Single carrier frequency division multiplexing (SC-FDM) for wireless local area network (WLAN)

Abstract

The present disclosure provides methods, devices and systems for reducing PAPR in wireless communications. More specifically, some implementations relate to single carrier frequency division multiplexing (SC-FDM) techniques that may be used for wireless communications in a wireless local area network (WLAN). In some aspects, a wireless communication device may modulate a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) into a series of symbols in the time domain, and may transform a subset of the time domain symbols into a number (Q) of frequency domain samples based on a Q-point Discrete Fourier Transform (DFT). The wireless communication device maps the Q frequency domain samples to a number (N) of orthogonal subcarriers (representing Orthogonal Frequency Division Multiplexing (OFDM) symbols), wherein Ngt; in one embodiment, the N subcarriers are divided into N subcarriers, Q, and the N subcarriers are transformed into N time domain samples based on inverse fast Fourier transform (IFFT) for transmission over a wireless channel.

Description

[0001] Cross-references

[0002] This patent application claims priority to U.S. patent application No. 17 / 843,747, filed by Yang et al. on June 17, 2022, and entitled “Single-Carrier Frequency-Division Multiplexing (SC-FDM) for Wireless Local Area Networks (WLANs)”, which is assigned to the assignee of this application and is expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to wireless communications and, more particularly, to single carrier frequency division multiplexing (SC-FDM) for wireless local area networks (WLANs). Background Art

[0004] A wireless local area network (WLAN) can be formed by one or more wireless access points (APs) that provide a shared wireless communication medium for use by multiple client devices, also referred to as stations (STAs). The basic building block of a WLAN that complies with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 series of standards is the basic service set (BSS), which is managed by the AP. Each BSS is identified by a basic service set identifier (BSSID) advertised by the AP. The AP periodically broadcasts beacon frames to enable any STA within the wireless range of the AP to establish or maintain a communication link with the WLAN.

[0005] Many existing WLAN communication protocols utilize orthogonal frequency division multiplexing (OFDM) technology, which tends to produce signals with relatively high peak-to-average power ratios (PAPR). Wireless signals with high PAPR require large power backoffs for transmission. Therefore, high PAPR may affect the effective range or efficiency of OFDM transmissions. Wireless communications at higher carrier frequencies suffer from even greater path losses than wireless communications at lower carrier frequencies. Therefore, new communication protocols and operating modes may be needed to reduce the PAPR associated with wireless communications, for example, to communicate over an extended range or to overcome path losses associated with higher carrier frequencies. Summary of the invention

[0006] The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0007] An innovative aspect of the subject matter described in the present disclosure may be implemented as a method of wireless communication. The method may be performed by a wireless communication device and may include: modulating a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU) into a plurality of symbols, the PPDU including a PHY preamble followed by a data portion, wherein the PHY preamble includes a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU; transforming a number (Q) of symbols including one or more first symbols of the plurality of symbols representing the PPDU into Q frequency domain samples based on a discrete Fourier transform (DFT); mapping the Q frequency domain samples to a number (N) of subcarriers, wherein N>Q; transforming the N subcarriers into N time domain samples based on an inverse fast Fourier transform (IFFT); and transmitting the N time domain samples over a wireless channel. In some aspects, Q may be divisible only by 2, 3, or 5.

[0008] In some aspects, the method may further include: mapping one or more null values ​​to one or more of the N subcarriers, respectively, wherein each of the one or more subcarriers represents a direct current (DC) subcarrier associated with the bandwidth of the wireless channel. In some aspects, the N subcarriers may be subdivided into a number (n) of segments, each segment being associated with a corresponding index (i), wherein 1≤i≤n. In such aspects, the method may further include: applying a series of first phase rotations to the subcarriers in each of the n segments associated with an even index i; and applying a series of second phase rotations to the subcarriers in each of the n segments associated with an odd index i, wherein the series of second phase rotations is different from the series of first phase rotations.

[0009] In some aspects, the Q symbols may also include one or more pilot symbols associated with a phase tracking operation. In some implementations, the one or more pilot symbols may be interspersed between the one or more first symbols. In some other implementations, the one or more pilot symbols may be placed continuously in the time domain following the one or more first symbols. In some implementations, the method may also include: appending a cyclic prefix including the one or more pilot symbols to the front of the N time domain samples.

[0010] In some other aspects, the Q symbols may further include one or more null symbols placed consecutively in the time domain following the one or more first symbols, wherein each of the one or more null symbols has a value equal to zero that maps to a corresponding null sample in the N time domain samples. In such aspects, the method may further include: transmitting a sequence of guard interval (GI) values ​​immediately preceding the N time domain samples; and modulating the sequence of GI values ​​on one or more null samples in the N time domain samples.

[0011] In some aspects, the method may further include: mapping one or more second symbols of the plurality of symbols directly to the N subcarriers, wherein the one or more second symbols represent at least a portion of the PHY preamble. In some implementations, the portion of the PHY preamble may include the LTF. In some implementations, the LTF may be modulated according to a modulation scheme having a higher modulation order than binary phase shift keying (BPSK). In some other implementations, the LTF may include a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u), and a sequence length (N), wherein:

[0012]

[0013] In some implementations, N may be a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped. In some other implementations, N may be a prime number associated with a bandwidth of the wireless channel.

[0014] Another innovative aspect of the subject matter described in the present disclosure can be implemented in a wireless communication device. In some implementations, the wireless communication device may include at least one memory and at least one processor, the at least one processor being communicatively coupled to the at least one memory and configured to cause the wireless communication device to perform operations, the operations including: modulating a PPDU into a plurality of symbols, the PPDU including a PHY preamble, the PHY preamble followed by a data portion, wherein the PHY preamble includes an STF, an LTF, and one or more SIG fields carrying information for interpreting the PPDU; transforming a number (Q) of symbols including one or more first symbols of the plurality of symbols representing the PPDU into Q frequency domain samples based on a DFT; mapping the Q frequency domain samples to a number (N) of subcarriers, wherein N>Q; transforming the N subcarriers into N time domain samples based on an IFFT; and transmitting the N time domain samples over a wireless channel.

[0015] Another innovative aspect of the subject matter described in the present disclosure may be implemented as a method of wireless communication. The method may be performed by a wireless communication device and may include: receiving a time-varying signal carrying a PPDU on a wireless channel, the PPDU including a PHY preamble followed by a data portion, wherein the PHY preamble includes an STF, an LTF, and one or more SIG fields carrying information for interpreting the PPDU; transforming a number (N) of first time domain samples of the time-varying signal into N first modulated subcarriers based on FFT; demapping the N first modulated subcarriers into a number (Q) of frequency domain samples, wherein N>Q; transforming the Q frequency domain samples into Q symbols based on IDFT; demodulating the Q symbols; and recovering at least a portion of the PPDU from the Q demodulated symbols. In some aspects, Q may be divisible only by 2, 3, or 5.

[0016] In some aspects, the Q symbols may include one or more pilot symbols associated with a phase tracking operation. In some implementations, the one or more pilot symbols may be interspersed between one or more data symbols in the Q symbols representing the portion of the PPDU. In some other implementations, the one or more pilot symbols may be placed consecutively in the time domain following one or more data symbols in the Q symbols representing the portion of the PPDU. In some implementations, the received time-varying signal may include a cyclic prefix preceding the N time domain samples, wherein the cyclic prefix includes the one or more pilot symbols.

[0017] In some other aspects, the received time-varying signal includes a sequence of GI values ​​immediately preceding the N time domain samples. In such aspects, the method may also include recovering the sequence of GI values ​​from one or more first symbols of the Q symbols, the one or more first symbols of the Q symbols being placed consecutively in the time domain following one or more data symbols of the Q symbols representing the portion of the PPDU.

[0018] In some aspects, the method may further include: transforming N second time domain samples of the received time-varying signal into N second modulated subcarriers based on the FFT; demodulating the N second modulated subcarriers; and recovering at least a portion of the PHY preamble from the N demodulated subcarriers. In some aspects, the portion of the PHY preamble recovered from the N demodulated subcarriers may include the LTF. In some implementations, the N second modulated subcarriers may be demodulated according to a modulation scheme having a higher modulation order than BPSK. In some other implementations, the LTF may include a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u), and a sequence length (N), wherein:

[0019]

[0020] In some implementations, N may be a prime number associated with the RU or M-RU to which the Q frequency-domain samples are mapped. In some other implementations, N may be a prime number associated with the bandwidth of the wireless channel.

[0021] Another innovative aspect of the subject matter described in the present disclosure can be implemented in a wireless communication device. In some implementations, the wireless communication device may include at least one memory and at least one processor, the at least one processor being communicatively coupled to the at least one memory and configured to cause the wireless communication device to perform operations, the operations including: receiving a time-varying signal carrying a PPDU on a wireless channel, the PPDU including a PHY preamble, the PHY preamble followed by a data portion, wherein the PHY preamble includes an STF, an LTF, and one or more SIG fields carrying information for interpreting the PPDU; transforming a number (N) of first time domain samples of the time-varying signal into N first modulated subcarriers based on FFT; demapping the N first modulated subcarriers into a number (Q) of frequency domain samples, wherein N>Q; transforming the Q frequency domain samples into Q symbols based on IDFT; demodulating the Q symbols; and recovering at least a portion of the PPDU from the Q demodulated symbols. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. It should be noted that the relative sizes of the following drawings may not be drawn to scale.

[0023] Figure 1 A schematic diagram of an example wireless communication network is shown.

[0024] Figure 2A Example protocol data units (PDUs) that may be used for communications between an access point (AP) and one or more wireless stations (STAs) are shown.

[0025] Figure 2B Shows Figure 2A Example fields in a PDU.

[0026] Figure 3 An example physical layer convergence protocol (PLCP) protocol data unit (PPDU) that may be used for communications between an AP and one or more STAs is shown.

[0027] Figure 4 A block diagram of an example wireless communication device is shown.

[0028] Figure 5A A block diagram of an example AP is shown.

[0029] Figure 5B A block diagram of an example STA is shown.

[0030] Figure 6 An example PPDU is shown that may be used for communication between an AP and one or more STAs according to some implementations.

[0031] Figure 7 A block diagram of an example transmit (TX) processing chain for a wireless communication device is shown in accordance with some implementations.

[0032] Figure 8 A block diagram of an example single-carrier frequency division multiplexing (SC-FDM) modulation system is shown in accordance with some implementations.

[0033] Fig.9A A block diagram of an example interface for modulating single carrier data onto orthogonal subcarriers according to some implementations is shown.

[0034] Fig. 9B Another block diagram of an example interface for modulating single carrier data onto orthogonal subcarriers according to some implementations is shown.

[0035] Fig.10 A block diagram of an example subcarrier phase adjustment system is shown in accordance with some implementations.

[0036] Fig.11 A block diagram of an example receive (RX) processing chain for a wireless communication device is shown in accordance with some implementations.

[0037] Fig.12 A block diagram of an example SC-FDM demodulation system is shown in accordance with some implementations.

[0038] Fig.13A A timing diagram depicting an example time-domain symbol sequence across a Q-point discrete Fourier transform (DFT) window is shown.

[0039] Fig. 13B Another timing diagram depicting an example time-domain symbol sequence spanning a Q-point DFT window is shown.

[0040] Fig. 13C Another timing diagram depicting an example time-domain symbol sequence spanning a Q-point DFT window is shown.

[0041] Fig.14 A timing diagram depicting an example sequence of time-domain samples across an N-point Inverse Fast Fourier Transform (IFFT) window is shown.

[0042] Fig.15 A timing diagram depicting an example sequence of time-domain samples, each spanning a corresponding N-point IFFT window, is shown.

[0043] Fig.16 Another block diagram of an example SC-FDM modulation system is shown according to some implementations.

[0044] Fig.17 A flow chart illustrating an example process for wireless communications supporting SC-FDM for a wireless local area network (WLAN) is shown.

[0045] Fig.18 A flow chart illustrating an example process for wireless communications supporting SC-FDM for WLANs is shown.

[0046] Fig.19 A block diagram of an example wireless communication device is shown in accordance with some implementations.

[0047] Fig. 20 A block diagram of an example wireless communication device is shown in accordance with some implementations.

[0048] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0049] For the purpose of describing the innovative aspects of the present disclosure, the following description is directed to certain implementations. However, those skilled in the art will readily appreciate that the teachings herein can be applied in a variety of different ways. The described implementations can be implemented in any device, system, or network capable of sending and receiving radio frequency (RF) signals in accordance with one or more of the following: the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the IEEE 802.15 standard, the Bluetooth Special Interest Group (SIG) standard, the Bluetooth SIG ... Standards, or Long Term Evolution (LTE), 3G, 4G or 5G (New Radio (NR)) standards issued by the Third Generation Partnership Project (3GPP), and other standards. The described implementation can be implemented in any device, system or network capable of sending and receiving RF signals according to one or more of the following technologies or methods: code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), single user (SU) multiple input multiple output (MIMO) and multi-user (MU) MIMO. The described implementation can also be implemented using other wireless communication protocols or RF signals suitable for use in one or more of the following: wireless personal area network (WPAN), wireless local area network (WLAN), wireless wide area network (WWAN) or Internet of Things (IOT) network.

[0050] As described above, many existing WLAN communication protocols utilize orthogonal frequency division multiplexing (OFDM) technology, which tends to produce signals with relatively high peak-to-average power ratios (PAPR). Wireless signals with high PAPR require large power backoffs for transmission. Therefore, high PAPR may affect the effective range or efficiency of OFDM transmissions. In contrast, single-carrier transmission techniques tend to produce wireless signals with significantly lower PAPRs (compared to OFDM). Various aspects of the present disclosure recognize that single-carrier transmission techniques can be used to boost the power of wireless signals without significantly increasing power consumption or reducing the efficiency of power amplifiers (compared to OFDM transmissions).

[0051] In general, various aspects relate to reducing PAPR in wireless communications, and more specifically, various aspects relate to single carrier frequency division multiplexing (SC-FDM) techniques that can be used for wireless communications in WLANs. In some aspects, a wireless communication device can modulate a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU) into a series of symbols in the time domain, and can transform a subset of the time domain symbols into a number (Q) of frequency domain samples based on a Q-point discrete Fourier transform (DFT). In some implementations, Q can be an integer value that can only be divided by 2, 3, or 5. In some implementations, the wireless communication device can add one or more pilot symbols to the subset of time domain symbols provided as input to the Q-point DFT. The wireless communication device maps the Q frequency domain samples to a number (N) of orthogonal subcarriers (representing OFDM symbols), where N>Q, and transforms the N subcarriers into N time domain samples based on an inverse fast Fourier transform (IFFT) for transmission over a wireless channel. In some aspects, the wireless communication device may further map one or more null values ​​to one or more of the N subcarriers, respectively, wherein each of the one or more null subcarriers represents a direct current (DC) subcarrier associated with a bandwidth of the wireless channel. In some aspects, the wireless communication device may directly map at least a portion of a PHY preamble (including a long training field (LTF)) of a PPDU to the N subcarriers.

[0052] Specific implementations of the subject matter described in the present disclosure may be implemented to achieve one or more of the following potential advantages. By modulating the PPDU into a series of symbols in the time domain, aspects of the present disclosure may utilize the low PAPR characteristics of a single carrier waveform to overcome path loss or extend the range of wireless communications in a WLAN. Because the time domain symbols are converted to the frequency domain and further mapped to OFDM symbols, such SC-FDM techniques may be implemented using existing WLAN (or OFDM) hardware. Aspects of the present disclosure recognize that many WLAN-capable devices also include hardware that supports various 3GPP standards such as LTE, 3G, 4G, or 5G NR. Such hardware includes one or more Q-point DFTs, where Q is only divisible by 2, 3, or 5. Therefore, by limiting the number of frequency domain samples (Q) per OFDM symbol to only a number that is divisible by 2, 3, or 5, the SC-FDM techniques of the present disclosure may be further implemented using existing 3GPP hardware. The tone plan associated with OFDM processing includes pilot subcarriers that may be used for phase tracking in the frequency domain. However, mapping pilot values ​​to specific subcarriers may increase the PAPR of the resulting signal. In contrast, inserting pilot symbols in the time domain allows phase tracking to be performed on the received signal without sacrificing the gain in PAPR associated with single-carrier transmission. On the other hand, mapping null values ​​directly to the DC subcarrier allows frequency domain processing for phase and DC offset correction (e.g., according to existing WLAN protocols).

[0053] Figure 1 A block diagram of an example wireless communication network 100 is shown. According to some aspects, the wireless communication network 100 may be an example of a wireless local area network (WLAN) such as a Wi-Fi network (and will be referred to as WLAN 100 hereinafter). For example, the WLAN 100 may be a network that implements at least one of the IEEE 802.11 family of wireless communication protocol standards (such as those defined by the IEEE 802.11-2020 specification or amendments thereof, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be). The WLAN 100 may include a plurality of wireless communication devices, such as an access point (AP) 102 and a plurality of stations (STAs) 104. Although only one AP 102 is shown, the WLAN network 100 may also include a plurality of APs 102.

[0054] Each STA in STA104 may also be referred to as a mobile station (MS), a mobile device, a mobile phone, a wireless phone, an access terminal (AT), a user equipment (UE), a subscriber station (SS), or a subscriber unit, among other possibilities. STA104 may represent various devices, such as mobile phones, personal digital assistants (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptop computers, display devices (e.g., TVs, computer monitors, navigation systems, and other devices), music or other audio or stereo equipment, remote control devices ("remote devices"), printers, kitchen or other household appliances, key cards (e.g., for passive keyless entry and start (PKES) systems), and other possibilities.

[0055] A single AP 102 and the associated set of STAs 104 may be referred to as a basic service set (BSS) managed by the corresponding AP 102 . Figure 1 Also shown is an example coverage area 108 of the AP 102, which may represent a basic service area (BSA) of the WLAN 100. The BSS may be identified to users by a service set identifier (SSID) and to other devices by a basic service set identifier (BSSID), which may be a medium access control (MAC) address of the AP 102. The AP 102 periodically broadcasts a beacon frame (“beacon”) including the BSSID to enable any STA 104 within the wireless range of the AP 102 to “associate” or re-associate with the AP 102 to establish or maintain a corresponding communication link 106 (hereinafter also referred to as a “Wi-Fi link”) with the AP 102. For example, the beacon may include an identification of a primary channel used by the corresponding AP 102 and a timing synchronization function for establishing or maintaining timing synchronization with the AP 102. The AP 102 may provide access to external networks to the respective STAs 104 in the WLAN via the corresponding communication links 106.

[0056] To establish a communication link 106 with an AP 102, each of the STAs 104 is configured to perform passive or active scanning operations (“scans”) on frequency channels in one or more frequency bands (e.g., 2.4 GHz, 5 GHz, 6 GHz, or 60 GHz bands). To perform a passive scan, the STA 104 listens for beacons transmitted by the corresponding AP 102 at periodic time intervals (measured in time units (TUs), one TU being equal to 1024 microseconds (μs)) called target beacon transmission times (TBTTs). To perform an active scan, the STA 104 generates a probe request and sequentially transmits the probe request on each channel to be scanned, and listens for probe responses from the AP 102. Each STA 104 may be configured to identify or select an AP 102 with which to associate based on the scan information obtained through the passive or active scan, and perform authentication and association operations to establish a communication link 106 with the selected AP 102. The AP 102 assigns an association identifier (AID) to the STA 104 at the end of the association operation, and the AP 102 uses the AID to track the STA 104.

[0057] Due to the increasing popularity of wireless networks, STA104 may have the opportunity to select one of multiple BSSs within the range of the STA, or select between multiple APs 102 that together form an extended service set (ESS) including multiple connected BSSs. The extended network station associated with the WLAN 100 can be connected to a wired or wireless distribution system that allows multiple APs 102 to be connected in such an ESS. In this way, the STA104 can be covered by more than one AP 102 and can be associated with different APs 102 at different times for different transmissions. In addition, after association with an AP 102, the STA104 can also be configured to periodically scan its surroundings to find a more suitable AP 102 to associate with. For example, a STA104 that is moving relative to its associated AP 102 can perform a "roaming" scan to find another AP 102 with more desirable network characteristics (such as a larger received signal strength indicator (RSSI) or a reduced traffic load).

[0058] In some cases, STA 104 can form a network without AP 102 or other devices except STA 104 itself. An example of such a network is a self-organizing network (or wireless self-organizing network). A self-organizing network can be alternatively referred to as a mesh network or a peer-to-peer (P2P) network. In some cases, a self-organizing network can be implemented in a larger wireless network (such as WLAN 100). In such an implementation, although STA 104 can use communication link 106 to communicate with each other through AP 102, STA 104 can also communicate directly with each other via direct wireless link 110. In addition, two STA 104 can communicate via direct communication link 110, regardless of whether the two STA 104 are associated with the same AP 102 and served by the same AP 102. In such a self-organizing system, one or more STAs in STA 104 can assume the role played by AP 102 in the BSS. Such STA 104 can be referred to as a group owner (GO), and can coordinate the transmission in the self-organizing network. Examples of direct wireless link 110 include a Wi-Fi direct connection, a connection established by using a Wi-Fi Tunnel Direct Link Setup (TDLS) link, and other P2P group connections.

[0059] The AP 102 and the STA 104 may operate and communicate (via corresponding communication links 106) in accordance with the IEEE 802.11 family of wireless communication protocol standards (such as those defined by the IEEE 802.11-2016 specification or its amendments, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be). These standards define WLAN radio and baseband protocols for the PHY and medium access control (MAC) layers. The AP 102 and the STA 104 send and receive wireless communications in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs) to and from each other (hereinafter also referred to as "Wi-Fi communications"). The AP 102 and STA 104 in the WLAN 100 may send PPDUs on an unlicensed spectrum, which may be a portion of a spectrum that includes frequency bands traditionally used by Wi-Fi technology, such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHz band, and the 700 MHz band. Some implementations of the AP 102 and STA 104 described herein may also communicate in other frequency bands, such as the 6 GHz band, that may support both licensed and unlicensed communications. The AP 102 and STA 104 may also be configured to communicate in other frequency bands, such as shared licensed bands, where multiple operators may have licenses to operate in the same or overlapping frequency band or bands.

[0060] Each of these frequency bands may include multiple sub-bands or multiple frequency channels. For example, PPDUs that comply with IEEE 802.11n, 802.11ac, 802.11ax, and 802.11be standard revisions may be sent on 2.4, 5 GHz, or 6 GHz frequency bands, each of which is divided into multiple 20 MHz channels. Thus, these PPDUs are sent on a physical channel with a minimum bandwidth of 20 MHz, but larger channels may be formed by channel bonding. For example, a PPDU may be sent on a physical channel with a bandwidth of 40 MHz, 80 MHz, 160, or 320 MHz by bonding multiple 20 MHz channels together.

[0061] Each PPDU is a composite structure including a PHY preamble and a payload in the form of a PHY service data unit (PSDU). The receiving device can use the information provided in the preamble to decode subsequent data in the PSDU. In an instance where a PPDU is sent on a bonded channel, the preamble field can be copied and sent in each component channel of a plurality of component channels. The PHY preamble may include both a traditional part (or "transmit preamble") and a non-traditional part (or "non-traditional preamble"). Traditional preambles can be used for packet detection, automatic gain control, and channel estimation, as well as other purposes. Traditional preambles can also be generally used to maintain compatibility with traditional devices. The format, encoding, and information provided therein of the non-traditional part of the preamble are based on the specific IEEE 802.11 protocol to be used to send the payload.

[0062] Figure 2A An example protocol data unit (PDU) 200 that can be used for wireless communication between an AP 102 and one or more STAs 104 is shown. For example, the PDU 200 can be configured as a PPDU. As shown, the PDU 200 includes a PHY preamble 202 and a PHY payload 204. For example, the preamble 202 can include a legacy portion, which itself includes a legacy short training field (L-STF) 206 that can be composed of two BPSK symbols, a legacy long training field (L-LTF) 208 that can be composed of two BPSK symbols, and a legacy signal field (L-SIG) 210 that can be composed of two BPSK symbols. The legacy portion of the preamble 202 can be configured according to the IEEE 802.11a wireless communication protocol standard. The preamble 202 can also include a non-legacy portion, which includes, for example, one or more non-legacy fields 212 that conform to an IEEE wireless communication protocol (such as IEEE 802.11ac, 802.11ax, 802.11be, or one or more later wireless communication protocols).

[0063] The L-STF 206 generally enables the receiving device to perform automatic gain control (AGC) and coarse timing and frequency estimation. The L-LTF 208 generally enables the receiving device to perform fine timing and frequency estimation, and can also perform initial estimation of the wireless channel. The L-SIG 210 generally enables the receiving device to determine the duration of the PDU, and uses the determined duration to avoid sending over the PDU. For example, the L-STF 206, L-LTF 208 and L-SIG 210 can be modulated according to a binary phase shift keying (BPSK) modulation scheme. The payload 204 can be modulated according to a BPSK modulation scheme, an orthogonal BPSK (Q-BPSK) modulation scheme, an orthogonal amplitude modulation (QAM) modulation scheme, or another suitable modulation scheme. The payload 204 may include a PSDU, which includes a data field (DATA) 214, which in turn may carry higher layer data, for example, in the form of a medium access control (MAC) protocol data unit (MPDU) or an aggregated MPDU (A-MPDU).

[0064] Figure 2B Shows Figure 2A 2. Example L-SIG 210 in PDU 200 of FIG. L-SIG 210 includes a data rate field 222, reserved bits 224, a length field 226, parity bits 228, and a tail field 230. Data rate field 222 indicates the data rate (note that the data rate indicated in data rate field 212 may not be the actual data rate of the data carried in payload 204). Length field 226 indicates the length of the packet in units of, for example, symbols or bytes. Parity bits 228 can be used to detect bit errors. Tail field 230 includes tail bits that can be used by a receiving device to terminate the operation of a decoder (e.g., a Viterbi decoder). The receiving device can use the data rate and length indicated in data rate field 222 and length field 226 to determine the duration of the packet in units of, for example, microseconds (μs) or other time units.

[0065] Figure 3An example PPDU 300 is shown that can be used for communication between an AP 102 and one or more STAs 104. As described above, each PPDU 300 includes a PHY preamble 302 and a PSDU 304. Each PSDU 304 can represent (or "carry") one or more MAC protocol data units (MPDUs) 316. For example, each PSDU 304 can carry an aggregate MPDU (A-MPDU) 306, which includes an aggregation of multiple A-MPDU subframes 308. Each A-MPDU subframe 306 can include an MPDU frame 310, which includes a MAC delimiter 312 and a MAC header 314 before the accompanying MPDU 316, and the MPDU 316 includes a data portion ("payload" or "frame body") of the MPDU frame 310. Each MPDU frame 310 can also include a frame check sequence (FCS) field 318 for error detection (e.g., the FCS field can include a cyclic redundancy check (CRC)) and padding bits 320. The MPDU 316 may carry one or more MAC service data units (MSDUs) 326. For example, the MPDU 316 may carry an aggregated MSDU (A-MSDU) 322 that includes multiple A-MSDU subframes 324. Each A-MSDU subframe 324 contains a corresponding MSDU 330, preceded by a subframe header 328, and in some cases followed by padding bits 332.

[0066] Referring back to the MPDU frame 310, the MAC delimiter 312 may serve as a marker for the start of the associated MPDU 316 and indicate the length of the associated MPDU 316. The MAC header 314 may include a plurality of fields containing information defining or indicating the characteristics or attributes of the data encapsulated within the frame body 316. The MAC header 314 includes a duration field indicating a duration extending from the end of the PPDU at least until the end of an acknowledgement (ACK) or block ACK (BA) of the PPDU to be sent by the receiving wireless communication device. The use of the duration field is used to reserve the wireless medium for the indicated duration and enable the receiving device to establish its network allocation vector (NAV). The MAC header 314 also includes one or more fields indicating an address for the data encapsulated within the frame body 316. For example, the MAC header 314 may include a combination of a source address, a transmitter address, a receiver address, or a destination address. The MAC header 314 may also include a frame control field containing control information. The frame control field may specify a frame type, such as a data frame, a control frame, or a management frame.

[0067] Figure 4 4 shows a block diagram of an example wireless communication device 400. In some implementations, the wireless communication device 400 may be a device for communicating with a STA (such as a reference Figure 1 In some implementations, the wireless communication device 400 may be an example of a device used in an AP (such as one of the STAs 104 described in the reference). Figure 1 The wireless communication device 400 is an example of a device used in one of the APs 102 described herein. The wireless communication device 400 is capable of sending (or outputting for transmission) and receiving wireless communications (e.g., in the form of wireless packets). For example, the wireless communication device can be configured to send and receive packets in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs) and medium access control (MAC) protocol data units (MPDUs) that comply with IEEE 802.11 wireless communication protocol standards (such as those defined by the IEEE 802.11-2016 specification or amendments thereof, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be).

[0068] The wireless communication device 400 may be or may include the following: a chip, a system on chip (SoC), a chipset, a package, or a device including one or more modems 402 (e.g., a Wi-Fi (IEEE 802.11 compliant) modem). In some implementations, the one or more modems 402 (collectively referred to as "modems 402") additionally include a WWAN modem (e.g., a modem compliant with 3GPP 4G LTE or 5G). In some implementations, the wireless communication device 400 also includes one or more radio units 404 (collectively referred to as "radio units 404"). In some implementations, the wireless communication device 406 also includes one or more processors, processing blocks, or processing elements 406 (collectively referred to as "processors 406") and one or more memory blocks or elements 408 (collectively referred to as "memory 408").

[0069] The modem 402 may include an intelligent hardware block or device, such as an application specific integrated circuit (ASIC) and other possibilities. The modem 402 is typically configured to implement the PHY layer. For example, the modem 402 is configured to modulate packets and output the modulated packets to the radio unit 404 for transmission on the wireless medium. The modem 402 is similarly configured to obtain modulated packets received by the radio unit 404, and demodulate the packets to provide demodulated packets. In addition to the modulator and demodulator, the modem 402 may also include digital signal processing (DSP) circuits, automatic gain control (AGC), encoders, decoders, multiplexers, and demultiplexers. For example, when in transmission mode, data obtained from the processor 406 is provided to an encoder, which encodes the data to provide encoded bits. The encoded bits are then mapped to points in the modulation constellation (using the selected MCS) to provide modulated symbols. The modulated symbols can then be mapped to a number (N SS ) of spatial streams or a number (N STS ). The modulated symbols in the corresponding spatial stream or space-time stream may then be multiplexed, transformed via an inverse fast Fourier transform (IFFT) block, and then provided to a DSP circuit for Tx windowing and filtering. The digital signal may then be provided to a digital-to-analog converter (DAC). The resulting analog signal may then be provided to a frequency up-converter and ultimately to a radio unit 404. In an implementation involving beamforming, the modulated symbols in the corresponding spatial stream may be precoded via a directional matrix before being provided to the IFFT block.

[0070] When in receive mode, a digital signal received from the radio unit 404 is provided to a DSP circuit configured to acquire the received signal, for example, by detecting the presence of the signal and estimating the initial timing and frequency offset. The DSP circuit is also configured to digitally condition the digital signal, for example, using channel (narrowband) filtering, analog impairment conditioning (such as correcting I / Q imbalance), and applying digital gain to ultimately obtain a narrowband signal. The output of the DSP circuit can then be fed to an AGC configured to determine an appropriate gain using information extracted from the digital signal (e.g., in one or more received training fields). The output of the DSP circuit is also coupled to a demodulator configured to extract modulated symbols from the signal and, for example, calculate a log-likelihood ratio (LLR) for each bit position of each subcarrier in each spatial stream. The demodulator is coupled to a decoder, which can be configured to process the LLRs to provide decoded bits. The decoded bits from all spatial streams are then fed to a demultiplexer for demultiplexing. The demultiplexed bits may then be descrambled and provided to the MAC layer (processor 406) for processing, evaluation, or interpretation.

[0071] The radio unit 404 typically includes at least one radio frequency (RF) transmitter (or "transmitter chain") and at least one RF receiver (or "receiver chain"), which can be combined into one or more transceivers. For example, the RF transmitter and receiver can include various DSP circuits including at least one power amplifier (PA) and at least one low noise amplifier (LNA), respectively. The RF transmitter and receiver can in turn be coupled to one or more antennas. For example, in some implementations, the wireless communication device 400 can include or be coupled to multiple transmit antennas (each with a corresponding transmit chain) and multiple receive antennas (each with a corresponding receive chain). The symbols output from the modem 402 are provided to the radio unit 404, which then transmits the symbols via the coupled antennas. Similarly, the symbols received via the antennas are obtained by the radio unit 404, which then provides the symbols to the modem 402.

[0072] The processor 406 may include an intelligent hardware block or device designed to perform the functions described herein, such as a processing core, a processing block, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD) (such as a field programmable gate array (FPGA)), discrete gate or transistor logic, discrete hardware components, or any combination thereof. The processor 406 processes information received through the radio unit 404 and the modem 402, and processes information to be output by the modem 402 and the radio unit 404 for transmission over a wireless medium. For example, the processor 406 may implement a control plane and a MAC layer, which is configured to perform various operations related to the generation and transmission of MPDUs, frames, or packets. The MAC layer is configured to perform or facilitate encoding and decoding of frames, spatial multiplexing, space-time block coding (STBC), beamforming and OFDMA resource allocation, and other operations or techniques. In some implementations, the processor 406 may generally control the modem 402 so that the modem performs the various operations described above.

[0073] The memory 408 may include a tangible storage medium, such as a random access memory (RAM) or a read-only memory (ROM), or a combination thereof. The memory 408 may also store non-transitory processor or computer executable software (SW) code containing instructions that, when executed by the processor 406, cause the processor to perform various operations described herein for wireless communication, including generation, transmission, reception, and interpretation of MPDUs, frames, or packets. For example, various functions of the components disclosed herein or various blocks or steps of the methods, operations, processes, or algorithms disclosed herein may be implemented as one or more modules of one or more computer programs.

[0074] Figure 5A 5 shows a block diagram of an example AP 502. For example, the AP 502 may be a reference Figure 1 1. An example implementation of AP 102 is described. AP 502 includes a wireless communication device (WCD) 510 (although AP 502 itself may also be generally referred to as a wireless communication device as used herein). For example, wireless communication device 510 may be a wireless communication device as described herein. Figure 4An example implementation of the wireless communication device 400 described herein. The AP 502 also includes a plurality of antennas 520 coupled to the wireless communication device 510 to send and receive wireless communications. In some implementations, the AP 502 additionally includes an application processor 530 coupled to the wireless communication device 510 and a memory 540 coupled to the application processor 530. The AP 502 also includes at least one external network interface 550 that enables the AP 502 to communicate with a core network or a backhaul network to gain access to an external network including the Internet. For example, the external network interface 550 may include one or both of a wired (e.g., Ethernet) network interface and a wireless network interface (such as a WWAN interface). Components of the aforementioned components may communicate directly or indirectly with other components of these components on at least one bus. The AP 502 also includes a housing that surrounds: the wireless communication device 510; the application processor 530; the memory 540; and at least portions of the antennas 520 and the external network interface 550.

[0075] Figure 5B 5 shows a block diagram of an example STA 504. For example, STA 504 may be a reference Figure 1 104. STA 504 includes a wireless communication device 515 (although STA 504 itself may also be generally referred to as a wireless communication device as used herein). For example, wireless communication device 515 may be a wireless communication device as described herein. Figure 4 An example implementation of the wireless communication device 400 described herein. The STA 504 also includes one or more antennas 525 coupled to the wireless communication device 515 to send and receive wireless communications. The STA 504 further includes an application processor 535 coupled to the wireless communication device 515 and a memory 545 coupled to the application processor 535. In some implementations, the STA 504 also includes a user interface (UI) 555 (such as a touch screen or keyboard) and a display 565, which can be integrated with the UI 555 to form a touch screen display. In some implementations, the STA 504 can also include one or more sensors 575, such as one or more inertial sensors, accelerometers, temperature sensors, pressure sensors, or altitude sensors. Components of the aforementioned components can communicate directly or indirectly with other components of these components on at least one bus. The STA 504 also includes a housing that surrounds: the wireless communication device 515; the application processor 535; the memory 545; and at least portions of the antenna 525, the UI 555, and the display 565.

[0076] As described above, many existing WLAN communication protocols utilize OFDM technology, which tends to produce signals with relatively high PAPR. Wireless signals with high PAPR require large power backoff for transmission. Therefore, high PAPR may affect the effective range or efficiency of OFDM transmission. In contrast, single-carrier transmission technology tends to produce wireless signals with significantly lower PAPR (compared to OFDM). Various aspects of the present disclosure recognize that single-carrier transmission technology can be used to boost the power of wireless signals without significantly increasing power consumption or reducing the efficiency of power amplifiers (compared to OFDM transmission).

[0077] In summary, various aspects relate to reducing PAPR in wireless communications, and more specifically, various aspects relate to SC-FDM techniques that can be used for wireless communications in WLANs. In some aspects, a wireless communication device may modulate a PPDU into a series of symbols in the time domain, and may transform a subset of the time domain symbols into a number (Q) of frequency domain samples based on a Q-point DFT. In some implementations, Q may be an integer value that is only divisible by 2, 3, or 5. In some implementations, a wireless communication device may add one or more pilot symbols to a subset of the time domain symbols, which is provided as an input to the Q-point DFT. The wireless communication device maps the Q frequency domain samples to a number (N) of orthogonal subcarriers (representing OFDM symbols), where N>Q, and transforms the N subcarriers into N time domain samples based on an IFFT for transmission over a wireless channel. In some aspects, the wireless communication device may also map one or more null values ​​to one or more of the N subcarriers, respectively, where each of the one or more null subcarriers represents a DC subcarrier associated with the bandwidth of the wireless channel. In some aspects, the wireless communication device may map at least a portion of a PHY preamble (including the LTF) of a PPDU directly to the N subcarriers.

[0078] Specific implementations of the subject matter described in the present disclosure may be implemented to achieve one or more of the following potential advantages. By modulating the PPDU into a series of symbols in the time domain, aspects of the present disclosure may utilize the low PAPR characteristics of a single carrier waveform to overcome path loss or extend the range of wireless communications in a WLAN. Because the time domain symbols are converted to the frequency domain and further mapped to OFDM symbols, such SC-FDM techniques may be implemented using existing WLAN (or OFDM) hardware. Aspects of the present disclosure recognize that many WLAN-capable devices also include hardware that supports various 3GPP standards such as LTE, 3G, 4G, or 5G NR. Such hardware includes one or more Q-point DFTs, where Q is only divisible by 2, 3, or 5. Therefore, by limiting the number of frequency domain samples (Q) per OFDM symbol to only a number that is divisible by 2, 3, or 5, the SC-FDM techniques of the present disclosure may be further implemented using existing 3GPP hardware. The tone plan associated with OFDM processing includes pilot subcarriers that may be used for phase tracking in the frequency domain. However, mapping pilot values ​​to specific subcarriers may increase the PAPR of the resulting signal. In contrast, inserting pilot symbols in the time domain allows phase tracking to be performed on the received signal without sacrificing the gain in PAPR associated with single-carrier transmission. On the other hand, mapping null values ​​directly to the DC subcarrier allows frequency domain processing for phase and DC offset correction (e.g., according to existing WLAN protocols).

[0079] As reference Figure 2A , 2B As described in and 3, many existing PPDU formats include a PHY preamble 202 with legacy fields (such as L-STF 206, L-LTF 208, and L-SIG 210) and a non-legacy field 212. The legacy field is common to different PPDU formats and provides backward compatibility for legacy WLAN devices operating on carrier frequencies below 7 GHz (also referred to as "below 7 GHz" bands). However, new WLAN communication protocols are being developed to implement enhanced WLAN communication features (such as higher throughput and wider bandwidth) that require even higher carrier frequencies (such as in the 45 GHz or 60 GHz bands). Aspects of the present disclosure recognize that there are currently no legacy WLAN devices operating at carrier frequencies above 7 GHz. Therefore, in some aspects, a new "green field" PPDU format can be designed for wireless communications at carrier frequencies above 7 GHz. More specifically, the green field PPDU format can be optimized for communications at carrier frequencies above 7 GHz, for example, by reducing or eliminating redundant fields or signaling that would otherwise be included for backward compatibility with legacy WLAN devices.

[0080] Figure 6 An example PPDU 600 that can be used for communication between an AP and one or more STAs according to some implementations is shown. The PPDU 600 includes a PHY preamble 601, which is followed by a data portion 602 and a packet extension (PE) or one or more training fields (TRN) 603. The PHY preamble 601 includes a short training field (STF), a long training field (LTF), and a signal (SIG) field. The STF can be used for packet detection, AGC, and timing or frequency offset estimation, while the LTF can be used for channel estimation (or fine timing and frequency offset estimation). In some implementations, when multiple spatial streams (N SS >1), the PHY preamble 601 may include one or more additional LTFs (following the SIG field).

[0081] The SIG field may carry any information necessary to interpret or demodulate the PPDU 600. Example demodulation information may include information about bandwidth, length, modulation and coding scheme (MCS), number of spatial streams (N), and the like. SS ), BSS color, padding, PE ambiguity, or low-density parity check (LDPC) additional symbols, and other examples. In some implementations, the SIG field may also carry beam management information that indicates whether the PPDU 600 is associated with a beamforming training operation or various parameters associated with a beamforming training operation. Example beam management information may include PPDU type, training direction, beam tracking request, training length, countdown, sector ID, antenna ID, best antenna ID, best sector ID, number of RX sectors or RX antennas of the transmitting device, or signal-to-noise ratio (SNR) report, and other examples.

[0082] Figure 7 700 is a block diagram of an example TX processing chain for a wireless communication device according to some implementations. In some aspects, the wireless communication device may be Figure 4 The TX processing chain 700 is configured to process a PPDU 701 for transmission as an RF signal 705. In some implementations, the PPDU 701 may conform to an existing PPDU format for wireless communications in the sub-7 GHz band (such as reference Figure 2A , 2B and 3). In some other implementations, PPDU 701 may conform to a greenfield PPDU format designed for carrier frequencies above 7 GHz (such as Figure 6 PPDU 600). For simplicity, Figure 7Only a single spatial stream of the TX processing chain 700 is depicted in FIG. In actual implementations, the TX processing chain 700 may include any number of spatial streams.

[0083] The TX processing chain 700 includes a constellation mapper 710, an SC-FDM modulator 720, an RF mixer 730, and a power amplifier (PA) 740. The constellation mapper 710 maps the PPDU 701 to one or more time domain (TD) symbols 702 associated with a modulation scheme. Exemplary suitable modulation schemes include binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), and quadrature amplitude modulation (QAM), among other examples. The SC-FDM modulator 720 modulates the TD symbols 702 onto a set of orthogonal subcarriers and converts the modulated subcarriers into a time-varying TX signal 703. The RF mixer 730 up-converts the TX signal 703 to a carrier frequency, and the power amplifier 740 amplifies the resulting RF signal 705 for transmission via one or more antennas 750. For example, the RF mixer 730 may modulate the TX signal 703 onto a local oscillator (LO) signal 704 oscillating at a carrier frequency.

[0084] In some aspects, existing WLAN hardware may be repurposed to support single carrier transmission of PPDUs. For example, the SC-FDM modulator 720 may transform the TD symbol 702 into a frequency domain (FD) sample that may be mapped to a set of orthogonal subcarriers. In some implementations, the SC-FDM modulator 720 may reuse existing OFDM hardware to map the FD samples onto orthogonal subcarriers and convert the orthogonal subcarriers into TX signals 703. Thus, the SC-FDM modulator 720 may retain the single carrier characteristics (such as low PAPR) associated with the TD symbol 702 while transmitting the TD symbol 702 over a wireless channel using OFDM techniques. More specifically, the SC-FDM modulator 720 reduces the PAPR of the RF signal 705 (compared to conventional OFDM transmissions), thereby reducing the power backoff required by the power amplifier 740. Thus, the power amplifier 740 may operate more efficiently, for example, to boost the power of the RF signal 705. This boosting of RF signal 705 may be used to extend the range of wireless communications or to overcome path loss at higher carrier frequencies.

[0085] Figure 8A block diagram of an example SC-FDM modulation system 800 according to some implementations is shown. In some aspects, the SC-FDM modulation system 800 can be configured to modulate the PPDU 801 onto the TX signal 807. More specifically, the SC-FDM modulation system 800 can convert the PPDU 801 from the time domain to the frequency domain so that the resulting TX signal 807 can be transmitted using OFDM techniques while preserving the single carrier characteristic of the PPDU 801 in the time domain. In some implementations, the SC-FDM modulation system 800 can be Figure 7 An example of an SC-FDM modulator 720. Figure 7 , PPDU 801 may be an example of TD symbol 702 , and TX signal 807 may be an example of TX signal 703 .

[0086] The SC-FDM modulation system 800 includes a Q-point DFT 810, a tone mapper 820, an N-point IFFT 830, a CP adder 840, and a DAC 850. The Q-point DFT 810 converts the PPDU 801 from the time domain to the frequency domain. In some aspects, the Q-point DFT 810 can convert a number (M) of data symbols (such as Figure 7 TD symbol 702) is transformed into a number (Q) of frequency domain (FD) samples 803. For example, Q can represent the size of the resource unit (RU) or multi-RU (M-RU) to which the FD sample 803 is mapped. In some implementations, a number (K) of pilot symbols can also be provided as input to the Q-point DFT 810 (where M+K=Q). The pilot symbols can be associated with a phase tracking operation that can be performed in the time domain by the receiving device. Various aspects of the present disclosure recognize that the OFDM tone plan associated with existing versions of the IEEE 802.11 standard specifies the number of pilot subcarriers for a given RU size. In some implementations, K can be equal to the number of pilot subcarriers specified by the existing OFDM tone plan for the size of the RU or M-RU to which the FD sample 803 is mapped.

[0087] In some implementations, Q may be an integer value equal to the size of any RU or M-RU defined by an existing version of the IEEE 802.11 standard (such as 26, 52, 52+26, 106, 106+26, 242, 484, 484+242, 996, 996+484, 996x2, 996x2+484, 99x3, 996x3+484, or 996x4). In some other implementations, Q may be an integer value that is only divisible by 2, 3, or 5. In such implementations, the size of an existing RU or M-RU may be reduced or increased to the nearest multiple of 2, 3, or 5. For example, a 26-subcarrier RU may be reduced to 25 subcarriers, a 52-subcarrier RU may be reduced to 50 subcarriers, a 106-subcarrier RU may be reduced to 100 subcarriers, a 132-subcarrier RU may be reduced to 128 subcarriers, a 242-subcarrier RU may be reduced to 240 subcarriers, a 484-subcarrier RU may be reduced to 480 subcarriers, a 726-subcarrier RU may be reduced to 720 subcarriers, and a 996-subcarrier RU may be reduced to 972 subcarriers. In some implementations, the reduced RU size may result in fewer pilot symbols being provided as input to the Q-point DFT 810. For example, a 480-subcarrier RU may be associated with 12 pilot symbols (compared to 16 pilot subcarriers associated with a 484-subcarrier RU). In some other implementations, the RU size may be increased by adding one or more "unused" subcarriers (such as any subcarriers across a given bandwidth that are not assigned to a RU or M-RU according to an existing OFDM tone plan. For example, a 26-subcarrier RU may be expanded to 27 subcarriers by adding one or more unused subcarriers associated with a 20 MHz tone plan.

[0088] The tone mapper 820 maps the FD samples 803 to a number (N) of subcarriers to produce modulated subcarriers 804. The N subcarriers may represent OFDM symbols in the frequency domain. In other words, the N subcarriers may span the bandwidth associated with the wireless channel on which the TX signal 807 is sent. In some aspects, N may be greater than Q. Therefore, the tone mapper 820 may map the FD samples 803 to a subset of the Q-subcarrier RU or M-RU of the N subcarriers representing a portion of the channel bandwidth spanning. In some implementations, the remaining NQ subcarriers may be left unused. In some other implementations, at least some of the remaining NQ subcarriers may be modulated (such as according to OFDMA) using data associated with another RU or M-RU. The N-point IFFT 830 transforms the modulated subcarrier 804 from the frequency domain to the time domain as N time domain (TD) samples 805. The CP adder 840 adds a cyclic prefix to the N time domain samples 805 to generate a plurality of prefix samples 806. The DAC 850 converts the prefix samples 806 into a TX signal 807.

[0089] The existing PPDU format includes a PHY preamble designed to be processed in the frequency domain. For example, the existing version of the IEEE 802.11 standard defines STF and LTF sequences that are mapped to specific subcarrier indices associated with the existing OFDM tone plan. In some aspects, at least a portion of the PHY preamble of the PPDU 801 can be directly mapped to N subcarriers in the frequency domain. For example, the PHY preamble can be directly input to the tone mapper 820 (bypassing the Q-point DFT 810), and the tone mapper 820 maps the PHY preamble to the same RU or M-RU as the data portion of the PPDU 801. Therefore, various aspects of the present disclosure can reuse the existing PHY preamble design for the PPDU sent using SC-FDM. However, as described above, mapping frequency domain symbols to specific subcarriers may increase the PAPR of the PPDU 801. In particular, various aspects of the present disclosure recognize that the existing LTF sequences associated with large M-RUs (such as 484+252-subcarrier M-RUs) may create a PAPR bottleneck. For example, the high PAPR associated with such LTF sequences may cause power amplifiers (such as Figure 7 The PA 740) operates in the saturation region, thereby distorting the TX signal 807.

[0090] In some aspects, an existing LTF sequence may be mapped to one or more LTFs in the PHY preamble of the PPDU 801. In some implementations, the LTFs may be repeated (in the time domain) to compensate for losses in channel estimation due to distortion of the TX signal 807. In such implementations, the number of LTFs in the PHY preamble may be greater than the number of spatial streams over which the PPDU 801 is transmitted. In some other implementations, the LTF symbols may be modified (in a manner unknown to the receiver) to reduce the PAPR associated with the PPDU 801. Example modifications may include applying a different phase rotation to each component RU (in an M-RU) or mapping a non-zero value (with special scaling) to one or more DC subcarriers, among other examples.

[0091] In some other aspects, a new LTF sequence may be designed for a PPDU sent using SC-FDM. Such an LTF sequence may be referred to herein as an "SC-LTF" sequence. In some implementations, the SC-LTF sequence may be modulated according to a higher order modulation scheme (higher than BPSK) to reduce the PAPR of the PPDU 801 in the time domain. In some other implementations, the SC-LTF sequence may be constructed based on a Zadoff-Chu sequence. For example, each value (x) of the Zadoff-Chu sequence may be expressed as a function of its sequence index (m), root index (u), and sequence length (N), as shown in Equation 1:

[0092]

[0093] Aspects of the present disclosure recognize that the Zadoff-Chu sequence in Equation 1 exhibits time-frequency duality for prime values ​​of sequence length N. In other words, the time domain values ​​of the Zadoff-Chu sequence (input to the DFT) follow the same (circular) pattern or distribution as the frequency domain values ​​of the Zadoff-Chu sequence (output by the DFT). Therefore, by mapping a Zadoff-Chu sequence with a prime length N to the LTFs of the PPDU 801, aspects of the present disclosure can reduce the PAPR of the PPDU 801 in both the time and frequency domains.

[0094] In some implementations, the length N of the Zadoff-Chu sequence can be associated with the size of the RU or M-RU to which the PPDU 801 is mapped. In such an implementation, N can be set to a maximum prime number that does not exceed the number of subcarriers in the associated RU or M-RU, and the Zadoff-Chu sequence can be extended to be equal to the number of subcarriers in the RU or M-RU by cyclically shifted copies. Therefore, RUs and M-RUs of different sizes can be associated with different values ​​of N. Table 1 summarizes example sequence lengths N that can be associated with various RU sizes.

[0095] Table 1

[0096]

[0097]

[0098] In some other implementations, the length N of the Zadoff-Chu sequence can be associated with the bandwidth of the wireless channel over which the PPDU 801 (or TX signal 807) is sent. In such an implementation, N can be set to a maximum prime number that does not exceed the total number of subcarriers spanning the bandwidth of the wireless channel, and the Zadoff-Chu sequence can be extended to be equal to the number of subcarriers spanning the channel bandwidth by cyclically shifted copies. Therefore, the value of the Zadoff-Chu sequence mapped to each RU or M-RU can depend on the subcarrier index spanned by the RU or M-RU. Table 2 summarizes example sequence lengths N that can be associated with various bandwidths.

[0099] Table 2

[0100] Number of subcarriers across the bandwidth Zadoff-Chu sequence length (N) 242 241 484 479 996 991 996x2 1987 996x4 3967

[0101] Fig.9A A block diagram of an example interface 900 for modulating single carrier data onto orthogonal subcarriers according to some implementations is shown. In some implementations, the interface 900 may be Figure 8 The interface 900 includes a tone mapping component 902 and a phase rotation component 904. The tone mapping component 902 maps a number (Q) of samples 901 to a number (N) of subcarriers 903 in the frequency domain (where N>Q). Figure 8 , Q samples 901 may be an example of FD samples 803. Therefore, Q samples 901 may represent a series of data symbols and a number of pilot symbols associated with a PPDU in the time domain. Fig.9A In the example of , the tone mapping component 902 is configured to modulate the Q samples 901 onto Q consecutive subcarrier indices associated with N subcarriers. For example, the Q consecutive subcarrier indices may represent a RU or an M-RU. The remaining NQ subcarriers may be left unused or modulated with samples associated with other RUs or M-RUs (not shown for simplicity).

[0102] In some aspects, the tone mapping component 902 may also map one or more null values ​​to one or more subcarrier indices associated with a DC subcarrier, respectively. For example, such subcarrier indices may represent a DC subcarrier associated with a bandwidth of a wireless channel and may be used by a receiving device for DC offset correction. In some implementations, the number of DC subcarriers inserted by the tone mapping component 902 may be equal to the number of DC subcarriers specified by an existing OFDM tone plan for a given channel bandwidth. Various aspects of the present disclosure recognize that directly inserting a DC subcarrier in the frequency domain may increase the PAPR of the resulting signal. In some implementations, the phase rotation component 904 may apply a series of phase rotations to the N subcarriers 903, which mitigates the PAPR associated with the DC subcarrier. In other words, the phase rotation component 904 may produce N phase-rotated subcarriers 905 associated with a lower PAPR (compared to the N subcarriers 903). Reference Figure 8 , the phase-rotated subcarrier 905 can be an example of the modulated subcarrier 804.

[0103] Fig. 9B Another block diagram of an example interface 910 for modulating single carrier data onto orthogonal subcarriers according to some implementations is shown. In some implementations, the interface 910 may be Figure 8 The interface 910 includes a tone mapping component 912 and a phase rotation component 914. The tone mapping component 912 maps a number (Q) of samples 911 to a number (N) of subcarriers 913 in the frequency domain (where N>Q). Figure 8 , Q samples 911 may be an example of FD samples 803. Thus, Q samples 911 may represent a series of data symbols and a number of pilot symbols associated with a PPDU in the time domain. Fig. 9B In the example of , the tone mapping component 902 is configured to modulate the Q samples 901 onto Q non-contiguous subcarrier indices associated with N subcarriers. For example, the Q non-contiguous subcarrier indices may represent a RU or M-RU (or distributed RU). The remaining NQ subcarriers may be left unused or modulated with samples associated with other RUs or M-RUs (not shown for simplicity).

[0104] In some aspects, the tone mapping component 912 may also map one or more null values ​​to one or more subcarrier indices associated with a DC subcarrier, respectively. For example, such subcarrier indices may represent a DC subcarrier associated with the bandwidth of a wireless channel and may be used by a receiving device for DC offset correction. In some implementations, the number of DC subcarriers inserted by the tone mapping component 912 may be equal to the number of DC subcarriers specified by an existing OFDM tone plan for a given channel bandwidth. Various aspects of the present disclosure recognize that directly inserting a DC subcarrier in the frequency domain may increase the PAPR of the resulting signal. In some implementations, the phase rotation component 914 may apply a series of phase rotations to the N subcarriers 913, which mitigates the PAPR associated with the DC subcarrier. In other words, the phase rotation component 914 may produce N phase-rotated subcarriers 915 associated with a lower PAPR (compared to the N subcarriers 913). Reference Figure 8 , the phase-rotated subcarrier 915 can be an example of the modulated subcarrier 804.

[0105] Fig.10 A block diagram of an example subcarrier phase adjustment system 1000 according to some implementations is shown. More specifically, the phase adjustment system 1000 can support π / 2-BPSK modulation. In some implementations, the phase adjustment system 1000 can be an example of the phase rotation component 914 of FIG. 9. Thus, the phase adjustment system 1000 can apply a series of phase rotations to a number (N) of subcarriers 1002 to produce N phase-rotated subcarriers 1004. Referring to FIG. 9, the N subcarriers 1002 can be an example of the N subcarriers 913, and the phase-rotated subcarrier 1004 can be an example of the phase-rotated subcarrier 915.

[0106] Phase adjustment system 1000 includes a number (M) of phase rotators 1010(1)-1010(M). Each of phase rotators 1010(1)-1010(M) applies a set of phase rotations to a corresponding subset (or "segment") of N subcarriers 1002. More specifically, N subcarriers 1002 may be relatively evenly distributed among the M segments in order of increasing subcarrier index such that each segment includes substantially the same number of subcarriers 1002. Fig.10As shown, the subcarrier segments are numbered (or indexed) from 1 to M. The subcarriers 1002 in the 1st segment are associated with consecutive subcarrier indices 1 to i; the subcarriers 1002 in the 2nd segment are associated with consecutive subcarrier indices i+1 to j; the subcarriers 1002 in the 3rd segment are associated with consecutive subcarrier indices j+1 to k; the subcarriers 1002 in the 4th segment are associated with consecutive subcarrier indices k+1 to l; and the subcarriers 1002 in the Mth segment are associated with consecutive subcarrier indices m to N.

[0107] In some aspects, the phase adjustment system 1000 may apply a different phase rotation pattern to subcarriers 1002 in odd-numbered segments (such as segments 1 and 3) than to subcarriers 1002 in even-numbered segments (such as segments 2 and 4). For example, each of the phase rotators 1010(1) and 1010(3) may apply a series of first phase rotations to subcarriers 1002 in segments 1 and 3, respectively, and each of the phase rotators 1010(2) and 1010(4) may apply a series of second phase rotations to subcarriers 1002 in segments 2 and 4, respectively, wherein the series of first phase rotations is different from the series of second phase rotations.

[0108] In some implementations, phase rotators associated with odd-numbered segments may apply a 90° phase shift to every other subcarrier 1002 starting from the second subcarrier index in its corresponding segment (which results in the phase rotation pattern [1i1i ...] being applied over a range of subcarrier indices across each odd-numbered segment). For example, phase rotator 1010(1) may apply a 90° phase shift to subcarrier 1002 associated with subcarrier index 2 and every other subcarrier index thereafter across segment 1. Similarly, phase rotator 1010(3) may apply a 90° phase shift to subcarrier 1002 associated with subcarrier index j+2 and every other subcarrier index thereafter across segment 3.

[0109] In some implementations, phase rotators associated with even-numbered segments may apply a 90° phase shift to every other subcarrier 1002 starting with the first subcarrier index in its corresponding segment (resulting in a phase shift pattern [i 1i 1…] being applied over a range of subcarrier indices across each even-numbered segment). For example, phase rotator 1010(2) may apply a 90° phase shift to subcarrier 1002 associated with subcarrier index i+1 and every other subcarrier index thereafter across segment 2. Similarly, phase rotator 1010(4) may apply a 90° phase shift to subcarrier 1002 associated with subcarrier index k+1 and every other subcarrier index thereafter across segment 4.

[0110] As an example, the phase adjustment system 1000 can subdivide a 242-subcarrier OFDM symbol (N=242) into 60 substantially equal segments (M=60). For example, among the 60 subcarrier segments, 58 segments can be assigned 4 subcarriers each, and the remaining 2 segments can be assigned 5 subcarriers each. Each phase rotator associated with an odd-numbered segment can apply a phase rotation pattern [1i 1i] or [1i 1i 1] to 4 or 5 subcarriers in its segment, respectively, and each phase rotator associated with an even-numbered segment can apply a phase rotation pattern [i1i1] or [i 1i 1i] to 4 or 5 subcarriers in its segment, respectively.

[0111] Thus, given 242 subcarriers subdivided into 60 segments, the phase adjustment system 1000 can apply a 90° phase shift to the subcarriers associated with the following subcarrier indices: 2, 4, 5, 7, 10, 12, 13, 15, 18, 20, 21, 23, 26, 28, 29, 31, 34, 36, 37, 39, 42, 44, 45, 47, 50, 52, 53, 55, 58, 60, 61, 63, 66, 68, 69, 71, 74, 76, 77, 79, 82, 84, 85, 87, 90, 92, 93, 95, 98, 100, 101, 103, 106, 108, 109, 111, 114, 116, 117, 119, 121、122、124、126、127、129、132、134、135、137、140、142、143、145、148、150、151、153、156、158、159、161、164、166、167、169、172、174、175、177、180、 182, 183, 185, 188, 190, 191, 193, 196, 198, 199, 201, 204, 206, 207, 209, 212, 214, 215, 217, 220, 222, 223, 225, 228, 230, 231, 233, 236, 238, 239 and 241.

[0112] Fig.11 1 shows a block diagram of an example RX processing chain 1100 for a wireless communication device according to some implementations. In some aspects, the wireless communication device may be Figure 4 The RX processing chain 1100 is configured to recover the PPDU 1105 from the received RF signal 1101. In some implementations, the PPDU 1105 may conform to an existing PPDU format for wireless communications in the sub-7 GHz band (such as reference Figure 2A , 2Band 3). In some other implementations, the PPDU 1105 may conform to a greenfield PPDU format designed for carrier frequencies above 7 GHz (such as Figure 6 PPDU600). For simplicity, Fig.11 Only a single spatial stream of the RX processing chain 1100 is depicted. In actual implementations, the RX processing chain 1100 may include any number of spatial streams.

[0113] The RX processing chain 1100 includes a low noise amplifier (LNA) 1120, an RF mixer 1130, an SC-FDM demodulator 1140, and a constellation demapper 1150. The LNA 1120 amplifies an RF signal 1101 received via one or more antennas 1110, and the RF mixer 1130 down-converts the RF signal 1101 to a baseband RX signal 1103. For example, the RF mixer 1130 may demodulate the RF signal 1101 based on an LO signal 1102 oscillating at a carrier frequency. The SC-FDM demodulator 1140 demodulates the RX signal 1103 into one or more time domain (TD) symbols 1104 associated with a modulation scheme. In some implementations, the SC-FDM demodulator 1140 may invert the RF signal 1101 received by the LO signal 1102. Figure 7 The constellation demapper 1150 demaps the TD symbols 1104 to recover the PPDU 1105. In some implementations, the constellation demapper 1150 may invert the Figure 7 The mapping is performed by the constellation mapper 710.

[0114] Fig.12 1 shows a block diagram of an example SC-FDM demodulation system 1200 according to some implementations. In some aspects, the SC-FDM demodulation system 1200 can be configured to recover the PPDU 1206 from the RX signal 1201. More specifically, the SC-FDM demodulation system 1200 can invert the Figure 8 In some implementations, the SC-FDM demodulation system 1200 may be Fig.11 An example of an SC-FDM demodulator 1140. Fig.11 , RX signal 1201 may be an example of RX signal 1103 , and PPDU 1206 may be an example of TD symbol 1104 .

[0115] The SC-FDM demodulation system 1200 includes an ADC 1210, a CP remover 1220, an N-point fast Fourier transform (FFT) 1230, a tone demodulator 1240, and a Q-point inverse discrete Fourier transform (IDFT) 1250. The ADC 1210 converts the RX signal 1201 into a set of time domain (TD) samples 1202. In some aspects, the ADC 1210 can be used in a manner similar to Figure 8 The DAC 850 operates at the same sampling rate as the DAC 850. The CP remover 1220 removes the cyclic prefix from the TD samples 1202 to generate a number (N) of prefix-free samples 1203. The N-point FFT 1230 transforms the N prefix-free samples 1203 from the time domain to the frequency domain as N modulated subcarriers 1204.

[0116] The tone demodulator 1240 is configured to perform equalization and demap the modulated subcarrier 1204 into a number (Q) of frequency domain (FD) samples 1205. In some aspects, the tone demodulator 1240 may invert the Figure 8 The tone mapper 820 or Fig.9A and 9B The mapping is performed by any of the interfaces 900 or 910 of the PPDU 1206. For example, the tone demodulator 1240 can obtain FD samples 1205 (where N>Q) from a subset of N modulated subcarriers 1204 representing a Q-subcarrier RU or an M-RU. In some implementations, the tone demodulator 1240 can recover a portion of the PHY preamble of the PPDU 1206 (such as the SIG field) from the FD samples 1205.

[0117] The Q-point IDFT 1250 transforms the FD samples 1205 from the frequency domain to the time domain to recover the PPDU 1206. In some aspects, the Q-point IDFT 1250 may invert the Figure 8 The FD samples 1205 may be transformed into a number (M) of data symbols and a number (K) of pilot symbols 1207 (where M+K=Q) associated with the PPDU 1206 in the time domain. In some implementations, the wireless communication device may also perform a phase tracking operation in the time domain based on the recovered pilot symbols 1207. More specifically, the wireless communication device may estimate (and correct) the phase error in the received PPDU 1206 by comparing the values ​​of the pilot symbols 1207 with their ideal (or known) values.

[0118] For example, the received signal (R) modulated on the mth subcarrier index of the nth OFDM symbol (such as at the output of the N-point FFT 1230) m,n ) can be expressed as the value of the signal sent (X m,n), each subcarrier channel (H m ), phase noise (e j θ ) and noise (N m,n ) function:

[0119] R m,n =H m e jθ X m,n +N m,n

[0120] After equalization and conversion to the time domain (such as at the output of the Q-point IDFT 1250), each sample (y m,n ) can be expressed as:

[0121]

[0122] More specifically, the timing of the pilot symbol (t m,n ) can be expressed as a function of the ideal pilot symbol value (p) and the time domain noise (v) sent at such a time:

[0123]

[0124] Therefore, the phase slope or offset between the mth pilot symbol and the kth pilot symbol is It can be expressed as:

[0125]

[0126] In some implementations, the wireless communication device may use one or more data symbols (associated with the PPDU 1206) to further enhance or improve the accuracy of the phase offset estimate (e.g., by comparing the value of the received data symbol to the hard decision value of the data symbol used for reference). In some implementations, the wireless communication device may use the phase estimate To correct the phase of each data symbol in the current OFDM symbol. In some other implementations, the wireless communication device may use the phase estimation To correct the phase of each data symbol in the subsequent OFDM symbol.

[0127] Fig.13A A timing diagram 1300 depicting an example time domain symbol sequence across a Q-point DFT window is shown. Fig.13A As shown, the Q-point DFT window spans the duration from time t0 to t3. The time domain symbol sequence includes a number (K) of pilot symbols interspersed between a number (M) of data symbols (where M+K=Q). In some implementations, the M data symbols and the K pilot symbols may be respectively Figure 8PPDU 801 and pilot symbol 802 (or respectively Fig.12 1206 and pilot symbols 1207). Fig.13A In the example of , the pilot symbols are concentrated in the middle of the time domain sequence (such as between time t1 and t2), and the data symbols are distributed between time t0 to t1 and between time t2 to t3.

[0128] In some implementations, the receiving device may estimate the slope of the phase ramp associated with the received time-domain symbol sequence based on the pilot symbols received between times t1 and t2. (such as reference Fig.12 The receiving device can also use the phase estimation To correct the phase of the data symbols received between time t0 and t1 and between time t2 and t3.

[0129] Fig. 13B Another timing diagram 1310 is shown depicting an example time domain symbol sequence across a Q-point DFT window. Fig. 13B As shown, the Q-point DFT window spans the duration from time t0 to t5. The time domain symbol sequence includes a number (K) of pilot symbols interspersed between a number (M) of data symbols (where M+K=Q). In some implementations, the M data symbols and the K pilot symbols may be respectively Figure 8 PPDU 801 and pilot symbol 802 (or respectively Fig.12 1206 and pilot symbols 1207). Fig.13A Compared with the pilot symbol, Fig. 13B The pilot symbols in are more evenly distributed within the time domain sequence, such as between time t1 and t2 and between time t3 and t4. The data symbols are distributed between time t0 and t1, between time t2 and t3, and between time t4 and t5.

[0130] In some implementations, the receiving device may estimate the slope of the phase ramp associated with the received time-domain symbol sequence based on pilot symbols received between times t1 and t2, pilot symbols received between times t3 and t4, or any combination thereof. (such as reference Fig.12 The receiving device can also use the phase estimation To correct the phase of the data symbols received between time t0 and t1, between time t2 and t3, and between time t4 and t5.

[0131] Fig. 13C Another timing diagram 1320 depicting an example time domain symbol sequence across a Q-point DFT window is shown. Fig. 13CAs shown, the Q-point DFT window spans the duration from time t0 to t9. The time domain symbol sequence includes a number (K) of pilot symbols interspersed between a number (M) of data symbols (where M+K=Q). In some implementations, the M data symbols and the K pilot symbols may be respectively Figure 8 PPDU 801 and pilot symbol 802 (or respectively Fig.12 1206 and pilot symbols 1207). Fig. 13B Compared with the pilot symbol, Fig. 13C The pilot symbols in the time domain are more evenly distributed within the time domain sequence, such as between time t1 and t2, between time t3 and t4, between time t5 and t6, and between time t7 and t8. The data symbols are distributed between time t0 and t1, between time t2 and t3, between time t4 and t5, between time t6 and t7, and between time t8 and t9.

[0132] In some implementations, the receiving device may estimate the slope of the phase ramp associated with the received time-domain symbol sequence based on pilot symbols received between times t1 and t2, pilot symbols received between times t3 and t4, pilot symbols received between times t5 and t6, pilot symbols received between times t7 and t8, or any combination thereof. (such as reference Fig.12 The receiving device can also use the phase estimation To correct the phase of the data symbols received between time t0 and t1, between time t2 and t3, between time t4 and t5, between time t6 and t7, and between time t8 and t9.

[0133] Fig.14 A timing diagram 1400 depicting an example sequence of time-domain samples spanning an N-point IFFT window is shown. Fig.14 As shown, the N-point IFFT window spans the duration from time t1 to t3. In some implementations, the sequence of time domain samples spanning the N-point IFFT window (such as between time t1 and t3) may be Figure 8 TD sample 805 (or Fig.12 More specifically, the time domain sample sequence includes a plurality of samples associated with data symbols (also referred to as "data samples") and a plurality of samples associated with pilot symbols (also referred to as "pilot samples"). Fig.14 In the example of , the pilot samples are concentrated at the end of the time domain sequence (such as between time t2 and t3), and the data symbols are distributed between time t1 and t2. As a result of cyclic prefixing, the pilot samples (and part of the data samples) are copied to the beginning of the time domain sequence (such as between time t0 and t1).

[0134] In some implementations, the receiving device may estimate the slope of the phase ramp associated with the received time-domain symbol sequence based on the pilot symbols received between times t0 and t1 and the pilot symbols received between times t2 and t3. In other words, instead of discarding the cyclic prefix, the receiving device can compare the phase offset between the pilot samples in the cyclic prefix and the pilot samples at the end of the IFFT window. Because the pilot samples in the cyclic prefix have the same values ​​as the pilot samples at the end of the IFFT window, the receiving device can use either set of pilot samples as a reference. In some implementations, the receiving device can also refine the phase estimate based on the pilot symbols demodulated from the pilot samples received between time t2 and t3. Estimate (e.g., refer to Figure 12-13C The receiving device can also use the phase estimation To correct the phase of the data symbols received between time t1 and t2.

[0135] Fig.15 A timing diagram 1500 is shown depicting an example sequence of time-domain samples each spanning a corresponding N-point IFFT window. Fig.15 As shown, the first N-point IFFT window spans the duration from time t1 to t3, and the second N-point IFFT window spans the duration from time t3 to t5. In some implementations, each time domain sample sequence spanning the corresponding N-point IFFT window may be Figure 8 TD sample 805 (or Fig.12 More specifically, each time domain sample sequence includes a plurality of data samples and a plurality of samples associated with a guard interval (also referred to as "GI samples"). Fig.15 As shown, the GI samples are concentrated at the end of each time domain sequence (such as between time t2 and t3 and between time t4 and t5), and the data symbols are distributed between time t1 and t2 and between time t3 and t4. In some aspects, the GI samples can provide a buffer to mitigate inter-symbol interference between consecutive data sample sequences (instead of a cyclic prefix).

[0136] In some implementations, the GI samples may carry a known pattern of values ​​(such as pilot values). More specifically, the same pattern of GI values ​​may be repeated in each guard interval to maintain a cyclic structure similar to a cyclic prefix. In such an implementation, a copy of the GI value may be sent before any data sample (such as between time t0 and t1) so that the preliminary guard interval precedes the first OFDM symbol associated with the PPDU. Thus, the GI value may be used by a receiving device for channel estimation, carrier frequency offset (CFO) correction, phase noise mitigation, and phase tracking. For example, the phase offset associated with the kth time domain sample sequence may be It can be expressed as the GI value in the kth time domain sequence (p k,i ), the GI value in the preliminary guard interval (e.g., between time t0 and t1) The number of GI samples in each guard interval (N GI ) and the length of the channel impulse response (N CIR ) function:

[0137]

[0138] Aspects of the present disclosure further recognize that the length of the available correlation window (L corr ) indicates the degree of noise suppression available. For example, the length L corr represents the number of GI samples that are not affected by inter-symbol interference (ISI) from the previous time-domain sample sequence:

[0139] L corr =N GI -N CIR +1

[0140] Fig.16 1600 according to some implementations. In some aspects, the SC-FDM modulation system 1600 may be configured to modulate the PPDU 1601 onto the TX signal 1608. More specifically, the SC-FDM modulation system 1600 may be configured to generate a sequence of data samples followed by a guard interval (such as Fig.15 In some implementations, the SC-FDM modulation system 1600 may be Figure 7 An example of an SC-FDM modulator 720. Figure 7 , PPDU 1601 may be an example of TD symbol 702 , and TX signal 1608 may be an example of TX signal 703 .

[0141] SC-FDM modulation system 1600 includes a Q-point DFT 1610, a tone mapper 1620, an N-point IFFT 1630, a GI adder 1640, and a DAC 1650. Q-point DFT 1610 converts PPDU 1601 from the time domain to the frequency domain. In some aspects, Q-point DFT 1610 may convert a number (M) of data symbols (such as Figure 7 TD symbols 702) are converted into a number (Q) of frequency domain (FD) samples 1603. For example, Q may represent the size of the RU or M-RU to which the FD samples 1603 are mapped. In some implementations, Q may be an integer value equal to the size of any RU or M-RU defined by an existing version of the IEEE 802.11 standard. In some other implementations, Q may be an integer value that is only divisible by 2, 3, or 5 (such as referring to Figure 8 In some implementations, a plurality of null symbols 1602 (having a value equal to zero) may also be provided as input to the Q-point DFT 1610 (where M+K=Q). Fig.15 , the null symbol 1602 may be used as a placeholder for one or more GI samples at the end of the IFFT window.

[0142] The tone mapper 1620 maps the FD samples 1603 to a number (N) of subcarriers to produce modulated subcarriers 1604. The N subcarriers may represent an OFDM symbol in the frequency domain. In other words, the N subcarriers may span a bandwidth associated with a wireless channel over which the TX signal 1608 is transmitted. In some aspects, N may be greater than Q. Thus, the tone mapper 1620 may map the FD samples 1603 to a subset of the N subcarriers representing a Q-subcarrier RU or M-RU that spans a portion of the channel bandwidth. In some aspects, the tone mapper 1620 may map null values ​​to one or more DC subcarriers (of the N subcarriers) associated with the channel bandwidth (such as with reference to FIG. 1 ). Fig. 9B In some implementations, the tone mapper 1620 may map null values ​​to one or more of the N subcarriers such that the output of the N-point IFFT 1630 includes a series of null samples 1606. Fig.15 , the null samples 1606 may be used as placeholders for one or more GI samples at the end of the IFFT window. For example, at least some of the null samples 1606 may coincide with the null symbols 1602.

[0143] The N-point IFFT 1630 transforms the modulated subcarrier 1604 from the frequency domain to the time domain as a series of time domain (TD) samples 1605 followed by a series of null samples 1606. Referring to e.g. Fig.15, a series of TD samples 1605 may be an example of any data sample sequence within a given IFFT window (such as data samples distributed between time t1 and t2 or data samples distributed between time t3 and t4). GI adder 1640 modulates the GI value (or pilot value) onto the null sample 1606 to generate a series of GI samples 1607. Referring to, for example Fig.15 , a series of GI samples 1607 may be an example of any GI sample sequence within a given IFFT window (such as GI samples distributed between time t2 and t3 or GI samples distributed between time t4 and t5). DAC 1650 converts a series of TD samples 1605 and a series of GI samples 1607 into a TX signal 1608.

[0144] In some aspects, at least a portion of the PHY preamble of the PPDU 1601 may be mapped directly to the N subcarriers in the frequency domain. For example, the PHY preamble may be directly input to the tone mapper 1620 (bypassing the Q-point DFT 1610), which maps the PHY preamble to the same RU or M-RU as the data portion of the PPDU 1601. In some aspects, an existing LTF sequence may be mapped to one or more LTFs in the PHY preamble of the PPDU 1601. In some implementations, the LTFs may be repeated to compensate for losses in channel estimation due to distortion of the TX signal 1608 (such as with reference to FIG. 1 ). Figure 8 In some other implementations, the LTF symbols may be modified to reduce the PAPR associated with the PPDU 1601 (such as with reference to Figure 8 In some other aspects, the new SC-LTF sequence may be mapped to one or more LFTs in the PHY preamble of the PPDU 1601. In some implementations, the SC-LTF sequence may be modulated according to a higher order modulation scheme (higher than BPSK) to reduce the PAPR of the PPDU 801 in the time domain. In some other implementations, the SC-LTF sequence may be constructed based on a Zadoff-Chu sequence (such as with reference to Figure 8 described).

[0145] Fig.17 A flow chart illustrating an example process 1700 for wireless communication supporting SC-FDM for a WLAN is shown. In some implementations, the process 1700 may be performed by an AP (such as those described above with reference to Figure 1 and 5A The process 1700 may be performed by a wireless communication device operating as a STA (such as any of the APs 102 or 502 described above) or operating within an AP. In some other implementations, the process 1700 may be performed by a wireless communication device operating as a STA (such as any of the APs 102 or 502 described above). Figure 1 and5B The invention may be performed by any one of the STA104 or 504 described herein) operating or by a wireless communication device operating within the STA.

[0146] In some implementations, process 1700 begins at block 1702 with modulating a PPDU into a plurality of symbols, the PPDU comprising a PHY preamble followed by a data portion, wherein the PHY preamble comprises a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU. At block 1704, process 1700 continues with transforming a number (Q) of symbols including one or more first symbols of the plurality of symbols representing the PPDU into Q frequency domain samples based on a DFT. At block 1706, process 1700 continues with mapping the Q frequency domain samples to a number (N) of subcarriers, wherein N>Q. At block 1708, process 1700 continues with transforming the N subcarriers into N time domain samples based on an IFFT. At block 1710, process 1700 continues with transmitting the N time domain samples over a wireless channel.

[0147] In some aspects, process 1700 may also include: mapping one or more null values ​​to one or more subcarriers of N subcarriers, respectively, wherein each of the one or more subcarriers represents a DC subcarrier associated with a bandwidth of a wireless channel. In some aspects, the N subcarriers may be subdivided into a number (n) of segments, each segment being associated with a corresponding index (i), wherein 1≤i≤n. In such aspects, process 1700 may also include: applying a series of first phase rotations to subcarriers in each segment of the n segments associated with an even index i; and applying a series of second phase rotations to subcarriers in each segment of the n segments associated with an odd index i, wherein the series of second phase rotations is different from the series of first phase rotations.

[0148] In some aspects, Q may only be divisible by 2, 3, or 5. In some aspects, the Q symbols may also include one or more pilot symbols associated with a phase tracking operation. In some implementations, the one or more pilot symbols may be interspersed between the one or more first symbols. In some other implementations, the one or more pilot symbols may be placed continuously in the time domain following the one or more first symbols. In some implementations, process 1700 may also include: appending a cyclic prefix including the one or more pilot symbols to the front of the N time domain samples.

[0149] In some other aspects, the Q symbols may further include one or more null symbols placed consecutively in the time domain following the one or more first symbols, wherein each of the one or more null symbols has a value equal to zero that maps to a corresponding null sample in the N time domain samples. In such aspects, process 1700 may further include: sending a sequence of GI values ​​immediately preceding the N time domain samples; and modulating the sequence of GI values ​​on one or more null samples in the N time domain samples.

[0150] In some aspects, process 1700 may also include: directly mapping one or more second symbols of the plurality of symbols to the N subcarriers, wherein the one or more second symbols represent at least a portion of the PHY preamble. In some implementations, a portion of the PHY preamble may include an LTF. In some implementations, the LTF may be modulated according to a modulation scheme having a higher modulation order than BPSK. In some other implementations, the LTF may include a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u), and a sequence length (N), wherein:

[0151]

[0152] In some implementations, N may be a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped. In some other implementations, N may be a prime number associated with a bandwidth of a wireless channel.

[0153] Fig.18 A flow chart illustrating an example process 1800 for wireless communication supporting SC-FDM for a WLAN is shown. In some implementations, the process 1800 may be performed by an AP (such as those described above with reference to Figure 1 and 5A The process 1800 may be performed by a wireless communication device operating as a STA (such as any of the APs 102 or 502 described above) or operating within an AP. In some other implementations, the process 1800 may be performed by a wireless communication device operating as a STA (such as any of the APs 102 or 502 described above). Figure 1 and 5B The invention may be performed by any one of the STA104 or 504 described herein) operating or by a wireless communication device operating within the STA.

[0154] In some implementations, process 1800 begins in block 1802 with receiving a time-varying signal carrying a PPDU on a wireless channel, the PPDU including a PHY preamble followed by a data portion, the PHY preamble including a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU. In block 1804, process 1800 continues with transforming a number (N) of first time-domain samples of the time-varying signal into N first modulated subcarriers based on an FFT. In block 1806, process 1800 continues with demapping the N first modulated subcarriers into a number (Q) of frequency-domain samples, where N>Q. In block 1808, process 1800 continues with transforming the Q frequency-domain samples into Q symbols based on an IDFT. In block 1810, process 1800 continues with demodulating the Q symbols. At block 1812, process 1800 continues by recovering at least a portion of the PPDU from the Q demodulated symbols.

[0155] In some aspects, Q may be divisible only by 2, 3, or 5. In some aspects, the Q symbols may include one or more pilot symbols associated with a phase tracking operation. In some implementations, the one or more pilot symbols may be interspersed between one or more data symbols in the Q symbols representing a portion of the PPDU. In some other implementations, the one or more pilot symbols may be placed consecutively in the time domain following one or more data symbols in the Q symbols representing a portion of the PPDU. In some implementations, the received time-varying signal may include a cyclic prefix preceding the N time domain samples, wherein the cyclic prefix includes the one or more pilot symbols.

[0156] In some other aspects, the received time-varying signal includes a sequence of GI values ​​immediately preceding the N time-domain samples. In such aspects, process 1800 may also include recovering the sequence of GI values ​​from one or more first symbols of the Q symbols, the one or more first symbols being consecutively placed in the time domain following one or more data symbols of the Q symbols representing a portion of the PPDU.

[0157] In some aspects, process 1800 may also include: transforming the N second time domain samples of the received time-varying signal into N second modulated subcarriers based on an FFT; demodulating the N second modulated subcarriers; and recovering at least a portion of a PHY preamble from the N demodulated subcarriers. In some aspects, the portion of the PHY preamble recovered from the N demodulated subcarriers may include an LTF. In some implementations, the N second modulated subcarriers may be demodulated according to a modulation scheme having a higher modulation order than BPSK. In some other implementations, the LTF may include a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u), and a sequence length (N), where:

[0158]

[0159] In some implementations, N may be a prime number associated with the RU or M-RU to which the Q frequency-domain samples are mapped. In some other implementations, N may be a prime number associated with the bandwidth of the wireless channel.

[0160] Fig.19 A block diagram of an example wireless communication device 1900 is shown according to some implementations. In some implementations, the wireless communication device 1900 is configured to perform a reference Fig.17 The wireless communication device 1900 may be the one described above with reference to Figure 4 An example implementation of the wireless communication device 400 is described. For example, the wireless communication device 1900 may be a chip, SoC, chipset, package, or device including at least one processor and at least one modem (e.g., a Wi-Fi (IEEE 802.11) modem or a cellular modem).

[0161] The wireless communication device 1900 includes a receiving component 1910, a communication manager 1920, and a transmitting component 1930. The communication manager 1920 also includes a constellation mapping component 1922 and a frequency domain conversion component 1924, a subcarrier mapping component 1926, and a time domain conversion component 1928. Portions of one or more of the components 1922, 1924, 1926, and 1928 may be implemented at least in part in hardware or firmware. In some implementations, at least some of the components 1922, 1924, 1926, and 1928 are implemented at least in part as software stored in a memory, such as the memory 408. For example, portions of one or more of the components 1922, 1924, 1926, and 1928 may be implemented as non-transitory instructions (or "code") that can be executed by a processor, such as the processor 406, to perform the functions or operations of the corresponding components.

[0162] The receiving component 1910 is configured to receive an RX signal from one or more other wireless communication devices on a wireless channel. The communication manager 1920 is configured to control or manage communication with one or more other wireless communication devices. In some implementations, the constellation mapping component 1922 can modulate the PPDU into multiple symbols, the PPDU including a PHY preamble followed by a data portion, wherein the PHY preamble includes a short training field (STF), a long training field (LTF) and one or more signal (SIG) fields carrying information for interpreting the PPDU; the frequency domain conversion component 1924 can transform a number (Q) of symbols including one or more first symbols in a plurality of symbols representing the PPDU into Q frequency domain samples based on DFT; the subcarrier mapping component 1926 can map the Q frequency domain samples to a number (N) of subcarriers, wherein N>Q; and the time domain conversion component 1928 can transform the N subcarriers into N time domain samples based on IFFT. The transmitting component 1930 is configured to send a TX signal to one or more other wireless communication devices on a wireless channel. In some implementations, transmitting component 1930 can transmit the N time domain samples over a wireless channel.

[0163] Fig. 20 A block diagram of an example wireless communication device 2000 according to some implementations is shown. In some implementations, the wireless communication device 2000 is configured to perform a reference Fig.18 The wireless communication device 2000 may be the one described above with reference to Figure 4 An example implementation of the wireless communication device 400 is described. For example, the wireless communication device 2000 may be a chip, SoC, chipset, package, or device including at least one processor and at least one modem (eg, a Wi-Fi (IEEE 802.11) modem or a cellular modem).

[0164] The wireless communication device 2000 includes a receiving component 2010, a communication manager 2020, and a transmitting component 2030. The communication manager 2020 also includes a frequency domain conversion component 2022, a subcarrier demapping component 2024, a time domain conversion component 2026, and a constellation demapping component 2028. Portions of one or more of the components 2022, 2024, 2026, and 2028 may be implemented at least in part in hardware or firmware. In some implementations, at least some of the components 2022, 2024, 2026, and 2028 are at least in part implemented as software stored in a memory, such as the memory 408. For example, portions of one or more of the components 2022, 2024, 2026, and 2028 may be implemented as non-transitory instructions (or "code") that can be executed by a processor, such as the processor 406, to perform the functions or operations of the corresponding components.

[0165] The receiving component 2010 is configured to receive an RX signal from one or more other wireless communication devices on a wireless channel. In some implementations, the receiving component 2010 can receive a time-varying signal carrying a PPDU on a wireless channel, the PPDU including a PHY preamble followed by a data portion, wherein the PHY preamble includes a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU. The communication manager 2020 is configured to control or manage communications with one or more other wireless communication devices. In some implementations, the frequency domain conversion component 2022 can transform a number (N) of first time domain samples of the time-varying signal into N first modulated subcarriers based on FFT; the subcarrier demapping component 2024 can demap the N first modulated subcarriers into a number (Q) of frequency domain samples, where N>Q; the time domain conversion component 2026 can transform the Q frequency domain samples into Q symbols based on IDFT; and the constellation demapping component 2028 can demodulate the Q symbols and recover at least a portion of the PPDU from the Q demodulated symbols. The transmitting component 2030 is configured to transmit a TX signal to one or more other wireless communication devices on a wireless channel.

[0166] Implementation examples are described in the following numbered clauses:

[0167] 1. A method for wireless communication by a wireless communication device, comprising:

[0168] modulating a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU) into a plurality of symbols, the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU;

[0169] transforming a number (Q) of symbols including one or more first symbols of the plurality of symbols representing the PPDU into Q frequency domain samples based on a discrete Fourier transform (DFT);

[0170] Mapping the Q frequency domain samples to a number (N) of subcarriers, where N>Q;

[0171] transforming the N subcarriers into N time domain samples based on an inverse fast Fourier transform (IFFT); and

[0172] The N time domain samples are transmitted over a wireless channel.

[0173] 2. The method according to clause 1, further comprising:

[0174] One or more null values ​​are respectively mapped to one or more subcarriers of the N subcarriers, each of the one or more subcarriers representing a direct current (DC) subcarrier associated with a bandwidth of the wireless channel.

[0175] 3. A method according to any of clauses 1 or 2, wherein the N subcarriers are subdivided into a number (n) of segments, each segment being associated with a respective index (i), wherein 1≤i≤n, the method further comprising:

[0176] applying a series of first phase rotations to subcarriers in each of the n segments associated with an even index i; and

[0177] A series of second phase rotations are applied to subcarriers in each of the n segments associated with an odd index i, the series of second phase rotations being different from the series of first phase rotations.

[0178] 4. A method according to any of clauses 1-3, wherein the Q symbols also include one or more pilot symbols associated with a phase tracking operation.

[0179] 5. A method according to any of clauses 1-4, wherein the one or more pilot symbols are interspersed between the one or more first symbols.

[0180] 6. A method according to any of clauses 1-4, wherein the one or more pilot symbols are placed consecutively in the time domain following the one or more first symbols.

[0181] 7. The method according to any one of clauses 1 to 4 or 6, further comprising:

[0182] A cyclic prefix including the one or more pilot symbols is appended in front of the N time domain samples.

[0183] 8. A method as set out in any of clauses 1-3, wherein the Q symbols further comprise one or more null symbols placed consecutively in the time domain following the one or more first symbols, each of the one or more null symbols having a value equal to zero, the value being mapped to a corresponding null sample of the N time domain samples, the method further comprising:

[0184] sending a sequence of guard interval (GI) values ​​immediately preceding the N time domain samples; and

[0185] The GI value sequence is modulated onto one or more null samples in the N time domain samples.

[0186] 9. A method according to any one of clauses 1 to 8, further comprising:

[0187] One or more second symbols of the plurality of symbols are directly mapped to the N subcarriers, the one or more second symbols representing at least a portion of the PHY preamble.

[0188] 10. A method as described in any of clauses 1-9, wherein the portion of the PHY preamble comprises the LTF.

[0189] 11. A method according to any of clauses 1-10, wherein the LTF is modulated according to a modulation scheme having a higher modulation order than Binary Phase Shift Keying (BPSK).

[0190] 12. A method according to any of clauses 1 to 10, wherein the LTF comprises a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u) and a sequence length (N), wherein:

[0191]

[0192] 13. A method according to any of clauses 1-10 or 12, wherein N is a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped.

[0193] 14. A method according to any of clauses 1-10 or 12, wherein N is a prime number associated with a bandwidth of the wireless channel.

[0194] 15. A method according to any one of clauses 1 to 14, wherein Q is divisible only by 2, 3 or 5.

[0195] 16. A wireless communication device, comprising:

[0196] at least one memory; and

[0197] At least one processor communicatively coupled to the at least one memory, the at least one processor configured to cause the wireless communication device to perform a method according to any one or more of clauses 1-15.

[0198] 17. A method for wireless communication by a wireless communication device, comprising:

[0199] receiving, on a wireless channel, a time-varying signal carrying a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU), the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU;

[0200] transforming a number (N) of first time-domain samples of the time-varying signal into N first modulated subcarriers based on a Fast Fourier Transform (FFT);

[0201] Demapping the N first modulated subcarriers to a number (Q) of frequency domain samples, where N>Q;

[0202] Transforming the Q frequency domain samples into Q symbols based on an inverse discrete Fourier transform (IDFT);

[0203] Demodulating the Q symbols; and

[0204] At least a portion of the PPDU is recovered from the Q demodulated symbols.

[0205] 18. A method as described in clause 17, wherein the Q symbols include one or more pilot symbols associated with a phase tracking operation.

[0206] 19. A method as described in any of clauses 17 or 18, wherein the one or more pilot symbols are interspersed between one or more data symbols in the Q symbols representing the portion of the PPDU.

[0207] 20. A method as described in any of clauses 17 or 18, wherein the one or more pilot symbols are placed consecutively in the time domain following one or more data symbols of the Q symbols representing the portion of the PPDU.

[0208] 21. A method according to any of clauses 17, 18 or 20, wherein the received time-varying signal comprises a cyclic prefix preceding the N time-domain samples, the cyclic prefix comprising the one or more pilot symbols.

[0209] 22. A method as described in clause 17, wherein the received time-varying signal comprises a sequence of guard interval (GI) values ​​immediately preceding the N time-domain samples, the method further comprising:

[0210] The GI value sequence is recovered from one or more first symbols among the Q symbols, the one or more first symbols being consecutively placed in the time domain following one or more data symbols among the Q symbols representing the portion of the PPDU.

[0211] 23. A method according to any one of clauses 17 to 22, further comprising:

[0212] transforming N second time domain samples of the received time-varying signal into N second modulated subcarriers based on the FFT;

[0213] Demodulating the N second modulated subcarriers; and

[0214] At least a portion of the PHY preamble is recovered from the N demodulated subcarriers.

[0215] 24. A method as described in any of clauses 17-23, wherein the portion of the PHY preamble recovered from the N demodulated subcarriers comprises the LTF.

[0216] 25. A method according to any of clauses 17-24, wherein the N second modulated sub-carriers are demodulated according to a modulation scheme having a higher modulation order than Binary Phase Shift Keying (BPSK).

[0217] 26. A method according to any of clauses 17 to 24, wherein the LTF comprises a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u) and a sequence length (N), wherein:

[0218]

[0219] 27. A method according to any of clauses 17-24 or 26, wherein N is a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped.

[0220] 28. A method according to any of clauses 17-24 or 26, wherein N is a prime number associated with a bandwidth of the wireless channel.

[0221] 29. A method according to any of clauses 17-28, wherein Q is divisible only by 2, 3 or 5.

[0222] 30. A wireless communication device, comprising:

[0223] at least one memory; and

[0224] At least one processor communicatively coupled to the at least one memory, the at least one processor being configured to cause the wireless communication device to perform a method according to any one or more of clauses 17-29.

[0225] As used herein, a phrase referring to "at least one of" or "one or more of" a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to cover the possibilities of: only a, only b, only c, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a, b, and c. As used herein, "based on" is intended to be interpreted in an inclusive sense, unless otherwise expressly indicated. For example, "based on" may be used interchangeably with "based at least in part on," unless otherwise expressly indicated. Specifically, unless the phrase refers to "based only on 'a'" or an equivalent in context, whether "based on 'a'" or "based at least in part on 'a'" may be based only on "a" or on a combination of "a" and one or more other factors, conditions, or information.

[0226] The various illustrative components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described in conjunction with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or a combination of hardware, firmware, or software, including the structures disclosed in this specification and their structural equivalents. The interchangeability of hardware, firmware, and software has been generally described around functionality and shown in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0227] Various modifications to the implementations described in this disclosure may be apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Therefore, the claims are not intended to be limited to the implementations shown herein, but are to be given the broadest scope consistent with the disclosure, the principles and novel features disclosed herein.

[0228] In addition, various features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable subcombination. Furthermore, while features may be described above as acting in a particular combination, and even initially claimed as such, in some cases, one or more features from a claimed combination may be removed from the combination, and a claimed combination may be directed to a subcombination or variation of a subcombination.

[0229] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be understood as requiring to perform in the specific order shown or in the order of sequence, or requiring to perform all the operations shown to achieve the desired result. In addition, the accompanying drawings can schematically depict one or more example processes in the form of a flow chart or a schematic flow diagram. However, other operations that are not depicted can be incorporated into the example processes schematically shown. For example, one or more additional operations can be performed before, after, simultaneously or between any operation in the operations shown. In some cases, multitasking and parallel processing may be advantageous. In addition, the segmentation of each system component in the implementation described above should not be understood as requiring such segmentation in all implementations, and it should be understood that the described program components and systems can usually be integrated together in a single software product, or be encapsulated in multiple software products.

Claims

1. A method for performing wireless communication by a wireless communication device, comprising: modulating a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU) into a plurality of symbols, the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU; transforming a number (Q) of symbols including one or more first symbols of the plurality of symbols representing the PPDU into Q frequency domain samples based on a discrete Fourier transform (DFT); Mapping the Q frequency domain samples to a number (N) of subcarriers, where N>Q; transforming the N subcarriers into N time domain samples based on an inverse fast Fourier transform (IFFT); and The N time domain samples are transmitted over a wireless channel.

2. The method according to claim 1, further comprising: One or more null values ​​are respectively mapped to one or more subcarriers of the N subcarriers, each of the one or more subcarriers representing a direct current (DC) subcarrier associated with a bandwidth of the wireless channel.

3. The method according to claim 1, wherein: The N subcarriers are subdivided into a number (n) of segments, each segment being associated with a corresponding index (i), wherein 1≤i≤n, the method further comprising: applying a series of first phase rotations to subcarriers in each of the n segments associated with an even index i; and A series of second phase rotations are applied to subcarriers in each of the n segments associated with an odd index i, the series of second phase rotations being different from the series of first phase rotations.

4. The method according to claim 1, wherein: The Q symbols also include one or more pilot symbols associated with a phase tracking operation.

5. The method according to claim 4, wherein: The one or more pilot symbols are interspersed between the one or more first symbols.

6. The method according to claim 4, wherein: The one or more pilot symbols are placed continuously in the time domain following the one or more first symbols.

7. The method according to claim 6, further comprising: A cyclic prefix including the one or more pilot symbols is appended in front of the N time domain samples.

8. The method according to claim 1, wherein: The Q symbols further include one or more null symbols placed consecutively in the time domain following the one or more first symbols, each of the one or more null symbols having a value equal to zero, the value being mapped to a corresponding null sample in the N time domain samples, the method further comprising: sending a sequence of guard interval (GI) values ​​immediately preceding the N time domain samples; and The GI value sequence is modulated onto one or more null samples in the N time domain samples.

9. The method according to claim 1, further comprising: One or more second symbols of the plurality of symbols are directly mapped to the N subcarriers, the one or more second symbols representing at least a portion of the PHY preamble.

10. The method according to claim 9, wherein: The portion of the PHY preamble includes the LTF.

11. The method according to claim 10, wherein: The LTF is modulated according to a modulation scheme having a higher modulation order than binary phase shift keying (BPSK).

12. The method according to claim 10, wherein: The LTF comprises a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u) and a sequence length (N), where:

13. The method according to claim 12, wherein: N is a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped.

14. The method according to claim 12, wherein: N is a prime number associated with the bandwidth of the wireless channel.

15. The method according to claim 1, wherein: Q is only divisible by 2, 3, or 5.

16. A wireless communication device, comprising: at least one memory; as well as at least one processor communicatively coupled to the at least one memory, the at least one processor configured to cause the wireless communication device to: modulating a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU) into a plurality of symbols, the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU; transforming a number (Q) of symbols including one or more of the plurality of symbols representing the PPDU into Q frequency domain samples based on a discrete Fourier transform (DFT); Mapping the Q frequency domain samples to a number (N) of subcarriers, where N>Q; transforming the N subcarriers into N time domain samples based on an inverse fast Fourier transform (IFFT); and The N time domain samples are transmitted over a wireless channel.

17. A method of wireless communication performed by a wireless communication device, comprising: receiving, on a wireless channel, a time-varying signal carrying a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU), the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU; transforming a number (N) of first time-domain samples of the time-varying signal into N first modulated subcarriers based on a Fast Fourier Transform (FFT); Demapping the N first modulated subcarriers to a number (Q) of frequency domain samples, where N>Q; Transforming the Q frequency domain samples into Q symbols based on an inverse discrete Fourier transform (IDFT); Demodulating the Q symbols; and At least a portion of the PPDU is recovered from the Q demodulated symbols.

18. The method according to claim 17, wherein: The Q symbols include one or more pilot symbols associated with a phase tracking operation.

19. The method according to claim 18, wherein: The one or more pilot symbols are interspersed between one or more data symbols among the Q symbols representing the portion of the PPDU.

20. The method according to claim 18, wherein: The one or more pilot symbols are placed consecutively in the time domain following one or more data symbols among the Q symbols representing the portion of the PPDU.

21. The method according to claim 20, wherein: The received time-varying signal includes a cyclic prefix preceding the N time-domain samples, the cyclic prefix including the one or more pilot symbols.

22. The method according to claim 17, wherein: The received time-varying signal includes a sequence of guard interval (GI) values ​​immediately preceding the N time domain samples, the method further comprising: The GI value sequence is recovered from one or more first symbols among the Q symbols, the one or more first symbols being consecutively placed in the time domain following one or more data symbols among the Q symbols representing the portion of the PPDU.

23. The method of claim 17, further comprising: transforming N second time domain samples of the received time-varying signal into N second modulated subcarriers based on the FFT; Demodulating the N second modulated subcarriers; as well as At least a portion of the PHY preamble is recovered from the N demodulated subcarriers.

24. The method according to claim 23, wherein: The portion of the PHY preamble recovered from the N demodulated subcarriers includes the LTF.

25. The method according to claim 24, wherein: The N second modulated subcarriers are demodulated according to a modulation scheme having a higher modulation order than binary phase shift keying (BPSK).

26. The method according to claim 24, wherein: The LTF comprises a sequence of values ​​(x) associated with a Zadoff-Chu sequence having a sequence index (m), a root index (u) and a sequence length (N), where:

27. The method according to claim 26, wherein: N is a prime number associated with a resource unit (RU) or a multi-RU (M-RU) to which the Q frequency-domain samples are mapped.

28. The method according to claim 26, wherein: N is a prime number associated with the bandwidth of the wireless channel.

29. The method according to claim 28, wherein: Q is only divisible by 2, 3, or 5.

30. A wireless communication device, comprising: at least one memory; as well as at least one processor communicatively coupled to the at least one memory, the at least one processor configured to cause the wireless communication device to: receiving, on a wireless channel, a time-varying signal carrying a physical layer (PHY) convergence protocol (PLCP) protocol data unit (PPDU), the PPDU comprising a PHY preamble followed by a data portion, the PHY preamble comprising a short training field (STF), a long training field (LTF), and one or more signal (SIG) fields carrying information for interpreting the PPDU; transforming a number (N) of first time-domain samples of the time-varying signal into N first modulated subcarriers based on a Fast Fourier Transform (FFT); Demapping the N first modulated subcarriers to a number (Q) of frequency domain samples, where N>Q; Transforming the Q frequency domain samples into Q symbols based on an inverse discrete Fourier transform (IDFT); Demodulating the Q symbols; and At least a portion of the PPDU is recovered from the Q demodulated symbols.

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