WO2019124970A1

WO2019124970A1 - Method and device for transmitting frame on basis of fdr in wireless lan system

Info

Publication number: WO2019124970A1
Application number: PCT/KR2018/016235
Authority: WO
Inventors: 송태원; 김서욱; 김정기; 류기선; 장인선; 최진수
Original assignee: 엘지전자 주식회사
Priority date: 2017-12-20
Filing date: 2018-12-19
Publication date: 2019-06-27

Abstract

A method and device for transmitting a frame on the basis of FDR in a wireless LAN system is proposed. A first STA generates a list indicating that the first STA can perform FDR with a second STA. The list is generated by detecting a first frame transmitted and received between an AP and the second STA. The first STA transmits the list to the AP. The AP transmits a second frame to the second STA, and concurrently the first STA transmits a third frame to the AP. The second frame and the third frame are transmitted on the basis of the FDR.

Description

Method and apparatus for transmitting frames based on FDR in a wireless LAN system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for performing FDR in a wireless LAN system, and more particularly, to a method and apparatus for transmitting frames using an asymmetric FDR scheme in a wireless LAN system.

Discussions are under way for the next generation wireless local area network (WLAN). In the next generation WLAN, 1) enhancement of IEEE 802.11 PHY (physical) layer and MAC (medium access control) layer in the 2.4GHz and 5GHz bands, 2) improvement of spectrum efficiency and area throughput throughput, and 3) to improve performance in real indoor and outdoor environments, such as environments where interference sources exist, dense heterogeneous networks, and environments with high user loads.

The environment that is considered mainly in the next generation WLAN is a dense environment with AP (access point) and STA (station), and improvement in spectrum efficiency and area throughput is discussed in this dense environment. In addition, the next generation WLAN is concerned not only with the indoor environment but also with the actual performance improvement in the outdoor environment which is not considered much in the existing WLAN.

Specifically, the next-generation WLAN is interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment, And STA in a dense environment.

In addition, in the next generation WLAN, improvement of system performance in an overlapping basic service set (OBSS) environment, improvement of outdoor environment performance, and cellular offloading will be actively discussed rather than improvement of single link performance in one basic service set (BSS) It is expected. The directionality of this next generation WLAN means that the next generation WLAN will have a technology range similar to that of mobile communication. Considering the recent discussions of mobile communication and WLAN technology in the area of small cell and D2D (direct-to-direct) communication, it is expected that the technological and business convergence of next generation WLAN and mobile communication will become more active.

The present invention proposes a method and apparatus for transmitting a frame based on FDR (Full-Duplex Radio) in a wireless LAN system.

An example of the present invention proposes a technique of transmitting a frame using an asymmetric FDR scheme.

An example of this specification is a procedure flow diagram for transmitting a frame based on FDR (Full-Duplex Radio).

The present embodiment proposes a MAC protocol based on the FDR operation when it is assumed that self-interference, which is a great obstacle in performing FDR, can be successfully removed from the PHY layer. The FDR operation is symmetric FDR and asymmetric FDR. In the following, the description is limited to the asymmetric FDR.

In the asymmetric FDR, there are an FDR in which the STA starts transmission first and an FDR in which the AP initiates transmission first. Hereinafter, the description will be limited to the FDR (AP-initiated FDR) in which the AP first starts transmission.

First, in summary terms, a first STA may correspond to a secondary transmitter (STX) attempting a secondary transmission and a second STA may correspond to a primary transmission Or receive the first transmission frame of the AP.

The first STA (station) generates a list that it can perform the FDR with the second STA. The list is generated by sensing a first frame transmitted and received between an access point (AP) and the second STA. That is, the first STA overhears the first frame received by the AP and the second STA, and stores the identifier (ID) of the second STA as a list. Specifically, the first STA can receive a frame from the AP and know that it is in coverage. However, the first STA may not receive a frame from the second STA. This is because the first STA and the second STA are outside of one-hop. Thus, the first STA can not hear the frame from the AP while the frame from the second STA can not be eavesdropped. Through this information, the first STA is far enough away from the second STA that it is determined that the possibility of collision, such as inter-node interference, is low, and the list can be whitelisted to be able to perform an FDR with the second STA have. If the first STA and the second STA are within one hop, the possibility of collision such as inter-node interference increases, so that the list can be blacklisted that the FDR can not be performed with the second STA. However, in the present embodiment, the second STA is limited to being whitelisted.

The first STA sends the list to the AP. Since the identifier of the second STA is included in the list, the AP receiving the list can know that the first STA can perform the FDR with the second STA.

In addition, the first STA may send a buffer status feedback to the AP. The buffer status feedback may be transmitted to notify the AP if data to be transmitted by the first STA exists in the buffer. In addition, the buffer status feedback may be transmitted in the same frame as the list. In addition, the buffer status feedback may be transmitted in a frame different from the frame in which the list is transmitted.

At the same time that the AP transmits the second frame to the second STA, the first STA transmits the third frame to the AP. The second frame and the third frame are transmitted based on the FDR.

The first STA notifies the list and the buffer status feedback to the AP so that the AP can perform the FDR by explicitly specifying the first STA corresponding to the STX. That is, if the AP has a DL frame (second frame) to transmit to the second STA and the AP knows that the first STA and the second STA are suitable to perform the FDR operation based on the list and the buffer status feedback , The AP may specify the identifier of the first STA corresponding to STX in the DL frame (second frame) so that the first STA may attempt to FDR. Thus, the second frame may include the identifier of the first STA and the identifier of the second STA.

If the first STA does not inform the AP with the list and the buffer status feedback, the STAs corresponding to the STX may attempt the second transmission autonomously (opportunistic) without explicit specification of the AP.

However, the transmission time of the second frame may be earlier than the transmission time of the third frame. This indicates that the transmission of the second frame corresponds to a primary transmission and the transmission of the third frame corresponds to a secondary transmission. The second frame starts to be transmitted earlier than the third frame, and the second frame and the third frame can be simultaneously transmitted based on the FDR.

Also, the channel measurement for self-interference cancellation may be completed based on the transmission of the second frame before the third frame is transmitted. In this embodiment, it is assumed that the AP performing the FDR can perform self interference cancellation.

When the first frame is transmitted in the downlink, the first frame may include a Request To Send (RTS) frame or a data frame. That is, the first STA may eavesdrop or detect the RTS frame or data frame transmitted by the AP to the second STA, and store the identifier of the second STA as a list.

When the first frame is transmitted in the uplink, the first frame includes a clear to send (CTS) frame, a quality of service (QoS) null frame, or a power save (PS) . That is, the first STA may eavesdrop upon or detect the CTS frame, the QoS null frame, or the PS poll frame received from the second STA, and store the identifier of the second STA as a list.

Also, the list may be generated based on Received Signal Strength Indication (RSSI) of the detected first frame.

This specification proposes a scheme for transmitting frames using an asymmetric FDR scheme in a wireless LAN system.

According to the embodiment proposed in the present specification, it is possible to specify a STA attempting a second transmission based on FDR to reduce the probability of collision with the STA attempting the first transmission, and to achieve a high throughput.

1 is a conceptual diagram illustrating a structure of a wireless local area network (WLAN).

2 is a diagram showing an example of a PPDU used in the IEEE standard.

3 is a diagram showing an example of an HE PPDU.

FIG. 4 shows an example in which an AP receiving a PS-Poll frame operates as an immediate response.

5 shows an example in which an AP receiving a PS-Poll frame operates as a deferred response.

6 shows an example in which the AP performs the DTIM operation.

7 shows active scanning and passive scanning procedures in a wireless LAN system.

8 shows an example of Symmetric FDR operation.

9 shows an example of an asymmetric FDR operation.

10 shows an example of the Asymmetric FDR operation initiated by the STA.

Figure 11 shows an example of an Asymmetric FDR operation initiated by an AP.

12 shows an example in which a STA that receives a downlink frame from an AP creates a whitelist.

FIG. 13 shows an example in which a STA that receives an uplink frame from another STA creates a whitelist.

14 shows an example in which the STA records another STA on a black list.

FIG. 15 is an example in which a STA that listens to a PS-Poll frame or a QoS Null frame from another STA records another STA in a black list.

FIG. 16 shows an example in which the STA creates a whitelist by confirming the RSSI of the eavesdropped frame.

17 shows an example of a topology of an Opportunistic Asymmetric FDR operation initiated by an AP.

FIG. 18 shows an example of an opportunistic asymmetric FDR operation initiated by an AP considering the FDR performance probability of another STA.

FIG. 19 shows an example of an opportunistic asymmetric FDR operation initiated by an AP considering random waiting.

20 shows an example of an Opportunistic Asymmetric FDR operation initiated by an AP considering access category differentiation.

21 shows an example of a topology of the deterministic asymmetric FDR operation initiated by the AP.

22 shows an example of the Deterministic Asymmetric FDR operation initiated by the AP.

23 shows an example of deterministic asymmetric FDR operation initiated by an AP considering RTS / CTS.

24 shows an example of a topology of deterministic asymmetric FDR operation initiated by the STA.

25 shows an example of deterministic asymmetric FDR operation initiated by the STA.

FIG. 26 shows an example of deterministic asymmetric FDR operation initiated by the STA in consideration of RTS / CTS.

FIG. 27 is a flow chart of a procedure for transmitting a frame based on the FDR (Full-Duplex Radio) according to the present embodiment.

28 shows a transmitting apparatus for implementing this embodiment.

FIG. 29 shows a procedure of transmitting a frame based on the FDR according to the present embodiment.

30 shows a receiving apparatus for implementing this embodiment.

The upper part of FIG. 1 shows the structure of an infrastructure basic service set (BSS) of Institute of Electrical and Electronic Engineers (IEEE) 802.11.

1, the WLAN system may include one or more infrastructure BSSs 100 and 105 (hereinafter, BSS). The BSSs 100 and 105 are a set of APs and STAs such as an access point 125 and an STA1 (station 100-1) capable of successfully synchronizing and communicating with each other. The BSS 105 may include one or more associatable STAs 105-1 and 105-2 in one AP 130. [

The BSS may include at least one STA, APs 125 and 130 providing a distribution service, and a distribution system (DS) 110 connecting a plurality of APs.

The distributed system 110 may implement an extended service set (ESS) 140 that is an extended service set by connecting a plurality of BSSs 100 and 105. ESS 140 may be used to refer to one network in which one or more APs 125 and 230 are connected through a distributed system 110. [ An AP included in one ESS 140 may have the same service set identification (SSID).

A portal 120 may serve as a bridge for performing a connection between a wireless LAN network (IEEE 802.11) and another network (for example, 802.X).

A network between the APs 125 and 130 and a network between the APs 125 and 130 and the STAs 100-1, 105-1 and 105-2 may be implemented in the BSS as shown in the upper part of FIG. However, it is also possible to establish a network and perform communication between the STAs without the APs 125 and 130. [ An ad-hoc network or an independent basic service set (IBSS) is defined as a network that establishes a network and establishes communication between STAs without APs 125 and 130. [

1 is a conceptual diagram showing IBSS.

1, the IBSS is a BSS operating in an ad-hoc mode. Since IBSS does not include APs, there is no centralized management entity. That is, in the IBSS, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner. In the IBSS, all the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be mobile STAs, and the access to the distributed system is not allowed, network.

The STA is an arbitrary functional medium including a medium access control (MAC) conforming to IEEE (Institute of Electrical and Electronics Engineers) IEEE 802.11 standard and a physical layer interface for a wireless medium. May be used to mean both an AP and a non-AP STA (Non-AP Station).

The STA may be a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit Mobile Subscriber Unit), or simply a user.

Meanwhile, the term 'user' may be used in various meanings. For example, the term 'user' may be used to mean an STA participating in uplink MU MIMO and / or uplink OFDMA transmission in wireless LAN communication, But is not limited thereto.

2 is a diagram showing an example of a PPDU used in the IEEE standard.

As shown, various types of PPDU (PHY protocol data unit) are used in IEEE a / g / n / ac standards. Specifically, the LTF and STF fields included training signals, SIG-A and SIG-B included control information for the receiving station, and the data field included user data corresponding to the PSDU.

This embodiment proposes an improved technique for the signal (or control information field) used for the data field of the PPDU. The signal proposed in this embodiment can be applied on the HE PPDU (high efficiency PPDU) according to the IEEE 802.11ax standard. That is, the signal to be improved in this embodiment may be HE-SIG-A and / or HE-SIG-B included in the HE PPDU. Each of HE-SIG-A and HE-SIG-B can also be expressed as SIG-A, SIG-B. However, the improved signal proposed by the present embodiment is not necessarily limited to the HE-SIG-A and / or HE-SIG-B standards, and various control and control schemes including control information in a wireless communication system, It is applicable to data fields.

3 is a diagram showing an example of an HE PPDU.

The control information field proposed in this embodiment may be HE-SIG-B included in the HE PPDU as shown in FIG. The HE PPDU according to FIG. 3 is an example of a PPDU for multiple users. The HE-SIG-B is included only for multi-user, and the corresponding HE-SIG-B can be omitted for a PPDU for a single user.

As shown, an HE-PPDU for a Multiple User (MU) includes a legacy-short training field (L-STF), a legacy-long training field (L-LTF) (HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF) , A data field (or MAC payload), and a Packet Extension (PE) field. Each field may be transmitted during the time interval shown (i.e., 4 or 8 占 퐏, etc.).

The IEEE 802.11 standard provides a power saving mechanism to increase the lifetime of a WLAN STA. For power saving, WLAN STA operates in two modes, active mode and sleep mode. Active mode refers to a state where normal operation such as frame transmission / reception or channel scanning is possible. On the other hand, in the sleep mode, power consumption is extremely reduced, so frame transmission and reception is impossible and channel scanning is impossible. Normally, the basic operation principle is to reduce power consumption by switching to active mode only when WLAN STA is in sleep mode.

As long as possible in sleep mode, the power consumption is reduced and the lifetime of WLAN STAn is increased. However, in the sleep mode, the frame condition can not be operated because the frame can not be transmitted or received. If there is a frame to be transmitted in the sleep mode, it is necessary to transmit the frame by switching to the active mode, so that a big problem does not occur. However, if the station is in sleep mode and the AP has a frame to send to the STA, it is not possible for the STA to receive it and to know that there is a frame to receive. Therefore, the STA should operate in receive mode by switching to active mode occasionally to receive the frame if it exists. The AP shall inform the STA of the existence of frames to be sent to the STA at that time.

The WLAN STA periodically awakes in sleep mode to receive a beacon frame from the AP to know that it has a frame to receive. The AP uses the TIM element of the beacon frame to inform each STA of the frame to receive. There are two types of TIM elements: TIM is used to inform unicast frames, and DTIM is used to inform multicast / broadcast frames.

The STA knows that there is a frame to send to the AP through the TIM element of the beacon frame, and transmits the PS (Power Save) -Poll frame through contending. The AP receiving the PS-Poll frame operates by selecting Immediate Response or Deferred Response depending on the situation.

FIG. 4 shows an example in which an AP receiving a PS-Poll frame operates as an immediate response. 5 shows an example in which an AP receiving a PS-Poll frame operates as a deferred response.

Immediate Response transmits the data frame immediately after the SIFS time after receiving the PS-Poll frame as shown in FIG. When receiving normally, the STA sends an ACK frame after SIFS and switches to sleep mode again.

If the AP does not prepare the data frame for SIFS time after receiving the PS-Poll frame, select Deferred Response. As shown in FIG. 5, when an ACK frame is first transmitted and then a data frame is prepared, the data frame is contended and transmitted to the STA. The STA that normally receives the data frame transmits the ACK frame and then switches back to sleep mode.

6 shows an example in which the AP performs the DTIM operation.

On the other hand, since DTIM (Delivery Traffic Indication Message) is a multicast / broadcast frame, data frame transmission immediately follows the beacon frame without PS-Poll frame transmission / reception as shown in FIG.

The WLAN STA is assigned an association ID (AID) while establishing an association with the AP. AID is unique within a BSS and can now have a value between 1 and 2007. 14bit is allocated for AID, so it can be used up to 16383, but the value of 2008 ~ 16383 is reserved.

In WLAN, scanning procedures are passive scanning and active scanning. Passive scanning is performed through a beacon frame in which the AP periodically broadcasts. Typically, an AP in a WLAN broadcasts a beacon frame every 100 msec, and this beacon frame contains information about the current network. To obtain this information, the non-AP STA will passively wait for the beacon frame to be received on that channel. By receiving the beacon frame, the non-AP STA that has obtained the information about the network will finish scanning on the corresponding channel. Passive scanning is advantageous because the non-AP STA only needs to receive a beacon frame without having to transmit another frame, so the overall overhead is small. However, there is a disadvantage that the scanning execution time increases in proportion to the beacon frame period.

Active scanning is a non-AP STA that actively broadcasts a probe request frame on the corresponding channel and requests network information from all APs that receive it. After receiving the probe request frame, the AP waits for a random time to prevent frame collision, and transmits the network information to the corresponding non-AP STA in the probe response frame. Upon receiving this information, the non-AP STA completes the scanning process by obtaining the network information. Active scanning has the advantage of being able to finish scanning relatively quickly. However, as additional frame sequences are needed, the overall network overhead increases.

After the scanning process, the non-AP STA selects the network according to its own criteria and establishes authentication with the AP. The authentication process consists of two-way handshaking. Through the authentication process, the non-AP STA and the AP authenticate each other and establish an association.

The association process consists of two-way handshaking. First, the non-AP STA transmits an association request frame to the AP. The transmitted association request frame contains information about the capability of the non-AP STA. Based on this, the AP determines whether the non-AP STA can be supported. After determining the AP, the AP sends to the non-AP STA an association response frame containing information on whether or not the association request is acceptable, its reason, and capability information that it can support. If the association is well established, the normal transmission / reception is performed. If the association is not established, the association process may be attempted again based on the reason, or association with another AP may be attempted.

8 shows an example of Symmetric FDR operation. 9 shows an example of an asymmetric FDR operation.

Recently, Full-Duplex Radio (FDR) technology has been actively researched to enable simultaneous transmission / reception between one transceiver and another. If FDR is used, it can theoretically double the performance of the MAC layer without using FDR, ie, Half-Duplex. However, one of the major obstacles to FDR is self-interference, which means that a signal sent by a particular STA is received back to the STA and interferes with the signal it originally intended to receive. Many studies have demonstrated cancellation performance of more than 100dB at the present signal level. If the self-interference cancellation is successfully achieved in the PHY layer, a MAC protocol based on the FDR operation is also required. There are two main types of FDR MAC, Symmetric FDR and Asymmetric FDR. 8 and 9 show examples of operations of Symmetric and Asymmetric FDR.

In the case of Symmetric FDR, each transmission and reception occurs at both terminals. That is, it is easier to implement than Asymmetric, but there is a disadvantage that there is data to be sent to both terminals precisely. On the other hand, Asymmetric FDR has relatively more opportunities to occur than symmetric FDR because two transmissions occur in different pairs of terminals, but the transmission of Node A -> Node B in FIG. 9 causes inter-node interference in reception of Node C Therefore, the terminal to perform the FDR must be well selected.

This asymmetric FDR can be divided into STA-initiated in which the UE first initiates transmission and AP-initiated in which the AP initiates transmission first. Figures 10 and 11 below illustrate examples of STA-initiated FDR and AP-initiated FDR. 10 shows an example of the Asymmetric FDR operation initiated by the STA. Figure 11 shows an example of an Asymmetric FDR operation initiated by an AP.

In the case of FIG. 10, when a specific STA seizes a channel and attempts a primary transmission to an AP, the AP detects that a simultaneous transmission of a secondary transmission Full duplex transmission is performed after determining the receiving STA.

As mentioned above, it is important to select an FDR transmission pair that minimizes inter-node interference in order to demonstrate the performance of Asymmetric FDR. 11, in the case of the AP-initiated Asymmetric FDR, the first transmission is a transmitter, the STA is a receiver, and the second transmission is a STA different from the STA participating in the first transmission. There are deterministic methods in which the AP identifies STAs of the secondary transmitter (STX), and opportunistic methods in which STAs autonomously perform secondary transmission autonomously. In the deterministic method, since the STX is specified, the collision probability is significantly lower than the opportunistic method, and the high throughput can be achieved. However, the computational complexity for selecting the appropriate STX is high and additional fields or indicators for specifying the STX are required. On the other hand, Opportunistic method is computational complexity because STA autonomously computes, but there is a possibility of collision when two or more STAs try to transmit. In this specification, we propose the operation procedure of AP-initiated opportunistic asymmetric FDR MAC.

In this embodiment, a structure of AP-initiated opportunistic asymmetric MAC based on FDR (Full-Duplex Radio) is proposed. Opportunistic MAC does not specify the STA that the AP performs the secondary transmission, and the STAs decentralize the secondary transmission. Through this MAC protocol, STAs can perform full-duplex operation without central processing algorithm, which can exert the advantage of FDR and guarantee high throughput.

1. Operation Procedure

In this specification, it is assumed that a terminal performing FDR (in this specification, AP only) can perform self-interference cancellation. Opportunistic AP-initiated Asymmetric MAC is implemented as follows.

(1) When the STA hears the frames exchanged with other STAs existing in the surrounding area, the STA IDs are stored in a list according to a series of processes. The ID of the STA is all possible if it can operate with an Association ID (AID), a MAC Address, or a unique ID that identifies another STA in any format. The list can be: 1) a whitelisting method (which tells the other STAs in the list that a FDR is available) and 2) a blacklist method (which tells the other STAs in the list that FDR is not possible).

(2) When downlink data is generated, the AP tries to transmit according to the existing 802.11 baseline spec.

(3) When the STA confirms the destination through the downlink data of the AP, the STA performs channel access after a probabilistic or arbitrary waiting time based on the list created by the STA only when there is data to be transmitted for uplink, It tries to send uplink to. (Since it is AP-initiated, STX always sends uplink.)

2. Technical Example

Embodiments of the element technologies necessary for the operation of the present invention will be described below.

(1) Create a list

The STA recognizes and manages one-hop neighbors in two ways: one is white list method and the other is black list method. For example, if there is STA2 in the list from STA1, or in STA2 or STA3 -> AP -> STA1, the whitelist scheme is possible. In the blacklist scheme, for example, STA2 and STA3 Is possible, except for STA2 or STA3 -> AP -> STA1 FDR.

There are many ways to create a whitelist or a blacklist for each STA, but the following methods are possible

A. Frame unit bounded by SIFS pair

SIFS is the smallest inter-frame space (IFS) used between pairs of frames that require immediate response. The STA that is used in front of the PPDU including the DATA-ACK, the RTS (Request To Send), the CTS (Clear To Send), and the BlockAck can whitelist the frames as shown in FIGS. 12 and 13 below.

If a particular STA lists another STA on a whitelist, it can be categorized into two.

FIG. 12 illustrates a case where a STA describes a whitelist in the case of a downlink frame pair from an AP. Taking FIG. 12 as an example, STA2 is far enough away from STA1 that it can be listed in the whitelist, which occurs when the RTS and DATA frame are overheard. In this case, an RTS-CTS pair must be used. This is because if the DATA frame is overheated and the ACK frame is not received, STA1 and STA2 can not be determined to be hidden because STA1 does not transmit ACK due to collision or error of DATA frame.

In the second case, the case where the STA lists the whitelist in the uplink frame pair from another STA is shown in FIG. Since the CTS or ACK frame can not be used alone and is necessarily used as a response to the RTS or DATA frame, the STA who cried over the CTS or ACK frame can be considered to have not eavesdropped with the RTS and DATA frame immediately before. Therefore, the STA that receives the CTS and ACK transmitted by the AP can whitelist the STA corresponding to the reception address of the frame.

It is also possible to manage similar cases in a blacklist. 14 shows an example in which the STA records another STA on a black list.

If the STA2 hears an uplink frame from another STA, it can be estimated that the STA is between the STA and the one-hop, so that the STA can be directly blacklisted. In FIG. 14, when the CTS frame of the STA1 is heard or the data from the STA3 is heard, the corresponding STA is listed in the black list. In the case of black list, unlike the whitelist, since only the transmission of the adjacent STA can be recorded in the blacklist, it can be recorded in the black list even if a frame such as PS-Poll or QoS Null is detected in addition to the pair bundled with SIFS. The above situation is illustrated by way of example in FIG. 15 below. FIG. 15 is an example in which a STA that listens to a PS-Poll frame or a QoS Null frame from another STA records another STA in a black list.

Through the above method, a specific STA can determine which STA is hidden in the surrounding area, and informs the AP of the STA that the AP can determine STX.

This list registration method is not limited to the above example and can be applied to any frame pair that needs immediate response. Also, in transmitting the list to the AP in the above manner, the identifier for distinguishing the neighboring STAs may be a partial AID format obtained through the VHT-SIG-A preamble or a MAC address format obtained through the MAC header . Since the AP knows all the information about the associated STA, it can manage the list without any problem even if it receives any type of information.

B. Using Received Signal Strength Indication (RSSI)

The above-described RTS / CTS or DATA / ACK pair can not be used for creating a whitelist or a blacklist. For example, when the AP and STA2 are close to each other and the RSSI is very large, and STA1 and STA2 are not in a hidden node relationship but the RSSI of the received signal is very small, when the AP-> STA2 transmission is performed, Can happen. In order to support this case, a list management method based on RSSI can be considered. In FIG. 16, the SIFS pair frame pair as well as the list management using the RSSI are briefly illustrated. FIG. 16 shows an example in which the STA creates a whitelist by confirming the RSSI of the eavesdropped frame.

When creating the whitelist / blacklist of the STA, the STA can create a list based on the signal strength from the AP or other STAs in the vicinity, that is, the RSSI. It is also possible to determine whether to make a list by setting the ratio or difference of the RSSIs of the frames that are intercepted, or if it is determined that the STA can not be FDR if the strength of the received frame is more than a predetermined value, .

(2) FDR sending and receiving process

The FDR transmission operation process including a series of processes is briefly shown in FIG. 17 to FIG. Each STA has a whitelist or a blacklist through the list management method. (In opportunistic mode, the STA only holds the list, not the AP)

17 shows a basic transmission / reception process of AP-initiated opportunistic MAC. When the STA attempts to transmit the downlink frame to the STA1 in the state where the STA creates the whitelist or the blacklist through the above embodiment, the STAs (STA2 and STA3 in FIG. 17) FDR, that is, STX, through its own list. If STA2 concludes that it can not do FDR with STA1 through the list, or if there is no data in the buffer, it works by setting NAV only without attempting FDR, and STA3 can perform FDR with STA1 through list , The FDR is performed by transmitting the uplink data to the AP.

FIG. 18 shows a case where there are two or more STAs capable of attempting FDR as another example. When the AP sends downlink data, it concludes that STA1 can not perform FDR with STA1 through the list, or if there is no data in the buffer, it operates by setting only NAV without attempting FDR. STA2 and STA3 determined that they could perform FDR with STA1 through the list. In this example, the STA probabilistically describes a situation in which two or more FDRs are prepared for a collision by attempting an uplink FDR. Each STA determines whether to transmit via a given probability p, which works similar to the p-persistent CSMA model. In this example, the STA2 has not attempted to transmit, and the STA3 can see that the FDR is made by attempting to transmit.

FIG. 19 shows an example in which another anti-collision technique is applied. The CSMA / CA scheme, similar to the 802.11 baseline spec, allows two or more STAs to attempt uplink FDR to reduce the probability of collisions. Random waiting Setting method and setting range can all be set the same, or can be set at the discretion of AP or service provider using CW set for each access category (AC). The STA that succeeded in channel access can set the DATA length considering the time that it waited before.

In addition to the probability-based scheme and the random wait time scheme, FDR based access category (AC) of the frame is also possible. 20 shows an example of an Opportunistic Asymmetric FDR operation initiated by an AP considering access category differentiation.

FIG. 20 illustrates an example of an AC differential-based FDR. The example is based on the four ACs currently available in the 802.11 baseline spec. The STAs can know the AC of the frame while receiving the frame from the AP. The STA can participate in the FDR only if the buffered frame of the STA wishing to participate in the FDR is equal to or higher than the AC of the frame from the AP. The detailed settings may vary depending on the environment or service provider settings.

Also, in this specification, we propose the operation procedure of deterministic asymmetric FDR MAC applicable in both STA-initiated and AP-initiated environments.

The present embodiment proposes a deterministic asymmetric MAC structure based on FDR (Full-Duplex Radio). The deterministic MAC determines asymmetric FDR transmission between the AP and the STA after the AP identifies the STA performing the secondary transmission. This MAC protocol can fully exploit the benefits of FDR and ensure high throughput.

1. Operation Procedure

In the present invention, it is assumed that a terminal performing FDR (in the present specification, AP only) can perform self-interference cancellation. Deterministic AP-initiated Asymmetric MAC is implemented as follows.

(2) The STA can inform the AP when the data to be transmitted in the uplink exists in the buffer (Buffer status feedback). This process can use the existing method (QoS Control field or BSR Control field in HT Control field) existing in 802.11 baseline spec, or it can be done by other methods.

(3) The STA delivers the list collected in (1) to the AP. This can occur simultaneously with the process of (2) (the way it is included in the Frame Body field), or it can happen separately.

(4)

A. If the AP occupies the channel for the downlink transmission, the AP checks the list collected in (2) and (3), the buffer status feedback, and the downlink data that the AP should send to the STA , STA IDs to participate in the FDR are specified in downlink data and transmitted.

B. (STA-Initiated) When the STA occupies the channel for uplink transmission, the STA attempts to transmit the uplink.

(5)

A. (For AP-initiated) The STA that is specified in the downlink data, that is to say that the FDR is available from the AP, tries to send an uplink to the AP (STA1 sends an uplink to the AP in FIG.

B. (In the case of STA-initiated) The AP that started receiving the uplink data from the STA attempts to send the downlink based on the list collected in (2) and (3) and the downlink data to be sent to the STA (AP sends downlink transmission to STA2 in FIG. 10).

2. Technical Example

Embodiments of the element technologies necessary for the operation procedure proposed in the present specification will be described below.

(1) Create a list

Deterministic Asymmetric FDR The method by which the STA creates the list in the course of the MAC operation is the same as the method of creating the list in the operation process of the AP-initiated opportunistic asymmetric FDR MAC. Accordingly, the STA performing the deterministic asymmetric FDR operation can perform the list management by using the whitelist or the black list creation method described in FIGS. 12 to 16 in the same manner.

A. Frame unit bounded by SIFS pair

SIFS is the smallest inter-frame space (IFS) used between pairs of frames that require immediate response. It is used in front of PPDUs including DATA-ACK, RTS-CTS, and BlockAck, and the STA who overhears a frame can create a whitelist as shown in FIGS. 12 and 13 below.

B. Using Received Signal Strength Indication (RSSI)

(2) List delivery

Deterministic Asymmetric FDR In the operation of the MAC, unlike the operation procedure of the AP-initiated opportunistic asymmetric FDR MAC, the STA delivers the created list to the AP. It can be delivered periodically or otherwise at the request of the AP. When the STA informs the AP of its buffer status through the QoS Control field, the BSR Control field within the HT Control field, or other methods, the STA may also include the list in the frame body of the corresponding frame. The buffer status of each STA is informed by using the QoS Control field or the HT Control field, and the created list can be transmitted by including it in the Frame Body field.

(3) FDR sending and receiving process

The FDR transmission operation process including a series of processes is briefly shown in FIGS. 21 to 26 below. Figs. 21 to 23 show examples of AP-initiated, and Figs. 24 to 26 show examples of STA-initiated.

21 shows an example of a topology of the deterministic asymmetric FDR operation initiated by the AP. 22 shows an example of the Deterministic Asymmetric FDR operation initiated by the AP. 23 shows an example of deterministic asymmetric FDR operation initiated by an AP considering RTS / CTS.

The list and buffer status feedback in FIG. 21 may exist in the same frame or may be separately transmitted to the AP. If there is downlink data to the STA1, the AP knows that the STA2 is suitable for the FDR based on the collected list and the buffer status feedback, the AP must specify the STX ID in the corresponding frame so that the STX can try the FDR . For example, in FIG. 22 and FIG. 23, the DATA transmitted from the AP to the STA1 must include the ID of the primary receiver STA1 and the ID of the secondary transmitter STA2. The STX ID can be provided in the SIG format in the current PHY preamble or in the Address 4 field in the MAC frame or by defining the format of the new RTS frame to inform STX in the RTS phase or in other ways can do. In addition, since the AP must simultaneously receive from the STA2 during the transmission process toward the STA1, the AP performs self-interference cancellation based on the transmission of the AP-> STA1 before the secondary transmission of the STA2-> AP occurs The channel measurement for the channel must be completed. Or if there is a previously measured channel measurement.

24 to 26 show examples of STA-initiated deterministic asymmetric FDR.

24 shows an example of a topology of deterministic asymmetric FDR operation initiated by the STA. 25 shows an example of deterministic asymmetric FDR operation initiated by the STA. FIG. 26 shows an example of deterministic asymmetric FDR operation initiated by the STA in consideration of RTS / CTS.

The STA in FIG. 24, when there is uplink data to be transmitted to the AP, attempts to transmit uplink by occupying the channel through channel competition. When the AP successfully decodes the data from the STA, it determines and transmits a SRX (secondary receiver) based on the received list. In comparison with AP-initiated, in the case of STA-initiated, the AP does not need to provide a separate STX ID since it is the secondary transmission. In addition, the AP must perform channel measurement for self-interference cancellation. However, since the AP needs to know the channel information of the signal transmitted by the AP during reception, it is not practical. To solve this problem, if the AP has previously acquired the channel information, a method of using the previous channel information can be used.

In step S2710, the first STA (station) generates a list that it can perform the FDR with the second STA. The list is generated by sensing a first frame transmitted and received between an access point (AP) and the second STA. That is, the first STA overhears the first frame received by the AP and the second STA, and stores the identifier (ID) of the second STA as a list. Specifically, the first STA can receive a frame from the AP and know that it is in coverage. However, the first STA may not receive a frame from the second STA. This is because the first STA and the second STA are outside of one-hop. Thus, the first STA can not hear the frame from the AP while the frame from the second STA can not be eavesdropped. Through this information, the first STA is far enough away from the second STA that it is determined that the possibility of collision, such as inter-node interference, is low, and the list can be whitelisted to be able to perform an FDR with the second STA have. If the first STA and the second STA are within one hop, the possibility of collision such as inter-node interference increases, so that the list can be blacklisted that the FDR can not be performed with the second STA. However, in the present embodiment, the second STA is limited to being whitelisted.

In step S2720, the first STA transmits the list to the AP. Since the identifier of the second STA is included in the list, the AP receiving the list can know that the first STA can perform the FDR with the second STA.

In step S2730, while the AP transmits the second frame to the second STA, the first STA transmits the third frame to the AP. The second frame and the third frame are transmitted based on the FDR.

According to the above-described embodiment, the STA that attempts the second transmission based on the FDR can be specified to reduce the probability of collision with the STA attempting the first transmission, and a high throughput can be achieved.

28 shows a transmitting apparatus for implementing this embodiment.

Referring to FIG. 28, a wireless device is a transmitting device capable of implementing the above-described embodiment, and can operate as an AP. In addition, the wireless device may correspond to a transmitting device that transmits a signal to a user.

28 includes a processor 2810, a memory 2820 and a transceiver 2830 as shown. The illustrated processor 2810, memory 2820 and transceiver 2830 may each be implemented as separate chips, or at least two blocks / functions may be implemented on a single chip.

The transceiver 2830 is a device including a transmitter and a receiver. When a specific operation is performed, only the operation of either the transmitter or the receiver is performed, or both the transmitter and the receiver are performed . The transceiver 2830 may include one or more antennas for transmitting and / or receiving wireless signals. In addition, the transceiver 2830 may include an amplifier for amplifying a received signal and / or a transmitted signal, and a band-pass filter for transmitting on a specific frequency band.

The processor 2810 may implement the functions, processes, and / or methods suggested herein. For example, the processor 2810 may perform the operations according to the embodiment described above. That is, the processor 2810 generates a list for performing the FDR and transmits the list to the AP, and processes the first STA and the second STA to transmit frames based on the FDR. The operation of the processor is as follows.

The first STA (station) generates a list that it can perform the FDR with the second STA. The list is generated by sensing a first frame transmitted and received between an access point (AP) and the second STA. That is, the first STA overhears the first frame received by the AP and the second STA, and stores the identifier (ID) of the second STA as a list.

Processor 2810 may include an application-specific integrated circuit (ASIC), another chipset, logic circuitry, a data processing device, and / or a transducer to convert baseband signals and radio signals. Memory 2820 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

First, in summary terms, STA1 may correspond to a secondary transmitter (STX) that attempts a secondary transmission, STA2 may attempt a primary transmission to the AP, The first transmission frame can be received.

In step S2910, the AP transmits and receives the first frame to the STA2.

In step S2920, the STA1 detects the first frame and generates a list of STAs capable of performing the FDR. That is, the STA1 overhears the first frame received by the AP and the STA2, and stores the identifier (ID) of the STA2 in a list.

In step S2930, STA1 transmits the list to the AP. Since the list includes the identifier of the STA2, the AP receiving the list can know that the STA1 can perform the FDR with the STA2.

Also, the STA1 may transmit a buffer status feedback to the AP. The buffer status feedback may be transmitted to notify the AP if data to be transmitted by the STA1 exists in the buffer. In addition, the buffer status feedback may be transmitted in the same frame as the list. In addition, the buffer status feedback may be transmitted in a frame different from the frame in which the list is transmitted.

In steps S2940 and S2950, while the AP transmits the second frame to the STA2, the STA1 transmits the third frame to the AP. The second frame and the third frame are transmitted based on the FDR.

The STA1 informs the AP of the list and the buffer status feedback so that the AP can perform the FDR by explicitly specifying the STA1 corresponding to STX (deterministic method). That is, if the AP has a DL frame (second frame) to transmit to the STA2 and the AP finds that the STA1 and the STA2 are suitable for performing the FDR operation based on the list and the buffer status feedback, The first STA may attempt to FDR by specifying an identifier of the STA1 corresponding to the STX in the first frame (second frame). Accordingly, the second frame may include an identifier of the STA1 and an identifier of the STA2.

If STA1 does not inform the list and buffer status feedback to the AP, the STAs corresponding to the STX may attempt the second transmission autonomously (opportunistic) without explicit specification of the AP.

When the first frame is transmitted in the downlink, the first frame may include a Request To Send (RTS) frame or a data frame. That is, the STA1 can listen to or sense the RTS frame or the data frame transmitted to the STA2 by the AP, and store the identifier of the STA2 as a list.

When the first frame is transmitted in the uplink, the first frame includes a clear to send (CTS) frame, a quality of service (QoS) null frame, or a power save (PS) . That is, the STA1 can listen to or detect the CTS frame, the QoS null frame, or the PS poll frame received from the STA2 and store the identifier of the STA2 as a list.

30 shows a receiving apparatus for implementing this embodiment.

Referring to FIG. 30, a wireless device is a receiving device capable of implementing the above-described embodiment, and can operate as a non-AP STA. Also, the wireless device may correspond to the above-described user.

30 includes a processor 3010, a memory 3020 and a transceiver 3030, as shown. The illustrated processor 3010, the memory 3020 and the transceiver 3030 may be implemented as separate chips, or at least two blocks / functions may be implemented through one chip.

The transceiver 3030 is a device including a transmitter and a receiver. When a specific operation is performed, only the operation of either the transmitter or the receiver is performed, or both the transmitter and the receiver are performed . The transceiver 3030 may include one or more antennas for transmitting and / or receiving wireless signals. In addition, the transceiver 3030 may include an amplifier for amplifying a received signal and / or a transmitted signal, and a band-pass filter for transmitting on a specific frequency band.

The processor 3010 may implement the functions, processes, and / or methods suggested herein. For example, the processor 3010 can perform the operations according to the above-described embodiment. That is, the processor 3010 receives the list generated for performing the FDR, and processes the FDR-based frames transmitted from the first STA and the second STA based on the list. The operation of the processor is as follows.

The processor 3010 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, a data processing device, and / or a converter for converting baseband signals and radio signals. Memory 3020 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

Claims

A method for transmitting a frame based on a full-duplex radio (FDR) in a wireless LAN system,

Generating a list that a first STA can perform an FDR with a second STA, wherein the list is generated by sensing a first frame transmitted and received between an access point (AP) and the second STA;

The first STA sending the list to the AP; And

The first STA transmitting a third frame to the AP while the AP transmitting a second frame to the second STA,

The second frame and the third frame are transmitted based on the FDR

Way.
The method according to claim 1,

Wherein the second frame includes an identifier of the first STA and an identifier of the second STA

Way.
The method according to claim 1,

The first STA sending a buffer status feedback to the AP,

The buffer status feedback is transmitted in the same frame as the list

Way.
The method according to claim 1,

Wherein the transmission time of the second frame is faster than the transmission time of the third frame

Way.
5. The method of claim 4,

The channel measurement for self-interference cancellation is completed based on the transmission of the second frame before the third frame is transmitted

Way.
The method according to claim 1,

When the first frame is transmitted in the downlink, the first frame includes a Request To Send (RTS) frame or a data frame

Way.
The method according to claim 1,

When the first frame is transmitted in the uplink, the first frame includes a clear to send (CTS) frame, a quality of service (QoS) null frame, or a power save (PS)

Way.
The method according to claim 1,

The list is generated based on Received Signal Strength Indication (RSSI) of the detected first frame

Way.
A first STA (Station) for transmitting a frame based on a Full-Duplex Radio (FDR) in a wireless LAN system,

A transceiver for transmitting or receiving a wireless signal; And

A processor for controlling the transceiver, the processor comprising:

Generating a list indicating that an FDR can be performed with a second STA, the list being generated by sensing a first frame transmitted and received between an access point (AP) and the second STA;

The first STA sends the list to the AP; And

The first STA transmits a third frame to the AP while the AP transmits a second frame to the second STA,

The second frame and the third frame are transmitted based on the FDR

Wireless device.
10. The method of claim 9,

Wherein the second frame includes an identifier of the first STA and an identifier of the second STA

Wireless device.
10. The method of claim 9,

Wherein the processor is configured to send buffer status feedback to the AP,

The buffer status feedback is transmitted in the same frame as the list

Wireless device.
10. The method of claim 9,

Wherein the transmission time of the second frame is faster than the transmission time of the third frame

Wireless device.
13. The method of claim 12,

The channel measurement for self-interference cancellation is completed based on the transmission of the second frame before the third frame is transmitted

Wireless device.
10. The method of claim 9,

When the first frame is transmitted in the downlink, the first frame includes a Request To Send (RTS) frame or a data frame

Wireless device.
10. The method of claim 9,

When the first frame is transmitted in the uplink, the first frame includes a clear to send (CTS) frame, a quality of service (QoS) null frame, or a power save (PS)

Wireless device.
10. The method of claim 9,

The list is generated based on Received Signal Strength Indication (RSSI) of the detected first frame

Wireless device.