KR20110051129A - Method and apparatus for configuring PLC frame in JHT wireless LAN system - Google Patents

Abstract

Provided are a physical layer convergence procedure (PLCP) frame configuration method and a device supporting the same in a Very High Throughput (VHT) wireless LAN system. PLCP frame configuration method according to the present invention generates an MPDU (MAC Protocol Data Unit) to be transmitted to the destination STA (station, STA), the control information for the L-SIG field and VHT STA containing the control information for the legacy STA in the MPDU Generating a PPDU (PLCP Protocol Data Unit) by attaching a physical layer convergence procedure (PLCP) header including a VHT-SIG field, and transmitting the PPDU to the destination station, wherein the OFDM symbol of the VHT-SIG field is included. The constellation applied to is characterized in that the constellation obtained by rotating the constellation applied to the OFDM symbol of the L-SIG field.

Description

Method and Apparatus of configuring physical layer convergence procedure (PLCP) frame in Very High Throughput (VHT) Wireless Local Area Network (WLAN) system}

The present invention relates to wireless communication, and more particularly, to a method for configuring a PLCP frame in a VHT WLAN system and a wireless device 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), 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 for 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.

In order to overcome the limitation of communication speed, which has been pointed out as a weak point in WLAN, IEEE 802.11n is a relatively recent technical standard. 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 and also uses multiple antennas at both the transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology. 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.

In the IEEE 802.11n High Throughput (HT) WLAN system, in addition to the PLCP format supporting legacy STAs, HT Greenfield, a PLCP format efficiently designed for HT STAs, can be used in a system composed of only HT STAs supporting IEEE 802.11n. field) The PLCP format was introduced. It also supports HT mixed PLCP format, a PLCP format designed to support HT systems in systems where legacy STAs and HT STAs coexist.

In the HT mixed PLCP frame, the HT-SIG field is encoded and interleaved and then mapped for modulation, which uses QBPSK constellation. QBPSK constellation is rotated 90 ° BPSK constellation. Since the L-SIG field uses a general BPSK property, it is easy to detect the HT-SIG field.

For more information on the HT Greenfield PLCP format and the HT Mixed PLCP format, see “IEEE P802.11n ™ / D11.0, Draft STANDARD for Information Technology-Telecommunications and information exchange between systems-Local and metropolitan area networks”, which was released in June 2009. -Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 5: Enhancements for Higher Throughput, Clause 20. High Throughput PHY specification ”.

In IEEE 802.11n, 8 bits are allocated to the HT-SIG field for CRC check, and bits 0-33 (0-23 is the HT-SIG1 field and 0-9 are the HT-SIG2 field) out of a total of 48 bits. It is designed to be protected. The CRC operation sets the shift register to its initial value, passes through the input bits in turn, calculates and outputs the bits remaining in the transition register after the last bit is entered and all operations are over. To get For example, if (m0… m33) = {1 1 1 1 0 0 0 1 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0} the CRC bit {c7 … c0} = {1 0 1 0 1 0 0 0}.

When the HT STA detects the HT-SIG field of the HT mixed PLCP frame, two operations are possible in addition to the mode in which the HT-SIG field is normally read and operated. The HT STA recognizes that it is not an HT-SIG field and operates in legacy mode, or recognizes it as an HT-SIG field, but when an error is detected as a result of CRC execution, PHY-RXSTART.indication is not transmitted and PHY-RXEDN.indication (Format Violation informs the CRC error, where the HT PHY stage uses a specific CCA sensitivity level (eg, Energy Detection Threshold), which means that the received level is an idle channel. Keep PHY-CCA.indication (BUSY, channel-list) until it falls below)).

In each OFDM symbol of the 20 MHz channel of IEEE 802.11n, four subcarriers are composed of pilot signals, which are robust to frequency offset and phase noise. For coherent detection. The pilot is modulated with a BPSK constellation and is located at indexes -21, -7, 7, 21, and {0,0, ..., 0,1, 0, ..., 0,1, 0, ..., 0, 1, 0, ..., 0, -1, 0, ... can be represented by 0}. Meanwhile, the pilot subcarrier is scrambled by the sequence Pn.

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. Very High Throughput (VHT) WLAN system is one of the recently proposed IEEE 802.11 WLAN system to support the data processing speed of 1Gbps or more.

IEEE 802.11 TGac, which is progressing standardization of VHT WLAN system, uses 4X4 MIMO and 80MHz or higher channel bandwidth to provide 1Gbps or more throughput, and legacy STA, HT STA, and VHT STA coexist. Research into a PLCP format for efficiently supporting each STA in a WLAN system is being conducted. In order to improve the performance of the newly introduced MU-MIMO in the SU-MIMO and VHT wireless LAN system introduced in IEEE 802.11n, it effectively supports the SU-MIMO mode and the MU-MIMO mode and prevents malfunction of legacy STA and HT STA. Consideration should be given to a method of configuring a PLCP frame format that can prevent and guarantee coexistence and a wireless device supporting the same.

An object of the present invention is to improve the performance of SU-MIMO in a WLAN system in which legacy STAs, HT STAs, and VHT STAs coexist, and to provide a method for configuring a PLCP frame supporting MU-MIMO and an apparatus supporting the same.

Another problem to be solved by the present invention is a PLCP frame format capable of preventing malfunction of the HT STA while reducing preamble overhead in a WLAN system in which legacy STAs, HT STAs, and VHT STAs coexist. To provide.

PLCP frame configuration method according to the present invention generates an MPDU (MAC Protocol Data Unit) to be transmitted to the destination STA (station, STA), the control information for the L-SIG field and VHT STA containing the control information for the legacy STA in the MPDU Generating a PPDU (PLCP Protocol Data Unit) by attaching a physical layer convergence procedure (PLCP) header including a VHT-SIG field, and transmitting the PPDU to the destination station, wherein the OFDM symbol of the VHT-SIG field is included. The constellation applied to is characterized in that the constellation obtained by rotating the constellation applied to the OFDM symbol of the L-SIG field.

According to an embodiment of the present invention, it is possible to effectively support SU-MIMO and MU-MIMO, reduce preamble overhead, and prevent malfunction of legacy STA and HT STA, thereby ensuring coexistence of VHT STA, legacy STA, and HT STA.

1 is a diagram illustrating a physical layer architecture of IEEE 802.11.
FIG. 2 is a block diagram illustrating an example of a VHT mixed PLCP frame format supporting SU-MIMO in a WLAN system in which L-STA, HT-STA, and VHT-STA coexist.
3 is a block diagram illustrating an example of a VHT mixed PLCP frame format supporting MU-MIMO in a WLAN system in which L-STA, HT-STA, and VHT-STA coexist.
4 is a diagram showing an example of the properties that can be used in the constellations used in the L-SIG field, HT-SIG field and the VHT-SIG field proposed in the present invention, respectively.
FIG. 5 is a diagram showing another example of the properties used in the L-SIG field and the HT-SIG field and the properties used in the VHT-SIG field proposed by the present invention.
6 is a block diagram illustrating a VHT mixed PLCP frame format supporting SU-MIMO according to an embodiment of the present invention.
7 is a block diagram illustrating a VHT mixed PLCP frame format supporting MU-MIMO according to an embodiment of the present invention.
8 is an example of a constellation for a symbol and a pilot for a symbol of each field of a PLCP frame according to an embodiment of the present invention.
9 is a block diagram illustrating a wireless device in which an embodiment of the present invention is implemented.

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

A wireless local area network (WLAN) system in which an embodiment of the present invention is implemented includes at least one basic service set (BSS). A BSS is a collection of stations (STAs) that have been successfully synchronized to communicate with each other. BSS can be classified into Independent BSS (IBSS) and Infrastructure BSS.

The BSS includes at least one STA and an access point (AP). The AP is a functional medium that provides a connection through a wireless medium for each STA in the BSS. The AP may be called another name such as a centralized controller, a base station (BS), a scheduler, and the like.

A STA is any functional medium that includes a medium access control (MAC) and a wireless-medium physical layer (PHY) interface that meets the IEEE 802.11 standard. The STA may be an AP or a non-AP STA, but refers to a non-AP STA unless otherwise indicated below. The STA may be called other names such as user equipment (UE), mobile station (MS), mobile terminal (MT), portable device, interface card, and the like.

STA may be classified into VHT-STA, HT-STA and L (Legacy) -STA. HT-STA refers to an STA that supports IEEE 802.11n, and L-STA refers to a STA that supports a lower version of IEEE 802.11n, for example, IEEE 802.11a / b / g. L-STA is also called non-HT STA.

1 is a diagram illustrating a physical layer architecture of IEEE 802.11.

The PHY layer architecture of the IEEE 802.11 is composed of 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 11 transmits the MAC Protocol Data Unit (MPDU) received from the MAC sublayer 120 between the MAC sublayer 120 and the PMD sublayer 100 according to the indication of the MAC layer 120. Or a frame coming from the PMD sublayer 100 to the MAC sublayer 120. The PMD sublayer 100 is a lower layer of the PLCP to enable transmission and reception of physical layer entities between two stations through a wireless medium.

The PLCP sublayer 110 adds an additional field including information required by the physical layer transceiver in the process of receiving the MPDU 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 on the data field. The PLCP preamble serves to prepare the receiver for synchronization and antenna diversity before the PSDU (PLCP Service Data Unit = MPDU) is transmitted. The PLCP header includes a field including information on the frame, which will be described in detail later with reference to FIG. 2.

The PLCP sublayer 110 adds the above-mentioned fields to the MPDU to generate a PPDU (PLCP Protocol Data Unit) and transmits it to the receiving station via the PMD sublayer, and the receiving station receives the PPDU to receive data from the PLCP preamble and PLCP header. Restore the data by obtaining the information necessary for restoration.

FIG. 2 is a block diagram illustrating an example of a VHT mixed PLCP frame format supporting SU-MIMO in a WLAN system in which L-STA, HT-STA, and VHT-STA coexist.

The VHT mixed PLCP frame includes L-STF field 210, L-LTF field 220, L-SIG field 230, HT-SIG field 240, VHT-SIG field 250, VHT STF field 260. ), A Data VHT-LTF field 270, an extension VHT-LTF field 280, and a data field 290.

In the PLCP sublayer, the necessary information is added to the MPDU received from the MAC layer and converted into data 290 of FIG. 2, and the L-STF field 210, L-LTF field 220, L-SIG field 230, and HT -Add fields such as SIG field 240, VHT-SIG field 250, VHT STF field 260, Data VHT-LTF field 270, extension VHT-LTF field 280, etc. Generate 200 and transmit to one or more STAs through the PMD layer.

The L-STF field 210 is used for frame timing acquisition, automatic gain control (AGC) control, coarse frequency acquisition, and the like.

The L-LTF field 220 is used for channel estimation for demodulation of the L-SIG field 230, the HT-SIG field 240, and the VHT-SIG field 250.

The VHT-SIG field 250 is transmitted without being beamformed so that all STAs including the L-STA can be received and recognized, and the VHT STF field 260 and Data VHT- transmitted after the VHT-SIG field 250. The LTF field 270, the extended VHT-LTF field 280, and the data field 290 may be beamformed and transmitted through precoding.

The VHT-STF field 260 is used by the VHT-STA to improve the AGC estimation and allow the receiving STA to consider a portion in which transmission power due to precoding is variable.

The Data VHT-LTF field 270 is configured in plural and used for channel estimation for demodulation of the data field 290. Additionally, an extended VHT-LTF field 280 for channel sounding may be used.

Short training field (STF) fields, such as the L-STF field 210 and the VHT STF field 260, are also referred to as sync signals or sync channels because they are used for frame timing acquisition, automatic gain control (AGC) control, and the like. . That is, STF is used to synchronize synchronization between STAs or between STAs and APs.

Long training fields, such as the L-LTF field 220 and the Data VHT LTF field 270, are used for channel estimation for demodulation of data and / or control information. Also called a pilot.

The L-SIG field 230, the HT-SIG field 240, and the VHT-SIG field 250 are also referred to as control information because they provide various information necessary for demodulation and decoding of data.

The VHTSIG field 250 may include at least one of the fields of Table 1, for example.

Field name Explanation MU-MIMO indicator Indicates whether MU-MIMO is used. Alternatively, you can toggle the SU-MIMO / MU-MIMO. Bandwidth Indicates the bandwidth of the channel VHT Length Number of data octets in the PSDU STA indicator Indicates the STA to receive. Indicates the STA's address or indicates the STA's identification information, such as the AID of the STA Multiplex count Number of STAs (or users) multiplexed with MU-MIMO Decoding indicator Indicates information for decoding data. MCS Represents MCS (modulation and coding scheme) information required to decode data Short gi Indication of whether to use short GI (short guard interval) Number of spatial streams added The number of extension spatial streams CRC Check value to check if there is an error in the transmitted data Tail Bits Used to terminate the trellis of the convolution coder

In Table 1, the field names are merely examples and other names may be used. Fields in Table 1 are merely examples, some fields may be omitted, and other fields may be added. In addition, the PPDU frame according to the PPDU frame format illustrated in FIG. 2 is generated in the PLCP sublayer of the STA and transmitted to the transmission target STA through the PMD sublayer. Some fields of the PPDU frame of FIG. 2 may be omitted or added as necessary.

3 is a block diagram illustrating an example of a VHT mixed PLCP frame format supporting MU-MIMO in a WLAN system in which L-STA, HT-STA, and VHT-STA coexist.

The VHT mixed PLCP frame includes an L-STF 310, an L-LTF 320, an L-SIG field 330, an HT-SIG field 340, a plurality of VHT-SIG fields 350, and a VHT STF 360. , Data VHT-LTF 370, extension VHT-LTF 380, and data 390.

The function of each field is the same as in FIG. However, the VHT mixed PLCP frame format of FIG. 3 supporting MU-MIMO for simultaneously transmitting data to a plurality of destination STAs has a plurality of VHT-SIG fields 350.

3 illustrates a case in which the AP performs MU-MIMO transmission to STA1 and STA2. In FIG. 3, two VHT-SIG fields are included, and the VHT-SIG1 field 350-1 and the VHT-SIG2 field 350-2 include control information for STA1 and STA2, respectively. That is, a PLCP frame format supporting MU-MIMO may have as many VHT-SIG fields as the number of target STAs.

In addition, in FIG. 3, the AP transmits data to STA 1 using three spatial streams, and transmits data to STA 2 using two spatial streams. The case of using all five spatial streams is illustrated. In this case, each spatial stream may have a VHT-LTF. Therefore, in FIG. 3, the Data VHT-LTF 370 may include five VHT-LTFs.

As can be seen in the VHT mixed PLCP frame structure illustrated in FIGS. 2 and 3, the L-SIG field and the L-SIG field for the L-STA in order to support backward compatibility with the L-STA and the HT-STA, and The HT-SIG field for the HT-STA is transmitted first before the VHT-SIG field for the VHT-STA.

At this time, when the operation of each STA, the L-STA reads the L-SIG field from the received PLCP frame and assumes that the data packet is its own data packet. However, since the L-STA received the PLCP frame transmitted in the data format for the HT STA including the HT-SIG field and not the data that the L-STA can accept (recognition), it is assumed that the format for the L-STA When CRC checks the result of demodulation and decoding, an error occurs. The same may occur in the case of the HT-STA, but as in the case of the L-STA, it is determined that the L-SIG field and the HT-SIG field are read and data is transmitted in a format for the HT STA, thereby the HT-SIG The field after the VHT-SIG field, which is transmitted after the field, is recognized as HT-LTF, and received, demodulated and decoded, resulting in an error in the CRC check.

As described above, in order to satisfy backward compatibility, continuously transmitting three SIG fields (L-SIG field, HT-SIG field, and VHT-SIG field) in a VHT mixed PLCP frame increases preamble overhead. It is not preferable in that it is made. In order to reduce the preamble overhead, if the three SIG fields are not transmitted continuously and the HT-SIG field of the three SIG fields is not transmitted (i.e., only the L-SIG field and the VHT-SIG field are transmitted), 8 ㎲ preamble over Reduce head In this case, if the HT-SIG field including the control information for the HT-STA is not transmitted in order to reduce the preamble overhead, the HT-STA may malfunction.

 VHT that allows HT-STA to recognize VHT mixed PLCP frame that transmits only L-SIG field and VHT-SIG field without HT-SIG field and recognizes that it is not its own data packet without malfunction. We propose a composition and field setting method for a mixed PLCP frame.

According to an embodiment of the VHT mixed PLCP frame configuration and field setting method proposed by the present invention, when the HT-STA performs a CRC check on the CRC bits included in the VHT-SIG field, a CRC error is returned. Set to get.

For example, CRC polynomial used for CRC check is set differently from CRC polynomial of HT-SIG field, and CRC bits included in VHT-SIG field by CRC calculation based on CRC polynomial set otherwise. Determine the value of (bits).

The AP transmits a PLCP frame including an L-SIG field and a VHT-SIG field in which the HT-SIG field is omitted. In this case, CRC bits obtained based on the new CRC polynomial may be included in the VHT-SIG field as a subfield. The HT-STA receiving the VHT mixed PLCP frame omitting the HT-SIG field according to an embodiment of the present invention performs a CRC check based on a conventional CRC polynomial used in the HT-STA and obtains a result of a CRC error. It can be seen that the data is not in the format for HT-STA.

According to another embodiment of the present invention, when the HT-STA receiving the VHT mixed PLCP frame performs a CRC check, a CRC polynomial for CRC check of the HT-SIG field is used. CRC parity bits are subjected to an exclusive OR (XOR) operation with a particular bit pattern (hereinafter referred to as 'CRC masking') to obtain the CRC bits of the VHT-SIG field. The VHT-SIG field including CRC bits obtained through CRC masking causes a CRC error to the HT-STA, but the VHT-STA may operate normally.

In this case, an ID capable of identifying an STA such as an association ID (AID) or an STA ID of the VHT-STA may be used as a specific bit pattern XORed to the CRC parity bits. Since the HT-STA receiving the VHT-SIG field including the CRC bits obtained by CRC masking the AID does not know whether to mask the CRC, the HT-STA recognizes it as a simple CRC error and knows that the data is not in the format for the HT-STA. .

According to another embodiment of the present invention, the VHT-SIG field is set so that the HT-STA receiving the VHT-SIG field is recognized and operated as a data format for the L-STA.

The method for setting the VHT-SIG field according to an embodiment of the present invention newly defines and uses a property for the VHT-SIG field so that the HT-STA receiving the VHT-SIG field is recognized and operated as a data format for the L-STA. do.

4 is a diagram showing an example of the properties that can be used in the constellations used in the L-SIG field, HT-SIG field and the VHT-SIG field proposed in the present invention, respectively.

Referring to FIG. 4, the L-STA reads the L-SIG field 410 composed of one 4㎲ SIG field, and the HT-STA reads the 4㎲ HT-SIG1 field 420-1 and 4㎲ HT-SIG2 field ( Read HT-SIG field 420 composed of 420-2. As shown in FIG. 4, the constellation used in the L-SIG field 410 is BPSK, and the HT-SIG1 field 420-1 and HT-SIG2 field 420-2, which are 24-bits respectively, are the same QBPSK (quadrature BPSK). It is modulated.

The constellation 430 of the VHT-SIG field of FIG. 4 is an example of the constitution of the VHT-SIG field according to the embodiment of the present invention. The VHT-SIG field 430 according to the embodiment of the present invention may be composed of a VHT-SIG1 field 430-1 and a VHT-SIG2 field 430-2. A modulation scheme applied to the VHT-SIG field may be BPSK, but may be transmitted in a combination of different rotated BPSK constellations for each VHT-SIG OFDM symbol.

The example of FIG. 4 is a BPSK constellation rotated 90 degrees with the constellation of the first OFDM symbol VHT-SIG1 430-1 in the VHT-SIG field 430 and the constellation of the second OFDM symbol VHT-SIG2 430-2. This is an example of applying. Using this feature, the HT-STA reads the VHT-SIG field and does not recognize it as an HT-SIG field. In order for the HT-STA to recognize the VHT-SIG field as the HT-SIG field, the VHT-SIG1 430-1 and the VHT-SIG2 430-2 are modulated by QBPSK, or the VHT according to an example of an STA implementation method. This is because at least the VHT-SIG1 430-1 should be modulated by QBPSK even if it is determined whether the SHT1 430-1 is the HT-SIG field. However, since the VHT-STA already knows whether the constellation is rotated and the degree of rotation, it can be seen that the received PLCP frame format is for the VHT-STA through the rotation of the constellation of the VHT-SIG2 430-2.

FIG. 5 is a diagram showing another example of the properties used in the L-SIG field and the HT-SIG field and the properties used in the VHT-SIG field proposed by the present invention.

In the VHT WLAN system, the control information bits required to support QPSK, 16QAM, 64QAM, 256QAM and 8 or more spatial streams may be larger than 48 bits. In order to maximize the transmission coverage of the control information, three OFDM symbols (20MHz, 24) in case of taking 1/2 code-rate channel encoding applied to the HT-SIG field When using subcarriers). In this case, the VHT-SIG field 530 may include three OFDM symbols VHT-SIG1 530-1, VHT-SIG2 530-2, and VHT-SIG3 530-3.

As in the example of FIG. 4, a modulation scheme applied to the VHT-SIG field 530 may be BPSK, but may be transmitted in a combination of different rotated BPSK constellations for each VHT-SIG OFDM symbol. The degree of rotation can be different angles for each symbol, some of which can be the same value. In the example of FIG. 5, the BHTK is applied to the VHT-SIG1 530-1 and the VHT-SIG2 530-2, and the QBPSK is applied to the VHT-SIG3 530-3. Since the VHT-SIG1 530-1 and the VHT-SIG2 530-2 are not modulated by QBPSK, the HT-STA is not recognized as a PLCP frame format for the HT-STA. However, since the VHT-STA already knows whether the constellation has been rotated and the degree of rotation, the PLCP frame format that has been received through the rotation of the constellations of the VHT-SIG2 (530-2) and / or VHT-SIG3 (530-3) It can be seen that the format for the VHT-STA.

6 and 7 are block diagrams illustrating a VHT mixed PLCP frame format supporting SU-MIMO and a VHT mixed PLCP frame format supporting MU-MIMO according to an embodiment of the present invention, respectively.

In the VHT mixed PLCP frame format of FIG. 6, unlike the VHT mixed PLCP frame format of FIG. 2, the HT-SIG field is omitted between the L-SIG field 630 and the VHT-SIG field 650. Unlike the VHT mixed PLCP frame format of FIG. 7, the HT-SIG field is omitted between the L-SIG field 730 and the VHT-SIG field 750.

The possibility of malfunction of the HT-STA receiving the VHT mixed PLCP frame in which the HT-SIG field is omitted according to an embodiment of the present invention may be caused by a method of causing a CRC error by setting the CRC bit included in the above-described VHT-SIG field. This can be solved by configuring the VHT-SIG field with a combination of rotated BPSK constellations. Each method can be used independently or can be applied together.

The method of constructing the VHT-SIG field with a combination of rotated BPSK constellations is to construct a VHT-SIG symbol using two or three BPSK constellations for L-STA as it is, or the first VHT-SIG symbol VHT-SIG1. Is maintained in the constellation BPSK of the L-SIG field, and then the symbols of the transmitted VHT-SIG2 (VHT-SIG2 and VHT-SIG3, if composed of three symbols) are constructed using the rotated L-SIG constellation (BPSK constellation). Do it. When the HT-STA receives a VHT mixed PLCP frame in which the HT-SIG field of the format shown in FIG. 6 or 7 is omitted, the first VHT-SIG symbol VHT SIG1 must be maintained in the shape of the L-SIG in order to prevent malfunction. Because. In this case, the first VHT-SIG symbol VHT SIG1 may use the constellation of rotating the constellation of L-SIG by 180º. In this case, the HT-STA does not support the L-STA because the constellation of the symbol is not rotated by 90º. This is because it can judge and operate with PLCP frame format.

According to another embodiment of the present invention, a malfunction of the HT-STA may be prevented by using a pilot included in the OFDM symbol of the VHT-SIG field. The VHT-STA may use the pilot to classify the SIG field, or the pilot may be used to classify the SIG field together with whether the symbol configuration of the SIG field is rotated.

In each OFDM symbol of a channel having a bandwidth of 20MHz, four subcarriers are composed of pilot signals, which may be modulated with a BPSK constellation and located at indices -21, -7, 7, and 21.

심볼 및

시공간 스트림(space time stream, STS)에 대한 파일럿 시퀀스를 나타낸다. 여기에서 n은 심볼번호(number)를

는 모둘로(modulo) 연산자를 의미하며,

는 n을 a로 나눈 나머지 값을 의미한다. 파일럿의 패턴

는 표 2와 같이 정의된다.Equation 1 is

Symbol and

Represents a pilot sequence for a space time stream (STS). Where n is the symbol number

Means the modulo operator,

Is the remainder of n divided by a. Pattern of pilot

Is defined as shown in Table 2.

According to the embodiment of the present invention, when the BPSK constellation used for the pilot is applied to the pilot for the VHT SIG field, the constitution is applied as the rotated BPSK constellation. For example, the VHT-SIG field can be used by applying a 180 ° rotated BPSK constellation. The degree of rotation may be set in various ways, and the present invention is not limited by the degree of rotation and the number of pilot signals included in each OFDM symbol. Hereinafter, an OFDM symbol in a channel having a bandwidth of 20 MHz including four pilot signals will be described as an example. However, the technical idea of the present invention is that 40 or 80 MHz in which six or more subcarriers are composed of subcarriers including a pilot signal in an OFDM symbol. The same applies to the case of using a channel having a channel bandwidth of 80 MHz or more.

According to an embodiment, a pilot of one of the symbols constituting the SIG field may be used to allow the receiving STA to know the type of the SIG field, and more precisely, using a pilot of two or three symbols constituting the SIG field. You can also tell the type of the SIG field.

A method for distinguishing types of SIG fields using pilots according to an embodiment of the present invention may be performed as follows.

In the case of using the BPSK constellation rotated by 180 ° with the constellation applied to the pilot according to an embodiment of the present invention, it is possible to express the pilot in two ways.

The first method is to rotate the pilot itself by 180º. The rotated pilot proposed by the present invention is {0,0,... , 0, -1,0,… , 0, -1,0,… , 0, -1,0,… , 0,1,0,… , 0} can be used. This is because the pilot values located at indexes -21, -7, 7 and 21 have been changed from 1 to -1 and -1 to 1, which is the result of rotating the pilot itself by 180º.

The second method is to rotate the scrambling sequence by 180 °, and scrambling using a 180 ° rotated scrambling sequence obtained by multiplying the scrambling sequence by −1.

The received STA may use the correlation of each pilot or the phase difference between the LTF field and the pilot as a method of distinguishing the SIG field by using a pilot of the OFDM symbol.

8 is an example of a constellation for a symbol and a pilot for a symbol of each field of a PLCP frame according to an embodiment of the present invention.

8 illustrates another embodiment of the present invention described with reference to FIG. 4, and the symbol constellation 855-1 of the VHT-SIG1 850-1 uses the constellation 835 of the L-SIG 850 as it is. The symbol constellation 855-2 of the VHT-SIG2 850-2 shows an example of rotating and using the constellation 855 of the L-SIG 850.

The pilot of the present invention exists in the SIG field and the data field. In describing the pilot sequence in FIG. 8, {0,0,... , 0,1,0,… , 0,1,0,… , 0,1,0,… , 0, -1,0,… , 0} is {… ,One,… ,One,… , 1, -1,… } In the form of omitting zero, it is simply expressed by only pilot values located at indexes -21, -7, 7 and 21.

Compared to the pilot constellation 837 of the L-SIG field 830, the pilot constellation 857-1 of the VHT SIG1 850-1 and the constellation 857-2 of the VHT SIG2 850-2 symbol are 180 degrees. You can see that it is rotated.

The HT-STA receiving the VHT mixed PCLP frame as shown in the example of FIG. 8 is a PLCP frame received from the constellation 835 of the L-SIG field 830 and the constellation 855-1 of the VHT-SIG1 850-1. It can operate by recognizing the format as a frame format supporting L-STA. In addition, the pilot constellation 857-1 of the VHT SIG1 (850-1) rotated 180 degrees and the constellation 857-2 of the VHT SIG2 (850-2) symbol are not PLCP frame formats for the HT-STA. You can also recognize it.

9 is a block diagram illustrating a wireless device in which an embodiment of the present invention is implemented. The wireless device 900 may be a non-AP STA or part of an AP.

The wireless device 900 includes a frame generator 910 and a frame transmitter 920. The frame generator 910 generates a VHT mixed PLCP frame according to the above-described embodiment. In this case, the CRC bit of the VHTSIG field included in the PLCP header of the VHT mixed PLCP frame may be set so that the HT-STA receiving the error causes an error as a result of the CRC check, and the properties and / or pilot of the VHT-SIG field may be described in the above-described method. Can be set. The frame transmitter 920 transmits the generated VHT mixed PLCP frame to one or more wireless devices.

The frame generator 910 and the frame transmitter 920 may be implemented as one chip in the form of a processor. An embodiment of generating a frame may be configured as a software module, stored in a memory, and executed by a processor.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (9)

In the method of configuring a physical layer convergence procedure (PLCP) frame in a VHT (Very High Throughput) wireless LAN system,
Generate a MAC Protocol Data Unit (MPDU) to be sent to a destination STA (STA);
A PPDU (PLCP Protocol Data Unit) is generated by attaching a physical layer convergence procedure (PLCP) header including a L-SIG field containing control information for a legacy STA and a VHT-SIG field containing control information for a VHT STA to the MPDU. and; And
Transmitting the PPDU to the destination station;
The constellation applied to the OFDM symbol of the VHT-SIG field is a constellation obtained by rotating the constellation applied to the OFDM symbol of the L-SIG field. The method of claim 1,
The L-SIG field is transmitted in one OFDM symbol, and the OFDM symbol of the L-SIG field is mapped to a BPSK constellation. The method of claim 1,
The OFDM symbol of the VHT-SIG field is composed of two OFDM symbols of VHT-SIG1 and VHT-SIG2,
The VHT-SIG1 is modulated in the same manner and shape as the OFDM symbol of the L-SIG field. The method of claim 1,
The OFDM symbol of the VHT-SIG field is composed of three OFDM symbols of VHT-SIG1, VHT-SIG2, and VHT-SIG3,
The VHT-SIG1 is modulated in the same manner and shape as the OFDM symbol of the L-SIG field. The method of claim 1,
The OFDM symbol of the VHT-SIG field includes a VHT pilot signal,
The VHT pilot signal is mapped to a constellation obtained by rotating the constellation applied to the pilot signal included in the OFDM symbol of the L-SIG field. 6. The method of claim 5,
The pilot signal included in the OFDM symbol of the L-SIG field is mapped to the BPSK constellation. The method of claim 6,
Wherein the VHT pilot signal is mapped to a 180 ° rotated BPSK constellation. In the method of configuring a physical layer convergence procedure (PLCP) frame in a VHT (Very High Throughput) wireless LAN system,
Generate a MAC Protocol Data Unit (MPDU) to be sent to a destination STA (STA);
A PPDU (PLCP Protocol Data Unit) is generated by attaching a physical layer convergence procedure (PLCP) header including a L-SIG field containing control information for a legacy STA and a VHT-SIG field containing control information for a VHT STA to the MPDU. and; And
Transmitting the PPDU to the destination station;
The L-CRC bit string included in the L-SIG field and the VHT-CRC bit string included in the VHT-SIG field used for the cyclic redundancy check (CRC) of the target STA are obtained based on different CRC polynomials. How to feature. A frame generation unit generating a PPDU to be transmitted to the destination STA, and
Including a frame transmitting unit for transmitting the PPDU to the destination STA,
The PLCP header of the PPDU includes a VHT-SIG field containing control information for the VHT STA.
The constellation applied to the OFDM symbol of the VHT-SIG field is a constellation obtained by rotating the BPSK constellation.

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