# US 9,753,131 B2 · Motion tracking via body radio reflections > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,753,131 B2 - Document ID: US9753131B2 - Status: Granted - Kind: B2 - Application number: 14/510,263 - Filed: 2014-10-09 - Published: 2017-03-23 - Granted: 2017-09-05 - Earliest claimed: 2013-10-09 - Assignees: Massachusetts Institute of Technology - Applicants: Massachusetts Institute of Technology - Inventors: Fadel Adib; Zachary Edward Kabelac; Dina Katabi - Web page: https://patentgrep.com/patent/US9753131B2 ## CPC - G01S 13/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S13/46) - G01S 7/35: Details of non-pulse systems - G01S 7/354: {Extracting wanted echo-signals (Doppler systems G01S13/50)} - G01S 7/415: {Identification of targets based on measurements of movement associated with the target} - G01S 13/003: {Bistatic radar systems; Multistatic radar systems} - G01S 13/343: {using sawtooth modulation} - G01S 13/584: {adapted for simultaneous range and velocity measurements} - G01S 13/72: for two-dimensional [2D] tracking, e.g. combination of angle and range tracking, track-while-scan radar - G01S 13/726: {Multiple target tracking} - G01S 13/878: {Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector (G01S13/874 takes precedence)} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A motion tracking system makes use of a number antennas to transmit and receive radio frequency signals that are reflected from objects (e.g., people) in the environment of the system, which may include one or more rooms of a building, the interior of a vehicle, etc., and may be partitioned, for example, walls or cloth sheets. In general, the objects in the environment include both fixed objects, such as chairs, walls, etc., as well as moving objects, such as but not limited to people. The system can track people, who may be moving around a room, or may be relatively stationary, for instance, sitting in a chair of lying in bed, but may nevertheless exhibit breathing motion that may be detected. The system may detect body or limb gestures made by the people in the environment, and detect physical activity including detection of falls. ## Claims ### Claim 1 A method for indoor localization using signal reflections from a moving body, the method comprising: emitting a transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna; receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal; for each received signal, processing the received signal to form successive patterns of reflections of the transmitting signal pattern from moving bodies, and processing the successive patterns of reflections including retaining effects of direct reflections from said moving body and excluding at least some effects of multipath reflections from said moving body that are also reflected from at least one static object; and determining a location of the body using a result of processing the successive patterns of reflections. ### Claim 2 (depends on 1) The method of claim 1 wherein, for each receiving antenna, excluding multipath reflections includes identifying a direct reflection from the moving body, and identifying indirect reflections from the moving body that also reflect from the at least one static object. ### Claim 3 (depends on 2) The method of claim 2 wherein, for each receiving antenna, excluding multipath reflections includes identifying a first round-trip time from the transmitting antenna to the receiving antenna, said first round-trip time representing a shortest round-trip propagation time of a signal pattern reflecting from the moving body. ### Claim 4 (depends on 3) The method of claim 3 wherein determining the location of the body includes using the identified first round-trip times for each received signal to eliminating multipath reflections corresponding to round-trip times greater than the identified first round-trip time. ### Claim 5 (depends on 4) The method of claim 4 wherein using the identified first round-trip times comprises tracking said times over successive patterns of reflections. ### Claim 6 (depends on 1) The method of claim 1 wherein the set of receiving antennas includes at least three antennas, with at least two antennas having different elevations. ### Claim 7 (depends on 6) The method of claim 6 wherein determining the location of the body comprises determining an elevation of the body. ### Claim 8 (depends on 1) The method of claim 1 further comprising detecting a pattern of motion in the tracked locations of the body. ### Claim 9 (depends on 8) The method of claim 8 wherein detecting a pattern of motion comprises detecting a temporal pattern of a trajectory of locations of the body. ### Claim 10 (depends on 8) The method of claim 8 wherein detecting a pattern of motion comprises detecting a pattern of motion in an environment of the localization. ### Claim 11 (depends on 8) The method of claim 8 wherein detecting the pattern of motion comprises detecting a gesture. ### Claim 12 (depends on 11) The method of claim 11 wherein detecting the gesture comprises detecting a whole-body gesture. ### Claim 13 (depends on 11) The method of claim 11 wherein detecting the gesture comprises detecting a limb gesture. ### Claim 14 (depends on 13) The method of claim 13 wherein detecting the gesture comprises detecting a pointing gesture. ### Claim 15 (depends on 14) The method of claim 14 wherein detecting a pointing gesture includes detecting a direction of a pointing gesture. ### Claim 16 (depends on 11) The method of claim 11 further comprising controlling an electrical or electronic device according to the detecting of the gesture. ### Claim 17 (depends on 16) The method of claim 16 wherein detecting the electrical or electronic device comprises controlling at least one of a gaming device, an appliance, and a lighting device. ### Claim 18 (depends on 8) The method of claim 8 wherein detecting the pattern of motion comprises detecting falling activity. ### Claim 19 (depends on 18) The method of claim 18 wherein detecting falling activity comprises monitoring at least one of a change in elevation, a duration of changing elevation of the body, and a proximity of a final elevation to a floor level. ### Claim 20 (depends on 1) The method of claim 1 wherein the signal pattern comprises a narrow band signal at a carrier frequency swept from a first frequency to a second frequency. ### Claim 21 (depends on 20) The method of claim 20 wherein the first frequency and the second frequency are both in a range of 5.46 to 7.25 gigahertz. ### Claim 22 (depends on 1) The method of claim 1 wherein receiving the received signal includes receiving a reflection of the transmitted signal after propagation through at least one obstruction. ### Claim 23 (depends on 1) The method claim 1 wherein the body is a person. ### Claim 24 (depends on 1) The method claim 1 wherein the body is a limb of a person. ### Claim 25 A method for interaction with a device using gestures made by a person comprising: tracking a motion of a body, including emitting a radio frequency transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna, receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal, tracking the location using successive reflections of the transmitted signal pattern; detecting a pattern of motion using the tracked motion of the body; using the detected pattern of motion to interact with the device. ### Claim 26 (depends on 25) The method of claim 25 wherein the tracking of the motion includes using propagation time of the transmitted signal. ### Claim 27 (depends on 26) The method of claim 26 wherein the transmitted signal pattern comprises a Frequency Modulated Carrier Wave (FMCW) signal pattern. ### Claim 28 (depends on 25) The method of claim 25 wherein the reflections of the transmitted signal comprise reflections passing through an obstruction. ### Claim 29 (depends on 25) The method of claim 25 wherein detecting the pattern of motion comprises detecting a gesture. ### Claim 30 (depends on 29) The method of claim 29 wherein detecting the gesture includes detecting a two-dimensional gesture. ### Claim 31 (depends on 29) The method of claim 29 wherein detecting the gesture includes detecting a three-dimensional gesture. ### Claim 32 (depends on 29) The method of claim 29 wherein detecting the gesture comprises detecting a whole-body gesture. ### Claim 33 (depends on 29) The method of claim 29 wherein detecting the gesture comprises detecting a limb gesture. ### Claim 34 (depends on 33) The method of claim 33 wherein detecting the limb gesture includes distinguishing a reflection from a limb from a reflection of a whole body of a person according to a size of the reflection. ### Claim 35 (depends on 33) The method of claim 33 wherein detecting the gesture comprises detecting a pointing gesture. ### Claim 36 (depends on 29) The method of claim 29 further comprising controlling an electrical or electronic device according to the detecting of the gesture. ### Claim 37 A method for detecting fall of a person comprising: tracking a motion of the person, including emitting a radio frequency transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna, receiving, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal, tracking the location using successive reflections of the transmitted signal pattern; detecting a pattern of motion using the tracked motion of the body; using the detected pattern of motion to detect a fall of the person. ### Claim 38 (depends on 37) The method of claim 37 wherein the reflections of the transmitted signal comprise reflections passing through an obstruction. ### Claim 39 (depends on 37) The method of claim 37 wherein detecting the pattern of motion comprises monitoring at least one of a change in elevation, a duration of changing elevation of the body, and a proximity of a final elevation to a floor level. ### Claim 40 (depends on 39) The method of claim 39 wherein detecting the pattern of motion comprises monitoring a change of elevation includes detecting a change of elevation of at least a threshold value. ### Claim 41 (depends on 39) The method of claim 39 wherein detecting the pattern of motion comprises monitoring the duration of changing elevation includes detecting a duration less than a threshold value. ### Claim 42 (depends on 39) The method of claim 39 wherein detecting the pattern of motion comprises monitoring proximity of the final elevation includes detecting a final elevation less than a threshold value. ### Claim 43 (depends on 39) The method of claim 39 wherein detecting the pattern of motion comprises detecting when each condition of the group of conditions consisting of a change of elevation of at least a first threshold value, a duration less than a second threshold value, and a final elevation less than a third threshold value, are satisfied. ### Claim 44 A system comprising: a transmitting antenna and a set of receiving antenna; a transmitter coupled to the transmitting antenna and configured to generate a transmitting signal comprising repetitions of a transmitting signal pattern; a receiver coupled to the set of receiving antennas, for receiving signals comprising reflections of the transmitting signal; a processor coupled to the transmitter and to the receiver, configured to cause the system to emit a transmitted signal comprising repetitions of a transmitted signal pattern from a transmitting antenna; receive, at each receiving antenna of a set of receiving antennas, a received signal comprising reflections of the transmitted signal; for each received signal, process the received signal to form successive patterns of reflections of the transmitting signal pattern from moving bodies, and process the successive patterns of reflections including retaining effects of direct reflections from said moving body and excluding at least some effects of multipath reflections from said moving body that are also reflected from at least one static object; and determine a location of the body using a result of processing the successive patterns of reflections.