KR20100011141A - A method of transmmiting data in a very high throughput wireless lan system and a station of supporting the method - Google Patents

Abstract

PURPOSE: A method of transmitting data in a very high throughput wireless LAN system and a station supporting the method are provided to prevent collocation Interference in an adjacent sub channel. CONSTITUTION: A VHT station(STA 2) transmits a channel allocation request frame through an unoccupied sub channel among sub channels(S110). If the use of a main sub channel is completed, stations try to occupy the main sub channel(S120). STA 1 transmits an RTS(Request to Send) frame to an AP through a main sub channel(S130). The AP transmits a CTS(Clear to Send) frame to the STA 1 through the main sub channel(S140). The STA 1 transmits a data frame to the AP through the main sub channel(S150).

Description

TECHNICAL DATA TRANSFER METHOD IN A WHTH WLAN System AND A STATION SUPPORTING THEREOF {A METHOD OF TRANSMMITING DATA IN A VERY HIGH THROUGHPUT WIRELESS LAN SYSTEM AND A Station

The present invention relates to a wireless local access network (WLAN), and more particularly, to a data transmission method and a station supporting the same in a VHT (Very High Throughput) WLAN system.

Recently, with the development of information and communication technology, various wireless communication technologies have been developed. Wireless LAN (WLAN) is based on radio frequency technology, using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc. It is a technology that allows wireless access to the Internet in a specific service area.

Since the Institute of Electrical and Electronics Engineers (IEEE) 802, the standardization body for WLAN technology, was established in February 1980, a number of standardization tasks have been performed. Early WLAN technology used 2.4 GHz frequency through IEEE 802.11 to support speeds of 1 to 2 Mbps for frequency hopping, spread spectrum, infrared communication, etc. Can support speed. In addition, IEEE 802.11 improves Quality of Service (QoS), access point protocol compatibility, security enhancement, radio resource measurement, and wireless access vehicular environment. Standards of various technologies such as, fast roaming, mesh network, interworking with external network, and wireless network management are being put into practice.

Among IEEE 802.11, IEEE 802.11b supports communication speeds up to 11Mbps while using frequencies in the 2.4GHz band. IEEE 802.11a, which was commercialized after IEEE 802.11b, reduces the influence of interference compared to the frequency of the congested 2.4 GHz band by using the frequency of the 5 GHz band instead of the 2.4 GHz band, and maximizes the communication speed by using OFDM technology. Up to 54Mbps. However, IEEE 802.11a has a shorter communication distance than IEEE 802.11b. IEEE 802.11g, like IEEE 802.11b, uses a frequency of 2.4 GHz to achieve a communication speed of up to 54 Mbps and satisfies backward compatibility, which has received considerable attention. It is superior to

In addition, IEEE 802.11n is a relatively recent technical standard established to overcome limitations on communication speed and throughput, which has been pointed out as a weak point in WLAN. IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT) with data throughput of up to 540 Mbps in the 5 GHz frequency band, and also multiplexes on both sides of the transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Output (MIMO) technology using antennas. In addition, the standard not only uses a coding scheme for transmitting multiple duplicate copies to increase data reliability, but may also use orthogonal frequency division multiplex (OFDM) to increase the speed.

Background of the Invention As the spread of WLAN and applications diversifying using it have recently emerged, there is a need for a new WLAN system to support higher throughput than the data throughput supported by IEEE 802.11n. However, the IEEE 802.11n Medium Access Control (MAC) / Physical Layer (PHY) protocol is not effective in providing throughput of 1 Gbps or more. Because the IEEE 802.11n MAC / PHY protocol is for operation of a single STA, that is, one STA having a network interface card (NIC), the frame is maintained while maintaining the MAC / PHY protocol of the existing IEEE 802.11n. This is because, as the throughput increases, the overhead that occurs additionally increases. As a result, there is a limit to improving the throughput of a wireless communication network while maintaining the existing IEEE 802.11n MAC / PHY protocol, that is, a single STA architecture.

Therefore, in order to achieve a data processing speed of 1Gbps or more in a wireless communication network, a new system different from the IEEE 802.11n MAC / PHY protocol, which is a single STA architecture, is required. Very High Throughput (VHT) system is the next version of the IEEE 802.11n wireless LAN system, a recently proposed IEEE 802.11 wireless to support data processing speed of 1Gbps or more in the MAC Service Access Point (SAP) One of the LAN systems. The name of the VHT WLAN system is arbitrary. In order to provide throughput of 1 Gbps or more, a feasibility test for the VHT WLAN system using 4 × 4 MIMO and 80 MHz channel bandwidth is currently being conducted.

As described above, the IEEE 802.11a standard uses a channel bandwidth of 20 MHz in the 5 GHz band, and the IEEE 802.11n standard extends the use bandwidth to 40 MHz by binding up to two 20 MHz channels in the 5 GHz band. In such a situation, in the newly proposed VHT WLAN system, the use bandwidth is extended up to 80 MHz by combining three or more 20 MHz channels in the 5 GHz band, for example, up to four. For example, a plurality of (eg, four) subchannels of 20 MHz adjacent to each other are bundled to use a bonding channel of 80 MHz. According to this, it is possible to efficiently manage the plurality of subchannels that are connected to each other, and there is an advantage in that the variation of characteristics according to the subchannels is small.

However, when a station STA simultaneously receives frames in downlink and transmits frames in uplink using subchannels adjacent to each other, collocation interference may occur.

1 is a diagram illustrating an example of juxtaposition interference.

Referring to FIG. 1, the STA transmits an uplink frame to the AP through subchannel 2 while receiving a downlink frame through subchannel 1 from an access point (AP). Accordingly, since the downlink frame received through subchannel 1 is interfered with by the uplink frame transmitted through subchannel 2, the frame reception may fail.

As shown in FIG. 1, due to parallel interference, one AP may operate an independent WLAN protocol using a plurality of adjacent subchannels.

In order to solve the problem of co-existence interference, in IEEE 802.11n system, two subchannels are divided into a primary subchannel (PCH) and a secondary subchannel (Secondary Channel (SCH)), and all stations connected to the AP Data frames cannot be transmitted using only sub-channels. That is, the AP and all stations connected to the AP may transmit only a 20 MHz frame using only the primary subchannel and a 40 MHz frame using both the primary and secondary subchannels. Accordingly, it is possible to prevent the problem of juxtaposition interference which may occur by transmitting or receiving data frames independently using the primary subchannel and the sub subchannel adjacent to each other.

The channel operating method of the IEEE 802.11n system can be applied to the channel operating method of the IEEE 802.11 VHT WLAN system. In this case, in the IEEE 802.11 VHT WLAN system, a maximum of four 20 MHz subchannels are combined to use an 80 MHz combined channel. Can be.

FIG. 2 illustrates an example of frame transmission when a 20 MHz frame wins in contention for occupying a primary subchannel in an IEEE 802.11 VHT WLAN system. FIG. 3 illustrates an example of frame transmission when an 80 MHz frame wins. It is shown.

Referring to FIG. 2, a 20 MHz frame is transmitted using only a primary subchannel. Referring to FIG. 3, an 80 MHz frame is transmitted using a primary subchannel and all three sub-channels. Although not shown in the drawing, when a 40 MHz frame wins a contention, a frame is transmitted using a primary subchannel and one secondary subchannel, and when a 60 MHz frame wins, a primary subchannel and two secondary subchannels are used. Frame is transmitted. Therefore, in either case, the primary subchannel is necessarily used for frame transmission, and the frame cannot be transmitted using only the subchannel.

As described above, according to the channel operating method of the IEEE 802.11n system and the IEEE 802.11 VHT WLAN system, it is possible to prevent the parallel problem in advance. However, according to this, when the primary subchannel is occupied by any one of a 20 MHz frame, a 40 MHz frame, and a 60 MHz frame, one or more secondary subchannels become empty until the use of the primary subchannel ends. Therefore, there is a problem in that the efficiency of channel operation is inferior, and there is a problem that a contention with 20 MHz frames for occupying the main subchannel must be won in order to transmit an 80 MHz frame.

In particular, unlike the IEEE 802.11n system using a bandwidth of 40 MHz, since the IEEE 802.11 VHT system uses a bandwidth of 80 MHz, when a 20 MHz frame wins contention, a channel corresponding to a maximum of 60 MHz is wasted. Therefore, in the IEEE 802.11 VHT system, it is necessary to consider more seriously the efficiency of channel operation than the IEEE 802.11n system.

Accordingly, an object of the present invention is to provide a method for improving efficiency of channel operation in a VHT WLAN system using a combined channel consisting of a primary subchannel and a plurality of secondary subchannels.

Another object of the present invention is to provide a method for preventing collocation interference between adjacent subchannels in a VHT WLAN system using a combined channel consisting of a primary subchannel and a plurality of secondary subchannels.

One embodiment of the present invention for solving the above problems is a data transmission method in a VHT WLAN system using a combined channel consisting of a primary subchannel and a plurality of sub-channels, when the primary subchannel is in use And each of the one or more transmitting stations transmits a channel allocation request frame to a receiving station through any subchannel selected from the plurality of sub-channels, and in response to the channel allocation request frame, the receiving station Receiving a channel assignment frame through the combined channel from the at least one transmitting station receiving the channel assignment frame and transmitting a data frame through the subchannel receiving the channel allocation frame.

Another embodiment of the present invention for solving the above problems is a station supporting the data transmission method.

Another embodiment of the present invention for solving the above problems is a channel operating method in a VHT WLAN system using a combined channel consisting of a primary subchannel and a plurality of sub-channels, the primary subchannel is in use The access point may then receive a channel assignment request frame through any subchannel selected from the plurality of sub-channels from one or a plurality of stations and in response to the channel assignment request frame, the access point. Transmitting a channel assignment frame on the combined channel to the station.

Another embodiment of the present invention for solving the above problems is an access point supporting the channel operating method.

Another embodiment of the present invention for solving the above problems is a format of a frame for channel operation in a VHT WLAN system, the frame is a channel allocation request frame, the channel allocation request frame is the channel allocation request frame It contains the address of the station sending it.

Another embodiment of the present invention for solving the above problems is a format of a frame for channel operation in a VHT WLAN system, the frame is a channel allocation frame, the channel allocation frame is a channel allocation request frame Contains the address of the station.

According to an embodiment of the present invention, in a VHT WLAN system using a combined channel consisting of a primary subchannel and a plurality of sub-channels, to provide a channel access method and a data transmission method to improve the efficiency of channel operation It is possible. In particular, according to an embodiment of the present invention, it is possible to prevent the problem of collocation interference that may occur in adjacent subchannels.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 briefly illustrates a configuration of an example of a WLAN system to which an embodiment of the present invention may be applied.

Referring to FIG. 4, the WLAN system includes one or more basic service sets (BSSs). The BSS is a set of stations (STAs) that can successfully synchronize and communicate with each other, and is not a concept indicating a specific area. In addition, a BSS that supports ultra-high speed data processing of 1 GHz or more is called a VHT (Very High Throughput) BSS.

A VHT WLAN system including one or more VHT BSSs may use an 80 MHz channel bandwidth, which is exemplary. For example, the VHT WLAN system may use a channel bandwidth of 60 MHz, 100 MHz, or more. As such, the VHT WLAN system has a multi-channel environment in which a plurality of subchannels having a channel bandwidth of a predetermined size, for example, 20 MHz is included.

The BSS may be classified into an infrastructure BSS (Independent BSS) and an Independent BSS (IBSS). An infrastructure BSS is illustrated in FIG. 4. The infrastructure BSS (BSS1, BSS2) includes one or more STAs (STA1, STA3, STA4), an access point (AP) that is a STA that provides a distribution service, and a plurality of APs (AP1, AP2). Including a distribution system (DS) to connect the (). On the other hand, since the IBSS does not include an AP, all STAs are configured as mobile stations, and thus access to the DS is not allowed, thereby forming a self-contained network.

A STA is any functional medium that includes a medium access control (MAC) compliant with the IEEE 802.11 standard and a physical layer interface to a wireless medium. Broadly speaking, an AP and a non-AP station (Non- AP Station). In addition, a STA that supports ultra-high speed data processing of 1 GHz or more in a multi-channel environment, which will be described later, is referred to as a VHT STA.

The STA for wireless communication includes a processor and a transceiver, and includes a user interface and a display means. The processor is a functional unit designed to generate a frame to be transmitted through a wireless network or to process a frame received through the wireless network, and performs various functions for controlling an STA. The transceiver is a unit that is functionally connected to the processor and is designed to transmit and receive frames over a wireless network for a station.

Among the STAs, the portable terminal operated by the user is a non-AP STA (STA1, STA3, STA4, STA6, STA7, STA8), which is simply referred to as a non-AP STA. The non-AP STA may be a terminal, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal, or a mobile subscriber unit. It may also be called another name (Mobile Subscriber Unit). In addition, a non-AP STA supporting ultra-high speed data processing of 1 GHz or more in a multi-channel environment as described below is referred to as a non-AP VHT STA.

The APs AP1 and AP2 are functional entities that provide access to the DS via a wireless medium for an associated station (STA) associated therewith. In an infrastructure BSS including an AP, communication between non-AP STAs is performed via an AP. However, when a direct link is established, direct communication between non-AP STAs is possible. The AP may be called a centralized controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller in addition to the access point. In addition, an AP supporting ultra-fast data processing of 1 GHz or more in a multi-channel environment, which will be described later, is referred to as a VHT AP.

The plurality of infrastructure BSSs may be interconnected through a distribution system (DS). A plurality of BSSs connected through a DS is called an extended service set (ESS). STAs included in the ESS may communicate with each other, and a non-AP STA may move from one BSS to another BSS while seamlessly communicating within the same ESS.

The DS is a mechanism for one AP to communicate with another AP, which means that an AP transmits a frame for STAs coupled to a BSS managed by the AP or when one STA moves to another BSS. Frames can be delivered with external networks, such as wired networks. This DS does not necessarily need to be a network, and there is no limitation on its form as long as it can provide certain distribution services defined in IEEE 802.11. For example, the DS may be a wireless network such as a mesh network or a physical structure that connects APs to each other.

FIG. 5 illustrates a multi-radio unification protocol, which is an example of a protocol that can be applied to a very high throughput (VHT) system having a plurality of network interface cards (NICs) each having its own radio interface. Block diagram for MUP). Here, the configuration in which the VHT system has a plurality of network interface cards (NICs) is exemplary and may apply a single NIC.

Referring to FIG. 5, an STA supporting MUP includes a plurality of network interface cards (NICs). In FIG. 5, each network interface card NIC is shown separated from each other, which means that each network interface card NIC operates independently of each other. That is, the classification of the network interface card (NIC) shown in FIG. 5 indicates that the network interface card (NIC) is a logical entity operating according to an individual MAC / PHY protocol. Accordingly, the plurality of network interface cards (NICs) may be implemented as functional entities that are physically distinct from each other, or may be integrated into one physical entity.

According to an aspect of this embodiment, the plurality of network interface cards (NICs) may be divided into a primary radio interface (Primary Radio Interface) and one or more secondary radio interface (Secondary Radio Interface). And when there are a plurality of secondary radio interfaces, they may also be classified into a first secondary radio interface, a second secondary radio interface, a third secondary radio interface, and the like. The division of the primary radio interface and the secondary radio interface and / or the division of the secondary radio interface itself may be policy or may be adaptively determined in consideration of the channel environment.

Multiple network interface cards (NICs) are integrated and managed through the Multi-Radio Integration Protocol (MUP). As a result, a plurality of network interface cards (NICs) are recognized as if they were one device to the outside. For this operation, the VHT WLAN system includes a virtual-media access control (V-MAC), wherein the upper layer through the V-MAC is a plurality of network interface cards in a multi-radio channel Not recognized by the NICs. As described above, in the VHT WLAN system, the upper layer does not recognize the multi-radio through the V-MAC. That is, one virtual Ethernet address is provided.

6 is an example of a MAC layer frame.

Referring to FIG. 6, the MAC layer frame consists of nine fields. Among the fields constituting the MAC layer frame, the Frame Control (FC) field has a length of 2 bytes and defines a type of frame and some control information. The Duration (D) field defines the transmission period or ID (ID) of the frame. The Address field consists of four address fields each 6 bytes long, and the Sequence Control (SC) field defines the sequence number of the frame used for flow control. The frame body field has a length of 0 to 2312 bytes and includes information defined by types and subtypes in the FC field. The FCS field is 4 bytes long and contains an error detection order.

Frames can be broadly divided into a management frame, a control frame, and a data frame. The management frame is used at the beginning of communication between the station and the AP, and the control frame is used when accessing the channel or for acknowledgment. Control frames include a Request to Send (RTS) frame, a Clear to Send (CTS) frame, and an Acknowledgment (Ack) frame. Data frames are used to transmit data and control information.

Next, a channel access procedure in a VHT WLAN system according to embodiments of the present invention will be described. Embodiments described below relate to a VHT WLAN system (i.e., a combined channel having an 80 MHz channel bandwidth) using a combined channel composed of four adjacent subchannels having a bandwidth of 20 MHz, but this is merely exemplary. It will be apparent to those skilled in the art that the embodiments of the present invention described below may be equally applied to a VHT WLAN system including a plurality of subchannels, for example, three or five or more subchannels. In addition, the embodiment of the present invention is not limited to a VHT wireless LAN system having a bandwidth of 20 MHz in a subchannel.

7 is a flowchart illustrating a channel access method in a VHT WLAN system according to an embodiment of the present invention.

Hereinafter, the legacy station is a station supporting IEEE 802.11a / b / g / n, and the VHT station is a station supporting IEEE 802.11 VHT. In addition, the VHT station may coexist with the legacy station. In FIG. 7, STA 1 is a legacy station and STA 2 is described as a VHT station, but this is only an example.

First, the VHT WLAN system uses a combined channel composed of a primary subchannel and a plurality of secondary subchannels, and a plurality of stations having data to be transmitted to the AP contend to occupy the primary subchannel. As a result of the competition, it is assumed that one station STA1 wins the competition and is using the primary subchannel, and any one of the plurality of subchannels is empty. In addition, it is assumed that the AP periodically transmits a beacon message including network information including information on a channel contention time (PCHContentiontime). Here, the channel contention time means a time taken for a plurality of stations to compete to occupy the primary subchannel.

First, the VHT station listening to the frame exchange of the primary subchannel calculates the remaining channel occupancy time (PCHResidualTime) of the primary subchannel (S100). The channel occupancy time is calculated using a network allocation vector (NAV).

In general, the period / ID field of the control frame or data frame transmitted by the station includes information on the transmission period. Other stations listening to the frame transmission of the station set the transmission period included in the period / ID field to NAV. Here, the other stations may be stations that do not belong to the corresponding AP.

The VHT station STA 2 having data to be transmitted to the AP transmits a channel allocation request frame through an empty subchannel among the plurality of subchannels (S110). STA 2 may transmit a channel assignment request frame using a carrier sense multiple access (CSMA) based access scheme such as a distributed coordination function (DCF) or enhanced distributed channel access (EDCA). In this case, the CSMA-based access method is a method of checking whether a channel is in use before transmitting a frame to avoid collision between stations and to improve performance.

In addition, the period during which the station transmits the channel assignment request frame to the AP may overlap with the period during which the AP receives another frame on the primary subchannel. Accordingly, it is possible to prevent the coexistence interference problem that may be caused by the overlapping of the frame reception and transmission for one terminal in the adjacent channel in time.

The channel assignment request frame may also be referred to as a Request To Schedule in Secondary Channel (RTSSC) frame. The RTSSC frame is a control frame for requesting allocation of a channel for data transmission to the AP when the use of the primary subchannel of STA 1 ends. The RTSSC frame includes the address of the station transmitting the frame, the time required to transmit data to the AP, the traffic class of the data required to set the scheduling priority, or the buffer status of the station.

STA 2 also wraps the RTSSC frame in a control frame (eg, CTS to self) for legacy stations to interpret, and sets the Duration / ID field to channel contention time + channel occupancy time. Can be sent. Accordingly, legacy stations listening to the sub-channel set the channel contention time + channel occupation time to NAV. Therefore, it is possible to protect the channel allocation request frame and the channel allocation frame transmitted on the sub subchannel within this time in the future from legacy stations. Here, the legacy stations may be stations that do not belong to the corresponding AP.

When the use of the primary subchannel ends, a plurality of stations having data to be transmitted to the AP contend to occupy the primary subchannel (S120). Contention to occupy the primary subchannel is achieved by the AP within the channel contention time (PCHContentionTime). Hereinafter, assuming that STA 1 wins a contention for a 20 MHz frame and the remaining sub-channels are empty.

STA 1 transmits a Request to Send (RTS) frame to the AP through the primary subchannel (S130). The RTS frame is a control frame indicating that there is a data frame to be transmitted by the station to the AP.

The AP receiving the RTS frame transmits a clear to send (CTS) frame to STA 1 through the primary subchannel (S140), and the AP receiving the channel allocation request frame transmits the channel allocation frame to STA 2 through the combined channel. (S141). Here, the CTS frame is a control frame indicating that the AP is ready to receive a data frame from the station. The AP transmits the CTS frame and the channel assignment frame before the channel contention time elapses from the end of the use of the primary subchannel.

The channel assignment frame may be referred to as a scheduling request grant (SRG) frame. The SRG frame is a response frame to the RTSSG frame. The SRG frame includes the address of the station transmitting the RTSSC frame, the reception result of the RTSSC frame, and the time allowed for data transmission to the AP.

In addition, the AP may wrap the SRG frame into a control frame (eg, a CTS) so that legacy stations can interpret it, and set the Duration / ID field to be longer than necessary for data transmission and transmit the same. Accordingly, legacy stations listening to the secondary subchannel set the NAV to a time longer than necessary for the data transmission.

The SRG frame may be transmitted on all subchannels through which stations in the VHT system can transmit data. That is, the SRG frame may be transmitted through all empty subchannels at the time of transmitting the SRG frame, and the subchannel includes a subchannel and a primary subchannel in which the RTSSC frame is not transmitted. In addition, one or more SRG frames may be transmitted on one or more subchannels. At this time, each SRG frame has the same transmission start time point and the same Duration / ID field. In addition, if a CTS frame is transmitted through a primary subchannel at the time when one or more SRG frames are transmitted through one or more sub-channels, the SRG frame and the CTS frame have the same transmission time and the same Duration / ID field. . In addition, the AP may transmit one or more SRG frames having different station addresses through different subchannels, and may be different from station addresses included in simultaneously transmitted CTS frames. If the transmission start time of the SRG frame and the CTS frame is the same, it is possible to prevent the parallel interference problem that may appear by overlapping uplink transmission and downlink transmission between adjacent subchannels.

STA 1 receiving the CTS frame including the same address as its own address transmits a data frame to the AP through the primary subchannel receiving the CTS frame (S150), and allocates a channel including the same address as its own address. The STA 2 receiving the frame transmits a data frame to the AP through the subchannel receiving the channel allocation frame (S151). The data transmission time is set to be equal to or less than the time set in the Duration / ID field of the SRG frame.

Upon receiving the data frame, the AP transmits an acknowledgment (Ack) frame to STA 1 and STA 2 (S160 and S161). Here, when the AP transmits a plurality of Ack frames through the plurality of subchannels, the transmission start time points are made to match. If the transmission start time coincides, parallel interference that may occur due to duplication of uplink transmission and downlink transmission may be prevented.

If the station transmitting the channel allocation request frame does not receive the channel allocation frame until the channel contention time passes from the end of the NAV of the main subchannel, the station may enter a contention window for transmitting the channel allocation request frame. ). Here, the contention period is a predetermined time divided into a plurality of slots, and if the channel allocation frame is not received, the contention period may be increased by a predetermined slot.

According to FIG. 7, even when the primary subchannel is in use by another station, the channel allocation request frame and the channel allocation frame are transmitted through the secondary subchannel, and thus the channel can be efficiently used. In addition, uplink transmission and downlink transmission are performed by setting the transmission start time of the CTS frame and the channel allocation frame, the transmission start time of the data frame of the plurality of stations, and the transmission start time of the Ack frame for the plurality of stations of the AP. Overlapping problems of collocation interference can be prevented.

8 is a view showing a channel operating method of the 80MHz bandwidth according to an embodiment of the present invention.

Referring to FIG. 8, it is assumed that a primary subchannel is in use by a 20 MHz frame of a legacy station. Each of the VHT STA 1 and the VHT STA 2 having data to be transmitted to the AP transmits a Request to Schedule in Secondary Channel (RTSSC) frame through the sub subchannel 1 and the sub subchannel 3 to the AP. As shown in FIG. 8, each VHT STA may transmit at least one RTSSC frame. The RTSSC frame sets the duration / ID field to the sum of the channel occupancy time and the channel contention time. Other stations listening to the RTSSC frame set the sum of the channel occupancy time and the channel contention time in the duration / ID field to NAV.

When the legacy station's primary subchannel usage ends, a channel contention timer starts and stations with data to send to the AP contend to occupy the primary subchannel. In the following, assume that a legacy station of 20 MHz frame has won contention. The legacy station sends an RTS frame to the AP on the primary subchannel. The AP transmits the CTS frame to the legacy station before the channel contention timer expires, and transmits the SRG frame to the VHT STA 1 and the VHT STA 2. Here, transmission start time points of the CTS frame and the SRG frame are the same. The CTS frame and the SRG frame set the duration / ID field to more than the time required for data frame transmission. Stations listening to the CTS frame and the SRG frame set a value greater than the time required for transmitting the data frame to NAV.

The legacy station receiving the CTS frame transmits the data frame to the AP through the primary subchannel, and the VHT STA 1 and VHT STA 2 receiving the SRG frame transmit the data frame to the AP through the subchannel receiving the SRG frame. do. Here, the transmission start time of the data frame may be the same.

Upon receiving the data frame, the AP transmits an Ack frame to the legacy stations, the VHT STA 1 and the VHT STA 2 to confirm receipt of the data frame.

According to an embodiment of the present invention, even when the primary subchannel is in use, since the frame is transmitted through the secondary subchannel, the efficiency of the channel can be increased, and the uplink transmission and the downlink transmission do not overlap between adjacent subchannels. The problem of juxtaposition interference can be prevented.

The invention can be implemented in hardware, software or a combination thereof. In hardware implementation, an application specific integrated circuit (ASIC), a digital signal processing (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, and a microprocessor are designed to perform the above functions. , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

As mentioned above, preferred embodiments of the present invention have been described in detail, but those skilled in the art to which the present invention pertains should understand the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. It will be appreciated that various modifications or changes can be made. Accordingly, modifications to future embodiments of the present invention will not depart from the technology of the present invention.

1 is a diagram illustrating an example of juxtaposition interference.

2 illustrates an example of frame transmission when a 20 MHz frame wins a contention for occupying a main subchannel in an IEEE 802.11 VHT WLAN system.

3 illustrates an example of frame transmission when an 80 MHz frame wins a contention for occupying a main subchannel in an IEEE 802.11 VHT WLAN system.

4 briefly illustrates a configuration of an example of a WLAN system to which an embodiment of the present invention may be applied.

FIG. 5 illustrates a multi-radio unification protocol (MUP), which is an example of a protocol that may be applied to a very high throughput (VHT) system having a plurality of network interface cards (NICs) each having its own radio interface. Block diagram

6 is an example of a MAC layer frame.

7 is a flowchart illustrating a channel access method in a VHT WLAN system according to an embodiment of the present invention.

8 is a view showing a channel operating method of the 80MHz bandwidth according to an embodiment of the present invention.

Claims (15)

A data transmission method in a VHT wireless LAN system using a combined channel consisting of a primary subchannel and a plurality of secondary subchannels, If the primary subchannel is in use, each of the one or a plurality of transmitting stations transmits a channel assignment request frame to a receiving station via any subchannel selected from the plurality of subsubchannels; In response to the channel assignment request frame, receiving a channel assignment frame from the receiving station over the combined channel; And The one or more transmitting stations receiving the channel allocation frame transmits the data frame through the sub-channel receiving the channel allocation frame. The method of claim 1, The channel allocation request frame is packed in a control frame format that can be interpreted by the legacy station data transmission method in a VHT WLAN system. The method of claim 2, The Duration / ID field of the control frame is set to a channel contention time + channel occupancy time. The station supporting the data transmission method of the VHT WLAN system of claim 1. A channel operating method in a VHT wireless LAN system using a combined channel consisting of a primary subchannel and a plurality of secondary subchannels, If the primary subchannel is in use, the access point receives a channel assignment request frame from any one or a plurality of stations on any subchannel selected from the plurality of subsubchannels; And And in response to the channel allocation request frame, the access point transmitting a channel allocation frame to the station through the combined channel. The method of claim 5, wherein The channel allocation frame is a channel operating method in a VHT WLAN system, characterized in that the package is packed in a control frame that can be interpreted by the legacy station. The method of claim 5, wherein The access point further comprises the step of transmitting the CTS frame on the primary sub-channel simultaneously with the transmission of the channel allocation frame channel operating method in a VHT WLAN system. The method of claim 7, wherein The method of operating a channel in a VHT WLAN system, characterized in that the transmission start time of the channel allocation frame and the CTS frame is the same. The method of claim 7, wherein And in response to receiving the data frame, transmitting the acknowledgment frame to one or a plurality of stations. The method of claim 9, The method of operating a channel in the VHT WLAN system, characterized in that the transmission start time of the acknowledgment frame for the plurality of stations are the same. An access point supporting a channel operating method of the VHT WLAN system of claim 5. In the format of a frame for channel operation in a VHT WLAN system, The frame is a channel allocation request frame, The channel allocation request frame is a frame format for channel operation in a VHT WLAN system, characterized in that it comprises the address of the station transmitting the channel allocation request frame. The method of claim 12, The channel allocation request frame further includes a time required for transmitting data to an access point and a buffer state of the station. In the format of a frame for channel operation in a VHT WLAN system, The frame is a channel assignment frame, And the channel allocation frame includes an address of a station that has transmitted a channel allocation request frame. The method of claim 14, The channel allocation frame further comprises a period of time allowed for transmitting data to the access point and the reception result of the channel allocation request frame frame format for operation in the VHT WLAN system.

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