WO2016018026A1

WO2016018026A1 - Method by which sta receives signal in wireless lan system

Info

Publication number: WO2016018026A1
Application number: PCT/KR2015/007829
Authority: WO
Inventors: 이욱봉; 류기선; 조한규; 최진수
Original assignee: 엘지전자 주식회사
Priority date: 2014-07-28
Filing date: 2015-07-28
Publication date: 2016-02-04

Abstract

One embodiment of the present invention relates to a method by which an STA receives a signal in a wireless communication system, comprising the steps of: receiving a PPDU from an AP; and decoding the PPDU, wherein a downlink bandwidth through which the PPDU is transmitted includes a resource unit for a plurality of STAs capable of being multiplexed with the STA, and when performing the decoding, the STA assumes that there is a DC subcarrier also in the center part of a bandwidth allocated to the STA, besides being in the center of the downlink bandwidth.

Description

Receiving method of STA in WLAN system

The following description relates to a method for receiving a signal from a SAT in a wireless communication system and a station apparatus for performing the same.

First, a wireless local area network (WLAN) system will be described as an example of a system to which the present invention can be applied.

The standard for WLAN technology is being developed as an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11a and b are described in 2.4. Using unlicensed band at GHz or 5 GHz, IEEE 802.11b provides a transmission rate of 11 Mbps and IEEE 802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g applies orthogonal frequency-division multiplexing (OFDM) at 2.4 GHz to provide a transmission rate of 54 Mbps. IEEE 802.11n applies multiple input multiple output OFDM (MIMO-OFDM) to provide a transmission rate of 300 Mbps for four spatial streams. IEEE 802.11n supports channel bandwidths up to 40 MHz, in this case providing a transmission rate of 600 Mbps.

The WLAN standard uses a maximum of 160MHz bandwidth, supports eight spatial streams, and supports IEEE 802.11ax standard through an IEEE 802.11ac standard supporting a speed of up to 1Gbit / s.

The present invention relates to which numerology the STA will receive when a new PPDU is used.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In one embodiment of the present invention, a method for receiving a signal by a STA in a wireless communication system, the method comprising: receiving a PPDU from an AP; And decoding the PPDU, wherein the downlink bandwidth through which the PPDU is transmitted includes resource units for a plurality of STAs that can be multiplexed with the STA, and the STA performs the downlink bandwidth when performing the decoding. In addition to the center of, the STA is a signal reception method of the STA, assuming that the DC subcarrier also exists in the center portion of the bandwidth allocated to the STA.

An embodiment of the present invention, an STA apparatus in a wireless communication system, comprising: a receiving module; And a processor, wherein the processor receives a PPDU from an AP, decodes the PPDU, and a downlink bandwidth through which the PPDU is transmitted includes resource units for a plurality of STAs that can be multiplexed with the STA; When the decoding is performed, the STA is a STA device that assumes that a DC subcarrier exists in a center portion of the bandwidth allocated to the STA, in addition to the center of the downlink bandwidth.

Embodiments of the invention may include all or part of the following.

Timing-related constants used by the STA when performing the decoding may vary according to bandwidth allocated to the STA.

The timing-associated constant may include the number of data subcarriers, the number of pilot subcarriers, and the total number of subcarriers.

The number of data subcarriers of the resource unit may be 52.

The number of pilot subcarriers may be four.

The bandwidth allocated to the STA may be a multiple of the resource unit.

According to the present invention, STAs can efficiently use a new PPDU while reducing complexity.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings appended hereto are for the purpose of providing an understanding of the present invention and for illustrating various embodiments of the present invention and for describing the principles of the present invention together with the description of the specification.

1 is a diagram illustrating an example of a configuration of a WLAN system.

2 is a diagram illustrating another example of a configuration of a WLAN system.

3 is a view for explaining a frame structure that can be used in a WLAN system.

4 shows a frame format according to the IEEE 802.11ac standard technology.

5 is a diagram for explaining a frame time interval.

6 to 8 are diagrams for explaining an embodiment of the present invention.

9 is a diagram illustrating a configuration of a transmitting and receiving device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the invention may be practiced.

The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are omitted or shown in block diagram form, centering on the core functions of each structure and device, in order to avoid obscuring the concepts of the present invention.

As described above, the following description relates to a method for transmitting a frame in a WLAN system and a station apparatus for performing the same. To this end, first, a WLAN system to which the present invention is applied will be described in detail.

1 is a diagram illustrating an example of a configuration of a WLAN system.

As shown in FIG. 1, the WLAN system includes one or more basic service sets (BSSs). A BSS is a set of stations (STAs) that can successfully synchronize and communicate with each other.

STA is a logical entity that includes a medium access control (MAC) and a physical layer interface to a wireless medium, and includes an access point (AP) STA and a non-AP STA (Non-AP Station). It includes. Simply referred to as an AP refers to an AP STA, and also referred to as an AP may refer to a non-AP STA. A non-AP STA is a terminal, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal, or a mobile subscriber. It may also be called another name such as a mobile subscriber unit.

The AP is an entity that provides an associated station (STA) coupled to the AP to access a distribution system (DS) through a wireless medium. The AP may be called a centralized controller, a base station (BS), a Node-B, a base transceiver system (BTS), or a site controller.

BSS can be divided into infrastructure BSS and Independent BSS (IBSS).

The BBS shown in FIG. 1 is an IBSS. The IBSS means a BSS that does not include an AP. Since the IBSS does not include an AP, access to the DS is not allowed, thereby forming a self-contained network.

The BSS shown in FIG. 2 is an infrastructure BSS. Infrastructure BSS includes one or more STAs and APs. In the infrastructure BSS, communication between non-AP STAs is performed via an AP. However, when a direct link is established between non-AP STAs, direct communication between non-AP STAs is also possible.

As shown in FIG. 2, a plurality of infrastructure BSSs may be interconnected through a DS. A plurality of BSSs connected through a DS is called an extended service set (ESS). STAs included in the ESS may communicate with each other, and a non-AP STA may move from one BSS to another BSS while seamlessly communicating within the same ESS.

The DS is a mechanism for connecting a plurality of APs. The DS is not necessarily a network, and there is no limitation on the form if it can provide a predetermined distribution service. For example, the DS may be a wireless network such as a mesh network or a physical structure that connects APs to each other.

Based on the above, a frame structure that can be used in a WLAN system will be described.

3 is a view for explaining a frame structure that can be used in a WLAN system.

Specifically, reference numeral 310 of FIG. 3 illustrates a physical layer protocol data unit (PPDU) format for a terminal according to the IEEE 802.11a / g standard, and

reference numerals

320 and 330 refer to an IEEE 802.11n standard. A PPDU format for a terminal is shown. As shown in FIG. 3, a terminal supporting the IEEE 802.11n scheme uses a frame called HT-.

More specifically, reference numeral 320 denotes a HT-mixed format PPDU of an IEEE 802.11n terminal, and 330 denotes a HT-greenfield format PPDU.

Reference numeral 340 denotes a configuration of a data area in each PPDU, and the data area includes a PSDU (Physical Service Data Unit).

4 shows a frame format according to the IEEE 802.11ac standard technology.

As shown in FIG. 4, a terminal conforming to the IEEE 802.11ac standard supports a field denoted as VHT-.

Specifically, each field shown in FIG. 4 is as follows.

Table 1

Field	Description
L-STF	Non-HT Short Training field
L-LTF	Non-HT Long Training field
L-SIG	Non-HT SIGNAL field
VHT-SIG-A	VHT Signal A field
VHT-STF	VHT Short Training field
VHT-LTF	VHT Long Training field
VHT-SIG-B	VHT SIGNAL B field
Data	The Data field carries the PSDU (s)

프레임 간 시간 간격(IFS: Inter-Frame Space)Inter-Frame Space (IFS)

The time interval between two frames may be defined as an inter-frame space (IFS). The STA may determine whether the channel is used during IFS through carrier sensing. The DCF MAC layer defines four IFSs, whereby the priority to occupy the wireless medium can be determined.

IFS may be set to a specific value according to the physical layer regardless of the bit rate of the STA. Types of IFS are the same as SIFS (Short IFS), PIFS (PCF IFS), DIFS (DCF IFS), and EIFS (Extended IFS). SIFS (Short IFS) is used when transmitting an RTS / CTS or ACK frame and may have the highest priority. PIFS (PCF IFS) may be used for PCF frame transmission, and DIFS (DCF IFS) may be used for DCF frame transmission. Extended IFS (EIFS) is used only when a frame transmission error occurs and does not have a fixed interval.

The relationship between each IFS is defined as a time gap on the medium, and related attributes are provided by the physical layer as shown in FIG. 5 below.

5 is a diagram illustrating the relationship of IFS. At all media timings, the end of the last symbol of the PPDU indicates the end of transmission, and the first symbol of the preamble of the next PPDU indicates the start of transmission. All MAC timings may be determined with reference to the PHY-TXEND.confirm primitive, PHYTXSTART.confirm primitive, PHY-RXSTART.indication primitive and PHY-RXEND.indication primitive.

Referring to FIG. 5, the SIFS time aSIFSTime and the slot time aSlotTime may be determined for each physical layer. The SIFS time has a fixed value, and the slot time may change dynamically according to a change in the air delay time (aAirPropagationTime). SIFS, PIFS, and DIFS may be defined as Equations 1 to 3, respectively, and the values in parentheses in each equation are generally used. However, this value may vary by terminal and / or by location.

Equation 1

Equation 2

Equation 3

6 shows an example of a High Efficiency PLCP protocol data unit (HE-PPDU) frame format that can be applied to an embodiment of the present invention.

The example of FIG. 6A includes a 12.8? S HE-SIGA field, and may include a 1 symbol HE-STF field, a HE-LTF field, and a 1 symbol HE-SIGB field. From the beginning of the HE-STF, 256, 512, 1024, and 2048 FFTs can be applied to 20 MHz, 40 MHz, 80 MHz, and 160 MHz HE PPDU formats, respectively. HE PPDU preamble length is 8 (L-STF) + 8 (L-LTF) + 4 (L-SIG) + 12.8 (HE-SIGA) + 16 (HE-STF) + X (times) 16 (HE-LTF) +16 (HE-SIGB) = 80.8us (X = 1 case).

The PPDU format of FIG. 6 (b) may include a 1 symbol HE-STF field, a 1 symbol HE-SIG field, and a HE-LTF field. From the beginning of the HE-STF, 256, 512, 1024, and 2048 FFTs can be applied to 20 MHz, 40 MHz, 80 MHz, and 160 MHz HE PPDU formats, respectively. HE PPDU preamble length is 8 (L-STF) + 8 (L-LTF) + 4 (L-SIG) + 16 (HE-STF) + 16 (HE-SIGA) + X (times) 16 (HE-LTF) = 68us (X = 1 case).

The PPDU format of FIG. 6C may include a 1 symbol HE-STF field and a 1 symbol HE-SIG field. From the beginning of the HE-STF, 256, 512, 1024, and 2048 FFTs can be applied to the 20 MHz, 40 MHz, 80 MHz, and 160 MHz HE PPDU formats, respectively. The HE PPDU preamble length may be 8 (L-STF) +8 (L-LTF) +4 (L-SIG) +16 (HE-STF) +16 (HE-SIGA) = 52us.

The PPDU format as in the above example may be for an FFT size four times larger in each bandwidth than the existing IEEE 802.11 OFDM system (IEEE 802.11a, 802.11n, 802.11ac). The SAT may receive such a PPDU from the AP and decode the PPDU. Here, the downlink bandwidth through which the PPDU is transmitted may include a resource unit (701 of FIG. 7) for a plurality of STAs that may be multiplexed with the STA. In addition, as illustrated in FIG. 7, the STA may assume that in addition to the center of the downlink bandwidth, the DC subcarrier exists in the center portion of the bandwidth allocated to the STA when decoding is performed. That is, the position where the DC subcarrier is assumed to exist depends on the bandwidth allocated to the STA. The bandwidth allocated to the STA may be a multiple of a resource unit.

Timing-related constants used by the STA when performing the decoding may vary depending on the bandwidth allocated to the STA. Here, the timing-associated constant may include the number of data subcarriers, the number of pilot subcarriers, and the total number of subcarriers. Timing-related constants may be used as defined in the following Table 2 (Timing-related constants of IEEE 802.11ah) or Table 3 (Timing-related constants of IEEE 802.11ac).

TABLE 2

TABLE 3

For example, the number of data subcarriers in a resource unit may be 52 and the number of pilots may be four.

In addition, the STA data and the channel estimation LTF may be transmitted according to the transmission bandwidth of each allocated STA. For example, when simultaneously supporting up to four STAs at 20 MHz, 20 MHz may be divided into four subblocks. For example, 20 MHz (N_SD = 52) of VHT for one continuous, 40 MHz (N_SD = 108) for VHT for two consecutive, and 80 MHz (N_SD = 234) for VHT for four consecutive STAs. Can be used. For other allocation numbers (when allocated non-contiguous sub-blocks, or contiguous sub-blocks rather than two or four), group them into two consecutive contiguous sub-blocks and four sub-blocks. The interleaver may be performed in-between, and a segment parser may be placed between subblocks in a manner similar to that of 160 MHz or 80 + 80 MHz transmission in VHT, thereby obtaining maximum diversity gain in the frequency axis. The same method can be used at 40 MHz / 80 MHz / 80 + 80 MHz / 160 MHz.

In addition, in order to reduce the complexity and overhead of the HE-SIG, the maximum number of allocated STAs may be fixed to 4 or 8, and at this time, the STAs may be allocated as contiguous resources or a set of subbands grouped by 2 or 4 may be specified. Patterns can be assigned (using permutation or interleaving techniques).

In the case of uplink, it is always allocated in multiples of 20 MHz per STA (i.e. 20 MHz, 40 MHz, 80 MHz, 80 + 80 MHz, 160 MHz), i.e. 4, 8, 16, 16 + 16 consecutive subbands in the example above. 32 can be allocated, and at this time, a specific pattern of mixing the above-mentioned sets of 2 or 4 subbands may not be applied. This is to ensure coexistence with the existing system since the UL transmits only a portion allocated to each STA, unlike the DL. Specifically, this is because legacy legacy STAs may deferral after CCA only if they match the existing transmission bandwidth.

8 illustrates an example of the pilot position and the number of PPDU STA dependent parts (HE-LTF and / or data). Specifically, FIG. 8 (a) shows a case where bandwidth is allocated to two STAs by 10 Mhz. At this time, the STA of the upper 10MHz can be assigned to the subcarrier index 6 ~ 122, and among them, the pilot can be transmitted to 117, 89, 75, 53, 39, 11. In addition, subcarrier indexes 63, 64, and 65 may transmit no data. Subcarrier indexes (-6) to (-122) may be allocated to the STA of the lower 10 MHz, and pilots may be located at -117, -89, -75, -53, -39, and -11. Also, the subcarrier indexes -63, -64, and -65 may not transmit any data.

8 (b) is a case where 10, 5, and 5 MHz are allocated to three STAs, respectively. In this case, the STA of the upper 10 MHz can be allocated up to subcarrier indexes 6 to 122, and pilots can be located at 117, 89, 75, 53, 39, and 11 among them. In addition, subcarrier indexes 63, 64, and 65 may transmit no data. The STA of the lower first 5 MHz may be allocated up to subcarrier indexes (-4) to (-60), and pilots may be located at -53, -39, -25, and -11. In addition, subcarrier index -32 may not transmit any data. The subcarrier indexes (-68) to (-124) may be allocated to the STA of the lower second 5 MHz, and pilots may be located at -75, -89, -103, and -117. Also, subcarrier index -96 may not transmit any data. 8 (c) is a case where 5, 10, and 5 MHz are allocated to three STAs, respectively. The STA of the upper 5 MHz may be allocated up to subcarrier indexes 68 to 124, and pilots may be located at 117, 103, 89 and 75. In addition, subcarrier index 96 may transmit no data. The intermediate 10MHz STA can be allocated to subcarrier indexes -58 to 58, and pilots can be located at 53, 25, 11, -11, -25, and -53. In addition, subcarrier indexes 1, 0, and -1 may transmit no data. The STA of the last 5 MHz can be allocated up to subcarrier indexes (-68) to (-124), and pilots can be located at -75, -89, -103, and -117. Also, subcarrier index -96 may not transmit any data. 8 (d) is allocated to three STAs by 5, 5, and 10 MHz, and the subcarrier indexes 68 through 124 are allocated to the STA of the first 5 MHz, among which 75, 89, 103, and 117 are assigned. The pilot can be located. In addition, subcarrier index 96 may transmit no data. STAs of the upper second 5 MHz may be allocated up to subcarrier indexes (4) to (60), and pilots may be located at 53, 39, 25, and 11 therein. In addition, subcarrier index 32 may not transmit any data. Subcarrier indexes (-6) to (-122) may be allocated to the STA of the lower 10 MHz, and pilots may be located at -117, -89, -75, -53, -39, and -11. Also, the subcarrier indexes -63, -64, and -65 may not transmit any data.

When four STAs are allocated as 8 (e), the first 5MHz STAs can be assigned subcarrier indexes 68 through 124, and pilots can be located at 75, 89, 103, and 117. have. In addition, subcarrier index 96 may transmit no data. STAs of the upper second 5 MHz may be allocated up to subcarrier indexes (4) to (60), and pilots may be located at 53, 39, 25, and 11 therein. In addition, subcarrier index 32 may not transmit any data. The STA of the lower first 5 MHz may be allocated up to subcarrier indexes (-4) to (-60), and pilots may be located at -53, -39, -25, and -11. In addition, subcarrier index -32 may not transmit any data. The subcarrier indexes (-68) to (-124) may be allocated to the STA of the lower second 5 MHz, and pilots may be located at -75, -89, -103, and -117. Also, subcarrier index -96 may not transmit any data.

That is, in the example of FIG. 8, the position and number of pilots are the same as the VHT bandwidth option according to the bandwidth option of each subband. At this time, the numerology (N_SD, N_SP, N_ST) of each subband may be exactly the same as each bandwidth option of the VHT. For example, one continuous subband may follow 20 MHz numerology of VHT, two subbands may follow 40 MHz numerology, and four may follow 80 MHz numerology.

Alternatively, the location and number of pilots can be located equal to the common part of the DL OFDMA.

Hereinafter, what numerology is used in the common part (HE-STF, HE-SIG) of the PPDU.

As a first method, 20 MHz uses the IEEE 802.11ac (VHT) 80 MHz numerology to reduce implementation complexity. At 20MHz, a 4x FFT results in a 256 size FFT, which is the same as that of the existing 80MHz. That is, in this case, N_SD = 234, N_SP = 8, N_ST = 242, and N_SR = 122 may be used. For 40 MHz, a numerology of VHT 160 MHz can be used. In the case of 80MHz, we can divide it into two segments (upper 40MHz and lower 40MHz) and each segment can use a 40MHz numerology. 160MHz can also be divided into two segments (upper 80MHz and lower 80MHz) and each segment can use 80MHz numerology

As a second method, in the case of 20 MHz, it is divided into four subblocks, and each subblock may use the 20 MHz numerology of IEEE 802.11ac (VHT) or IEEE 802.11n (HT) or IEEE 802.11a. For 40MH, divide into two segments (upper 20MHz and lower 20MHz) and each segment can use 20MHz numerology. The 80 MHz is divided into two segments (upper 40 MHz and lower 40 MHz) and each segment can use a 40 MHz numerology. 160MHz can also be divided into two segments (upper 80MHz and lower 80MHz) and each segment can use 80MHz numerology

본 발명의 실시예에 의한 장치 구성Device configuration according to an embodiment of the present invention

9 is a block diagram illustrating a configuration of a wireless device according to an embodiment of the present invention.

The AP 10 may include a processor 11, a memory 12, and a transceiver 13. The STA 20 may include a processor 21, a memory 22, and a transceiver 23. The

transceivers

13 and 23 may transmit / receive wireless signals and, for example, may implement a physical layer in accordance with the IEEE 802 system. The

processors

11 and 21 may be connected to the

transceivers

13 and 21 to implement a physical layer and / or a MAC layer according to the IEEE 802 system.

Processors

11 and 21 may be configured to perform operations according to the various embodiments of the present invention described above. In addition, modules for implementing the operations of the AP and the STA according to various embodiments of the present invention described above may be stored in the

memory

12 and 22 and executed by the

processors

11 and 21. The

memories

12 and 22 may be included inside the

processors

11 and 21 or may be installed outside the

processors

11 and 21 and connected to the

processors

11 and 21 by known means.

Specific configurations of the AP and STA apparatus as described above may be implemented so that the above-described matters described in various embodiments of the present invention may be independently applied or two or more embodiments may be simultaneously applied, and overlapping descriptions are omitted for clarity. do.

Embodiments of the present invention described above may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For implementation in hardware, a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Embodiments of the present invention as described above may be applied to various mobile communication systems.

Claims

In the method of receiving a signal in a wireless communication system,

Receiving a PPDU from an AP; And

Decoding the PPDU;

Including;

The downlink bandwidth through which the PPDU is transmitted includes a resource unit for a plurality of STAs that can be multiplexed with the STA,

When the decoding is performed, the STA assumes that in addition to the center of the downlink bandwidth, the DC subcarrier also exists in the center portion of the bandwidth allocated to the STA.
The method of claim 1,

Timing-related constants used by the STA when performing the decoding vary according to a bandwidth allocated to the STA.
The method of claim 2,

The timing-related constants include a number of data subcarriers, a number of pilot subcarriers, and a total number of subcarriers.
The method of claim 3,

The signal receiving method of the STA, the number of data subcarriers in the resource unit is 52.
The method of claim 4, wherein

The number of pilot subcarriers is 4, the method of receiving a signal of the STA.
The method of claim 1,

The bandwidth allocated to the STA is a multiple of the resource unit.

Method of receiving signal from STA.
In a STA device in a wireless communication system,

A receiving module; And

Includes a processor,

The processor receives a PPDU from an AP, decodes the PPDU,

The downlink bandwidth on which the PPDU is transmitted includes a resource unit for a plurality of STAs that can be multiplexed with the STA, and the STA, in addition to the center of the downlink bandwidth, is allocated to the STA when the decoding is performed. And a DC subcarrier is also present in the central portion of the STA apparatus.
The method of claim 7, wherein

Timing-related constants used by the STA when performing the decoding depend on a bandwidth allocated to the STA.
The method of claim 9,

The timing-related constants include a number of data subcarriers, a number of pilot subcarriers, and a total number of subcarriers.
The method of claim 10,

Wherein the number of data subcarriers in the resource unit is 52.
The method of claim 11,

Wherein the number of pilot subcarriers is four.
The method of claim 7, wherein

A bandwidth allocated to the STA is a multiple of the resource unit.