Doppler Patterns in Wireless Networks

Abstract

The present application relates to Doppler patterns in wireless networks. In order to receive data in a data field of a PHY protocol data unit (PPDU), wherein the data field includes a midamble, the number of midambles and the number of data symbols included in the data field are determined. The number of midambles is determined based on information in a HE-SIG-A field of the PPDU, information in an L-SIG field of the PPDU, and one or more predetermined values ​​specified by a standard. The number of data symbols can be determined using the number of midambles, and data is received based on the number of midambles and the number of data symbols.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the application date of May 25, 2018, application number 201880050567.6 and invention name “Doppler mode in wireless network”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 511,914, filed May 26, 2017, which is incorporated herein by reference in its entirety. Background Art 1. Technical Field

[0005] The technology described herein generally relates to wireless networking. More specifically, the technology relates to determining parameters of a received transmission, wherein a midamble is used to improve reception of the transmission.

[0006] 2. Description of the Prior Art

[0007] Wireless local area network (WLAN) devices are currently being deployed in a variety of environments. Some of these environments have a large number of access points (APs) and non-AP stations in a geographically limited area. In addition, there is an increasing need for WLAN devices to support a variety of applications, such as video, cloud access, and offloading. In particular, video services are expected to be the dominant service type in many efficient WLAN deployments. Due to the real-time requirements of some of these applications, WLAN users require improved performance in implementing their applications, including improved power consumption for battery-powered devices.

[0008] IEEE (Institute of Electrical and Electronics Engineers) Part 11 is standardizing WLAN under the name of "Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specifications", and a series of standards have been adopted as the evolution of WLAN, including IEEE Standard 802.11 TM -2012 (March 2012) (IEEE 802.11n). IEEE Standard 802.11 was subsequently adopted by IEEE Standard 802.11ae TM -2012, IEEE standard 802.11aa TM -2012, IEEE standard 802.11ad TM -2012, and IEEE standard 802.11ac TM -2013 (IEEE 802.11ac) was revised.

[0009] Recently, the IEEE 802.11ax task group is developing an amendment dedicated to providing high-efficiency (HE) WLAN in high-density scenarios. The 802.11ax amendment is dedicated to improving metrics that reflect user experience, such as the average per-station throughput, the 5th percentile per-station throughput of a group of stations, and the regional throughput. Improvements can be made to support environments such as wireless corporate offices, outdoor hotspots, dense residential apartments, and stadiums.

[0010] In some environments, channel conditions may change during the communication of a data unit. For example, when a non-AP station is moving relative to the AP, the Doppler effect may change the channel conditions. In these environments, a mid-amble may be inserted into the data portion of a communication to allow channel estimation to be performed by a receiving device during reception of the data portion. Placing the mid-amble in the data portion may change the way in which the receiving device determines some parameters of the communication. Summary of the invention

[0011] In one embodiment, a method performed by a wireless device includes: receiving a first part of a PHY protocol data unit (PPDU), the first part including a legacy signal (L-SIG) field; decoding the L-SIG field; and determining a format of the PPDU using the first part. In response to determining that the format of the PPDU is a high-efficiency (HE) format, the method performs receiving and decoding a HE signal A (HE-SIG-A) field, and determining whether the PPDU includes a midamble using a Doppler field of the HE-SIG-A field. In response to determining that the PPDU includes a midamble, the method determines a number N of midambles based on the format of the PPDU and using first information determined by utilizing the HE-SIG-A field and second information determined by utilizing the L-SIG field. MA , the number of intermediate synchronization codes N MA Indicates the number of midambles included in the data field of the PPDU. The number of midambles used is N. MA Determine the number N of data symbols included in the data field of the PPDU SYM , and the number of intermediate synchronization codes used N MA and the number of data symbols N SYM Receive the data field of the PPDU.

[0012] In another embodiment, a wireless device includes a receiver and a processor. The processor is configured to perform receiving a first portion of a PHY protocol data unit (PPDU) using a receiver, the first portion including a legacy signal (L-SIG) field, decoding the L-SIG field, and determining a format of the PPDU using the first portion. The processor is also configured to perform receiving and decoding a HE signal A (HE-SIG-A) field in response to determining that the format of the PPDU is a high efficiency (HE) format, and determining whether the PPDU includes an intermediate synchronization code using a Doppler field of the HE-SIG-A field. The processor is also configured to determine the number of intermediate synchronization codes N according to the format of the PPDU and using first information determined by using the HE-SIG-A field and second information determined by using the L-SIG field in response to determining that the PPDU includes an intermediate synchronization code. MA , the number of intermediate synchronization codes N MA Indicates the number of midambles included in the data field of the PPDU, and the number of data symbols N included in the data field of the PPDU is determined using the number of midambles SYM , and the number of intermediate synchronization codes used N MA and the number of data symbols N SYM Receive the data field of the PPDU.

[0013] In an embodiment, the first information includes a packet extension (PE) disambiguation bit value b PE-Disambiguity , the number of HE long training field (HE-LTF) values ​​N HE-LTF , HE-LTF duration T including guard interval HE-LTF , Data symbol duration T SYM , and the intermediate synchronization code periodicity M.

[0014] In an embodiment, the first information also includes a preamble duration T according to the PPDU format. PA HE-LTF duration T HE-LTF , and the number of HE-LTF values ​​N HE-LTF .

[0015] In an embodiment, the first information further includes the middle synchronization code duration T MA .

[0016] In an embodiment, the second information includes a length field value L_LENGTH.

[0017] In an embodiment, the number N of midambles is determined MA The number N of intermediate synchronization codes is determined according to the following formula: MA :

[0018]

[0019] When the format of the PPDU is HE multi-user PPDU or HE extended range single-user PPDU format, m is 1, otherwise m is 2, where β is an integer greater than or equal to zero.

[0020] In an embodiment, the number N of midambles is determined MA The number N of intermediate synchronization codes is determined according to the following formula: MA :

[0021]

[0022] When the format of the PPDU is HE multi-user PPDU or HE extended range single-user PPDU format, m is 1, otherwise m is 2, where β is an integer greater than or equal to zero.

[0023] In an embodiment, β is 1.

[0024] In an embodiment, the received data field includes a number N of repetitions and a midamble MA The embodiment then receives the remaining 0 or more remaining consecutive data symbols, wherein the number of data symbols in the plurality of data symbols is equal to the periodicity M of the intermediate synchronization code, and receives the intermediate synchronization code immediately following the plurality of consecutive data symbols. remain equal:

[0025] N remain =N SYM -(M·N MA ). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A wireless network according to an embodiment is shown.

[0027] Figure 2 is a schematic diagram of a wireless device according to an embodiment.

[0028] Figure 3A Components of a wireless device configured to transmit data are shown according to an embodiment.

[0029] Figure 3B Components of a wireless device configured to receive data are shown according to an embodiment.

[0030] Figure 4 The inter-frame space (IFS) relationship is shown.

[0031] Figure 5 The frame transmission process based on carrier sense multiple access / collision avoidance (CSMA / CA) is shown.

[0032] Fig. 6A A High Efficiency (HE) PHY Protocol Data Unit (PPDU) according to an embodiment is shown.

[0033] Figure 6B Table 1 according to an embodiment is shown, which discloses Fig. 6A Additional attributes of the fields of the HE PPDU frame.

[0034] Fig. 7A The format of a high-efficiency (HE) single-user (SU) PPDU according to an embodiment is shown.

[0035] Figure 7B The format of a HE multi-user (MU) PPDU frame according to an embodiment is shown.

[0036] Figure 7C The format of a HE extended range (ER) SU PPDU according to an embodiment is shown.

[0037] Fig.7D The format of a HE trigger-based (TB) PPDU 700D according to an embodiment is shown.

[0038] Figure 8 A trigger frame according to an embodiment is shown.

[0039] Fig. 9 Shown are common information fields according to an embodiment.

[0040] Fig.10 Shown are user information fields according to an embodiment.

[0041] Fig.11 A PPDU used when the Doppler subfield is set to 1 according to an embodiment is shown.

[0042] Fig.12 Signaling of a PPDU format according to an embodiment is shown.

[0043] Fig.13 A process for determining the midamble periodicity M according to the format of the PPDU according to an embodiment is shown.

[0044] Fig.14 A process for determining the midamble periodicity M according to the format of the PPDU according to another embodiment is shown.

[0045] Fig.15 A process for determining the midamble periodicity M according to the format of the PPDU according to another embodiment is shown.

[0046] Fig.16A process for determining the midamble periodicity M according to the format of the PPDU according to another embodiment is shown.

[0047] Fig.17 A PPDU including a midamble according to an embodiment is shown.

[0048] Fig.18 A PPDU including a midamble according to an embodiment is shown.

[0049] Fig.19 Features of a PPDU including a midamble according to another embodiment are shown.

[0050] Fig. 20 A PPDU including a midamble according to another embodiment is shown.

[0051] Fig.21 A process for receiving a PPDU having a data field including a midamble according to an embodiment is shown.

[0052] Fig. 22 A process for receiving a data field of a PPDU including a midamble according to an embodiment is shown. DETAILED DESCRIPTION

[0053] The technology described herein generally relates to wireless networking. More specifically, the technology relates to communication of a PHY protocol data unit (PPDU) including a data field, wherein the data field includes a midamble.

[0054] In the following detailed description, certain illustrative embodiments have been illustrated and described. As will be appreciated by those skilled in the art, these embodiments can be modified in various ways without departing from the scope of the present disclosure. Therefore, the drawings and description should be considered illustrative rather than restrictive. The same reference numerals in the specification represent the same elements.

[0055] Figure 1 A wireless network according to an embodiment is shown. The wireless network includes an infrastructure Basic Service Set (BSS) 100 of a Wireless Local Area Network (WLAN). In an 802.11 WLAN, a BSS provides the basic organizational unit and typically includes an Access Point (AP) and one or more associated stations (STAs).

[0056] The first BSS 100 includes an access point 102 (also referred to as an AP) that wirelessly communicates with first, second, third, and fourth wireless devices (or stations) 104, 106, 108, and 110 (also referred to as stations STA1, STA2, STA3, and STA4, respectively). The wireless devices may each include a media access control (MAC) layer and a physical (PHY) layer according to the IEEE 802.11 standard.

[0057] although Figure 1 It is shown that the first BSS 100 includes only first to fourth stations STA1 to STA4, but the embodiment is not limited thereto and may include a BSS including any number of stations therein.

[0058] The AP 102 is a station, i.e., a STA, configured to control and coordinate functions of the BSS 100. The AP 102 may transmit information to a single station selected from a plurality of stations STA1 to STA4 in the first BSS 100 using a single frame, or may simultaneously transmit information to two or more stations among the stations STA1 to STA4 in the first BSS 100 using a single orthogonal frequency division multiplexing (OFDM) broadcast frame, a single OFDM multi-user multiple input multiple output (MU-MIMO) transmission, a single orthogonal frequency division multiple access (OFDMA) frame, or a single MU-MIMO OFDMA frame.

[0059] The stations STA1 to STA4 may each use a single frame to send data to the AP 102, or use a single frame to send and receive information to and from each other. Two or more of the stations STA1 to STA4 may simultaneously send data to the AP 102 using an uplink (UL) OFDMA frame, a UL MU-MIMO frame, or a UL MU-MIMO OFDMA frame.

[0060] In another embodiment, the AP 102 may not be present, and the stations STA1 to STA4 may be in an ad-hoc network.

[0061] Figure 1 A first downlink (DL) transmission 114 and a first uplink (UL) transmission 112 of a first BSS 100 are shown.

[0062] Each of the stations STA1 to STA4 and the AP 102 includes a processor and one or more transceiver circuits, and may also include a user interface and a display device.

[0063] The processor is configured to generate frames to be sent via the wireless network, process frames received via the wireless network, and execute the protocol of the wireless network. The processor can perform some or all of its functions by executing computer programming instructions stored on a non-transitory computer readable medium.

[0064] A transceiver represents a unit functionally connected to a processor and designed to send and receive frames via a wireless network. A transceiver may comprise a single component that performs both sending and receiving functions, or may comprise two separate components, each performing one of these functions.

[0065] The processors and transceivers of the stations STA1 to STA4 and the AP 102 may be implemented using hardware components, software components, or both, respectively.

[0066] The first AP 102 may be or include a WLAN router, a standalone access point, a WLAN bridge, a lightweight access point (LWAP) managed by a WLAN controller, etc. In addition, a device such as a personal computer, a tablet computer, or a cell phone may also be configured to be able to operate as an AP 102, such as when a cell phone is configured to operate as a wireless "hotspot".

[0067] Each of stations STA1 to STA4 may be or may include a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, an e-book reader, a portable multimedia player (PMP), a portable game console, a navigation system, a digital camera, a digital multimedia broadcasting (DMB) player, a digital audio recorder, a digital audio player, a digital photo recorder, a digital photo player, a digital video recorder, a digital video player, etc.

[0068] The present disclosure may be applied to a WLAN system according to the IEEE 802.11 standard, but the embodiments are not limited thereto.

[0069] In the IEEE 802.11 standard, frames exchanged between stations (including access points) are classified into management frames, control frames, and data frames. A management frame may be a frame for exchanging management information that is not forwarded to a higher layer of a communication protocol stack. A control frame may be a frame for controlling access to a medium. A data frame may be a frame for sending data to be forwarded to a higher layer of a communication protocol stack.

[0070] As specified in applicable standards, the type and subtype of a frame may be identified using a type field and / or a subtype field included in a control field of the frame.

[0071] Figure 2 FIG. 2 is a schematic block diagram of a wireless device 200 according to an embodiment. The wireless or WLAN device 200 may be included in an AP 102 or Figure 1 The WLAN device 200 includes a baseband processor 210, a radio frequency (RF) transceiver 240, an antenna unit 250, a storage device (e.g., memory) 232, one or more input interfaces 234, and one or more output interfaces 236. The baseband processor 210, the memory 232, the input interface 234, the output interface 236, and the RF transceiver 240 can communicate with each other via a bus 260.

[0072] The baseband processor 210 performs baseband signal processing and includes a MAC processor 212 and a PHY processor 222. The baseband processor 210 may utilize a memory 232, which may include a non-transitory computer-readable medium having software (eg, computer program instructions) and data stored therein.

[0073] In an embodiment, the MAC processor 212 includes a MAC software processing unit 214 and a MAC hardware processing unit 216. The MAC software processing unit 214 may implement the first plurality of functions of the MAC layer by executing MAC software, which may be included in the software stored in the memory 232. The MAC hardware processing unit 216 may implement the second plurality of functions of the MAC layer in dedicated hardware. However, the MAC processor 212 is not limited thereto. For example, the MAC processor 212 may be configured to perform the first and second plurality of functions entirely in software or entirely in hardware according to an embodiment.

[0074] The PHY processor 222 includes a transmit signal processing unit (SPU) 224 and a receive SPU 226. The PHY processor 222 implements multiple functions of the PHY layer. Depending on the embodiment, these functions may be performed in software, hardware, or a combination thereof.

[0075] The functions performed by the transmit SPU 224 may include one or more of forward error correction (FEC) encoding, stream parsing to parse into one or more spatial streams, diversity coding to encode a spatial stream into multiple space-time streams, spatial mapping to map the space-time streams to transmit chains, inverse Fourier transform (iFT) calculation, cyclic prefix (CP) insertion to create a guard interval (GI), etc. The functions performed by the receive SPU 226 may include the inverse functions of the functions performed by the transmit SPU 224, such as GI removal, Fourier transform calculation, etc.

[0076] The RF transceiver 240 includes an RF transmitter 242 and an RF receiver 244. The RF transceiver 240 is configured to transmit first information received from the baseband processor 210 to the WLAN, and provide the baseband processor 210 with second information received from the WLAN.

[0077] The antenna unit 250 includes one or more antennas. When multiple-input multiple-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antenna unit 250 may include multiple antennas. In an embodiment, the antennas in the antenna unit 250 may operate as a beamforming antenna array. In an embodiment, the antennas in the antenna unit 250 may be directional antennas, which may be fixed or controllable.

[0078] The input interface 234 receives information from the user, and the output interface 236 outputs information to the user. The input interface 234 may include one or more of a keyboard, a keypad, a mouse, a touch screen, a microphone, etc. The output interface 236 may include one or more of a display device, a touch screen, a speaker, etc.

[0079] As described herein, many functions of the WLAN device 200 may be implemented in hardware or software. Which functions are implemented in software and which functions are implemented in hardware will vary depending on the constraints imposed on the design. These constraints may include one or more of design cost, manufacturing cost, time to market, power consumption, available semiconductor technology, etc.

[0080] As described herein, various electronic devices, circuits, firmware, software, and combinations thereof may be used to implement the functions of the components of the WLAN device 200. In addition, the WLAN device 200 may include other components, such as an application processor, a storage interface, a clock generator circuit, a power supply circuit, etc., which are omitted for brevity.

[0081] Figure 3A Components of a wireless device configured to transmit data according to an embodiment are shown, including a transmit (Tx) SPU (TxSP) 324, an RF transmitter 342, and an antenna 352. In an embodiment, the TxSP 324, the RF transmitter 342, and the antenna 352 correspond to Figure 2 The transmitting SPU 224, the RF transmitter 242 and the antenna of the antenna unit 250.

[0082] The TxSP 324 includes an encoder 300 , an interleaver 302 , a mapper 304 , an inverse Fourier transformer (IFT) 306 , and a guard interval (GI) inserter 308 .

[0083] The encoder 300 receives and encodes input data DATA. In an embodiment, the encoder 300 includes a forward error correction (FEC) encoder. The FEC encoder may include a binary convolutional code (BCC) encoder followed by a puncturing device. The FEC encoder may include a low-density parity check (LDPC) encoder.

[0084] The TxSP 324 may also include a scrambler for scrambling the input data before encoding by the encoder 300 to reduce the probability of long sequences of 0 seconds or 1 second. When the encoder 300 performs BCC encoding, the TxSP 324 may also include an encoder parser for demultiplexing scrambled bits between multiple BCC encoders. If LDPC encoding is used in the encoder, the TxSP 324 may not use an encoder parser.

[0085] The interleaver 302 interleaves bits of each stream output from the encoder 300 to change the order of bits therein. The interleaver 302 may apply interleaving only when the encoder 300 performs BCC encoding, or may output the stream output from the encoder 300 without changing the order of bits therein.

[0086] The mapper 304 maps the bit sequence output from the interleaver 302 to a constellation point. If the encoder 300 performs LDPC encoding, the mapper 304 may perform LDPC tone mapping in addition to the constellation mapping.

[0087] When the TxSP 324 performs MIMO or MU-MIMO transmission, the TxSP 324 may include multiple interleavers 302 and multiple mappers 304 according to the multiple spatial streams (NSS) of the transmission. The TxSP 324 may also include a stream parser for dividing the output of the encoder 300 into blocks, and may send the blocks to different interleavers 302 or mappers 304, respectively. The TxSP 324 may also include a space-time block code (STBC) encoder for extending the constellation points from the spatial stream to multiple space-time streams (NSTS) and a space mapper for mapping the space-time stream to the transmission chain. The spatial mapper may use direct mapping, spatial extension, or beamforming.

[0088] The IFT 306 converts the blocks of constellation points output from the mapper 304 (or, when MIMO or MU-MIMO is performed, from the spatial mapper) into time domain blocks (i.e., symbols) by using an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). If an STBC encoder and a spatial mapper are used, an IFT 306 may be provided for each transmit chain.

[0089] When the TxSP 324 performs MIMO or MU-MIMO transmissions, the TxSP 324 may insert cyclic shift diversity (CSD) to prevent unintentional beamforming. The TxSP 324 may perform the insertion of the CSD before or after the IFT 306. The CSD may be specified for each transmit chain or may be specified for each space-time stream. Alternatively, the CSD may be applied as part of the spatial mapper.

[0090] When the TxSP 324 performs MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0091] GI inserter 308 places a GI in front of each symbol generated by IFT 306. Each GI may include a cyclic prefix (CP) corresponding to a repeated portion of the end of the symbol following the GI. TxSP 324 may optionally perform windowing to smooth the edges of each symbol after inserting the GI.

[0092] The RF transmitter 342 converts the symbols into RF signals and transmits the RF signals via the antenna 352. When the TxSP 324 performs MIMO or MU-MIMO transmission, the GI inserter 308 and the RF transmitter 342 may be provided for each transmission chain.

[0093] Figure 3B Components of a wireless device configured to receive data according to an embodiment are shown, including a receiver (Rx) SPU (RxSP) 326, an RF receiver 344, and an antenna 354. In an embodiment, the RxSP 326, the RF receiver 344, and the antenna 354 may correspond to Figure 2 The receiving SPU 226, the RF receiver 244 and the antenna of the antenna unit 250.

[0094] The RxSP 326 includes a GI remover 318 , a Fourier transformer (FT) 316 , a demapper 314 , a deinterleaver 312 , and a decoder 310 .

[0095] RF receiver 344 receives RF signals via antenna 354 and converts the RF signals into symbols. GI remover 318 removes GI from each symbol. When the received transmission is a MIMO or MU-MIMO transmission, RF receiver 344 and GI remover 318 may be provided for each receive chain.

[0096] The FT 316 converts each symbol (ie, each time domain block) into a frequency domain block of constellation points by using a discrete Fourier transform (DFT) or a fast Fourier transform (FFT). The FT 316 may be provided to each receive chain.

[0097] When the received transmission is a MIMO or MU-MIMO transmission, the RxSP 326 may include a spatial demapper for converting the individual outputs of the FT 316 of the receiver chain into constellation points for multiple space-time streams, and an STBC decoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0098] Demapper 314 demaps the constellation points output from FT 316 or STBC decoder into a bit stream. If the received transmission is encoded using LDPC coding, demapper 314 may further perform LDPC tone demapping before performing constellation demapping.

[0099] The deinterleaver 312 deinterleaves the bits of each stream output from the demapper 314. The deinterleaver 312 may perform deinterleaving only when the received transmission is encoded using BCC encoding, and may otherwise output the stream output by the demapper 314 without performing deinterleaving.

[0100] When the received transmission is a MIMO or MU-MIMO transmission, the RxSP 326 may use multiple demappers 314 and multiple deinterleavers 312 corresponding to the multiple spatial streams of the transmission. In this case, the RxSP 326 may also include a stream inverse parser for combining the streams output from the deinterleavers 312.

[0101] The decoder 310 decodes the stream output from the deinterleaver 312 or the stream inverse parser. In an embodiment, the decoder 312 includes an FEC decoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

[0102] RxSP 326 may also include a descrambler for descrambling the decoded data. When decoder 310 performs BCC decoding, RxSP 326 may also include an encoder inverse parser for multiplexing data decoded by multiple BCC decoders. When decoder 310 performs LDPC decoding, RxSP 326 may not use the encoder inverse parser.

[0103] Before transmitting, a wireless device such as wireless device 200 will assess the availability of the wireless medium using a clear channel assessment (CCA). If the medium is occupied, the CCA may determine that it is busy, and if the medium is available, the CCA determines that it is idle.

[0104] The PHY entity for IEEE Standard 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In the OFDM or OFDMA physical (PHY) layer, STAs are able to send and receive physical layer protocol data units (PPDUs) that conform to the mandatory PHY specifications. The PHY specifications define a set of modulation and coding schemes (MCS) and the maximum number of spatial streams. Some PHY entities define downlink (DL) and uplink (UL) multi-user (MU) transmissions with a maximum number of space-time streams (STS) per user and employing up to a predetermined total number of STSs.

[0105] Figure 4 The inter-frame space (IFS) relationship is shown. Figure 4A short IFS (SIFS), a point coordination function (PCF) IFS (PIFS), a distributed coordination function (DCF) IFS (DIFS), and an arbitration IFS corresponding to an access category (AC) 'i' (AIFS[i]) are shown. Figure 4 The time slots are also shown.

[0106] The data frame is used for transmission of data forwarded to a higher layer. If a DIFS in which a medium has been idle has passed, the WLAN device transmits the data frame after performing a backoff.

[0107] Management frames are used to exchange management information, which is not forwarded to higher layers. Subtype frames of management frames include beacon frames, association request / response frames, probe request / response frames, and authentication request / response frames.

[0108] Control frames are used to control access to the medium. Subtypes of control frames include request to send (RTS), clear to send (CTS), and acknowledgement (ACK).

[0109] When the control frame is not a response frame of another frame, if DIFS in which the medium has been idle has passed, the WLAN device sends the control frame after performing backoff. When the control frame is a response frame of another frame, the WLAN device sends the control frame after SIFS has passed without performing backoff or checking whether the medium is idle.

[0110] After performing backoff, if the AIFS (AIFS[AC]) for the associated access category (AC) has passed, a WLAN device supporting a quality of service (QoS) function (i.e., a QoS station) may transmit the frame. When transmitted by a QoS station, any frame that is not a response frame among a data frame, a management frame, and a control frame may use the AIFS[AC] of the AC of the transmitted frame.

[0111] When a WLAN device that is ready to transmit a frame finds that the medium is busy, the WLAN device can perform a backoff procedure. In addition, a WLAN device operating according to IEEE 802.11n and 802.11ac standards can also perform a backoff procedure when the WLAN device infers that the frame transmission of the WLAN device has failed.

[0112] The backoff procedure includes determining a random backoff time consisting of N backoff slots, each backoff slot having a duration equal to one slot time, and N is an integer greater than or equal to zero. The backoff time can be determined based on the length of the contention window (CW). In an embodiment, the backoff time can be determined based on the AC of the frame. All backoff slots occur following a DIFS or extended IFS (EIFS) period as described below, during which the medium is determined to be idle for the duration of the period.

[0113] When the WLAN device detects no medium activity for the duration of a particular backoff slot, the backoff procedure decrements the backoff time by the slot time. When the WLAN determines that the medium is busy during the backoff slot, the backoff procedure is suspended until the medium is again determined to be idle for the duration of the DIFS or EIFS period. When the backoff timer reaches zero, the WLAN device may perform a transmission or retransmission of the frame.

[0114] The back-off procedure operates so that when multiple WLAN devices postpone and execute the back-off procedure, each WLAN device can select a back-off time using a random function, and the WLAN device selecting the minimum back-off time can win the competition, thereby reducing the probability of conflict.

[0115] Figure 5 A frame transmission process based on Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) for avoiding collision between frames in a channel according to an embodiment is shown. Figure 5 A first station STA1 transmitting data, a second station STA2 receiving data, and a third station STA3 located in an area that can receive frames transmitted from STA1, frames transmitted from the second station STA2, or both are shown. The stations STA1, STA2, and STA3 may be WLAN devices.

[0116] STA1 may determine whether the channel is busy by carrier sensing. STA1 may determine the channel occupancy based on the energy level in the channel or the autocorrelation of the signal in the channel, or may determine the channel occupancy by using a network allocation vector (NAV) timer.

[0117] After determining that the channel is not used by other devices during the DIFS period (i.e., the channel is idle) (and performing a backoff if necessary), STA1 may send a ready-to-send (RTS) frame to the second station STA2. Upon receiving the RTS frame, after SIFS, the second station STA2 may send a clear-to-send (CTS) frame as a response to the RTS frame. If dual CTS is enabled and the second station STA2 is an AP, the AP may send two CTS frames in response to the RTS frame: a first CTS frame in a conventional non-HT format, and a second CTS frame in a HT format.

[0118] When the third station STA3 receives the RTS frame, it may use the duration information included in the RTS frame to set the NAV timer of the third station STA3 for the transmission duration of the subsequently transmitted frame (e.g., the duration of SIFS+CTS frame duration+SIFS+data frame duration+SIFS+ACK frame duration). When the third station STA3 receives the CTS frame, it may use the duration information included in the CTS frame to set the NAV timer of the third station STA3 for the transmission duration of the subsequently transmitted frame. When a new frame is received before the NAV timer expires, the third station STA3 may update the NAV timer of the third station STA3 by using the duration information included in the new frame. The third station STA3 does not attempt to access the channel until the NAV timer expires.

[0119] When STA1 receives the CTS frame from the second station STA2, it may transmit the data frame to the second station STA2 after SIFS has passed from the time when the CTS frame has been completely received. After successfully receiving the data frame, the second station STA2 may send an ACK frame as a response to the data frame after SIFS has passed.

[0120] When the NAV timer expires, the third station STA3 may determine whether the channel is busy using carrier sensing. Upon determining that the channel is not used by other devices during DIFS after the NAV timer has expired, the third station STA3 may attempt to access the channel after a contention window according to a backoff procedure has passed.

[0121] When dual CTS is enabled, a station that has obtained a transmission opportunity (TXOP) and has no data to send can send a CF-End frame to shorten the TXOP. An AP that receives a CF-End frame with the AP's basic service set identifier (BSSID) as the destination address can respond by sending two more CF-End frames (i.e., a first CF-End frame using space-time block coding (STBC) and a second CF-End frame using non-STBC). A station that receives a CF-End frame resets its NAV timer to 0 at the end of the PPDU containing the CF-End frame.

[0122] Figure 5 The second station STA2 is shown sending an ACK frame to acknowledge that the receiver successfully received the frame.

[0123] The PHY entity for IEEE Standard 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In the OFDM or OFDMA physical (PHY) layer, a STA can send and receive a PHY protocol data unit (PPDU) that complies with the mandatory PHY specification.

[0124] The PHY entity may provide support for 20 MHz, 40 MHz, 80 MHz and 160 MHz contiguous channel widths, and provide support for 80+80 MHz non-contiguous channel widths.Each channel includes a number of subcarriers, which may also be referred to as tones.

[0125] The PHY entity may define fields denoted as legacy signal (L-SIG), signal A (SIG-A), and signal B (SIG-B), within which some necessary information about the attributes of the PHY service data unit (PSDU) is conveyed. For example, a high efficiency (HE) PHY entity may define an L-SIG field, a HE signal A (HE-SIG-A) field, and a HE signal B (HE-SIG-B) field.

[0126] For completeness and brevity, the following description refers to OFDM-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP HE STA and an AP refers to a HE AP.

[0127] In IEEE standard 802.11ac, the SIG-A and SIG-B fields are referred to as VHT SIG-A and VHT SIG-B fields. Hereinafter, the IEEE standard 802.11ax SIG-A and SIG-B fields are referred to as HE-SIG-A and HE-SIG-B fields, respectively.

[0128] Fig. 6A A HE PPDU 600 according to an embodiment is shown. A transmitting station generates and transmits a HE PPDU frame 600 to one or more receiving stations. A receiving station receives, detects and processes the HE PPDU frame 600.

[0129] The HE PPDU frame 600 includes a legacy short training field (L-STF) 602, a legacy (i.e., non-high throughput (non-HT)) long training field (L-LTF) 604, a legacy signal (L-SIG) field 606, which together include the legacy preamble 601 and a repeated L-SIG field (RL-SIG) 608. The L-STF 604 of the HE PPDU has a periodicity of 0.8 μs with 10 cycles.

[0130] The HE PPDU frame 600 also includes a HE signal A (HE-SIG-A) field 610, a HE signal B (HE-SIG-B) field 612, a HE-STF 614, a HE-LTF 616, and a HE-data field 618. In an embodiment, the HE PPDU frame 600 includes a plurality of HE-SIG-B fields 612 corresponding to different channels, and a corresponding plurality of HE-STFs 614, HE-LTFs 616, and HE-data fields 618 corresponding to different channels or resource units.

[0131] When the legacy preamble 601, the RL-SIG field 608, the HE-SIG-A field 610, and the HE-SIG-B field 612 are present, they comprise a first portion of the HE PPDU frame 600. In an embodiment, the first portion of the HE PPDU frame 600 is decoded using a 64-element discrete Fourier transform (DFT), and the first portion has a basic subcarrier spacing of 312.5 KHz.

[0132] The HE-SIG-A field 610 is repeated on each 20 MHz segment after the legacy preamble to indicate common control information. The HE-SIG-A field 610 includes a plurality of OFDM HE-SIG-A symbols 620, each symbol having a duration of 4 μs (including a guard interval (GI)). Depending on the type of the HE PPDU 600, the number of HE-SIG-A symbols 620 in the HE-SIG-A field 610 is determined to be 2 or 4. In an embodiment, the HE-SIG-A field 610 of the HE extended range single user (SU) PPDU includes 4 HE-SIG-A symbols 620, while the HE-SIG-A field 610 of other types of HE PPDUs includes 2 HE-SIG-A symbols 620.

[0133] The HE-SIG-B field 612 is included in the HE multi-user (MU) PPDU. The HE-SIG-B field 612 includes a plurality of OFDM HE-SIG-B symbols 622, each symbol having a duration of 4 μs including a GI. In an embodiment, one or more of the HE SU PPDU, HE triggered-based PPDU, and HE extended range SU PPDU do not include the HE-SIG-B field 612. The number of HE-SIG-B symbols 622 in the HE-SIG-B field 612 is determined by the N in the HE-SIG-A field 610. HE-SIGB Indicative and variable.

[0134] When the bandwidth of the HE PPDU 600 is 40 MHz or higher, the HE-SIG-B field 612 may be sent in the first HE-SIG-B channel 1 and the second HE-SIG-B channel 2. The HE-SIG-B field in the HE-SIG-B channel 1 is referred to as the HE-SIG-B1 field, and the HE-SIG-B field in the HE-SIG-B channel 2 is referred to as the HE-SIG-B2 field. The HE-SIG-B1 field and the HE-SIG-B2 field are transmitted using different 20 MHz bandwidths of the HE PPDU 600 and may contain different information. In this document, the term "HE-SIG-B field" may refer to the HE-SIG-B field of a 20 MHz PPDU, or to either or both of the HE-SIG B1 field or the HE-SIG B2 field of a 40 MHz or higher PPDU.

[0135] The HE-STF 614 of a non-trigger-based PPDU has a periodicity of 0.8 μs with a period of 5. A non-trigger-based PPDU is a PPDU that is not sent in response to a trigger frame. The HE-STF 614 of a trigger-based PPDU has a periodicity of 1.6 μs with a period of 5. A trigger-based PPDU includes a UL PPDU that is sent in response to a corresponding trigger frame.

[0136] The HE-LTF 616 includes one or more OFDM HE-LTF symbols 626, each having a duration of 12.8 μs plus a guard interval (GI). The HE PPDU frame 600 can support 2xLTF mode and 4xLTF mode. In 2xLTF mode, the HE-LTF symbol 626 not including the guard interval (GI) is equivalent to modulating every other tone in the 12.8 μs OFDM symbol not including the GI, and then removing the second half of the OFDM symbol in the time domain. The number of HE-LTF symbols 626 in the HE-LTF field 616 is determined by N. HE-LTF indicates, and is equal to 1, 2, 4, 6, or 8.

[0137] The HE-data field 618 includes one or more OFDM HE-data symbols 628, each symbol having a duration of 12.8 μs plus a guard interval (GI). The number of HE-data symbols 628 in the HE-data field 618 is represented by N DATA Instructions, and are variable.

[0138] Figure 6B Table 1 according to an embodiment is shown, which indicates Fig. 6A Additional attributes of the fields of the HE PPDU frame 600.

[0139] For completeness and brevity, the following description refers to OFDMA-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP HE STA and an AP refers to a HE AP.

[0140] In the present disclosure, multi-user (MU) transmission refers to the case where multiple frames are sent to or from multiple STAs simultaneously using different resources, where examples of different resources are different frequency resources in OFDMA transmission and different spatial streams in MU-MIMO transmission. Therefore, DL-OFDMA, DL-MU-MIMO, UL-OFDMA, and UL-MU-MIMO are examples of MU transmission.

[0141] For several reasons, IEEE Std 802.11ax may require more protection mechanisms for MU transmissions than DL MU-MIMO defined in IEEE Std 802.11ac. The first reason is that the IEEE Std 802.11ax operating scenario is different in that it includes a denser wireless environment and outdoor support. Also, the coverage area of ​​an IEEE Std 802.11ax BSS may be physically larger than an IEEE Std 802.11ac BSS. Both of these factors create a need for more robust protection mechanisms.

[0142] The second reason is that IEEE standard 802.11ax supports not only DL MU transmission, but also UL MU transmission. In the case of UL MU transmission, since the number of frames that may be transmitted from each STA is larger, more protection is needed to avoid being affected by other nearby transmitting STAs. Another reason is that in the IEEE standard 802.11ax environment, the AP may want to have more control over the medium by using a scheduled access mechanism, which may involve more frequent use of OFDMA / MU-MIMO transmissions.

[0143] The UL MU PPDU (MU-MIMO or OFDMA) is sent as a response to a trigger frame sent by the AP. The trigger frame may have sufficient STA-specific information and corresponding assigned resource units to identify the STA that should send the UL MU PPDU.

[0144] Figures 7A to 7D The four HE PPDU formats shown in FIG. 8 are defined by IEEE standard 802.11ax: HE SU PPDU, HE MU PPDU, HE extended range SU PPDU, and HE trigger-based (TB) PPDU. Figures 7A to 7D Elements with reference characters of the form 7xx in are essentially similar to Fig. 6A Elements having reference characters in the form of 6xx are not described herein and their description is omitted for brevity. Figures 7A to 7D The frame shown in FIG. 7 also includes a packet extension (PE) 730 .

[0145] Fig. 7A The format of a high-efficiency (HE) single-user (SU) PPDU 700A according to an embodiment is shown. The HE SU PPDU 700A is used for SU transmission, and in this format, the HE-SIG-A field 710 is not repeated. The HE SU PPDU 700A does not have a HE-SIG-B field.

[0146] Figure 7B The format of a HE multi-user (MU) PPDU frame 700B according to an embodiment is shown. This format is used for MU transmissions that are not responses to trigger frames. In this format, a HE-SIG-B field 712 is present. The number of symbols in the HE-SIG-B field 712 may be determined based on information in the HE-SIG-A field 710 (e.g., a HE-SIG-B compression indication), the bandwidth of the PPDU frame 700B, and the number of user fields indicated in the common field of the HE-SIG-B field 712 when a common field is present in the HE-SIG-B field 712.

[0147] Figure 7C The format of the HE extended range (ER) SU PPDU 700C according to an embodiment is shown. This format is used for SU transmission, and the HE-SIG-A field 710 is repeated in this format (as a first HE-SIG-A field 710-1 and a second HE-SIG-A field 710-2).

[0148] Fig.7D The format of a HE trigger-based (TB) PPDU 700D according to an embodiment is shown.

[0149] Figure 8 A trigger frame 800 according to an embodiment is shown. The trigger frame 800 is used to allocate resources for UL MU transmission and request UL MU transmission to be performed after the PPDU carrying the trigger frame (as a response to the PPDU). The trigger frame also carries other information required for the responding STA to send UL MU transmission.

[0150] The trigger frame 800 includes a frame control field 802, a duration field 804, a receiver address (RA) field 806, a transmitter address (TA) field 808, a common information field 810, one or more user information fields 812-x, optional padding 814, and a frame check sequence (FCS) field 816.

[0151] The value of the frame control field 802 indicates that the trigger frame 800 is a trigger frame. The value of the duration field 804 indicates the length of the trigger frame 800. The value of the RA field 806 of the trigger frame is the address of the receiving station or the broadcast address corresponding to one or more receiving stations. The value of the TA field 804 of the trigger frame is the address of the station sending the trigger frame.

[0152] Fig. 9 The public information field 910 is shown according to an embodiment. The public information field 910 is suitable for use as Figure 8 The common information field 810 of the trigger frame 800 of FIG. The common information field 910 includes a trigger type subfield 922, a length subfield 924, a concatenation information subfield 926, a carrier sense (CS) required subfield 928, a bandwidth (BW) subfield 930, a guard interval (GI) and a long training field (LTF) type subfield 932, a HE-LTF symbol number subfield 936, a space-time block coding subfield 938, a spatial reuse subfield 946, a Doppler subfield 948, and a HE-SIG-A reserved subfield 950. In some trigger frames, the common information field 910 also includes a trigger-dependent common information subfield 954.

[0153] A trigger type subfield 922 indicating the type of the trigger frame. Depending on the type of the trigger frame, the trigger frame may include an optional type-specific trigger dependent common information field 954 and an optional type-specific per-user information field (in each of the per-user information fields of the trigger frame).

[0154] The length subfield 924 indicates the value of the L-SIG length field of the HE TB PPDU transmitted in response to the trigger frame. The concatenation indication subfield 926 indicates that the subsequent trigger frame follows the current trigger frame when set to 1, otherwise it has a value of 0.

[0155] The CS Required subfield 928 is set to 1 to indicate that the station identified in the Per-User Information field of the trigger frame needs to use Energy Detection (ED) to sense the medium and consider the medium status and NAV when determining whether to respond to the trigger frame. The CS Required subfield 928 is set to 0 to indicate that the station identified in the Per-User Information field does not need to consider the medium status or NAV when determining whether to respond to the trigger frame.

[0156] The BW subfield 930 indicates the bandwidth in the HE-SIG-A field of the HE TB PPDU transmitted in response to the trigger frame. The CP and LTF type subfield 932 indicates the CP and HE-LTF type of the HE TB PPDU transmitted in response to the trigger frame.

[0157] The HE-SIG-A reserved subfield 950 indicates the contents of the HE-SIG-A field of the HE TB PPDU sent in response to the trigger frame. In an embodiment, all values ​​in the HE-SIG-A reserved subfield are set to 1.

[0158] The spatial reuse (SR) subfield 946 provides spatial reuse information. For communications using 20 MHz BW, the SR subfield 946 provides one SR field corresponding to the entire 20 MHz, and the other 3 fields indicate the same value. For communications using 40 MHz BW, the SR subfield 946 provides two SR fields corresponding to each 20 MHz, and the other 2 fields indicate the same value. For communications using 80 MHz BW, the SR subfield 946 provides four SR fields corresponding to each 20 MHz, respectively. For communications using 160 MHz BW, the SR subfield 946 provides four SR fields corresponding to each 40 MHz, respectively.

[0159] The Doppler subfield 948 supports adequate performance even in outdoor mobility use cases. When the Doppler subfield 948 indicates a first value (e.g., set to 1), the PPDU sent in response to a trigger frame including the common information field 90 includes a midamble field consisting of a plurality of HE-LTFs, wherein each midamble periodicity (M) data symbol is inserted into the plurality of HE-LTFs, as described below.

[0160] In some embodiments of the present disclosure, the common information field 910 may include a midamble interval (M) field 952 described below, which indicates the number of data symbols between midasmbles when the Doppler subfield 948 has a value of 1.

[0161] Fig.10 A user information field 1012 is shown according to an embodiment. The user information field 1012 is suitable for use as Figure 8 The user information field 1012 includes a 12-bit user identifier, which indicates an association ID (AID12) subfield 1020, a resource unit (RU) allocation subfield 1022, a coding type subfield 1024, an MCS subfield 1026, a dual carrier modulation (DCM) subfield 1028, and a spatial stream (SS) allocation subfield 1030. In some trigger frames, the user information field 1012 may include a trigger-dependent user information subfield 1036.

[0162] The user identifier (AID12) subfield 1020 indicates the association identifier (AID) of the station to which the resource unit (RU) is allocated, where one or more MPDUs are sent in the HE TB PPDU sent in response to the trigger frame. The RU allocation subfield 1022 indicates the RU to be used to send the HE TB PPDU of the station identified by the user identifier subfield. The first bit of the RU allocation subfield 1022 can indicate whether the allocated RU is located in the primary or non-primary 80 MHz. According to the IEEE standard 802.11ax OFDMA parameter set (numerology), the subsequent seven bits of the RU allocation subfield 1022 are indexed as one of the RUs and mapped to the RU allocation.

[0163] The coding type subfield 1024 indicates the coding type of the HE TB PPDU sent in response to the trigger frame of the station identified by the user identifier subfield 1020, and is set to 0 for BCC and 1 for LDPC. The MCS subfield 1026 indicates the MCS of the HE TB PPDU sent by the station identified by the user identifier field in response to the trigger frame.

[0164] The dual carrier modulation (DCM) subfield 1028 indicates the dual carrier modulation of the HE TB PPDU sent in response to the trigger frame by the station identified by the user identifier field 1020. A value of 1 indicates that the HE TB PPDU should use DCM, while a value of 0 indicates that DCM should not be used.

[0165] The spatial stream (SS) allocation subfield 1030 indicates the spatial stream of the HE TB PPDU that the station identified by the user identifier field 1020 transmits in response to the trigger frame.

[0166] Fig.11 1 shows a PPDU 1100 used when the Doppler subfield 948 is set to 1 according to an embodiment. In the PPDU format 1100, as described below, one or more HE-LTFs 1106 are inserted every (M) data symbols of the midamble period of the transmission. M The HE-LTF 1106 in each midamble field M The number is equal to the HE-LTF 1106 in the preamble of the PPDU P The number of HE-LTF 1106 M and HE-LTF 1106 P They are defined as the middle synchronization code HE-LTF and the preamble code HE-LTF respectively.

[0167] The PPDU 1100 includes a first portion 1102 corresponding to the first portion of the PPDU 600 of FIG. 6. The first portion 1102 is followed by a HE-STF 1104 and one or more preamble HE-LTFs 1106. P The first part 1102, HE-STF 1104 and one or more preamble codes HE-LTF 1106 P Corresponding to the preamble code of PPDU 1100.

[0168] After the preamble, the PPDU 1100 includes a first data portion 1108-1, which includes M data symbols. After the first data portion 1108-1, the PPDU 1100 includes a first midamble, which includes one or more midambles HE-LTF 1106. M The duration of the first intermediate synchronization code is the intermediate synchronization code duration T MA .

[0169] After the first midamble, the PPDU 1100 includes a second data portion 1108-2, the second data portion 1108-2 including M data symbols. After the second data portion 1108-2, the PPDU 1100 includes a second midamble, the second midamble including one or more midamble HE-LTF 1106 M The duration of the second intermediate synchronization code is the intermediate synchronization code duration T MA .

[0170] After the second midamble, the PPDU 1100 includes a third data portion 1108-3 including the remaining data symbols of the PPDU 1100. After the third data portion 1108-3, the PPDU 1100 includes a packet extension 1110.

[0171] In some embodiments of the present disclosure, the value of M is determined using information in a common information field of a trigger frame requesting a PPDU.

[0172] Fig.12 Signaling of a PPDU format according to an embodiment is shown. Fig.12A first PPDU 1200a, a second PPDU 1200b, and a third PPDU 1200c are shown, each having a different format. Each PPDU includes at least one L-SIG field 1202, a repeated L-SIG (RL-SIG) field 1204, at least a first HE-SIG-A symbol 1206-1 and a second HE-SIG-A symbol 1206-2, and a HE-STF 1210. In a device operating according to IEEE Standard 802.11ax, the device can detect the format of the PPDU based on the value of the length field included in the L-SIG field 1202 and the rotated constellation of the initial symbol of the HE-SIG-A field.

[0173] exist Fig.12 In , the symbol with a horizontal bar below it is modulated using binary phase shift keying (BPSK). The symbol with a vertical bar directly below it is modulated using quadrature binary phase shift keying (QBPSK), i.e., rotated BPSK.

[0174] If the value of the length field in the L-SIG field 1202 is equal to 1 modulo 3, the detected PPDU is a HE SUPPDU (bit B0 of the HE-SIG-A field = 1) or a HE trigger-based PPDU (bit B0 of the HE-SIG-A field = 0). Fig.12 In the embodiment, PPDU 1200a is a HE SU PPDU or a HE TB PPDU.

[0175] If the value of the length field in the L-SIG field 1202 is equal to 2 modulo 3, the PPDU format is a HE extended range SU PPDU (indicated by the second HE-SIG-A symbol 1206-2 modulated using QBPSK) or a HE MU PPDU (indicated by the second HE-SIG-A symbol 1206-2 modulated using BPSK). Fig.12 In the embodiment, PPDU 1200b is a HE extended range SUPPDU and includes third and fourth HE-SIG-A symbols 1206-3 and 1206-4 modulated using BPSK, PPDU 1200a is a HE MU PPDU and includes a HE-SIG-B field 1208, and HE-SIG-B field 1208 includes multiple symbols.

[0176] Embodiments include a process for inserting a midamble into a PPDU according to the PPDU format, and a process for determining the location to insert the midamble in the PPDU once the PPDU format is detected.How the midamble is inserted into the HEPPDU may differ depending on the format of the PPDU.

[0177] Typically, information sent using a higher data rate (e.g., a higher MCS) is more susceptible to adverse effects associated with a mobility environment. Therefore, when using a higher MCS rate, introducing an intermediate synchronization code field according to a small intermediate synchronization code periodicity M can achieve compensation for phase drift, thereby improving performance.

[0178] Fig.13 A process 1300 for determining a midamble periodicity M according to a format of a PPDU according to an embodiment is shown. For example, the process 1300 may be used when the Doppler subfield of the common information field of a trigger frame is set to 1. In this case, the process 1300 may be used to determine a midamble periodicity M of a PPDU sent in response to the trigger frame.

[0179] At S1302, the process 1300 determines whether the PPDU format is any one of the HE SU, HE SU ER, or HE UL MU formats. For the received PPDU, the PPDU format may be determined based on one or more of the length in the L-SIG field, the modulation of the second symbol of the HE-SIG-A field, and the B0 bit of the HE-SIG-A field. In response to the PPDU format being the HE SU, HE SU ER, or HE UL MU format, at S1302, the process 1300 proceeds to S1312; otherwise, at S1302, the process 1300 proceeds to S1304.

[0180] At S1304, the process 1300 determines whether the PPDU format is a multi-user HE DL MU format. For the received PPDU, the PPDU format may be determined based on the length in the L-SIG field and the modulation of the second symbol of the HE-SIG-A field. In response to the PPDU format being a multi-user HE DL MU format, at S1304, the process 1300 proceeds to S1314; otherwise, at S1304, the process 1300 proceeds to S1306.

[0181] At S1306, the process 1300 determines whether the PPDU format is a HE trigger-based (TB) format for the PPDU. In response to the PPDU format being a HE TB format, at S1306, the process 1300 proceeds to S1316; otherwise, at S1306, the process 1300 exits.

[0182] At S1312, the process 1300 determines the midamble periodicity M according to the MCS of the PPDU and then exits.

[0183] At S1314, the process 1300 determines the midamble periodicity M according to the highest MCS among the corresponding MCS values ​​of the STAs assigned to participate in the MU PPDU, and then exits.

[0184] At S1316 , the process 1300 determines the midamble periodicity M according to a predetermined value without considering the value of the assigned MCS in the trigger frame requesting the STA to perform UL MU transmission, and then exits.

[0185] In the embodiment, as previously referred to Fig. 9 As described above, the midamble periodicity M for the trigger-based PPDU may be signaled to all STAs participating in the TB PPDU in a field of a trigger frame requesting a TB PPDU.

[0186] Reference Fig. 9 When the Doppler subfield 948 is set to a first state (e.g., 1), the midamble periodicity (M) subfield 952 has a value corresponding to the number of data symbols between midambles. When the Doppler subfield 948 is set to a second state (e.g., 0), the midamble periodicity (M) subfield 952 is reserved.

[0187] Fig.14 A process 1400 for determining the midamble periodicity M according to the format of the PPDU according to another embodiment is shown. For example, the process 1400 may be used when the Doppler subfield of the common information field of the trigger frame is set to 1, in which case the process 1500 may be used to determine the midamble periodicity M of the PPDU sent in response to the trigger frame.

[0188] At S1402, the process 1400 determines whether the PPDU format is a HE SU format or a HE SU ER format. In response to the PPDU format being a HE SU or HE SU ER format, at S1402, the process 1400 proceeds to S1412; otherwise, at S1402, the process 1400 proceeds to S1404.

[0189] At S1404, the process 1400 determines whether the PPDU format is a multi-user HE MU format (UL or DL). In response to the PPDU format being a multi-user HE MU format, at S1404, the process 1400 proceeds to S1414; otherwise, at S1404, the process 1400 proceeds to S1406.

[0190] At S1406, the process 1400 determines whether the PPDU format is the HE TB format of the PPDU. In response to the PPDU format being the HE TB format, at S1406, the process 1400 proceeds to S1416; otherwise, at S1406, the process 1400 exits.

[0191] At S1412, the process 1400 determines the midamble periodicity M according to the MCS of the PPDU and then exits.

[0192] At S1414, the process 1400 determines the midamble periodicity M according to the highest MCS among the MCS values ​​of the STAs assigned to participate in the MU PPDU, and then exits. At S1414, when only one STA is assigned to participate in the MU PPDU (e.g., ULMU PPDU), the process 1400 determines the midamble periodicity M according to the MCS of only one STA, and then exits.

[0193] At S1416 , the process 1400 determines the midamble periodicity M according to a predetermined value without considering the value of the assigned MCS in the trigger frame requesting the STA to perform UL MU transmission, and then exits.

[0194] Fig.15 A process 1500 for determining a midamble periodicity M based on a format of a PPDU according to another embodiment is shown.

[0195] At S1502, the process 1500 determines whether the PPDU format is a HE SU format or a HE SU ER format. In response to the PPDU format being a HE SU or HE SU ER format, at S1502, the process 1500 proceeds to S1512; otherwise, at S1502, the process 1500 proceeds to S1504.

[0196] At S1504, the process 1500 determines whether the PPDU format is a multi-user HE MU format (UL or DL). In response to the PPDU format being a multi-user HE MU format, at S1504, the process 1500 proceeds to S1516; otherwise, at S1504, the process 1500 proceeds to S1506.

[0197] At S1506, the process 1500 determines whether the PPDU format is a HE trigger-based (TB) format for the PPDU. In response to the PPDU format being a HE TB format, at S1506, the process 1500 proceeds to S1516; otherwise, at S1506, the process 1500 exits.

[0198] At S1512, the process 1500 determines the midamble periodicity M according to the MCS of the PPDU and then exits.

[0199] At S1516, the process 1500 determines the midamble periodicity M according to a predetermined value regardless of any MCS value, and then exits.

[0200] Fig.16A process 1600 is shown for determining a midamble periodicity M based on the format of a PPDU according to another embodiment. The process 1600 may be used when the Doppler subfield indicates the presence of a midamble in the PPDU.

[0201] At S1602, the process 1600 determines whether the PPDU format is a first format. In an embodiment, the first format includes a HE SU format. In an embodiment, the first format includes a HE ER SU format. In an embodiment, the first format includes a single-user HE UL MU format. In response to the PPDU format being the first format, at S1602, the process 1600 proceeds to S1612; otherwise, at S1602, the process 1600 proceeds to S1604.

[0202] At S1604, the process 1600 determines whether the PPDU format is a second format. In an embodiment, the second format includes a HE MU format. In an embodiment, the second format includes a HE DL MU format for more than one user. In response to the PPDU format being the second format, at S1604, the process 1600 proceeds to S1614; otherwise, at S1604, the process 1600 proceeds to S1606.

[0203] At S1606, the process 1600 determines whether the PPDU format is a third format. In an embodiment, the third format includes an HE TB format. In an embodiment, the third format includes an HE MU format. In response to the PPDU format being the third format, at S1606, the process 1600 proceeds to S1616; otherwise, at S1606, the process 1600 proceeds to S1608.

[0204] At S1608, the process 1600 determines whether the PPDU format is a fourth format. In an embodiment, the fourth format includes an HE TB format. In response to the PPDU format being the fourth format, at S1608, the process 1600 proceeds to S1618; otherwise, at S1608, the process 1600 exits.

[0205] At S1612, the process 1600 determines the midamble periodicity M according to the MCS of the PPDU and then exits.

[0206] At S1614, the process 1600 determines the midamble periodicity M according to the highest value of the MCS values ​​of all the assigned STAs in the PPDU. In an embodiment, only one STA may be assigned. Then, the process 1600 exits.

[0207] At S1616, the process 1600 determines the midamble periodicity M according to a predetermined value, regardless of any MCS value, and then exits.

[0208] At S1618, the process 1600 determines the midamble periodicity M according to the value indicated in the frame requesting the STA to send a PPDU in response to the frame, and then exits. In an embodiment, the request frame may be a trigger frame.

[0209] In a first embodiment, for any one of the HE SU PPDU, HE SU extended range PPDU, and ULHE PPDU for one user transmission, when the Doppler subfield is set to a first state indicating that the PPDU is transmitted with the midamble, the HE PPDU format is considered when determining the midamble periodicity M. According to the MCS value of the PPDU, the transmitter inserts the midamble field after each midamble periodicity M encoded OFDM data symbols. Each midamble field can be used to perform channel estimation on the data symbol following the midamble field. When the PPDU is received, once the receiver correctly decodes the MCS value in the PHY preamble of the PPDU, the position and length of the midamble field can be determined.

[0210] In DL MU transmissions with STAs assigned different MCS values, the midamble fields may not be aligned for resource blocks allocated to the respective STAs, and as a result, the FFT windows may not be aligned across resource blocks, which may increase implementation complexity. The MCS value for each assigned STA may be determined collectively by all STAs because the HE-SIG-B field that conveys the MCS value to the STA is not beamformed.

[0211] In an embodiment, for a DL HE MU PPDU targeting more than one user, when the Doppler subfield is set to a first state indicating that the PPDU is transmitted with a midamble, the HE PPDU format is considered when determining the midamble periodicity M. The transmitter inserts the midamble field after M OFDM data symbols per midamble periodicity according to the maximum MCS value among the STAs participating in the DL HE MU PPDU. Each midamble field can be used to perform channel estimation for the data symbol following the midamble field. When the PPDU is received, once the receiver correctly decodes all MCS values ​​for each STA, the position and length of the midamble field can be determined based on the maximum MCS value among the STAs.

[0212] In UL MU transmission with STAs assigned different MCS values, the midamble fields may not be aligned for resource blocks allocated to the respective STAs, and as a result, the FFT windows may not be aligned across resource blocks, which may increase implementation complexity. If all midambles are fed from all users in the UL MU transmission end at the same time, the implementation of the AP may be made easier.

[0213] In an embodiment, for a UL HE MU PPDU, when the Doppler subfield is set to a first state indicating that the PPDU is transmitted with a midamble, the HE PPDU format is considered when determining the midamble periodicity M of the HE triggered (TB) PPDU for UL HE MU transmission. Each STA determines all MCS values ​​in the per-user information field of the trigger frame. The responding STA inserts the midamble field at M data symbols per midamble periodicity based on the maximum MCS value among the assigned STAs. When the AP receives the HE TB PPDU from the assigned STA, the position and length of the midamble field may be determined according to the maximum MCS value among the assigned STAs.

[0214] In an embodiment, for a UL HE MU PPDU, when the Doppler subfield of the received trigger frame is set to a first state indicating that the PPDU is transmitted with a midamble, the HE PPDU format is considered when determining the midamble periodicity M for the HETB PPDU transmitted in response to the trigger frame. The midamble periodicity M is implemented to have a predetermined value so that each STA does not need to see all MCS values ​​in the per-user information field of the trigger frame. The responding STA inserts the midamble field after the predetermined midamble periodicity M data symbols regardless of the MCS value assigned to the STA in the UL transmission. When the AP receives the HE TB PPDU from the assigned STA, the position and length of the midamble field can be expected based on the predetermined midamble periodicity M value.

[0215] Fig.17 A PPDU 1700 including a midamble is shown according to an embodiment. The PPDU 100 includes a preamble 1702, first, second and third data portions 1706-1, 1706-2 and 1706-3, first and second midambles 1708-1 and 1708-2, and a packet extension (PE) 1710. The first data portion 1706-1 begins with a first data symbol 1706S1, followed by a second data symbol 1706S2, and ends with a seventh data symbol 1706S7. The second data portion 1706-2 begins with an eighth data symbol 1706S8. In the illustrative example shown, the midamble periodicity M is equal to 7.

[0216] A first channel estimation 1722-1 is performed using the preamble 1702 to generate parameters for a first equalization 1724-1 to be performed on symbols of the first data portion 1706-1. A second channel estimation 1722-2 is performed using the first midamble 1708-1 to generate parameters for a second equalization 1724-2 to be performed on symbols of the second data portion 1706-2. A third channel estimation 1722-3 is performed using the second midamble 1708-2 to generate parameters for a third equalization 1724-3 to be performed on symbols of the third data portion 1706-3.

[0217] For IEEE standard 802.11 devices, a space-time block coding STBC process has been implemented to provide stable performance in edge areas of AP coverage. The STBC operation pairs two OFDM symbols and sends the paired symbols in consecutive time slots, and the receiver decodes the paired symbols together. For example, when sending PPDU 1700 using STBC, the first data symbol 1706S1 is paired with the second data symbol 1706S2, the third data symbol is paired with the fourth data symbol, and so on.

[0218] However, the paired seventh data symbol 1706S7 and eighth data symbol 1706S8 are separated by the first intermediate synchronization code 1708-1. As a result, the system needs to wait for new channel information to be obtained from the second channel estimation 1722-2 in order to decode two OFDM symbols together, and needs to have a buffer size twice as large in order to store two different channel information together (here, the result of the first channel estimation 1722-1 using the preamble 1702 and the result of the second channel estimation 1722-2 using the first intermediate synchronization code 1708-1).

[0219] In an embodiment, when STBC is enabled and the Doppler subfield is set to a first state to indicate that the transmitted PPDU includes one or more midamble fields, the transmitter inserts the midamble field after M OFDM data symbols per midamble periodicity of the PPDU. If the midamble field is located between two OFDM symbols paired for STBC operation, the midamble field is shifted to a position after the two paired OFDM symbols.

[0220] In another embodiment, when STBC is enabled and the Doppler subfield is set to a first state to indicate that the transmitted PPDU includes one or more midamble fields, the transmitter inserts the midamble field after M OFDM data symbols per midamble periodicity of the PPDU. If the midamble field is located between two OFDM symbols to be paired for STBC operation, the midamble field is shifted to a position before the two paired OFDM symbols.

[0221] In either embodiment, when a PPDU is received, once the receiver correctly decodes the STBC value in the PHY preamble of the PPDU, the location and length of the midamble field can be determined.

[0222] In another embodiment, the value of the midamble periodicity M is always an even number, and as a result, the midamble field always appears before or after two OFDM data symbols that are paired for STBC operation, and never appears between the paired symbols.

[0223] When the transmitter sends APEP_LENGTH bytes of data in a HE PPDU, where the Doppler subfield is set to a first state (e.g., 1) indicating the presence of one or more midambles, the number N of OFDM data symbols SYM Depending on the coding scheme, the number of data symbols N SYM It can be determined by the following formula:

[0224] For BCC:

[0225] For LDPC:

[0226] When using STBC, m STBC is 2, otherwise it is 1, N DBPS is the number of data bits per OFDM symbol, N Tail is the number of tail bits (6), N Service is the number of service bits (16).

[0227] Given N SYM , the transmitter sets the value of the length field in L-SIG to:

[0228]

[0229] in:

[0230] TXTIME=20+T PA +N SYM T SYM +N MA T MA+T PE +SE,

[0231] T MA =N HE-LTF T HE-LTF (+T HE-STF ),as well as

[0232]

[0233] And, where N MA is the number of midambles, M is the midamble periodicity, SE is 0us when transmitting in the 5GHz band and is 6us when transmitting in the 2.4GHz band, T PA Is it about Figures 7A to 7D The duration of the HE preamble, T SYM is the duration of an OFDM data symbol, T PE is the duration of the packet extension (the packet extension consists of a random value whose average power is the same as that of the OFDM data symbols and ensures additional receive processing time), and M is 1 for a HEMU PPDU or HEER SU PPDU, and 2 otherwise. MA is the duration of the midamble field, in the embodiment T MA The duration T of the HE-STF may be included HE-STF , and in another embodiment T MA The duration T of HE-STF may not be included HE-STF .

[0234] When a receiver receives an HE PPDU, it needs to determine how many OFDM data symbols (N SYM ) and how much time T can be guaranteed PE Used for RX processing.

[0235] In an embodiment, a device receiving a HE PPDU finds the number of OFDM data symbols (N SYM ) to determine the number of OFDM symbols used to decode the data symbols of the HE PPDU:

[0236]

[0237]

[0238] where b PE-Disambiguity is the value of the PE disambiguation bit in the HE-SIG-A field of the PPDU. Once N SYM , T PE Calculated by the following formula:

[0239]

[0240] Therefore, in a PPDU in which one or more midamble fields are present, the receiver can determine the number of OFDM data symbols N using Equation 5 SYM , but the number of intermediate synchronization codes N in Equation 5 MA YesN SYM As a result, the receiver cannot directly calculate the number of OFDM symbols N SYM , and the number N of OFDM data symbols is realized in the received PPDU including one or more midambles compared to the case where the midamble field is not included in the PPDU SYM The determination of may increase the system complexity. It is difficult to eliminate the circular dependencies of equations 4 and 5 because, for example, nonlinear elements of these equations, such as the floor operation (ie, ) is each equation.

[0241] The embodiment uses a method for determining the number N of OFDM symbols used for data symbols. SYM and the received HEPPDU packet extension duration T PE A novel process is provided to reduce the complexity of a device configured to receive a HE PPDU including a midamble.

[0242] To determine the number N of OFDM data symbols at the receiving device SYM , you can consider using equation 5. However, equation 5 requires the number of intermediate synchronization codes N MA The value of is known, and equation 4 confirms that the number of midambles N MA is the number of OFDM data symbols N SYM Therefore, when the Doppler subfield of the HE-SIG-A field of the PPDU being received is set to the first state (e.g., 1), this indicates that one or more midambles exist, and the number of OFDM data symbols N cannot be directly calculated using Equation 5. SYM Therefore, new equations and new assumptions are needed to determine N SYM . The new equation can be derived as follows:

[0243] Step A1) The function can be truncated from Equation 4 by restating Equation 4 using an additional unknown variable n0 as follows:

[0244] For some n0,0≤n0≤M-1,

[0245] Step A2) The lower truncation function can be eliminated from Equation 5 by restating Equation 5 using an additional unknown variable α as follows:

[0246] For some α,0≤α<1,

[0247]

[0248] Step A3) According to step A1 and step A2, the following equation can be derived:

[0249]

[0250]

[0251] Step A4) Based on the above, the minimum and maximum possible values ​​of n0 and α can be used to determine the number of midambles N. MA The minimum (N MA_MIN ) and maximum (N MA_MAX ) Possible values:

[0252] Assume α=0,n0=0:

[0253]

[0254] Assume α=1,n0=M-1:

[0255]

[0256] And note:

[0257] N MA_MIN <N MA <N MA_MAX Formula 13

[0258] Step A5) According to the above, determine the MA_MAX -N MA_MIN ) to determine the number N of midambles used MA The range of possible values ​​is:

[0259]

[0260] Because N MA_MAX and N MA_MIN The difference between is less than one and N MA_MAX Greater than N MA_MIN , so the lower truncation floor(N MA_MAX ) = upper truncation ceiling(N MA_MIN ). Depending on this and on the number N of intermediate synchronization codes MA Must be N MA_MAX and N MA_MIN A positive integer between

[0261] N MA =floor(N MA_MAX)=ceiling(N MA_MIN ) Formula 15

[0262]

[0263] Therefore, using the middle or right side of Equation 16, the number of midambles N can be determined: MA , without first determining the number N of OFDM symbols used to decode the data symbols SYM (ie, the number of OFDM data symbols N SYM ).

[0264] In an embodiment according to Equation 16, the number N of OFDM data symbols identified from the received HE PPDU is SYM and the package extension duration T PE When the Doppler subfield indicates that a midamble is present in the received HE PPDU, the number of midambles N is first determined according to the following formula: MA :

[0265]

[0266] When the Doppler subfield indicates that a midamble is not present in the HE PPDU, the number of midambles N MA is 0. Different from the process relying on Equation 4, the number of midambles N is determined using Equation 17 MA The process does not require first determining the value N in order to do so SYM .

[0267] Once the number of midambles N is determined MA , then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and the packet extension duration T can be determined according to Equation 6 PE .

[0268] In another embodiment according to Equation 16, the number N of OFDM data symbols is identified from the received HE PPDU SYM and the package extension duration T PE When the Doppler subfield indicates that the midamble is present in the HE PPDU, the number of midambles N is determined according to the following formula: MA :

[0269]

[0270] When the Doppler subfield indicates that a midamble is not present in the HE PPDU, the number of midambles N MA = 0, use equation 18 to determine the number of midambles N MAThe process does not require first determining N in order to do so SYM The value of .

[0271] Once the number of midambles N is determined MA , then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and the packet extension duration T can be determined according to Equation 6 PE .

[0272] The analysis that led to equations 17 and 18 can be generalized to cover the number of midambles N MA and the number of OFDM data symbols N SYM Other similar relationships between.

[0273] For example, when the number of OFDM data symbols N SYM When M is equal to twice the midamble periodicity, the relationship in equation 4 will indicate two 2 midambles. This will produce Fig.18 PPDU shown.

[0274] Fig.18 A PPDU 1800 is shown according to an embodiment. Fig.18 Elements with reference characters of the form 18XX or 18XX-X in Fig.17 Elements having corresponding reference characters in the form of 17XX or 17XX-X are shown in the drawings and their description is omitted for the sake of brevity.

[0275] PPDU 1800 includes 2·M OFDM data symbols, where M is the midamble periodicity. As a result, midamble 1808-1 is inserted after the first M OFDM data symbols, and because this embodiment is according to equation 4, another (optional) midamble 1826 is inserted after the last OFDM data symbol. Midamble 1826 is optional because packet extension (PE) 1810 is not an OFDM symbol to be decoded, and therefore the third channel estimation 1822-3 and the third equalization 1824-3 are not required.

[0276] In an embodiment, in order to prevent the insertion of this unnecessary midamble, the transmitter appropriately determines the number N of OFDM data symbols used in the HE PPDU according to Equation 1 or Equation 2. SYM , and determine the length field of the L-SIG of the HE PPDU according to Equation 3.

[0277] Then, instead of determining the number N of the intermediate synchronization codes according to the above equation 4 MA , instead, the transmitter can determine the number of intermediate synchronization codes N according to the following formula MA :

[0278]

[0279] When a receiver receives a HE PPDU, it needs to derive how many (N) are being sent in the received HE PPDU. SYM ) is the OFDM data symbol to be decoded to produce data, and how much additional time is provided for the receive processing, i.e., the packet extension duration T PE . The equation for doing this can be derived as follows:

[0280] Step B1) The lower truncation function can be eliminated from Equation 19 by restating Equation 19 using an additional unknown variable n0 as follows:

[0281] For some n0,0≤n0≤M-1,

[0282] Step B2) The lower truncation function can be eliminated from Equation 5 by restating Equation 5 using an additional unknown variable α as follows:

[0283] For some α,0≤α<1,

[0284]

[0285] Step B3) According to step B1 and step B2, the following equation can be derived:

[0286]

[0287]

[0288] Step B4) Based on the above, the minimum and maximum possible values ​​of n0 and α can be used to determine the number N of midambles used. MA The minimum ((N MA_MIN ) and maximum (N MA_MAX ) Possible values:

[0289] Assume α=0,n0=0:

[0290]

[0291] Assume α=1,n0=M-1:

[0292]

[0293] And note:

[0294] N MA_MIN <N MA <N MA_MAX Formula 26

[0295] Step B5) According to the above, determine the MA_MAX -N MA_MIN ) to determine the number of intermediate synchronization codes N MA The range of possible values ​​is:

[0296]

[0297] Because N MA_MAX and N MA_MIN The difference between is less than one and N MA_MAX Greater than N MA_MIN , so the lower truncation floor(N MA_MAX ) = upper truncation ceiling(N MA_MIN ). Depending on this and on the number N of intermediate synchronization codes MA Must be N MA_MAX and N MA_MIN A positive integer between

[0298] N MA =floor(N MA_MAX )=ceiling(N MA_MIN ) Formula 28

[0299]

[0300] Therefore, the number of midambles N MA The number of OFDM data symbols N can be determined without first using the middle or right side portion of Equation 29 SYM is determined in the case.

[0301] In an embodiment according to Equation 29, the number N of OFDM data symbols identified from the received HE PPDU is SYM and the package extension duration T PE When the Doppler subfield indicates that a midamble is present in the HE PPDU, the number of midambles N is first determined according to the following formula: MA :

[0302]

[0303] When the Doppler subfield indicates that a midamble is not present in the HE PPDU, the number of midambles N MA is 0. Different from the process relying on Equation 4, the number of midambles N is determined using Equation 30 MA The process does not require first determining the value N in order to do so SYM .

[0304] Once the number of midambles N is determined MA, then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and determine the packet extension duration T according to Equation 6 PE .

[0305] In another embodiment according to Equation 29, the number N of OFDM data symbols is identified from the received HE PPDU SYM and the package extension duration T PE When the Doppler subfield indicates that the midamble is present in the HE PPDU, the number of midambles N is determined according to the following formula: MA :

[0306]

[0307] When the Doppler subfield indicates that no midamble is present in the HE PPDU, the number of midambles N MA = 0, use equation 31 to determine the number of midambles N MA The process does not require first determining N in order to do so SYM The value of .

[0308] Once the number of midambles N is determined MA , then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and determine the packet extension duration T according to Equation 6 PE .

[0309] By Fig.18 induction, Fig. 20 A PPDU 2000 according to an embodiment is shown. Fig. 20 Elements with reference characters of the form 20XX or 20XX-X in the Fig.17 Elements having corresponding reference characters in the form of 17XX or 17XX-X are designated and their description is omitted for brevity.

[0310] The illustrated PPDU 2000 includes 2M+β OFDM data symbols, where M is the midamble periodicity. In the example shown, β=1. As a result, the midamble 2008-1 is inserted after the first M OFDM data symbols, and because the embodiment is according to Equation 4 (or Equation 19), another (non-essential) midamble 2026 is inserted before the last OFDM data symbol 2006-2M+1 and PE 2010. The midamble 2026 is non-essential because the equalization required to decode the last OFDM data symbol 2006-2M+1 may be substantially the same as the equalization required to receive the penultimate OFDM data symbol 2006-2M, and the packet extension (PE) 2010 is not an OFDM symbol to be decoded. Therefore, the third channel estimation 2022-3 and the third equalization 2024-3 are not required, which means that the non-essential midamble 2026 is not required.

[0311] In an embodiment, in order to prevent the insertion of unnecessary midamble 2026, the transmitter appropriately determines the number N of OFDM symbols used to encode data symbols in the HE PPDU according to Equation 1 or Equation 2. SYM , and determine the length field of the L-SIG of the HE PPDU according to Equation 3.

[0312] Then, instead of determining the number N of the intermediate synchronization codes according to the above equation 4 or 19 MA , instead, the transmitter can determine the number of intermediate synchronization codes N according to the following formula MA :

[0313]

[0314] This prevents another midamble from being inserted after the last midamble when only M+β OFDM data symbols remain to be sent, 0≤β<M. In an embodiment, β=1. Equivalently, because for any positive integers y and z, Equation 19A is equivalent to:

[0315]

[0316] When the receiver receives an HE PPDU, it needs to derive how many (N SYM ) OFDM data symbol and how much extra time has been provided, i.e., the PE duration T PE , for receiving processing. The equation for doing this can be derived as follows:

[0317] Step C1) The upper truncation function can be removed from Equation 19B by restating Equation 19B using an additional unknown variable n0 as follows:

[0318] For some n0,0≤n0≤M-1,

[0319]

[0320] Step C2) The lower truncation function can be eliminated from Equation 5 by restating Equation 5 using an additional unknown variable α as follows:

[0321] For some α,0≤α<1,

[0322]

[0323] Step C3) According to step C1 and step C2, the following equation can be derived:

[0324]

[0325]

[0326] Step C4) Based on the above, the minimum and maximum possible values ​​of n0 and α can be used to determine the number N of midambles used. MA The minimum (N MA_MIN ) and maximum (N MA_MAX ) Possible values:

[0327] Assume α=1,n0=M-1:

[0328]

[0329] Assume α=0,n0=0:

[0330]

[0331] And note:

[0332] N MA_MIN <N MA <N MA_MAX Formula 26B

[0333] Step C5) According to the above, determine the MA_MAX -N MA_MIN ) to determine the number of intermediate synchronization codes N MA The range of possible values ​​is:

[0334]

[0335] Because N MA_MAX and N MA_MIN The difference between is less than one and NMA_MAX Greater than N MA_MIN , so the lower truncation floor(N MA_MAX ) = upper truncation ceiling(N MA_MIN ). Depending on this and on the number N of intermediate synchronization codes MA Must be N MA_MAX and N MA_MIN A positive integer between

[0336] N MA =floor(N MA_MAX )=ceiling(N MA_MIN ) Formula 28B

[0337]

[0338] Therefore, the number of intermediate synchronization codes N can be determined MA , without first determining the number of OFDM data symbols N SYM .

[0339] In an embodiment according to Equation 29B, the number N of OFDM data symbols identified from the HE PPDU being received SYM and the package extension duration T PE When the Doppler subfield indicates that a midamble is present in the HE PPDU, the number of midambles N is first determined according to the following formula: MA :

[0340]

[0341] When the Doppler subfield indicates that a midamble is not present in the HE PPDU, the number of midambles N MA is 0. Different from the process relying on Equation 4, the number of midambles N is determined using Equation 30B MA The process does not require first determining N in order to do so SYM The value of .

[0342] Once the number of midambles N is determined MA , then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and the packet extension duration T can be determined according to Equation 6 PE .

[0343] In another embodiment according to Equation 29B, the number N of OFDM data symbols is identified from the received HE PPDU SYM and the package extension duration T PEWhen the Doppler subfield indicates that the midamble is present in the HE PPDU, the number of midambles N is determined according to the following formula: MA :

[0344]

[0345] When the Doppler subfield indicates that the midamble is not present in the HE PPDU, the number of midambles is 0 and the number of midambles N is determined using Equation 31B. MA The process does not require first determining N in order to do so SYM The value of .

[0346] Once the number of midambles N is determined MA , then the process can determine the number of OFDM data symbols N according to Equation 5 SYM , and the packet extension duration T can be determined according to Equation 6 PE .

[0347] For example, given β=0, the number N of each midamble according to Equation 1, Equation 3, and Equation 4 is MA The exact same value is provided on the TX side. Equations 19 and 19B generate the number N of midambles used on the receive side. MA The same value of .

[0348] For another example, given β=1, then on the TX side, replacing β in Equation 19B with 1 yields:

[0349]

[0350] And at the receiving side, when β=1, the number of intermediate synchronization codes N MA Determined by either of the following equations:

[0351]

[0352] or

[0353]

[0354] Note that when β = 1, by definition, the number of midambles N MA is 0 or a positive integer, where the number of intermediate synchronization codes N MA is the number of intermediate synchronization codes inserted per M except for two cases. If mod(N SYM ,N MA )=0, no midamble is inserted after the last OFDM data symbol, and at the end of the HE PPDU, if mod(N SYM ,N MA)=1, then no midamble is inserted before the last OFDM data symbol. In an embodiment, β is a predetermined value.

[0355] In another embodiment, a process determines the number N of OFDM data symbols for a received HE PPDU as follows: SYM and the package extension duration T PE :

[0356] When the Doppler information for the HE PPDU indicates that one or more midambles are present in the HE PPDU, the process determines the number N of midambles according to the following equation: MA :

[0357]

[0358] Or determined according to the following formula:

[0359]

[0360] Otherwise, when the Doppler information indicates that there is no midamble in the HE PPDU, the number of midambles N MA =0.

[0361] The process then determines the estimated number of OFDM symbols T_N used to decode the data according to either SYM :

[0362]

[0363] or

[0364]

[0365] Need to determine T_T PE Is it less than 0 to verify the estimated number of OFDM symbols T_N SYM , to obtain N SYM The final value of .

[0366]

[0367]

[0368] Then the PE duration T is determined according to the above equation 6 PE .

[0369] according to Fig.19 , which is used to determine the above T_N is derived as follows SYM and N SYM of the above equations 34-37.

[0370] Fig.19Features of a PPDU 1900 including a midamble 1908 according to an embodiment are shown. The PPDU 1900 also includes an L-SIG field 1902, a HE preamble 1904, a first portion 1906-1 and a second portion 1906-2 of a data field, and a packet extension (PE) 1910. The duration of the HE preamble 1904 is determined by T PA The combined duration of the midamble of the PPDU is represented by T HE_MIDAMBLE The duration of PE 1910 is represented by T PE express.

[0371] The length from the end of the L-SIG field 1902 to the end of the PPDU beyond is equal to the value L_LENGTH of the length field of the L-SIG field 1902 plus the number of service bits (16) at the beginning of the first part of the data field 1906-1 plus the number of tail bits (6) at the end of the last (here, second) part of the data field 1906-2 plus m, where m is 1 for a HEMU PPDU or HEER SU PPDU and 2 otherwise.

[0372] In order to obtain N SYM , when the Doppler information is set to a first state (e.g., 1) indicating the presence of a midamble, the following equation is used:

[0373]

[0374] Step D1) is derived from equation 38:

[0375]

[0376]

[0377]

[0378] Because in the receiver of HE PPDU, in the absence of N SYM In the case of T PE I don't know, so ((T PE +α) / T SYM ) is temporarily ignored, and the impact of this term will be verified later. As shown in the following equation 42, N SYM Replaced by T_N SYM , as the temporary number of OFDM data symbols:

[0379]

[0380] Step D2) According to the above:

[0381] T_N SYM=M·N MA +n0,0≤n0≤M-1 Formula 43

[0382] Step D3) according to step D1 and step D2:

[0383]

[0384]

[0385]

[0386] Step D4) according to step D2 and step D3,

[0387]

[0388]

[0389] Step D5) Calculate the number N of intermediate synchronization codes MA The minimum and maximum values ​​of to find the boundaries:

[0390] Assume α=1,n0=0,

[0391]

[0392] Assume α=0,n0=M-1,

[0393]

[0394]

[0395] Step D6) Check (Max N MA -Min N MA ) to view N MA Range:

[0396]

[0397] Since the number of intermediate synchronization codes N MA Should be 0<(MaxN MA -MinN MA )<1, so N NA Should be a positive integer, so truncate floor(MaxN M ) = upper truncation ceil(MinN M ):

[0398]

[0399] Then, according to the above equation,

[0400]

[0401]

[0402] or

[0403]

[0404] In another embodiment, the number N of OFDM data symbols used to determine the received HE PPDU is determined as follows SYM and the package extension duration T PE The process:

[0405] When the Doppler information for the HE PPDU indicates that one or more midambles are present in the HE PPDU, the process determines the number N of midambles according to the following equation: MA :

[0406]

[0407] Or determined according to the following formula:

[0408]

[0409] Otherwise, when the Doppler information indicates that there is no midamble in the HE PPDU, the number of midambles N MA =0.

[0410] The process then determines the estimated number of OFDM symbols T_N used to decode the data according to either SYM :

[0411]

[0412] or

[0413]

[0414] Need to determine T_N SYM Is it less than 0 to verify the estimated number of OFDM symbols T_N SYM , to obtain N SYM The final value of .

[0415]

[0416]

[0417] Then determine the PE duration T according to Equation 6 above PE .

[0418] To determine the above T_N SYM and N SYMThe above equations 57-60 are derived as follows: In order to obtain N on the receiving side SYM , when the Doppler information is set to a first state (e.g., 1) indicating the presence of a midamble, the following equation is used:

[0419]

[0420] Step E1) is derived from equation 61:

[0421]

[0422]

[0423]

[0424] Because in the receiver of HE PPDU, in the absence of N SYM In the case of T PE I don't know, so (( PE +α) / T SYM ) is temporarily ignored, and the impact of this term will be verified later. As shown in the following equation 42, N SYM Replaced by T_N SYM , as the temporary number of OFDM data symbols:

[0425]

[0426] Step E2) According to the above:

[0427] T_N SYM =M·N MA +n0+1,0≤n0≤M-1 Formula 66

[0428] Step E3) According to step E1 and step E2:

[0429]

[0430]

[0431]

[0432] Step E4) According to step E2 and step E3,

[0433]

[0434]

[0435] Step E5) Find N MA The minimum and maximum values ​​of to find the boundaries:

[0436] Assume α=1,n0=0,

[0437]

[0438] Assume α=0,n0=M-1,

[0439]

[0440]

[0441] Step E6) Step D6) Check (MaxN MA -MinN MA ) to view N MA Range:

[0442]

[0443] Due to N NA Should be 0 < (MaxN MA -MinN MA )<1, so N MA Should be a positive integer, so truncate floor(MaxN MA ) = upper truncation ceil(MinN MA ):

[0444]

[0445] Then, according to the above equation,

[0446]

[0447]

[0448] or

[0449]

[0450] In another embodiment of the present invention, when a HE PPDU is received where the Doppler information is set to indicate the presence of one or more midambles, if a signal loss occurs during reception before the reception of the PSDU is completed, an error condition PHYRXEND.indication(CarrierLost) shall be reported to the MAC. After waiting for the end of the PPDU as determined by equation 80 below, the PHY shall set the PHY-CCA.indication(IDLE) primitive and return to the RX IDLE state.

[0451]

[0452] Note that the duration of HE-STF is THE-STF can be omitted from Equation 20.

[0453] Fig.21 A process 2100 for receiving a PPDU having a data field including a midamble is shown according to an embodiment. The symbols may be symbols in the data field of the PPDU with the midamble inserted therein. The process 2100 may be performed by a wireless device including a receiver, and the wireless device may include a processor configured to perform the process 2100.

[0454] At S2102, the process 2100 determines the format of the PPDU being received. Determining the format of the PPDU being received may include: receiving the first four symbols of the PPDU being received starting with the L-STF; determining the modulation method of the third symbol and the fourth symbol of the received symbols; and determining whether the content of the fourth symbol is the same as the content of the third symbol. The third symbol may be a symbol of a legacy signal (L-Sig) field.

[0455] When the third and fourth symbols are modulated using BPSK, the third symbol is an L-SIG field symbol and the fourth symbol carries a copy of the contents of the L-SIG field, the PPDU being received is an HE PPDU, and determining the format may also include receiving fifth and sixth symbols, and determining the format of the PPDU being received based on the value of the length field of the L-SIG field modulo 3 and the modulation method of the fifth and sixth symbols, as described with respect to Fig.12 as described.

[0456] At S2104, the process 2100 determines whether the PPDU being received is a HE PPDU. In response to determining that the PPDU being received is a HE PPDU, at S2104, the process 2100 proceeds to S2106; otherwise, the process 2100 exits.

[0457] At S2106, the process 2100 determines whether the PPDU being received is a HE multi-user (MU) PPDU or a HE extended range single user (ER SU) PPDU. In response to determining that the PPDU being received is a HE MU PPDU or a HE ER SU PPDU, at S2106, the process 2100 proceeds to S2110; otherwise, the process 2100 proceeds to S2108.

[0458] At S2108, in response to the PPDU being received being neither a HE MU PPDU nor a HE ER SU PPDU, the process S2100 sets the modifier m to 1 and then proceeds to S2112.

[0459] At S2110, in response to the received PPDU being a HE MU PPDU or a HE ER SU PPDU, the process S2100 sets the modifier m to 2 and then proceeds to S2112.

[0460] At S2112, the process S2100 decodes the HE Signal A (HE-SIG-A) field. When the PPDU being received is a HE ERSU PPDU, decoding the HE-SIG-A field includes receiving and decoding the fifth to eighth symbols of the PPDU being received. When the PPDU being received is a HE MU PPDU, a HE TB PPDU, or a HE SU PPDU, decoding the HE-SIG-A field includes receiving and decoding the fifth to sixth symbols of the PPDU being received.

[0461] At S2114, the process S2100 determines whether the HE-SIG-A field indicates that the PPDU being received includes a midamble. In an embodiment, the process S2100 determines that the PPDU being received includes a midamble in response to the Doppler field of the HE-SIG-A field having a value corresponding to a first state (e.g., 1), and when the Doppler field does not have a value corresponding to the first state (i.e., has a value different from the value corresponding to the first state), it is determined that the PPDU being received does not include a midamble.

[0462] In response to determining that the PPDU being received includes a midamble, at S2114 , the process 2100 proceeds to S2116 ; otherwise, the process 2100 exits.

[0463] At S2116, the process 2100 determines the L-SIG length field L_LENGTH, the packet extension (PE) disambiguation bit b PE-Disambiguity HE-LTF duration T HE-LTF , Preamble duration T PA , the duration of the middle synchronization code T MA , the duration T of the symbol of the data field of the PPDU being received SYM (In the following, the data symbol duration T SYM ) and the value of the intermediate synchronization code periodicity M.

[0464] Process 2100 determines the value of the L-SIG length field L_LENGTH using the L-SIG field of the PPDU being received. Process 2100 determines the value of the PE disambiguation bit b using information in the HE-SIG-A field according to the applicable standard. PE-Disambiguity , the midamble periodicity M, and the data symbol duration T SYM In an embodiment, the applicable standard is IEEE standard 802.11ax or its successor standard.

[0465] Process 2100 determines, using information in the HE-SIG-A field, a HE-LTF duration T corresponding to the duration of the HE-LTF included in the PPDU being received, in accordance with the applicable standard. HE-LTF As used herein, the HE-LTF duration T HE-LTF Includes the duration of the guard interval included in each HE-LTF.

[0466] Process 2100 sets the preamble duration T PA The value of is determined to be equal to the duration of the RL-SIG field (4 μs), the duration of the HE-SIG-A field (16 μs for HE ER SU PPDU, otherwise 8 μs), the duration of the HE-SIG-B field (if present) (variable), the duration of the HE-STF (8 μs for HE TB PPDU, otherwise 4 μs), and the combined duration of one or more HE-LTFs immediately following the HE-STF (hereinafter, the number of which is referred to as the number of HE-LTFs N) HE-LTF Process 2100 determines the number N of HE-LTFs using the information in the HE-SIG-A field according to the applicable standard. HE-LTF .

[0467] Process 2100 is based on the number N of HE-LTFs HE-LTF With HE-LTF duration T HE-LTF The product of the intermediate synchronization code duration T is determined MA The value of, as specified in the applicable standard:

[0468] T MA =N HE-LTF ·T HE-LTF Formula 81

[0469] At S2118, the process 2100 determines the number N of midambles using the value determined at S2116. MA In an embodiment, the number of midambles N is determined according to equation 30B above using the value of β specified by the applicable standard. MA Where β is an integer value greater than or equal to zero and indicates the number of data symbols exceeding the midamble periodicity M allowed at the end of the data field without the need to insert another midamble. In an embodiment, the number of midambles N is determined according to Equation 31B above using the value of β specified by the applicable standard. MA In an embodiment, the value of β is 0. In other embodiments, the value of β is 1.

[0470] At S2120, process 2100 determines the number N of data symbols SYM The value and duration of PE T PE In an embodiment, process 2100 determines the number of data symbols N according to equation 5 above: SYM Then, the PE duration T is determined according to Equation 6 above. PE The value of .

[0471] At 2122, the process 2100 receives the data field of the PPDU being received using the information determined in S2102 to S2120. Receiving the data field may include iteratively receiving a number of data symbols equal to the midamble periodicity M and midambles immediately following the data symbols until the number of received midambles is equal to the number N of midambles determined at S2118. MA Each intermediate synchronization code consists of N HE-LTF It consists of HE-LTFs.

[0472] Once the iteration is complete, the remaining data symbols are received. The process 2100 then exits. The number of remaining data symbols N remain yes

[0473] N remain =N SYM -(M·N MA ) Formula 82

[0474] Fig. 22 A process 2222 for receiving a data field of a PPDU including a midamble is shown according to an embodiment. The process 2222 may be performed at Fig.21 Executed in S2122 of process 2100.

[0475] At S2202, the process 2222 initializes a loop counter N to 1. At S2204, the process 2222 receives an Nth plurality of consecutive data symbols, wherein the number of data symbols in each plurality of consecutive data symbols is equal to the midamble periodicity M.

[0476] At S2206, the process 2222 receives the Nth midamble. At S2208, the process 2222 increments the loop counter N by 1.

[0477] At S2210, in response to the value of the loop counter N being less than or equal to the number N of the intermediate synchronization codes, MA value, process 2222 proceeds to S2204; otherwise, at S2210, process 2222 proceeds to S2212.

[0478] At S2212, process 2222 receives the remaining data symbols. The number of remaining data symbols may be determined according to equation 82 above.

[0479] The solutions provided herein have been described with reference to a wireless LAN system; however, it should be understood that these solutions may also be applicable to other network environments, such as a cellular telecommunication network, a wired network, and the like.

[0480] The above description and drawings apply to HE stations, HE frames, HE PPDUs, HE-SIG fields, etc. of IEEE 802.11 ax modification, but they may also be applicable to receivers, frames, PPDUs, SIG fields, etc. of another future modification of IEEE 802.11.

[0481] Embodiments of the present disclosure include electronic devices configured to perform one or more operations described herein. However, the embodiments are not limited thereto.

[0482] Embodiments of the present disclosure may also include systems configured to operate using the processes described herein. A system may include a basic service set (BSS), such as Figure 1 The BSS 100 may be configured as follows, but the embodiment is not limited thereto.

[0483] The embodiments of the present disclosure may be implemented in the form of program instructions, which may be executed by various computer devices such as processors or microcontrollers and recorded in non-transitory computer-readable media. Non-transitory computer-readable media may include one or more of program instructions, data files, data structures, etc. The program instructions may be suitable for executing a process, and when, for example, Figure 1 The method generates and decodes the frames described herein when executed on a device such as the wireless device shown in FIG.

[0484] In an embodiment, the non-transitory computer readable medium may include a read-only memory (ROM), a random access memory (RAM), or a flash memory. In an embodiment, the non-transitory computer readable medium may include a disk, an optical disk, or a magneto-optical disk, such as a hard drive, a floppy disk, a CD-ROM, etc.

[0485] In some cases, embodiments of the present invention may be an apparatus (e.g., an AP station, a non-AP station, or another network or computing device) that includes one or more hardware and software logic structures for performing one or more operations described herein. For example, as described above, the apparatus may include a storage unit that stores instructions that can be executed by a hardware processor installed in the apparatus. The apparatus may also include one or more other hardware or software elements, including a network interface, a display device, etc.

[0486] Although the present invention has been described in conjunction with what are currently considered to be practical embodiments, the embodiments are not limited to the disclosed embodiments, but rather may include various modifications and equivalent arrangements within the spirit and scope of the appended claims. The order of operations described in the procedures is illustrative, and some operations may be reordered. Furthermore, two or more embodiments may be combined.

Claims

1. A method performed by a wireless device, the method comprising: When a format of a physical layer protocol data unit (PPDU) is determined to be a high efficiency (HE) single user (SU) format or a HE SU extended range format, setting a value of a midamble periodicity according to a modulation and coding scheme (MCS) of the PPDU; When the format of the PPDU is determined to be a HE trigger-based format, setting the value of the midamble periodicity to a predetermined value; as well as The data field of the PPDU is periodically transmitted or received according to the intermediate synchronization code.

2. The method of claim 1, further comprising: When the format of the PPDU is determined to be a HE downlink multi-user (MU) format, the midamble periodicity is set according to the highest MCS among all stations corresponding to the PPDU.

3. The method of claim 2, further comprising: When the format of the PPDU is determined to be a single-user HE uplink MU format, the midamble periodicity is set according to the MCS of the PPDU.

4. The method of claim 2, further comprising: When the format of the PPDU is determined to be the HE uplink MU format, the midamble periodicity is set according to the highest MCS among all stations corresponding to the PPDU.

5. The method of claim 1, further comprising: When the format of the PPDU is determined to be a HE downlink multi-user (MU) format or a HE uplink MU format, the value of the midamble periodicity is set to a predetermined value.

6. A method performed by a wireless device, the method comprising: When a format of a physical layer protocol data unit (PPDU) is determined to be a first format, setting a midamble periodicity according to a modulation and coding scheme (MCS) of the PPDU; When the format of the PPDU is determined to be the second format, setting the midamble periodicity according to the highest MCS among all stations transmitting or receiving the PPDU on the PPDU; When the format of the PPDU is determined to be a third format, setting the midamble periodicity to a predetermined value; When the format of the PPDU is determined to be the fourth format, setting the midamble periodicity to a value specified in a request frame for requesting to send the PPDU; as well as The data field of the PPDU is periodically transmitted or received according to the intermediate synchronization code.

7. A wireless device comprising: Transmitter; Receiver; as well as A processor configured to execute: When a format of a physical layer protocol data unit (PPDU) is determined to be a high efficiency (HE) single user (SU) format or a HE SU extended range format, setting a value of a midamble periodicity according to a modulation and coding scheme (MCS) of the PPDU; When the format of the PPDU is determined to be a HE trigger-based format, setting the value of the midamble periodicity to a predetermined value; as well as According to the midamble periodicity, a data field of the PPDU is transmitted using the transmitter or a data field of the PPDU is received using the receiver.

8. The wireless device of claim 7, wherein the processor is further configured to: When the format of the PPDU is determined to be a HE downlink multi-user format, the midamble periodicity is set according to the highest MCS among all stations corresponding to the PPDU.

9. The wireless device of claim 7, wherein the processor is further configured to: When the format of the PPDU is determined to be a HE downlink multi-user (MU) format or a HE uplink MU format, the value of the midamble periodicity is set to a predetermined value.

10. A wireless device comprising: Transmitter; Receiver; as well as A processor configured to execute: When a format of a physical layer protocol data unit (PPDU) is determined to be a first format, setting a midamble periodicity according to a modulation and coding scheme (MCS) of the PPDU; When the format of the PPDU is determined to be the second format, setting the midamble periodicity according to the highest MCS among all stations transmitting or receiving the PPDU on the PPDU; When the format of the PPDU is determined to be a third format, setting the midamble periodicity to a predetermined value; When the format of the PPDU is determined to be the fourth format, setting the midamble periodicity to a value specified in a request frame for requesting to send the PPDU; as well as According to the midamble periodicity, a data field of the PPDU is transmitted using the transmitter or a data field of the PPDU is received using the receiver.

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