KR101984918B1 - Method for generating and transmitting frame in a wireless local area network and apparatus for the same - Google Patents

Abstract

Provided are a frame transmission method by a transmission station (STA) in a WLAN system. The method transmits short training symbols for coarse frequency offset estimation and timing synchronization to a receiving STA, and long training symbols for fine frequency offset estimation and channel estimation. Is transmitted to the receiving STA, a first signal symbol including control information is transmitted to the receiving STA, a second signal symbol including the control information is transmitted to the receiving STA, and the first data symbol is received. Sending to the STA and sending a second data symbol to the receiving STA.

Description

TECHNICAL FOR GENERATING AND TRANSMITTING FRAME IN A WIRELESS LOCAL AREA NETWORK AND APPARATUS FOR THE SAME}

The present invention relates to wireless communication, and more particularly, to a method for generating and transmitting a frame for extending service coverage in a WLAN system and an apparatus for supporting the same.

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), or the like. It is a technology that allows wireless access to the Internet in a specific service area.

WLAN technology has been in the spotlight as a wireless communication technology that provides high-speed data services in an unlicensed band. In particular, unlike conventional cellular communication systems, an access point that acts as a base station can be easily installed and priced when powered and connected to a wired network. It is inexpensive and can be used for data communication.

Decentralized operation, which is one of the features of the WLAN, has the advantage of enabling simple operation, and is spreading to sensor networks and smart utility networks. In the case of the sensor network and the smart utility network, since the amount of data to be transmitted is not large and the transmission period is also short, it may be more important to expand the service coverage by the WLAN system than to improve the transmission speed.

Accordingly, in order to extend the coverage of a WLAN system, a repetitive transmission method for extending a service coverage to a relay technique and a method for generating a frame having a structure for supporting the same are required.

SUMMARY The present invention has been made in an effort to provide a method for generating and transmitting a frame for extending service coverage in a WLAN system and an apparatus supporting the same.

In one aspect, a frame transmission method by a transmission station (STA) in a WLAN system is provided. The method transmits short training symbols for coarse frequency offset estimation and timing synchronization to a receiving STA, and long training symbols for fine frequency offset estimation and channel estimation. Is transmitted to the receiving STA, a first signal symbol including control information is transmitted to the receiving STA, a second signal symbol including the control information is transmitted to the receiving STA, and the first data symbol is received. Sending to the STA and sending a second data symbol to the receiving STA.

The first signal symbol and the second signal symbol may be orthogonal frequency division multiplexing (OFDM) symbols.

The second signal symbol may be a cyclic OFDM repeating symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0.

The second data symbol may be a symbol in which the first data symbol is cyclic OFDM repeated.

The first signal symbol may be a Binary Phase Shift Keying (BPSK) modulation applied.

The second signal symbol may be a quadrature binary phase shift keying (QBPSK) modulation.

The control information may include information indicating that the first signal symbol and the second signal symbol in which the first signal symbol is repeated in the cyclic OFDM are transmitted.

The second data symbol may be a symbol in which the first signal symbol is the cyclic OFDM repeated.

The method may further include transmitting a third signal symbol identical to the first signal symbol, and transmitting a fourth signal symbol identical to the second signal symbol.

The method may further include transmitting a third data symbol that is identical to the first data symbol, and transmitting a fourth data symbol that is identical to the second data symbol.

The third signal symbol may be transmitted between the first signal symbol and the second signal symbol.

The fourth signal symbol may be transmitted after the second signal symbol.

The first signal symbol may be one to which BPSK modulation is applied.

QBPSK modulation may be applied to the second signal symbol, the third signal symbol, and the fourth signal symbol.

The control information may include information indicating that the first signal symbol, the second signal symbol, the third signal symbol, and the fourth signal symbol are transmitted.

In another aspect, a wireless device is provided. The apparatus includes a transceiver for transmitting and receiving wireless signals and a processor operatively coupled to the transceiver. The processor transmits short training symbols for coarse frequency offset estimation and timing synchronization to a receiving device, and long training symbols for fine frequency offset estimation and channel estimation. Is transmitted to the receiving device, a first signal symbol including control information is transmitted to the receiving device, a second signal symbol including the control information is transmitted to the receiving device, and the first data symbol is transmitted to the receiving device. Send to the receiving device and send a second data symbol to the receiving device.

The first signal symbol and the second signal symbol may be orthogonal frequency division multiplexing (OFDM) symbols.

The second signal symbol may be a cyclic OFDM repeating symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0.

In another aspect, a method for receiving a frame by a receiving station (STA) in a WLAN system is provided. The method transmits short training symbols for coarse frequency offset estimation and timing synchronization from a transmitting STA, and long training symbols for fine frequency offset estimation and channel estimation. Is received from the transmitting STA, the first signal symbol containing control information is received from the transmitting STA, the second signal symbol containing the control information is received from the transmitting STA, and the first data symbol is received. Receiving from a transmitting STA and receiving a second data symbol from the transmitting STA.

The first signal symbol and the second signal symbol may be orthogonal frequency division multiplexing (OFDM) symbols.

The second signal symbol may be a cyclic OFDM repeating symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0.

The present invention proposes a repetitive transmission scheme for improving the reception sensitivity of a WLAN system, and proposes a frame structure and performance improvement schemes to support this based on the WLAN standard. If such a method is supported, the data transmission speed is lowered, but the service coverage of the WLAN system is expanded. Therefore, more reliable and efficient services can be provided in applications such as sensor networks that require wide coverage rather than high transmission speed.

1 is a diagram illustrating a physical layer architecture of a WLAN system supported by IEEE 802.11.
2 illustrates cyclic OFDM symbol repetition.
3 is a diagram illustrating a structure of an OFDM symbol that can be used for 4th repeated transmission according to an embodiment of the present invention.
4 is a block diagram illustrating a frame format applicable to repetitive transmission according to an embodiment of the present invention.
5 is a diagram illustrating a frame format according to an embodiment of the present invention to which repetitive transmission is applied.
6 is a diagram illustrating another example of a frame format according to an embodiment of the present invention.
7 is a diagram illustrating a format of a signal field according to an embodiment of the present invention.
8 is a diagram illustrating a configuration of a rate subfield according to an embodiment of the present invention.
9 is a diagram illustrating a constellation mapping method applied to a signal field according to an embodiment of the present invention.
10 illustrates an example of an HT frame format according to an embodiment of the present invention.
11 illustrates another example of an HT frame format according to an embodiment of the present invention.
12 is a block diagram illustrating a wireless device in which an embodiment of the present invention may be implemented.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, “unit”, etc. described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. It can be implemented as.

A wireless local area network (WLAN) system to which an embodiment of the present invention can be applied includes one or more basic service sets (BSSs). The BSS is a set of stations (STAs) that can successfully communicate with each other by synchronizing, and is not a concept indicating a specific area.

A STA is any functional medium that includes a medium access control (MAC) compliant with the IEEE of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and a physical layer interface to a wireless medium. It includes both AP and Non-AP Stations.

A non-AP STA is an STA, not an AP, and a non-AP STA is a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), It may also be called a mobile station (MS), mobile subscriber unit, or simply another name such as user. Hereinafter, for convenience of description, a non-AP STA is referred to as an STA.

An AP is a functional entity that provides access to a DS via a wireless medium for an associated STA to that AP. In an infrastructure BSS including an AP, communication between STAs is performed via an AP. However, when a direct link is established, direct communication between STAs is possible. The AP may be called a central controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller.

1 is a diagram illustrating a physical layer architecture of a WLAN system supported by IEEE 802.11.

The PHY architecture of IEEE 802.11 includes a PHY Layer Management Entity (PLME), a Physical Layer Convergence Procedure (PLCP) sublayer 110, and a Physical Medium Dependent (PMD) sublayer 100. PLME cooperates with the MAC Layer Management Entity (MLME) to provide the management of the physical layer. The PLCP sublayer 110 transfers the MAC Protocol Data Unit (MPDU) received from the MAC sublayer 120 to the sublayer between the MAC sublayer 120 and the PMD sublayer 100 according to an instruction of the MAC layer. The frame coming from the PMD sublayer 100 is transferred to the MAC sublayer 120. The PMD sublayer 100 is a PLCP lower layer to enable transmission and reception of physical layer entities between two stations through a wireless medium. The MPDU delivered by the MAC sublayer 120 is referred to as a physical service data unit (PSDU) in the PLCP sublayer 110. The MPDU is similar to the PSDU. However, when an A-MPDU (aggregated MPDU) that aggregates a plurality of MPDUs is delivered, the individual MPDUs and the PSDUs may be different from each other.

The PLCP sublayer 110 adds an additional field including information required by the physical layer transceiver in the process of receiving the PSDU from the MAC sublayer 120 and transmitting it to the PMD sublayer 100. In this case, the added field may be a PLCP preamble, a PLCP header, and tail bits required to return the convolutional encoder to a zero state in the PSDU. The PLCP sublayer 110 receives a TXVECTOR parameter from the MAC sublayer, which includes control information necessary for generating and transmitting the PPDU and control information necessary for the receiving STA to receive and interpret the PPDU. The PLCP sublayer 110 uses the information included in the TXVECTOR parameter to generate a PPDU containing the PSDU.

The PLCP preamble serves to prepare the receiver for synchronization and antenna diversity before the PSDU is transmitted. The data field may include a coded sequence encoded with a padding bits, a service field including a bit sequence for initializing a scraper, and a bit sequence appended with tail bits in the PSDU. In this case, the encoding scheme may be selected from either binary convolutional coding (BCC) encoding or low density parity check (LDPC) encoding according to the encoding scheme supported by the STA receiving the PPDU. The PLCP header includes a field containing information on a PLC Protocol Data Unit (PPDU) to be transmitted.

The PLCP sublayer 110 adds the above-described fields to the PSDU, generates a PPDU (PLCP Protocol Data Unit), and transmits the data to the receiving station via the PMD sublayer. Obtain and restore information necessary for restoration. The PLCP sublayer of the receiving station transmits an RXVECTOR parameter including the PLCP preamble and control information included in the PLCP header to the MAC sublayer so that the PPDU can be interpreted and the data can be obtained in the reception state.

Most transmission specifications of the WLAN system have been developed for improving the transmission speed. Transmission speed improvement could be achieved through MIMO (Multiple Input Multiple Output) and bandwidth expansion.

In the general network environment, the improvement of the transmission speed may be significant in connection with the meaning of increasing network capacity. However, in a network for collecting information such as a sensor network, the expansion of coverage may be more important. When the coverage is expanded, it means that information can be collected in a large area through a small number of APs, so that a sensor network can be constructed at a low cost.

The coverage extension of the WLAN system is related to the transmission power used in the wireless signal transmission and the reception sensitivity at the receiver side. If you transmit a radio signal with higher transmission power, the radio signal can reach a greater distance. However, since the transmission power is limited by the communication protocol, it cannot be increased without restriction for coverage expansion. In addition, since the wireless communication entity may be a low cost, small wireless device in the sensor network, the transmission power available in the wireless device may be limited.

Therefore, in the present invention, the coverage extension of the WLAN may be implemented by a method capable of improving the receiver side reception sensitivity to more accurately receive the radio signal. To this end, an embodiment of the present invention proposes a method of repeatedly transmitting an Orthogonal Frequency Division Multiplexing (OFDM) symbol, which is a radio signal, and a frame format applied to the method. Hereinafter, with reference to the drawings will be described in more detail.

2 illustrates cyclic OFDM symbol repetition.

2, N data subcarriers are included in one OFDM symbol. The N subcarriers are divided into two groups based on the DC component, that is, the subcarrier index 0. Therefore, one subcarrier group among two subcarriers divided into two groups has a positive index value and the other group has a negative index value.

Cyclic OFDM symbol repetition is to transmit the included OFDM symbol by changing the position of the subcarrier group included in the OFDM symbol to be transmitted first. In FIG. 2, subcarriers A ₁ to A _{N / 2} in the above OFDM symbol transmitted first are subcarrier groups having negative indices, and subcarriers A _{N / 2 + 1} to A _N are positive indices. It corresponds to the subcarrier group having. On the other hand, it can be seen that the positions of subcarriers are reversed in the following OFDM symbol.

This repetition of the cyclic OFDM symbol makes it possible to obtain a frequency diversity gain. The cyclic OFDM symbol repetition as shown in FIG. 2 can be easily applied to two repetitive transmissions.

3 is a diagram illustrating a structure of an OFDM symbol that can be used for 4th repeated transmission according to an embodiment of the present invention.

Referring to FIG. 3, a simple OFDM symbol repetition for sending the same OFDM symbol again and a cyclic OFDM symbol repetition described with reference to FIG. 2 are combined to indicate that four repetitive transmissions may be implemented.

The second OFDM symbol corresponds to a simple repetition of the first OFDM symbol.

The third OFDM symbol corresponds to a repeating cyclic OFDM symbol of the first OFDM symbol. The fourth OFDM symbol corresponds to a simple repetition of the third OFDM symbol.

4 repeated transmissions as shown in FIG. 3 may further improve reception sensitivity than twice repeated transmissions. Although the OFDM symbols to be applied in four repetitive transmissions can be defined by dividing the subcarriers into four groups and changing their positions cyclically, cyclic OFDM because the added gain decreases as the diversity order increases. The symbol repetition may be applied once, and the remaining repetitions may adopt a method of obtaining only a power gain by simple repetition. In the case of implementing four repetitive transmissions using such cyclic OFDM symbol repetition and simple repetition, it is possible to vary the setting of the cyclic prefix (CP), which may be more efficient.

4 is a block diagram illustrating a frame format applicable to repetitive transmission according to an embodiment of the present invention.

In general, when the OFDM technique is applied, a CP-type guard interval is set so that the delay of the previous OFDM symbol does not affect the corresponding OFDM symbol. The sub-figure (a) shows an example of a general case, and a CP is added between OFDM symbols repeatedly transmitted.

Sub-blot (b) shows an example in which no CP is added before the second OFDM symbol and the fourth OFDM symbol. Since the second OFDM symbol and the fourth OFDM symbol are the same forms as the first OFDM symbol and the fourth OFDM symbol, respectively, even if CP is not added, performance degradation may not occur because there is no interference effect between symbols. Throughput can be improved by saving transmission time by two CPs while transmitting four OFDM symbols.

The sub-view (c) shows the configuration of a frame in which the length of the CP added before the first and third OFDM symbols is doubled. In this case, the delay spread of the channel is also increased because the purpose of the repetitive transmission is the coverage extension, so that the length of the existing CP may be shorter than the maximum channel delay spread time. Accordingly, the length of the CP can be doubled to correspond to the channel delay spread time lengthened by the extended coverage. Since the CP is not added to the second and fourth OFDM symbols even if the length of the CP is doubled, the length of the entire frame is equal to the frame of the format as shown in (a). Therefore, the effect of covering up to twice as long channel spread delay without a decrease in throughput can be obtained.

In the following description of the frame format, a representation of a field is used as a component of a frame. However, a representation of a symbol, such as a data symbol, may be used to refer to a component that is transmitted after being modulated.

5 is a diagram illustrating a frame format according to an embodiment of the present invention to which repetitive transmission is applied.

Sub-a diagram (a) shows a basic frame format of a WLAN system. Referring to the sub-view (a), the frame 500a includes a short training field (510a), a long training field (520a), a signal (SIG) field 530a, and a data field 540a. do. Each field except the DATA field 540a is transmitted through one OFDM symbol. The DATA field 540a may be transmitted through at least one or more OFDM symbols as shown.

 The STF 510a may be used for signal sensing, automatic gain control (AGC), diversity selection, coarse frequency offset estimation, and timing synchronization. The LTF 520a may be used for channel estimation and fine frequency offset estimation. The SIG field 530a includes rate information and information indicating a length of a data unit included in a frame as control information.

Sub-blot (b) shows a frame format used when two repetitive transmissions are applied. Referring to the sub-figure (b), the frame 500b is subjected to cyclic OFDM symbol repetition to the SIG field and the data field in the same format as (a).

Sub-figure (c) shows the frame format used when the fourth repetitive transmission is applied. Referring to the sub-figure (c), the frame 500c has a structure in which the SIG field and the data field are repeated four times, two simple repetitions and the other two cyclic OFDM symbol repetitions. At this time, the CP structure of the SIG field and the DATA field to which the fourth repetition transmission is applied may be all three structures shown in FIG. However, in the case of the SIG field, a structure in which CP is added to every OFDM symbol may be more preferable. This is to enable automatic detection of the number of repetitions and the number of times through constellation mapping. Hereinafter, this will be described in detail with reference to the accompanying drawings.

6 is a diagram illustrating another example of a frame format according to an embodiment of the present invention.

In the case of a frame to which 2 repetitions or 4 repetitions are applied, reception sensitivity is greatly improved. Therefore, if the STF is short, the performance of carrier sensing for checking the presence or absence of packets at the receiving end may be deteriorated. If carrier sensing performance decreases, packets may not be received. Therefore, the length of the STF needs to be extended to improve the performance of carrier sensing. Referring to FIG. 6, it can be seen that the length of the STF is extended in the sub-view (a) that is the frame format for the second repeated transmission and the sub-view (b) that is the frame format for the fourth repeated transmission. If a given waveform has a structure of repeating 10 times in a WLAN system, the extended STF has a structure of repeating the same waveform more than 10 times. For example, if the STF consists of 160 samples in total, and this is a structure in which a 16-sample waveform is repeated 10 times, an extended STF means that the waveform of 16 samples is extended to more than 10, that is, 15 or 20 samples, and so on. The number of may be 240 or 320 and the like.

On the other hand, information may be needed to distinguish whether a receiving STA is a frame that is repeatedly transmitted or repeated twice or transmitted four times. For this purpose, a rate subfield and a spare field of the signal field may be used.

7 is a diagram illustrating a format of a signal field according to an embodiment of the present invention.

Referring to FIG. 7, the signal field 700 may include a rate subfield 710, a spare bit 720, a length subfield 730, a parity bit 740, and a signal tail subfield ( 750). The length subfield 730 indicates the length of the data unit included in the frame. Parity bit 740 is a bit for parity check. Signal tail subfield 750 includes tail bits.

The rate subfield 710 may have a length of 4 bits and may indicate 16 modes. The existing rate subfield could define eight rates, which is a combination of four mapping methods and three code rates. Accordingly, the rate subfield 710 may be set to indicate eight rates in the absence of repetitive transmission and eight rates in the situation in which cyclic OFDM symbol repetition is applied.

8 is a diagram illustrating a configuration of a rate subfield according to an embodiment of the present invention.

Referring to FIG. 8, it is possible to know the configuration of a rate field for eight rate indications when repetitive transmission is not applied and eight rate indications when repetitive transmission according to cyclic OFDM symbol repetition is applied. In this case, if the value of R4, which is the last fourth bit of the rate field, is 0, it may be interpreted as indicating a rate when repetitive transmission is not applied, and if it is 1, indicating a rate when repetitive transmission is applied.

Referring to FIG. 7 again, the reserved bit 720 may be set to indicate whether the frame format is repeated according to the second repeated transmission or the frame format according to the fourth repeated transmission. If 0 is a frame format to which simple repetition is not applied, and if 1, simple repetition is applied to indicate that the frame format is according to the 4th repetition transmission.

As described above, when the 4-bit rate subfield 710 and the 1-bit spare bit 720 are not repeatedly transmitted, it is possible to distinguish both the case of repeatedly transmitting twice and the case of repeatedly transmitting four times.

Meanwhile, a method for allowing a receiving STA to automatically detect that repetitive transmission is applied without demodulating and analyzing a signal field may be proposed.

9 is a diagram illustrating a constellation mapping method applied to a signal field according to an embodiment of the present invention. BPSK modulation is applied to the signal field for the first OFDM symbol and QBPSK modulation is applied to the signal field for the remaining OFDM symbols.

Sub-view (a) indicates the modulation scheme applied to the signal field when repetitive transmission is not applied. In this case, since the signal field is not repeatedly transmitted, the signal field is transmitted as an OFDM symbol by applying BPSK modulation.

Sub-blot (b) indicates the modulation scheme applied to the signal fields in the case where two repetitive transmissions are applied. In this case, BPSK modulation is applied to the first transmitted signal field and QBPSK modulation is applied to the second transmitted signal field.

Sub-figure (c) indicates the modulation scheme applied to the signal fields when the fourth repetitive transmission is applied. In this case, BPSK modulation is applied to the first transmitted signal field and QBPSK modulation is applied to the remaining signal fields.

As shown in FIG. 9, all the OFDM symbols except for the OFDM symbol for the first signal field are transmitted with QBPSK modulation applied, so that the receiving STA modulates without checking the values of the rate subfield and the reserved bits included in the signal field. You can know the number of repetitions only by checking the method. The receiving STA may know that repetitive transmission is applied when the first received OFDM symbol is applied with BPSK modulation and the next OFDM symbol is applied with QBPSK modulation. In addition, it can be determined whether QBPSK modulation is applied to the transmitted OFDM symbol and whether it is 2 times or 4 times.

Such a repeated transmission method may be applied to an HT WLAN system.

10 illustrates an example of an HT frame format according to an embodiment of the present invention.

Sub-view (a) shows the format of an existing HT frame. In the HT frame, an HT-Signal (HT-SIG) field is transmitted through two OFDM symbols. Each HT-SIG field may be divided into an HT-SIG1 field and an HT-SIG2 field.

The sub-figure (b) shows the format of the HT frame when the second repetitive transmission is applied. In this case, the HT-SIG1 field and the HT-SIG2 field may be viewed as one unit, and cyclic OFDM symbol repetition may be applied. Accordingly, the HT-SIG1 field and the HT-SIG2 field to which cyclic OFDM symbol repetition is applied may be further included.

Information for indicating, by the receiving STA, whether the transmitted frame is a frame to which repetitive transmission is applied may be included in the HT-SIG field. To this end, a 7-bit subfield that defines the MCS (modulation and coding scheme) of the HT-SIG field and a 1-bit spare bit are set to indicate whether to apply the repetitive, repeat 2, and repeat 4 transmissions. can do.

In addition, another modulation scheme may be applied so that the receiving STA knows whether the repetitive transmission is applied only by the constellation mapping state before demodulation and interpretation of the HT-SIG field. BPSK modulation is applied to the HT-SIG1 and HT-SIG2 fields transmitted first, and then transmitted as OFDM symbols, and QBPSK modulation is applied to the second HT-SIGA1 and HT-SIG2 fields.

In addition, the length of the L-STF may be extended to improve the performance of carrier sensing.

Sub-figure (c) shows the format of the HT frame when the fourth repetitive transmission is applied. In this case, the HT-SIG1 field and the HT-SIG2 field may be simply repeated, and may include two HT-SIG1 fields and two HT-SIG2 fields to which cyclic OFDM symbol repetition is applied.

Like the sub-view (b), the HT-SIG field may include an MCS subfield and a reserved bit set to indicate whether repeated transmission is applied.

The first HT-SIG1 field and the HT-SIG2 field may be transmitted as OFDM symbols by applying BPSK modulation, and may be transmitted by applying QBPSK modulation to a subsequent transmitted field.

The length of the L-STF may be extended to improve the performance of carrier sensing.

11 illustrates another example of an HT frame format according to an embodiment of the present invention. FIG. 11 is a HT-green frame that can be used in an HT WLAN system composed of only STAs supporting HT.

In the frame format of FIG. 11, similarly to FIG. 10, the HT-SIG1 field and the HT-SIG2 field may be repeatedly included. The HT-SIG field may include an MCS subfield and a reserved bit set to indicate whether to repeatedly transmit.

In addition, the first HT-SIG1 field and the HT-SIG2 field may be transmitted by applying BPSK modulation, and then the simple repeated field and the cyclic OFDM symbol repeated field may be transmitted by applying QBPSK modulation.

12 is a block diagram illustrating a wireless device in which an embodiment of the present invention may be implemented. 12 may be an AP or an STA.

Referring to FIG. 12, a wireless device 1200 includes a processor 1210, a memory 1220, and a transceiver 1230. The transceiver 1230 transmits and / or receives a radio signal, but implements a physical layer of IEEE 802.11. The processor 1210 may be configured to be functionally connected to the transceiver 930 to implement the embodiments of the invention shown in FIGS. 1 to 11.

The processor 1210 and / or transceiver 1230 may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the memory 1220 and executed by the processor 1210. The memory 1220 may be included in the processor 1210 and may be functionally connected to the processor 1210 through various known means that are separately located outside.

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. The above embodiments are only to be understood as technical idea, and should not be construed as being limited thereto. Accordingly, the scope of the present invention is not limited by the specific embodiments, but is determined by the claims, and changes in the future embodiments of the present invention will not depart from the technology of the present invention.

Claims (21)

In the frame transmission method by a transmission station (STA) in a WLAN system,
Transmit a first signal symbol including control information to a receiving STA,
Transmit a second signal symbol including the control information to the receiving STA,
Send a first data symbol to the receiving STA, and
Transmitting a second data symbol to the receiving STA;
And at least one of the second signal symbol and the second data symbol is a cyclic repetitive symbol including subcarriers in which subcarriers of a previously transmitted symbol are displaced. The method of claim 1,
Transmit a short training symbol for coarse frequency offset estimation and timing synchronization to a receiving STA,
Sending a long training symbol for fine frequency offset estimation and channel estimation to the receiving STA,
And the first signal symbol and the second signal symbol are orthogonal frequency division multiplexing (OFDM) symbols. The method of claim 1,
And the second signal symbol is a cyclic repetitive symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0. The method of claim 1,
And wherein the second data symbol is a cyclic repetitive symbol including subcarriers arranged by changing the position of subcarriers of the first data symbol based on subcarrier index 0. The method of claim 3, wherein
And the first signal symbol is subjected to binary phase shift keying (BPSK) modulation. The method of claim 5,
The second signal symbol is a frame transmission method characterized in that Quadrature Binary Phase Shift Keying (QBPSK) modulation is applied. The method of claim 3, wherein
The control information,
And information indicating that the first signal symbol and the second signal symbol, which is a cyclic repetition symbol of the first signal symbol, are transmitted. The method of claim 7, wherein
And the second data symbol is a cyclic repetitive symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0. The method of claim 3, wherein the method is
Transmit a third signal symbol equal to the first signal symbol, and
And transmitting a fourth signal symbol identical to the second signal symbol. The method of claim 4, wherein the method
Transmit a third data symbol equal to the first data symbol, and
And transmitting a fourth data symbol identical to the second data symbol. The method of claim 9,
And wherein the third signal symbol is transmitted between the first signal symbol and the second signal symbol, and the fourth signal symbol is transmitted subsequent to the second signal symbol. delete The method of claim 11,
BPSK modulation is applied to the first signal symbol, and QBPSK modulation is applied to the second signal symbol, the third signal symbol, and the fourth signal symbol. delete delete A transceiver for transmitting and receiving wireless signals,
Including a processor that is functionally coupled to the transceiver to operate,
The processor,
Transmitting a short training symbol for coarse frequency offset estimation and timing synchronization to a receiving device,
Transmitting a long training symbol for fine frequency offset estimation and channel estimation to the receiving apparatus,
Transmit a first signal symbol including control information to the receiving device,
Transmit a second signal symbol including the control information to the receiving device,
Send a first data symbol to the receiving device, and
Transmit a second data symbol to the receiving device,
And at least one of the second signal symbol and the second data symbol is a cyclic repetitive symbol including subcarriers in which subcarriers of a previously transmitted symbol are displaced. The method of claim 16,
And wherein the second data symbol is a cyclic orthogonal frequency division multiplexing (OFDM) repetitive symbol including subcarriers arranged by changing the position of subcarriers of the first data symbol based on subcarrier index 0. The method of claim 16,
And the second signal symbol is a cyclic OFDM repetition symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0. In a frame receiving method by a receiving station (STA) in a WLAN system,
Transmit a short training symbol for coarse frequency offset estimation and timing synchronization from a transmitting STA,
Receiving a long training symbol for fine frequency offset estimation and channel estimation from the transmitting STA,
Receiving a first signal symbol including control information from the transmitting STA,
Receiving a second signal symbol including the control information from the transmitting STA,
Receive a first data symbol from the transmitting STA, and
Receive a second data symbol from the transmitting STA,
And at least one of the second signal symbol and the second data symbol is a cyclic repetitive symbol including a subcarrier in which subcarriers of a previously transmitted symbol are displaced. The method of claim 19,
The second data symbol is a frame reception method, characterized in that the cyclic orthogonal frequency division multiplexing (OFDM) repetition symbol including subcarriers arranged by changing the position of subcarriers of the first data symbol based on subcarrier index 0. . The method of claim 20,
And wherein the second signal symbol is a cyclic OFDM repeating symbol including subcarriers arranged by changing the position of subcarriers of the first signal symbol based on subcarrier index 0.

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