WO2018231737A1

WO2018231737A1 - Enhanced sounding sequences for secure wireless communications

Info

Publication number: WO2018231737A1
Application number: PCT/US2018/036978
Authority: WO
Inventors: Qinghua Li; Feng Jiang; Xintian E. Lin; Xiaogang Chen; Jonathan Segev; Robert Stacey
Original assignee: Intel Corporation
Priority date: 2017-06-12
Filing date: 2018-06-11
Publication date: 2018-12-20

Abstract

This disclosure describes systems, methods, and devices related to enhanced sounding signals for device ranging operations. A device may determine a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence The device may determine a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence. The device may apply a first phase rotation to the second combined Golay sequence. The device may allocate the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain. The device may send the first NDP.

Description

ENHANCED SOUNDING SEQUENCES FOR SECURE WIRELESS

COMMUNICATIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U. S. Provisional Application No. 62/518,413, filed June 12, 2017, the disclosure of which is incorporated by reference as if set forth in full.

TECHNICAL FIELD

[0002] This disclosure generally relates to systems and methods for wireless communications and, more particularly, to sounding signal sequences for secure wireless communications.

BACKGROUND

[0003] Wireless devices are becoming widely prevalent and are increasingly requesting device positioning information. Communications used to determine device positioning may be vulnerable to security breaches.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a network diagram illustrating an example network environment, in accordance with one or more example embodiments of the present disclosure.

[0005] FIG. 2 depicts illustrative sounding signal symbols, in accordance with one or more example embodiments of the present disclosure.

[0006] FIG. 3A depicts an enhanced sounding sequence, in accordance with one or more example embodiments of the present disclosure.

[0007] FIG. 3B depicts an enhanced sounding sequence, in accordance with one or more example embodiments of the present disclosure.

[0008] FIG. 4 depicts allocating an enhanced sounding sequence to subcarriers, in accordance with one or more example embodiments of the present disclosure.

[0009] FIG. 5A depicts an enhanced peak-to-average power ratio (PAPR) performance evaluation of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0010] FIG. 5B depicts an enhanced PAPR performance evaluation of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[001 1] FIG. 5C depicts an enhanced PAPR performance evaluation of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0012] FIG. 6A illustrates a flow diagram of illustrative process for enhanced sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0013] FIG. 6B illustrates a flow diagram of illustrative process for enhanced sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0014] FIG. 7 illustrates a functional diagram of an exemplary communication station that may be suitable for use as a user device, in accordance with one or more example embodiments of the present disclosure.

[0015] FIG. 8 illustrates a block diagram of an example machine upon which any of one or more techniques (e.g., methods) may be performed, in accordance with one or more example embodiments of the present disclosure. DETAILED DESCRIPTION

[0016] Example embodiments described herein provide certain systems, methods, and devices for enhanced sounding signal sequences for secure wireless communications. The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, algorithm, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0017] In wireless communications, devices may use a variety of methods to determine a device's location/position. For example, devices may exchange data transmissions using a null data packet (NDP) with sequences of symbols. A portion of an NDP frame may include one or more sounding symbols. Each sounding symbol may have a set of subcarriers (e.g., tones) having non-zero energy, and some guard subcarriers such as direct current (DC) subcarriers and edge subcarriers. Based on the symbols in a sounding signal, devices may perform location measurements to determine device locations. However, such sounding signals may be subject to security and privacy vulnerabilities. For example, an attacking device may replicate sounding signals to cause device ranging determinations to be inaccurate, thereby causing devices to take actions which may allow an attack, such as unlocking a screen or device.

[0018] In wireless communications standards such as IEEE 802.1 laz, security and privacy precautions are provided for ranging measurements of wireless devices at both the physical (PHY) and medium access control (MAC) levels of a device. On the PHY level, techniques such as random cyclic shift diversity (CSD) and a random long training field (LTF) sounding sequence may provide security and privacy in communication sequences used to determine a device's location. A random CSD may refer to a transmitting device applying a time delay to transmitted signals, where the delay can be cyclic or linear. A random LTF sounding sequence may refer to using the LTF of a sounding signal to transmit a sequence of signals used to determine device location. Using a random LTF sounding sequence may allow a system to not only detect an adversary attack, but also suppress the attack. However, using a random LTF sounding sequence may increase the peak-to-average power ratio (PAPR) of a sounding signal and therefore reduce the range or quality of ranging signals. For example, higher PAPR may result in portions of a signal being clipped, allowing distortion and reducing the accuracy of ranging operations using sounding signals. When signals are converted from a frequency domain to a time domain, a Gaussian distribution may be a result. To increase the number of sequences which may be used for sounding signals, simply reversing the sign polarity (e.g., from +1 to -1) of each symbol in a sequence may result in high PAPR. Therefore, a Golay sequence may be used instead of a Gaussian representation of sounding signals.

[0019] It is desirable to have many sounding signal sequences to choose from in order to minimize the chance of an attacking device selecting the right sounding sequence to execute an attack, but it is challenging to generate many sounding sequences with low PAPRs. In addition, because a random sounding signal may replace an existing sounding signal (e.g., an LTF symbol) to provide security enhancements, a hardware change for a device may be required (e.g., from hardware designed to use IEEE 802.1 lmc communications). Therefore, it may be beneficial to use random CSD for IEEE 802.1 lmc ranging operations, and to use a random sounding symbol for IEEE 802.11 az ranging operations (e.g., to improve upon IEEE 802.11 ax operations). It also may be possible to replace very high throughput (VHT) LTF symbols in IEEE 802.1 lmc with a random sounding symbol as defined herein.

[0020] For device security, it may be preferable to have many sequences (e.g., hundreds) from which a transmitter may choose so that an adversary is less likely to know which sequence is used in the sounding. In addition to low PAPR, it may be preferable to generate the sequences in a parametric fashion such that only the generating parameters, instead of the long sequence itself, are exchanged between a transmitter and receiver. Low complexities may be preferable for generating the sequence so that a transceiver does not need to store hundreds of sequences. Also, it may be beneficial to enhance sounding signal sequences using a number of LTF sounding sequences whose PAPRs are about the same as or even lower than the IEEE 802.1 l ax LTF sounding sequences. It may be desirable for the generation of the sequences to be of an extremely low complexity.

[0021] Example embodiments of the present disclosure relate to systems, methods, and devices for enhanced sounding sequences for secure wireless communications. [0022] In one or more embodiments, a family of LTF sounding sequences may be used in enhanced sounding signal operations. The LTF sounding sequences may have PAPRs the same or lower than IEEE 802.1 lax LTF sounding sequences, and the generation of the LTF sounding sequences may be of low complexity.

[0023] In one or more embodiments, an LTF sounding sequence of an 80 MHz channel may have 250 bits, each having a value of +1 or -1. If each bit were allowed to randomly flip, some of the sequences using the bits would have high PAPRs. To reduce PAPR, a subset of the number of sequences may be selected. For ease of implementation, a systematic way of generating low PAPR sequences may require only eight operations, each of which may include one copy-paste and one sign flip. The enhanced generation may use the complementary structure of Golay sequences, and this structure ensures a low PAPR. Golay pairs include two binary sequences of a same length L, and whose auto-correlation functions have equal magnitude but opposite signs. The sum of the auto-correlation functions of the two binary sequences results in an auto-correlation function with a peak value of 2L.

[0024] In one or more embodiments, an NDP may be used as a sounding signal. Subcarriers of the NDP sounding signal which have non-zero energy may be modulated by a sequence of symbols. For ease of implementation and to maintain low PAPR, the symbols may be binary in phase (e.g., 0 degree and 180 degree represented as +1 and -1). In one or more embodiments, the symbols may have a higher modulation order than binary phase shift keying (BPSK). Instead of rotating the phase by 180 degrees as in BPSK, a finer phase rotation like quadrature phase shift keying (QPSK) or eight phase shift keying (8PSK) may be used for having more random sequences. In 802.1 l a/g/n/ac, the sequence of symbols may be optimized and specified for channel sounding and training. Therefore, there may be only one sequence with a low PAPR for each channel bandwidth and each LTF duration. For enhanced protection of the security and privacy of the ranging user, random CSD and/or a random sounding symbol may be implemented for sounding operations.

[0025] In one or more embodiments, complementary pairs of Golay sequences may have low PAPRs. Therefore, enhanced sounding signal operations may include generating complementary Golay sequence pairs and fitting each pair into the non-zero energy subcarriers of an NDP. Complementary Golay pairs may be generated using concatenation, interleaving, and/or reversion. Using Golay pair transformations with concatenation, interleaving, and/or reversion, 2^K+1 complementary pairs of Golay sequences may be generated, in which the length of each sequence is 2^K_1. The generation may use K iterations. After each iteration, both the length of the sequence and the number of sequences may be doubled. The K iterations above may generate 2^K complementary pairs. The sequences generated by concatenating the two sequences of each pair are orthogonal, which is desirable for mitigating an adversary attack. For an 80 MHz channel, for example, there may be 250 non-zero energy subcarriers for lx duration sounding. Using eight iterations, 256 complementary pairs may be generated. For increased security, more pairs may be desirable. The number of pairs may be doubled by interleaving and order reversing.

[0026] In one or more embodiments, using interleaving and reversing, 2^K complementary pairs of length 2^K_1 sequences may be generated. These pairs may be different from those generated by concatenation. In total, 2^K+1 complementary pairs of length 2^K_1 sequences may be generated. Over an encrypted channel, a transmitter and receiver may exchange the indication or index of the sign flips, the indication or index of interleaving, and the indication or index of the reversing so that the transmitter and receiver may generate the same sounding symbol.

[0027] In one or more embodiments, because the length of generated sequences is of the power of two, it may be beneficial to puncture out some symbols in the generated sequences to fit the punctured sequences into the non-zero energy subcarriers (e.g., of an NDP frame), whose number is not a power of two. There are multiple ways to do this, and because puncturing usually increases PAPR, it may be beneficial to use a puncturing method that has low PAPR.

[0028] In one or more embodiments, a transmitter device and a receiver device using enhanced sounding signals may agree upon a waveform and various parameters (e.g., symbols, timing, cyclic shift, etc.) used in the communication of sounding signals. This way, the devices may determine based on the information associated with sounding signals (e.g., timing information) whether received signals are from an expected device or from an attacking device. For example, the number of signals used in a sounding sequence for ranging operations may be pre-set and communicated between the devices.

[0029] Advantages of enhanced sounding signal sequences for secure wireless communications include suppression to adversary attacks and low PAPR sequences ensuring ranging operation accuracy for long distances. The PAPRs of the enhanced sequences may be the same as or even lower than the PAPRs of the LTFs of the IEEE 802.1 lax sequences. In addition, the enhanced sequences may be dynamically generated with extremely low complexity so that no storage memory is needed for storing hundreds of sequences.

[0030] Numerous other examples, configurations, processes, algorithms, etc., may exist, some of which are described in greater detail below. Example embodiments will now be described with reference to the accompanying figures. [0031] FIG. 1 is a network diagram illustrating an example network environment, according to some example embodiments of the present disclosure. Wireless network 100 may include one or more user devices 120 and one or more access points(s) (AP) 102, which may communicate in accordance with IEEE 802.11 communication standards. The user device(s) 120 may be mobile devices that are non-stationary (e.g., not having fixed locations) or may be stationary devices.

[0032] In some embodiments, the user devices 120 and the AP 102 may include one or more computer systems similar to that of the functional diagram of FIG. 7 and/or the example machine/system of FIG. 8.

[0033] One or more illustrative user device(s) 120 and/or AP(s) 102 may be operable by one or more user(s) 110. It should be noted that any addressable unit may be a station (STA). An STA may take on multiple distinct characteristics, each of which shape its function. For example, a single addressable unit might simultaneously be a portable STA, a quality-of- service (QoS) STA, a dependent STA, and a hidden STA. The one or more illustrative user device(s) 120 and the AP(s) 102 may be STAs. The one or more illustrative user device(s) 120 and/or AP(s) 102 may operate as a personal basic service set (PBSS) control point/access point (PCP/AP). The user device(s) 120 (e.g., 124, 126, or 128) and/or AP(s) 102 may include any suitable processor-driven device including, but not limited to, a mobile device or a non-mobile, e.g., a static, device. For example, user device(s) 120 and/or AP(s) 102 may include, a user equipment (UE), a station (STA), an access point (AP), a software enabled AP (SoftAP), a personal computer (PC), a wearable wireless device (e.g., bracelet, watch, glasses, ring, etc.), a desktop computer, a mobile computer, a laptop computer, an ultrabook™ computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, an internet of things (IoT) device, a sensor device, a PDA device, a handheld PDA device, an on-board device, an off-board device, a hybrid device (e.g., combining cellular phone functionalities with PDA device functionalities), a consumer device, a vehicular device, a non-vehicular device, a mobile or portable device, a non-mobile or non-portable device, a mobile phone, a cellular telephone, a PCS device, a PDA device which incorporates a wireless communication device, a mobile or portable GPS device, a DVB device, a relatively small computing device, a non-desktop computer, a "carry small live large" (CSLL) device, an ultra mobile device (UMD), an ultra mobile PC (UMPC), a mobile internet device (MID), an "origami" device or computing device, a device that supports dynamically composable computing (DCC), a context-aware device, a video device, an audio device, an A/V device, a set-top-box (STB), a blu-ray disc (BD) player, a BD recorder, a digital video disc (DVD) player, a high definition (HD) DVD player, a DVD recorder, a HD DVD recorder, a personal video recorder (PVR), a broadcast HD receiver, a video source, an audio source, a video sink, an audio sink, a stereo tuner, a broadcast radio receiver, a flat panel display, a personal media player (PMP), a digital video camera (DVC), a digital audio player, a speaker, an audio receiver, an audio amplifier, a gaming device, a data source, a data sink, a digital still camera (DSC), a media player, a smartphone, a television, a music player, or the like. Other devices, including smart devices such as lamps, climate control, car components, household components, appliances, etc. may also be included in this list.

[0034] As used herein, the term "Internet of Things (IoT) device" is used to refer to any obj ect (e.g., an appliance, a sensor, etc.) that has an addressable interface (e.g., an Internet protocol (IP) address, a Bluetooth identifier (ID), a near-field communication (NFC) ID, etc.) and can transmit information to one or more other devices over a wired or wireless connection. An IoT device may have a passive communication interface, such as a quick response (QR) code, a radio-frequency identification (RFID) tag, an NFC tag, or the like, or an active communication interface, such as a modem, a transceiver, a transmitter-receiver, or the like. An IoT device can have a particular set of attributes (e.g., a device state or status, such as whether the IoT device is on or off, open or closed, idle or active, available for task execution or busy, and so on, a cooling or heating function, an environmental monitoring or recording function, a light-emitting function, a sound-emitting function, etc.) that can be embedded in and/or controlled/monitored by a central processing unit (CPU), microprocessor, ASIC, or the like, and configured for connection to an IoT network such as a local ad-hoc network or the Internet. For example, IoT devices may include, but are not limited to, refrigerators, toasters, ovens, microwaves, freezers, dishwashers, dishes, hand tools, clothes washers, clothes dryers, furnaces, air conditioners, thermostats, televisions, light fixtures, vacuum cleaners, sprinklers, electricity meters, gas meters, etc., so long as the devices are equipped with an addressable communications interface for communicating with the IoT network. IoT devices may also include cell phones, desktop computers, laptop computers, tablet computers, personal digital assistants (PDAs), etc. Accordingly, the IoT network may be comprised of a combination of "legacy" Internet-accessible devices (e.g., laptop or desktop computers, cell phones, etc.) in addition to devices that do not typically have Internet-connectivity (e.g., dishwashers, etc.).

[0035] The user device(s) 120 and/or AP(s) 102 may also include mesh stations in, for example, a mesh network, in accordance with one or more IEEE 802.11 standards and/or 3GPP standards. [0036] Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to communicate with each other via one or more communications networks 130 and/or 135 wirelessly or wired. The user device(s) 120 may also communicate peer-to-peer or directly with each other with or without the AP(s) 102. Any of the communications networks 130 and/or 135 may include, but not limited to, any one of a combination of different types of suitable communications networks such as, for example, broadcasting networks, cable networks, public networks (e.g., the Internet), private networks, wireless networks, cellular networks, or any other suitable private and/or public networks. Further, any of the communications networks 130 and/or 135 may have any suitable communication range associated therewith and may include, for example, global networks (e.g., the Internet), metropolitan area networks (MANs), wide area networks (WANs), local area networks (LANs), or personal area networks (PANs). In addition, any of the communications networks 130 and/or 135 may include any type of medium over which network traffic may be carried including, but not limited to, coaxial cable, twisted-pair wire, optical fiber, a hybrid fiber coaxial (HFC) medium, microwave terrestrial transceivers, radio frequency communication mediums, white space communication mediums, ultra-high frequency communication mediums, satellite communication mediums, or any combination thereof.

[0037] Any of the user device(s) 120 (e.g., user devices 124, 126, 128) and AP(s) 102 may include one or more communications antennas. The one or more communications antennas may be any suitable type of antennas corresponding to the communications protocols used by the user device(s) 120 (e.g., user devices 124, 126 and 128), and AP(s) 102. Some non-limiting examples of suitable communications antennas include Wi-Fi antennas, Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards compatible antennas, directional antennas, non-directional antennas, dipole antennas, folded dipole antennas, patch antennas, multiple-input multiple-output (MIMO) antennas, omnidirectional antennas, quasi- omnidirectional antennas, or the like. The one or more communications antennas may be communicatively coupled to a radio component to transmit and/or receive signals, such as communications signals to and/or from the user devices 120 and/or AP(s) 102.

[0038] Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform directional transmission and/or directional reception in conjunction with wirelessly communicating in a wireless network. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform such directional transmission and/or reception using a set of multiple antenna arrays (e.g., DMG antenna arrays or the like). Each of the multiple antenna arrays may be used for transmission and/or reception in a particular respective direction or range of directions. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform any given directional transmission towards one or more defined transmit sectors. Any of the user device(s) 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may be configured to perform any given directional reception from one or more defined receive sectors.

[0039] MIMO beamforming in a wireless network may be accomplished using RF beamforming and/or digital beamforming. In some embodiments, in performing a given MIMO transmission, user devices 120 and/or AP(s) 102 may be configured to use all or a subset of its one or more communications antennas to perform MIMO beamforming.

[0040] Any of the user devices 120 (e.g., user devices 124, 126, 128), and AP(s) 102 may include any suitable radio and/or transceiver for transmitting and/or receiving radio frequency (RF) signals in the bandwidth and/or channels corresponding to the communications protocols utilized by any of the user device(s) 120 and AP(s) 102 to communicate with each other. The radio components may include hardware and/or software to modulate and/or demodulate communications signals according to pre-established transmission protocols. The radio components may further have hardware and/or software instructions to communicate via one or more Wi-Fi and/or Wi-Fi direct protocols, as standardized by the Institute of Electrical and Electronics Engineers (IEEE) 802.1 1 standards. In certain example embodiments, the radio component, in cooperation with the communications antennas, may be configured to communicate via 2.4 GHz channels (e.g., 802.1 1b, 802. l lg, 802.1 1η, 802.1 l ax), 5 GHz channels (e.g., 802.1 1η, 802.1 l ac, 802.1 l ax), or 60 GHZ channels (e.g., 802.1 lad, 802. Hay). In some embodiments, non-Wi-Fi protocols may be used for communications between devices, such as Bluetooth, dedicated short-range communication (DSRC), Ultra-High Frequency (UHF) (e.g., IEEE 802.1 laf, IEEE 802.22), white band frequency (e.g., white spaces), or other packetized radio communications. The radio component may include any known receiver and baseband suitable for communicating via the communications protocols. The radio component may further include a low noise amplifier (LNA), additional signal amplifiers, an analog-to- digital (A/D) converter, one or more buffers, and digital baseband.

[0041] In one or more embodiments, AP 102 and user devices 120 may exchange one or more sounding signals (e.g., NDP sounding signal 140). The sounding signals may be used for ranging operations to determine device locations. The sounding signals may be defined as explained further herein.

[0042] FIG. 2 depicts illustrative sounding signal symbols 200, in accordance with one or more example embodiments of the present disclosure. [0043] Referring to FIG. 2, an NDP sounding signal 202 may be sent by a device (e.g., AP 102 or user device 120 of FIG. 1). NDP sounding signal 202 may be sent as part of a ranging operation between devices. A portion 204 of NDP sounding signal 202 may include one or more sounding symbols used for a ranging operation, and each sounding symbol may have one or more sequences of sounding symbols. For example, the portion 204 of NDP sounding signal 202 may include sounding symbols, each having two sequences (e.g., sequence 206, sequence 208). Sequence 206 and sequence 208 may form one sounding symbol of the portion 204, and portion 204 may have multiple sounding symbols. NDP sounding signal 202 may be sent in the time domain, and the sounding symbols may map (e.g., be allocated) to the frequency domain. Sequence 206 and sequence 208 may be different from one another, and may include subcarriers mapped/allocated from the NDP sounding signal 202, and may include subcarriers with non-zero energy (e.g., a +1 or -1 value). Each sounding symbol has a set of subcarriers with non-zero energy. In the frequency domain, some subcarriers with zero energy may be reserved. For example, edge subcarriers 210, DC subcarriers 212, and edge subcarriers 212 (e.g., guard subcarriers) may be zero energy subcarriers to which sounding symbols of NDP frame 202 are not mapped/allocated. This way, sequence 206 and sequence 208 may include subcarriers in the frequency domain with edge subcarriers 210, DC subcarriers, and edge subcarriers 212 that all have zero energy.

[0044] In one or more embodiments, the subcarriers with non-zero energy (e.g., subcarriers other than edge subcarriers 210, DC subcarriers 212, and edge subcarriers 214) may be modulated by a sequence of symbols. For the ease of implementation and for low PAPR, the symbols with non-zero energy may be binary in phase (e.g., +1 and -1). In one or more embodiments, the symbols may have a higher modulation order than BPSK. Instead of rotating the phase by 180 degrees as in BPSK, a finer phase rotation like QPSK or 8PSK may be used for generating more random sequences. In the IEEE 802.1 la/g/n/ac standards, the sequence of symbols of NDP frame 202 maybe optimized for channel sounding and training. Therefore, there is only one sequence with a low PAPR for each channel bandwidth and each LTF duration. In IEEE 802.11 az, however, enhancement may improve protection security and privacy of a ranging user device. A random CSD and/or random sounding symbol may be used to enhance a sounding signal sequence. Because random sounding signal may replace an existing sounding symbol (e.g., an LTF symbol), hardware change may be required, although it may be undesirable to change the existing IEEE 802.11mc hardware of wireless devices. Therefore random CSD may be used for IEEE 802.1 lmc ranging operations, and random sounding symbols (e.g., sequence 206 and sequence 208) may be used for IEEE 802.1 1az to enhance ranging operations of the IEEE 802.1 lax standard. In addition, random sounding symbols may replace VHT-LTF symbols defined in IEEE 802.11mc.

[0045] For enhanced security, it may be beneficial to have a significant number (e.g., hundreds) of sounding signal sequences from which a transmitting device may select sounding signal sequences (e.g., sequence 206 and sequence 208) for ranging operations. Having a large number of possible sounding signal sequences may make it more difficult for an adversary device to determine and replicate the sequence selected in a sounding operation. In addition to low PAPR, it may be preferable to generate sounding signal sequences in a parametric fashion so that only the generating parameters, instead of the long sequence itself, may be exchanged between a transmitter and receiver. Low complexities are preferred for generating the sequence so that a transceiver may not need to store hundreds of sequences.

[0046] In one or more embodiments, complementary pairs of Golay sequences may have low PAPRs (e.g., lower than Gaussian distributions). Therefore, Golay sequence pairs may be generated and fit (e.g., mapped/allocated) into the non-zero energy subcarriers (e.g., sequence 206 and sequence 208). Complementary Golay pairs may be generated using concatenation, interleaving, and reversion of signals.

[0047] In one or more embodiments, let (a, b) be a pair of complementary Golay sequences. For example, sequence a and sequence b may be symmetric in the pair (a, b). Thus, (a, b) and (b, a) may be treated as the same pair before being mapped/allocated to the non-zero energy subcarriers. Pairs (a, b) and (b, a) may be mapped/allocated differently to the non-zero energy subcarriers, and the different mappings/allocations may generate different sounding symbols (e.g., sequence 206 and sequence 208). To generate additional complementary Golay sequences from (a, b), the following transformations may be performed by a device to preserve the complementary property.

[0048] In one or more embodiments, to generate additional complementary Golay sequences from (a, b), a sign flip (e.g., a sign inverse/polarity flip) may be applied. For example, if (a, b) is a pair of complementary Golay sequences, then (a, -b) also may be a pair of complementary Golay sequences. For example, if a = [1 , 1] and b=[l ,-l], then [1 , 1] and [- 1, 1] are complementary. Therefore, sequence 206 may be (a, b), while sequence 208 may be (a, -b). The sign flip may be a special case of phase rotation. In one or more embodiments, instead of rotating the phase by 180 degrees, a finer phase rotation like QPSK or 8PSK may be used for having more random sequences.

[0049] In one or more embodiments, to generate additional complementary Golay sequences from (a, b), a reversal of order of the sequences may be applied. For example, if (a, b) is a pair of complementary Golay sequences, then (a', b') or (b', a') also may be a pair of complementary Golay sequences, where x' may denote a sequence with a reverse order of sequence x. For example, if a=[l ,l] and b=[l,-l], then [1 , 1] and [-1, 1] are complementary. Therefore, sequence 206 may be (a'), while sequence 208 may be (b').

[0050] In one or more embodiments, to generate additional complementary Golay sequences from (a, b), a concatenation of the sequences may be applied. For example, if (a, b) is a pair of complementary Golay sequences, then ([a, b], [a, -b]) also may be a pair of complementary Golay sequences whose length is twice of that of (a, b), and where [xl , x2] may denote concatenating two sequences xl and x2 sequentially. For example, if a = [1 , 1] and b=[l ,-l], then [1 ,1 , 1,-1] and [1, 1,-1, 1] are complementary. Therefore, sequence 206 may be the sequence ([a, b], [a, b]) with the puncturing of some symbols for DC and edge subcarriers, while sequence 208 may be the sequence ([a, b], [a, -b]) with the puncturing of some symbols for DC and edge subcarriers.

[0051] In one or more embodiments, to generate additional complementary Golay sequences from (a, b), interleaving of the sequences may be applied. For example, if (a, b) is a pair of complementary Golay sequences, then ("a, b", "a, -b") also may be a pair of complementary Golay sequences whose length is twice of that of (a, b), and where "xl, x2" may denote interleaving two sequences xl and x2. For example, if a = [1, 1] and b=[l,-l], then [1 ,1 , 1,-1] and [1,-1, 1, 1] are complementary. Therefore, sequence 206 may be ("a, b") with puncturing for DC and edge subcarriers, while sequence 208 may be ("a, -b") with puncturing for DC and edge subcarriers.

[0052] FIG. 3A depicts an enhanced sounding sequence 300, in accordance with one or more example embodiments of the present disclosure.

[0053] Referring to FIG. 3A, the enhanced sounding sequence 300 may double the length of a sequence such as sequence si, k-i, and sequence s₂, k-i, respectively, by using concatenation. A concatenated sequence 302 may be formed by concatenating sequence si, k-i and sequence S2, k-i. A concatenated sequence 304 may be formed by concatenating sequence si, k-i and the sign inverse (e.g., -1) of sequence s₂, k-i, and then applying a phase rotation b(K) (e.g., a sign flip) to sequence si, k-i and the sign inverse (e.g., -1) of sequence s₂, k-i.

[0054] In one or more embodiments, using the sign flip, reverse order, concatenation, and interleaving transformations described above with regard to FIG. 2, 2^K+1 complementary pairs of Golay sequences may be generated, where the length of each sequence may be 2^K_1. The generation of complementary pairs may involve K iterations, which may be based on the number of non-zero subcarriers to which the sounding sequences may be allocated to form a sounding signal. After each iteration (e.g., a k-th iteration), both the length of a sequence and a number of sequences may be doubled. For example, to generate sixteen pairs of complementary sequences, whose sequence length is four, the following process may be implemented.

[0055] In one or more embodiments, a device may select K sign flips (e.g., K numbers of sign inversions) by an index value (e.g., a sequence index). For example, if K=3, sign flips may be represented by sign inverse b(K), where b = [-1 , 1 , -1] . Thus, b(k) when k=l may be - 1 ; b(k) when k=2 may be 1, and b(k) when K=3 may be -1. Using K iterations, a sequence may be generated. For example, at a first iteration, a sequence si = [1], and a sequence S2 = b(l)*[l], so S2 = -1 * [1] = -1. At a second iteration, sequence si = [si, s₂], and sequence S2 = b(2)*[si, -s₂], so si = [1 , -1], and S2 = 1 *[1, 1] = [1 , 1] . At a third iteration, si = [si, s₂], and signal S2 = b(3)*[si, -s₂], so si = [1 , -1, 1 , 1], and S2 = -1 * [1 , -1, -1 , -1] = [-1 , 1 ,1 1]. A pair of length 2^K_1 sequences may be generated from s = (si, s₂). For example, s = ([1, -1 , 1, 1], [-1, 1 , 1, 1]) as b(k) cycles through sign inverse values (e.g., +1 or -1) for all K iterations. Thus, if K=3, then 2³ = 8 pairs of sequences may be generated.

[0056] In one or more embodiments, a key operation may be signal si,k = [si,k-i, S2,k-i], signal S2,k = b(k)* [si,k-i, -s₂,k-i], where sy is the i-th sequence of the complementary pair generated by the j-th iteration and b(k) is the sign inverse for the k-th iteration. The operation may include a binary copy -paste and a sign flip, resulting in low complexity operations. In one or more embodiments, b(k) may be a phase rotation (e.g., exp(j 2jim/M), where m=l,2,... ,M). When M=2, b(k) is a sign flip (e.g., BPSK). When M=4, each b(k) selects a constellation point of the QPSK constellation, where the rotation increment is 90 degrees. When M=8, each b(k) selects a constellation point of the 8PSK constellation, where the rotation increment is 45 degrees.

[0057] In one or more embodiments, using K iterations may result in generating 2^K complementary pairs. The sequences (e.g., sequence 302, sequence 304) generated by concatenating the two sequences of each pair may be orthogonal. Orthogonality may be helpful in mitigating thane adversary attack. In an 80 MHz channel, for example, there may be 250 non-zero energy subcarriers (e.g., for sequence 206 and sequence 208 in FIG. 2) which may be used for lx duration sounding operations. Using eight iterations may result in 256 complementary pairs. For increased security, more pairs may be desirable. A device may double the number of selectable pairs by interleaving and order reversing.

[0058] In one or more embodiments, a device may generate length 2^K"2 sequences and 2^K" ¹ pairs of the sequences (e.g., using K-l iterations). For each complementary pair of length 2^K" ² sequences (si, s₂), we can generate two complementary pairs of length 2^K_1 sequences as follows. Interleaving may be used to generate a pair. For signal s = ("si, s₂", "si, -s₂"), if si = [1 , -1], and S2 = [1, 1], then s = ([1 1 -1 1], [1 -1 -1 -1]). A device may generate another pair by reversing the interleaved pair as such. Let ti = "si, S2" and t₂ = "si, -s₂". Then, s = ( t₂', ti'). For example, si = [1, -1], s₂ = [1 , 1], ti = [1 1 -1 1], ta = [1 -1 -1 -1]. Then, s = ([-1 -1 -1 1], [1 -1 1 1]).

[0059] FIG. 3B depicts an enhanced sounding sequence 350, in accordance with one or more example embodiments of the present disclosure.

[0060] Referring to FIG. 3B, sequence 352 may be a, b, c, d. Sequence 354 may be A, B, C, D. An interleaved sequence 356 may be formed by interleaving sequence 352 with sequence 354, resulting in a, A, b, B, c, C, d, D. An interleaved sequence 358 may be formed by interleaving sequence 352 with a sign inverse (e.g., -1) of sequence 354, resulting in a, -A, b, - B, c, -C, d, -D. Reversing the order of interleaved sequence 356 and of interleaved sequence 358 may result in reversed sequence 360 and reversed sequence 362. For example, reversed sequence 360 may be -D, d, -C, c, -B, b, -A, a, and reversed sequence 362 may be D, d, C, c, B, b, A, a.

[0061] In one or more embodiments, using interleaving and reversing may result in 2^K complementary pairs of length 2^K_1 sequences. These pairs may be different from those generated by concatenation. In total, 2^K+1 complementary pairs of length 2^K_1 sequences may be generated. Over an encrypted channel, a transmitter and receiver may exchange the indication or index of the sign inverses or phase rotation, the indication or index of interleaving, and the indication or index of the reversing so that the transmitter and receiver may generate the same sounding symbol used in a ranging operation to ensure that the devices may verify whether or not an attack was attempted or whether a sounding signal was from an expected device.

[0062] In one or more embodiments, 2^K pairs may be generated using concatenation. 2^K_1 pairs may be generated by interleaving, and 2^K_1 pairs may be generated by using reversion. This way, the number of possible selectable pairs for sounding signal sequences may be significantly increased in order to reduce the chances of an attacker successfully implementing a sounding signal expected by a device which has communicated with another device the relevant sounding signal information used to detect a proper sounding signal.

[0063] In one or more embodiments, because the length of the generated sequences may be of the power of two (e.g., 2^K, 2^K_1), some symbols may be punctured (e.g., removed) from a sounding signal sequence (e.g., sequence 360, sequence 362) to map/allocate punctured sequences to non-zero energy subcarriers (e.g., sequence 206 and sequence 208 of FIG. 2), whose number may not be a power of two. There are multiple ways to perform puncturing, however, puncturing usually increases PAPR. Therefore, it may be beneficial to use a puncturing method with low PAPR.

[0064] FIG. 4 depicts allocating an enhanced sounding sequence 400 to subcarriers, in accordance with one or more example embodiments of the present disclosure.

[0065] Referring to FIG. 4, a portion of sequence si and of sequence S2 may be allocated to non-zero subcarriers in the frequency domain. For example, because the length of sequence si and of sequence S2 may be to the power of two (e.g., 2^K, 2^K_1), and because the number of non-zero subcarriers to which the sounding symbols of sequence si and of sequence S2 may be allocated may not correspond to the length of sequence si and of sequence S2, some symbols of sequence si and of sequence S2 may be punctured (e.g., removed). The punctured symbols 402 of sequence si and the punctured symbols 404 of sequence S2 may be removed, and the remaining symbols of sequence si and of sequence S2 may be allocated to non-zero subcarriers in the frequency domain, resulting in punctured sequence pi and in punctured sequence p2, respectively. Not all subcarriers in the frequency domain may be used to allocate sounding symbols. For example, DC subcarriers 406 may be reserved and may have zero energy.

[0066] FIG. 5A depicts an enhanced PAPR performance evaluation 500 of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0067] Referring to FIG. 5A, the PAPRs of the IEEE 802.11 ax LTF sounding signal 502, of the enhanced Golay sequence sounding signal 504, of the enhanced punctured Golay sequence sounding signal 506, and of the random BPSK modulated sounding signal 508 (e.g., a sounding signal randomly shifted by values of +1 and -1) are shown in comparison to a cumulative distribution function (CDF).

[0068] In one or more embodiments, the PAPR performance of the generated sounding signals may be evaluated by the simulations. A lx symbol duration (e.g., 4 microseconds) at 20 MHz may be used for the simulations. The PAPRs may be measured at RF rather than at baseband level. There may be 56 non-zero energy subcarriers for the bandwidth of 20 MHz.

[0069] As shown in FIG. 5A, the PAPR of the random BPSK modulated sounding signal 508 is very high. The PAPR of the enhanced Golay sequence sounding signal 504 is the lowest. The PAPR of about 20% of the enhanced punctured Golay sequence sounding signal 506 is lower than the PAPR of the IEEE 802.1 lax LTF sounding signal 502, and the PAPR of about 80% of the enhanced punctured Golay sequence sounding signal 506 is higher than the PAPR of the IEEE 802.1 lax LTF sounding signal 502, but still lower than the PAPR of the random BPSK modulated sounding signal 508.

[0070] FIG. 5B depicts an enhanced PAPR performance evaluation 530 of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0071] Referring to FIG. 5B, the PAPRs of the IEEE 802.1 lax LTF sounding signal 532, of the enhanced Golay sequence sounding signal 534, of the enhanced punctured Golay sequence sounding signal 536, and of the random BPSK modulated sounding signal 538 (e.g., a sounding signal randomly shifted by values of +1 and -1) are shown in comparison to a CDF.

[0072] In one or more embodiments, the PAPR performance of the generated sounding signals may be evaluated by the simulations. A lx symbol duration (e.g., 4 microseconds) at 40 MHz may be used for the simulations. The PAPRs may be measured at RF rather than at baseband level. There may be 122 non-zero energy subcarriers for the bandwidth of 40 MHz.

[0073] As shown in FIG. 5B, the PAPR of the random BPSK modulated sounding signal 508 is very high. The PAPR of the enhanced Golay sequence sounding signal 534 is the lowest. At a low CDF, the PAPR of the enhanced punctured Golay sequence sounding signal 536 is lower than the PAPR of the IEEE 802.1 l ax LTF sounding signal 532, and at higher CDFs, the PAPR of the enhanced punctured Golay sequence sounding signal 536 is higher than the PAPR of the IEEE 802.1 lax LTF sounding signal 532, but still lower than the PAPR of the random BPSK modulated sounding signal 538.

[0074] FIG. 5C depicts an enhanced PAPR performance evaluation 560 of sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0075] Referring to FIG. 5C, the PAPRs of the IEEE 802.1 lax LTF sounding signal 562, of the enhanced Golay sequence sounding signal 564, of the enhanced punctured Golay sequence sounding signal 566, and of the random BPSK modulated sounding signal 568 (e.g., a sounding signal randomly shifted by values of +1 and -1) are shown in comparison to a CDF.

[0076] In one or more embodiments, the PAPR performance of the generated sounding signals may be evaluated by the simulations. A lx symbol duration (e.g., 4 microseconds) at 80 MHz may be used for the simulations. The PAPRs may be measured at RF rather than at baseband level. There may be 250 non-zero energy subcarriers for the bandwidth of 80 MHz.

[0077] As shown in FIG. 5C, the PAPR of the random BPSK modulated sounding signal 568 is very high. The PAPR of the enhanced Golay sequence sounding signal 564 is the lowest. At a low CDF, the PAPR of the enhanced punctured Golay sequence sounding signal 566 is lower than the PAPR of the IEEE 802.1 l ax LTF sounding signal 562, and at higher CDFs, the PAPR of the enhanced punctured Golay sequence sounding signal 566 is higher than the PAPR of the IEEE 802.1 lax LTF sounding signal 562, but still lower than the PAPR of the random BPSK modulated sounding signal 568.

[0078] Referring to FIGs. 5A, 5B, and 5C, puncturing is applied to the generated Golay pairs from the allocating of sounding sequences to the non-zero energy subcarriers. The enhanced Golay sequence sounding signals are generated without puncturing, whereas the enhanced punctured Golay pairs are punctured and allocated on non-zero energy subcarriers.

[0079] FIG. 6A illustrates a flow diagram of illustrative process 600 for enhanced sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0080] At block 602, processing circuitry of a device (e.g., the user device(s) 120 and/or the AP 102 of FIG. 1) may determine a first combined Golay sequence based on a first Golay sequence and a second Golay sequence. The first combined Golay sequence may include the first Golay sequence concatenated with the second Golay sequence, a sign inverse of the first and/or second Golay sequence, a reverse order of symbols of the first and/or second Golay sequence, and/or the first Golay sequence interleaved with the second Golay sequence.

[0081] At block 604, the processing circuitry of the device may determine a second combined Golay sequence based on the first of Golay sequence and the second Golay sequence. The second combined Golay sequence may include the first Golay sequence concatenated with the second Golay sequence, a sign inverse of the first and/or second Golay sequence, a reverse order of symbols of the first and/or second Golay sequence, and/or the first Golay sequence interleaved with the second Golay sequence. The second combined Golay sequence may be a different sequence than the first combined Golay sequence.

[0082] At block 606, the processing circuitry of the device may apply a first sign multiplier or phase rotation to the second combined Golay sequence. The first sign multiplier may have a +1 or -1 value, and may flip (e.g., from +1 to -1 or from -1 to +1) with each iteration (e.g., b(k) of FIG. 3A) used to determine combined Golay sequences. For example, if the first Golay sequence is represented by a and the second Golay sequence is represented by b, then applying the sign multiplier may result in a second combined Golay sequence of (a, -b).

[0083] At block 608, the processing circuitry of the device may allocate the first combined Golay sequence and the second combined Golay sequence applied to the first sign multiplier to one or more first subcarriers of a first NDP (e.g., as shown in FIG. 2) in a frequency domain. For example, the NDP may allow for subcarriers of zero energy (e.g., edge subcarriers 210, DC subcarriers 214, edge subcarriers 212 of FIG. 2) and for subcarriers of non-zero energy. Allocating the first and second combined Golay sequences may include mapping symbols of the combined Golay sequences to the subcarriers with non-zero energy (e.g., a +1 or -1 value). To allocate the entirety of the first and second combined Golay sequences, which may have lengths to the order of two (e.g., 2^K or 2^K_1, where K is the number of one or more iterations based on the number of subcamers for a given channel bandwidth), one or more symbols may need to be punctured (e.g., removed) from the combined Golay sequences to fit the combined Golay sequences to the subcarrier allocations of the NDP frame (e.g., as shown in FIG. 4). The allocation may result in a sounding signal having two sequences (e.g., sequence 206 and sequence 208 of FIG. 2) represented by subcarriers having non-zero energy, and the NDP may include the subcamers with non-zero energy in the sounding signal. A random CSD may also be applied to a sounding signal.

[0084] At block 610, the processing circuitry of the device may cause the device to send the NDP. The NDP may be used as a sounding signal. A random CSD may be applied to the sounding signal so that the timing of the signal may be unknown to an attacking device, thereby making it difficult for an attacking device to perform an attack.

[0085] FIG. 6B illustrates a flow diagram of illustrative process 650 for enhanced sounding signals, in accordance with one or more example embodiments of the present disclosure.

[0086] At block 652, processing circuitry of a device (e.g., the user device(s) 120 and/or the AP 102 of FIG. 1) may identify an NDP (e.g., NDP sounding signal 202 of FIG. 2) received from a second device on a communication channel. The NDP may be used as a sounding signal and may have subcarriers of zero energy (e.g., edge subcarriers 210, DC subcamers 214, edge subcarriers 212 of FIG. 2), and subcarriers of non-zero energy (e.g., a +1 or -1 value such as in sequence 206 and sequence 208 of FIG. 2). A portion (e.g., portion 204 of FIG. 2) of the NDP may be used for a sounding sequence.

[0087] At block 654, the processing circuitry of the device may determine, based at least in part on one or more subcarriers of the NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence. The first combined Golay sequence may include a first Golay sequence and a second Golay sequence. The second combined Golay sequence may include the first Golay sequence and the second Golay sequence applied to a sign multiplier (e.g., a +1 or -1 value). The first and second combined Golay sequences may include the first Golay sequence concatenated with the second Golay sequence, a sign inverse of the first and/or second Golay sequence, a reverse order of symbols of the first and/or second Golay sequence, and/or the first Golay sequence interleaved with the second Golay sequence. The NDP may also have a random CSD applied, and the device may determine whether the signal is valid or part of an attack by verifying the random CSD.

[0088] At block 656, the processing circuitry of the device may estimate the communication channel with which the NDP is received by using the symbols of the first combined Golay sequence and the second combined Golay sequence. Because the combined Golay sequences may allow for a large number of Golay sequences with which to perform sounding signal operations, it may be unlikely that an attacker could replicate the sounding signal. In addition, the combined Golay sequences may have a relatively low PAPR for efficient sounding operations.

[0089] The device as a receiving device may benefit from having an indication of a sounding signal sequence to be used. For, example, the receiving device may receive multiple NDPs with different sequences used for sounding. A previous sequence of measurement frames may include a location measurement report (LMR) or another frame which may include an indication (e.g., a key) of the sequences to be used in a sounding operation. The information in the LMR or other frame may be encrypted for additional protection so that an attacking device may not easily determine the expected sounding sequence to be used even if the attacking device were to receive the encrypted information.

[0090] FIG. 7 shows a functional diagram of an exemplary communication station 700 in accordance with some embodiments. In one embodiment, FIG. 7 illustrates a functional block diagram of a communication station that may be suitable for use as an AP 102 (FIG. 1) or a user device 120 (FIG. 1) in accordance with some embodiments. The communication station 700 may also be suitable for use as a handheld device, a mobile device, a cellular telephone, a smartphone, a tablet, a netbook, a wireless terminal, a laptop computer, a wearable computer device, a femtocell, a high data rate (HDR) subscriber station, an access point, an access terminal, or other personal communication system (PCS) device.

[0091] The communication station 700 may include communications circuitry 702 and a transceiver 710 for transmitting and receiving signals to and from other communication stations using one or more antennas 701. The communications circuitry 702 may include circuitry that can operate the physical layer (PHY) communications and/or media access control (MAC) communications for controlling access to the wireless medium, and/or any other communications layers for transmitting and receiving signals. The communication station 700 may also include processing circuitry 706 and memory 708 arranged to perform the operations described herein. In some embodiments, the communications circuitry 702 and the processing circuitry 706 may be configured to perform operations detailed in FIGs. 2, 3A, 3B, 4, 5A, 5B, 6 A, and 6B.

[0092] In accordance with some embodiments, the communications circuitry 702 may be arranged to contend for a wireless medium and configure frames or packets for communicating over the wireless medium. The communications circuitry 702 may be arranged to transmit and receive signals. The communications circuitry 702 may also include circuitry for modulation/demodulation, upconversion/downconversion, filtering, amplification, etc. In some embodiments, the processing circuitry 706 of the communication station 700 may include one or more processors. In other embodiments, two or more antennas 701 may be coupled to the communications circuitry 702 arranged for sending and receiving signals. The memory 708 may store information for configuring the processing circuitry 706 to perform operations for configuring and transmitting message frames and performing the various operations described herein. The memory 708 may include any type of memory, including non-transitory memory, for storing information in a form readable by a machine (e.g., a computer). For example, the memory 708 may include a computer-readable storage device , read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices and other storage devices and media.

[0093] In some embodiments, the communication station 700 may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), a wearable computer device, or another device that may receive and/or transmit information wirelessly.

[0094] In some embodiments, the communication station 700 may include one or more antennas 701. The antennas 701 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated for spatial diversity and the different channel characteristics that may result between each of the antennas and the antennas of a transmitting station.

[0095] In some embodiments, the communication station 700 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen. [0096] Although the communication station 700 is illustrated as having several separate functional elements, two or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may include one or more microprocessors, DSPs, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio- frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements of the communication station 700 may refer to one or more processes operating on one or more processing elements.

[0097] Certain embodiments may be implemented in one or a combination of hardware, firmware, and software. Other embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory memory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. In some embodiments, the communication station 700 may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

[0098] FIG. 8 illustrates a block diagram of an example of a machine 800 or system upon which any one or more of the techniques (e.g., methodologies) discussed herein may be performed. In other embodiments, the machine 800 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 800 may operate in the capacity of a server machine, a client machine, or both in server-client network environments. In an example, the machine 800 may act as a peer machine in peer-to-peer (P2P) (or other distributed) network environments. The machine 800 may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a wearable computer device, a web appliance, a network router, a switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine, such as a base station. Further, while only a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0099] Examples, as described herein, may include or may operate on logic or a number of components, modules, or mechanisms. Modules are tangible entities (e.g., hardware) capable of performing specified operations when operating. A module includes hardware. In an example, the hardware may be specifically configured to carry out a specific operation (e.g., hardwired). In another example, the hardware may include configurable execution units (e.g., transistors, circuits, etc.) and a computer readable medium containing instructions where the instructions configure the execution units to carry out a specific operation when in operation. The configuring may occur under the direction of the executions units or a loading mechanism. Accordingly, the execution units are communicatively coupled to the computer-readable medium when the device is operating. In this example, the execution units may be a member of more than one module. For example, under operation, the execution units may be configured by a first set of instructions to implement a first module at one point in time and reconfigured by a second set of instructions to implement a second module at a second point in time.

[0100] The machine (e.g., computer system) 800 may include a hardware processor 802 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 804 and a static memory 806, some or all of which may communicate with each other via an interlink (e.g., bus) 808. The machine 800 may further include a power management device 832, a graphics display device 810, an alphanumeric input device 812 (e.g. , a keyboard), and a user interface (UI) navigation device 814 (e.g., a mouse). In an example, the graphics display device 810, alphanumeric input device 812, and UI navigation device 814 may be a touch screen display. The machine 800 may additionally include a storage device (i.e., drive unit) 816, a signal generation device 818 (e.g., a speaker), an enhanced sounding device 819, a network interface device/transceiver 820 coupled to antenna(s) 830, and one or more sensors 828, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensor. The machine 800 may include an output controller 834, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.)).

[0101] The storage device 816 may include a machine readable medium 822 on which is stored one or more sets of data structures or instructions 824 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 824 may also reside, completely or at least partially, within the main memory 804, within the static memory 806, or within the hardware processor 802 during execution thereof by the machine 800. In an example, one or any combination of the hardware processor 802, the main memory 804, the static memory 806, or the storage device 816 may constitute machine-readable media.

[0102] The enhanced sounding device 819 may carry out or perform any of the operations and processes (e.g., process 600 of FIG. 6A and process 650 of FIG. 6B) described and shown above.

[0103] In one or more embodiments, the enhanced sounding device 819 may determine a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determine a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; apply a first phase rotation to the second combined Golay sequence; allocate the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarners of a first null data packet (NDP) in a frequency domain; and cause to send the first NDP.

[0104] In one or more embodiments, the enhanced sounding device 819 may perform operations including identifying, at a first device, a first null data packet (NDP) received from a second device on a communication channel; determining, based at least in part on one or more first subcarners of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and estimating the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

[0105] In one or more embodiments, the enhanced sounding device 819 may perform a method including determining, by processing circuitry of a device, a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determining, by the processing circuitry, a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; applying, by the processing circuitry, a first phase rotation to the second combined Golay sequence; allocating, by the processing circuitry, the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarners of a first null data packet (NDP) in a frequency domain; and causing to send, by the processing circuitry, the first NDP.

[0106] It is understood that the above are only a subset of what the enhanced sounding device 819 may be configured to perform and that other functions included throughout this disclosure may also be performed by the enhanced sounding device 819.

[0107] While the machine-readable medium 822 is illustrated as a single medium, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 824.

[0108] Various embodiments may be implemented fully or partially in software and/or firmware. This software and/or firmware may take the form of instructions contained in or on a non-transitory computer-readable storage medium. Those instructions may then be read and executed by one or more processors to enable performance of the operations described herein. The instructions may be in any suitable form, such as but not limited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. Such a computer-readable medium may include any tangible non-transitory medium for storing information in a form readable by one or more computers, such as but not limited to read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; a flash memory, etc.

[0109] The term "machine-readable medium" may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 800 and that cause the machine 800 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting machine-readable medium examples may include solid-state memories and optical and magnetic media. In an example, a massed machine-readable medium includes a machine-readable medium with a plurality of particles having resting mass. Specific examples of massed machine-readable media may include non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD- ROM disks.

[0110] The instructions 824 may further be transmitted or received over a communications network 826 using a transmission medium via the network interface device/transceiver 820 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communications networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), plain old telephone (POTS) networks, wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.1 1 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, and peer-to-peer (P2P) networks, among others. In an example, the network interface device/transceiver 820 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 826. In an example, the network interface device/transceiver 820 may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple- output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term "transmission medium" shall be taken to include any intangible medium that is capable of storing, encoding, or carrying instructions for execution by the machine 800 and includes digital or analog communications signals or other intangible media to facilitate communication of such software. The operations and processes described and shown above may be carried out or performed in any suitable order as desired in various implementations. Additionally, in certain implementations, at least a portion of the operations may be carried out in parallel. Furthermore, in certain implementations, less than or more than the operations described may be performed.

[011 1] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The terms "computing device," "user device," "communication station," "station," "handheld device," "mobile device," "wireless device" and "user equipment" (UE) as used herein refers to a wireless communication device such as a cellular telephone, a smartphone, a tablet, a netbook, a wireless terminal, a laptop computer, a femtocell, a high data rate (HDR) subscriber station, an access point, a printer, a point of sale device, an access terminal, or other personal communication system (PCS) device. The device may be either mobile or stationary.

[0112] As used within this document, the term "communicate" is intended to include transmitting, or receiving, or both transmitting and receiving. This may be particularly useful in claims when describing the organization of data that is being transmitted by one device and received by another, but only the functionality of one of those devices is required to infringe the claim. Similarly, the bidirectional exchange of data between two devices (both devices transmit and receive during the exchange) may be described as "communicating," when only the functionality of one of those devices is being claimed. The term "communicating" as used herein with respect to a wireless communication signal includes transmitting the wireless communication signal and/or receiving the wireless communication signal. For example, a wireless communication unit, which is capable of communicating a wireless communication signal, may include a wireless transmitter to transmit the wireless communication signal to at least one other wireless communication unit, and/or a wireless communication receiver to receive the wireless communication signal from at least one other wireless communication unit.

[0113] As used herein, unless otherwise specified, the use of the ordinal adjectives "first," "second," "third," etc., to describe a common object, merely indicates that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

[0114] The term "access point" (AP) as used herein may be a fixed station. An access point may also be referred to as an access node, a base station, an evolved node B (eNodeB), or some other similar terminology known in the art. An access terminal may also be called a mobile station, user equipment (UE), a wireless communication device, or some other similar terminology known in the art. Embodiments disclosed herein generally pertain to wireless networks. Some embodiments may relate to wireless networks that operate in accordance with one of the IEEE 802.1 1 standards.

[0115] Some embodiments may be used in conjunction with various devices and systems, for example, a personal computer (PC), a desktop computer, a mobile computer, a laptop computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, a personal digital assistant (PDA) device, a handheld PDA device, an onboard device, an off-board device, a hybrid device, a vehicular device, a non-vehicular device, a mobile or portable device, a consumer device, a non-mobile or non-portable device, a wireless communication station, a wireless communication device, a wireless access point (AP), a wired or wireless router, a wired or wireless modem, a video device, an audio device, an audio-video (A/V) device, a wired or wireless network, a wireless area network, a wireless video area network (WVAN), a local area network (LAN), a wireless LAN (WLAN), a personal area network (PAN), a wireless PAN (WPAN), and the like.

[0116] Some embodiments may be used in conjunction with one way and/or two-way radio communication systems, cellular radio-telephone communication systems, a mobile phone, a cellular telephone, a wireless telephone, a personal communication system (PCS) device, a PDA device which incorporates a wireless communication device, a mobile or portable global positioning system (GPS) device, a device which incorporates a GPS receiver or transceiver or chip, a device which incorporates an RFID element or chip, a multiple input multiple output (MIMO) transceiver or device, a single input multiple output (SIMO) transceiver or device, a multiple input single output (MISO) transceiver or device, a device having one or more internal antennas and/or external antennas, digital video broadcast (DVB) devices or systems, multi- standard radio devices or systems, a wired or wireless handheld device, e.g., a smartphone, a wireless application protocol (WAP) device, or the like.

[0117] Some embodiments may be used in conjunction with one or more types of wireless communication signals and/or systems following one or more wireless communication protocols, for example, radio frequency (RF), infrared (IR), frequency-division multiplexing (FDM), orthogonal FDM (OFDM), time-division multiplexing (TDM), time-division multiple access (TDMA), extended TDMA (E-TDMA), general packet radio service (GPRS), extended GPRS, code-division multiple access (CDMA), wideband CDMA (WCDMA), CDMA 2000, single-carrier CDMA, multi-carrier CDMA, multi-carrier modulation (MDM), discrete multi- tone (DMT), Bluetooth®, global positioning system (GPS), Wi-Fi, Wi-Max, ZigBee, ultra- wideband (UWB), global system for mobile communications (GSM), 2G, 2.5G, 3G, 3.5G, 4G, fifth generation (5G) mobile networks, 3 GPP, long term evolution (LTE), LTE advanced, enhanced data rates for GSM Evolution (EDGE), or the like. Other embodiments may be used in various other devices, systems, and/or networks.

[0118] Example 1 may include a device, the device comprising memory and processing circuitry configured to: determine a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determine a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; apply a first phase rotation to the second combined Golay sequence; allocate the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and cause to send the first NDP.

[0119] Example 2 may include the device of example 1 and/or some other example herein, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to each other.

[0120] Example 3 may include the device of example 1 and/or some other example herein, wherein to allocate the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises the storage and the processing circuitry being further configured to: determine a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence; determine a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and allocate the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

[0121] Example 4 may include the device of example 3 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0122] Example 5 may include the device of example 4 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0123] Example 6 may include the device of example 1 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and the processing circuitry being further configured to concatenate the first Golay sequence and the second Golay sequence.

[0124] Example 7 may include the device of example 1 and/or some other example herein, wherein the storage and the processing circuitry are further configured to: determine a third combined Golay sequence based at least in part on a second phase rotation of the second combined Golay sequence, wherein the second phase rotation is different than the first phase rotation; allocate the third combined Golay sequence to one or more subcarriers of a second NDP in the frequency domain; and cause to send the second NDP.

[0125] Example 8 may include the device of example 1 and/or some other example herein, wherein the storage and the processing circuitry are further configured to determine 2^K pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0126] Example 9 may include the device of example 1 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to interleave the first Golay sequence and the second Golay sequence.

[0127] Example 10 may include the device of example 9 and/or some other example herein, wherein the storage and the processing circuitry are further configured to determine 2^K_1 pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0128] Example 1 1 may include the device of example 1 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to reverse an order of symbols of the first Golay sequence and of the second Golay sequence.

[0129] Example 12 may include the device of example 1 and/or some other example herein, wherein the storage and the processing circuitry are further configured to: determine a random cyclic shift diversity; and cause to send a second NDP based at least in part on the random cyclic shift diversity.

[0130] Example 13 may include the device of example 1 and/or some other example herein, further comprising a transceiver configured to transmit and receive wireless signals.

[0131] Example 14 may include the device of example 13 and/or some other example herein, further comprising one or more antennas coupled to the transceiver.

[0132] Example 15 may include a non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: identifying, at a first device, a first null data packet (NDP) received from a second device on a communication channel; determining, based at least in part on one or more first subcarriers of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and estimating the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

[0133] Example 16 may include the non-transitory computer-readable medium of example 15 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0134] Example 17 may include the non-transitory computer-readable medium of example 16 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0135] Example 18 may include the non-transitory computer-readable medium of example 15 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence concatenated with the second Golay sequence.

[0136] Example 19 may include the non-transitory computer-readable medium of example 15 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence interleaved with the second Golay sequence. [0137] Example 20 may include the non-transitory computer-readable medium of example 15 and/or some other example herein, wherein the first combined Golay sequence comprises a reverse order of the first Golay sequence and of the second Golay sequence.

[0138] Example 21 may include the non-transitory computer-readable medium of example 15 and/or some other example herein, the operations further comprising: identifying a second NDP received from the second device; and determining a random cyclic shift diversity associated with the second NDP.

[0139] Example 22 may include a method comprising: determining, by processing circuitry of a device, a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determining, by the processing circuitry, a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; applying, by the processing circuitry, a first phase rotation to the second combined Golay sequence; allocating, by the processing circuitry, the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and causing to send, by the processing circuitry, the first NDP.

[0140] Example 23 may include the method of example 22 and/or some other example herein, wherein allocating the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises: determining a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence; determining a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and allocating the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

[0141] Example 24 may include the method of example 22 and/or some other example herein, wherein determining the first combined Golay sequence comprises concatenating the first Golay sequence and the second Golay sequence.

[0142] Example 25 may include the method of example 22 and/or some other example herein, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to one another

[0143] Example 26 may include an apparatus comprising means for performing a method as claimed in any one of examples 22-25. [0144] Example 27 may include a system, comprising at least one memory device having programmed instruction that, in response to execution cause at least one processor to perform the method of any one of examples 22-225.

[0145] Example 28 may include a machine-readable medium including code, when executed, to cause a machine to perform the method of any one of examples 22-25.

[0146] Example 29 may include a non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: determining a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determining a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; applying a first phase rotation to the second combined Golay sequence; allocating the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and causing to send the first NDP.

[0147] Example 30 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to each other.

[0148] Example 31 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein to allocate the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises the storage and the processing circuitry being further configured to: determine a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence; determine a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and allocate the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

[0149] Example 32 may include the non-transitory computer-readable medium of example

31 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0150] Example 33 may include the non-transitory computer-readable medium of example

32 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0151] Example 34 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and the processing circuitry being further configured to concatenate the first Golay sequence and the second Golay sequence.

[0152] Example 35 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein the operations further comprise: determining a third combined Golay sequence based at least in part on a second phase rotation of the second combined Golay sequence, wherein the second phase rotation is different than the first phase rotation; allocating the third combined Golay sequence to one or more subcarriers of a second NDP in the frequency domain; and causing to send the second NDP.

[0153] Example 36 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein the operations further comprise determining 2^K pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0154] Example 37 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to interleave the first Golay sequence and the second Golay sequence.

[0155] Example 38 may include the non-transitory computer-readable medium of example 37 and/or some other example herein, wherein the operations further comprise determining 2^K" ¹ pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0156] Example 39 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to reverse an order of symbols of the first Golay sequence and of the second Golay sequence.

[0157] Example 40 may include the non-transitory computer-readable medium of example 29 and/or some other example herein, wherein the operations further comprise: determining a random cyclic shift diversity; and causing to send a second NDP based at least in part on the random cyclic shift diversity.

[0158] Example 41 may include an apparatus comprising means for: determining a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence; determining a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence; applying a first phase rotation to the second combined Golay sequence; allocating the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and causing to send the first NDP.

[0159] Example 42 may include the apparatus of example 41 and/or some other example herein, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to each other.

[0160] Example 43 may include the apparatus of example 41 and/or some other example herein, wherein to allocate the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises the storage and the processing circuitry being further configured to: determine a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence; determine a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and allocate the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

[0161] Example 44 may include the apparatus of example 43 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0162] Example 45 may include the apparatus of example 44 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0163] Example 46 may include the apparatus of example 41 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and the processing circuitry being further configured to concatenate the first Golay sequence and the second Golay sequence.

[0164] Example 47 may include the apparatus of example 41 and/or some other example herein, further comprising: determining a third combined Golay sequence based at least in part on a second phase rotation of the second combined Golay sequence, wherein the second phase rotation is different than the first phase rotation; allocating the third combined Golay sequence to one or more subcarriers of a second NDP in the frequency domain; and causing to send the second NDP.

[0165] Example 48 may include the apparatus of example 41 and/or some other example herein, further comprising means for determining 2^K pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0166] Example 49 may include the apparatus of example 41 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to interleave the first Golay sequence and the second Golay sequence.

[0167] Example 50 may include the apparatus of example 49 and/or some other example herein, further comprising means for determining 2^K_1 pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

[0168] Example 51 may include the apparatus of example 41 and/or some other example herein, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to reverse an order of symbols of the first Golay sequence and of the second Golay sequence.

[0169] Example 52 may include the apparatus of example 41 and/or some other example herein, further comprising means for: determining a random cyclic shift diversity; and causing to send a second NDP based at least in part on the random cyclic shift diversity.

[0170] Example 53 may include a device, the device comprising memory and processing circuitry configured to: identify, at a first device, a first null data packet (NDP) received from a second device on a communication channel; determine, based at least in part on one or more first subcarriers of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and estimate the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

[0171] Example 54 may include the device of example 53 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0172] Example 55 may include the device of example 54 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0173] Example 56 may include the device of example 53 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence concatenated with the second Golay sequence.

[0174] Example 57 may include the device of example 53 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence interleaved with the second Golay sequence. [0175] Example 58 may include the device of example 53 and/or some other example herein, wherein the first combined Golay sequence comprises a reverse order of the first Golay sequence and of the second Golay sequence.

[0176] Example 59 may include the device of example 53 and/or some other example herein, the storage and the processing circuitry are further configured to: identify a second NDP received from the second device; and determine a random cyclic shift diversity associated with the second NDP.

[0177] Example 60 may include a method comprising; determining, based at least in part on one or more first subcarriers of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and estimating the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

[0178] Example 61 may include the method of example 60 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0179] Example 62 may include the method of example 61 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0180] Example 63 may include the method of example 60 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence concatenated with the second Golay sequence.

[0181] Example 64 may include the method of example 60 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence interleaved with the second Golay sequence.

[0182] Example 65 may include the method of example 60 and/or some other example herein, wherein the first combined Golay sequence comprises a reverse order of the first Golay sequence and of the second Golay sequence.

[0183] Example 66 may include the method of example 60 and/or some other example herein, further comprising: identifying a second NDP received from the second device; and determining a random cyclic shift diversity associated with the second NDP.

[0184] Example 67 may include an apparatus comprising means for performing a method as claimed in any one of examples 60-66.

[0185] Example 68 may include a system, comprising at least one memory device having programmed instruction that, in response to execution cause at least one processor to perform the method of any one of examples 60-66.

[0186] Example 69 may include a machine readable medium including code, when executed, to cause a machine to perform the method of any one of examples 60-66.

[0187] Example 70 may include an apparatus comprising means for An apparatus comprising means for; determining, based at least in part on one or more first subcarriers of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and estimating the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

[0188] Example 71 may include the apparatus of example 70 and/or some other example herein, wherein the one or more first subcarriers have non-zero energy.

[0189] Example 72 may include the apparatus of example 71 and/or some other example herein, wherein the first NDP comprises one or more second subcarriers having zero energy.

[0190] Example 73 may include the apparatus of example 70 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence concatenated with the second Golay sequence.

[0191] Example 74 may include the apparatus of example 70 and/or some other example herein, wherein the first combined Golay sequence comprises the first Golay sequence interleaved with the second Golay sequence.

[0192] Example 75 may include the apparatus of example 70 and/or some other example herein, wherein the first combined Golay sequence comprises a reverse order of the first Golay sequence and of the second Golay sequence.

[0193] Example 76 may include the apparatus of example 70 and/or some other example herein, further comprising means for: identifying a second NDP received from the second device; and determining a random cyclic shift diversity associated with the second NDP.

[0194] Example 77 may include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of a method described in or related to any of examples 1-76, or any other method or process described herein [0195] Example 78 may include an apparatus comprising logic, modules, and/or circuitry to perform one or more elements of a method described in or related to any of examples 1 -76, or any other method or process described herein.

[0196] Example 79 may include a method, technique, or process as described in or related to any of examples 1-76, or portions or parts thereof.

[0197] Example 80 may include an apparatus comprising: one or more processors and one or more computer readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform the method, techniques, or process as described in or related to any of examples 1-76, or portions thereof.

[0198] Example 81 may include a method of communicating in a wireless network as shown and described herein.

[0199] Example 82 may include a system for providing wireless communication as shown and described herein.

[0200] Example 83 may include a device for providing wireless communication as shown and described herein.

[0201] Embodiments according to the disclosure are in particular disclosed in the attached claims directed to a method, a storage medium, a device and a computer program product, wherein any feature mentioned in one claim category, e.g., method, can be claimed in another claim category, e.g., system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject- matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.

[0202] The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. [0203] Some embodiments may be used in conjunction with one or more types of wireless communication signals and/or systems following one or more wireless communication protocols, for example, radio frequency (RF), infrared (IR), frequency-division multiplexing (FDM), orthogonal FDM (OFDM), time-division multiplexing (TDM), time-division multiple access (TDMA), extended TDMA (E-TDMA), general packet radio service (GPRS), extended GPRS, code-division multiple access (CDMA), wideband CDMA (WCDMA), CDMA 2000, single-carrier CDMA, multi-carrier CDMA, multi-carrier modulation (MDM), discrete multi- tone (DMT), Bluetooth®, global positioning system (GPS), Wi-Fi, Wi-Max, ZigBee, ultra- wideband (UWB), global system for mobile communications (GSM), 2G, 2.5G, 3G, 3.5G, 4G, fifth generation (5G) mobile networks, 3 GPP, long term evolution (LTE), LTE advanced, enhanced data rates for GSM Evolution (EDGE), or the like. Other embodiments may be used in various other devices, systems, and/or networks.

[0204] Certain aspects of the disclosure are described above with reference to block and flow diagrams of systems, methods, apparatuses, and/or computer program products according to various implementations. It will be understood that one or more blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and the flow diagrams, respectively, may be implemented by computer-executable program instructions. Likewise, some blocks of the block diagrams and flow diagrams may not necessarily need to be performed in the order presented, or may not necessarily need to be performed at all, according to some implementations.

[0205] Certain aspects of the disclosure are described above with reference to block and flow diagrams of systems, methods, apparatuses, and/or computer program products according to various implementations. It will be understood that one or more blocks of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and the flow diagrams, respectively, may be implemented by computer-executable program instructions. Likewise, some blocks of the block diagrams and flow diagrams may not necessarily need to be performed in the order presented, or may not necessarily need to be performed at all, according to some implementations.

[0206] These computer-executable program instructions may be loaded onto a special- purpose computer or other particular machine, a processor, or other programmable data processing apparatus to produce a particular machine, such that the instructions that execute on the computer, processor, or other programmable data processing apparatus create means for implementing one or more functions specified in the flow diagram block or blocks. These computer program instructions may also be stored in a computer-readable storage media or memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage media produce an article of manufacture including instruction means that implement one or more functions specified in the flow diagram block or blocks. As an example, certain implementations may provide for a computer program product, comprising a computer- readable storage medium having a computer-readable program code or program instructions implemented therein, said computer-readable program code adapted to be executed to implement one or more functions specified in the flow diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational elements or steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide elements or steps for implementing the functions specified in the flow diagram block or blocks.

[0207] Accordingly, blocks of the block diagrams and flow diagrams support combinations of means for performing the specified functions, combinations of elements or steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, may be implemented by special-purpose, hardware-based computer systems that perform the specified functions, elements or steps, or combinations of special-purpose hardware and computer instructions.

[0208] Conditional language, such as, among others, "can," "could," "might," or "may," unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language is not generally intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.

[0209] Many modifications and other implementations of the disclosure set forth herein will be apparent having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS What is claimed is:

1. A device, the device comprising storage and processing circuitry configured to: determine a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence;

determine a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence;

apply a first phase rotation to the second combined Golay sequence;

allocate the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and

cause to send the first NDP.

2. The device of claim 1, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to each other.

3. The device of any of claims 1 or 2, wherein to allocate the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises the storage and the processing circuitry being further configured to:

determine a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence;

determine a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and

allocate the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

4. The device of claim 3, wherein the one or more first subcarriers have non-zero energy.

5. The device of claim 4, wherein the first NDP comprises one or more second subcarriers having zero energy.

6. The device of claim 1, wherein to determine the first combined Golay sequence comprises the storage and the processing circuitry being further configured to concatenate the first Golay sequence and the second Golay sequence.

7. The device of claim 1, wherein the storage and the processing circuitry are further configured to:

determine a third combined Golay sequence based at least in part on a second phase rotation of the second combined Golay sequence, wherein the second phase rotation is different than the first phase rotation;

allocate the third combined Golay sequence to one or more subcarriers of a second NDP in the frequency domain; and

cause to send the second NDP.

8. The device of claim 1, wherein the storage and the processing circuitry are further configured to determine 2^K pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

9. The device of claim 1, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to interleave the first Golay sequence and the second Golay sequence.

10. The device of claim 9, wherein the storage and the processing circuitry are further configured to determine 2^K_1 pairs of Golay sequences using the first Golay sequence and the second Golay sequence, wherein K is a number of iterations based at least in part on the one or more first subcarriers.

11. The device of claim 1, wherein to determine the first combined Golay sequence comprises the storage and processing circuitry being further configured to reverse an order of symbols of the first Golay sequence and of the second Golay sequence.

12. The device of claim 1, wherein the storage and the processing circuitry are further configured to:

determine a random cyclic shift diversity; and cause to send a second NDP based at least in part on the random cyclic shift diversity.

13. The device of claim 1, further comprising a transceiver configured to transmit and receive wireless signals.

14. The device of claim 13, further comprising one or more antennas coupled to the transceiver.

15. A non-transitory computer-readable medium storing computer-executable instructions which when executed by one or more processors result in performing operations comprising: identifying, at a first device, a first null data packet (NDP) received from a second device on a communication channel;

determining, based at least in part on one or more first subcarriers of the first NDP in a frequency domain, a first combined Golay sequence and a second combined Golay sequence, wherein the first combined Golay sequence comprises a first Golay sequence and a second Golay sequence, and wherein the second combined Golay sequence comprises the first Golay sequence and the second Golay sequence applied to a phase rotation; and

estimating the communication channel based at least in part on the first combined Golay sequence and the second combined Golay sequence.

16. The non-transitory computer-readable medium of claim 15, wherein the one or more first subcarriers have non-zero energy.

17. The non-transitory computer-readable medium of any of claims 15 or 16, wherein the first NDP comprises one or more second subcarriers having zero energy.

18. The non-transitory computer-readable medium of any of claims 15-17, wherein the first combined Golay sequence comprises the first Golay sequence concatenated with the second Golay sequence.

19. The non-transitory computer-readable medium of any of claims 15-17, wherein the first combined Golay sequence comprises the first Golay sequence interleaved with the second Golay sequence.

20. The non-transitory computer-readable medium of any of claims 15-17, wherein the first combined Golay sequence comprises a reverse order of the first Golay sequence and of the second Golay sequence.

21. The non-transitory computer-readable medium of any of claims 15-20, the operations further comprising:

identifying a second NDP received from the second device; and

determining a random cyclic shift diversity associated with the second NDP.

22. A method, comprising:

determining, by processing circuitry of a device, a first combined Golay sequence based at least in part on a first Golay sequence and a second Golay sequence;

determining, by the processing circuitry, a second combined Golay sequence based at least in part on the first of Golay sequence and the second Golay sequence;

applying, by the processing circuitry, a first phase rotation to the second combined Golay sequence;

allocating, by the processing circuitry, the first combined Golay sequence and the second combined Golay sequence applied to the first phase rotation to one or more first subcarriers of a first null data packet (NDP) in a frequency domain; and

causing to send, by the processing circuitry, the first NDP.

23. The method of claim 22, wherein allocating the first combined Golay sequence and the second combined Golay sequence to the one or more first subcarriers comprises:

determining a modified first combined Golay sequence by removing one or more symbols of the first combined Golay sequence;

determining a modified second combined Golay sequence by removing one or more symbols of the second combined Golay sequence; and

allocating the modified first combined Golay sequence and the modified second combined Golay sequence to the one or more first subcarriers.

24. The method of any of claims 22 or 23, wherein determining the first combined Golay sequence comprises concatenating the first Golay sequence and the second Golay sequence.

25. The method of any of claims 22 or 23, wherein the first combined Golay sequence and the second combined Golay sequence are complementary to one another..