from the end of reception of the data frame 1301. The PTS frame 1309 may refer to a frame requesting to stop frame transmission to the third station STA3. The PTS frame 1309 may include at least one of a transmitter address (ie, an address of a third station STA3), a period information for stopping transmission of the frame, and a receiver address. The PTS frame 1309 may be transmitted in a broadcast method, a multicast method, or a unicast method.

Meanwhile, the fourth station STA4 may receive the PTS frame 1309 from the third station STA3. The fourth station STA4 may obtain the transmitter address from the PTS frame 1309 and may not transmit the frame to the third station STA3 indicated by the transmitter address. In addition, the fourth station STA4 may further acquire period information in which the transmission of the frame is stopped from the PTS frame 1309, in which case the third station STA3 indicated by the transmitter address during the period in which the transmission of the frame is stopped. It may not transmit the frame. The period information in which the transmission of the frame is stopped may indicate from the end of reception of the PTS frame 1309 to the start of reception of the ACK frame 1304.

16 is a conceptual diagram showing another embodiment of a data frame transmission method according to the present invention, and FIG. 17 is a conceptual diagram showing another embodiment of a PTS frame transmission method according to the present invention.

16 and 17, the first station STA1, the second station STA2, the third station STA3, and the fourth station STA4 may constitute a first infrastructure BSS. The fifth station STA5 and the sixth station STA6 may constitute a second infrastructure BSS. The first station STA1 can normally receive frames transmitted from the second station STA2, the third station STA3, the fourth station STA4, and the fifth station STA5, but the sixth station STA6 ) Cannot be normally received.

The fifth station STA5 may normally receive frames transmitted from the first station STA1, the second station STA2, the third station STA3, and the sixth station STA6, but the fourth station STA4 ) Cannot be normally received. The sixth station STA6 may normally receive a frame transmitted from the fifth station STA5, but the first station STA1, the second station STA2, the third station STA3, and the fourth station STA4 ) Cannot be normally received.

That is, the first station STA1, the second station STA2, and the third station STA3 may refer to an interference station for the fifth station STA5. The fourth station STA4 may refer to a non-interfering station for the fifth station STA5. Here, each of the stations STA1, STA2, STA3, STA4, STA5, and STA6 may be a terminal or an access point.

First, the first station STA1 can search for a channel during DIFS, and if a signal exceeding a preset signal size is not detected as a result of the search (ie, when the channel is in an idle state), the competition according to the random backoff procedure After the window CW, the data frame 1501 may be transmitted to the second station STA2, the third station STA3, and the fourth station STA4 in a multicast method. Here, the ACK policy of the second station STA2 may be an implicit BA, and the ACK policy of the third station STA3 and the fourth station STA4 may be an explicit BA. .

When receiving the data frame 1501, the second station STA2 may transmit the BA frame 1502 in response to the data frame 1501 to the first station STA1. When the first station STA1 receives the BA frame 1502, the BAR frame 1503 may be transmitted to the third station STA3 after SIFS from the reception end time of the BA frame 1502. When receiving the BAR frame 1503, the third station STA3 may transmit the BA frame 1504 in response to the data frame 1501 to the first station STA1. When receiving the BA frame 1504, the first station STA1 may transmit the BAR frame 1505 to the fourth station STA4 after SIFS from the end point of the reception of the BA frame 1504. When receiving the BAR frame 1505, the fourth station STA4 may transmit the BA frame 1506 in response to the data frame 1501 to the first station STA1. When the first station STA1 receives the BA frame 1506, the data frame 1507 is multicast by the second station STA2 and STA3 after the SIFS from the reception end time of the BA frame 1506. ) And the fourth station STA4.

Meanwhile, the fifth station STA5 may receive the data frame 1501 transmitted from the first station STA1. The fifth station STA5 can obtain the receiver address of the data frame 1501 from the data frame 1501, and the receiver address is the second station STA2, the third station STA3, and the fourth station STA4. You can see that

The fifth station STA5 determines whether the second station STA2, the third station STA3, and the fourth station STA4 are the interfering station or the non-interfering station based on the pre-generated interference station list and the non-interference station list. can do. Here, it is assumed that the second station STA2 and the third station STA3 are interference stations, and the fourth station STA4 is assumed to be a non-interference station.

The interference station list and the non-interference station list may be the same as the interference station list and the non-interference station list described above with reference to FIG. That is, the interference station list may include identification information of the interference station and received power information of a frame transmitted by the interference station. Also, the non-interference station list may include identification information of the non-interference station and received power information of a frame transmitted by the non-interference station.

When the identification information of the second station STA2 is included in the interference station list, the fifth station STA5 may determine the second station STA2 as an interference station. Therefore, the fifth station STA5 may not attempt to transmit the frame while the second station STA2 transmits the BA frame 1502.

When the identification information of the third station STA3 is included in the interference station list, the fifth station STA5 may determine the third station STA3 as an interference station. Therefore, the fifth station STA5 may not attempt to transmit the frame while the third station STA3 transmits the BA frame 1504.

When the identification information of the fourth station STA4 is included in the non-interference station list, the fifth station STA5 may determine the fourth station STA4 as a non-interference station. The fifth station STA5 may search for a channel for a preset time (XIFS) from the end of reception of the BAR frame 1505 and determine the existence of a signal exceeding a preset signal size through the channel search. . Here, the preset time (XIFS) may be DIFS, PIFS, or AIFS. In addition, the preset time (XIFS) may be smaller than the available channel idle period, and the available channel idle period may be from the end of reception of the BAR frame 1505 to the start of reception of the data frame 1507.

Specifically, the fifth station STA5 receives the received power information from the fifth station STA5 for the frame transmitted by the fourth station STA4 (for example, the BA frame in response to the data frame) from the non-interference station list. Can be obtained. The fifth station STA5 may search for a channel for a preset time (XIFS) in consideration of the received received power information. That is, the fifth station STA5 sets a predetermined signal size based on received power information obtained from the non-interfering station list to remove the influence of the BA frame 1506 transmitted from the fourth station STA4 when searching for a channel. Can be adjusted. For example, the fifth station STA5 may set the difference between the preset signal size and the received power indicated by the received power information to a new preset signal size, and a signal exceeding the new preset signal size through channel search It can be determined whether it is detected.

When the channel is idle for a preset time (XIFS) (that is, when a signal exceeding a new preset signal size is not detected), the fifth station STA5 is configured according to the presence or absence of data to be transmitted to another communication entity. It can work like this.

When there is data to be transmitted to another communication object

When the fifth station STA5 has data to be transmitted to the sixth station STA6, the RTS frame 1508 is transmitted to the sixth station STA6 after a preset time (XIFS) from the end of reception of the BAR frame 1505. Can transmit. At this time, the fifth station STA5 may transmit the RTS frame 1508 to the sixth station STA6 after the contention window according to the random backoff procedure.

When the RTS frame 1508 is normally received, the sixth station STA6 may transmit the CTS frame 1509 to the fifth station STA5 in response to the RTS frame 1508. At this time, the sixth station STA6 may transmit the CTS frame 1509 after the SIFS from the end of the reception of the RTS frame 1508.

When the CTS frame 1509 is normally received, the fifth station STA5 may transmit the data frame 1510 to the sixth station STA6 after SIFS from the end of reception of the CTS frame 1509. When the data frame 1510 is normally received, the sixth station STA6 may transmit the ACK frame 1511 to the fifth station STA5 in response to the data frame 1510. At this time, the sixth station STA6 may transmit the ACK frame 1511 after SIFS from the end of reception of the data frame 1510.

Here, the transmission and reception of the RTS frame 1508, the CTS frame 1509, the data frame 1510, and the ACK frame 1511 starts when the reception of the response to the data frame 1507 starts from the reception end of the BAR frame 1505. Can be performed within.

When there is no data to be transmitted to another communication object

The fifth station STA5 may transmit the PTS frame 1512 after a preset time (XIFS) from the end of reception of the BAR frame 1505. The PTS frame 1512 may refer to a frame requesting to stop frame transmission to the fifth station STA5. The PTS frame 1512 may include at least one of a transmitter address (that is, an address of the fifth station STA5), period information for stopping transmission of the frame, and a receiver address. The PTS frame 1512 may be transmitted in a broadcast method, a multicast method, or a unicast method.

Meanwhile, the sixth station STA6 may receive the PTS frame 1512 from the fifth station STA5. The sixth station STA6 may obtain the transmitter address from the PTS frame 1512 and may not transmit the frame to the fifth station STA5 indicated by the transmitter address. Further, the sixth station STA6 may further acquire period information in which the transmission of the frame is stopped from the PTS frame 1512, and in this case, the fifth station STA5 indicated by the transmitter address during the period in which the transmission of the frame is stopped. It may not transmit the frame. The period information in which the transmission of the frame is stopped may indicate from the end of reception of the PTS frame 1512 to the start of reception of the response to the data frame 1507.

Embodiments of the present invention are implemented in the form of program instructions that can be executed through various computer means and can be recorded in computer readable media. Computer-readable media may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the embodiments of the present invention, or may be known and usable by those skilled in computer software.

The computer readable medium may refer to a hardware device specially configured to store and execute program instructions, such as a ROM, RAM, and flash memory. The hardware device may be configured to operate with at least one software module to perform operations according to embodiments of the present invention, and vice versa. Program instructions may refer to high-level language codes that can be executed on a computer based on an interpreter, etc., as well as machine language codes made by a compiler.

Although described with reference to the above embodiments, those skilled in the art understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. Will be able to.

Claims (20)

delete delete delete delete delete delete A method for transmitting a frame performed in a first station,
Receiving a first frame from a second station;
Obtaining a receiver address of the first frame from the first frame; And
If the receiver address of the first frame does not indicate the first station, determining whether the third station indicated by the receiver address is an interfering station or a non-interfering station based on a list of previously generated interference/non-interference stations ; And
In response to determining that the third station is a non-interfering station, transmitting a second frame after a first preset time from the point in time when the reception of the first frame is completed.
Transmitting the second frame;
Obtain received power information for the third frame transmitted by the third station from the interference / non-interference station list,
Search for a channel in consideration of the received power information for the first preset time,
When there is no signal exceeding a preset signal size during the first preset time, the second frame is transmitted after the first preset time.
The method according to claim 7,
The first frame,
A frame transmission method, which is a request to send (RTS) frame, a data frame, or a block acknowledgment request (BAR) frame. The method according to claim 7,
The interference/non-interference station list includes at least one station that transmits the response of the first frame within a second preset time, and the non-interference station list among the interference/non-interference station list is the first And at least one station that failed to transmit a response of one frame within a second preset time.
The method according to claim 9,
The second preset time is a short inter-frame space (SIFS), frame transmission method.
delete delete The method according to claim 7,
The first preset time,
A method for transmitting a frame, which is a distributed coordination function (DCF) inter-frame space (DIFS), a point coordination function (PCF) inter-frame space (PIFS) or an arbitration inter-frame space (AIFS).
The method according to claim 7,
The second frame is a frame requesting to stop transmitting the frame to the first station.
The method according to claim 14,
The second frame,
And at least one of a transmitter address of the second frame, period information at which transmission of the frame is stopped, and a receiver address of the second frame.
As a first station,
A processor;
And a memory in which at least one program command executed through the processor is stored,
The at least one program instruction,
Receiving a first frame from a second station;
Obtaining a receiver address of the first frame from the first frame;
Determining whether the third station indicated by the receiver address is an interfering station or a non-interfering station based on a pre-generated list of interference/non-interference stations; And
In response to determining that the third station is a non-interfering station, transmitting a second frame after a first preset time from the point in time when the reception of the first frame is completed.
Transmitting the second frame;
Obtain received power information for the third frame transmitted by the third station from the interference / non-interference station list,
Search for a channel in consideration of the received power information for the first preset time,
The first station transmits the second frame after the first preset time when there is no signal exceeding a preset signal size during the first preset time.
The method according to claim 16,
The interference/non-interference station list includes at least one station that transmits the response of the first frame within a second preset time, and the non-interference station list among the interference/non-interference station list is the first A first station, comprising at least one station that failed to transmit a response of one frame within a second preset time.
delete delete The method according to claim 16,
The second frame is a frame requesting to stop transmitting a frame to the first station.

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