PATENT DOCUMENT

Publication Number: US-10887863-B2
Application Number: US-202016805243-A
Country: US
Kind Code: B2

Title: Receiver for secure time-of-arrival calculation

Abstract:
Some embodiments include an apparatus, method, and computer program product for secure time-of-arrivals calculations in an ultra-wideband (UWB) system. Some embodiments include a UWB receiver that can inspect a channel impulse response (CIR) between a first and second electronic device and identify one or more first path candidates (FPCs). For a candidate path, the UWB receiver can identify subsequent paths that create inter-pulse interference (IPI) on the candidate path. Using estimates for the interfering path strengths (e.g., channel coefficients from the CIR) and the known cryptographically sequence of pulse polarities (SPP), the UWB receiver can reduce the IPI from these interfering paths on the FPCs, and then make decisions based at least on the remaining pulse polarities, whether the one or more FPCs comprise a legitimate transmission signal.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a transceiver configured to receive wireless transmissions from a second electronic device; 
 a processor, coupled to the transceiver, configured to:
 receive discrete-time samples that correspond to a received wireless transmission; 
 estimate a channel impulse response (CIR) comprising estimates of one or more propagation path coefficients based at least on the discrete-time samples and a sequence of pulse polarities (SPP); 
 based on the CIR, estimate a First-Path Candidate (FPC) corresponding to the SPP; 
 reduce inter-pulse interference (IPI) on one or more samples that correspond to the FPC; and 
 after the reduction, determine based at least on the SPP, whether the one or more samples represents a legitimate transmission of the SPP. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein to reduce the IPI, the processor is configured to:
 estimate interference on the one or more samples from preceding pulses in the SPP, wherein the estimate is based at least on the SPP and the CIR; and 
 subtract the estimated interference from the one or more samples. 
 
     
     
       3. The electronic device of  claim 1 , wherein to determine based at least on the SPP whether the one or more samples represent a legitimate transmission of the SPP, the processor is configured to:
 estimate a polarity sequence of the one or more samples; 
 compare the estimated polarity sequence with the SPP; 
 determine whether the comparison satisfies a configurable threshold; and 
 based on the determination, initiate a security operation. 
 
     
     
       4. The electronic device of  claim 3 , wherein to estimate the polarity sequence, the processor is configured to:
 equalize the one or more samples based on the one or more propagation path coefficients of the FPC; and 
 estimate polarities of the equalized one or more samples. 
 
     
     
       5. The electronic device of  claim 1 , wherein the SPP is a cryptographically secure pulse sequence (CSPS) or a training sequence of a physical layer protocol data unit (PPDU). 
     
     
       6. The electronic device of  claim 1 , wherein to determine based at least on the SPP whether the one or more samples represents a legitimate transmission of the SPP, the processor is configured to:
 compute a correlation between the one or more samples and the SPP; 
 compute a sample norm of the one or more samples; 
 compute a ratio between a magnitude of the correlation and the sample norm; and 
 determine whether the ratio exceeds a configurable threshold. 
 
     
     
       7. The electronic device of  claim 6 , wherein the sample norm comprises a square-root of a sum of squared magnitudes of the one or more samples. 
     
     
       8. A method, comprising:
 receiving discrete-time samples that correspond to a received wireless transmission; 
 estimating a channel impulse response (CIR) comprising estimates of one or more propagation path coefficients based at least on the discrete-time samples; 
 estimating, based at least on the CIR, a First-Path Candidate (FPC) corresponding to a sequence of pulse polarities (SPP); 
 generating one or more inter-pulse interference (IPI) reduced samples (IRSs) based at least on the SPP and the CIR that correspond to the FPC; and 
 after the reducing, determining whether the one or more IRSs represent a legitimate transmission of the SPP. 
 
     
     
       9. The method of  claim 8 , wherein the generating the one or more IRSs comprises:
 based on the SPP and the CIR, estimating a subset of the discrete-time samples; 
 estimating interference on the subset of the discrete-time samples from preceding pulses in the SPP; and 
 cancelling the estimated interference from the subset of the discrete-time samples. 
 
     
     
       10. The method of  claim 8 , wherein the determining whether the one or more IRSs represent a legitimate transmission of the SPP comprises:
 estimating a polarity sequence of the one or more IRSs; 
 comparing the estimated polarity sequence with the SPP; and 
 determining whether the comparison satisfies a configurable threshold. 
 
     
     
       11. The method of  claim 10 , wherein the estimating the polarity sequence comprises:
 equalizing the one or more IRSs based on the one or more propagation path coefficients of the FPC; and 
 estimating polarities of the equalized one or more IRSs. 
 
     
     
       12. The method of  claim 8 , wherein the SPP is a cryptographically secure pulse sequence (CSPS) or a training sequence of a physical layer protocol data unit (PPDU). 
     
     
       13. The method of  claim 8 , wherein the determining whether the one or more IRS s represents a legitimate transmission of the SPP comprises:
 computing a correlation between the one or more IRSs and the SPP; 
 computing a sample norm of the one or more IRSs; 
 computing a ratio between a magnitude of the correlation and the sample norm; and 
 determining whether the ratio exceeds a configurable threshold. 
 
     
     
       14. The method of  claim 13 , wherein the sample norm comprises a square-root of a sum of squared magnitudes of the one or more IRSs. 
     
     
       15. A non-transitory computer-readable medium storing instructions that, when executed by a processor of a first electronic device, cause the processor to perform operations, the operations comprising:
 receiving discrete-time samples that correspond to a received wireless transmission; 
 estimating a channel impulse response (CIR) comprising estimates of one or more propagation path coefficients based at least on the discrete-time samples; 
 estimating, based at least on the CIR, a First-Path Candidate (FPC); 
 based at least on the SPP and the CIR, generating one or more inter-pulse interference (IPI) reduced samples (IRSs) that correspond to the FPC; 
 determining, whether the one or more IRSs represent a legitimate transmission of the SPP; and 
 based on the determination that the one or more IRSs represent a legitimate transmission of the SPP, performing a security operation. 
 
     
     
       16. The non-transitory computer-readable medium of  claim 15 , wherein the generating the one or more IRSs operation comprises:
 based at least on the SPP and the CIR, estimating a subset of the discrete-time samples; 
 estimating interference on the subset of the discrete-time samples from preceding pulses in the SPP; and 
 subtracting the estimated interference from the subset of the discrete-time samples. 
 
     
     
       17. The non-transitory computer-readable medium of  claim 15 , wherein the determining whether the one or more IRSs represent a legitimate transmission of the SPP operation comprises:
 estimating a polarity sequence of the one or more IRSs; 
 comparing the estimated polarity sequence with the SPP; and 
 determining whether the comparison satisfies a configurable threshold. 
 
     
     
       18. The non-transitory computer-readable medium of  claim 17 , wherein the estimating the polarity sequence operation comprises:
 equalizing the one or more IRSs based on the one or more propagation path coefficients of the FPC; and 
 estimating polarities of the equalized one or more IRSs. 
 
     
     
       19. The non-transitory computer-readable medium of  claim 15 , wherein the determining whether the one or more IRSs represent a legitimate transmission of the SPP operation comprises:
 computing a correlation between the one or more IRSs and the SPP; 
 computing a sample norm of the one or more IRSs; 
 computing a ratio between a magnitude of the correlation and the sample norm; and 
 determining whether the ratio exceeds a configurable threshold. 
 
     
     
       20. The non-transitory computer-readable medium of  claim 19 , wherein the sample norm comprises a square-root of a sum of squared magnitudes of the one or more IRSs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Application No. 62/812,445, filed on Mar. 1, 2019, entitled, Receiver for Secure Time-of-Arrival Calculation, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     The described embodiments relate generally to wireless communication, including the use of ultra wideband packets. 
     Related Art 
     Ultra-wideband (UWB) systems provide for wireless communication using low power, short range, and moderate data rate pulse streams that spread their energy across a very wide frequency bandwidth. UWB transmissions use a combination of burst position modulation (BPM) and binary phase shift keying (BPSK) to transform binary data into a stream of pulses (the time interval associated with a pulse is also referred to as a chip). The Institute of Electrical and Electronics Engineers (IEEE) 802.15 working group specifies wireless personal area networking (WPAN) standards, including a lower power WPAN communication protocol 802.15.4 that defines data packet formats for various low rate and high rate wireless WPANs. Wireless packet transmissions typically begin with a preamble used for detecting the transmission, acquiring synchronization timing and frequency, adaptively training receiver settings, and estimating a transmission channel. The preamble usually includes a series of repeated predetermined pseudo random (PR) sequences having desired autocorrelation properties. As the PR sequences are known in advance, a receiver can correlate received data to locate the PR sequence and detect the start of a wireless packet transmission. As the set of possible preamble PR sequences used are known and each preamble includes multiple repetitions of a selected PR sequence, a malicious actor may monitor wireless transmissions, detect the PR sequence, and transmit using the detected PR sequence as part of an attempt to spoof a receiver into falsely detecting the malicious actor as a valid transmitter. 
     SUMMARY 
     In some embodiments, a wireless transmission is received and a receiver utilizes channel impulse response (CIR) estimates and a sequence of pulse polarities (SPP), known only to the receiver and the legitimate transmitter, to determine whether the wireless transmission is received is indeed a legitimate transmission of the SPP. If the wireless transmission received is instead a spoofed transmission, then the receiver utilizes CIR estimates and the SPP to determine that the wireless transmission received is not a legitimate transmission. Thus, some embodiments of the disclosure are an improvement over first-path extraction systems because some embodiments can distinguish a legitimate transmission from a spoofed transmission. 
     Some embodiments include an apparatus, method, and computer program product for secure time-of-arrival calculations. For example, some embodiments include obtaining an SPP, receiving a wireless transmission, and estimating a CIR based at least on the wireless transmission received. Some embodiments include identifying one or more First Path Candidates (FPCs), and for each FPC, estimating a location of one or more samples of the wireless transmission that correspond respectively to that FPC of each pulse polarity of the SPP, reducing inter-pulse interference (IPI) from the one or more samples based on the SPP and the estimated CIR to generate one or more IPI reduced samples (IRS), and determining, based at least on the IRS, SPP, and the CIR, whether the wireless transmission is a transmission. 
     To reduce the IPI from the one or more samples, some embodiments can estimate, based at least on the CIR and the SPP, the interference on the one or more samples from previous pulses of the SPP. In some embodiments, the estimated interference can be canceled out of the one or more samples to generate IPI reduced samples (IRS) of an FPC. The IRS of an FPC is then compared with the SPP to determine whether the FPC corresponds to a transmission of the SPP. When the comparison yields a high similarity metric between the IRS and the SPP, the FPC is confirmed as a legitimate transmission; otherwise, the FPC is considered a fake or spoofed transmission. Thus, some embodiments strengthen the physical layer security of first path extraction. 
     In some embodiments, the estimating the received polarity sequence includes equalizing the IRS of an FPC, and determining pulse polarities of the equalized IRS. The SPP can be a cryptographically secure pulse sequence (CSPS) representing a training sequence of a physical layer protocol data unit (PPDU). The PPDU can be an Ultra-wideband (UWB) packet. Note that the terms SPP and CSPS can be used interchangeably in this document. In some embodiments, the comparing of the IRS with the SPP includes computing a correlation between the IRS and the SPP, computing a sample norm of the IRS, and comparing the correlation with the sample norm. The sample norm can be a square-root of a sum of squared magnitudes of the IRS. Further, the comparing the correlation with the sample norm can include computing a ratio between a magnitude of the correlation and a magnitude of the sample norm, and determining whether the ratio computed satisfies (e.g., exceeds) a configurable threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the presented disclosure and, together with the description, further serve to explain the principles of the disclosure and enable a person of skill in the relevant art(s) to make and use the disclosure. 
         FIG. 1A  illustrates an example system implementing receivers for secure time-of-arrival calculations, in accordance with some embodiments of the disclosure. 
         FIG. 1B  illustrates a diagram of an exemplary set of electronic devices with multipath reflection, in accordance with some embodiments of the disclosure. 
         FIG. 1C  illustrates a diagram of an exemplary set of electronic devices with multipath reflection and attenuation, in accordance with some embodiments of the disclosure. 
         FIG. 2A  illustrates a diagram of an exemplary format for a physical layer protocol data unit (PPDU) with no payload, in accordance with some embodiments of the disclosure. 
         FIG. 2B  illustrates a diagram of an exemplary format for a physical layer protocol data unit with a payload, in accordance with some embodiments of the disclosure. 
         FIG. 3A  illustrates a diagram of an example of a malicious actor electronic device interfering with communication between a set of electronic devices, in accordance with some embodiments of the disclosure. 
         FIG. 3B  illustrates a block diagram of an example wireless system with a receiver for secure time-of-arrival calculations, according to some embodiments of the disclosure. 
         FIG. 4  illustrates a receiver block diagram of an example wireless system for secure time-of-arrival calculation, according to some embodiments of the disclosure. 
         FIG. 5  illustrates a method for an example wireless system with a receiver for secure time-of-arrival calculation, according to some embodiments of the disclosure. 
         FIG. 6A  illustrates an estimate of a channel impulse response (CIR) of analog to digital converter (ADC) samples received by an example wireless system, according to some embodiments of the disclosure. 
         FIG. 6B  illustrates a wireless transmission received by an example wireless system, according to some embodiments of the disclosure. 
         FIG. 6C  illustrates first path components and inter-pulse interference (WI) components of a wireless transmission received by an example wireless system, according to some embodiments of the disclosure. 
         FIG. 6D  illustrates first path components after cancellation of inter-pulse interference (IPI) components of a wireless transmission received by an example wireless system, according to some embodiments of the disclosure. 
         FIG. 7  illustrates signals of an example wireless system, with a receiver for secure time-of-arrival calculation, according to some embodiments of the disclosure. 
         FIG. 8  is an example computer system for implementing some embodiments or portion(s) thereof. 
         FIGS. 9A and 9B  illustrate the vulnerability of first-path extraction systems with a malicious actor electronic device interfering with communication between a set of electronic devices at different received power levels. 
     
    
    
     The presented disclosure is described with reference to the accompanying drawings. In the drawings, generally, like reference numbers indicate identical or functionally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
     DETAILED DESCRIPTION 
     Secure ranging in Ultra-wideband (UWB) systems may rely on the exchange of a sequence of pulse polarities (SPP) for time-of-arrival calculations. Pulse polarities are generated by a cryptographically secure pseudo-random number generator, which may be seeded with a different key for every ranging exchange. The key may be known only to the appropriate ranging parties. One approach to secure time-of-arrival calculation is to pass the received SPP through a correlator and extract the first path from the resulting channel impulse response (CIR). But, this opens up the possibility for attackers to create strong contributions to the correlator output at the receiver simply by injecting random energies while adjusting the transmit power, without having to correctly guess the true SPP. The generally desired ability to extract weak first paths gives an attacker even more room to play with power levels. Thus, relying on CIRs alone may be vulnerable to attacks. Some embodiments include a system, method, and computer program product that strengthen the security of physical layer for reception of the SPP. 
     Some embodiments include an apparatus, method, and computer program product for secure time-of-arrival calculations in UWB systems. Some embodiments are directed to a UWB receiver in an electronic device that receives UWB signals from a second electronic device. The UWB receiver can inspect the channel impulse response (CIR) between the first and second electronic devices and identify one or more first path candidates (FPCs) (e.g., based on a non-secure preamble CIR or an SPP CIR). For an FPC, the UWB receiver can identify the samples that correspond to an FPC, as well as paths in the CIR that create inter-pulse interference (IPI) on each sample of the FPC. For example, if the pulses of the SPP are separated by T nanoseconds, then samples of an FPC can have IPI from paths that are multiples of T nanoseconds later than that FPC. Each FPC may have a different set of interfering paths, or even different samples of a single FPC may have IPI from different paths, for example if the pulse spacing is not uniform. Using estimates for the interfering path strengths (e.g., channel coefficients from the CIR) and the known SPP, the UWB receiver can cancel out the IPI from these later paths on an FPC, and then make decisions on pulse polarities. If an FPC for which the fraction of decisions that match the SPP satisfies (e.g., is higher than) a configurable threshold, the UWB receiver can accept that FPC as a first path. The threshold may be determined based factors including, but not limited to the desired level of security (e.g., false alarm probability) and/or the number of pulses in the SPP. 
       FIG. 1A  illustrates an example system  100  implementing receivers for secure time-of-arrival calculations, according to some embodiments of the disclosure. Example system  100  is provided for the purpose of illustration only and is not limiting of the disclosed embodiments. System  100  may include but is not limited to wireless communication devices  190 ,  135 , vehicular transponder device  130 , entry transponder device  140 , ticket entry device  150 , and proximity detection device  160 . Other devices that may benefit from some or all of the embodiments—which are not shown in  FIG. 1  for simplicity purposes—may include other computing devices including but not limited to laptops, desktops, tablets, personal assistants, routers, monitors, televisions, printers, household devices (e.g., thermostat), and appliances. Example uses may include access to a device once in proximity. 
     When wireless communication device  190  is in proximity (e.g., a hundred meters) to vehicular transponder device  130  or entry transponder device  140 , some embodiments may enable a corresponding car door or entry (e.g., entry of a door to a house, an office, or a building) to be unlocked or opened. Likewise, when wireless communication device  190  is in proximity of ticket entry device  150 , some embodiments allow a ticket (e.g., a concert ticket, a metro rail ticket, or a sport event ticket) associated with wireless communication device  190  to be recognized, validated, and allow a ticket holder (via wireless communication device  190 ) entry to the venue. Ticket entry device  150  may include other implementations including but not limited to a turnstile that permits entry, or an automatic gate that unlocks or opens. Proximity detection device  160  may detect a potential customer with wireless communication device  190  near a store front and transmit a promotional coupon or advertisement to wireless communication device  190  to entice the potential customer to visit the store. Likewise, wireless communication device  135  of a first user may recognize when wireless communication device  190  of a second user is in proximity and send an invitation to wireless communication device  190  to invite the second user to meet (e.g., helps friends and family members find each other). In another example (not shown), settings of a household device (e.g., a thermostat) may be adjusted to preferences associated with or stored on wireless communication device  190  as wireless communication device  190  comes into proximity. In another example, a leash tag (not shown) may be a removable device attached to a pet collar or clothing of a wandering toddler where secure communications between the leash tag and wireless communication device  190  result in an alarm notification on wireless communication device  190  when the leash tag exceeds a configurable distance threshold from wireless communication device  190 . 
     The above wireless communication devices can be portable or mobile and can determine relative positions and/or distances with each other. Some wireless devices may be stationary (e.g., proximity detection device  160 ) and may determine absolute positions or geographic locations. 
     In accordance with various embodiments described herein, the terms “wireless communication device,” “wireless device,” “mobile device,” “mobile station,” and “user equipment” (UE) may be used interchangeably herein to describe one or more common consumer electronic devices that may be capable of performing procedures associated with various embodiments of the disclosure. In accordance with various implementations, any one of these consumer electronic devices may relate to: a cellular phone or a smart phone, a tablet computer, a laptop computer, a notebook computer, a personal computer, a netbook computer, a media player device, an electronic book device, a MiFi® device, a wearable computing device, as well as any other type of electronic computing device having wireless communication capability that can include communication via one or more wireless communication protocols such as used for communication on: a wireless wide area network (WWAN), a wireless metro area network (WMAN) a wireless local area network (WLAN), a wireless personal area network (WPAN), a near field communication (NFC), a cellular wireless network, a fourth generation (4G) Long Term Evolution (LTE), LTE Advanced (LTE-A), and/or fifth generation (5G) or other present or future developed advanced cellular wireless networks. 
     The wireless communication device, in some embodiments, can also operate as part of a wireless communication system, which can include a set of client devices, which can also be referred to as stations, client wireless devices, or client wireless communication devices, interconnected to an access point (AP), e.g., as part of a WLAN, and/or to each other, e.g., as part of a WPAN and/or an “ad hoc” wireless network. In some embodiments, the client device can be any wireless communication device that is capable of communicating via a WLAN technology, e.g., in accordance with a wireless local area network communication protocol. In some embodiments, the WLAN technology can include a Wi-Fi (or more generically a WLAN) wireless communication subsystem or radio, the Wi-Fi radio can implement an Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology, such as one or more of: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012; IEEE 802.11ac; or other present or future developed IEEE 802.11 technologies. 
     Additionally, it should be understood that the UEs described herein may be configured as multi-mode wireless communication devices that are also capable of communicating via different third generation (3G) and/or second generation (2G) RATs. In these scenarios, a multi-mode UE can be configured to prefer attachment to LTE networks offering faster data rate throughput, as compared to other 3G legacy networks offering lower data rate throughputs. For instance, in some implementations, a multi-mode UE may be configured to fall back to a 3G legacy network, e.g., an Evolved High Speed Packet Access (HSPA+) network or a Code Division Multiple Access (CDMA) 2000 Evolution-Data Only (EV-DO) network, when LTE and LTE-A networks are otherwise unavailable. 
       FIG. 3B  illustrates a block diagram of an example wireless system  350  with a receiver (e.g., within transceiver  320 ) for secure time-of-arrival calculations, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG. 3B , may be described with elements of  FIGS. 1A, 1B, and 1C . System  350  may be any of the devices (e.g.,  130 ,  135 ,  140 ,  150 ,  160 , and/or  190 ) of system  100 . System  350  may include processor  310 , transceiver  320 , communication infrastructure  330 , memory  335 , and antenna  325  that together perform operations enabling wireless communications including secure channel estimation. Transceiver  320  transmits and receives communications signals including PPDU (e.g., PPDU  210  or  260 ) for secure channel estimation according to some embodiments, and may be coupled to antenna  325 . Communication infrastructure  330  may be a bus. Memory  335  may include random access memory (RAM) and/or cache, and may include control logic (e.g., computer software) and/or data. Antenna  325  coupled to transceiver  320 , may include one or more antennas that may be the same or different types. 
       FIG. 1B  illustrates a diagram  110  of an exemplary set of electronic devices  102 ,  104  with multi-path reflection. In this example, electronic devices  102  and  104  can be any two devices of system  100  of  FIG. 1A  such as wireless communication device  190  and ticket entry device  150 . Electronic device  102  may send a transmission, e.g., one or more wireless packets, using wireless subsystem  106 - 1  to electronic device  104 , which receives the transmission using wireless subsystem  106 - 2 . Wireless subsystems  106 - 1  and  106 - 2  may include a system  350  of  FIG. 3B  to implement the wireless transmission. The transmission may traverse a direct path  111 , which may represent a shortest distance path, from electronic device  102  to electronic device  104 . The transmission may also traverse an indirect path  112  from electronic device  102  to electronic device  104 , which may represent a longer distance path due to an echo from a reflective surface  108 . While there may be any number of propagation paths, with any combination of strong and weak path strengths, the two-path description that follows is chosen for the sake of simplicity and is notmeant to be limiting. Electronic device  104  can correlate pre-determined sequences included in the transmission to estimate a channel impulse response (CIR)  114  based on received samples that include a combination of the transmissions via direct path  111  and indirect path  112 . Channel impulse response  114  can include a stronger direct path peak  116  and a weaker indirect path peak  118 . Electronic device  104  can use the estimated channel impulse response  114  to estimate a distance between electronic device  102  and electronic device  104 , which can also be referred to as wireless ranging. For wireless ranging, the second electronic device  104  must distinguish between different peaks in the estimated channel impulse response  114  to locate direct path  111  and also separate the channel impulse response from ambient noise to accurately determine the distance between electronic devices  102  and  104 . 
       FIG. 1C  illustrates a diagram  120  of an exemplary set of electronic devices  102  and  104  with both multipath reflection and attenuation. Electronic device  102  may send a transmission using the wireless subsystem  106 - 1  to electronic device  104 , which receives the transmission using the wireless subsystem  106 - 2 . The transmission may traverse attenuated direct path  122 , which represents the shortest distance path between electronic devices  102  and  104 . But, the signal received via attenuated direct path  122  may be attenuated by attenuating object  122  (e.g., a structure like furniture or a wall), thereby reducing the total energy received via attenuated direct path  122 . The transmission may also traverse indirect path  112  and be received by the second electronic device  104  later than via the attenuated direct path  122 . The resulting channel impulse response  124  estimated by electronic device  104  can include a weaker direct path peak  126  and a stronger indirect path peak  128 . A noted hereinabove, there may be any number of propagation paths, some stronger and some weaker resulting in an estimated channel impulse response (CIR) having multiple peaks, and the estimated CIR  124  shown in  FIG. 1C  is exemplary but not limiting. Electronic device  104  may still distinguish between the peaks, however, direct path peak  126  of  FIG. 1C  can have a reduced signal strength that may be more difficult to separate from receiver noise and other signal distortion phenomena than the direct path peak  116  of  FIG. 1B . 
     As a convenience and not a limitation,  FIGS. 2A and 2B , may be described with elements of  FIGS. 1A, 1B, 1C, and 3B .  FIG. 2A  illustrates a diagram  200  of an exemplary format for a physical layer protocol data unit (PPDU)  210  with no payload, in accordance with some embodiments of the disclosure. PPDU  210  (e.g., a UWB packet) may be transmitted when a secure time-of-arrival calculation (e.g., secure distance measurement) is desired. PPDU  210  includes a preamble  202  which can include a repeated series of pseudo random sequences followed by start of frame delimiter (SFD)  204  separating preamble  202  from SPP field  206 . SPP field  206  can include for example, 4096 pulses with a pulse repetition period, T, where T=16 ns. 
       FIG. 2B  illustrates a diagram  250  of an exemplary format for a PPDU  260  with a payload, in accordance with some embodiments of the disclosure. PPDU  260  may be transmitted when data transfer is also desired in addition to secure time-of-arrival calculation. PPDU  260  includes a preamble  202  followed by SFD  204  separating preamble  202  from SPP field  206 . PPDU  260  can include physical layer header (PHR)  258  and physical service data unit (PSDU)  270  that includes data. 
     The accuracy of a channel impulse response (CIR) estimation by electronic devices  102  and  104  can depend on the use of known sequences having desired auto correlation properties. A pseudo random (PR) sequence having a perfect autocorrelation property can produce a positive result with perfect alignment and zero results for all shifted alignments. Known finite length PR sequences having perfect autocorrelation may be included in preambles of wireless transmission packets, where the PR sequence may be repeated several times to aid detection for the start of a wireless transmission packet (e.g., PPDU  210  or PPDU  260 ) by a receiver, e.g., by the wireless subsystem  106 - 2  of electronic device  104 . As the PR sequence used for the preamble  202  and/or pulses of SPP field  206  are known, the wireless subsystem  106 - 2  of electronic device  104  can readily receive and detect the start of a wireless transmission packet. But, as described in  FIG. 3A  below, other electronic devices may also listen for and detect the same wireless transmission packet and may interfere with proper detection by electronic device  104 . 
       FIG. 3A  illustrates a diagram  300  of an example of a malicious actor electronic device  302  interfering with communication between a set of electronic devices  102  and  104 . As a convenience and not a limitation,  FIG. 3A  may be described with elements of  FIGS. 1A, 1B, 1C, 2A, 2B, and 3B . In the example, electronic device  102  sends legitimate transmission  304  to electronic device  104 . Malicious actor electronic device  302  may receive a sniffed transmission  306 , such as a portion of legitimate transmission  304 , and after recognizing a PR sequence used for preamble  202  or recognizing portions of SPP field  206  of legitimate transmission  304 , may send spoofed transmission  308  to electronic device  104  reusing the PR sequence or portions of SPP field  206  to potentially cause electronic device  104  to incorrectly recognize malicious actor electronic device  302  as the legitimate transmitter instead of electronic device  102 . When that occurs, electronic device  104  can determine an incorrect time-of-arrival and an incorrect distance between electronic device  102  and electronic device  104 . The impact of the incorrect distance can be demonstrated with regard to system  100  of  FIG. 1A . If the incorrect distance was determined between wireless communication device  190  and ticket entry device  150 , ticket entry device  150  may open too early and/or close too early and a user of wireless communication device  190  may not be able to gain entry as desired and intended. And, a user of malicious actor electronic device  302  may be able to gain entry through ticket entry device  150 . 
     In some attacks, malicious actor electronic device  302  can react quickly during the preamble transmission from electronic device  102  to electronic device  104  by injecting to the wireless medium a malicious actor preamble signal, using preamble intervals that are identical to those transmitted by electronic device  102  such that spoofed transmission  308  received at electronic device  104  appears time-advanced relative to legitimate transmission  304  received at electronic device  104 . When such malicious actor preamble signals are used for wireless ranging, electronic device  104  may erroneously determine that malicious actor electronic device  302  is the closest (based on the timing advance), legitimate (based on the known PR sequence or SPP) electronic device, based on channel impulse response (CIR) estimation at a physical layer. 
       FIGS. 9A and 9B  illustrate the vulnerability of first-path extraction systems with a malicious actor electronic device  302  interfering with communication between a set of electronic devices  102  and  104 . As a convenience and not a limitation,  FIGS. 9A and 9B  may be described with elements from previous figures. CIR estimation  900  illustrates that a first-path extraction system that relies only on CIR estimation (based either on the known PR sequence or the SPP) for a secure time-of-arrival calculation can be fooled by spoofed transmission  308  of  FIG. 3A  that can show up as the fake first path compared to a legitimate first path that arrives at a later time. When a receiver of electronic device  104  receives spoofed transmission  308 , electronic device  104  may use the fake first path to determine the time-of-arrival calculation and thus calculate an incorrect distance between electronic device  102  and itself, electronic device  104 . And, if electronic device  102  is for example, wireless communication device  190  of system  100  in  FIG. 1A , and electronic device  104  is any of the other electronic devices of system  100 , then the applications may not have the desired effects as described above. CIR estimation  950  illustrates a similar result at a different received power level. To address the vulnerability of first-path extraction systems, some embodiments include an apparatus, method, and computer program product for secure time-of-arrival calculations such as UWB systems. 
       FIG. 4  illustrates a receiver block diagram of an example wireless system  400  for secure time-of-arrival calculation, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG. 4  may be described with elements from previous figures. For example, wireless system  400  may be implemented by wireless system  350  of  FIG. 3B , with antenna  325 , and processor  310 . Wireless system  400  can be any electronic device of system  100  of  FIG. 1 . As an example, and not a limitation, wireless system  400  can be that of electronic device  104  of  FIG. 3A . Some embodiments rely on a known periodic sequence which may be based on the preamble  202  or SPP field  206  of  FIG. 2A or 2B . For convenience and not a limitation, the examples herein utilize SPP field  206  that includes for example, 4096 pulses with a pulse repetition period, T, where T=16 ns. 
       FIG. 4  illustrates a receiver block diagram of electronic device  104  that determines whether a received transmission is legitimate transmission  304  or spoofed transmission  308 . Wireless system  400  a utilizes channel impulse response (CIR) estimates based on a known sequence as well as the SPP affiliated with legitimate transmission  304  to verify that the wireless transmission received is indeed legitimate transmission  304 . If for example, the wireless transmission received is actually spoofed transmission  308 , then the processes of wireless system  400  that utilize CIR estimates as well as the SPP affiliated with legitimate transmission  304  can determine that the wireless transmission received is not legitimate transmission  304 . Thus, some embodiments of the disclosure are an improvement over first-path extraction systems of  FIGS. 9A and 9B  because some embodiments can distinguish legitimate transmission  304  received from spoofed transmission  308  received. 
     Wireless receiver system  400  includes radio  410 , channel impulse response (CIR) FPC estimator  420 , inter-pulse interference (IPI) canceller  430 , polarity detector  440 , SPP  470 , error counter  450 , and threshold  460 . Radio  410  receives (a) transmission such as an RF signal, via one or more antennas and converts the RF signal to (b) discrete-time samples. CIR FPC estimator  420  receives (b) discrete-time samples, and determines (c) CIR, FPC, and inter pulse interference (IPI) information that can include channel coefficient and timing estimates that identify a CIR including estimates of one or more propagation paths including FPCs and subsequent reflected paths (e.g., IPI components) as shown in  FIG. 6B .) The IPI components can be spaced from the FPCs by multiples of T, the temporal distances between pulses in the transmitted SPP field  206 . Thus, (c) CIR, FPC, and IPI information identify the IPI components at multiples of T. SPP  470  generates (d) SPP pulse polarities that are known to both the transmitting electronic device (e.g., electronic device  102 ) and the receiving electronic device (e.g., electronic device  104 ). 
     IPI canceller  430  uses (c) CIR, FPC, and IPI information to remove from FPCs, respective IPI components at multiples of T based on (d) SPP field  206 , from (b) discrete-time samples. Thus, IPI canceller  430  yields (e) IPI-reduced samples (IRSs) on FPCs. 
     Polarity detector  440  uses (c) CIR, FPC, and IPI information (e.g., the first path channel coefficient estimate) to perform bit detection for each sample of the (e) IRSs. For example, polarity detector  440  can estimate a polarity sequence. Polarity detector  440  yields (t) decisions on pulse polarities at multiples of T. 
     Error counter  450  compares the (t) decisions on pulse polarities (e.g., estimated bit values) with (d) SPP field  206 , and yields (g) the number of polarity errors. 
     Threshold  460  compares whether or not (g) the number of polarity errors are considered a match with SPP field  206 . For example, threshold  460  determines whether (g) the number of polarity errors satisfies a configurable threshold value (e.g., below a given bit error rate (BER) and is considered a match, or exceeds a given BER and is not considered a match). Threshold  460  yields (h) an accepted or rejected first path (e.g., accepts the received wireless transmission at (a) as legitimate transmission  304  or rejects the received wireless transmission at (a) as a not being legitimate transmission  304  (e.g., as spoofed transmission  308 .) 
       FIG. 5  illustrates method  500  for an example wireless system  400  with a receiver for secure time-of-arrival calculation, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG. 5 , may be described with elements from previous figures. Method  500  may be performed by wireless system  350  of  FIG. 3B  and any electronic devices of system  100  of  FIG. 1A . 
     At  502 , method  500  receives discrete-time samples representing a UWB transmission of SPP field  206 . 
     At  505 , method  500  extracts a channel impulse response (CIR) from the received discrete-time samples. For example, a processor performing CIR FPC estimator  420  functions can receive discrete-time samples and estimate the CIR. 
     At  510 , method  500  estimates a FPC of each pulse polarity in the SPP (e.g., using timing and coefficients of the CIR.) 
     At  515 , method  500  estimates a location of one or more samples that correspond to the FPC of each pulse polarity in the SPP (e.g., use timing and coefficient of paths that create IPI components such as second path components and/or reflected path components on subsequent FPCs.) 
     At  520 , method  500  reduces IPI on the one or more samples based at least on the SPP and the CIR (e.g., utilizes pulse locations at multiples of T of SPP field  206 ) to cancel out IPI components from discrete-timing samples received, where the discrete-timing samples include first path components and IPI components that correspond to the location of pulses at multiples of T of the SPP.) The result of cancelling the IPI components yields IRSs (e.g., IPI-free samples) received on first paths located at multiples of T. In other words, method  500  generates one or more IPI reduced samples (IRS) that correspond to the FPC of each pulse polarity in the SPP. 
     At  525 , method  500  makes decisions on pulse polarities (e.g., by using first path channel coefficient estimates to equalize the IRSs received on first paths located at multiples of T.) The channel equalization may include phase rotations of the IPI-free samples received on first paths. The output of the channel equalization performed by a processor performing polarity detector  440  functions, are estimated bit values. 
     At  530 , method  500  compares the estimated bit values with the SPP polarities. 
     At  535 , method  500  counts the number of errors based on the comparison at  530 . 
     At  540 , method  500  determines whether the number of errors counted satisfies a threshold. For example, a determination is made whether the number of errors counted is less than a configurable threshold value (e.g., a BER). When the number of errors counted is less than the configurable threshold value, method  500  proceeds to  545 . When the number of errors counted is greater than the configurable threshold value, method  500  proceeds to  550 . 
     At  545 , method  500  accepts the discrete-time samples as a transmission of SPP field  206  (e.g., as legitimate transmission  304 .) 
     At  547 , method  500  initiates a security operation using the accepted discrete-time samples. For example, as shown in  FIG. 1A , entry transponder device  140  enables a car door (e.g., unlocks or opens a vehicle door), entry to a building, or ticket entry device  150  allows a ticket that enables entry to a venue. Other security operations are possible. 
     At  550 , method  500  rejects the discrete-time samples as not being a transmission of SPP field  206  (e.g., as spoofed transmission  308 .) 
       FIGS. 6A-6D  illustrates signals associated with  FIG. 4 . For example,  FIG. 6A  illustrates the output of channel estimator  420 ;  FIG. 6B  illustrates the output signal of radio  410 ;  FIG. 6C  illustrates components that make up the output signal of radio  410 ; and  FIG. 6D  illustrates the output of IPI canceller  430 . As a convenience and not a limitation,  FIGS. 6A-6D  may be described with elements from previous figures. 
       FIG. 6A  illustrates an estimate of a channel impulse response (CIR)  600  (e.g., (c) channel coefficient and timing estimates) of (b) ADC samples received by an example wireless system  400 , according to some embodiments of the disclosure. CIR estimate  600  identifies a first path candidate  605  and a reflection of first path candidate  605 ,  605 R 1 , at multiples of T, the temporal distances between pulses in the transmitted SPP field  206 . While other signals  615  are identified, they are ignored because they are not located at a location that is a multiple of T. Recall that the period, T, is determined when the known sequence SPP field  206  is selected. Although only the first path candidate  605  and the reflection of first path candidate  605 , namely  605 R 1 , are shown (c) channel coefficient and timing estimates are assumed to also identify the IPI components at multiples of T (e.g.,  632 R 1 ,  634 R 1 , . . .  642 R 1 ,  644 R 1 , and  646 R 1  of  FIG. 6C ) that are spaced by multiples of T which are described below with regard to  FIGS. 6B and 6C . 
       FIG. 6B  illustrates a wireless transmission  630  received by an example wireless system  400 , according to some embodiments of the disclosure. The one or more samples shown in wireless transmission  630  includes signals  622 ,  624 ,  626 , . . .  654 ,  656 ,  658  and so on which are a subset of (b) discrete-time samples of  FIG. 4  that are identified using (c) CIR, FPC, and IPI information of  FIG. 4 . Some embodiments first assume that the signals of wireless transmission  630  include FPCs of each pulse polarity of SPP field  206  superimposed with (e.g., added with) inter-pulse interference (IPI) components of earlier pulses at that location (e.g., multiple of T). While there may be many reflected paths that contribute to the IPI components, for convenience and not a limitation, examples herein describe the IPI from reflected second path components. 
       FIG. 6C  illustrates first path components and inter-pulse interference (WI) components of a wireless transmission  650  received by an example wireless system  400 , according to some embodiments of the disclosure. For example, signal  622  of  FIG. 6B  is assumed to be the First-Path Candidate (FPC) of legitimate transmission  304  and is shown as a first path of pulse  632  of  FIG. 6C . Signal  624  of  FIG. 6B  is assumed to include a superposition of a first path of pulse  634  plus the WI component (e.g., interference) due to a reflection of pulse  632 ,  632 R 1  component, at that location shown in  FIG. 6C . In other words,  632 R 1  component is assumed to be a second path reflection of pulse  632 . Note that first path of pulse  634  has a negative polarity while  632 R 1  component with a stronger receive signal has a positive polarity, and the superposition yields a signal  624  of a positive polarity at that location in  FIG. 6B . Signal  626  of  FIG. 6B  is assumed to include first path of pulse  636  superpositioned with a reflection of pulse  634 ,  634 R 1  component. Since both first path of pulse  636  and  634 R 1  component have negative polarities, their superposition is assumed to yield a negative polarity shown as signal  626  of  FIG. 6B . Similarly, signal  654  of  FIG. 6B  is assumed to include first path of pulse  644  superpositioned with a reflection of pulse  642 ,  642 R 1  component. Signal  656  of  FIG. 6B  is assumed to include first path of pulse  646  superpositioned with a reflection of pulse  644 ,  644 R 1  component. Signal  658  of  FIG. 6B  is assumed to include first path of pulse  648  superpositioned with a reflection of pulse  646 ,  646 R 1  component. 
       FIG. 6D  illustrates first path components  660  after cancellation of IPI components of a wireless transmission received by an example wireless system, according to some embodiments of the disclosure, (e) IRSs. Thus, the (c) CIR, FPC, and IPI information are assumed to identify the IPI components at multiples of T (e.g.,  632 R 1 ,  634 R 1 , . . .  642 R 1 ,  644 R 1 , and  646 R 1  of  FIG. 6C ) that are spaced by multiples of T which are described below with regard to  FIGS. 6B and 6C . When (a) received RF signal is indeed legitimate transmission  304 , first path components  660  can be substantially equivalent to the SPP (e.g., SPP field  206 ) as shown in this example. Polarity detector  440 , error counter  450 , and threshold  460  functions together confirm the substantial equivalence. When (a) received RF signal is actually not legitimate transmission  304  (e.g., is spoofed transmission  308 ), first path components  660  can be different from the known SPP (e.g., SPP field  206 .) In some embodiments, polar detector  440 , error counter  450 , and threshold  460  functions together confirm the difference and some embodiments would reject (a) received RF signal as a false signal such as detected spoofed transmission  308 . 
       FIG. 7  illustrates signals  700  of an example wireless system  700 , with a receiver for secure time-of-arrival calculation, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG. 7  may be described with elements from previous figures. Wireless system  700  can include transmitters and receivers. The electronic devices that transmit as well as the electronic devices that receive may be wireless system  350  of  FIG. 3B  and any electronic devices of system  100  of  FIG. 1A . The receiver functions may be performed by wireless system  400  of  FIG. 4 . 
     An electronic device transmits signal  705 , namely x(t), at time, t=0. In an example, x(t) can be a transmitted training signal such as SPP field  206 . 
     After a delay at t=τ 1 , signal  710 , a weak first path signal traverses the channel; the weak first path signal is characterized as y 1 (t)=h 1 x(t−τ 1 ). 
     After another delay at t=τ 2 , signal  715 , a strong second path signal such as IPI signals also traverse the channel, where τ 2 =τ 1 +T, where T is the pulse repetition period; the strong second path signal is characterized as y 2 (t)=h 2 x(t−τ 2 ). While other paths of the channel impulse response may exist, for convenience, they are not shown here. 
     Signal  720  includes y(t) that is equivalent to (b) discrete-time samples of  FIG. 4 . Radio  410  of  FIG. 4  receives a noisy analog signal and at time t, yields a noisy sampled signal characterized as y(t)=y 1 (t)+y 2 (t)+z(t). Note that for simplicity, a continuous time notation is used for signals in this and subsequent paragraphs, indicated by the notation “(t)” for the time t at which the respective signal is evaluated. In a practical state of the art system, however, the time at which signals are observed and processed will be quantized such that t=Ts*n, where t is Ts is the sampling interval and n is the discrete time index. In what follows, it is understood that signal t refers to a sequence of discrete time instances. 
     IPI canceller  430  functions of  FIG. 4  can be performed by a processor (e.g., processor  310  of  FIG. 4 ) that estimates and cancels the strong second path signal using the CIR and SPP. 
     The resulting signal  725  can be characterized as: a(t)=y(t)−ĥ 2 x (t−{circumflex over (τ)} 2 )+z(t), which can be equivalent to (e) IRSs of  FIG. 4 . 
     Polarity detector  440  functions of  FIG. 4  can be performed by a processor (e.g., processor  310  of  FIG. 4 ) that equalizes the resulting signal to produce signal  730 . Signal  730  which can be characterized as
 
 b ( t )= ĥ   1   a ( t )+ z ( t ).
 
     Polarity detector  440  functions of  FIG. 4  can be performed by a processor (e.g., processor  310  of  FIG. 4 ) that also determines whether the pulse polarities are positive or negative, and then compares the determined pulse polarities with the known SPP to determine whether received noisy signal  720  was the legitimate expected transmission (e.g., legitimate transmission  304 ) or not. The result of the determination signal  735  can be characterized as:
 
sign[ b ( Tk )]?=sign[ x ( Tk )] k= 0, . . . ,  N− 1.
 
     For example, based on the comparison and the number of errors (e.g., bit error rate (BER)) being less than a given threshold value, received noisy signal  720  is considered to be legitimate transmission  304  of  FIG. 3A  (e.g., not a spoofed transmission  308 .) In this example, the transmission x(t) is a legitimate transmission  304  of  FIG. 3A , and x(t) is a transmission of SPP field  206 . 
     In some embodiments, the determination whether the wireless transmission is from the legitimate transmitter can be based on the concept of a normalized correlation. Specifically, a correlation metric between signal a(t) and the SPP can be utilized, where correlation refers to an inner vector product, computed by conducting pairwise multiplication of samples of a(t) with corresponding polarity values in the SPP and summing up the results of this multiplication over the entirely of the SPP. The normalization starts by computing the sample norm of a(t), which comprises computing the squared magnitude |a(t)|{circumflex over ( )}2 of each sample in a(t) and computing the average of this metric over all samples in a(t). Finally, to arrive at the normalized correlation, a ratio is calculated between the absolute value of the correlation (or inner product) and the sample norm. To determine whether the wireless transmission is legitimate, that is indeed a transmission of the expected SPP, the normalization correlation is compared to a configurable threshold. 
     Various embodiments can be implemented, for example, using one or more computer systems, such as computer system  800  shown in  FIG. 8 . Computer system  800  can be any well-known computer capable of performing the functions described herein. For example, and without limitation, electronic devices such as laptops, desktops as described with regard to  FIG. 1A  and/or other apparatuses and/or components shown in the figures. The laptops and desktops or other wireless devices may include the functions as shown in system  350  of  FIG. 3B  and/or some or all of method  500  of  FIG. 5 , and wireless system  400  of  FIGS. 4 and 7  respectively. For example, computer system  800  can be used in wireless devices to exchange UWB packet structures that enable secure time-of-arrival calculation between wireless devices. 
     Computer system  800  includes one or more processors (also called central processing units, or CPUs), such as a processor  804 . Processor  804  is connected to a communication infrastructure or bus  806 . Computer system  800  also includes user input/output device(s)  803 , such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure  806  through user input/output interface(s)  802 . Computer system  800  also includes a main or primary memory  808 , such as random access memory (RAM). Main memory  808  may include one or more levels of cache. Main memory  808  has stored therein control logic (e.g., computer software) and/or data. 
     Computer system  800  may also include one or more secondary storage devices or memory  810 . Secondary memory  810  may include, for example, a hard disk drive  812  and/or a removable storage device or drive  814 . Removable storage drive  814  may be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and/or any other storage device/drive. 
     Removable storage drive  814  may interact with a removable storage unit  818 . Removable storage unit  818  includes a computer usable or readable storage device having stored thereon computer software (control logic) and/or data. Removable storage unit  818  may be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and/any other computer data storage device. Removable storage drive  814  reads from and/or writes to removable storage unit  818  in a well-known manner. 
     According to some embodiments, secondary memory  810  may include other means, instrumentalities or other approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system  800 . Such means, instrumentalities or other approaches may include, for example, a removable storage unit  822  and an interface  820 . Examples of the removable storage unit  822  and the interface  820  may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface. 
     Computer system  800  may further include a communication or network interface  824 . Communication interface  824  enables computer system  800  to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference number  828 ). For example, communication interface  824  may allow computer system  800  to communicate with remote devices  828  over communications path  826 , which may be wired and/or wireless, and which may include any combination of LANs, WANs, the Internet, etc. Control logic and/or data may be transmitted to and from computer system  800  via communication path  826 . 
     The operations in the preceding embodiments can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding embodiments may be performed in hardware, in software or both. In some embodiments, a tangible apparatus or article of manufacture includes a tangible computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system  800 , main memory  808 , secondary memory  810  and removable storage units  818  and  822 , as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system  800 ), causes such data processing devices to operate as described herein. 
     Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use embodiments of the disclosure using data processing devices, computer systems and/or computer architectures other than that shown in  FIG. 8 . In particular, embodiments may operate with software, hardware, and/or operating system implementations other than those described herein. 
     It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the disclosure as contemplated by the inventor(s), and thus, are not intended to limit the disclosure or the appended claims in any way. 
     While the disclosure has been described herein with reference to exemplary embodiments for exemplary fields and applications, it should be understood that the disclosure is not limited thereto. Other embodiments and modifications thereto are possible, and are within the scope and spirit of the disclosure. For example, and without limiting the generality of this paragraph, embodiments are not limited to the software, hardware, firmware, and/or entities illustrated in the figures and/or described herein. Further, embodiments (whether or not explicitly described herein) have significant utility to fields and applications beyond the examples described herein. 
     Embodiments have been described herein with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined as long as the specified functions and relationships (or equivalents thereof) are appropriately performed. In addition, alternative embodiments may perform functional blocks, steps, operations, methods, etc. using orderings different from those described herein. 
     References herein to “one embodiment,” “an embodiment,” “an example embodiment,” or similar phrases, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of persons skilled in the relevant art(s) to incorporate such feature, structure, or characteristic into other embodiments whether or not explicitly mentioned or described herein. 
     The breadth and scope of the disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Metadata:
Filing Date: 20200228
Publication Date: 20210105
Grant Date: 20210105
Priority Date: 20190301
Inventors: SASOGLU, Eren
HAMMERSCHMIDT, JOACHIM S.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W4/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/029", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W4/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L25/0212", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W4/029", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L25/0224", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W64/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W4/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L25/0212", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L25/03012", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/029", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W64/006", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L25/0212", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/80", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 72236784