KR20220040600A - Apparatus and method for transmitting and receiving ACK in wireless communication system - Google Patents

Abstract

The present invention can provide an ACK transmitting/receiving device in a wireless communication system and a method thereof which transmit a broadcast frame in which whether to additionally transmit a request for an ACK frame or an ACK request frame for requesting the ACK frame is set and determine whether the broadcast frame is retransmitted based on power of a received ACK frame when the ACK frame is received, wherein the ACK frame is transmitted by using the same resources at the same time from each of one or more ACK transmitting devices that receive at least one of the broadcast frame or the ACK request frame, thereby increasing reliability for the broadcast frame.

Description

ACK transceiver and method of a wireless communication system {Apparatus and method for transmitting and receiving ACK in wireless communication system}

The present invention relates to an apparatus and method for transmitting and receiving ACK in a wireless communication system, and to an apparatus and method for transmitting and receiving ACK for a broadcast frame in a wireless communication system.

Recently, with the spread of mobile devices, a wireless LAN technology that can provide a fast wireless Internet service is receiving a lot of attention. Wireless LAN technology is a technology that enables mobile devices such as smart phones, smart pads, laptop computers, portable multimedia players, and embedded devices to wirelessly access the Internet in a short distance based on wireless communication technology.

A standard using a wireless LAN is mainly being developed as an IEEE 802.11 standard by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE 802.11 standard was developed and standardized in such a way that, starting with the initial version supporting 1~2 Mbps, it was revised through subsequent versions. In the IEEE 802.11a revision, up to 54 Mbps is supported using Orthogonal Frequency Division Multiplexing (OFDM) in the 5 GHz band, and IEEE 802.11b is Direct Sequence Spread Spectrum (DSSS). ) method to support a transmission rate of up to 11 Mbps in the 2.4 GHz band where the initial version operates.

Since then, due to the demand for improved speed, the IEEE 802.11n revision including the high throughput (HT) wireless LAN technology operates in the OFDM method, expands the channel bandwidth in the 2.4 GHz band and the 5 GHz band, and MIMO (multiple input multiple output) to improve the maximum transmission speed. As a result, when using 4 SS (spatial steam) and 40 MHz bandwidth, the maximum transmission speed was improved to support up to 600 Mbps.

As the wireless LAN technology has been developed and spread, applications using the wireless LAN technology have been diversified, and a demand for a wireless LAN technology supporting a higher throughput has arisen. Accordingly, the IEEE 802.11ac revision further expands the frequency bandwidth used (up to 160 MHz or 80+80 MHz) and expands the number of supported spatial streams to support a high throughput of 1 Gbps or more (Very High Throughput: VHT) wireless LAN technology is reflected. In addition, the standard supports downlink transmission toward multiple terminals by utilizing MIMO.

Meanwhile, among WLAN technologies, specific operations such as fast handoff (fast BSS transition), fast initial link setup (Fast Initial Link Setup), technology for low-power terminals operating in a band of 1 GHz or less, and WLAN technology for vehicle terminals Standard technology was also developed and reflected, and each standard revision was established. In particular, the wireless LAN technology for the vehicle terminal is reflected in IEEE 802.11p, based on the signal form in IEEE 802.11a and EDCA (Enhanced Distributed Channel Access) in IEEE 802.11e, and operates in the 5.9 GHz band. In addition, based on a 10 MHz bandwidth to suit a mobile terminal with strong mobility, the terminal can directly perform communication between each vehicle terminal without going through an authentication and association process with a base station or an access point (AP). OCB (Outside Context of BSS) is supported.

On the other hand, as more sensors and operations are developed in communication operation for vehicles, applications for the operation are diversified, and there is a demand for higher throughput and transmission distance for the IEEE 802.11p. The need for wireless LAN technology development has increased. Accordingly, IEEE 802.11bd is being developed and standardized to establish a wireless LAN standard for next-generation vehicle communication (Next Generation V2X, NGV). The IEEE 802.11bd aims to support higher throughput, reliability and transmission distance. Accordingly, in IEEE 802.11bd, a technique for transmitting high-capacity data at high speed using a 20 MHz bandwidth to support higher throughput was proposed and reflected, and a signal form for a higher transmission distance was proposed and reflected. became

However, as OCB is supported in vehicle communication, communication between vehicle terminals increases, and a specific vehicle terminal frequently transmits a broadcast frame (or multicast frame, groupcast frame) to a plurality of nearby vehicle terminals. do. In addition, a case in which a roadside device or the like transmits a broadcast frame to a plurality of nearby vehicle terminals frequently occurs.

However, in the existing wireless communication system, even when a vehicle or a roadside device transmits a broadcast frame, it is not possible to check whether nearby terminals have normally received the broadcast frame. That is, an operation capable of increasing transmission reliability for broadcast frame transmission is not clearly defined. In particular, since a retransmission method for frame collision due to an increase in the number of transmitting terminals is not defined, there is a need for improvement.

Korean Patent Registration No. 10-1781194 (Registered on Sep. 18, 2017)

An object of the present invention is to provide an ACK transceiver and method capable of increasing the transmission reliability of a broadcast frame by transmitting an ACK frame request together when transmitting a broadcast frame in a wireless communication system and receiving ACK frames from a plurality of terminals. there is.

Another object of the present invention is to provide an ACK transceiver and method capable of minimizing resource usage for ACK frame transmission by allowing multiple terminals to simultaneously transmit multiple ACK frames using the same resource.

Another object of the present invention is to provide an ACK transceiver and method capable of determining whether a broadcast frame is normally transmitted based on the power of a plurality of ACK frames simultaneously transmitted with the same resource.

In order to achieve the above object, an ACK reception apparatus of a wireless communication system according to an embodiment of the present invention transmits a broadcast frame in which a request for an ACK frame or an additional transmission of an ACK request frame requesting an ACK frame is set, and the When an ACK frame transmitted using the same resource is simultaneously received from each of at least one ACK transmission device that has received at least one of a broadcast frame or an ACK request frame, the broadcast frame is retransmitted based on the power of the received ACK frame to determine whether

The ACK reception apparatus transmits the broadcast frame by setting at least one of a request for the ACK frame or an additional transmission of the ACK request frame in a MAC header of the broadcast frame, and includes a MAC header of the broadcast frame. If it is set to additionally transmit the ACK request frame, the ACK request frame may be transmitted after a predetermined time from the transmission end time of the broadcast frame.

The ACK receiving apparatus transmits by setting whether to additionally transmit a NAK request frame in the MAC header of the broadcast frame or the MAC header of the ACK request frame, and simultaneously from each of the at least one ACK transmitting apparatus receiving the NAK request frame When a NAK frame transmitted using the same resource is received, it may be determined whether the broadcast frame is retransmitted based on a power ratio of the ACK frame and the received NAK frame.

After transmitting the broadcast frame or the ACK request frame, the ACK receiving apparatus transmits a plurality of ACK frames in a time interval in which the ACK frame is to be received or in a time interval in which the NAK frame is received after transmitting the NAK request frame. Alternatively, when an arbitrary busy signal is detected due to asynchronous overlap of a plurality of NAK frames, it is possible to determine whether the broadcast frame is retransmitted by detecting the power of the detected busy signal.

The ACK receiving apparatus transmits by designating a time for the at least one ACK transmitting apparatus to transmit an ACK frame in the MAC header of the broadcast frame or the MAC header of the ACK request frame, and transmits the ACK in the MAC header of the NAK request frame The device may transmit by specifying the time to transmit the NAK frame.

When the ACK request frame is additionally transmitted, the ACK reception apparatus may transmit by setting the same sequence number to the MAC header of the broadcast frame and the MAC header of the ACK request frame.

An ACK transmission apparatus of a wireless communication system according to another embodiment of the present invention for achieving the above object determines whether a request for an ACK frame or additional transmission of an ACK request frame is set in a received broadcast frame, and the ACK If additional transmission of the request frame is set, the ACK request frame is received, and a predetermined ACK frame requested by the broadcast frame or the ACK request frame is used at the same time as another ACK transmission device at a predetermined time using the same resource. to send

In order to achieve the above object, a method for receiving ACK in a wireless communication system according to another embodiment of the present invention includes transmitting a broadcast frame in which a request for an ACK frame or an ACK request frame requesting an ACK frame is additionally transmitted. ; and when an ACK frame transmitted using the same resource is simultaneously received from each of the at least one ACK transmission device that has received at least one of the broadcast frame and the ACK request frame, the broadcast frame is based on the power of the received ACK frame. and determining whether to retransmit.

In accordance with another embodiment of the present invention for achieving the above object, there is provided a method for transmitting an ACK in a wireless communication system, comprising: determining whether a request for an ACK frame or additional transmission of an ACK request frame is set in a received broadcast frame; receiving the ACK request frame when additional transmission of the ACK request frame is set; and transmitting a predetermined ACK frame requested by the broadcast frame or the ACK request frame at a predetermined time and at the same time as another ACK transmission method using the same resource.

Accordingly, the apparatus and method for transmitting and receiving ACK in a wireless communication system according to an embodiment of the present invention includes or additionally transmits an ACK frame request or a NAK frame request when a broadcast frame is transmitted in a wireless communication system, and an ACK frame from a plurality of terminals Alternatively, reliability of the broadcast frame may be improved by receiving the NAK frame and determining whether the broadcast frame is normally transmitted. In particular, when an ACK frame is requested, a plurality of UEs can simultaneously transmit an ACK frame using the same resource, thereby minimizing resource usage for transmitting the ACK frame. Also, it is possible to easily determine whether a broadcast frame is normally transmitted by analyzing the power of a plurality of ACK frames and NAK frames received at the same time using the same resource, and to perform additional operations such as retransmission.

1 illustrates an example of a wireless communication system environment in which vehicle terminals communicate with each other.
2 shows an example of a hierarchical structure of a terminal according to the present embodiment.
3 shows an example of broadcast transmission and ACK frame transmission/reception operations.
4 shows an example of an ACK request frame structure.
5 shows another example of an ACK frame transmission/reception operation for broadcast for checking whether transmission of the broadcast frame is successful.
6 shows an example of a structure of a NAK request frame.
7 shows another example of an ACK frame transmission/reception operation for broadcast for checking whether transmission of the broadcast frame is successful.
8 illustrates an ACK reception method in a wireless communication system according to an embodiment of the present invention.
9 shows an ACK transmission method in a wireless communication system according to an embodiment of the present invention.
10 shows an ACK transceiver of a wireless communication system according to an embodiment of the present invention.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention may be embodied in various different forms, and is not limited to the described embodiments. In addition, in order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it does not exclude other components, unless otherwise stated, meaning that other components may be further included. In addition, terms such as "...unit", "...group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. and a combination of software.

1 shows an example of a wireless communication system environment in which terminals communicate with each other.

In the wireless communication system (or wireless LAN) environment according to the present embodiment, the terminal STA may be an ACK transmission device or a reception device, and may be a vehicle terminal STA that is provided in each of a plurality of vehicles to perform mutual communication. In addition, the terminal STA may be a roadside terminal provided in a roadside device such as a street lamp or a traffic light to communicate with a vehicle terminal STA provided in a neighboring vehicle, or may be a terminal of another wireless communication device. In addition, a plurality of terminals (STA) may perform mutual communication by performing a wireless LAN operation.

In the wireless communication system environment as shown in FIG. 1 , the terminal (STA) may not perform scanning, authentication, and binding operations performed in the existing wireless LAN operation, and data without belonging to a specific basic service set (BSS). It may be an Outside the Context of BSS (OCB) environment that can transmit and receive .

1 , each of the plurality of vehicle terminals (STA) may detect a specific situation or perform a specified specific operation through various sensors provided in the vehicle. In addition, as a result of the sensed information or the operation, data including the vehicle position, speed, acceleration, and sensor measurement result may be transmitted in the form of a broadcast frame to a plurality of nearby vehicle terminals. In addition, a broadcast frame transmitted by another vehicle terminal (STA) or various other frames may be received.

On the other hand, the roadside device may transmit a map of the surrounding situation and a specific event (eg, accident and congestion information in the road direction) in the form of a broadcast frame, and each vehicle terminal (STA) receives the broadcast frame. can do.

Here, the vehicle terminal or the roadside terminal may transmit a broadcast frame for a specific event (eg, accident information and breakdown information of the corresponding vehicle) in an emergency situation. In addition, since the broadcast frame for a specific event requires high reliability that neighboring vehicle terminals (STAs) must receive, unlike a general broadcast frame, transmission success must be guaranteed. Therefore, in the present embodiment, the terminal (STA) transmitting the broadcast frame must be able to determine whether the transmitted broadcast frame is normally received by the plurality of vehicle terminals (STA), and retransmit the broadcast frame according to the determination result.

However, since the operation of the terminal (STA) receiving the broadcast frame is not defined in the existing WLAN operation, the terminal (STA) transmitting the broadcast frame cannot determine whether the broadcast frame is normally transmitted.

Accordingly, in the present embodiment, the ACK request is transmitted together with the broadcast frame transmission so that it can be determined whether the broadcast frame is normally transmitted, so that the terminal (STA) receiving the broadcast frame transmits the ACK frame. In this case, the ACK request may be transmitted together with being included in the transmitted broadcast frame, but may also be transmitted separately from the broadcast frame in the form of an ACK request frame.

Each of the plurality of terminals (STA) may transmit and receive various frames. Hereinafter, a terminal transmitting a broadcast frame is referred to as a transmitting terminal (Tx STA), and a terminal receiving the broadcast frame is referred to as a receiving terminal (Rx STA). ) is called Here, the transmitting terminal (Tx STA) may be referred to as an ACK receiving device because it receives the ACK frame for the broadcast frame transmitted thereafter, and the receiving terminal (Rx STA) may be referred to as an ACK transmitting device since it receives the ACK frame.

That is, each of the plurality of terminals (STA) may transmit or receive a broadcast frame or an ACK frame.

2 shows an example of a hierarchical structure of a terminal according to the present embodiment.

In this embodiment, the terminal (STA) may perform a communication operation in a Dedicated Short Range Communication (DSRC) method. Referring to FIG. 2 , a terminal (STA) performing DSRC communication is a transport layer that ensures transmission reliability between both ends under an application layer (not shown), which is the highest layer. UDP/TCP performing the operation of 110, IPv6 performing the operation of the network layer 120 that finds a transmission path between multiple nodes and delivers it to the corresponding path, and a data link layer for point-to-point transmission (Data Link) Layer) of the LLC (Logical Link Control) layer 131 and MAC (Medium Access Control) layer 132 and may be composed of a physical layer (Physical layer: PHY) 140 that transmits an actual signal.

However, as shown in FIG. 1 , when the terminal is a vehicle terminal provided in a vehicle to perform communication between vehicles, the transmitting terminal directly transmits the data to the receiving terminal, so the process of transmitting data to a destination through multiple terminals I don't need this. Therefore, since the roles of the transport layer and the data link layer in the existing network layer are not required, the functions of the transport layer 110 and the data link 120 layer as shown in FIG. 2 are implemented using the WAVE (Wireless Access in Vehicular Environments) Short Message Protocol (hereinafter referred to as WSMP) 150 may be replaced and simplified.

Meanwhile, for operation in each layer, corresponding data and additional information may be transmitted from an upper or lower layer through a service access point (hereinafter referred to as SAP). For example, the LLC 131 transmits data and parameters such as a source address and a destination address from the WSMP 150 or IPv6 160 to the link service access point (LSAP). ) (160). In particular, when the corresponding data is transmitted through the WSMP 150 , the channel load measured by the corresponding terminal may be transmitted through the LSAP 160 . The WAVE MAC (Medium Access Control) 132 may exchange data to be transmitted through the upper layer LLC 131 and the MAC SAP 170 and parameters for the transmission operation. When transmitting a frame, the MAC layer 132 may transmit a frame transmission request in the form of MA-UNITDATA.request, which is an SAP parameter used in an existing WLAN, from the LLC 131 through the MAC SAP 170 . Alternatively, it can be delivered in the form of MA-UNITDATAX.request in which parameters for WAVE-related operations are added to MA-UNITDATA.request. MA-UNITDATAX.request can be composed as follows.

Among the parameters included in the MA-UNITDATAX.request, Channel Identifier is set as a Channel Identifier included in a request primitive in WSM, indicates a channel to transmit WSM, and Time Slot is WAVE channel switching In connection with (channel switching), it may be set to 0 or 1 as a time slot in which the corresponding message is transmitted. Data Rate indicates the data rate used when transmitting the corresponding WSM, TxPwr_Level indicates the transmission power to be used when transmitting the WSM, and WsmExpiryTime is an optional parameter included when transmitting the WSMP. Avoid sending messages. Finally, High Reliability is a parameter indicating whether high reliability transmission is required when transmitting the WSM, and may be set to a value of 0 or 1.

As described above, High Reliability among the parameters delivered through the MAC SAP 170 indicates whether the corresponding WSM is a message requiring high reliability, and when the corresponding parameter indicates data requiring high reliability, the MAC layer 132 ) can perform high-reliability transmission.

3 shows an example of broadcast transmission and ACK frame transmission/reception operations, and FIG. 4 shows an example of an ACK request frame structure.

Referring to FIG. 3 , a transmitting terminal (Tx STA) may transmit a broadcast frame (or a multicast frame, a groupcast frame) 210 to neighboring terminals (STA). Here, the peripheral terminal (STA) may be a vehicle terminal provided in the vehicle together with the transmitting terminal (Tx STA), or may be a terminal in a pre-grouped group.

In this embodiment, the transmitting terminal (Tx STA) may transmit a frame in an Enhanced Distributed Channel Access (EDCA) method. In EDCA, a transmitting terminal (Tx STA) first checks a channel state when transmitting a frame. In this case, the channel state can be confirmed through physical detection of a signal, virtual detection through a PHY preamble, and network allocation vector (NAV) setting analysis through a Duration field in a MAC header. The transmitting terminal (Tx STA) checks the channel state for transmitting the frame during the Arbitrary Inter-frame Space (AIFS) time, and transmits the frame if the channel is empty during the AIFS time. In this case, a different access category (hereinafter referred to as AC) may be designated according to the type of frame to be transmitted, and the AIFS value may vary according to each designated AC. For example, when an AIFS number (AIFS number) is set for each AC, the AIFS may be calculated and set as (Short Inter-frame Space) + AIFSN Ⅷ (aSlotTime).

On the other hand, when the channel becomes busy during the AIFS time, or when the transmission procedure of another frame is performed immediately before the frame transmission, it is confirmed that the channel is empty during the AIFS time and then waits additionally for a random time A backoff procedure may be performed. In this case, a backoff value is set randomly among numbers between 0 and a predetermined contention window (hereinafter, CW), and a time corresponding to the set backoff value may be additionally waited. Here, CW may be set to a different value for each AC. If the channel is empty, the set backoff value decreases by 1 per aSlotTime, and when the backoff number becomes 0, frame transmission can be performed. However, if a channel becomes busy during the backoff procedure, the backoff procedure is aborted, and when the corresponding channel is empty again, the channel sensing is performed for the AIFS time, and then for the time corresponding to the remaining backoff number. The frame may be transmitted by additionally waiting.

And in the present embodiment, the transmitting terminal (Tx STA) transmits the frame to be transmitted is a broadcast frame 210 according to a predetermined event for notifying nearby vehicles of an urgent situation such as accident information or vehicle failure information. Transmission reliability may be improved by checking whether the terminal STA has normally received the broadcast frame 210 . In this embodiment, the transmitting terminal (Tx STA) may request transmission of an ACK frame from the receiving terminal (Rx STA) that has received the broadcast frame 210 in order to check whether transmission of the broadcast frame 210 is successful. .

For example, when the High Reliability parameter is set to 1 in the MA-UNITDATAX.request transmitted through the MAC SAP 170 , the transmitting terminal (Tx STA) may determine that an event requiring high reliability has occurred. Accordingly, the transmitting terminal (Tx STA) requests transmission of the ACK frame 230 to the receiving terminal (Rx STA) receiving the broadcast frame 210 while transmitting the broadcast frame 210 to the neighboring terminal (STA). can In this case, the ACK frame 230 transmission request is performed by transmitting an ACK request frame 220 separate from the broadcast frame 210, as shown in FIG. 3, or a predetermined specific information of the broadcast frame 210 It can be performed by setting and transmitting an ACK frame request in the field.

When the broadcast frame 210 and the separate ACK request frame 220 are not transmitted and the broadcast frame 210 is implicitly transmitted with the ACK frame request, the transmitting terminal (Tx STA) transmits the broadcast frame. In the MAC header of 210 , the receiving terminal (Rx STA) may transmit the ACK frame 230 including a time in the Duration field.

However, when transmitting the ACK request frame 220 separate from the broadcast frame 210 , the receiving terminal (Rx STA) that has received the broadcast frame 210 recognizes in advance that the ACK request frame 220 is additionally transmitted thereafter. should be able to Therefore, when the transmitting terminal (Tx STA) intends to transmit the ACK request frame 220 separate from the broadcast frame 210 , the More Data subfield value is added in the MAC header of the broadcast frame 210 . By setting it to 1 and transmitting, the receiving terminal (Rx STA) can recognize in advance that the ACK request frame 220 is transmitted and stably receive the ACK request frame 220 .

In addition, the transmitting terminal (Tx STA) may transmit the ACK frame 230 including a time for the receiving terminal (Rx STA) to transmit the ACK frame 230 in the persistence field 320 in the MAC header of the ACK request frame 220 .

In this case, the transmitting terminal (Tx STA) transmits the ACK request frame 220 to the neighboring terminal (STA) after a predetermined time (eg, Short Inter-frame Space: SIFS) from the transmission end time of the broadcast frame. can

In addition, in some cases, the transmitting terminal (Tx STA) includes a Duration field in the MAC header of the broadcast frame 210 , the time at which the receiving terminal (Rx STA) will receive the ACK request frame 220 and the ACK frame 230 ) may be transmitted including the time to transmit. That is, even if the transmitting terminal (Tx STA) separately transmits the ACK request frame 220 , both the time to receive the ACK request frame 220 and the time to transmit the ACK frame 230 are in the MAC header of the broadcast frame 210 . It can also be sent with

In addition, the transmitting terminal (Tx STA) transmits the broadcast frame 210 and the ACK request frame 220 so that the receiving terminal (Rx STA) can transmit the ACK frame 230 corresponding to the transmitted broadcast frame 210 MAC. A sequence number may be included in a sequence number subfield of the header and transmitted. Even if the receiving terminal (Rx STA) receives the ACK request frame 220, the transmitting terminal (Tx STA) receives the previously transmitted broadcast frame 210, and the sequence number of the received broadcast frame 210 and This is to transmit the ACK frame 230 only when the sequence numbers of the ACK request frame 220 match.

The ACK request frame 220 may be configured the same as or similar to the existing Block Ack Request (BAR) frame. 4, the ACK request frame 220 includes a frame control field 310, a persistence field 320, a Receiver Address (RA) field 330, a Transmitter Address (TA) field 340, a BAR control field ( 350 ), a BAR information field 360 and an FCS field 370 . In this case, the frame control field 310 , the persistence field 320 , and the FCS field 370 may be configured identically or similarly to the existing Block Ack Request (BAR) frame. However, in the persistence field 320 , a time for the receiving terminal (Rx STA) to transmit the ACK frame 230 may be set. All bits of the RA field 330 may be set to 1 when the current frame is the ACK request frame 220 for the broadcast frame 210 . However, when the current frame is not the ACK request frame 220 for the broadcast frame 210 but the ACK request frame for the groupcast frame for the terminal in the predetermined group, the group address may be set in the RA field 330. .

The BAR control field 350 may include a BAR ACK policy subfield 351 , a BAR type subfield 352 , a TID information subfield 354 , and the like. In this case, the response of the receiving terminal (Rx STA) The BAR ACK policy subfield 351 may be set to 0 in order to request can be In addition, the TID information subfield 354 may indicate the TID of the transmitted broadcast frame or groupcast frame.

The BAR information field 360 may indicate a fragment number subfield 361 and a start sequence number field 362 indicated by 0. At this time, if the value of the sequence number field of the transmitted broadcast frame or groupcast frame is not 0, the start sequence number field 362 contains the same value as the value of the sequence number field of the broadcast frame or groupcast frame. can

Meanwhile, the receiving terminal (Rx STA) that has received the broadcast frame 210 may check the persistence field of the received broadcast frame 210 to implicitly check whether there is a request for transmission of the ACK frame. Alternatively, the receiving terminal (Rx STA) may check whether the ACK request frame 220 is separately transmitted by checking an additional data subfield of the broadcast frame 210 .

When the transmission of the ACK frame 230 is implicitly requested by the duration field of the broadcast frame 210, the receiving terminal (Rx STA) receives a time specified in the duration field from the transmission end time of the broadcast frame 210 (or The ACK frame 230 may be transmitted after a predetermined time (eg, SIFS). At this time, the transmitted ACK frame 230 may be a block ACK (BlockACK) frame.

Since the transmitting terminal (Tx STA) transmits the broadcast frame 210 to a plurality of neighboring terminals (STAs), the plurality of receiving terminals (Rx STAs) that have received the broadcast frame 210 transmit the ACK frame 230 . can However, in this embodiment, a plurality of receiving terminals (Rx STAs) transmit an ACK frame 230 using the same resource at the time specified in the persistence field (or at a predetermined time (eg, SIFS)). can

On the other hand, when it is confirmed that the ACK request frame 220 is separately transmitted by the additional data subfield of the received broadcast frame 210, the receiving terminal (Rx STA) receives from the transmitting terminal (Tx STA). It waits until the ACK request frame 220 is transmitted. As described above, the transmitting terminal (Tx STA) may transmit the ACK request frame 220 after a predetermined time (eg, SIFS) from the transmission end time of the broadcast frame 210, and the ACK request frame The receiving terminal (Rx STA) that has received 220 may transmit the ACK frame 230 after a predetermined time (eg, SIFS) from the transmission end time of the ACK request frame 220 . However, the receiving terminal (Rx STA) may transmit the ACK frame 230 at the time set in the persistence field 320 .

At this time, when the sequence number is included in the ACK request frame 220 , the receiving terminal (Rx STA) determines whether a frame including the same sequence number has been previously received, and determines that the frame including the same sequence number has been received Only when the ACK frame 230 can be transmitted. The ACK frame 230 transmitted at this time may also be a block ACK frame similar to the ACK request frame 220 .

In addition, in this embodiment, a plurality of receiving terminals (Rx STAs) may transmit the ACK frame 230 simultaneously using the same resource in response to the broadcast frame 210 or the ACK request frame 220 . This is to minimize resource consumption for ACK frame 230 transmission.

Although a plurality of receiving terminals (Rx STAs) transmit the ACK frame 230 using the same resource, since the plurality of receiving terminals (Rx STAs) simultaneously transmit the ACK frame 230, the transmitting terminal (Tx STA) is Simultaneous-ACK (ACK) frames 230 transmitted simultaneously by a plurality of receiving terminals (Rx STAs) may be received without collision between the plurality of ACK frames 230 .

The transmitting terminal (Tx STA) requests transmission of the ACK frame 230 to the receiving terminal (Rx STA) using the broadcast frame 210 or the ACK request frame 220 , and the broadcast frame 210 or ACK It is determined whether the ACK frame 230 is detected within a predetermined time (eg, distributed coordination function inter-frame space time (DIFS)) from the time when the request frame 220 is transmitted.

When the ACK frame 230 is received, the transmitting terminal (Tx STA) detects the power of the received ACK frame 230, and when the detected power of the ACK frame 230 is greater than or equal to a predetermined reference power, a broadcast frame ( 210) is determined to have been transmitted normally. However, if the ACK frame 230 is not received or the detected power of the ACK frame 230 is less than the reference power, it is determined that the broadcast frame 210 is not normally transmitted. That is, it is determined that the neighboring terminal (STA) has not received the broadcast frame 210 .

As described above, in this embodiment, a plurality of receiving terminals (Rx STAs) simultaneously transmit the same ACK frame 230 using the same resource. Therefore, when only the reception of the ACK frame 230 is detected, even if only one receiving terminal (Rx STA) receives the broadcast frame 210 and transmits the ACK frame 230 , the transmitting terminal (Tx STA) broadcasts the broadcast. It is determined that the frame 210 is normally transmitted. However, this is not a case in which the broadcast frame 210 to be propagated to a plurality of terminals (STAs) is normally transmitted. Therefore, in the present embodiment, the transmitting terminal (Tx STA) in order to determine whether a plurality of terminals (STA) has received the broadcast frame 210 from the ACK frame 230 transmitted using the same resource at the same time, the ACK frame 230 ) and determines whether the broadcast frame 210 is normally transmitted based on the sensed power.

Even when determining whether the broadcast frame 210 is normally transmitted based on the power of the ACK frame 230 , the number of receiving terminals (Rx STAs) that have received the broadcast frame 210 cannot be accurately determined. Nevertheless, since the approximate number of receiving terminals (Rx STAs) that have received the broadcast frame 210 can be estimated from the power of the ACK frame 230 , it can be sufficiently determined whether the broadcast frame 210 is normally transmitted. there is.

When the power of the ACK frame 230 is equal to or greater than the reference power, the transmitting terminal (Tx STA) determines that the broadcast frame 210 has been normally transmitted and does not retransmit the broadcast frame 210 .

However, when the ACK frame 230 is not received or the power of the ACK frame 230 is less than the reference power, the transmitting terminal (Tx STA) determines that transmission of the broadcast frame 210 has failed. In addition, if it is determined that transmission of the broadcast frame 210 has failed, a retransmission operation of the broadcast frame 210 may be performed. In this case, the CW for setting the backoff value for the retransmission broadcast frame 210 may be set to CWⅧ2-1 based on the CW for the previous broadcast frame 210 .

In the above description, it has been described that the transmitting terminal (Tx STA) determines whether the broadcast frame 210 is normally transmitted based on the received power of the ACK frame 230 . However, in an actual wireless communication environment, particularly, in a wireless LAN environment between vehicle terminals, as shown in FIG. 1 , due to various factors such as vehicle movement, even if a plurality of receiving terminals (Rx STAs) transmit the ACK frame 230 at the same time, the transmitting terminal In the (Tx STA), a plurality of ACK frames 230 may be received with a time difference. In this case, it is difficult for the transmitting terminal (Tx STA) to detect the ACK frame 230, so that it may be determined that an arbitrary busy signal is received through the channel. However, in the present invention, since the transmitting terminal (Tx STA) senses the power of the ACK frame 230 only to determine whether the broadcast frame 210 is normally transmitted, there is no need to restore the received ACK frame 230 . . Therefore, the transmitting terminal (Tx STA) detects the power of the busy signal even if a plurality of ACK frames 230 have a time difference and are received in the form of an arbitrary busy signal, and the broadcast frame 210 is transmitted. It can be determined whether transmission is normal.

As a result, in the ACK frame transmission/reception operation according to FIG. 3 , the transmitting terminal (Tx STA) transmits the broadcast frame 210 including the ACK request, or transmits the ACK request frame 220 separately from the broadcast frame 210. , so that a plurality of receiving terminals (Rx STAs) that have received the broadcast frame 210 simultaneously transmit an ACK frame 230 using the same resource, and an ACK frame 230 transmitted from a plurality of receiving terminals (Rx STAs) ), it is possible to easily determine whether the broadcast frame 210 is normally transmitted or not. In addition, transmission reliability can be greatly improved by retransmitting the broadcast frame 210 according to the determination result.

FIG. 5 shows another example of an ACK frame transmission/reception operation for broadcast for checking whether transmission of a broadcast frame is successful, and FIG. 6 shows an example of a structure of a NAK request frame.

In FIG. 5 , the transmitting terminal (Tx STA) transmits an ACK request frame 420 separately from the broadcast frame 410 similar to that in FIG. 3 . However, in FIG. 5 , the transmitting terminal (Tx STA) may additionally request not only the ACK request frame 420 but also the NAK request frame 440 for checking whether the broadcast frame 410 has not been received.

Also in FIG. 5 , the transmitting terminal (Tx STA) may transmit the duration field 320 of the broadcast frame 410 including the time for the receiving terminal (Rx STA) to transmit the ACK frame 230, and the broadcast frame 410 ) by setting the value of the More Data subfield to a predetermined value, the receiving terminal (Rx STA) can be notified that at least one of the ACK request frame 420 or the NAK request frame 440 is transmitted. there is.

According to the setting of the broadcast frame 410, the transmitting terminal (Tx STA) may transmit the ACK request frame 420 after a predetermined time (eg, SIFS) from the transmission end time of the broadcast frame 410. . And as shown in (a), when the transmitting terminal (Tx STA) receives the ACK frame 430 from the receiving terminal (Rx STA), a predetermined time (eg, SIFS), the NAK request frame 440 may be additionally transmitted.

At this time, the transmitting terminal (Tx STA) detects the power of the received ACK frame 430 to determine whether the power of the ACK frame 430 is greater than or equal to a predetermined reference power, and if it is greater than or equal to the reference power, the NAK request frame 440 is additionally added can be transmitted And even if the transmitting terminal (Tx STA) does not receive the NAK frame 450 from the receiving terminal (Rx STA) or the NAK frame 450 is received, the power of the ACK frame 430 and the power of the received NAK frame 450 . If the ratio is less than the predetermined reference power ratio, the transmitting terminal (Tx STA) may determine that the broadcast frame 410 is not normally transmitted and retransmit the broadcast frame 410 .

On the other hand, the transmitting terminal (Tx STA) If the power ratio of the ACK frame 430 and the NAK frame 450 is equal to or greater than the reference power ratio, it is determined that the broadcast frame 410 has been transmitted normally, and the broadcast frame 410 may not be retransmitted.

However, in some cases, the transmitting terminal (Tx STA) has a time difference between the plurality of ACK frames 430 transmitted from the plurality of receiving terminals (Rx STA), as shown in (b), and in the form of an arbitrary busy signal. If the transmitted and sensed power of the busy signal is equal to or greater than the reference power, the NAK request frame 440 can be additionally transmitted after a predetermined time (eg, SIFS) from the end of the transmission of the busy signal. there is.

In addition, the transmitting terminal (Tx STA) may transmit the broadcast frame 410 , the ACK request frame 420 , and the NAK request frame 440 by including the sequence number in the sequence number subfield of the MAC header.

Since the structure of the ACK request frame 420 has already been described with reference to FIG. 4 , it will not be described herein. In addition, the NAK request frame 440 may be configured the same as or similarly to the existing Block Ack Request (BAR) frame like the ACK request frame 420 . Referring to FIG. 6 , the NAK request frame 440 may have substantially the same configuration as the ACK request frame 420 . Also in the NAK request frame 440 , a time for the receiving terminal (Rx STA) to transmit the ACK frame 230 may be set in the persistence field 320 . However, in the NAK request frame 440 , the TA field 340 included in the ACK request frame 420 may be omitted. In addition, the BAR type subfield 352 in the BAR control field 350 may be set to 5 when the receiving terminals (Rx STAs) request to simultaneously transmit the NAK frame 450 .

When it is confirmed that the receiving terminal (Rx STA) that has normally received the broadcast frame 410 transmits the ACK request frame 420 separately by the More Data subfield of the received broadcast frame 410 , , waits until the ACK request frame 420 is transmitted from the transmitting terminal (Tx STA).

When the ACK request frame 420 is transmitted after a predetermined time (eg, SIFS) from the transmission terminal (Tx STA) of the transmission end time of the broadcast frame 410, the broadcast frame 410 and the ACK request The receiving terminal (Rx STA) that has received the frame 420 transmits the ACK frame 430 to the transmitting terminal (Tx STA) after a predetermined time (eg, SIFS) from the transmission end time of the ACK request frame 420 . send

When the NAK request frame 440 is received, the terminal (STA) that has not normally received the broadcast frame 410 receives the NAK after a predetermined time (eg, SIFS) from the transmission end time of the NAK request frame 440 . The frame 450 is transmitted to a transmitting terminal (Tx STA).

Here, the terminal STA receiving the ACK request frame 420 or the NAK request frame 440 transfers a frame including the same sequence number as the sequence number included in the ACK request frame 420 or the NAK request frame 440 . It is determined whether a frame has been received, and when it is determined that a frame including the same sequence number has not been received, the NAK frame 450 may be transmitted.

Here, each terminal (STA) receiving the ACK request frame 420 may transmit the ACK frame 430 with the same resource at the same time. In addition, each terminal (STA) receiving the NAK request frame 440 may transmit the NAK frame 450 with the same resource at the same time.

The transmitting terminal (Tx STA) determines whether the ACK frame 430 and the NAK frame 450 are detected. When the ACK frame 430 is detected and the NAK frame 450 is not detected, the transmitting terminal (Tx STA) may determine that the broadcast frame 410 is normally transmitted.

However, when the ACK frame 430 and the NAK frame 450 are detected, the transmitting terminal (Tx STA) detects the power of each of the detected ACK frame 430 and the NAK frame 450 . Here, the ACK frame 430 is a frame transmitted by the receiving terminal (Rx STA) that has received the broadcast frame 410 , whereas the NAK frame 450 is a frame transmitted by the terminal (STA) that has not received the broadcast frame 410 . This is the transmitted frame. Accordingly, the transmitting terminal (Tx STA) may determine the transmission success rate of the broadcast frame 410 by comparing the detected power of the ACK frame 430 with the power of the NAK frame 450 . When the ratio between the power of the ACK frame 430 and the power of the NAK frame 450 is equal to or greater than a predetermined reference power ratio, the transmitting terminal (Tx STA) determines that the broadcast frame 410 is normally transmitted. However, if it is less than the reference power ratio, it is determined that the broadcast frame 410 is not normally transmitted, and the broadcast frame 410 may be retransmitted.

In addition, even if a plurality of terminals (STA) transmit the ACK frame 430 or the NAK frame 450 at the same time, each of the ACK frame 430 and the NAK frame 450 is, as shown in (b), the transmitting terminal (Tx) STA) may be received in the form of an arbitrary busy signal with a time difference.

Accordingly, the transmitting terminal (Tx STA) detects the ACK frame 430 and the NAK frame 450 after transmission of the ACK request frame 420 even when the ACK frame 430 and the NAK frame 450 are not accurately detected and are detected in the form of a busy signal. Whether to retransmit the broadcast frame 410 may be determined based on a ratio of the power of the busy signal and the power of the busy signal detected after transmission of the NAK request frame 440 .

Here too, the CW for setting the backoff value for the retransmitted broadcast frame 410 may be set to CWⅧ2-1 based on the CW for the previous broadcast frame 410 .

7 shows another example of an ACK frame transmission/reception operation for broadcast for checking whether transmission of the broadcast frame is successful.

Also in FIG. 7 , the transmitting terminal (Tx STA) transmits a broadcast frame 610 . However, as shown in (a) of FIG. 7 , the transmitting terminal (Tx STA) does not transmit the ACK request frames 220 and 432 or the NAK request frame 440 . In addition, the receiving terminal (Rx STA) that has received the broadcast frame 610 does not transmit the separately configured ACK frames 230 and 430 or the NAK frame 450, unlike in FIGS. 3 to 6, but the received broadcast frame. 610 is copied and transmitted. That is, the received broadcast frame 610 may be transmitted as an ACK frame.

To this end, the transmitting terminal (Tx STA) sets a period until the end of the operation of copying and transmitting the broadcast frame 610 in the persistence field 320 of the MAC header of the broadcast frame 610, or Copy and retransmission of the broadcast frame 610 may be indicated through the type subfield of the frame control field 310 . For example, the transmitting terminal (Tx STA) may set the type subfield of the frame control field 310 in the MAC header to 0101 to request to instruct copy and retransmission of the broadcast frame 610 .

Accordingly, the receiving terminal (Rx STA) that has received the broadcast frame 610 may confirm that copying and retransmission of the received broadcast frame 610 is requested from the MAC header of the broadcast frame 610 . In addition, the receiving terminal (Rx STA) may transmit the received broadcast frame 610 simultaneously using the same resource after a predetermined time (eg, SIFS) from the transmission end time of the broadcast frame 610 . In addition, the terminal (STA) that did not receive the broadcast frame 610 transmitted from the transmitting terminal (Tx STA) also receives a broadcast frame 610 by the broadcast frame 610 retransmitted from the receiving terminal (Rx STA). are given the opportunity to receive However, in order to prevent the transmission of the broadcast frame 610 by a plurality of terminals (STA) from being repeatedly generated in a chain, the receiving terminal (Rx STA) partially modifies the MAC header of the received broadcast frame 610 . can be retransmitted.

The transmitting terminal (Tx STA) may determine whether the broadcast frame 610 is normally transmitted based on the power of the broadcast frame 610 retransmitted from the receiving terminal (Rx STA).

However, as shown in (b), if the retransmitted broadcast frame 610 is not received from the receiving terminal (Rx STA), the transmitting terminal (Tx STA) determines that the broadcast frame 610 is not normally transmitted. Thus, the broadcast frame 610 may be retransmitted.

8 shows an ACK reception method in a wireless communication system according to an embodiment of the present invention.

Referring to FIGS. 2 to 7 , the ACK reception method of the wireless communication system of FIG. 8 will be described. The transmitting terminal (Tx STA), that is, the ACK receiving apparatus determines whether a broadcast frame to be transmitted exists (S11). And if it is determined that there is a broadcast frame to be transmitted, the broadcast frame is transmitted (S12). At this time, the ACK receiving device determines whether the broadcast frame to be transmitted is a broadcast frame for a specific event requiring high reliability according to the High Reliability parameter value of MA-UNITDATAX.request delivered through the MAC SAP 170 in advance. can be discerned.

When it is determined that the broadcast frame to be transmitted is a high-reliability broadcast frame, the ACK reception device may transmit by including the ACK request in the MAC header of the transmitted broadcast frame, or may notify that it will additionally transmit the ACK request frame. When the ACK reception device includes the ACK request in the MAC header of the broadcast frame and transmits the ACK request, the MAC header may transmit the ACK frame by including a time for the transmission device to transmit the ACK frame in the persistence field. However, when the ACK request frame is additionally transmitted, the additional data subfield value in the MAC header of the broadcast frame may be set to a predetermined value and transmitted.

Accordingly, the ACK receiving apparatus determines whether transmission of the ACK request frame is necessary by setting the ACK request frame to be additionally transmitted using the MAC header of the broadcast frame and checking whether the broadcast frame is transmitted (S13).

When it is determined that transmission of the ACK request frame is necessary, the ACK receiving apparatus transmits the ACK request frame (S14). The ACK receiving apparatus may transmit the ACK request frame after a predetermined time (eg, SIFS) from the time when the transmission of the broadcast frame is terminated. In this case, the ACK receiving device is a broadcast frame and an ACK request frame so that the receiving terminal (Rx STA) receiving the broadcast frame, that is, the ACK transmitting device, can identify whether the ACK request frame is an ACK request frame for a specific broadcast frame. The same sequence number may be included in the sequence number subfield of the MAC header and transmitted.

Then, the ACK receiving device simultaneously receives the ACK frame transmitted through the same resource from the ACK transmitting device that has received the broadcast frame (S15). Here, the ACK frame may receive the ACK frame transmitted simultaneously after a predetermined time (eg, SIFS) from the time when the broadcast frame or the ACK request frame is transmitted. If the time to transmit the ACK frame is designated in the broadcast frame or the ACK request frame, the ACK frame transmitted at the designated time is received. The ACK receiving apparatus detects the power of the received ACK frame (S16). Then, the ACK receiving apparatus determines whether the power of the detected ACK frame is equal to or greater than a predetermined reference power (S17). If the power of the ACK frame is less than the reference power, it is determined that the broadcast frame is not normally transmitted, and the broadcast frame is retransmitted (S24).

On the other hand, if the power of the ACK frame is equal to or greater than the reference power, the ACK receiving apparatus determines whether to additionally transmit the NAK request frame (S18). Whether to request an additional NAK request frame may be specified in advance in the ACK receiving apparatus. If it is determined that there is no need to additionally transmit the NAK request frame, it is determined that the broadcast frame has been transmitted normally, and the broadcast frame is not retransmitted (S19).

And, if it is determined that the ACK reception device needs to additionally transmit the NAK request frame, it transmits the NAK request frame (S20). In this case, the ACK receiving apparatus may transmit the NAK request frame after a predetermined time (eg, SIFS) from the time when the ACK frame is transmitted from the ACK transmitting apparatus. Then, the ACK reception device determines whether a NAK frame transmitted through the same resource is simultaneously received from the ACK transmission device that has not received the broadcast frame (S21). In this case, the NAK frame may receive the simultaneously transmitted NAK frame after a predetermined time (eg, SIFS) from the time when the transmission of the NAK request frame is terminated. If the time to transmit the NAK frame is specified in the NAK request frame, the NAK frame transmitted at the specified time may be received.

If the NAK frame is not received, the ACK receiving apparatus determines that the broadcast frame is normally transmitted and does not retransmit the broadcast frame (S19). However, if it is determined that the NAK frame has been received, the ACK receiving apparatus detects the power of the received NAK frame (S22). Then, it is determined whether the power ratio of the ACK frame and the NAK frame is equal to or greater than a predetermined reference power ratio. If the power ratio of the ACK frame and the NAK frame is equal to or greater than the reference power ratio, the ACK receiving apparatus determines that the broadcast frame is normally transmitted and does not retransmit the broadcast frame (S19). However, if the power ratio of the ACK frame and the NAK frame is less than the reference power ratio, it is determined that the broadcast frame is not normally transmitted, and the ACK receiving apparatus retransmits the broadcast frame (S24).

In the above description, it has been described that the ACK receiving apparatus receives the simultaneously transmitted ACK frame or the simultaneously transmitted NAK frame. However, the ACK frame or the NAK frame is not normally received due to an unavoidably generated time difference, and an arbitrary busy signal form can also be received, and in this case, it is possible to determine whether the broadcast frame is normally transmitted by detecting the power of a busy signal.

9 shows an ACK transmission method in a wireless communication system according to an embodiment of the present invention.

Referring to FIGS. 2 to 7 , the ACK transmission method of the wireless communication system of FIG. 9 will be described. The receiving terminal (Rx STA), that is, the ACK transmitting apparatus determines whether a broadcast frame is received ( S31 ). And when the broadcast frame is received, the MAC header of the broadcast frame is analyzed to determine whether to wait for the ACK request frame (S32). If it is set to additionally transmit the ACK request frame in the MAC header of the analyzed broadcast frame, the ACK transmitter receives the ACK request frame transmitted from the ACK receiver (S33).

In addition, when an ACK frame request is included in the MAC header of the broadcast frame or an ACK request frame is received, the broadcast frame or the ACK request frame is transmitted from the time the broadcast frame or the ACK request frame is completed according to the MAC header setting of the received broadcast frame. An ACK frame is transmitted at a specified time (eg, SIFS) (S34). In this case, the ACK frame may be simultaneously transmitted from a plurality of ACK transmission devices on the same resource, and when the time to transmit the ACK frame is specified in the broadcast frame or the ACK request frame, the ACK frame may be transmitted at the specified time.

Also, when the received broadcast frame and the ACK request frame include a sequence number, the ACK transmission apparatus may transmit the ACK frame only when the sequence number included in the broadcast frame and the ACK request frame is the same.

On the other hand, the ACK transmission apparatus determines whether to wait for reception of the NAK request frame (S35). Here, the ACK transmission apparatus may analyze the MAC of the broadcast frame or the ACK request frame to determine whether to wait for reception of the NAK request frame.

If it is determined that the NAK request frame is waiting to be received, the NAK request frame transmitted from the ACK receiving apparatus is received (S36). In response to the received NAK request frame, the NAK frame is transmitted at a predetermined time (eg, SIFS) from the time when the transmission of the NAK request frame is terminated ( S37 ). In this case, the NAK frame may also be transmitted simultaneously on the same resource by a plurality of ACK transmission devices, and when the time to transmit the NAK frame is specified in the NAK request frame, the NAK frame may be transmitted at the specified time.

10 shows an ACK transceiver of a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 10 , the ACK transmission apparatus or the ACK reception apparatus according to the present embodiment may include a processor 710 , a memory 720 , and a communication unit 730 . The processor 710 may execute functions, operations, and methods performed by the above-described ACK transmitting apparatus or ACK receiving apparatus. For example, the processor 710 of the ACK reception device may generate a broadcast frame, an ACK request frame, and a NAK request frame, which require high reliability, and transmit it through the communication unit 730 , and the ACK frame and the NAK frame through the communication unit 730 . By receiving the frame, it is possible to determine whether to retransmit the broadcast frame. In addition, the processor 710 of the ACK transmission apparatus analyzes the broadcast frame, the ACK request frame, and the NAK request frame received through the communication unit 730, and generates an ACK frame and a NAK frame, and transmits the generated ACK frame and the NAK frame. It may be transmitted through the communication unit 730 .

The memory 720 stores various data required for a function or operation to be executed by the processor 710 . In addition, the communication unit 730 transmits a frame transmitted from the processor 710 to another ACK receiving apparatus or an ACK transmitting apparatus, or transmits a frame transmitted from an ACK receiving apparatus or another ACK transmitting apparatus to the processor 710 . In this case, the communication unit 730 may detect the power of a frame or a busy signal transmitted from the ACK reception device or another ACK transmission device and transmit it to the processor 710 .

In the above description, the ACK receiving device and the ACK transmitting device are separately described. However, the ACK receiving device and the ACK transmitting device are short-term functionally divided into a device for receiving an ACK frame and a device for transmitting an ACK frame. It may be an ACK transmission/reception device 700 that operates as or operates as an ACK transmission device.

The method according to the present invention may be implemented as a computer program stored in a medium for execution by a computer. Here, the computer-readable medium may be any available medium that can be accessed by a computer, and may include all computer storage media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, and read dedicated memory), RAM (Random Access Memory), CD (Compact Disk)-ROM, DVD (Digital Video Disk)-ROM, magnetic tape, floppy disk, optical data storage, and the like.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is only exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

Claims (20)

A wireless communication system comprising:
Transmits a broadcast frame in which a request for an ACK frame or an ACK request frame requesting an ACK frame is additionally transmitted;
When an ACK frame transmitted using the same resource is simultaneously received from each of the at least one ACK transmission device that has received at least one of the broadcast frame and the ACK request frame,
An ACK receiving apparatus for determining whether to retransmit the broadcast frame based on the power of the received ACK frame. The method of claim 1, wherein the ACK receiving device
transmitting the broadcast frame by setting at least one of a request for the ACK frame or additional transmission of the ACK request frame in a MAC header of the broadcast frame;
If it is set to additionally transmit the ACK request frame in the MAC header of the broadcast frame, the ACK receiving apparatus transmits the ACK request frame after a predetermined time from the transmission end time of the broadcast frame. The method of claim 2, wherein the ACK receiving device
Set whether to additionally transmit a NAK request frame in the MAC header of the broadcast frame or the MAC header of the ACK request frame and transmit;
When a NAK frame transmitted using the same resource is simultaneously received from each of the at least one ACK transmission device that has received the NAK request frame,
An ACK receiving apparatus for determining whether to retransmit the broadcast frame based on a power ratio of the received NAK frame to the power of the ACK frame. The method of claim 3, wherein the ACK receiving device
After transmitting the broadcast frame or the ACK request frame, a plurality of ACK frames or a plurality of NAK frames in a time interval in which the ACK frame is received or in a time interval in which the NAK frame is received after transmitting the NAK request frame When an arbitrary busy signal is detected due to asynchronous overlap of The method of claim 3, wherein the ACK receiving device
In the MAC header of the broadcast frame or the MAC header of the ACK request frame, the at least one ACK transmitter designates a time to transmit an ACK frame and transmits, and the ACK transmitter sends a NAK frame in the MAC header of the NAK request frame ACK receiving device that transmits by specifying the time to transmit. The method of claim 2, wherein the ACK receiving device
When the ACK request frame is additionally transmitted, the ACK receiving apparatus transmits by setting the same sequence number in the MAC header of the broadcast frame and the MAC header of the ACK request frame. A wireless communication system comprising:
It is determined whether a request for an ACK frame or additional transmission of an ACK request frame is set in the received broadcast frame,
If additional transmission of the ACK request frame is set, the ACK request frame is received,
An ACK transmission apparatus for transmitting a predetermined ACK frame requested by the broadcast frame or the ACK request frame at a predetermined time and simultaneously with another ACK transmission apparatus using the same resource. The method of claim 7, wherein the ACK transmission device
If the request for the ACK frame is set in the MAC header of the broadcast frame, the ACK frame is transmitted at a predetermined time after the transmission of the broadcast frame is terminated;
When the additional transmission of the ACK request frame is set in the MAC header of the broadcast frame, the ACK transmission apparatus transmits the ACK frame at a predetermined time after the transmission of the ACK request frame is terminated. The method of claim 8, wherein the ACK transmission device
An ACK transmitting apparatus for transmitting the ACK frame by comparing the MAC header of the broadcast frame with a sequence number set in the MAC header of the ACK request frame, and transmitting the ACK frame when the sequence numbers are the same. The method of claim 8, wherein the ACK transmission device
If additional transmission of the NAK request frame is set in the MAC header of the ACK request frame, the NAK request frame is received,
If the broadcast frame is not received before the NAK request frame is received, an ACK transmission apparatus for transmitting a predetermined NAK frame at a predetermined time and at the same time as another ACK transmission apparatus using the same resource. In the ACK receiving method of the ACK receiving apparatus of a wireless communication system,
transmitting a broadcast frame in which a request for an ACK frame or an ACK request frame for requesting an ACK frame is additionally transmitted; and
When an ACK frame transmitted using the same resource is simultaneously received from each of the at least one ACK transmission device that has received at least one of the broadcast frame or the ACK request frame, the broadcast frame is transmitted based on the power of the received ACK frame. ACK reception method comprising the step of determining whether to retransmit. 12. The method of claim 11, wherein transmitting the broadcast frame comprises:
setting and transmitting at least one of a request for the ACK frame and whether to additionally transmit the ACK request frame in a MAC header of the broadcast frame; and
and transmitting the ACK request frame after a predetermined time from a transmission end time of the broadcast frame when it is set to additionally transmit the ACK request frame in the MAC header of the broadcast frame. The method of claim 12, wherein the ACK reception method
transmitting by setting whether to additionally transmit a NAK request frame in the MAC header of the broadcast frame or the MAC header of the ACK request frame; and
When a NAK frame transmitted using the same resource is simultaneously received from each of the at least one ACK transmission device that has received the NAK request frame, it is determined whether the broadcast frame is retransmitted or not, the power of the ACK frame and the power ratio of the received NAK frame ACK reception method further comprising the step of determining based on the. The method of claim 13, wherein the determining based on the power ratio comprises:
After transmitting the broadcast frame or the ACK request frame, a plurality of ACK frames or a plurality of NAK frames in a time interval in which the ACK frame is received or in a time interval in which the NAK frame is received after transmitting the NAK request frame When an arbitrary busy signal is detected due to asynchronous overlap of 14. The method of claim 13, wherein transmitting the broadcast frame comprises:
The at least one ACK transmitter designates a time to transmit an ACK frame and transmits it in the MAC header of the broadcast frame or the MAC header of the ACK request frame;
The step of transmitting by setting whether to additionally transmit the NAK request frame is
An ACK receiving method in which the at least one ACK transmitting device designates a time to transmit the NAK frame in a MAC header of the NAK request frame and transmits the specified time. 13. The ACK of claim 12, wherein the transmitting of the broadcast frame comprises setting the same sequence number in the MAC header of the broadcast frame and the MAC header of the ACK request frame when the ACK request frame is additionally transmitted. How to receive. In the ACK transmission method of the ACK transmission apparatus of a wireless communication system,
determining whether a request for an ACK frame or additional transmission of an ACK request frame is set in the received broadcast frame;
receiving the ACK request frame when additional transmission of the ACK request frame is set; and
and transmitting a predetermined ACK frame requested by the broadcast frame or the ACK request frame at a predetermined time and at the same time as another ACK transmission method using the same resource. The method of claim 17, wherein the transmitting using the same resource at the same time comprises:
comparing the MAC header of the broadcast frame with a sequence number set in the MAC header of the ACK request frame; and
and transmitting the ACK frame when the sequence number set in the MAC header of the broadcast frame and the MAC header of the ACK request frame is the same. 18. The method of claim 17, wherein transmitting the ACK frame comprises:
transmitting the ACK frame at a predetermined time after transmission of the broadcast frame is terminated when the request for the ACK frame is set in the MAC header of the broadcast frame; and
and transmitting the ACK frame at a predetermined time after transmission of the ACK request frame is terminated when the additional transmission of the ACK request frame is set in the MAC header of the broadcast frame. The method of claim 19, wherein the ACK transmission method
determining whether additional transmission of a NAK request frame is set in a MAC header of the ACK request frame;
receiving the NAK request frame if additional transmission of the NAK request frame is set; and
If the broadcast frame is not received before the NAK request frame is received, transmitting a predetermined NAK frame at a predetermined time and at the same time as another ACK transmission method using the same resource.

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