KR101824093B1 - Apparatus and method of indicating bandwidth in wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for indicating bandwidth in a wireless communication system. The present disclosure includes a transceiver for transmitting and receiving a wireless signal, and a processor operatively coupled to the transceiver, wherein the processor is configured to perform phase rotation < RTI ID = 0.0 > (PPDU) to which the application of the PPDU is selectively applied.

Description

[0001] APPARATUS AND METHOD OF INDICATING BANDWIDTH IN WIRELESS COMMUNICATION SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to an apparatus and method for indicating a bandwidth in a wireless communication system.

Dynamic bandwidth allocation is newly introduced in IEEE 802.11ac for adaptive preparation of frequency selective disturbances of homogeneous and heterogeneous interfering signals in wireless LAN networks and for efficient use of frequency resources. Dynamic bandwidth allocation is a function of the VHT STA and can be defined as the exchange of RTS / CTS negotiating a channel width that is potentially reduced compared to the channel width indicated by the RTS. However, in the dynamic bandwidth allocation, there is a problem that a peak to average power ratio (PAPR) of the SIG occurs, and a solution is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for indicating a bandwidth in a wireless communication system.

According to an aspect of the present invention there is provided a transceiver comprising a transceiver for transmitting and receiving a radio signal, a processor operatively associated with the transceiver, And a physical protocol data unit (PPDU) to which the application of rotation is selectively applied.

Here, in the case of a bandwidth indication, the processor can generate the PPDU to which the application of the phase rotation is not applied based on a TXVECTOR parameter indicating a bandwidth exchange (BW_EXCHANGE).

The processor may also generate a SIG field that includes a one-bit DYN_BANDWIDTH indicating that the bandwidth indication is dynamic or static.

According to another aspect of the present invention, there is provided a method of performing bandwidth indication by a wireless device in a wireless LAN system. The method includes generating a physical protocol data unit (PPDU) selectively applying the application of phase rotation in the case of a bandwidth indication and in the case of a bandwidth indication, and transmitting the PPDU.

Here, in the case of the bandwidth indication, the PPDU to which the application of the phase rotation is not applied may be generated based on the TXVECTOR parameter indicating the bandwidth exchange (BW_EXCHANGE).

The method may further comprise generating a SIG field including a one-bit DYN_BANDWIDTH indicating that the bandwidth indication is dynamic or static.

Conventionally, using the bandwidth information already defined in the preamble, the phase rotation can be selectively allowed in the dynamic bandwidth allocation (or the dynamic frequency allocation), thereby solving the problem of uniformly applying the phase rotation as before.

1 is a diagram illustrating a configuration of a wireless local area network (WLAN) system to which an embodiment of the present invention can be applied.
2 is a diagram illustrating a physical layer architecture of a wireless LAN system supported by IEEE 802.11.
3 and 4 are block diagrams illustrating a format of a PPDU used in a wireless local area network (LAN) system to which the embodiment of the present invention can be applied.
5 is a diagram for explaining a dynamic bandwidth indication.
6 is a diagram illustrating a method for performing scrambling of data in an 802.11ac.
7 is a block diagram illustrating a wireless device in which embodiments of the present invention may be implemented.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

The present invention will be described with reference to a communication network. The work performed in the communication network may be performed in a process of controlling the network and transmitting data by a system (e.g., a base station) that manages the communication network, The work can be done.

1 is a diagram illustrating a configuration of a wireless local area network (WLAN) system to which an embodiment of the present invention can be applied.

Referring to FIG. 1, a WLAN system includes one or more Basic Service Sets (BSSs). BSS is a set of stations (STAs) that can synchronize successfully and communicate with each other,

The infrastructure BSS may include one or more non-AP stations (non-AP STA1 21, non-AP STA2 22, non-AP STA3 23, non-AP STA4 24, (STAa 30), an access point (AP) 10 for providing a distribution service, and a distribution system (DS) for connecting a plurality of APs. In the infrastructure BSS, the AP manages the non-AP STAs of the BSS.

On the other hand, an independent BSS (IBSS) is a BSS operating in an ad-hoc mode. Since the IBSS does not include APs, there is no centralized management entity in the center. That is, non-AP STAs are managed in a distributed manner in the IBSS. In the IBSS, all STAs can be made as mobile STAs, and self-contained networks are established because access to the DS is not allowed.

The STA is an arbitrary functional medium including a medium access control (MAC) conforming to IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard and a physical layer interface for a wireless medium. It includes both an AP and a non-AP station.

The non-AP STA is a non-AP STA, the non-AP STA is a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE) May also be referred to as another name, such as a mobile station (MS), a mobile subscriber unit, or simply a user. Hereinafter, non-AP STA will be referred to as STA for convenience of explanation.

An AP is a functional entity that provides access to a DS via wireless media for an associated STA to the AP. Communication between STAs in an infrastructure BSS including an AP is performed via an AP, but direct communication is also possible between STAs when a direct link is established. The AP may be referred to as a central controller, a base station (BS), a node-B, a base transceiver system (BTS), a site controller or a management STA.

A plurality of infrastructure BSSs including the BSS shown in FIG. 1 may be interconnected through a distribution system (DS). A plurality of BSSs connected through a DS is referred to as an extended service set (ESS). The APs and / or STAs included in the ESS can communicate with each other, and the STA can move from one BSS to another BSS while continuing to communicate in the same ESS.

In a wireless LAN system according to IEEE 802.11, the basic access mechanism of Medium Access Control (MAC) is a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism is also referred to as the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC, which basically employs a "listen before talk" access mechanism. According to this type of connection mechanism, the AP and / or STA senses a wireless channel or medium prior to initiating a transmission. As a result of sensing, if it is determined that the medium is in the idle status, the frame transmission is started through the medium. On the other hand, if it is detected that the medium is occupied, the AP and / or STA sets a delay period for medium access without waiting to start its own transmission.

The CSMA / CA mechanism also includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly senses the media. Virtual carrier sensing is intended to compensate for problems that may arise from media access, such as hidden node problems. For the virtual carrier sensing, the MAC of the wireless LAN system uses a network allocation vector (NAV). The NAV is a value indicating to another AP and / or the STA that the AP and / or the STA that is currently using or authorized to use the medium has remaining time until the media becomes available. Therefore, the value set to NAV corresponds to the period in which the medium is scheduled to be used by the AP and / or the STA that transmits the frame.

In addition to DCF, the IEEE 802.11 MAC protocol is a DCF and pollination-based, synchronous access scheme that uses an HCF (Point Coordination Function) that periodically polls all receiving APs and / or STAs to receive data packets. (Hybrid Coordination Function). The HCF is a protocol that allows a provider to provide data packets to a large number of users using a competing based EDCA (Enhanced Distributed Channel Access) and a non-contention based channel approach using a polling mechanism (HCCA Access). The HCF includes a medium access mechanism for improving QoS (Quality of Service) of a wireless LAN and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).

In the wireless communication system, the presence of the network is not immediately known when the STA is powered on and starts operating due to the nature of the wireless medium. Therefore, any type of STA must perform a network discovery process in order to access the network. The STA that detects the network through the network discovery process selects the network to join through the network selection process. Thereafter, the mobile station joins the selected network and performs a data exchange operation in the transmission / reception stage.

In the wireless LAN system, the network discovery process is implemented by a scanning procedure. The scanning procedure is divided into passive scanning and active scanning. Manual scanning is based on a beacon frame in which the AP periodically broadcasts. Generally, an AP in a wireless LAN broadcasts a beacon frame every predetermined interval (for example, 100 msec). The beacon frame contains information about the BSS that it manages. The STA manually waits for a beacon frame to be received on a particular channel. The STA that has acquired the information about the network through the reception of the beacon frame terminates the scanning procedure in the specific channel. Manual scanning is advantageous in that the overall overhead is small since the STA only needs to receive a beacon frame without having to transmit a separate frame. However, there is a disadvantage in that the scanning execution time is increased in proportion to the transmission period of the beacon frame.

In active scanning, the STA actively broadcasts a probe request frame on a specific channel and requests network information from all the APs that receive the probe request frame. After receiving the probe request frame, the AP transmits a network response to the probe response frame after waiting for a random time to prevent frame collision. The STA terminates the scanning procedure by receiving the probe response frame and obtaining the network information. Active scanning has the advantage that scanning can be completed in a relatively short time. On the other hand, since the frame sequence according to the request-response is required, the overall network overhead increases.

After completing the scanning procedure, the STA selects a network according to a specific criterion for itself and performs an authentication procedure with the AP. The authentication procedure consists of a two-way handshake. After completing the authentication procedure, the STA proceeds with the association process with the AP.

The combining procedure consists of a two-way handshake. First, the STA sends an association request frame to the AP. The association request frame includes capability information of the STA. Based on this, the AP determines whether the STA can be combined. The AP which has decided whether to allow the association transmits an association response frame to the corresponding STA. The association response frame includes information indicating whether or not to permit the association and information indicating the reason for the combination permission / failure. The association response frame further includes information on the capability values that the AP can support. If the association is successfully completed, a normal frame exchange is performed between the AP and the STA. If the association fails, the association procedure may be retried based on information about the reason for the failure included in the association response frame, or the STA may request the association to another AP.

IEEE 802.11n is a relatively recently established technical standard to overcome the limitation of communication speed which is pointed out as a weak point in wireless LAN. IEEE 802.11n aims to increase the speed and reliability of the network and to extend the operating distance of the wireless network. More specifically, IEEE 802.11n supports high throughput (HT) with data rates of up to 540 Mbps or higher, and uses multiple antennas at both ends of the transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology.

With the spread of wireless LANs and the diversification of applications using them, there is a need for a new wireless LAN system to support higher throughput than the data processing rate supported by IEEE 802.11n. The wireless LAN system supporting Very High Throughput (VHT) is the next version of the IEEE 802.11n wireless LAN system. It has a data processing speed of more than 1Gbps for multiuser in MAC Service Access Point (SAP) And is one of the recently proposed IEEE 802.11 wireless LAN systems to support a throughput of 500 Mbps or higher for a single user.

To support 80MHz continuous 160MHz (contiguous 160MHz), discrete 160MHz (non-contiguous 160MHz) bandwidth transmission and / or higher bandwidth transmission in VHT Wireless LAN system than existing wireless LAN system supporting 20MHz and 40MHz do. In addition, it supports 256QAM more than existing wireless LAN system supporting 64QAM (Quadrature Amplitude Modulation).

Since the VHT wireless LAN system supports an MU-MIMO (Multi User-Multiple Input Multiple Output) transmission method for higher throughput, the AP can simultaneously transmit data frames to at least one STA paired with MIMO. The number of paired STAs can be a maximum of four, and when the maximum number of spatial streams is eight, each STA can be assigned a maximum of four spatial streams.

Referring to FIG. 1 again, in the given WLAN system, the AP 10 includes at least one STA among a plurality of STAs 21, 22, 23, 24, and 30 associated therewith The data can be simultaneously transmitted to the STA group. 1 illustrates an example in which an AP transmits MU-MIMO to STAs. However, in a wireless LAN system supporting TDLS (Tunneled Direct Link Setup), DLS (Direct Link Setup), and mesh network, The STA can transmit the PPDU to a plurality of STAs using the MU-MIMO transmission scheme. Hereinafter, the AP transmits an PPDU to a plurality of STAs according to the MU-MIMO transmission scheme.

Data transmitted to each STA may be transmitted through different spatial streams. The data packet transmitted by the AP 10 may be referred to as a frame as a data field included in a PPDU or PPDU generated and transmitted in the physical layer of the WLAN system. That is, a data field included in a PPDU or PPDU for SU (single user) -MIMO and / or MU-MIMO may be referred to as a MIMO packet. Among them, the PPDU for the MU can be called an MU packet. In the example of the present invention, it is assumed that STA1 21, STA2 22, STA3 23 and STA4 24 are STA groups that are paired with AP 10 and MU-MIMO. At this time, since a spatial stream is not allocated to a specific STA of a transmission target STA group, data may not be transmitted. On the other hand, it is assumed that the STAa 30 is an STA that is coupled to the AP but is not included in the STA group to be transmitted.

In order to support MU-MIMO transmission in an WLAN system, an identifier may be assigned to a STA group to be transmitted, which is referred to as a group identifier (Group ID). The AP transmits a Group ID management frame including group definition information to the STAs supporting the MU-MIMO transmission, and the group ID is transmitted to the STAs supporting the MU-MIMO transmission before the PPDU transmission Lt; / RTI > One STA can be assigned a plurality of group IDs.

Table 1 below shows the information elements included in the group ID management frame.

Order Information One Category 2 VHT Action 3 Membership status 4 User position array

The category field and the VHT action field are set so that the corresponding frame corresponds to a management frame and is a group ID management frame used in a VHT wireless LAN system supporting MU-MIMO.

As shown in Table 1, the group definition information indicates membership status information indicating whether or not it belongs to a specific group ID, and when it belongs to the group ID, the spatial stream set of the STA is located at a certain position in the entire spatial stream according to the MU- And the spatial stream position information indicating whether it is applicable.

Since there are a plurality of group IDs managed by one AP, the membership status information provided to one STA needs to indicate whether each STA belongs to each group ID managed by the AP. Thus, the membership state information may exist in the form of an array of subfields indicating whether or not they belong to each group ID. The spatial stream location information indicates a location for each group ID, and therefore may exist in the form of an array of subfields indicating the location of the spatial stream set occupied by the STA for each group ID. In addition, the membership state information and the spatial stream position information for one group ID can be implemented in one subfield.

When transmitting the PPDU to the plurality of STAs through the MU-MIMO transmission scheme, the AP transmits information indicating the group ID (Group ID) as control information in the PPDU. When the STA receives the PPDU, the STA checks the group ID field to confirm that the STA is the member STA of the STA group to be transmitted. If it is confirmed that the STA group is a member of the STA group to which the STA is to be transmitted, it is possible to confirm how many spatial stream sets transmitted to the STA group are located among the entire spatial streams. Since the PPDU includes information on the number of spatial streams allocated to the receiving STA, the STA can receive data by searching for the spatial streams assigned to the receiving STA.

On the other hand, TV WS (white space) is attracting attention as a frequency band that can be newly used in a wireless LAN system. The TV WS refers to a dormant frequency band remained due to the digitization of analog TV in the United States, for example, a band of 54 to 698 MHz. However, this is merely an example, and the TV WS may be an authorized band that the licensed user can use first. An authorized user means a user who is authorized to use the licensed band, and may also be called another name, such as a licensed device, a primary user, an incumbent user, and so on.

The AP and / or STA operating on the TV WS should provide protection for the authorized user because the user authorized in the use of the TV WS band takes precedence. For example, when an authorized user such as a microphone already uses a specific WS channel, which is a conventionally divided frequency band having a specific bandwidth in the TV WS band, the AP and / Or the STA can not use the frequency band corresponding to that WS channel. In addition, the AP and / or the STA should stop using the frequency band currently used for frame transmission and / or reception when the authorized user uses the frequency band.

Therefore, the AP and / or the STA must precede the procedure of determining whether a specific frequency band in the TV WS band is available, in other words, whether there is a user authorized in the frequency band. Knowing whether or not there is a user authorized in a specific frequency band is called spectrum sensing. The spectrum sensing mechanism uses energy detection method and signature detection method. If the strength of the received signal is equal to or greater than a predetermined value, it is determined that the authorized user is in use, or it is determined that the authorized user is using the DTV preamble when the preamble is detected.

2 is a diagram illustrating a physical layer architecture of a wireless LAN 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 210, and a PMD (Physical Medium Dependent) sublayer 200. PLME provides the management functions of the physical layer in cooperation with the MAC Layer Management Entity (MLME). The PLCP sublayer 210 transmits an MPDU (MAC Protocol Data Unit) received from the MAC sublayer 220 to the PMD sublayer according to an instruction of the MAC layer between the MAC sublayer 220 and the PMD sublayer 200 , And delivers the frame from the PMD sublayer 200 to the MAC sublayer 220. The PMD sublayer 200 enables the transmission / reception of a physical layer entity between two stations via a wireless medium as a PLCP lower layer. The MPDU transmitted from the MAC sublayer 220 is referred to as a physical service data unit (PSDU) in the PLCP sublayer 210. MPDUs are similar to PSDUs, but individual MPDUs and PSDUs can be different when an aggregated MPDU (aggregated MPDU) aggregating multiple MPDUs is delivered.

The PLCP sublayer 210 adds an additional field including information required by the physical layer transceiver in the process of receiving the PSDU from the MAC sublayer 220 and transferring the PSDU to the PMD sublayer 200. In this case, the added field may be a PLCP preamble, a PLCP header, a tail bit for returning the convolutional encoder to a zero state, or the like, to the PSDU. The PLCP sublayer 210 receives a TXVECTOR parameter including control information necessary for generating and transmitting a PPDU and control information necessary for the receiving STA to receive and interpret the PPDU from the MAC sublayer. The PLCP sublayer 210 uses the information included in the TXVECTOR parameter in generating the PPDU including the PSDU.

The PLCP preamble serves to prepare the receiver for the synchronization function and antenna diversity before the PSDU is transmitted. The data field may include padding bits in the PSDU, a service field including a bit sequence for initializing the scrambler, and a coded sequence in which a bit sequence with tail bits appended thereto is encoded. In this case, the encoding scheme may be selected from 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 may include a field including information on a PLCP Protocol Data Unit (PPDU) to be transmitted.

In the PLCP sublayer 210, the above-described field is added to the PSDU to generate a PLCP Protocol Data Unit (PPDU) and transmitted to the receiving station via the PMD sublayer. The receiving station receives the PPDU and generates a PLCP preamble, data Get and restore the information needed for restoration. The PLCP sublayer of the receiving station transmits the RXVECTOR parameter including the PLCP preamble and control information included in the PLCP header to the MAC sublayer to interpret the PPDU in the receiving state and acquire the data.

3 and 4 are block diagrams illustrating a format of a PPDU used in a wireless local area network (LAN) system to which the embodiment of the present invention can be applied. Hereinafter, a STA operating in a legacy wireless LAN system based on IEEE 802.11a / b / g, which is an existing wireless LAN standard prior to IEEE 802.11n, is referred to as a legacy STA (Legacy STA). In addition, STA that can support HT in HT Wireless LAN system based on IEEE 802.11n is called HT-STA.

3 and 4 are block diagrams illustrating a format of a PPDU used in a wireless local area network (LAN) system to which the embodiment of the present invention can be applied. Hereinafter, a STA operating in a legacy wireless LAN system based on IEEE 802.11a / b / g, which is an existing wireless LAN standard prior to IEEE 802.11n, is referred to as a legacy STA (Legacy STA). In addition, STA that can support HT in HT Wireless LAN system based on IEEE 802.11n is called HT-STA.

3 shows a legacy PPDU (L-PPDU) format, which is a PPDU used in IEEE 802.11a / b / g, which is a conventional wireless LAN system standard prior to IEEE 802.11n. Accordingly, in an HT wireless LAN system adopting the IEEE 802.11n standard, a legacy STA (L-STA) can transmit and receive L-PPDUs having such a format.

Referring to FIG. 3A, the L-PPDU 310 includes an L-STF 311, an L-LTF 312, an L-SIG field 313, and a data field 314.

The L-STF 311 is used for frame timing acquisition, automatic gain control (AGC) convergence, coarse frequency acquisition, and the like.

The L-LTF 312 is used for frequency offset and channel estimation.

The L-SIG field 313 includes control information for demodulating and decoding the data field 314.

The L-PPDU may be transmitted in the order of L-STF 311, L-LTF 312, L-SIG field 313 and data field 314.

(B) is a block diagram of an HT-mixed PPDU format allowing L-STA and HT-STA to coexist. Referring to FIG. 6B, the HT mixed PPDU 320 includes an L-STF 321, an L-LTF 322, an L-SIG 323, an HT-SIG 324, A plurality of HT-LTFs 326 and a data field 327.

The L-STF 321, the L-LTF 322 and the L-SIG field 323 are the same as those indicated by reference numerals 311, 312 and 313 in FIG. Thus, the L-STA may interpret the data field via the L-LTF 322, the L-LTF 322, and the L-SIG 323 upon receiving the HT mixed PPDU 320. However, the L-LTF field 323 indicates the channel to be performed by the HT-STA to receive the HT mixed PPDU 320 and decode the L-SIG field 323, the HT-SIG 324, and the HT- And may further include information for estimation.

The HT-STA can know that the HT mixed PPDU 320 is a PPDU for itself through the HT-SIG 324 following the L-SIG 323 and demodulate and decode the data field 327 based on the information .

The HT-STF 325 may be used for frame timing synchronization, AGC convergence, etc. for the HT-STA.

The HT-LTF 326 may be used for channel estimation for demodulation of the data field 327. Since IEEE 802.11n supports SU-MIMO, a plurality of HT-LTFs 326 can be configured for channel estimation for each data field transmitted in a plurality of spatial streams.

The HT-LTF 326 may comprise a Data HT-LTF used for channel estimation for spatial streams and an extended HT-LTF (Extension HT-LTF) used additionally for full channel sounding have. Thus, the plurality of HT-LTFs 326 may be equal to or greater than the number of spatial streams transmitted.

The L-STF 321, the L-LTF 322, and the L-SIG field 323 are transmitted first so that the HT-mixed PPDU 320 can also receive the L-STA and acquire the data. The HT-SIG field 324 is then transmitted for demodulation and decoding of data transmitted for the HT-STA.

STA and HT-STA to receive the corresponding PPDU to acquire data, and transmits the HT-STF 325, HT-SIG 324, and HT- The LTF 326 and the data field 327 are subjected to wireless signal transmission through precoding. Herein, the STA 323 transmits a plurality of HT-LTFs 326 and a plurality of data fields 327 to transmit the HT-STFs 325 in order to allow the receiving STAs to take into account the variable power by precoding. do.

Although the HT-STA using 20 MHz in the HT-WLAN system uses 52 data subcarriers per OFDM symbol, the L-STA using the same 20 MHz still uses 48 data subcarriers per OFDM symbol. Since the HT-SIG field 324 in the HT mixed PPDU 320 format is decoded using the L-LTF 322 to support backward compatibility with the existing system, the HT-SIG field 324 is 48 × 2 data subcarriers. The HT-STF 325 and the HT-LTF 426 are configured with 52 data subcarriers per OFDM symbol. As a result, since the HT-SIG field 324 is 1/2 and BPSK (Binary Phase Shift Keying), each HT-SIG field 324 is composed of 24 bits and is transmitted in a total of 48 bits. That is, the channel estimation for the L-SIG field 323 and the HT-SIG field 324 uses the L-LTF 322 and the bit sequence constituting the L-LTF 322 is expressed by the following Equation 1 . The L-LTF 322 is composed of 48 data subcarriers excluding a DC subcarrier per symbol.

(C) is a block diagram showing an HT-Greenfield PPDU 330 format that only the HT-STA can use. Referring to FIG. 3C, the HT-GF PPDU 330 includes an HT-GF-STF 331, an HT-LTF1 332, an HT- SIG 333, a plurality of HT- (335).

The HT-GF-STF 331 is used for frame timing acquisition and AGC.

HT-LTF1 332 is used for channel estimation.

The HT-SIG 333 is used for demodulating and decoding the data field 335.

The HT-LTF2 334 is used for channel estimation for demodulation of the data field 335. Likewise, since the HT-STA uses SU-MIMO, channel estimation is required for each of the data fields transmitted in a plurality of spatial streams, so that the HT-LTF 326 can be composed of a plurality of channels.

The plurality of HT-LTFs 334 may be composed of a plurality of Data HT-LTFs and a plurality of extended HT-LTFs, similar to the HT-LTFs 326 of the HT mixed PPDUs 320.

Each of the data fields 314, 327, and 335 shown in Figures (a), (b), and (c) may include a service field, a scrambled PSDU, a tail bit, and a padding bit. The service field may be used to initialize the scrambler. The service field may be set to 16 bits. In this case, the bits for scrambler initialization can be implemented with 7 bits. The tail field may consist of a bit sequence necessary to return the convolution encoder to a zero state. The tail field may be allocated a bit size proportional to the number of BCC (Binary Convolutional Code) encoders used to encode data to be transmitted, and more specifically, may be implemented to have 6 bits per BCC number.

4 is a diagram showing an example of a PPDU format used in a wireless LAN system supporting VHT.

4, the PPDU 400 includes an L-STF 410, an L-LTF 420, an L-SIG field 430, a VHT-SIGA field 440, a VHT- STF 450, LTF 460, VHT-SIGB field 470, and data field 480.

The PLCP sublayer constituting the PHY adds necessary information to the PSDU received from the MAC layer and converts it into a data field 480. The L-STF 410, the L-LTF 420, the L-SIG field 430, The PPDU 400 is added by adding the fields of the -SIGA field 440, the VHT-STF 450, the VHT-LTF 460, and the VHT-SIGB 470, To the STA. The control information used for the PPDU to be generated by the PLCP sublayer and included in the PPDU, and the control information used by the receiving STA to interpret the PPDU are provided from the TXVECTOR parameter received from the MAC layer.

The L-STF 410 is used for frame timing acquisition, automatic gain control (AGC) convergence, coarse frequency acquisition, and the like.

The L-LTF 420 is used for channel estimation for demodulation of the L-SIG field 430 and the VHT-SIGA field 440.

The L-SIG field 430 is used by the L-STA to receive the PPDU 400 and interpret it to obtain data. The L-SIG field 430 includes a rate sub-field, a length sub-field, a parity bit, and a tail field. The rate subfield is set to a value indicating a bit rate for the data to be currently transmitted.

The length subfield is set to a value indicating the octet length of the PSDU requesting the MAC layer to transmit to the PHY layer. The L_LENGTH parameter, which is a parameter related to the octet length information of the PSDU, is determined based on the TXTIME parameter, which is a parameter related to the transmission time. TXTIME indicates a transmission time determined by the PHY layer for transmission of a PPDU including a PSDU in response to a transmission time requested by the MAC layer for transmission of a physical service data unit (PSDU). Therefore, since the L_LENGTH parameter is a time-related parameter, the length subfield included in the L-SIG field 430 includes information related to the transmission time.

The VHT-SIGA field 440 contains control information (or signal information) necessary for the STAs receiving the PPDU to interpret the PPDU 400. The VHT-SIGA field 440 is transmitted in two OFDM symbols. Accordingly, the VHT-SIGA field 440 can be divided into the VHT-SIGA1 field and the VHT-SIGA2 field. The VHT-SIGA1 field includes channel bandwidth information used for PPDU transmission, identification information related to whether or not Space Time Block Coding (STBC) is used, information indicating a method of transmitting a PPDU among SU or MU-MIMO, In the case of MU-MIMO, information indicating a STA group to be transmitted, which is a plurality of STAs paired with an AP and an MU-MIMO, and information on a spatial stream allocated to each STA included in the STA group to be transmitted. The VHT-SIGA2 field includes short guard interval (SGI) -related information.

The information indicating the MIMO transmission scheme and the information indicating the STA group to be transmitted may be implemented as one MIMO indication information, and may be implemented as a group ID, for example. The group ID may be set to a value having a specific range, and a specific value in the range indicates the SU-MIMO transmission scheme. Otherwise, when the PPDU 400 is transmitted in the MU-MIMO transmission scheme, It can be used as an identifier for STA group.

If the group ID indicates that the corresponding PPDU 400 is transmitted through the SU-MIMO transmission scheme, the VHT-SIGA2 field indicates whether the coding scheme applied to the data field is Binary Convolution Coding (BCC) or Low Density Parity Check (LDPC) And modulation coding scheme (MCS) information for the channel between the sender and the receiver. Further, the VHT-SIGA2 field may include a partial AID (partial AID) including an AID of a transmission target STA of the PPDU and / or a partial bit sequence of the AID.

When the group ID indicates that the corresponding PPDU 400 is transmitted through the MU-MIMO transmission scheme, the VHT-SIGA field 440 indicates that the coding scheme applied to the data field to which transmission is intended to the MU-MIMO paired receiving STAs is BCC Coding instruction or LDPC coding. In this case, modulation coding scheme (MCS) information for each receiving STA may be included in the VHT-SIGB field 470.

The VHT-STF 450 is used to improve the performance of the AGC estimation in the MIMO transmission.

The VHT-LTF 460 is used by the STA to estimate the MIMO channel. Since the VHT wireless LAN system supports MU-MIMO, the VHT-LTF 460 can be set to the number of spatial streams to which the PPDU 400 is transmitted. In addition, full channel sounding is supported, and the number of VHT LTFs can be increased when it is performed.

The VHT-SIGB field 470 contains dedicated control information necessary for a plurality of MIMO paired STAs to receive the PPDU 400 and obtain the data. Thus, the STA may be designed to decode the VHT-SIGB field 470 only if the control information contained in the VHT-SIGA field 440 indicates that the PPDU 400 currently received is MU-MIMO transmitted. have. Conversely, if the control information contained in the VHT-SIGA field 440 indicates that the PPDU 400 currently received is for a single STA (including SU-MIMO), the STA does not decode the VHT-SIGB field 470 .

The VHT-SIGB field 470 may include information on a modulation and coding scheme (MCS) and rate-matching for each STA. It may also include information indicating the PSDU length included in the data field for each STA. The information indicating the length of the PSDU is information indicating the length of the bit sequence of the PSDU, and can be indicated in units of an octet. On the other hand, when the PPDU is SU-transmitted, information on the MCS may not be included in the VHT-SIGB field 470 because it is included in the VHT-SIGA field 440. The size of the VHT-SIGB field 470 may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.

The data field 480 contains data intended for transmission to the STA. The data field 480 includes a service field for initializing a scrambler and a PLCP service data unit (PSDU) to which a MAC Protocol Data Unit (MPDU) is transmitted in the MAC layer, a service field for initializing a convolution encoder, a tail field including a bit sequence necessary for returning the data field to a normal state, and padding bits for normalizing the length of the data field. In the case of MU transmission, the data field transmitted to each STA may include a data unit, each of which is intended to be transmitted, and the data unit may be an aggregate MPDU (A-MPDU).

The fields included in each PPDU format shown in FIG. 3 and FIG. 4 can be transmitted as OFDM symbols through the processing of the physical layer. In particular, a data sequence constituting a data field may be transmitted in at least one data OFDM symbol according to its size. In addition, normal generation, transmission, reception and interpretation of data OFDM symbols may be interrupted due to radio channel conditions, time-synchronization inconsistencies between transmitters / receivers, and inter-symbol interference. In order to prevent this, a guard interval (GI) is applied to the data OFDM symbol, thereby preventing abnormal operations that may occur and ensuring reliable data unit transmission / reception. In addition, in the HT wireless LAN system and the VHT wireless LAN system, SGI is applied and the time consumed due to the guard interval can be reduced, so that more efficient transmission and reception can be guaranteed. HT wireless LAN system and VHT wireless LAN system, whether or not the SGI is applied in the signal field and the VHT-SIG A field can be indicated.

The STA1 21, the STA2 22 and the STA3 23 in the case where the AP 10 wants to transmit data to the STA1 21, the STA2 22 and the STA3 23 in the given wireless LAN system as shown in Fig. And the STA4 24 to the STA group. In this case, it is possible to allocate no spatial stream allocated to the STA4 24 as shown in FIG. 4, allocate a specific number of spatial streams to each of the STA1 21, the STA2 22 and the STA3 23, Lt; / RTI > In the example shown in Fig. 4, it can be seen that one spatial stream is allocated to STA1 21, three spatial streams are allocated to STA2 22, and two spatial streams are allocated to STA3.

5 is a diagram for explaining a dynamic bandwidth indication.

Referring to FIG. 5, the AP and / or STA operates dynamic bandwidth allocation as an RTS / CTS exchange. For example, the AP and / or the STA may detect a frequency channel in which there is interference through a request to send (RTS) / clear to send (CTS) exchange and transmit the dynamic Increases the efficiency of frequency use by handshaking frequency assignment.

6 is a diagram illustrating a method for performing scrambling of data in an 802.11ac.

Referring to FIG. 6, allocation of dynamic frequency in 802.11ac is possible by inserting bandwidth information (BW information) in an RTS or CTS signal. For example, as shown in FIG. 6, a scrambler seed is inserted into an operator and inserted in a service field of a PPDU. And Table 2 shows the contents of the first 7 bits of the scrambling sequence when CH_BANDWIDTH_IN_HT is present.

Next, a dynamic bandwidth indication in 802.11ah is disclosed. APs and / or STAs based on each 802.11ah can recognize both 1MHz preamble and 2MHz preamble. However, in 802.11ah, unlike in 802.11ac, there is no need to consider backward compatibility within the band and coexistence with legacy versions of legacy APs and / or STAs. Therefore, NON_HT_DUPLICATE transmission considering backward compatibility is not defined.

On the other hand, in 802.11ah, all APs and / or STAs must be able to decode both the 1MHz preamble and the 2MHz preamble. Bandwidth information available from the preamble includes bandwidth information in the 1 MHz mode and bandwidth information in the 2 MHz mode and above. Table 3 below is an example showing the number of bits of the bandwidth indication in a short preamble and a long preamble.

In 802.11ah, to enable dynamic bandwidth indication, the APs and / or STAs identify the dynamic bandwidth indication with bandwidth information in the mode of 2MHz or more, and the bandwidth is 1MHz by auto detection in the 1MHz mode.

In the 802.11ah system, when a preamble is received over a multi-channel in the time domain as shown in FIG. 5, the receiver (AP and / or STA) There is a problem that an error occurs in decoding the bandwidth information. This is because a phase rotation pattern is applied as shown in Equation (2).

Here, the relationship between the channel bandwidth (CH_BANDWIDTH) and Y _{k and BW} is shown in the following table.

Referring to Equation (2), in 802.11ah, as in 802.11ac, a phase rotation pattern is applied on the frequency axis to reduce the PAPR of the SIG in dynamic bandwidth allocation (or dynamic frequency allocation). This phase rotation pattern depends on the frequency span of the entire multi-channel as shown below. This affects the stability of the system.

-4 MHz preamble: phase rotation pattern for each 2 MHz piece = [1 j]

-8 MHz preamble: phase rotation pattern for each 2 MHz piece = [1 -1 -1 -1]

-16 MHz preamble: phase rotation pattern for each 2 MHz piece = [1 -1 -1 -1 1 -1 -1 -1]

Therefore, there is a need for a method of supporting allocation of dynamic bandwidth by distinguishing between cases where the phase rotation pattern should be permitted and those not. Hereinafter, a bandwidth indication method according to the present embodiment for solving such a problem will be described.

According to one embodiment, the AP and / or the STA applies a phase rotation to the PPDU, wherein the AP and / or the STA performs phase rotation on the PPDU (or PPDU for exchange of bandwidth information) related to the bandwidth indication such as RTS or CTS Do not apply. That is, the AP and / or STA is to transmit (or code) or receive (or decode) the PPDU associated with the bandwidth indication without phase rotation applied. That is, by selectively allowing the phase rotation, it is possible to solve the problem of uniformly applying the phase rotation as in the conventional art. This is very simple to implement and can simplify decoding of the receiver.

Herein, information indicating that the PPDU is related to the bandwidth indication, for example, a TXVECTOR parameter called "BW_EXCHANGE" Thus, the AP and / or STA may indicate that the PPDU is related to a bandwidth indication based on a TXVECTOR parameter called "BW_EXCHANGE ". For this, NON_HT_MODULATION in 802.11ac as shown in Table 5 below can be referred to.

On the other hand, for the bandwidth indication, a method of indicating that it is dynamic or static is required. That is, there is a need for a method of indicating whether the partial utilization of the bandwidth to be notified (available) or not (not) is available. To this end, one bit of "DYN_BANDWIDTH" may be added to the SIG field in the 2 MHz preamble (short preamble and long preamble) to support dynamic bandwidth indication performance. In other words, one bit of DYN_BANDWIDTH is required for dynamically setting the usable frequency band as shown in Table 6, which can be added to the SIG field of the 2 MHz preamble of 802.11ah.

Table 7 shows the values indicated by the value of DYN_BANDWIDTH added to the SIG field.

For example, referring to Table 6 below, it indicates that DYN_BANDWIDTH = 0 indicates 'static', and DYN_BANDWIDTH = 1 indicates 'dynamic'.

This makes it possible to utilize already defined bandwidth information in the preamble of 802.11ah. In addition, by allowing the phase rotation selectively in the bandwidth indication, it is possible to solve the problem caused by uniformly applying the phase rotation.

According to another embodiment, the AP and / or the STA does not use the bandwidth information (or scrambled) in the SIG field of the preamble of 802.11ah for the purpose of bandwidth information, the DYN_BANDWIDTH information and the bandwidth information can be additionally inserted as a feeding function for inputting a scrambler seed. This can reduce the burden of calculating the phase rotation, but the design structure of the existing SIG field in the preamble must be changed. In addition, there is a burden of inscribing bandwidth information as a scrambler seed in the service field and decoding it by the receiver.

7 is a block diagram illustrating a wireless device in which embodiments of the present invention may be implemented.

7, a wireless device 1300 includes a processor 1310, a memory 1320, and a transceiver 1330. Transceiver 1330 transmits and / or receives wireless signals, but implements the physical layer of IEEE 802.11. Processor 1310 may be configured to function and be operatively coupled to transceiver 1330. Processor 1310 may be configured to generate a SIG field for the bandwidth indication described herein. Processor 1310 may be configured to generate and send and receive NDPs in accordance with the present disclosure. The processor 1310 may be configured to perform the bandwidth indication according to an embodiment of the present invention.

Also, the AP or STA disclosed in FIG. 1 includes the wireless device 1300 of FIG.

Processor 1310 and / or transceiver 1330 may include an application-specific integrated circuit (ASIC), other chipset, logic circuitry, and / or data processing device. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module may be stored in memory 1320 and executed by processor 1310. [ The memory 1320 may be included within the processor 1310 and may be operatively connected to the processor 1310 by various means known in the art and located externally.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

Claims (8)

1. A wireless device for receiving a physical protocol data unit (PPDU) in a wireless communication system,
Transceiver;
Memory; And
A processor,
The processor comprising:
The PPDU is received via the transceiver based on the fact that the phase rotation is applied when the PPDU is transmitted in the basic bandwidth of 1 MHz mode and phase rotation is not applied when the PPDU is transmitted in the mode of 2 MHz or more which is the extended bandwidth ;
And to obtain data contained in the PPDU.
The method according to claim 1,
The PPDU generated in the 1 MHz mode does not include bandwidth related information,
Wherein the PPDU generated in the mode of 2 MHz or higher includes the bandwidth related information.
3. The method of claim 2,
And if the PPDU includes the bandwidth related information, the processor receives the PPDU to which the phase rotation is not applied based on an RXVECTOR parameter indicating a bandwidth exchange (BW_EXCHANGE).
3. The method of claim 2,
Wherein the processor receives the PPDU based on a SIG field comprising a one-bit DYN_BANDWIDTH indicating that the bandwidth indication is dynamic or static if the bandwidth related information comprises information indicative of bandwidth.
A method for receiving a physical protocol data unit (PPDU) in a wireless communication system,
Receiving the PPDU based on the phase rotation being applied when the PPDU is transmitted in a basic bandwidth of 1 MHz mode and phase rotation not being applied when the PPDU is transmitted in a mode of 2 MHz or more which is an extended bandwidth; And
And obtaining data contained in the PPDU.
6. The method of claim 5,
The PPDU generated in the 1 MHz mode does not include bandwidth related information,
Wherein the PPDU generated in the mode of 2 MHz or higher includes the bandwidth related information.
The method according to claim 6,
If the PPDU includes the bandwidth related information, receiving the PPDU to which the phase rotation is not applied based on an RXVECTOR parameter indicating a bandwidth exchange (BW_EXCHANGE).
The method according to claim 6,
And if the bandwidth related information includes information indicating bandwidth, receiving the PPDU based on a SIG field including a one-bit DYN_BANDWIDTH indicating that the bandwidth indication is dynamic or static.

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