BR112017004345B1 - TONE PLAN FOR LTF COMPRESSION AND TRANSMISSION IN WIRELESS COMMUNICATION SYSTEMS - Google Patents

Abstract

TONE PLAN FOR LTF COMPRESSION AND TRANSMISSION IN WIRELESS COMMUNICATION SYSTEMS. A method, an apparatus and a computer program product for wireless communication are provided. In one aspect, an apparatus is configured to transmit user data in a first symbol of a first type of symbol. The first symbol type has a first symbol duration, a first frequency bandwidth, and a tone foreground. The foreground tone includes a first valid start tone index, a first valid end tone index, and a first set of DC tones. The equipment is further configured to transmit an LTF on a second symbol of a second symbol type. The second symbol type has a second symbol duration, a second frequency bandwidth, and a tone background. The tone background includes a valid second start tone index, a valid second end tone index, and a second set of DC tones.

Description

Cross-references to related filing requests

[0001] This application claims the benefit of Provisional Patent Application Serial No. 62/046,086, entitled “Tone Plan for LTF Compression” and filed on September 4, 2014, Provisional Application Serial No. US 62/054,932, entitled “Tone Plan for LTF Compression” and filed on September 24, 2014, Provisional Application Serial No. US 62/064,935, entitled “Tone Plan for LTF Compression” and filed on October 16, 2014, Interim Application Serial No. US 62/067,260, entitled “Tone Plan for LTF Compression” and filed on October 22, 2014, and Patent Application No. US 14/843,538 entitled “TONE PLAN FOR LTF COMPRESSION” and filed September 2, 2015, all of which are expressly incorporated herein in full by reference.

BACKGROUND Field

[0002] The present disclosure relates generally to communications systems and more particularly to tone planes for long field compression training.

Background

[0003] In many telecommunication systems, communications networks are used to exchange messages between several interacting spatially separated devices. Networks can be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personnel area. Such networks could be referred to, respectively, as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), wireless local area network (WLAN), or personal area network (PAN). ). Networks also differ according to the switching/routing technique used to interconnect the various network nodes and devices (eg, circuit switching vs. packet switching), the type of physical media employed for transmission (eg, wired vs. wireless), and the set of communication protocols used (eg, Internet protocol suite, Synchronous Optical Networking (SONET), Ethernet, etc.).

[0004] Wireless networks are often preferred when the network elements are mobile and therefore have dynamic connectivity needs, or if the network architecture is formed in ad hoc rather than fixed topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infrared, optical, etc. frequency ranges. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed wired networks.

SUMMARY

[0005] The systems, methods, computer-readable media, and devices of the invention each have various aspects, no single one of which is solely responsible for the desirable attributes of the invention. Without limiting the scope of this invention as expressed by the following claims, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled “Detailed Description”, one will understand how the features of this invention provide advantages for devices on a wireless network.

[0006] One aspect of this disclosure provides a wireless device (eg, an access point or a station) for wireless communication. The wireless device may be configured to transmit user data in a first symbol of a first type of symbol. The first symbol type may have a first symbol duration, a first frequency bandwidth, and a tone foreground. The foreground tone can have a first valid start tone index, a first valid end tone index, and a first set of direct current (DC) tones. The wireless device can be configured to transmit a long training field in a second symbol of a second symbol type. The second type of symbol can have a second symbol duration, a second frequency bandwidth and a tone background. The background tone can have a valid second start tone index, a valid second end tone index, and a second set of DC tones.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 shows an exemplary wireless communication system in which aspects of the present disclosure can be employed.

[0008] FIG. 2 is a diagram of a wireless network and a tone plan.

[0009] FIGs. 3A-C are exemplary tone planes/indices diagrams for LTF compression.

[0010] FIGs. 4A-B are exemplary planes/tone indices diagrams for LTF compression.

[0011] FIG. 5 is a functional block diagram of a wireless device that may be employed within the wireless communication system of FIG. 1 and can use a modified tone plane.

[0012] FIG. 6 is a flowchart of an exemplary method of wireless communication using a modified tone plane.

[0013] FIG. 7 is a functional block diagram of an exemplary wireless communication device using a modified tone plane.

DETAILED DESCRIPTION

[0014] Various aspects of the innovative systems, equipment, computer program products, and methods are described more fully below with reference to the accompanying drawings. This disclosure may, however, be realized in many different ways and is not to be construed as limited to any specific structure or function set forth throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the description to those skilled in the art. Based on the teachings herein, a person skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the innovative systems, equipment, computer program products, and methods disclosed herein, whether implemented independently of, or combined with, any other aspect. of the invention. For example, an apparatus can be implemented or a method can be practiced using any number of aspects presented here. Furthermore, the scope of the invention is intended to cover such an apparatus or method which is practiced using another structure, functionality, or structure and functionality in addition to or other than the various aspects of the invention presented herein. It is to be understood that any aspect disclosed herein may be incorporated by one or more elements of a claim.

[0015] Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. While certain benefits and advantages of the preferred features are mentioned, the scope of the disclosure is not intended to be limited to certain benefits, uses or purposes. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting it, the scope of the disclosure being defined by the appended claims and equivalents thereto.

[0016] Popular wireless networking technologies can include various types of WLANs. A WLAN can be used to interconnect nearby devices, employing widely used network protocols. The various aspects described here can apply to any communication standard, such as a wireless protocol.

[0017] In some aspects, wireless signals may be transmitted in accordance with an 802.11 protocol using orthogonal frequency division multiplexing (OFDM), direct sequence spread spectrum communications (DSSS), a combination of OFDM and DSSS communications , or other schemes. Implementations of the 802.11 protocol can be used for sensors, meters and smart grid networks. Advantageously, aspects of certain devices implementing the 802.11 protocol may consume less power than devices implementing other wireless protocols, and/or may be used to transmit radio signals over a relatively long distance, for example about a kilometer or more.

[0018] In some implementations, a WLAN includes multiple devices that are the components that access the wireless network. For example, there can be two types of devices: access points (APs) and clients (also referred to as stations or “STAs”). In general, an AP can serve as a hub or base station for the WLAN and a STA serves as a WLAN user. For example, an STA can be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In one example, an STA connects to an AP over a WiFi (eg IEEE 802.11 protocol like) compliant wireless link to achieve general connectivity to the Internet or other wide area networks. In some implementations, a STA can also be used as an AP.

[0019] An access point may also comprise, be implemented as, or known as a Node B, Radio Network Controller (RNC), eNodeB, Base Station Controller (BSC), Base Transceiver Station (BTS), Station Base (BS), Transceiver Function (FT), Radio Router, Radio Transceiver, connection point, or some other terminology.

[0020] A station may also comprise, be implemented as, or known as an access terminal (AT), a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a user terminal , a user agent, a user device, a user equipment, or some other terminology. In some implementations, a station may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) telephone, a wireless local circuit (WLL) station, a personal digital assistant (PDA), a wireless capable laptop, or other suitable processing device connected to a wireless modem. Accordingly, one or more features described herein may be incorporated into a telephone (e.g., a cell phone or smartphone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device ( for example, a personal data assistant), an entertainment device (for example, a music or video device, or a satellite radio), a gaming device or system, a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium.

[0021] In one aspect, MIMO schemes may be used for wide-area WLAN connectivity (eg, Wi-Fi). MIMO exploits a radio wave characteristic called multi-path. In multipath, transmitted data can bounce objects (eg walls, doors, furniture), reaching the receiving antenna multiple times via different routes and at different times. A WLAN device employing MIMO will split a data stream into multiple parts, called spatial streams (or multi-streams), and transmit each spatial stream through separate antennas to corresponding antennas on a receiving WLAN device.

[0022] The term “associate”, or “association”, or any variant thereof shall be given the broadest possible meaning within the context of the present disclosure. By way of example, when a first piece of equipment is associated with a second piece of equipment, it must be understood that the two pieces of equipment can be directly associated or intermediate equipment can be present. For the sake of brevity, the process for establishing an association between two devices will be described using a handshake protocol that requires an "association request" by one of the devices followed by an "association response" by the other device. It will be understood by those skilled in the art that the greeting protocol may require other signaling, such as, for example, signaling to provide authentication.

[0023] Any reference to an element herein using a designation such as "first", "second" and so on generally does not limit the quantity or order of those elements. Rather, these designations are used here as a convenient method of distinguishing between two or more elements or occurrences of an element. Thus, a reference to the first and second elements does not mean that only two elements can be used, and that the first element must precede the second element. Also, a sentence referring to “at least one of a list of items refers to any combination of those items, including individual members. As an example, “at least one of”: A, B, or C” is intended to cover: A or B or C, or any combination thereof (e.g., A-B, A-C, B-C, and A-B-C).

[0024] As discussed above, some devices described here may implement the 802.11 standard, for example. Such devices, whether used as a STA or AP or other device, can be used for smart metering or in a network of smart grids. Such devices can provide sensor applications or be used in home automation. The devices may alternatively or additionally be used in a healthcare context, for example for personal healthcare. They can also be used for surveillance, to enable a range-extending Internet connection (for example, for use with hotspots), or to implement machine-to-machine communications.

[0025] FIG. 1 shows an exemplary wireless communication system 100 in which aspects of the present disclosure can be employed. Wireless communication system 100 may operate in accordance with a wireless standard, for example, the 802.11 standard. Wireless communication system 100 may include an AP 104, which communicates with STAs (e.g., STAs 112, 114, 116, and 118).

[0026] A variety of processes and methods can be used for transmissions in the wireless communication system 100 between the AP 104 and the STAs. For example, signals can be sent and received between AP 104 and STAs according to OFDM/OFDMA techniques. If this is the case, the wireless communication system 100 can be referred to as an OFDM/OFDMA system. Alternatively, signals can be sent and received between the AP 104 and the STAs in accordance with CDMA techniques. If this is the case, wireless communication system 100 may be referred to as a CDMA system.

[0027] The communication link that facilitates transmission from the AP 104 to one or more of the STAs may be referred to as a downlink (DL) 108, and a communication link that facilitates transmission from one or more of the STAs to the AP 104 may be referred to as an uplink (UL) 110. Alternatively, a downlink 108 may be referred to as a forward link or a forward channel, and an uplink 110 may be referred to as a reverse link or a reverse channel. In some aspects, DL communications may include indications of unicast or multicast traffic.

[0028] The AP 104 can suppress adjacent channel interference (AO) in some respects so that the AP 104 can receive UL communications on more than one channel simultaneously without causing significant analog-to-digital conversion (ADC) clipping noise. AP 104 can improve ACI suppression, for example, by having separate finite impulse response (FIR) filters for each channel or by having a longer ADC delay period with increased bit widths.

[0029] The AP 104 can act as a base station and provide wireless communication coverage in a basic service area (BSA) 102. A BSA (eg, the BSA 102) is the coverage area of an AP (eg, the AP 104). The AP 104, along with the STAs associated with the AP 104 and which use the AP 104 for communication may be referred to as a Basic Service Set (BSS). It should be noted that the wireless communication system 100 may not have a central AP (eg, AP 104), but instead may function as a peer-to-peer network between the STAs. Therefore, the functions of the AP 104 described herein may alternatively be performed by one or more of the STAs.

[0030] The AP 104 may transmit on one or more channels (e.g., multiple narrowband channels, each channel including a frequency bandwidth) a beacon signal (or simply a “beacon”), over a link communication devices, such as downlink 108, to other nodes (STAs) of the wireless communication system 100, which may assist other nodes (STAs) to synchronize their timing with the AP 104, or which may provide other information or functionality. These flags can be broadcast periodically. In one aspect, the period between successive transmissions may be referred to as a superframe. The transmission of a flag can be divided into several groups or intervals. In one aspect, the beacon may include, but is not limited to, information such as timestamp information to define a common clock, a peer network identifier, a device identifier, capability information, a superframe duration, transmit direction information, receive direction information, a neighbor list and/or an extended neighbor list, some of which are described in further detail below. Thus, a flag can include information that is both common (eg, shared) across multiple devices and specific to a given device.

[0031] In some aspects, a STA (eg, STA 114) may be required to associate with the AP 104 in order to send communications to and/or to receive communications from the AP 104. for association is included in a beacon transmission by the AP 104. To receive this beacon, the STA 114 may, for example, perform a wide coverage search over a coverage region. A search can also be performed by the STA 114 by scanning a coverage region of a lighthouse shape, for example. After receiving the information for association, the STA 114 may transmit a reference signal, such as a probe or association request, to the AP 104. In some aspects, the AP 104 may utilize the backhaul channel services, for example for example, to communicate with a larger network, such as the Internet or a public switched telephone network (PSTN).

[0032] In one aspect, the AP 104 may include one or more components to perform various functions. For example, the AP 104 may include a tone plane component 124 configured to transmit user data in a first symbol of a first symbol type to one or more STAs (e.g., STA 1 14). The first symbol type can have a first symbol duration, a first frequency bandwidth, and a tone foreground, and the tone foreground can include a valid first start tone index, a valid first end tone index and a first set of DC tones. Tone plane component 124 may be configured to transmit an LTF in a second symbol of a second symbol type. The second symbol type can have a second symbol duration, a second frequency bandwidth, and a tone background, and the tone background can include a valid second start tone index, a valid second end tone index and a second set of DC tones.

[0033] In another aspect, the STA 114 may include one or more components to perform various functions. For example, STA 114 may include a tone plane component 126 configured to transmit user data in a first symbol of a first symbol type to one or more APs (e.g., AP 104). The first symbol type may have a first symbol duration, a first frequency bandwidth, and a tone foreground. The foreground tone can have a valid first start tone index, a valid first end tone index, and a first set of DC tones. Tone plane component 126 may be configured to transmit an LTF in a second symbol of a second symbol type. The second symbol type has a second symbol duration, a second frequency bandwidth, and a tone background, and the tone background may include a valid start second tone index, a valid end second tone index, and a second set of DC tones.

[0034] In Wi-Fi networks, user data and data/information used for channel estimation, among other information, can be transmitted in frames that include multiple symbols (for example, OFDM symbols). User data can be transmitted in data symbols and information used for channel estimation can be transmitted in long training field (LTF) symbols. Each symbol can include a number of tones (or frequencies) on which information can be transmitted. A symbol also has symbol duration (for example, symbol duration of 1x, 2x, 4x, or another multiple of symbol duration 1x). Symbols with longer symbol duration (e.g., 4x symbol duration of 12.8 μs) can have more tones and longer time duration, and symbols with shorter symbol duration (e.g., 1x symbol duration of 3 .2 μs) may have fewer tones and shorter duration. For example, in a first symbol with a 4x symbol duration, the first symbol can be four times longer than a second symbol with a 1x symbol duration. The first symbol can have four times as many shades as the second symbol with a 1x symbol duration. The first symbol can have a quarter of the pitch spacing compared to a second symbol with 1x symbol duration. If a network transmits frames that use symbols with a symbol length of 4x in the LTF symbols and the data symbols, the overhead for the LTF symbols can be very large. This can be especially true for multi-streams and short to medium Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU) sizes. Longer symbol durations can also result in greater phase drift in uplink multi-user MIMO with a given residual carrier frequency offset (CFO). As such, there is a need to reduce LTF symbol overhead in wireless networks that use LTF symbols with longer symbol duration (eg, 4x symbol duration).

[0035] FIG. 2 is a diagram 200 of a wireless network (eg, a WiFi network) and tone plan. Diagram 200 illustrates a broadcast from AP 202 within a service area 214. STAs 206, 208, 210, 212 are within service area 214 of AP 202 (although only 4 STAs are shown in FIG. 2, more or less STAs can be within service area 214).

[0036] The AP 202 may transmit symbols (eg, data symbols or LTF symbols) 204 to one or more STAs (eg, STAs 206, 208, 210, 212) in one or more frames and vice versa. A frame 250 may include a preamble 260 and data symbols 268. The preamble 260 may be considered a header of the frame 250 with information identifying a modulation scheme, a transmission rate, and a time period for transmitting the frame 250. preamble 260 may include a signal field (SIG) 262, a short training field (STF) 264, and one or more long training field (LTF) symbols 266 (e.g., LTF1, LTF2, ..., LTFN) . Each symbol in the LTF Symbols 266 may include at least part of the LTF. Field SIG 262 can be used to transfer speed and length information. The STF 264 can be used to improve automatic gain control (AGC) in a multi-transmitter and multi-receiver system. For example, when a received signal is weak, the AGC algorithms in a receiving device can increase the gain stages in the receiving device to bring the received signal to an acceptable signal-to-noise ratio. LTF symbols 266 may be used to provide information necessary for a receiver (e.g., STA 206) to perform channel estimation. The number of LTF symbols can be equal to or greater than the number of spacetime streams from different STAs. For example, if there are 4 STAs, there could be 4 LTF symbols (ie LTF1, LTF2, LTF3, LTF4). Data symbols 268 may contain user data to be communicated between STA 206, for example, and AP 202.

[0037] In one aspect, the LTF symbols 266 (and data symbols 268) may have a tone plane that indicates which tones are guard tones, data tones, pilot tones and DC tones. For example, the 270 tone plane is an example of a tone plane for a 20 megahertz (MHz) symbol with 1x symbol duration, where the 20 MHz refers to the frequency bandwidth of the symbol. The 270 tone plane has 64 tones located within a tone range of -32 to 31 or [-32:31]. As shown in FIG. 2, however, not all tonal indices are represented. The unrepresented tone indices [-32:-29] and [29:31] are guard tones, which are tones that can have zero amplitude and are used to provide isolation or system separation from neighboring transmissions/symbols to reduce probability of shades of different symbols leaking together. A DC tone, located at tone index 0 in this example, can have zero amplitude or no energy and can be used for the AGC configuration. In one aspect, the DC tone may not carry information. In another aspect, the DC tone can be used to locate the radio frequency (RF) center frequency of a transmitting device. Although this example illustrates a DC tone at tone index 0, additional DC tones can be used (for example, 3 DC tones can be located at tone indexes -1, 0, and 1). In this example, the remaining tone indices [-28: -1] and [1: 28] contain usable (or useful) tones that can be used to transmit data (e.g. for channel estimation) and pilot signals (e.g. , phase drift correction). In tone plane 270, data 272 may be transmitted at tone indices -28, -27, -26, -10, -5, 5, 10, 26, 27, and 28, for example. A pilot signal 274 for phase drift correction, for example, may be transmitted at tone index -21. Additional pilot signals (as indicated by the vertical arrows in FIG. 2) can be transmitted at tone indices -7, 7, and 21. Because of the first valid tone, after the guard tones, on which data or pilot signals can be transmitted, is located at tone index -28, this tone index can be known as a valid start tone index. Likewise, tone index 28 may be known as a valid final tone index because tone index 28 is the last valid tone on which data or pilot signals can be transmitted before reaching tone indexes [29:31] , which are reserved for guard tones. In summary, the 270 tone plane has usable tones located within a tone index range of [-28:-1] and [1:28]. DC tones can be located at tone index 0, and non-DC tones can include guard tones and usable tones (which can include data tones for transmitting data and pilot tones for transmitting pilot signals) .

[0038] With reference again to FIG. 2, although LTF symbol 266 (e.g., LTF1) has a symbol duration of 1x as evidenced by tone plane 270, some wireless networks may use symbols with a symbol duration of 4x. Symbols with a symbol duration of 4x can have a total of 256 tones, of which 242 tones can be usable or valid tones (excluding guard tones and DC tones). For example, a symbol with a symbol duration of 4x can have usable tones within a tone index range of [-122:-2] and [2 : 122]. In one configuration, three DC tones can be located at tone indices [-1:1], and the guard tones can be located in tone indices [-128:-123] and [123:127]. However, when a wireless network uses symbols with a symbol duration of 4x for both LTF symbols (for example, 266 LTF symbols) and data symbols (for example, 268 data symbols), the overhead can be large. as previously discussed. Longer symbol length also increases phase drift.

[0039] To reduce the LTF symbol overhead in networks using symbols with a 4x symbol duration, two approaches can be followed separately. In the first approach, devices on the wireless network can continue to use LTF symbols with 4x symbol durations, but the tones within the LTF symbols can be grouped according to a group number (Ng) and shared between STAs. For example, if the group number is 2 (Ng = 2) and there are 2 STAs 206, 208, each STA can use all other tones. In this example, STA 206 can transmit on even tones and STA 208 can transmit on odd tones. When the AP 202 performs channel estimation for the STAs 206, 208 on the received LTF symbols 266 (e.g., LTF 1), the AP 202 may perform interpolation for the odd tones for the STA 206 and for the even tones for the STA 206. STA 208. Similarly, if the group number is 2 (Ng = 2) and there are 2 STAs 206, 208, 210, 212, each STA can transmit on every fourth tone in 266 LTF symbols. when Ng = 4, interpolation can be used by the receiver (eg AP 202) to reconstruct channel estimates of unsampled tones. In another aspect, when the grouping of tones (Ng) is greater than the number of STAs (or users or flows), for example, Ng = 4 and the number of STAs is 3, the power per tone in the tones being used will be augmented so that the total transmit power in the LTF symbol remains the same as in an LTF symbol in which all usable tones are being filled. The scale factor with respect to transmit power is a function of the number of streams or STAs. In yet another aspect, if Ng = 4 but there is only one stream or one user, i.e. equivalent to transmitting an LTF symbol with symbol duration 1x with Ng = 1 (without any unfilled tones). Likewise, if there are 2 users (or STAs), this is equivalent to transmitting an LTF symbol with 2x symbol duration and Ng = 2 with no wasted tones.

[0040] In the second approach, instead of using grouping of tones within the LTF symbol, the duration of the LTF symbol can be reduced. For example, instead of using 4x symbol durations for LTF 266 symbols, 1x or 2x symbol durations can be used to represent a symbol with 4x symbol duration. In one aspect, information in an LTF symbol with a 4x symbol duration can be compressed into an LTF symbol with a 1x symbol duration. However, two problems can arise when using reduced LTF symbol durations. The first issue concerns extrapolation challenges for channel estimation in edge tones. For example, a 20 MHz LTF symbol with a symbol duration of 1x has 56 usable tones out of 64 total tones. A 20 MHz LTF symbol with a 4x symbol duration has 242 usable tones out of 256 total tones. The 242 usable tones are effectively 4 times 60.5 tones. Indeed, without modifying the tone plane for a symbol with a symbol duration of 1x, the symbol would need 60.5 usable tones to represent a symbol with a symbol duration of 4x, assuming a compression factor or clustering number ) of 4. However, since a 20 MHz symbol with a symbol duration of 1x has only 56 usable tones, an average of 4.5 tones in the edge tones would be missing. Given the number of missing tones, channel interpolation cannot be used. Channel extrapolation can be used, but channel extrapolation can introduce more errors and degrade performance.

[0041] A second problem when using an LTF symbol with reduced symbol duration concerns the channel estimation around the DC tones in a symbol with a 4x symbol duration. For example, an 80 MHz symbol with a 4x symbol duration might have 3-7 DC tones. To map the channel estimates at tone indices -4 and +4 on a symbol with 4x symbol duration to a symbol with symbol duration 1x, one way is to fill these tones at tone indices -4 and +4 on indices tone -1 and +1 on symbol (eg LTF symbol) with symbol duration 1x. However, this would leave only one DC tone at index 0. In some cases, an 80 MHz symbol with a symbol duration of 1x has a tone plane that calls 3 DC tones with a notch filter that has a corresponding width of approximately 3 tones DC. As such, assuming that the notch filter only depends on the sampling rate, if the same notch filter is used (for example, the same notch filter with a width of 3 tones), the received LTF symbols with the symbol duration 1x can have tones located at indices -1 and +1 cut off by notch filtering, thus preventing the tones from being used for channel estimation. The following figures discuss a modified tone plan that reduces the LTF symbol overhead and overcomes the aforementioned issues.

[0042] FIGs. 3A-C are exemplary tone planes/indices diagrams 300, 330 and 360 for LTF compression. To solve the edge tone channel estimation problem, FIG. 3A illustrates an existing LTF symbol with a 4x symbol duration (row 1) that is used to derive a modified tone plane for LTF symbols with a 1x symbol duration (rows 2-3), a symmetric modified tone plane for symbols LTF with a symbol duration of 1x (rows 4-5) or a modified tone plane for LTF symbols with a symbol duration of 2x (rows 6-7). To address the second issue regarding channel estimation around DC tones, FIG. 3A offers two options. DC option 1 (for example, in row 2), assumes that an existing notch filter (for example, as used in current IEEE 802.11ac products) is used for the modified LTF symbol with 1x symbol duration. If this is the case, then the same number of DC tones can be reserved in the modified tone plane for the LTF symbol in row 2 as in the tone plane for the existing LTF symbol with 1x symbol duration in each signal bandwidth. corresponding frequency. In contrast, DC Option 2 (e.g. row 3) assumes that a new notch filter that is sharper and with a narrower notch can be used (compared to the notch filter used in 802.11ac products) so that only one DC tone is needed in the modified LTF symbol tone plane with 1x symbol duration. This is equally true for rows 4-7.

[0043] With reference to FIG. 3A, assuming a wireless network (e.g., the wireless network in FIGS. 1, 2) uses symbols with a symbol duration of 4x, row 1 of the diagram illustrates the usable tone rates for a 20 MHz symbol, a 40 MHz symbol and an 80 MHz symbol. For example, a 20 MHz symbol with a symbol duration of 4x has usable tones over the tone index range of [-122:-2] and [2 : 122]. In this example, the valid start tone index is -122 and the valid end tone index is 122. The guard tones are located at tone indices [-128: -123] and [123: 127]. DC tones are located at tone indices [-1: 1]. In another example, a 40 MHz symbol with a symbol duration of 4x has usable tones over the tone index range of [-250:-130], [-126:-6], [6: 126] and [130:250]. In this example, the valid start tone index is -250 and the valid end tone index is 250. In another example, an 80 MHz symbol with a symbol duration of 4x has usable tones over the range of indexes. tone of [-506:-4] and [4:506]. In this example, the valid start tone index is -506 and the valid end tone index is 506. To compress the symbols with 4x symbol duration in row 1 into a symbol with 1x d symbol duration, the symbol index valid start tone and valid end tone index for 20 MHz symbol with 1x symbol duration and a modified tone plane can be a function of the floor (and/or ceiling) of valid start and end tone indices for the symbols in row 1 divided by 4. In an example, as shown in row 1, for a 20 MHz LTF symbol with a symbol duration of 4x, the usable tones are [-122:-2] and [2: 122]. For LTF compression, the valid start tone index on a 20 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (-122/4), which equals -31. Similarly, the valid final tone index in the 20 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (122/4), which equals 30. Thus, the 20 MHz LTF symbols with 1x symbol duration in rows 2 and 3 both have tone planes with valid start and end tone indices of -31 and 30, respectively. The remaining determination for the tone plane is the number of DC tones. In DC Option 1, row 2, it is assumed that an existing notch filter is used (eg used in 802.11ac products) and thus the number of DC tones corresponds to the tone planes for symbols with symbol duration of 1x across the various frequency bandwidths to avoid tone clipping. In DC Option 1, the existing tone plan (for example, in IEEE 802.11ac) for a 20 MHz symbol with 1x symbol duration requires a DC tone. So tone index 0 can be reserved for DC tone. In DC Option 2, row 3, it is assumed that a narrower notch filter is required and therefore only a DC tone. Thus, tone index 0 can be reserved for the one DC tone. In summary, the usable tone indices for a modified tone plane for a 20 MHz LTF symbol with a symbol duration of 1x can have usable tone indices of [-31:- 1] and [1: 30] for both DC Option 1 (tier 2) and DC Option 2 (tier 3).

[0044] In another example, as shown in row 1, for a 40 MHz LTF symbol with a 4x symbol duration, the usable tones are [-250:-130], [-126: 6], and [6: 126] and [130:250]. For LTF compression, the valid start tone index on a 40 MHz LTF symbol with a symbol duration of 1x and a modified tone plane can be the result of a floor (-250/4), which is equal to -63. Similarly, the final valid tone index in the 40 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (250/4), which equals 62. Referring to FIG. 3A, the 40 MHz LTF symbols with 1x symbol duration in rows 2 and 3 have both valid start and end tone indices of -63 and 62, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 2, it is assumed that an existing notch filter is used and thus the number of DC tones corresponds to the existing tone planes for symbols with a symbol duration of 1x in the various frequency bandwidths . In DC Option 1, row 2, the existing tone plan for a 40 MHz symbol with 1x symbol duration calls for 3 DC tones. Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 3, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In summary, the usable tone indices for a modified tone plane for a 40 MHz LTF symbol with a 1x symbol duration can have usable tone indices of [-63: -2] and [2: 62] for the DC Option 1 (row 2) and [-63:-1] and [1:62] for DC Option 2 (row 3).

[0045] In yet another example, as shown in row 1, for an 80 MHz LTF symbol with a 4x symbol duration, the usable tones are [-506:-4] and [4:506]. For LTF compression, the valid start tone index on an 80 MHz LTF symbol with a symbol duration of 1x and a modified tone plane can be the result of a floor (-506/4), which is equal to -127. Similarly, the final valid tone index on the 80 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (506/4), which is equal to 126. Referring to FIG. 3A, the modified tone plan for the 80 MHz LTF symbols with 1x symbol duration in rows 2 and 3 have both valid start and stop tone indices of -127 and 126, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 2, it is assumed that an existing notch filter is used, and thus the number of DC tones corresponds to the tone planes for symbols having 1x symbol duration in the various frequency bandwidths. In DC Option 1, the 80 MHz symbol with 1x symbol duration calls for three DC tones (eg, in IEEE 802.11ac). Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 3, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In summary, the usable tone indices for a modified tone plane for an 80 MHz LTF symbol with a symbol duration of 1x can have usable tone indices of [-127:-2] and [2: 126] for the DC Option 1 (row 2) and [-127:-1] and [1 : 126] for DC Option 2 (row 3).

[0046] In the examples discussed in rows 2 and 3 of FIG. 3A, the valid start and end tone indices were asymmetric. That is, for example, for a 20 MHz LTF symbol with a symbol duration of 1x in DC Option 1, the valid start tone index is -31 and the valid end tone index is 30. In another aspect, the Valid start and end pitch indices of a modified pitch plane for a symbol with a symbol duration of 1x can be symmetric. For example, again referring to row 1, for a 20 MHz LTF symbol with a 4x symbol duration, the usable tones are [-122:-2] and [2: 122]. For LTF compression, the valid start tone index in a 20 MHz LTF symbol with a symbol duration of 1x can be the result of the ceiling (-122/4), which equals -30. The valid final tone index in the 20 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (122/4), which equals 30. Thus, the 20 MHz LTF symbols with symbol duration 1x in rows 4 and 5 both have tone planes with valid start and end tone indices of -30 and 30, respectively. The remaining determination for the tone plane is the number of DC tones. In DC Option 1, row 4, it is assumed that an existing notch filter is used (eg used in 802.11ac products) and thus the number of DC tones corresponds to the tone planes for symbols with symbol duration of 1x across the various frequency bandwidths to avoid tone clipping. In DC Option 1, the existing tone plan (for example, in IEEE 802.11ac) for a 20 MHz symbol with 1x symbol duration requires a DC tone. So tone index 0 can be reserved for DC tone. In DC Option 2, row 5, it is assumed that a narrower notch filter is required and therefore only a DC tone. Thus, tone index 0 can be reserved for the one DC tone. In summary, the usable tone indices for a modified tone plane for a 20 MHz LTF symbol with a symbol duration of 1x can have usable tone indices of [-30:-1] and [1: 30] for both DC Option 1 (row 4) and DC Option 2 (row 5).

[0047] In another example, as shown in row 1, for a 40 MHz LTF symbol with a 4x symbol duration, the usable tones are [-250:-130], [-126: 6], and [6: 126] and [130:250]. For LTF compression, the valid start tone index on a 40 MHz LTF symbol with a symbol duration of 1x and a modified tone plane can be the ceiling result (-250/4), which equals - 62. The final valid tone index on the 40 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (250/4), which equals 62. With reference to FIG. 3A, the 40 MHz LTF symbols with 1x symbol duration in rows 4 and 5 have both valid start and end tone indices of -62 and 62, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 4, it is assumed that an existing notch filter is used, and thus the number of DC tones corresponds to the existing tone planes for symbols with a symbol duration of 1x in the various frequency bandwidths . In DC Option 1, row 4, the existing tone plan for a 40 MHz symbol with 1x symbol duration calls for 3 DC tones. Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 5, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In summary, the usable tone indices for a modified tone plane for a 40 MHz LTF symbol with a symbol duration of 1x can have usable tone indices of [-62:-2] and [2: 62] for the DC Option 1 (row 4) and [-62:-1] and [1:62] for DC Option 2 (row 5).

[0048] In yet another example, as shown in row 1, for an 80 MHz LTF symbol with a 4x symbol duration, the usable tones are [-506:-4] and [4:506]. For LTF compression, the valid start tone index on an 80 MHz LTF symbol with a symbol duration of 1x and a modified tone plane can be the ceiling result (-506/4), which equals - 126. The final valid tone index in the 80 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (506/4), which equals 126. With reference to FIG. 3A, the modified tone plan for the 80 MHz LTF symbols with 1x symbol duration in rows 4 and 5 have both valid start and end tone indices of -126 and 126, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 4, it is assumed that an existing notch filter is used, and thus the number of DC tones corresponds to the tone planes for symbols having 1x symbol duration in the various frequency bandwidths. In DC Option 1, the 80 MHz symbol with 1x symbol duration calls for three DC tones (eg, in IEEE 802.11ac). Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 5, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In short, the usable tone indices for a modified tone plane for an 80 MHz LTF symbol with a symbol duration of 1x can have usable tone indices of [-126:-2] and [2: 126] for the DC Option 1 (row 4) and [-126:-1] and [1 : 126] for DC Option 2 (row 5).

[0049] The examples mentioned above with respect to rows 2 to 5 of FIG. 3A illustrate how the valid start and end tone indices for usable tones, along with the DC tone indices, can be calculated for a modified tone plane in an LTF symbol with a symbol duration of 1x of a tone plane existence of an LTF symbol with a symbol duration of 4x. Rows 6 and 7 of FIG. 3A illustrate the valid start and end tone indices for usable tones, along with the DC tone indices, for a modified tone plane in an LTF symbol with a symbol duration of 2x. With reference to rows 6 and 7, for a 20 MHz LTF symbol with a 4x symbol duration, the usable tones are [-122:-2] and [2: 122]. For LTF compression, the valid start tone index on a 20 MHz LTF symbol with a 2x symbol duration can be the result of a floor (-122/2), which equals -61. The valid final tone index in the 20 MHz LTF symbol with a symbol duration of 1x can be the result of a floor (122/2), which equals 61. Thus, the 20 MHz LTF symbols with symbol duration 2x's in rows 6 and 7 both have tone planes with valid start and end tone indices of -61 and 61, respectively. The remaining determination for the tone plane is the number of DC tones. In DC Option 1, row 6, it is assumed that an existing notch filter is used (eg used in 802.11ac products) and thus the number of DC tones corresponds to the tone planes for symbols with symbol duration of 2x across the various frequency bandwidths to avoid tone clipping. In DC Option 1, the existing tone plan (for example, in IEEE 802.11ac) for a 20 MHz symbol with 2x symbol duration requires a DC tone. So tone index 0 can be reserved for DC tone. In DC Option 2, row 7, it is assumed that a narrower notch filter is required and therefore only a DC tone. Thus, tone index 0 can be reserved for the one DC tone. In summary, the usable tone indices for a modified tone plane for a 20 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [-61: - 1] and [1: 61] for both DC Option 1 (row 6) and DC Option 2 (row 7).

[0050] In another example, as shown in row 1, for a 40 MHz LTF symbol with a 4x symbol duration, the usable tones are [-250:-130], [-126:6], and [6: 126] and [130:250]. For LTF compression, the valid start tone index on a 40 MHz LTF symbol with a symbol duration of 2x and a modified tone plane can be the result of a floor (-250/2), which is equal to -125. The final valid tone index on the 40 MHz LTF symbol with a symbol duration of 2x can be the result of a floor (250/2), which equals 125. With reference to FIG. 3A, the 40 MHz LTF symbols with 2x symbol duration in rows 6 and 7 have both valid start and end tone indices of -125 and 125, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 6, it is assumed that an existing notch filter is used and thus the number of DC tones corresponds to the existing tone planes for symbols with a symbol duration of 2x in the various frequency bandwidths . In DC Option 1, row 6, the existing tone plan for a 40 MHz symbol with 2x symbol duration calls for 3 DC tones. Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 7, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In summary, the usable tone indices for a modified tone plane for a 40 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [-125:-2] and [2: 125] for the DC Option 1 (row 6) and [125:-1] and [1 : 125] for DC Option 2 (row 7).

[0051] In yet another example, as shown in row 1, for an 80 MHz LTF symbol with a 4x symbol duration, the usable tones are [-506:-4] and [4:506]. For LTF compression, the valid start tone index on an 80 MHz LTF symbol with a symbol duration of 2x and a modified tone plane can be the result of a floor (-506/2), which equals -253. The final valid tone index on the 80 MHz LTF symbol with a symbol duration of 2x can be the result of a floor (506/2), which is equal to 253. With reference to FIG. 3A, the modified tone plan for the 80 MHz LTF symbols with 1x symbol duration in rows 6 and 7 have both valid start and stop tone indices of -253 and 253, respectively. The remaining determination is the number of DC tones. In DC Option 1, row 6, it is assumed that an existing notch filter is used, and thus the number of DC tones corresponds to the tone planes for symbols having 2x symbol duration in the various frequency bandwidths. In DC Option 1, the 80 MHz symbol with 2x symbol duration calls for three DC tones (eg, in IEEE 802.11ac). Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In DC Option 2, row 6, it is assumed that a narrower notch filter is required and therefore only a DC tone can be used. So tone index 0 can be reserved for DC tone. In summary, the usable tone indices for a modified tone plane for an 80 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [-253: -2] and [2: 253] for the DC Option 1 (row 6) and [-253:-1] and [1:253] for DC Option 2 (row 7).

[0052] In both types of LTF symbols (for example, 1x symbol duration and 2x symbol duration), the LTF compression option allows you to reduce the LTF symbol overhead compared to LTF symbols with symbol duration of 4x. In one aspect, the modified pitch planes in lines 2-7 of FIG. 3A can be pre-configured (eg hardcoded into an STA or AP).

[0053] In short, an AP or STA can transmit frames containing LTF symbols with modified tone planes while using symbols with 4x symbol duration for data. For example, an AP (e.g. AP 202) may transmit user data to an STA (e.g. STA 206) on a 20 MHz data symbol (e.g. data symbol 268), in which the symbol 20 MHz data stream has a symbol duration of 4x and a usable tone rate range of [-122:2] and [2:122]. Additionally, for channel estimation purposes, the AP may transmit to the STA an LTF (or at least part of an LTF) in a 20 MHz LTF symbol (for example, LTF symbol 266), in which the 20 MHz LTF symbol MHz has a symbol duration of 1x and a usable tone index range of [-30:-1] and [1:30].

[0054] In another embodiment, FIG. 3B illustrates an existing LTF symbol with a symbol duration of 4x (row 1) that is used to derive a modified tone plane for LTF symbols with a symbol duration of 2x (row 2). To address the second issue regarding channel estimation around DC tones, FIG. 3A offers two options. DC option 1 (for example, in row 2) assumes that the same notch match filter used for a 1x LTF symbol in IEEE 802.11ac is used for the 2x LTF symbol. Thus, if 802.11ac has 1 DC tone for a 1x symbol duration, then 3 DC tones can be reserved for a 2x symbol duration (shown), and if 802.11ac has 3 DC tones for a 1x symbol duration, then 5 DC tones can be reserved for a 2x symbol. In contrast, DC Option 2 (e.g. row 3) assumes that a new notch filter that is sharper and with a narrower notch can be used (compared to the notch filter used in 802.11ac) so that only three DC tones are needed in the modified LTF symbol tone plane with a symbol duration of 2x. Unlike DC Option 2 in Fig. 3A, DC Option 2 in Fig. 3B assumes a slightly wider notch filter.

[0055] With reference to FIG. 3B, assuming a wireless network (e.g., the wireless network in FIGS. 1, 2) uses symbols with a symbol duration of 2x, row 1 of the diagram illustrates the usable tone rates for a 20 MHz symbol, a 40 MHz symbol and an 80 MHz symbol. For example, a 20 MHz symbol with a symbol duration of 4x has usable tones over the tone index range of [-122:-2] and [2 : 122]. In this example, the valid start tone index is -122 and the valid end tone index is 122. The guard tones are located at tone indices [-128: -123] and [123: 127]. DC tones are located at tone indices [-1: 1]. In another example, a 40 MHz symbol with a symbol duration of 4x has usable tones over the tone index range of [-250:-130], [-126:-6], [6: 126] and [130:250]. In this example, the valid start tone index is -250 and the valid end tone index is 250. In another example, an 80 MHz symbol with a symbol duration of 4x has usable tones over the range of indexes. tone of [-506:-4] and [4:506]. In this example, the valid start tone index is -506 and the valid end tone index is 506. To compress the symbols with 4x symbol duration in row 1 into a symbol with 2x symbol duration, the symbol index valid start tone and valid end tone index for the 20 MHz symbol with 2x symbol duration and a modified tone plan can be a function of the valid start and end tone indices for the symbols in row 1 divided by 2. In an example, as shown in row 1, for a 20 MHz LTF symbol with a 4x symbol duration, the usable tones are [-122:-2] and [2: 122]. For LTF compression, the valid start tone index in a 20 MHz LTF symbol with a 2x symbol duration can equal -61. Similarly, the valid end tone index in the 20 MHz LTF symbol with a symbol duration of 2x can be equal to 61. Thus, the 20 MHz LTF symbols with a symbol duration of 2x in rows 2 and 3 have both tone planes with valid start and end tone indices of -61 and 61, respectively. The remaining determination for the tone plane is the number of DC tones. In DC Option 1 row 2 it is assumed that an existing notch filter is used (e.g. used in 802.11ac products) and so the number of DC tones can be based on the tone planes for symbols with duration of 1x symbol in the various frequency bandwidths to avoid tone clipping. In DC Option 1, the existing tone plan (for example, in IEEE 802.11ac) for a 20 MHz symbol with 1x symbol duration requires a DC tone. Thus, three tone indices -1, 0 and 1 can be reserved for a symbol duration of 2x. In DC Option 2, it is assumed that a narrower notch filter and therefore only three DC tones may be required regardless of the number of DC tones in the duration of the 1x symbol. Thus, tone indices -1, 0, and 1 can be reserved for 2x symbol duration. In summary, the usable tone indices for a modified tone plane for a 20 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [61: - 2] and [2: 61] for Option DC 1 and DC Option 2.

[0056] In another example, as shown in row 1, for a 40 MHz LTF symbol with a 4x symbol duration, the usable tones are [-250:-130], [-126:6], and [6: 126] and [130:250]. For LTF compression, the valid start tone index in a 40 MHz LTF symbol with a symbol duration of 2x and a modified tone plane can equal -125. Similarly, the valid endtone index in the 40 MHz LTF symbol with a 2x symbol duration can be equal to 125. Referring to FIG. 3B, the 40 MHz LTF symbols with 2x symbol duration in rows 2 and 3 have both valid start and end tone indices of -125 and 125, respectively. The remaining determination is the number of DC tones. Assuming the same notch filter assumptions apply as discussed with respect to the 20 MHz symbol, in DC Option 1, the existing tone plan for a 40 MHz symbol with 1x symbol duration calls for three DC tones. Thus, tone indices -2, -1, 0, 1 and 2 can be reserved for DC tones. In DC Option 2 it is assumed that a narrower notch filter can be used and therefore only three DC tones can be used. Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In summary, the usable tone indices for a modified tone plane for a 40 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [-125:-3] and [3: 125] for the DC Option 1 and [-125:-2] and [2 : 125] for DC Option 2.

[0057] In yet another example, as shown in row 1, for an 80 MHz LTF symbol with a 4x symbol duration, the usable tones are [-506:-4] and [4:506]. For LTF compression, the valid start tone index in an 80 MHz LTF symbol with a symbol duration of 2x and a modified tone plane can equal -253. Similarly, the valid endtone index in the 80 MHz LTF symbol with a 2x symbol duration can be equal to 253. Referring to FIG. 3B, the modified tone plan for the 80 MHz LTF symbols with 2x symbol duration in rows 2 and 3 have both valid start and end tone indices of -253 and 253, respectively. The remaining determination is the number of DC tones. Assuming the same notch filter assumptions apply as discussed with respect to the 20 MHz symbol, in DC Option 1, the existing tone plan for an 80 MHz symbol with 2x symbol duration can have three DC tones. Thus, tone indices -2, -1, 0, 1 and 2 can be reserved for DC tones. In DC Option 2 it is assumed that a narrower notch filter can be used and therefore only three DC tones can be used. Thus, tone indices -1, 0 and 1 can be reserved for DC tones. In summary, the usable tone indices for a modified tone plane for an 80 MHz LTF symbol with a 2x symbol duration can have usable tone indices of [-253: -3] and [3: 253] for the DC Option 1 and [-253:-2] and [2:253] for DC Option 2.

[0058] In the examples mentioned above with respect to rows 2 and 3 of FIG. 3B illustrate how the valid start and end tone indices for usable tones, along with the DC tone indices, can be calculated for a modified tone plane in an LTF symbol with a symbol duration of 2x of a tone plane existence of an LTF symbol with a symbol duration of 4x. A modified LTF symbol allows for reduced LTF symbol overhead compared to LTF symbols with 4x symbol duration. In one aspect, the modified pitch planes in rows 2 and 3 of FIG. 3B can be pre-configured (eg hardcoded into an STA or AP).

[0059] In short, an AP or STA can transmit frames containing LTF symbols with modified tone planes while using symbols with 4x symbol duration for data. For example, the AP (e.g., AP 202) may transmit to an STA user data (e.g., STA 206) on a 20 MHz data symbol (e.g., data symbol 268), in which the symbol 20 MHz data stream has a symbol duration of 4x and a usable tone rate range of [-122:2] and [2:122]. Additionally, for channel estimation purposes, the AP may transmit to the STA an LTF (or at least part of an LTF) on a 20 MHz LTF symbol (for example, LTF symbol 266), in which the 20 MHz LTF symbol MHz has a symbol duration of 2x and a usable tone rate range of [-61:-2] and [2:61].

[0060] In another embodiment, FIG. 3C illustrates an existing LTF symbol with a symbol duration of 4x (row 1) that is used to derive a modified tone plan for LTF symbols with a symbol duration of 1x (rows 2, 3). In one aspect, the tone planes in rows 2, 3 can be derived from the tone plane in row 1 by performing a 4x reduction of the usable tones in row 1. That is, every fourth tone of a tone plane in row 1 1 can be filled over the tone planes in rows 2, 3.

[0061] 20 MHz - Option 1

[0062] In one example, row 1 illustrates a 20 MHz symbol with a 4x symbol duration that has usable tones [-122:-2] and [2:122]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartIndex: 4: DCLeftindex - 1]U [DC Rightindex + 1:4:4xValidEndIndex] 4 '

[0063] The above equation represents inputs used to derive a range of tonal indices for a symbol of 1x symbol duration. 4xValidStartIndex is the valid start pitch index for a symbol with a symbol duration of 4x, DCLeftlndex is a leftmost DC pitch index of the symbol, DCRightlndex is a rightmost DC pitch index of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the symbol LTF with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, -0.5, is used to map the LTF signal to an integer tone index.

[0064] This approach reduces the extrapolation to 4x tones. Continuing with the example, the tone indices for a symbol with a symbol duration of 1x can be filled in tone indices [-30.5: 30.5], determined based on {[-122: 4: -2 ] U [2: 4: 122]}/4. In this case, each fractional pitch index separated by a pitch pitch spacing of 1 is padded (for example, -30.5, -29.5, -28.5,..., 30.5). To map fractional tone indices to whole tone indices for the purpose of packaging the LTF symbol, the tone indices can be shifted by -0.5 (half a step down) to derive the tone indices in row 2 of FIG. . 3C. Thus, the tone indices to be packed include the range [31: 30], where {[-122: 4: -2] U [2: 4: 122]}/4 — 0.5 = [31 :30 ]. In this example, the integer tone indices include a DC tone, so the DC tone is also packed. To avoid transmitting on a DC tone (tone index 0), after wrapping the LTF symbol (e.g. by inserting information into the LTF symbol at the various tone indexes), the tone index [-31:30] can be shifted by +0.5 (one halftone shift upward, corresponding to a time-domain phase ramp) to generate broadcast signals in tones of [-31: 30] + 0.5 = [-30.5: 30.5]. Additionally, the halftone offset allows transmission to occur at the exact frequency instants of [4xValidStartIndex: 4: DCLeftIndex-1 DCRightIndex+1 :4:4xValidEndToneIndex]/4. After this change, signals are transmitted in pitch indices -30.5, -29.5, -28.5, 29.5, 30.5, where each pitch index is separated by a value of 1. A transmission at tone index 0 (DC tone) is avoided.

[0065] 40 MHz - Option 1

[0066] In another example, row 1 illustrates a 40 MHz symbol with a 4x symbol duration that has usable tones [-250:-130] and [-126:-6], [6: 126] and [ 130:250]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartIndex: 4: DCLeftlndex - 1] U[DCRightIndex + 1:4:4xValidEndIndex] 4 '

[0067] The 4xValidStartIndex is the valid start tone index for a symbol with a symbol duration of 4x, the DCLeftlndex is an index of the leftmost DC tone of the symbol, the DCRightlndex is an index of the furthest DC tone right of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the symbol LTF with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, -0.5, is used to map the LTF signal to an integer tone index.

[0068] This approach reduces extrapolation to 4x tones. Continuing with the example, the pitch indices for a symbol with a symbol duration of 1x can be filled into pitch indices [-62.5: -1.5] U [1.5: 62.5], determined with base on {{[-250:4:-130]U[-126:4:-6]U[6:4:126]U[130:4:250]}/4. In this case, almost all fractional tone indices separated by a pitch indices spacing of 1 are padded (e.g. -62.5, -61.5, -60.5,..., -1.5 , 1.5, 2.5, ..., 62.5). To map fractional tone indices to whole tone indices for the purpose of packing the LTF symbol, the tone indices can be shifted by -0.5 (half a step down) to derive the tone indices in row 2. Thus , {[-250:4:-130] U [-126:4:-6] U [6:4: 126] U [130:4:250]}/4 - 0.5 = [-63 :-2] U [1 :62]. Subsequently, the pitch indexes [-63 :-2] U [1 :62] can be shifted by +0.5 (an upward shift of half a step, corresponding to a time-domain phase ramp) to generate signals transmission rate in tones of [-62:-2] U [1 :62] + 0.5 = [-61.5:-1.5] U [1.5:62.5]. Halftone shift allows transmission to occur at the exact frequency instants of [4xValidStartIndex:4:DCLeftIndex-1 DCRightIndex+1 :4:4xValidEndToneIndex]/4. After this change, signals are transmitted at tone indices -61.5, -60.5, -59.5, -1.5, 1.5, 2.5, 62.5, where each tone index is separated by a value of 1. Transmission at tone index 0 (DC tone) is avoided.

[0069] 80 MHz - Option 1

[0070] In another example, row 1 illustrates an 80 MHz symbol with a symbol duration of 4x that has usable tones [-506:-2] and [2:506]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartIndex: 4: DCLeftlndex - 1] U[DCRightI ndex + 1:4:4xValidEndIndex] 4 '

[0071] The 4xValidStartIndex is the valid start tone index for a symbol with a symbol duration of 4x, the DCLeftlndex is an index of the leftmost DC tone of the symbol, the DCRightlndex is an index of the furthest DC tone right of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the LTF symbol with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, -0.5, is used to map the LTF signal to an integer tone index.

[0072] This approach reduces the extrapolation to 4x tones. Continuing with the example, the tone indices for a symbol with a symbol duration of 1x can be filled into tone indices [-126.5: 126.5], determined based on {[-506:4:-2 ] U[2:4:506]}/4. In this case, each fractional pitch index separated by a pitch pitch spacing of 1 is padded (for example, -126.5, -125.5, -124.5, ... , 126.5). To map fractional tone indices to whole tone indices for the purpose of packing the LTF symbol, the tone indices can be shifted by -0.5 (half a step down) to derive the tone indices in row 2. Thus , the tone indices to pack include the range [127:126], where {[504:4:-2] U[2:4:506]}/4 - 0.5 = [-127:126] . In this example, the integer tone indices include at least one DC tone, and therefore the at least one DC tone is also packed. To avoid actually transmitting in the DC tone, the tone index [-127 :126] can be shifted by +0.5 (an upward shift of half a tone, corresponding to a time domain phase ramp) to generate broadcast in tones of [-127: 126] + 0.5 = [-126.5: 126.5]. Halftone shift allows transmission to occur at the exact frequency instants of [4xValidStartIndex:4:DCLeftIndex-1 DCRightIndex+1 :4:4xValidEndToneIndex]/4. After this change, signals are transmitted in pitch indices -126.5, -125.5, -124.5, 126.5, where each pitch index is separated by a value of 1. tone 0 (DC tone) is also avoided.

[0073] 20 MHz - Option 2

[0074] In one example, row 1 illustrates a 20 MHz symbol with a 4x symbol duration that has usable tones [-122:-2] and [2:122]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartindex: 4: DCLeftlndex - l]U[DCRightIndex + 1:4:4xValidEndIndex] 4 '

[0075] The 4xValidStartIndex is the valid start tone index for a symbol with a symbol duration of 4x, the DCLeftlndex is a leftmost DC tone index of the symbol, the DCRightlndex is a farthest DC tone index right of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the LTF symbol with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, +0.5, is used to map the LTF signal to an integer tone index.

[0076] This approach reduces the extrapolation to 4x tones. Continuing with the example, the tone indices for a symbol with a symbol duration of 1x can be filled in tone indices [-30.5: 30.5], determined based on {[-122: 4: -2 ] U [2: 4: 122]}/4. In this case, each fractional pitch index separated by a pitch pitch spacing of 1 is padded (for example, -30.5, -29.5, -28.5,... , 30.5). To map fractional tone indices to whole tone indices for the purpose of packaging the LTF symbol, the tone indices can be shifted by +0.5 (up half a step) to derive the tone indices in row 3 of FIG. . 3C. Thus, {[-122:4:-2] U [2:4: 122]}/4 + 0.5 = [-30:31]. In this example, the integer tone indices include a DC tone. To avoid transmitting on a DC tone (tone index 0), after wrapping the LTF symbol (e.g. by inserting information into the LTF symbol at the various tone indices), the tone index [-30:31] can be shifted by -0.5 (one halftone shift down, corresponding to a time-domain phase ramp) to generate broadcast signals in tones of [-30: 31] - 0.5 = [-30.5: 30.5]. Additionally, the halftone offset allows transmission to occur at the exact frequency instants of [4xValidStartIndex:4:DCLeftIndex-1 DCRightlndex+1 :4:4xValidEndToneIndex]/4. After this shift, signals are transmitted in pitch indices -30.5, -29.5, -28.5, ... , 29.5, 30.5, where each pitch index is separated by a value of 1. Transmission at tone index 0 (DC tone) is avoided.

[0077] 40 MHz - Option 2

[0078] In another example, row 1 illustrates a 40 MHz symbol with a 4x symbol duration that has usable tones [-250:-130] and [-126:-6], [6: 126] and [ 130:250]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartIndex: 4: DCLeftlndex - 1] U[DCRightI ndex + 1:4:4xValidEndIndex] 4 '

[0079] The 4xValidStartIndex is the valid start tone index for a symbol with a symbol duration of 4x, the DCLeftlndex is an index of the leftmost DC tone of the symbol, the DCRightlndex is an index of the farthest DC tone right of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the symbol LTF with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, +0.5, is used to map the LTF signal to an integer tone index.

[0080] This approach reduces the extrapolation to 4x tones. Continuing with the example, the pitch indices for a symbol with a symbol duration of 1x can be filled into pitch indices [-62.5: -1.5] U [1.5: 62.5], determined with base on {{[-250:4:-130]U[-126:4:-6]U[6:4:126]U[130:4:250]}/4. In this case, almost all fractional tone indices separated by a pitch indices spacing of 1 are padded (e.g. -62.5, -61.5, -60.5,..., -1.5 , 1.5, 2.5, ..., 62.5). To map fractional tone indices to whole tone indices for the purpose of packaging the LTF symbol, the tone indices can be shifted by +0.5 (up half a step) to derive the tone indices in row 3 of FIG. . 3C. So {[-250:- 4: 130] U [-126:4:-6] U [6:4: 126] U [130:4:250]}/4 + 0.5 = [-62: -l]U[2:63]. Subsequently, the pitch indexes [-62 :-1] U [2 :63] can be shifted by -0.5 (a half-tone upward shift, corresponding to a time-domain phase ramp) to generate signals transmission rate in the tones of [-62:-1] U [2 :63] + 0.5 = [-62.5: 1.5] U [1.5:62.5]. Halftone shift allows transmission to occur at the exact frequency instants of [4xValidStartIndex:4:DCLeftIndex-1 DCRightlndex+1 :4:4xValidEndToneIndex]/4. After this change, signals are transmitted at tone indices -62.5, -61.5, -60.5, -1.5, 1.5, 2.5, 62.5, where each tone index is separated by a value of 1. Transmission at tone index 0 (DC tone) is avoided.

[0081] 80 MHz - Option 2

[0082] In another example, row 1 illustrates an 80MHz symbol with a symbol duration of 4x that has usable tones [-506:-2] and [2:506]. The tones in an LTF symbol with a symbol duration of 4x can be reduced so that every fourth tone of a symbol with a symbol duration of 4X is mapped to an LTF symbol with a symbol duration of 1x, so that the LTF symbol with a symbol duration of 1x would have valid start and end tone indices determined based on the following expression: [4xValidStartIndex: 4: DCLeftlndex - l]U[DCRightIndex + 1:4:4xValidEndIndex] 4 '

[0083] The 4xValidStartIndex is the valid start tone index for a symbol with a symbol duration of 4x, the DCLeftlndex is an index of the leftmost DC tone of the symbol, the DCRightlndex is an index of the farthest DC tone right of the symbol and the 4xValidEndIndex is the valid ending pitch index for the symbol. The value “4” between 4xValidStartIndex and DCLeftlndex and between DCRightlndex and 4xValidEndIndex indicates that every fourth tone of a symbol with a symbol duration of 4x is mapped to the LTF symbol with a symbol duration of 1x. DCLeftlndex-1 represents the first pitch index to the left of the DCLeftlndex, and DCRightlndex + 1 represents the first pitch index to the right of the DCRightlndex. The value, +0.5, is used to map the LTF signal to an integer tone index.

[0084] This approach reduces the extrapolation to 4x tones. Continuing with the example, the tone indices for a symbol with a symbol duration of 1x can be filled into tone indices [-126.5: 126.5], determined based on {[-506:4:-2 ] U[2:4:506]}/4. In this case, each fractional pitch index separated by a pitch pitch spacing of 1 is padded (for example, -126.5, -125.5, -124.5, ... , 126.5). To map fractional tone indices to whole tone indices for the purpose of packing the LTF symbol, the tone indices can be shifted by +0.5 (up half a step) to derive the tone indices in row 3. So , {[-504:4:-2] U [2:4:506]}/4 + 0.5 = [-126: 127]. Subsequently, the [-126:127] tone indices can be shifted by -0.5 (a half-tone downward shift, corresponding to a time-domain phase ramp) to generate broadcast signals in the tones of [- 127: 127] - 0.5 = [-126.5: 126.5]. Halftone shift allows transmission to occur at exact frequency instants of [4xValidStartIndex: 4: DCLeftIndex-1 DCRightIndex+1 :4:4xValidEndToneIndex]/4. After this change, signals are transmitted in tone indices -126.5, -125.5, -124.5, 126.5, where each tone index is separated by a value of 1. tone 0 (DC tone) is also avoided.

[0085] Based on the tone planes in row 2, for example, the STA 206 can use a 20 MHz LTF symbol with 1x symbol duration having tone indices [31:30] to transmit the LTF. The LTF symbol can be packed into tone indices [-31:30] based on sampled signals associated with a 4x 20MHz LTF symbol. After packetizing the 20 MHz 1x LTF symbol, the STA can transmit information (e.g. LTF information) in the 1x 20 MHz LTF symbol with halftone upshift (e.g. [-30.5: 30.5] ). The 20 MHz LTF 1x symbol can be received by the AP 202, for example. In one configuration, the AP 202 may perform a reverse phase ramp to associate signals received on the LTF symbol with integer tone indices (e.g., perform a reverse phase ramp from -0.5 to go from [-30.5: 30.5] to [-31:30]). Afterwards, the AP 202 can perform a 1x FFT to recover the LTF signals at whole tone indices in 1x tones. In another configuration, the AP 202 can avoid inverse phase ramping by direct oversampling (eg, using 2x/4x FFT), to map the received signal to appropriate tone indices in 2x or 4x symbol tones. Although this example uses a STA as the transmitter and an AP as the receiver, the AP can be the transmitter and the STA can be the receiver. This operation/procedure also applies to tone planes in row 3.

[0086] FIGs. 4A-B are exemplary tone planes/indices diagrams 400 and 450 for LTF compression. However, instead of modifying the tone plane for an LTF symbol with 1x or 2x symbol duration in the various frequency bandwidths (eg, 20 MHz, 40 MHz, 80 MHz) as shown in FIGs. 3A-B, another option is to use an existing tone plan for an LTF symbol with a symbol duration of 1x or 2x (e.g., per IEEE 802.11ac) and modify the tone plan for data symbols with a symbol duration of 4x. For example, as shown in FIG. 4A, a 20 MHz symbol with a symbol duration of 1x has usable tones over the tone index range of [-28:1] and [1 :28]. A 40 MHz symbol with a symbol duration of 1x has usable tones over the tone index range of [-58:-2] and [2:58]. And an 80 MHz symbol with a symbol duration of 1x has usable tones over the tone index range of [-122:-2] and [2 : 122]. Based on the existing tone planes in row 1, the tone planes corresponding to a data symbol with a symbol duration of 4x can be determined by multiplying the valid start and end indices of the tone plane for an LTF symbol with the symbol duration 1x by 4. In one example, for a 20 MHz LTF symbol with a symbol duration of 1x, the tone plane has usable tones at tone indices [-28:-1] and [1:58] (eg, as per IEEE 802.11n and 802.11ac). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol (e.g., data symbol 268) can be determined by -28 * 4 = -112 and the final valid tone index can be determined by 28 * 4 = 112. Regarding the DC tones in a data symbol with a symbol duration of 4x, the DC tones may not need to be 4 times the number of DC tones as in the tone plane for a symbol of 1x symbol duration. Instead, if a symbol of 1x symbol duration has 1 DC tone, the corresponding data symbol of 4x symbol duration can have 3-4 DC tones to provide the same frequency width for notch filtering. And, if a symbol of 1x symbol duration has 3 DC tones, the corresponding data symbol of 4x symbol duration can have 7-8 DC tones. As shown in row 1, the 20 MHz data symbol of 1x symbol duration has a DC tone. Thus, as shown in row 2, the 4x symbol duration 20 MHz data symbol has 3 DC tones, and therefore the modified tone plane can have usable tone indices ranging from [-112:-2] to [2: 112]. The total number of usable tones equals the valid end tone index minus the valid start tone index plus one minus the number of DC tones. The total number of usable tones will be divided into data tones and pilot tones. In one aspect, this tone plane can have 210 data tones and 12 pilot tones for a total of 222 usable tones.

[0087] In another example, for a 40 MHz LTF symbol with a symbol duration of 1x, the tone plane has usable tones at tone indices [-58:-2] and [2:58] (e.g., as per the IEEE 802.11n and 802.11ac wireless standards). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol can be determined by -58 * 4= -232 and the valid end tone index can be determined by 58 * 4 = 232. Regarding the DC tones in a 40 MHz data symbol with a symbol duration of 1x, there are 3 DC tones. Thus, as shown in row 2, the 4x symbol duration 40 MHz data symbol has 7 DC tones, and therefore the modified tone plane can have usable tone indices ranging from [-232:4] to [ 4:232]. In one aspect, this tone plane can have 444 data tones and 14 pilot tones for a total of 458 usable tones.

[0088] In yet another example, for an 80 MHz LTF symbol with a symbol duration of 1x, the tone plane has usable tones at tone indices [-122:-2] and [2: 122] (ex. , such as by IEEE 802.11n and 802.11ac). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol can be determined by -122 * 4= -488 and the valid end tone index can be determined by 122 * 4 = 488. Regarding the DC tones in an 80 MHz data symbol with a symbol duration of 1x, there are 3 DC tones. Thus, as shown in row 2, the 80 MHz data symbol of 4x symbol duration has 7 DC tones, and therefore, the modified tone plane can have usable tone indices ranging from [-488:4] to [ 4:488]. In one aspect, this tone plane can have 954 data tones and 16 pilot tones for a total of 970 usable tones.

[0089] In another embodiment, as shown in row 1 of FIG. 4B, a 20 MHz symbol with a symbol duration of 2x has usable tones over the tone index range of [-58:-2] and [2:58]. A 40 MHz symbol with a symbol duration of 2x has usable tones over the tone index range of [-122:2] and [2 : 122]. And an 80 MHz symbol with a symbol duration of 2x has usable tones over the tone index range of [-250:-3] and [3:250]. Based on the existing tone planes in row 1 of FIG. 4B, the tone planes corresponding to a data symbol with a symbol duration of 4x can be determined by multiplying the valid start and end indices of the tone plane for an LTF symbol with a symbol duration of 2x by 2. For example, for a 20 MHz LTF symbol with a symbol duration of 2x, the tone plane has usable tones at tone indices [-58:-2] and [2:58] (e.g., as per IEEE 802.11n and 802.11ac). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol (e.g., data symbol 268) can be determined by -58 * 2 = -116 and the final valid tone index can be determined by 58 * 2 = 116. Regarding the DC tones in a data symbol with a symbol duration of 4x, the DC tones may not need to be 2 times the number of DC tones as in the tone plane for a symbol of 2x symbol duration. Instead, if a symbol of 2x symbol duration has 3 DC tones, the corresponding data symbol of 4x symbol duration can have 5 DC tones to provide the same frequency width for notch filtering. And, if a symbol of 2x symbol duration has 5 DC tones, the corresponding data symbol of 4x symbol duration can have 7 DC tones. As shown in row 1 of FIG. 4B, the 1x symbol duration 20 MHz data symbol has 3 DC tones. Thus, as shown in row 2 of FIG. 4B, the 4x symbol duration 20 MHz data symbol has 5 DC tones, and therefore, the modified tone plane can have usable tone indices ranging from [-116:-3] to [3:116]. The total number of usable tones equals the valid end tone index minus the valid start tone index plus one minus the number of DC tones. The total number of usable tones will be divided into data tones and pilot tones. In one aspect, this tone plane can have 216 data tones and 12 pilot tones for a total of 228 usable tones.

[0090] In another example, for a 40 MHz LTF symbol with a symbol duration of 2x, the tone plane has usable tones at tone indices [-122:-2] and [2: 122] (e.g., as per the IEEE 802.11n and 802.11ac wireless standards). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol can be determined by -122 * 2= -244 and the valid end tone index can be determined by 122 * 2 = 244. Regarding the DC tones in a 40 MHz data symbol with a symbol duration of 2x, there are 3 DC tones. Thus, as shown in row 2 of FIG. 4B, the 4x symbol duration 40 MHz data symbol has 5 DC tones, and therefore, the modified tone plane can have usable tone indices ranging from [-244:-3] to [3:244]. In one aspect, this tone plane can have 468 data tones and 16 pilot tones for a total of 484 usable tones.

[0091] In yet another example, for an 80 MHz LTF symbol with a symbol duration of 2x, the tone plane has usable tones at tone indices [-250:-3] and [3:250] (ex. , as well as by IEEE 802.11n and 802.11ac). To facilitate the reconstitution of the channel estimates in a data symbol with a symbol duration of 4x, the valid start tone index in the data symbol can be determined by -250 * 2= -500 and the valid end tone index can be determined by 250 * 2 = 250. Regarding the DC tones in an 80 MHz data symbol with a symbol duration of 2x, there are 5 DC tones. Thus, as shown in row 2 of FIG. 4B, the 4x symbol duration 80 MHz data symbol has 7 DC tones, and therefore, the modified tone plane can have usable tone indices ranging from [500:-4] to [4:500]. In one aspect, this tone plane can have 978 data tones and 16 pilot tones for a total of 994 usable tones.

[0092] In short, an AP or a STA can transmit frames containing LTF information in LTF symbols and user data in data symbols. In one embodiment, the LTF symbols can have a symbol duration of 1x and utilize existing tone planes for symbols of symbol duration 1x. Data symbols can use a modified tone plane based on an existing tone plane for 1x symbol duration symbols. In one example, the AP (e.g., AP 202) may transmit user data to an STA (e.g., STA 206) on a 20 MHz data symbol (e.g., data symbol 268), in which the 20 MHz data symbol has a symbol duration of 4x and a usable tone rate range of [-112:2] and [2:112]. Additionally, for channel estimation purposes, the AP may transmit to the STA an LTF on a 20 MHz LTF symbol (for example, LTF symbol 266), where the 20 MHz LTF symbol has a symbol duration of 1x and a usable tone index range of [-28:-1] and [1:28].

[0093] In another example, LTF symbols can have a symbol duration of 2x and use existing tone planes for symbols of symbol duration 2x. Data symbols can use a modified tone plane based on an existing tone plane for 2x symbol duration symbols. For example, the AP (e.g., AP 202) may transmit to an STA user data (e.g., STA 206) on a 20 MHz data symbol (e.g., data symbol 268), in which the symbol 20 MHz data rate has a symbol duration of 4x and a usable tone rate range of [-116: -3] and [3: 116]. Additionally, for channel estimation purposes, the AP may transmit to the STA an LTF on a 20 MHz LTF symbol (for example, LTF symbol 266), where the 20 MHz LTF symbol has a symbol duration of 2x and a usable tone index range of [-58:-2] and [2:58].

[0094] In yet another example, the LTF symbols may have a modified 2x symbol duration (e.g. in FIGs. 3A-B). Data symbols can use an existing tone plane for 4x symbol duration symbols. For example, the AP (e.g., AP 202) may transmit user data to an STA (e.g., STA 206) on a 20 MHz data symbol (e.g., data symbol 268), in which the 20 MHz data symbol has a symbol duration of 4x and a usable tone rate range of [-122:-2] and [2:122]. And, for channel estimation purposes, among others, the AP can transmit to the STA an LTF on a 20 MHz LTF symbol (for example, LTF symbol 266), where the 20 MHz LTF symbol has a symbol duration of 2x and a usable tone index range of [-61: -2] and [2: 61].

[0095] FIG. 5 shows an exemplary functional block diagram of a wireless device 502 that may be employed within the wireless communication system 100 of FIG. 1 and can use a modified tone plane. Wireless device 502 is an example of a device that can be configured to implement the various methods described herein. For example, wireless device 502 can be AP 104, AP 202, STAs 1 12, 1 14, 116, 1 18, or STAs 206, 208, 210, 212.

[0096] Wireless device 502 may include a processor 504 that controls the operation of wireless device 502. Processor 504 may also be referred to as a central processing unit (CPU). Memory 506, which may include both read-only memory (ROM) and random access memory (RAM), may provide instructions and data to processor 504. A portion of memory 506 may also include non-volatile random access memory (NVRAM) ). Processor 504 typically performs arithmetic and logic operations based on program instructions stored in memory 506. Instructions in memory 506 may be executable (by processor 504, for example) to implement the methods described herein.

[0097] Processor 504 may comprise or be a component of a processing system implemented with one or more processors. The one or more processors may be implemented with any combination of general purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGA), programmable logic devices (PLD), controllers, state machines, closed logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of the information.

[0098] The processing system may also include machine-readable media to store the software. Software should be interpreted broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (for example, in source code format, binary code format, executable code format, or any other suitable code format). Instructions, when executed by one or more processors, cause the processing system to perform the various functions described here.

[0099] The wireless device 502 may also include a housing 508, and the wireless device 502 may include a transmitter 510 and a receiver 512 to enable transmission and reception of data between the wireless device 502 and a remote device. Transmitter 510 and receiver 512 may be combined into one transceiver 514. An antenna 516 may be attached to housing 508 and electrically coupled to transceiver 514. Wireless device 502 may also include, multiple transmitters, multiple receivers, multiple transceivers and/or or multiple antennas.

[0100] The wireless device 502 may also include a signal detector 518 that may be used to detect and quantify the level of signals received by the transceiver 514 and the receiver 512. The signal detector 518 may detect these signals as total energy, energy per subcarrier per symbol, power spectral density, and other signals. Wireless device 502 may also include a digital signal processor (DSP) 520 for use in signal processing. The DSP 520 can be configured to generate a packet for transmission. In some aspects, the packet may comprise a PPDU.

[0101] The wireless device 502 may further comprise a user interface 522, in some aspects. User interface 522 may comprise a keyboard, microphone, speaker, and/or display. User interface 522 can include any element or component that transmits information to a user from wireless device 502 and/or receives input from the user.

[0102] When wireless device 502 is implemented as an AP (e.g., AP 104, AP 202) or as a STA (e.g., STA 114, STA 206), wireless device 502 may also include a tone plane component 524. The tone plane component 524 may be configured to transmit user data, via transmitter 510 or transceiver 514, in a first symbol of a first type of symbol. The first symbol type may have a first symbol duration, a first frequency bandwidth, and a tone foreground. The foreground tone can have a valid first start tone index, a valid first end tone index, and a first set of DC tones. Tone plane component 524 may be configured to transmit an LTF, via transmitter 510 or transceiver 514, on a second symbol of a second symbol type. The second type of symbol can have a second symbol duration, a second frequency bandwidth and a tone background. The background tone can have a valid second start tone index, a valid second end tone index, and a second set of DC tones. In one configuration, tone plane component 524 may be configured to determine the tone foreground associated with the first type of symbol based on configuration information. In this configuration, tone plane component 524 can be configured to determine the tone background associated with the second type of symbol based on configuration information. In another configuration, the second symbol duration may be less than the first symbol duration. In another configuration, the second valid start tone index is a function of the first valid start tone index and the second valid end tone index is a function of the first valid end tone index. In another embodiment, the first set of DC tones can include three DC tones located at tone index -1, 0 and 1, and the second set of DC tones can include one DC tone located at tone index 0. In another embodiment, the first set of DC tones can include eleven DC tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and the second set of DC tones can include three DC tones located at tone indices 1, 0 and 1 or one DC tone located at tone index 0. In another embodiment, the first set of DC tones can include seven tones of DC tones located at tone indices -3, -2, -1, 0, 1, 2, and 3, and the second set of DC tones can include three DC tones located at tone indices -1, 0, and 1 or one tone of DC at tone index 0. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first tone index The first valid starting pitch index can be -122, the first valid ending pitch index can be 122, the second valid starting pitch index can be -31, and the second valid ending pitch index can be 30. In another configuration, the first valid duration of the symbol can be four times as long as the duration of the second symbol, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first valid end tone index can be 250, the second valid start tone index can be -63, and the second valid end tone index can be 62. In another configuration, the first symbol duration can be four times longer than the second symbol duration, first and second frequency bandwidth can be 80 megahertz, first valid start tone index can be -506, first valid end tone index can be 506, second valid start tone index can be - 127 and the second valid final pitch index may be 126. In another configuration, transmitting the LTF on the second symbol may include transmitting the LTF on an overshifted subset of the pitch indices associated with the second symbol and overshifted based on the overshift value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid ending pitch index can be 122, the second valid starting pitch index can be -30, and the second valid ending pitch index can be 31. In this configuration, passing the LTF on the second symbol can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first valid ending pitch index can be 250, the second valid starting pitch index can be -62, and the second valid ending pitch index can be 63. In this configuration, passing the LTF on the second symbol can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 80 megahertz, the first valid start tone index can be -506, the first valid ending pitch index can be 506, the second valid starting pitch index can be -126, and the second valid ending pitch index can be 127. In this configuration, passing the LTF on the second token can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid ending pitch index can be 122, the second valid starting pitch index can be -30, and the second valid ending pitch index can be 30. In another configuration, the first symbol duration can be four times longer than that the duration of the second symbol, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first valid end tone index can be 250, the second valid valid starting tone can be -62 and the second valid ending tone index can be 62. In another configuration, the first symbol duration can be four times longer than the second symbol duration, the first and second symbol bandwidth frequency can be 80 megahertz, the first valid start tone index can be -506, the first valid end tone index can be 506, the second valid start tone index can be -126, and the second end sound index valid value can be 126. In another configuration, the first set of DC tones can include three DC tones located at tone indices -1, 0, and 1, and the second set of DC tones can include three DC tones located at indices -1, 0, and 1. In another embodiment, the first set of CO tones may include eleven CO tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and the second set of DC tones can include five DC tones located at tone indices -2, -1, 0, 1, and 2 or three DC tones located at tone indices -1, 0 and 1. In another embodiment, the first set of CO tones may include seven CO tones located at tone indices -3, -2, -1, 0, 1, 2, and 3, and the second set of CO tones may include five DC tones located at tone indices -2, -1, 0, 1, and 2 or three DC tones located at tone indices -1, 0, and 1. In another configuration, the first symbol duration can be twice as long than the duration of the second symbol, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid end tone index can be 122, the second index The valid start tone index can be -61 and the second valid end sound index can be 61. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first and second bandwidth frequency can be 40 megahertz, the first valid start tone index can be -250, the first valid end tone index can be 250, the second valid start tone index can be -125, and the second sound index valid end can be 125. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first and second frequency bandwidth can be 80 megahertz, the first start tone index The first valid end pitch index can be -506, the second valid starting pitch index can be -253, and the second valid ending pitch index can be 253. In another configuration, the foreground pitch can be based on the tone background. In one aspect, the first symbol duration may be four times greater than the second symbol duration, the first valid start tone index may be equal to the second valid start tone index multiplied by four, and the first valid start tone index valid end tone can be equal to the second valid start tone index multiplied by four. In another aspect, the second set of DC tones can include a DC tone, and the first set of DC tones can include three DG tones located at tone indices -1, 0 and 1. In yet another aspect, the second set of tones DC can include three DC tones, and the first set of DC tones can include seven DG tones located at tone indices -3, -2, -1, 0, 1, 2, and 3. In another configuration, the first bandwidth frequency bandwidth can be 20 megahertz, the first valid starting tone index can be -112, and the first valid ending tone index can be 112. In another configuration, the first frequency bandwidth can be 40 megahertz, the first valid index valid start tone index can be -232 and the first valid end tone index can be 232. In another configuration, the first frequency bandwidth can be 80 megahertz, the first valid start tone index can be -488, and the first valid end tone index can be 488. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first valid start tone index can be equal to the second valid tone index. valid start tone index multiplied by two, and the first valid end tone index can be equal to the second valid start tone index multiplied by two. In another configuration, the second set of DC tones can include three DC tones, and the first set of DC tones can include five DG tones located at tone indices -2, -1, 0, 1 and 2. In another configuration, the second set of DC tones can include three DC tones, and the first set of DC tones can include five DG tones located at tone indices -2, -1, 0, 1 and 2. In another configuration, the second set of DC tones may include five DC tones, and the first set of DC tones may include seven DG tones located at tone indices -3, -2, -1, 0, 1, 2, and 3. In another configuration, the first bandwidth of frequency can be 20 megahertz, the first valid starting tone index can be -116, and the first valid ending tone index can be 116. In another configuration, the first frequency bandwidth can be 40 megahertz and the first valid index valid start tone index can be -244 and the first valid end tone index can be 244. In another configuration, the first frequency bandwidth can be 80 megahertz, the first valid start tone index can be -500 and the first valid final tone index can be 500.

[0103] The various components of the wireless device 502 can be coupled together by a bus system 526. The bus system 526 can include a data bus, for example, as well as a power bus, a control signal bus , and a status signal bus in addition to the data bus. Components of wireless device 502 may be coupled together or accept or provide input to each other using some other mechanism.

[0104] Although a number of separate components are illustrated in FIG. 5, one or more components can be combined or commonly implemented. For example, processor 504 may be used to implement not only the functionality described above with respect to processor 504, but also to implement functionality described above with respect to signal detector 518, DSP 520, user interface 522, and/or or the tone plane component 524. Furthermore, each of the components illustrated in FIG. 5 can be implemented using a plurality of separate elements.

[0105] FIG. 6 is a flowchart of an exemplary wireless communication method 600 using a modified tone plane. Method 600 may be performed using equipment (e.g., AP 104, AP 202, STA 114, STA 206, or wireless device 502, for example). Although method 600 is described below in relation to wireless device elements 502 of FIG. 5, other components may be used to implement one or more of the steps described herein. In FIG. 6, blocks indicated with dotted lines represent optional steps.

[0106] In block 605, the equipment can determine a tone foreground associated with a first type of symbol based on the configuration information, the first duration of the symbol and the first frequency bandwidth. The foreground tone can include a valid first start tone index, a valid first end tone index, and a first set of DC tones. For example, with reference to FIG. 2, the AP 202 can determine a tone foreground for a data symbol based on the configuration information, the first symbol duration, and the first frequency bandwidth. In this example, the AP 202 can choose or be configured to use a 20 MHz symbol (the first frequency) with 4x symbol duration (the first symbol duration) for data symbols. Based on the 20 MHz frequency and 4x symbol duration, the AP 202 can determine which tone plan to use as indicated by the configuration information. For example, configuration information may indicate usable tone rates in [-122: -2] U [2: 122].

[0107] In block 610, the equipment can transmit user data in a first symbol of a first type of symbol. The first symbol type may have a first symbol duration, a first frequency bandwidth, and a tone foreground. For example, with reference to FIG. 2, the AP 202 can transmit user data on the first symbol of the first symbol type which has a symbol duration of 4x, a bandwidth of 20 MHz and the foreground tone with usable tone indices in [-122: -2]U[2:122]. In one aspect, user data may be transmitted in frame 250 within a symbol of data symbols 268.

[0108] In block 615, the equipment can determine a background tone associated with a second type of symbol based on the configuration information. The tone background can include a valid second start tone index, a valid second end tone index, and a second set of DC tones. For example, with reference to FIG. 2, the AP 202 can determine a tone background for an LTF symbol based on the configuration information, the second symbol duration, and the second frequency bandwidth. In this example, the AP 202 can choose or be configured to use a 20 MHz symbol (the second frequency) with a 2x symbol duration (the second symbol duration) for the LTF symbols. Based on the 20 MHz frequency and 2x symbol duration, the AP 202 can determine which tone plan to use as indicated by the configuration information. For example, the configuration information may indicate a usable pitch index [-61:1] U [1:61].

[0109] In block 620, the equipment can transmit an LTF in a second symbol of a second type of symbol. The second type of symbol can have a second symbol duration, a second frequency bandwidth and tone background. For example, with reference to FIG. 2, the AP 202 can transmit the LTF (or part of the LTF) in an LTF symbol of a second symbol type that has a symbol duration of 2x, a bandwidth of 20 MHz, and the background tone with indices of tone usable in [-61:-1] U [1:61].

[0110] Although the above-mentioned examples have been discussed in relation to an AP, an STA can perform similar procedures. For example, the STA 206 may determine a tone foreground based on pre-configured information within the STA 206. In one example, the pre-configured information may indicate that user data is to be transmitted in 20 MHz data symbols (e.g., symbol data rate 268) with a symbol duration of 4x based on a tone plane that has usable tones within a range of [-122 : -2] and [2 : 122]. Preconfigured information may indicate that LTF data should be transmitted on a 20 MHz LTF symbol (for example, LTF symbol 266) with a symbol duration of 1x based on a modified tone plan that has usable tones within a range of [-30 : 1] and [1:30]. The STA 206 can transmit user data and LTF data in data symbols and LTF symbols, respectively, according to preconfigured information.

[0111] In another example, the preconfigured information may indicate that user data should be transmitted in 20 MHz data symbols (for example, data symbol 268) with a symbol duration of 4x based on a tone plane mod that has usable tones within a range of [112 : -2] and [2 : 112]. Preconfigured information may indicate that LTF data should be transmitted on a 20 MHz LTF symbol (for example, LTF symbol 266) with a symbol duration of 1x based on an existing tone plan that has usable tones within a range of [-28 : 1] and [1:28]. The STA 206 can transmit user data and LTF data in data symbols and LTF symbols, respectively, according to preconfigured information.

[0112] In one example, the preconfigured information may indicate that user data should be transmitted in 20 MHz data symbols (for example, data symbol 268) with a symbol duration of 4x based on a tone plane that has usable tones within a range of [-122 : -2] and [2 : 122]. Preconfigured information may indicate that LTF data should be transmitted on a 20 MHz LTF symbol (for example, LTF symbol 266) with a symbol duration of 2x based on a modified tone plan that has usable tones within a range of [-61 : -2] and [2:61]. The STA 206 can transmit user data and LTF data in data symbols and LTF symbols, respectively, according to preconfigured information.

[0113] In another example, the preconfigured information may indicate that user data should be transmitted in 20 MHz data symbols (for example, data symbol 268) with a symbol duration of 4x based on a tone plane mod that has the usable tones within a range of [116 : -3] and [3 : 116]. Preconfigured information may indicate that LTF data should be transmitted on a 20 MHz LTF symbol (for example, LTF symbol 266) with a symbol duration of 2x based on an existing tone plan that has usable tones within a range of [-58 : -2] and [2:58]. The STA 206 can transmit user data and LTF data in data symbols and LTF symbols, respectively, according to preconfigured information.

[0114] FIG. 7 is a functional block diagram of an exemplary wireless communication device 700 using a modified tone plane. The wireless communication device 700 may include a receiver 705, a processing system 710, and a transmitter 715. The processing system 710 may include a tone plane component 724. The processing system 710, the tone plane component 724 and/or transmitter 715 may be configured to transmit user data in a first symbol of a first type of symbol. The first symbol type can have a first symbol duration, a first frequency bandwidth, and a tone foreground, and the tone foreground can include a valid first start tone index, a valid first end tone index and a first set of DC tones. Processing system 710, tone plane component 724 and/or transmitter 715 may be configured to transmit an LTF on a second symbol of a second symbol type. The second symbol type can have a second symbol duration, a second frequency bandwidth, and a tone background, and the tone background can include a valid second start tone index, a valid second end tone index and a second set of DC tones. In one embodiment, processing system 70 and/or tone plane component 724 may be configured to determine the tone foreground associated with the first symbol type based on configuration information. In this configuration, processing system 70 and/or tone plane component 724 can be configured to determine the tone background associated with the second symbol type based on configuration information. In another configuration, the second symbol duration may be less than the first symbol duration. In another configuration, the second valid start tone index is a function of the first valid start tone index and the second valid end tone index is a function of the first valid end tone index. In another embodiment, the first set of DC tones can include three DC tones located at tone index -1, 0 and 1, and the second set of DC tones can include one DC tone located at tone index 0. In another embodiment, the first set of DC tones can include eleven DC tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and the second set of DC tones can include three DC tones located at tone indices -1, 0 and 1 or one DC tone located at tone index 0. In another configuration, the first set of DC tones can include seven tones of DC tones located at tone indices -3, -2, -1, 0, 1, 2 and 3, and the second set of DC tones can include three DC tones located at tone indices -1, 0 and 1 or one DC tone at tone index 0. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid end tone index can be 122, the second valid start tone index can be -31, and the second valid end tone index can be 30. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first end tone index valid second tone index can be 250, second valid start tone index can be -63, and second valid final tone index can be 62. In another configuration, the first symbol duration can be four times longer than the second symbol duration , the first and second frequency bandwidth can be 80 megahertz, the first valid start tone index can be -506, the first valid end tone index can be 506, the second valid start tone index can be -127 and the second valid final pitch index can be 126. In another configuration, transmitting the LTF in the second symbol can include transmitting the LTF in an overshifted subset of the pitch indices associated with the second symbol and overshifted based on the overshift value . In another embodiment, transmitting the LTF in the second symbol can include the LTF information on all tone indices at and between the second valid start tone index and the second valid end tone index, including any tone indices corresponding to the DC tones. , and transmit the LTF in an overshifted subset of the pitch indices with the second symbol and overshifted based on the overshift value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid ending pitch index can be 122, the second valid starting pitch index can be -30, and the second valid ending pitch index can be 31. In this configuration, passing the LTF on the second symbol can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first valid ending pitch index can be 250, the second valid starting pitch index can be -62, and the second valid ending pitch index can be 63. In this configuration, passing the LTF on the second symbol can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 80 megahertz, the first valid start tone index can be -506, the first valid ending pitch index can be 506, the second valid starting pitch index can be -126, and the second valid ending pitch index can be 127. In this configuration, passing the LTF on the second token can include passing the LTF on a subset of the pitch indices associated with the second symbol and subset based on the suboffset value. In another configuration, the first symbol duration can be four times as long as the second symbol duration, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid ending pitch index can be 122, the second valid starting pitch index can be -30, and the second valid ending pitch index can be 30. In another configuration, the first symbol duration can be four times longer than that the duration of the second symbol, the first and second frequency bandwidth can be 40 megahertz, the first valid start tone index can be -250, the first valid end tone index can be 250, the second valid valid starting tone can be -62 and the second valid ending tone index can be 62. In another configuration, the first symbol duration can be four times longer than the second symbol duration, the first and second symbol bandwidth frequency can be 80 megahertz, the first valid start tone index can be -506, the first valid end tone index can be 506, the second valid start tone index can be -126, and the second end sound index valid value can be 126. In another configuration, the first set of DC tones can include three DC tones located at tone indices -1, 0, and 1, and the second set of DC tones can include three DC tones located at indices -1, 0, and 1. In another embodiment, the first set of CO tones may include eleven CO tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and the second set of DC tones can include five DC tones located at tone indices -2, -1, 0, 1, and 2 or three DC tones located at tone indices -1, 0 and 1. In another embodiment, the first set of CO tones may include seven CO tones located at tone indices -3, -2, -1, 0, 1, 2, and 3, and the second set of CO tones may include five DC tones located at tone indices -2, -1, 0, 1, and 2 or three DC tones located at tone indices -1, 0, and 1. In another configuration, the first symbol duration can be twice as long than the duration of the second symbol, the first and second frequency bandwidth can be 20 megahertz, the first valid start tone index can be -122, the first valid end tone index can be 122, the second index The valid start tone index can be -61 and the second valid end sound index can be 61. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first and second bandwidth frequency can be 40 megahertz, the first valid start tone index can be -250, the first valid end tone index can be 250, the second valid start tone index can be -125, and the second sound index valid end can be 125. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first and second frequency bandwidth can be 80 megahertz, the first start tone index The first valid end pitch index can be -506, the second valid starting pitch index can be -253, and the second valid ending pitch index can be 253. In another configuration, the foreground pitch can be based on the tone background. In one aspect, the first symbol duration may be four times greater than the second symbol duration, the first valid start tone index may be equal to the second valid start tone index multiplied by four, and the first valid start tone index valid end tone can be equal to the second valid start tone index multiplied by four. In another aspect, the second set of DC tones can include a DC tone, and the first set of DC tones can include three DG tones located at tone indices -1, 0 and 1. In yet another aspect, the second set of tones DC can include three DC tones, and the first set of DC tones can include seven DG tones located at tone indices -3, -2, -1, 0, 1, 2, and 3. In another configuration, the first bandwidth frequency bandwidth can be 20 megahertz, the first valid starting tone index can be -112, and the first valid ending tone index can be 112. In another configuration, the first frequency bandwidth can be 40 megahertz, the first valid index valid start tone index can be -232 and the first valid end tone index can be 232. In yet another configuration, the first frequency bandwidth can be 80 megahertz, the first valid start tone index can be -488 and the first valid end tone index can be 488. In another configuration, the first symbol duration can be twice as long as the second symbol duration, the first valid start tone index can be equal to the second tone index valid start tone index multiplied by two, and the first valid end tone index can be equal to the second valid start tone index multiplied by two. In another configuration, the second set of DC tones can include three DC tones, and the first set of DC tones can include five DG tones located at tone indices -2, -1, 0, 1 and 2. In another configuration, the second set of DC tones can include three DC tones, and the first set of DC tones can include five DG tones located at tone indices -2, -1, 0, 1 and 2. In another configuration, the second set of DC tones may include five DC tones, and the first set of DC tones may include seven DG tones located at tone indices -3, -2, -1, 0, 1, 2, and 3. In another configuration, the first bandwidth of frequency can be 20 megahertz, the first valid starting tone index can be -116, and the first valid ending tone index can be 116. In another configuration, the first frequency bandwidth can be 40 megahertz and the first valid index valid start tone index can be -244 and the first valid end tone index can be 244. In another configuration, the first frequency bandwidth can be 80 megahertz, the first valid start tone index can be -500 and the first valid final tone index can be 500.

[0115] The receiver 705, the processing system 710, the tone plane component 724 and/or the transmitter 715 can be configured to perform one or more functions discussed above in relation to blocks 605, 610, 615 and 620 of FIG. . 6. Receiver 705 may correspond to receiver 512. Processing system 710 may correspond to processor 504. Transmitter 715 may correspond to transmitter 510. Tone plane component 724 may correspond to sound plane component 124 and/or to the 524 tone plane component.

[0116] Furthermore, means for transmitting user data in a first symbol of a first type of symbol may comprise the processing system 710, the tone plane component 724 and/or the transmitter 715. Means for transmitting an LTF in a second symbol of a second type of symbol may comprise the processing system 710, the pitch plane component 724 and/or the transmitter 715. Means for determining the pitch foreground may comprise the processing system 710 and/or the sound plane component 724. Means for determining the tone background may comprise processing system 710 and/or sound plane component 724.

[0117] The various operations of the methods described above can be performed by any suitable means capable of performing the operations, such as various hardware devices and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures can be performed by functional means capable of performing the corresponding operations.

[0118] The various logic blocks, components and illustrative circuits described in connection with the present disclosure can be implemented or executed with a general purpose processor, a DSP, an application specific integrated circuit (ASIC), an FPGA or other PLD, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but alternatively the processor may be any commercially available processor, controller, microcontroller or state machine. A processor can also be implemented as a combination of computing devices, for example a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors together with a DSP core, or any other type of configuration.

[0119] In one or more exemplary aspects, the described functions can be implemented in hardware, software, firmware or any combination thereof. If implemented in software, functions may be stored in or transmitted via one or more instructions or code on computer-readable media. Computer-readable media include computer storage media and communication media, including any medium that facilitates the transfer of a computer program from one place to another. A storage medium can be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, compact disk (CD)-ROM (CD-ROM) or other optical disk storage, magnetic disk storage, or other storage devices. magnetic storage, or any other medium that can be used to transport or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly called a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source over coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, so coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. Disk and floppy disk as used herein include CD, laser disk, optical disk, digital versatile disk (DVD), floppy disk and Blu-ray disk where floppy disks generally reproduce data magnetically, while disks reproduce data optically with lasers. Accordingly, computer-readable media comprises non-transient computer-readable media (eg, tangible media).

[0120] The methods disclosed herein comprise one or more steps or actions for carrying out the described method. The steps and/or actions of the method can be interchanged with each other without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of the specific steps and/or actions can be modified without departing from the scope of the claims.

[0121] Thus, certain aspects may comprise a computer program product to perform the operations presented herein. For example, such a computer program product may comprise computer-readable media having instructions stored (and/or encoded) therein, the instructions being executable by one or more processors to perform the operations described herein. For some aspects, the computer program product may include packaging material.

[0122] Furthermore, it should be noted that components and/or other means suitable for carrying out the methods and techniques described herein may be downloaded and/or otherwise obtained by a user terminal and/or base station, as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for carrying out the methods described herein. Alternatively, various methods described herein can be provided via storage media (e.g. RAM, ROM, a physical storage medium such as a CD or floppy disk, etc.), such that a user terminal and/or workstation base can obtain the various methods by coupling or providing storage media to the device. In addition, any other suitable technique for delivering the methods and techniques described herein to a device may be used.

[0123] It should be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, alterations, and variations can be made in the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

[0124] Although the foregoing is directed to aspects of the present disclosure, other and additional aspects of the disclosure can be conceived without departing from the basic scope thereof, and its scope is determined by the following claims.

[0125] The foregoing description is provided to enable anyone skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown here, but must be within the full scope consistent with the claims of the language, reference to an element in the singular not intended to mean "one and only one" unless which is specifically so stated, but rather "one or more". Unless specifically noted otherwise, the term "some" refers to one or more. All structural and functional equivalents to elements of the various aspects described throughout this disclosure, which are known or later will be known to those skilled in the art, are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public regardless of whether that disclosure is expressly recited in the claims. No element of the claim shall be construed under the provisions of 35 USC § 12(f) unless the element is expressly recited using the phrase “means to,” or, in the case of a method claim, the element is recited using the phrase "step to".

Claims (15)

1. Method (600) performed by a wireless device, characterized in that it comprises: transmitting (610) user data in a first symbol of a first type of symbol, wherein the first type of symbol has a first duration of symbol, a first frequency bandwidth, and a tone foreground, and the tone foreground comprising a first valid start tone index, a first valid end tone index, and a first set of dc tones, A.D; and transmitting (620) a long training field, LTF, in a second symbol of a second symbol type, wherein the second symbol type has a second symbol duration, a second frequency bandwidth, and a background of tone, and the background tone comprises a second valid start tone index, a second valid end tone index, and a second set of DC tones, wherein a valid tone is a usable tone for transmission by the wireless device excluding guard tones and DC tones, and where the foreground tone is different from the background tone. 2. Method according to claim 1, characterized in that the second symbol duration is less than the first symbol duration. 3. Method according to claim 1, characterized in that the second valid start tone index is a function of the first valid start tone index, and the second valid end tone index is a function of the first index valid final tone. 4. Method according to claim 1, characterized in that the first set of DC tones includes three DC tones located at tone indices -1, 0, and 1, and in which the second set of DC tones includes a DC tone located at tone index 0. 5. Method according to claim 1, characterized in that the first set of DC tones includes eleven DC tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and wherein the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1 or one DC tone located at tone index 0. 6. Method, according to claim 1, characterized in that the first set of DC tones includes seven DC tones located at tone indices -3, -2, -1, 0, 1, 2, and 3, and wherein the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1 or one DC tone at tone index 0. 7. Method according to claim 1, characterized in that the first set of DC tones includes three DC tones located at tone indices -1, 0, and 1, and in which the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1. 8. Computer-readable memory characterized by the fact that it comprises instructions stored therein, the instructions being executed by a computer to carry out a method as defined in any one of claims 1 to 7. 9. Apparatus (700) for wireless communication, characterized in that it comprises: means (715) for transmitting user data in a first symbol of a first type of symbol, wherein the first type of symbol has a first duration of symbol, a first frequency bandwidth, and a tone foreground, and the tone foreground comprising a first valid start tone index, a first valid end tone index, and a first set of dc tones , DC; and means (715) for transmitting a long training field, LTF, in a second symbol of a second symbol type, wherein the second symbol type has a second symbol duration, a second frequency bandwidth, and a second tone plane, and the second tone plane comprises a second valid start tone index, a second valid end tone index, and a second set of DC tones, wherein a valid tone is a tone usable for transmission by the device wireless excluding guard tones and DC tones, and where the foreground tone is different from the background tone. 10. Apparatus according to claim 9, characterized in that the second symbol duration is less than the first symbol duration. 11. Apparatus according to claim 9, characterized in that the second valid start tone index is a function of the first valid start tone index, and the second valid final tone index is a function of the first index valid final tone. 12. Apparatus according to claim 9, characterized in that the first set of DC tones includes three DC tones located at tone indices -1, 0, and 1, and in which the second set of DC tones includes a DC tone located at tone index 0. 13. Apparatus according to claim 9, characterized in that the first set of DC tones includes eleven DC tones located at tone indices -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, and 5, and wherein the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1 or one DC tone located at tone index 0. 14. Apparatus according to claim 9, characterized in that the first set of DC tones includes seven DC tones located at tone indices -3, -2, -1, 0, 1, 2, and 3 and at that the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1 or one DC tone at tone index 0. 15. Apparatus according to claim 9, characterized in that the first set of DC tones includes three DC tones located at tone indices -1, 0, and 1, and in which the second set of DC tones includes three DC tones located at tone indices -1, 0, and 1.