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EP-3571785-B1 - MILLIMETER- WAVE COMMUNICATION SYSTEM AND METHOD FOR DETERMINING LOCATION OF FIRST DEVICE BASED ON KNOWN LOCATION OF SECOND DEVICE

EP3571785B1EP 3571785 B1EP3571785 B1EP 3571785B1EP-3571785-B1

Inventors

  • PAJOVIC, Milutin
  • AKINO, TOSHIAKI
  • ORLIK, PHILIP

Dates

Publication Date
20260513
Application Date
20181012

Claims (13)

  1. A millimeter-wave, mmWave, communication system for determining a location (704) of a first device (101) based on a known location of a second device (102), comprising: a transceiver (201, 202) connected to a set of antennas (203, 204) to communicate beams (205, 206) of mmWaves and to perform an estimation of a channel connecting the first device (101) and the second device (102) by comparing energy of beams communicated using mmWave beamforming over a set of beamforming angles, wherein neighboring beamforming angles in the set of beamforming angles are separated according to a resolution of the beamforming; a memory (303) to store results of the channels estimation including pairs of beam values (601), wherein each pair of beam values (601) includes a beamforming angle (611) and an energy (612) of the beam communicated with the beamforming angle (611); and a processor (701) operatively connected to the memory (303) and configured to select from the memory (303) multiple pairs of beam values (601) corresponding to beamforming communication sharing the same dominant path (901, 1650) connecting the first device (101) and the second device (102); determine a direction (703) of the dominant path (901, 1650) by evaluating a beamforming model (702) for the selected pairs of beam values (601), wherein the beamforming model (702) relates a deviation of a beamforming angle, caused by the resolution of the beamforming, from the dominant path (901, 1650) with the energy of the beam transmitted with the beamforming angle and received over the dominant path (901, 1650); and determine the location (704) of the first device (101) arranged along the direction (703) of the dominant path (901, 1650) with respect to the location of the second device (102); wherein the beamforming model (702) relates the deviation of the beamforming angle from the dominant path (901, 1650) to the energy of the beam and an unknown distance between transceivers (201, 202) performing the beamforming, such that the beamforming model (702) includes an ambiguity in the direction (703) of the dominant path (901, 1650) resolved by the processor (701) with the selected multiple pairs of beam values (601); wherein the set of antennas (203, 204) is a vertical line phased array including N antenna elements that are equally spaced at d = λ /2 , where λ = c / f is the wavelength, given as the ratio between the wave speed c and the carrier frequency f ; and wherein the processor (701) is configured to obtain the direction (703) of the dominant path (901, 1650) given as the angle θ 1 it encloses with a vertical line pointing upwards (905) by solving the equation z 1 z 2 = sin Nπ cosθ 1 − cos β / 2 sin π cosθ 1 − cos γ / 2 sin Nπ cosθ 1 − cos γ / 2 sin π cosθ 1 − cos β / 2 , where a received signal magnitude when steering towards a centering direction (911) of a beam (910) is z 1 , a magnitude of a received pilot signal when steering towards a centering direction (921) of a further beam (920) is z 2 , β and γ denote angles which the centering directions (911, 921), respectively, enclose with the vertical line pointing upwards (905).
  2. The communication system of claim 1, wherein the processor (701) determines a distance between the first and the second devices (101, 102), and determines the location (704) of the first device (101) based on the distance along the direction (703) of the dominant path (901, 1650).
  3. The communication system of claim 2, wherein the processor (701) obtains a time-of-flight of propagation of the beam over the dominant path (901, 1650) and determines the distance between the first and the second devices (101, 102) based on the time-of-flight.
  4. The communication system of claim 3, further comprising: a sensor to measure the time-of-flight.
  5. The communication system of claim 2, wherein the processor (701) determines the distance using a path-loss model of mmWave signal propagation along the direction of the dominant path (901, 1650) with the energy of the beam transmitted with the beamforming angle closest to the direction (703) of the dominant path (901, 1650).
  6. The communication system of claim 2, wherein the processor (701) checks whether the dominant path (901, 1650) connects the first and the second devices (101, 102) via a direct line of sight using a path-loss model of mmWave signal propagation along the distance traveled over the direction (703) of the dominant path (901, 1650); determines the location at the distance from the second device (102) along the direction (703) of the dominant path (901, 1650) when the dominant path (901, 1650) connects the first and the second devices (101, 102) via the direct line of sight; and otherwise determines a reflection of the dominant path (901, 1650) using a map (1520) of environment surrounding the first and the second devices (101, 102) and adjusts the location (704) of the first device (101) according to the reflection.
  7. The communication system of claim 1, wherein the processor (701) is configured to select from the memory (303) multiple sets of pairs of beam values (601) such that pairs of beam values (601) from different sets use different dominant paths (901, 1650) of the beamformed communication; determine the dominant path (901, 1650) for each set of pairs of beam values (601) to produce a set of dominant paths (901, 1650); and triangulate the dominant paths (901, 1650) originating at the location of the second device (102) to produce the location (704) of the first device (101).
  8. The communication system of claim 1, wherein the first and the second devices (101, 102) perform the channel estimation using a physical layer of a communication protocol and store the results of the channel estimation in a medium access control, MAC, layer (1705) of the communication protocol, and wherein the processor (701) determines the direction (703) of the dominant path (901, 1650) only using information retrieved from the MAC layer (1705).
  9. The communication system of claim 1, wherein the second device (102) is an access point, AP, connecting the first device (101) to a network.
  10. The communication system of claim 1, wherein transceivers (201, 202) communicate data between the first device (101) and the second device (201) using a beam with the beamforming angle determined during the channel estimation.
  11. The communication system of claim 1, wherein transceivers (201, 202) communicate data between the first device (101) and the second device (102) using a beam with the beamforming angle along the direction (703) of the dominant path (901, 1650).
  12. A method for determining a location (704) of a first device (101) based on a known location of a second device (102) using millimeter-wave, mmWave, beamforming, wherein the method uses a processor (701) coupled with stored instructions implementing the method, wherein the instructions, when executed by the processor (701) carry steps of the method comprising: estimating a channel connecting the first device (101) and the second device (102) by comparing energy of beams communicated using the mmWave beamforming over a set of beamforming angles separated according to a resolution of the beamforming to produce results of the channels estimation including pairs of beam values (601), wherein neighboring beamforming angles in the set of beamforming angles are separated according to a resolution of the beamforming, and wherein each pair of beam values (601) includes a beamforming angle (611) and an energy (612) of the beam communicated with the beamforming angle (611); selecting multiple pairs of beam values (601) corresponding to beamforming communication sharing the same dominant path (901, 1650) connecting the first device (101) and the second device (102); determining a direction (703) of the dominant path (901, 1650) by evaluating a beamforming model (702) for the selected pairs of beam values, wherein the beamforming model (702) relates a deviation of a beamforming angle, caused by the resolution of the beamforming, from the dominant path (901, 1650) with the energy of the beam transmitted with the beamforming angle and received over the dominant path (901, 1650); and determining (1320) the location (704) of the first device (101) arranged along the direction (703) of the dominant path (901, 1650) with respect to the location of the second device (102) using at least some of the results of the channels estimation; wherein the beamforming model (702) relates the deviation of the beamforming angle from the dominant path (901, 1650) to the energy of the beam and an unknown distance between transceivers (201, 202) performing the beamforming, such that the beamforming model (702) includes an ambiguity in the direction (703) of the dominant path (901, 1650) resolved by the processor (701) with the selected multiple pairs of beam values (601); wherein the method uses a vertical line phased array including N antenna elements that are equally spaced at d = λ /2, where λ = c / f is the wavelength, given as the ratio between the wave speed c and the carrier frequency f ; and wherein the direction (703) of the dominant path (901, 1650) given as the angle θ 1 it encloses with a vertical line pointing upwards (905) is obtained by solving the equation z 1 z 2 = sin Nπ cosθ 1 − cos β / 2 sin π cosθ 1 − cos γ / 2 sin Nπ cosθ 1 − cos γ / 2 sin π cosθ 1 − cos β / 2 , where a received signal magnitude when steering towards a centering direction (911) of a beam (910) is z 1 , a magnitude of a received pilot signal when steering towards a centering direction (921) of a further beam (920) is z 2 , β and γ denote angles which the centering directions (911, 921), respectively, enclose with the vertical line pointing upwards (905) .
  13. A non-transitory computer readable storage medium embodied thereon a program executable by a processor for performing a method for determining a location (704) of a first device (101) based on a known location of a second device (102) using millimeter-wave, mmWave, beamforming, the method comprising: estimating a channel connecting the first device (101) and the second device (102) by comparing energy of beams communicated using the mmWave beamforming over a set of beamforming angles separated according to a resolution of the beamforming to produce results of the channels estimation including pairs of beam values (601), wherein neighboring beamforming angles in the set of beamforming angles are separated according to a resolution of the beamforming, and wherein each pair of beam values (601) includes a beamforming angle (611) and an energy (612) of the beam communicated with the beamforming angle (611); selecting multiple pairs of beam values (601) corresponding to beamforming communication sharing the same dominant path (901, 1650) connecting the first device (101) and the second device (102); determining a direction (703) of the dominant path (901, 1650) by evaluating a beamforming model (702) for the selected pairs of beam values (601), wherein the beamforming model (702) relates a deviation of a beamforming angle, caused by the resolution of the beamforming, from the dominant path (901, 1650) with the energy of the beam transmitted with the beamforming angle and received over the dominant path (901, 1650); and determining (1320) the location (704) of the first device (101) arranged along the direction (703) of the dominant path (901, 1650) with respect to the location of the second device (102) using at least some of the results of the channels estimation; wherein the beamforming model (702) relates the deviation of the beamforming angle from the dominant path (901, 1650) to the energy of the beam and an unknown distance between transceivers (201, 202) performing the beamforming, such that the beamforming model (702) includes an ambiguity in the direction (703) of the dominant path (901, 1650) resolved by the processor with the selected multiple pairs of beam values (601); wherein the method uses a vertical line phased array including N antenna elements that are equally spaced at d = λ /2, where λ = c / f is the wavelength, given as the ratio between the wave speed c and the carrier frequency f ; and wherein the direction (703) of the dominant path (901, 1650) given as the angle θ 1 it encloses with a vertical line pointing upwards (905) is obtained by solving the equation z 1 z 2 = sin Nπ cosθ 1 − cos β / 2 sin π cosθ 1 − cos γ / 2 sin Nπ cosθ 1 − cos γ / 2 sin π cosθ 1 − cos β / 2 , where a received signal magnitude when steering towards a centering direction (911) of a beam (910) is z 1 , a magnitude of a received pilot signal when steering towards a centering direction (921) of a further beam (920) is z 2 , β and γ denote angles which the centering directions (911, 921), respectively, enclose with the vertical line pointing upwards (905).

Description

[Technical Field] This invention relates generally to communications systems, and more particularly to mmWave-based indoor localization system. [Background Art] Millimeter Waves (mmWaves) are radio waves with wavelength in the range of 1 millimeter (mm)-10 mm, which corresponds to a radio frequency of 30 GigaHertz (GHz)-300 GHz. Per the definition by the International Telecommunications Union (ITU), these frequencies are also referred to as the Extremely High Frequency (EHF) band. The mmWaves exhibit unique propagation characteristics. For example, compared with lower frequency radio waves, mmWaves suffer higher propagation loss, have a poorer ability to penetrate objects, such as buildings, walls, foliage, and are more susceptible to atmosphere absorption, deflection and diffraction due to particles (e.g., rain drops) in the air. On the other hand, due to the smaller wavelengths of the mmWaves, more antennas may be packed in a relatively small area, thereby allowing for the implementation of a high-gain antenna in small form factor. The mmWaves have been less utilized than the lower frequency radio waves. A vast amount of spectrum is available in the mmWave band. For example, the frequencies around 60 GHz, which are typically referred to as the 60 GHz band, are available as unlicensed spectrum in most countries. The technical field of indoor localization deals with developing systems and methods for localizing an object in an enclosed indoor area. The object can be a device that transmits and/or receives signals to/from some other device(s), or an entity without such a capability. The localizing refers to estimating the coordinates of an object in some pre-defined reference frame. Alternatively, localization can be framed as a proximity detection problem, where one aims to localize an object at a sub-area level, within a larger indoor area. A number of applications require precise indoor localization, such as locating people and resources in hospitals, warehouses, shopping malls, factories, to name a few. For example, a paradigm of technology-assisted living is built upon accurate localization. A well-known solution for outdoor localization, known as Global Positioning System (GPS), is ineffective indoors because the electromagnetic waves transmitted from the satellites in the GPS constellation do not penetrate indoors. A number of approaches in indoor localization require installing dedicated hardware in an indoor area. While this approach also has potential to yield accurate location estimates, it is undesirable because of the cost and the fact that a dedicated system is needed for localization task. An example of this approach is ultra-wide band (UWB) radio localization systems, commercially available, but relatively expensive and used only as a last resort. Other examples include systems based on lidar, radar or ultrasound, with usually high accuracy, but also high installation and maintenance cost. In the area of mmWave communication, the system described in CN102914762A discloses a mmWave-based indoor localization system. However, that system requires installation of a dedicated infrastructure operating at mmWave frequencies. The infrastructure used for localization plays a major role in the selection of indoor localization method, along with the accuracy that can be achieved. For example, infrastructure-free indoor localization that does not require fingerprinting is a desirable approach from the cost and implementation perspectives. Such systems exploit an already existing infrastructure dedicated for some other tasks. A representative example is WiFi infrastructure, where the access points are dedicated for enabling wireless connectivity in a local area network. These methods usually rely on path loss modeling of propagation of the WiFi signals, see, e.g., U.S. Patent 9,282,531. However, the principles of mmWave communications are very different from communication in the lower frequencies, and the existing methods suitable for WiFi signals are impractical for mmWave localization. Document US 6,195,556 B1 describes a system for accurately determining the position of a mobile unit operating within a predefined service area. In the system one, two and three narrow beam base transceiver stations are used to determine a mobile unit's position. Where one base station is utilized, an information map of signal attributes is used in the position determination. Where two and three base stations are used, signal strength measurements in combination with the time difference of arrival of a signal at the various base stations are used in the position determination. Document EP 2 422 210 A1 describes an orientation and localization system with spatial filtering capabilities. [Summary of Invention] The present invention is based on recognition that a millimeter wave (mmWave) channel has several specific properties of propagation of mmWaves. In contrast with the lower frequency radio waves, the mmWave channel is