Detecting motion based on repeated wireless transmissions

In a general aspect, motion of an object is detected based on wireless signals. In some aspects, wireless signals based on a repeated wireless transmission are received at a wireless sensor device in a space. The received wireless signals are analyzed, by operation of a processor, to detect movement of an object in the space. The analysis includes determining complex values representing the relative phases and amplitudes of respective frequency components of each of the received wireless signals, and detecting movement of an object in the space based on a change in the complex values.

BACKGROUND

The following description relates to detecting motion, for example, based on repeated wireless transmissions.

Motion detection systems have been used to detect movement, for example, of objects in a room or an outdoor area. In some example motion detection systems, infrared or optical sensors are used to detect movement of objects in the sensor's field of view. Motion detection systems have been used in security systems, automated control systems and other types of systems.

DETAILED DESCRIPTION

In some aspects of what is described, motion of an object is detected based on repeated transmissions of a wireless signal. A motion detection system may include one or more sensor devices, source devices and other components. In some example implementations, motion is detected based on signals (e.g., Bluetooth Beacons, Wi-Fi Beacons, other wireless beacon signals or other types of signals) that are generated by another system. In some examples, a wireless signal may propagate through an object (e.g., a wall) before or after interacting with a moving object, which may allow the object's movement to be detected without an optical line-of-sight between the moving object and the sensor device. Motion detector systems may be used in larger systems, such as a security system, that may include a control center for monitoring movement within a space, such as a room, building, etc.

FIG. 1is a diagram showing an environment with example motion detection system. In the example shown, source devices can transmit wireless signals in the radio spectrum. The example source devices shown inFIG. 1include a Bluetooth source102, a satellite source104, a base station source106, a Wi-Fi source108, and a cellular phone source110. In some examples, a laptop computer or tablet may include a Bluetooth source102, and may communicate with various devices near the laptop computer or tablet, such as a mouse, a headset, etc. A satellite source104may transmit, for example, signals for a Global Positioning System (GPS). In some examples, a base station source106can provide signals to connect mobile devices to a telephony network, to connect computing devices to a data network, etc. In some examples, a Wireless Access Point (WAP) for a network may operate as a Wi-Fi source108, which can allow computing devices, such as computers, tablets, smartphones, etc., to connect to a communications network. In some examples, a cellular phone can include one or more cellular phone sources110that transmit signals for Bluetooth or NFC systems, for Wi-Fi or cellular networks, or for other types of systems. Other source devices may be used.

In the example environment shown inFIG. 1, example sensor devices are illustrated in various locations.FIG. 1illustrates a first sensor device112, a second sensor device114, a third sensor device116, and a fourth sensor device118. A different number of sensor devices may be used. For example, a single sensor device may be used in some cases, or a large number (e.g., tens, hundreds, etc.) of sensor devices may be used.

The example sensor devices112,114,116, and118shown inFIG. 1are adapted to receive and analyze signals from one or more of the example source devices. The example sensor devices may receive signals through a communication channel, and the signal that is received can be used to detect movement of an object100(e.g., a person, a structure, a device, etc.) in the communication channel. An example sensor device is described with reference toFIGS. 7, 8 and 9. In some examples, a single device may operate as a source device and a sensor device at different times.

A communication channel for a wireless signal can include, for example, air or any other medium through which the wireless electromagnetic signal propagates. A communication channel can include multiple paths for a transmitted wireless electromagnetic signal. For a given communication channel (or a given path in a communication channel), the transmitted signal can be reflected off of or scattered by a surface in the communication channel. Reflection or scattering may occur as a result of the transmitted signal being incident upon an impedance discontinuity, which may occur at a boundary between distinct materials, such as a boundary between air and a wall, a boundary between air and a person, or other boundaries. In some instances, when a transmitted signal becomes incident upon a boundary between a first material (in this example, air) and a second material (in this example, a wall), a portion of the transmitted signal can be reflected or scattered at the boundary between the air and the wall. Additionally, another portion of the transmitted signal may continue to propagate through the wall, it may be refracted or affected in another manner. Further, the other portion that propagates through the wall may be incident upon another boundary, and a further portion may be reflected or scattered at that boundary and another portion may continue to propagate through the boundary.

At a sensor device, signals that propagate along the multiple paths of the communication channel can combine to form a received signal. Each of the multiple paths can result in a signal along the respective path having an attenuation and a phase offset relative to the transmitted signal due to the path length, reflectance or scattering of the signal, or other factors. Hence, the received signal at the sensor device can have different components that have different attenuations and phase offsets relative to the transmitted signal. When an object that reflects or scatters a signal in a path moves, a component of the received signal at the sensor device can change. For example, a path length can change resulting in a smaller or greater phase offset and resulting in more or less attenuation of the signal. Hence, the change caused by the movement of the object can be detected in the received signal.

FIGS. 2A and 2Bare diagrams showing signals transmitted in a space200that includes an example motion detection system. The example space200can be completely or partially enclosed or open at one or more boundaries of the space. The space200can be or can include an interior of a room, multiple rooms, a building, or the like. A first wall202, a second wall204, and a third wall206at least partially enclose the space200in the example shown.

The example motion detection system includes a source device208, a first sensor device210and a second sensor device212in the space200. The source device208is operable to transmit a transmitted wireless signal (e.g., an RF wireless signal) repeatedly (e.g., periodically, intermittently, at random intervals, etc.). The sensor devices210,212are operable to received wireless signals (e.g., RF wireless signals) based on the transmitted wireless signal. The sensor devices210,212each have a processor that is configured to determine characteristics (e.g., relative phase and magnitude) of frequency components of respective signals based on the received wireless signals. The sensor devices210,212each have a processor that is configured to detect motion of an object based on a comparison of the characteristics of the frequency components. In some examples, a single processor or multiple processors may be used, for example, as discussed with respect toFIGS. 8 and 9.

As shown, an object is in a first position214ainFIG. 2A, and the object has moved to a second position214binFIG. 2B. InFIGS. 2A and 2B, the moving object in the space200is represented as a human, but the moving object can be another type of object. For example, the moving object can be an animal, an inorganic object (e.g., a system, device, apparatus or assembly), or object that defines all or part of the boundary of the space200(e.g., a wall, door, window, etc.), or another type of object.

As shown inFIGS. 2A and 2B, multiple example paths of a wireless signal transmitted from the source device208are illustrated by dashed lines. Along a first signal path216, the wireless signal is transmitted from the source device208and reflected off the first wall202toward the second sensor device212. Along a second signal path218, the wireless signal is transmitted from the source device208and reflected off the second wall204and the first wall202toward the first sensor device210. Along a third signal path220, the wireless signal is transmitted from the source device208along a third path and reflected off the second wall204toward the first sensor device210. Along a fourth signal path222, the wireless signal is transmitted from the source device208and reflected off the third wall206toward the second sensor device212.

InFIG. 2A, along a fifth signal path224a, the wireless signal is transmitted from the source device208and reflected off the object at the first position214atoward the first sensor device210. BetweenFIGS. 2A and 2B, a surface of the object moves from the first position214ato a second position214bin the space200some distance away from the first position214a. InFIG. 2B, along a sixth signal path224b, the wireless siganl is transmitted from the source device208and reflected off the object at the second position214btoward the first sensor device210. The sixth signal path224bdepicted inFIG. 2Bis longer than the fifth signal path224adepicted inFIG. 2Adue to the movement of the object from the first position214ato the second position214b. In some examples, a path to a sensor can be added, removed or otherwise modified due to movement of an object in a space.

The example signals shown inFIGS. 2A and 2Bmay experience attenuation, frequency shifts, phase shifts or other effects through their respective paths and may have portions that propagate in another direction, for example, through the walls202,204, and206. In some examples, the signals are radio frequency (RF) signals; or the signals may include other types of signals.

As shown inFIGS. 2A and 2B, the source device208repeatedly transmits a signal. In particular,FIG. 2Ashows the signal being transmitted from the source device208at a first time, andFIG. 2Bshows the same signal being transmitted from the source device208at a second, later time. The transmitted signal can be transmitted continuously, periodically, at random or intermittent times or the like, or a combination thereof. The transmitted signal can have a number of frequency components in a frequency bandwidth. The transmitted signal can be transmitted from the source device208in an omnidirectional manner, in a directional manner or otherwise. In the example shown, the signals traverse multiple respective paths in the space200, and the signal along each path may become attenuated due to path losses, scattering, reflection, or the like and may have a phase or frequency offset.

As shown inFIGS. 2A and 2B, the signals from various paths216,218,220,222,224a, and224bcombine at the first sensor device210and the second sensor device212to form received signals. Because of the effects of the multiple paths in the space200(an example communication channel) on the transmitted signal, the space200may be represented as a transfer function (e.g., a filter) in which the transmitted signal is input and the received signal is output. When an object moves in the space200, the attenuation or phase offset affected upon a signal in a signal path can change, and hence, the transfer function of the space200can change. Assuming the same transmitted signal is transmitted from the source device208, if the transfer function of the space200changes, the output of that transfer function—the received signal—will also change. A change in the received signal can be used to detect movement of an object.

Mathematically, a transmitted signal f(t) transmitted from the source device208may be described according to Equation (1):

f⁡(t)=∑n=-∞∞⁢cn⁢ⅇjωn⁢t(1)
where ωnrepresents the frequency of nthfrequency component of the transmitted signal, cnrepresents the complex coefficient of the nthfrequency component, and t represents time. With the transmitted signal f(t) being transmitted from the source device208, an output signal rk(t) from a path k may be described according to Equation (2):

rk⁡(t)=∑n=-∞∞⁢αn,k⁢cn⁢ⅇj⁡(ωn⁢t+ϕn,k)(2)
where αn,krepresents an attenuation factor (e.g., due to scattering, reflection, and path losses) for the nthfrequency component along path k, and φn,krepresents the phase of the signal for nthfrequency component along path k. Then, the received signal R at a sensor device can be described as the summation of all output signals rk(t) from all paths to the sensor device, which is shown in Equation (3):

R=∑k⁢rk⁡(t)(3)
Substituting Equation (2) into Equation (3) renders the following Equation (4):

The received signal R at a sensor device can then be analyzed. The received signal R at a sensor device can be transformed to the frequency domain, for example, using a Fast Fourier Transform (FFT) or another type of algorithm. The transformed signal can represent the received signal R as a series of n complex values, one for each of the respective frequency components (at the n frequencies ωn). For a frequency component at frequency ωn, a complex number Ynmay be represented as follows in Equation (5):

Yn=∑k⁢cn⁢αn,k⁢ⅇjϕn,k(5)
The complex value Ynfor a given frequency component ωnindicates a relative magnitude and phase offset of the received signal at that frequency component ωn.

With the source device208repeatedly (e.g., at least twice) transmitting the transmitted signal f(t) and a respective sensor device210and212receiving and analyzing a respective received signal R, the respective sensor device210and212can determine when a change in a complex value Yn(e.g., a magnitude or phase) for a given frequency component ωnoccurs that is indicative of movement of an object within the space200. For example, a change in a complex value Ynfor a given frequency component ωnmay exceed a predefined threshold to indicate movement. In some examples, small changes in one or more complex values Ynmay not be statistically significant, but may only be indicative of noise or other effects.

In some examples, transmitted and received signals are in an RF spectrum, and signals are analyzed in a baseband bandwidth. For example, a transmitted signal may include a baseband signal that has been up-converted to define a transmitted RF signal, and a received signal may include a received RF signal that has been down-converted to a baseband signal. Because the received baseband signal is embedded in the received RF signal, effects of movement in the space (e.g., a change in a transfer function of the communication channel) may occur on the received baseband signal, and the baseband signal may be the signal that is analyzed (e.g., using a Fourier analysis or another type of analysis) to detect movement. In other examples, the analyzed signal may be an RF signal or another signal.

FIG. 3is a flowchart showing an example process for detecting movement in a space. The example process shown inFIG. 3may include additional or different operations, and the operations can be performed in the order shown or in another order. In some implementations, the process shown inFIG. 3can be performed by a motion detection system such as, for example, the motion detection systems shown inFIGS. 2A and 2B. In some implementations, the process shown inFIG. 3can be performed by another type of system that includes similar or different components.

At300, a wireless signal is transmitted from a source, which produces a transmitted wireless signal in a space. The transmission is performed repeatedly. Referring back toFIGS. 2A and 2B, for example, the source device208can repeatedly send a transmitted wireless signal. In some implementations, the transmission can be a beacon signal that is repeatedly sent by a Bluetooth device, a Wi-Fi router, or another type of device. The repeated transmissions can be sent at scheduled times, at periodic or random intervals or in other time steps. In some cases, the transmitted wireless signal is multiple times per second, per minute, per hour, etc.

At302, a wireless signal is received at a sensor in the space; the received wireless signal is based on the transmission of the transmitted wireless signal. As shown inFIG. 3, wireless signals can be received repeatedly, such that, for example, a signal can be received at302for each transmission at300. Referring back to the example shown in FIGS.2A and2B, the first sensor device210repeatedly receives a wireless signal—at a first time inFIG. 2A, and at a second time inFIG. 2B.

At304, characteristics of frequency components of the received wireless signal are determined. As discussed above in the example ofFIGS. 2A and 2B, the received signals can be transformed (e.g., Fourier transformed) to the frequency domain to determine complex values representing the frequency components in a bandwidth of the signal. For example, the spectrum analysis engine960inFIG. 9, the central processing unit (CPU)840inFIG. 8or another type of processor may be configured to identify frequency components. The analysis can be performed for each of the received wireless signals.

At306, movement of an object in the space is detected based on the characteristics of the frequency components of multiple received wireless signals. For example, in the example ofFIGS. 2A and 2B, when a complex value representing a magnitude and phase of a frequency component of a received signal changes by an amount that exceeds a threshold value, movement can be detected. For example, the spectrum analysis engine960inFIG. 9, the central processing unit (CPU)840inFIG. 8or another type of processor may be configured to detect movement.

In an example implementation of the process shown inFIG. 3, at a first time t1, the source device208sends a first transmission T1of a signal S; the first sensor device210then receives a first wireless signal R1based on the first transmission T1. At a second, later time t2, the source device208sends a second transmission T2of the same signal S; the first sensor device210then receives a second wireless signal R2based on the second transmission T2. In this example, the first and second transmissions (T1and T2) from the source device208are the same wireless signal (S=f(t)), transmitted at different times. The received wireless signals (R1and R2) may be the same or different. For example, when there is no movement of objects in the path traversed by the first and second transmissions (T1and T2) between the transmission times (t1and t2), the received wireless signals (R1and R2) are the same; whereas movement of an object in a path between the transmission times (t1and t2) may cause a difference in the received wireless signals (R1and R2). Accordingly, the sensor device210can detect movement of objects along any signal path between the source device208and the sensor device210based on a comparison between the received wireless signals (R1and R2).

FIG. 4is a diagram showing a signal transmitted in a space that includes an example motion detection system. Much of the environment and the components ofFIG. 4are the same as or similar to the environment and the components ofFIGS. 2A and 2B. InFIG. 4, the motion detection system includes a device400that can operate as both a source device and a sensor device. InFIG. 4, the device400can repeatedly transmit a transmitted signal or repeatedly receive and analyze a received signal, for example, in the manner discussed above with respect toFIGS. 2A and 2B. The device400is capable of detecting movement of an object in the space200based on the analysis of received signals. In the example shown, the device400operates as a source device, and the sensor devices210and212receive wireless signals based on transmissions from the device400. At other instances, the same device400may operate as a sensor device and receive wireless signals based on transmissions from another source device.

FIGS. 5A and 5Bare diagrams showing signals transmitted in another space that includes an example motion detection system. The example space500can be completely or partially enclosed or open at one or more boundaries of the space. The space500can be or can include an interior of a room, multiple rooms, a building, or the like. A first wall502, a second wall504, and a third wall508at least partially enclose the space500in this example. In the example shown, the second wall504includes a door506.

The example motion detection system includes a source device510, a first sensor device512and a second sensor device514in the space500. As shown inFIGS. 5A and 5B, multiple example paths of a wireless signal transmitted from the source device510are illustrated by dashed lines. Along a first signal path516, a wireless signal is transmitted from the source device510and reflected off the first wall502toward the second sensor device514. Along a second signal path518, the wireless signal is transmitted from the source device510and reflected of the second wall504toward the first sensor device512. Along a third signal path520, the wireless signal is transmitted from the source device510and reflected off the third wall508toward the second sensor device514.

As shown inFIG. 5A, the door506in the second wall504is open, and the wireless signal along a fourth signal path522ais transmitted from the source device510through the open door506. InFIG. 5A, there is no surface at the boundary of the space500to reflect the signal along the fourth signal path522a. InFIG. 5B, the door506in the second wall504has moved to a shut position, and the signal along a fifth signal path522bis transmitted from the source device510and reflected off the shut door506toward the first sensor device512. The door506closing causes the signal path to change during the time between the first and second transmissions of the wireless signal from the source device510, which causes a corresponding change in the received signal at the first sensor device512. The change in the received signal can be identified by the sensor device512to detect the motion of the door506, for example, according to the process shown inFIG. 3or in another manner.

Additionally, repetitive movements may be learned and catalogued by a sensor device. As inFIGS. 5Aand SB, a door opening and closing provides an example of a repetitive movement that can be learned and catalogued. In some cases, a movement in a space has an identifiable type of effect on a signal received at a sensor device. For example, assuming no other movement in a space, a repeated movement may cause the received signal to change in the same manner each instance the movement occurs. The characteristic change in the received signal can be identified to detect an instance of the repeated movement. A signature for a repetitive movement may be saved in memory in a sensor device so that the signature can be compared against detected signal changes, for example, to identify the nature of a detected movement. In some cases, this can provide more information to a person or system reviewing information about the movement detection. Noise or other effects may reduce the ability to detect a change in some cases.

FIG. 6is a diagram showing an example space600that includes multiple sensor devices610. The environment inFIG. 6can represent the example environments ofFIGS. 2A, 2B, 4, 5A and 5B, or another environment. The example space600inFIG. 6is a room defined, at least in part by a first wall602, a second wall604, a third wall606, and a fourth wall608. Another implementation may have another configuration for a space600, which may be a room, multiple rooms, a building, or the like. As shown inFIG. 6, each sensor device610has a spatial location (xi, yi, zi) and can monitor and analyze a received signal at its respective spatial location (xi, yi, zi).

Additionally, in some example implementations, each sensor device can transmit information (e.g., characteristics of a received signal, an indication of detection of motion, an identification of the detected motion, time of the detected motion, sensor device610identification or location information, or the like) to a data aggregation system (e.g., as discussed below inFIG. 7). For example, the location and time information can include spatial coordinates of the sensor device (e.g., (xi, yi, zi) or in other coordinates) and temporal coordinates (e.g., a time of day) at which motion is detected. The example environment inFIG. 6shows the spatial coordinates of the sensor devices610and serves as a map of the example spatial distribution of the sensor devices in the space600.

FIG. 7is a block diagram showing an architecture of an example motion detection system700. The motion detection system700can be implemented with the sensor devices or source devices in the example environments ofFIGS. 2A, 2B, 4, 5A, 5B, or another environment. The example motion detection system700includes sensor devices and one or more source devices. The sensor devices610are shown in the example motion detection system700ofFIG. 7. The example motion detection system700further includes an IP network720and a main controller730. The motion detection system700can include additional or different components. In some implementations, a motion detection system can be arranged as shown inFIG. 7or in another manner.

In the example shown inFIG. 7, each sensor device610is at a respective physical location having spatial coordinates (xi, yi, zi), where i varies from 1 to n+1 (n+1 being the number of the sensor devices610). In some implementations, each sensor device610can include a Global Positioning System (GPS) or another location identification system that identifies the location coordinates of the sensor device610, or the location coordinates can be identified in another manner. In some implementations, each sensor device610has a unique identifier, and the identifier can be associated with a location identifier or location coordinates.

The example sensor devices can receive respective signals that the sensor devices analyze for changes. Some changes, e.g., statistically significant changes, in a received signal can be indicative of movement in a space. For instance, the sensor device can detect an RF signal in a local wireless environment about the location of the sensor device at any given time. The RF signal can be in any bandwidth and may cover any portion of the radio spectrum.

In the example shown inFIG. 7, data from the sensor devices (e.g., movement indications, location information, etc.) are aggregated by a data aggregation or central control system (e.g., the main controller730). In some implementations, data from the sensor devices are aggregated by the main controller730by receiving the messages transmitted from the sensor devices, for example, through the IP network (e.g., the IP network720). In some implementations, the sensor devices are connected to the IP network720via a local network (e.g., a local internet702or704). The sensor devices can be connected to the local network by a local wireline network714or a wireless network712. The wireline network714can include, for example, Ethernet, xDSL (x-digital subscriber line), optical network, or other types of wireline communication networks. The wireless network712can include, for example, WiFi, Bluetooth, near field communication (NFC), or other types of local wireless networks. In some implementations, some of the sensor devices are connected directly to the IP network720using one or more wide area networks706. The wide area networks706can include, for example, cellular network, satellite network, or other types of wide area networks.

The main controller730can be a computing system that includes one or more computing devices or systems. The main controller730or any of its components can be located at a data processing center, a computing facility, or another location. In the example shown, the main controller730can remotely control and monitor operation of the sensor devices. Example functions of the main controller730can include aggregating the information from some or all of the sensor devices, upgrading the sensor device software, monitoring states of the sensor devices, etc. For example, the main controller730can send software updates to some or all sensor devices.

In the example shown inFIG. 7, the main controller730can put the sensor devices into one or more calibration or test modes, reset various elements within the sensor devices, or configure an individual sensor device, for example, based on the location or state of the sensor device, its neighboring sensor devices, or other factors. In some examples, the states of an sensor device can include: (i) the temperature of the sensor device, (ii) the current power consumption of the sensor device, (iii) the data rate flowing from the sensor device back to the main controller730, (iv) the location of the sensor device (e.g., detected an internal GPS unit in the sensor device), (v) a signal (e.g., IP packets, control signaling transmitted over the network) that provides information on the state of the sensor device or its surrounding sensor devices. The main controller730may monitor additional or different states of the sensor devices.

In some implementations, the main controller730can include or be coupled to a communication system that receives information related to movement detection (e.g., indication of movement detection, movement signature, detected changes in complex values representing magnitudes and phases of frequency components, spatial and temporal coordinates for each of the sensor devices, etc.) transmitted from the sensor devices. The main controller730can include or be coupled to a data analysis system736that can aggregate (e.g., assemble, compile or otherwise manage) the information related to movement detection from the multiple sensor devices and generate an incident report for, e.g., when movement is detected, such as for an investigation into the cause of the movement.

In some instances, the incident report can be presented on a data interface738to present users the indication of movement or other information from the sensor devices relative to the various locations of the sensor devices. For example, the incident report can indicate detected movements based on time and location or other information, which may be helpful to determine a source of movement. In some implementations, the data analysis system736can analyze real-time data, historical data, or a combination of both, and determine when movement occurs at a location. Accordingly, the main controller730may be used as a control center of a security system, where personnel are able to be alerted to detected movement and to dispatch security or police in response to the alert.

FIG. 8is a block diagram showing an example sensor device800. In some cases, the sensor devices ofFIGS. 2A, 2B, 4, 5A, 5B, 6 and 7can be implemented as the example sensor device800shown inFIG. 8. The example sensor device800includes a housing810, an RF interface812, a power management subsystem820, a signal analysis subsystem (e.g., the SI subsystem830, etc.), a CPU840, a memory850, communication interfaces, an input/output interface842(e.g., a USB connection), a GPS interface848, and one or more sensors (e.g.,3D orientation sensors844such as a compass or gyroscope, temperature sensors, etc.). The sensor device800can include additional or different components and features, and the features of the sensor device can be arranged as shown inFIG. 8or in another suitable configuration.

In some implementations, the housing810can be a portable housing that houses the RF interface812, the power management subsystem820, the signal analysis subsystem, the communication interfaces, and other components of the sensor device800. The housing can be made of plastic, metal, composites, or a combination of these and other materials. The housing can include components that are manufactured by molding, machining, extruding, or other types of processes. In some implementations, the sensor device800can be coupled to or integrated with another device (e.g., a WiFi access point or base station, a router, a thermostat, etc.). For example, the housing810of the sensor device800can be attached to, incorporated, or otherwise coupled to the other device. Alternatively, the housing810can be a dedicated housing that houses only the components of the sensor device800.

In some implementations, the design and arrangement of the housing810and components inside the housing810can be optimized or otherwise configured for monitoring and receiving wireless signals. For example, the sizes, orientations, and relative locations of the components can be optimized for detecting and analyzing wireless signals, and the device can be compact while accommodating all the necessary components. In some instances, the housing810can be on the order of, for example, 10×10×4 cm3; or another size housing can be used.

In some implementations, the RF interface812is configured to detect RF signals in multiple bandwidths of an RF spectrum in a local wireless environment about the sensor device800. The RF interface812can include an antenna system and multiple radio paths that are configured to process RF signals in the respective bandwidths. In the example shown inFIG. 8, the RF interface812includes an antenna822a, RF passive elements824, RF active elements826, and passive elements828. The RF passive elements824can include, for example, matching elements, RF switches, and filters. The RF active elements826can include, for example, RF amplifiers. The passive elements828after the RF active elements826can include, for example, filters, matching elements, switches, and baluns.

In some examples, the signal analysis subsystem can be configured to detect movement based on the RF signals. A signal analysis subsystem can include radio(s) digital signal processor (DSP), memory, and other components for extracting, e.g., complex values for the frequency components of a wireless signal, and for detecting movement. In some implementations, the combination of the RF interface812and the signal analysis subsystem can be referred to as a spectrum inspection (SI) signal path, which is described in greater detail with respect toFIG. 9.

The communication interfaces of the sensor device800can be configured to transmit the movement indication or other information to a remote system (e.g., the main controller730ofFIG. 7). The communication interfaces can include one or more wireless interfaces832(e.g., a WiFi connection, cellular connection, etc.), a wireline interface846to a local network (e.g., an Ethernet connection, xDSL connection, etc.) or other types of communication links or channels. The communication interfaces can share and reuse the common antennas (e.g., using an antenna array) or they can each have distinct and dedicated antennas.

The wireless interface832and the wireline interface846can each include a modem to communicate with the local or wide area network. For example, the wireless interface832and the wireline interface846can send information to a data aggregation system (e.g., the main controller730ofFIG. 7) and receive control information (e.g., software updates) from the data aggregation system, via the local or wide area network. In some implementations, a sensor device can be equipped with either or both of the communication interfaces. The wireline interface846can allow the example sensor device800to exploit existing wireline communication infrastructure (e.g., in a building) and large transmission capacity of wireline communications (e.g., large bandwidth provided by optical network, advanced digital subscriber line technologies, etc.). The wireless interface832can enhance the mobility and flexibility of the example sensor device800such that it can deliver information at a variety of locations and times, using Bluetooth, WiFi, cellular, satellite, or other wireless communication technologies. In some example implementations, when wireless communication is used with the wireless interface832, the wireless communication may implement signals in a bandwidth distinct from a bandwidth in which signals are used for detecting motion.

In some implementations, the wireless interface832and the RF interface812can share hardware or software components (or both). In some implementations, the wireless interface832and the RF interface812can be implemented separately. In some implementations, the RF interface812is mainly responsible for signal reception rather than transmission, and the RF interface812can be implemented with specialized lower-power circuitry and thus reduce the overall power consumption of the sensor device800.

The power management subsystem820can include circuits and software for providing and managing power to the sensor device800. In some implementations, the power management subsystem820can include a battery interface and one or more batteries (e.g., rechargeable batteries, a smart battery with an embedded microprocessor, or a different type of internal power source). The battery interface may be coupled to a regulator, which may assist the battery in providing direct current electrical power to the sensor device800. As such, the sensor device800can include a self-contained power supply and can be used at arbitrary locations without need for other external energy sources. Additionally or alternatively, the power management subsystem820can include an external power interface that receives power from an external source (e.g., an alternating current power source, an adapter, a converter, etc.). As such, the sensor device800can be plugged into an external energy source.

In some implementations, the power management subsystem820can oversee and manage power consumption of the sensor device800. For example, the power management subsystem820can monitor the power consumption of the RF interface812, communication interfaces, the CPU840, and other components of the sensor device800, and report the power consumption state of the sensor device800, for example, to a central controller. In some implementations, the sensor device800can be designed to have low power consumption and the power management subsystem820can be configured to send an alert to the central controller or intervene with the operations of the sensor device800if the power consumption exceeds a threshold. The power management subsystem820can include additional or different features.

The CPU840can include one or more processors or another type of data-processing apparatus that can execute instructions, for example, to manage the operations of the sensor device800. The CPU840may perform or manage one or more of the operations of a sensor device described with respect toFIGS. 2A, 2B, 3, 4, 5A and 5B. In some implementations, the CPU840can be part of the signal analysis subsystem830. For example, the CPU840can process and otherwise analyze the information relating to a received signal or relating to motion detection. In some cases, the CPU840can execute or interpret software, scripts, programs, functions, executables, or other modules contained in the memory850.

The input/output interface842can be coupled to input/output devices (e.g., a USB flash drive, a display, a keyboard, or other input/output devices). The input/output interface842can assist data transfer between the sensor device800and the external storage or display device, for example, over communication links such as a serial link, a parallel link, a wireless link (e.g., infrared, radio frequency, or others), or another type of link.

The memory850can include, for example, a random access memory (RAM), a storage device (e.g., a writable read-only memory (ROM) or others), a hard disk, or another type of storage medium. The memory850can store instructions (e.g., computer code) associated with operations of the sensor device800, a main controller, and other components in a sensor device. The memory850can also store application data and data objects that can be interpreted by one or more applications or virtual machines running on the sensor device800. The memory850can store, for example, location data, environment data, and state data of the sensor device800, movement detection data, and other data.

In some implementations, the sensor device800can be programmed or updated (e.g., reprogrammed) by loading a program from another source (e.g., from a central controller through a data network, a CD-ROM, or another computer device in another manner). In some instances, the central controller pushes software updates to the sensor device800as the updates become available, according to a predetermined schedule, or in another manner.

FIG. 9is a block diagram showing an example signal path900. The example signal path900includes an RF interface910(e.g., denoted as Radio Path A) and a spectrum analysis subsystem905. The RF interface812of the sensor device800ofFIG. 8can be implemented as the example RF interface910inFIG. 9or in another manner. The SI subsystem830of the sensor device800ofFIG. 8can be implemented as the example spectrum analysis subsystem905inFIG. 9or in another manner. In some cases, the signal path900can perform all operations for monitoring and detecting movement. For example, the signal path900can perform functions of a wireless receiver such as demodulation, etc. The signal path900can support signal reception of various wireless communication standards and access the spectrum analysis subsystem905for detecting movement.

In the example shown, the RF interface910can include a wideband or narrowband front-end chipset for detecting and processing RF signals. For example, the RF interface910can be configured to detect RF signals in a wide spectrum of one or more frequency bands, or a narrow spectrum within a specific frequency band of a wireless communication standard. In some implementations, an signal path900can include one or more RF interfaces910to cover the spectrum of interest. Example implementations of such an signal path are described with respect toFIG. 8.

In the example shown inFIG. 9, the RF interface910includes one or more antennas922, an RF multiplexer920or power combiner (e.g., an RF switch), and one or more signal processing paths (e.g., “path1”930, . . . , “path M”940). The antenna922can be implemented, for example, as a multi-port antenna or single-port antenna. The antenna922can include an omnidirectional antenna, a directional antenna, or a combination of one or more of each. The example antenna922is connected to an RF multiplexer920. In some implementations, the RF interface910can be configured to use the one or more antennas922for detecting the RF signals based on single-input single-output (SISO), single-input and multiple-output (SIMO), multiple-input and single-output (MISO) or multiple-input and multiple-output (MIMO) technologies.

In some implementations, an RF signal in the local environment of an sensor device can be picked up by the antenna922and input into the RF multiplexer920. Depending on the frequency of the RF signal, the signal902output from the RF multiplexer920can be routed to one of the processing paths (i.e., “path1”930, . . . , “path M”940). Here M is an integer. Each path can include a distinct frequency band. For example, “path1”930may be used for RF signals between 1 GHz and 1.5 GHz, while “path M” may be used for RF signals between 5 GHz and 6 GHz. The multiple processing paths may have a respective central frequency and bandwidth. The bandwidths of the multiple processing paths can be the same or different. The frequency bands of two adjacent processing paths can be overlapping or disjointed. In some implementations, the frequency bands of the processing paths can be allocated or otherwise configured based on the assigned frequency bands of different wireless communication standards (e.g., GSM, LTE, WiFi, etc.). For example, it can be configured such that each processing path is responsible for detecting RF signals of a particular wireless communication standard. As an example, “path1”930may be used for detecting LTE signals while the “path M”940may be used for detecting WiFi signals.

Each processing path (e.g., “processing path1”930, “processing path M”940) can include one or more RF passive and RF active elements. For example, the processing path can include an RF multiplexer, one or more filters, an RF de-multiplexer, an RF amplifier, and other components. In some implementations, the signals902,902moutput from the RF multiplexer920can be applied to a multiplexer in a processing path (e.g., “RF multiplexer1”932, . . . , “RF multiplexer M”942). For example, if “processing path1”930is selected as the processing path for the signal902, the signal902can be fed into “RF multiplexer1”932. The RF multiplexer can choose between the signal902coming from the first RF multiplexer920or the RF calibration (cal) tone938provided by the spectrum analysis subsystem905. The output signal904of “RF multiplexer1”932can go to one of the filters, Filter(1,1)934a, . . . , Filter (1,N)934n, where N is an integer. The filters further divide the frequency band of the processing path into a narrower band of interest. For example, “Filter(1,1)”934acan be applied to the signal904to produce a filtered signal906, and the filtered signal906can be applied to “RF de-multiplexer1”936. In some instances, the signal906can be amplified in the RF de-multiplexer. The amplified signal908can then be input into the spectrum analysis subsystem905.

Similarly, if “processing path M”940is selected as the processing path for the signal902m, the signal902mcan be fed into “RF multiplexer M”942. The RF multiplexer can choose between the signal902mcoming from the first RF multiplexer920or the RF calibration (cal) tone948provided by the spectrum analysis subsystem905. The output signal of “RF multiplexer M”942can go to one of the filters, Filter(M,1)944a, . . . , Filter (M,N)944n, where N is an integer. In some instances, the output signal of the filters can be amplified in the RF de-multiplexer M946. The amplified signal908mcan then be input into the spectrum analysis subsystem905.

The spectrum analysis subsystem905can be configured to convert the detected RF signals into digital signals and perform digital signal processing to detect movement based on the detected RF signals. The spectrum analysis subsystem905can include one or more radio receive (RX) paths (e.g., “radio RX path1”950a, “radio RX path M”950m), a DSP spectrum analysis engine960, an RF calibration (cal) tone generator970, a front end control module980, and an I/O990. The spectrum analysis subsystem705may include additional or different components and features.

In the example shown, the amplified signal908is input into “radio RX path1”950a, which down-converts the signal908into a baseband signal and applies gain. The down-converted signal can then be digitalized via an analog-to-digital converter. The digitized signal can be input into the DSP spectrum analysis engine960. In some example implementations, the DSP spectrum analysis engine960is implemented as one or more processors, which can include programmable logic (like a field programmable gate array (FPGA) with a core instantiated thereon), a general purpose processor configured to execute program code instructions, an application specific integrated circuit (ASIC), the like, or a combination thereof. The DSP spectrum analysis engine960can, for example, transform the digitized baseband signal into a Fourier transformed signal, which may be performed using an FFT algorithm. The FFT algorithm can produce complex values representing the respective frequency components, which may indicate a magnitude and phase offset of the baseband signal at the respective frequency components, for example, as described above with respect toFIGS. 2A and 2B.

In some example implementations, the DSP spectrum analysis engine960can output the complex values representing the frequency components. The output (e.g., the complex numbers) of the DSP spectrum analysis engine960can be applied and formatted to the I/O990, for example, for transmission to another processor, such as the CPU840ofFIG. 8. The CPU840can then store the complex values in memory850, such as a buffer, cache, or the like, for comparison with subsequently determined complex values. The CPU840can then compare complex values from a first time period to complex values of a subsequent time period, and when the numbers are different by an amount that exceeds a threshold, the CPU840can detect that movement has occurred. The CPU840can additionally compare the complex values, or the differences between complex values, with a signature that is stored in memory850. If a match is identified using the signature, the CPU840can identify the detected movement. An indication of detected movement, and in some examples, the identification of the movement, can be communicated from the CPU840through the wireless interface832or wireline interface846as discussed above inFIG. 8. In other example implementations, the DSP spectrum analysis engine960or another processor may perform one or more of the operations discussed as being performed by the CPU840.

Additionally, for other radio paths, a digitized signal can be input into the DSP spectrum analysis engine960, and the DSP spectrum analysis engine960can, for example, identify packets and frames included in the digital signal, read preambles, headers, or other control information embedded in the digital signal (e.g., based on specifications of a wireless communication standard) to identify various source devices (which may implement communications using Bluetooth, WiFi or other wireless communications). This information may be output from the DSP spectrum analysis engine960and formatted to the I/O990, for example, for transmission to the data aggregation system via one or more communication interfaces of the sensor device. This information can be used to determine how many and which devices are within an environment in which the sensor device is located.

The RF calibration (cal) tone generator970can generate RF calibration (cal) tones for diagnosing and calibration of the radio RX paths (e.g., “radio RX path1”950a, . . . “radio RX path M”950m). The radio RX paths can be calibrated, for example, for linearity and bandwidth.

In a general aspect of some of the examples described, wireless signals are used to detect movement in a space.

A first example is a motion detection process. At a wireless sensor device in a space and at a first time, a first received wireless signal based on a first transmission of a transmitted wireless signal is received. The first transmission is transmitted by a source device. By operation of a processor, a first characteristic of frequency components in a bandwidth of a first signal is determined. The first signal is based on the first received wireless signal. At the wireless sensor device and at a second, later time, a second received wireless signal based on a second transmission of the transmitted wireless signal is received. The second transmission is transmitted by the source device. By operation of the processor, a second characteristic of frequency components in the bandwidth of a second signal is determined. The second signal is based on the second received wireless signal. Movement of an object in the space is detected based on a comparison between the first characteristic and the second characteristic.

Implementations of the first example may, in some cases, include one or more of the following features. The space may be an enclosed space, and the source device can reside in the enclosed space. Determining the first characteristic and the second characteristic may include transforming, respectively, the first signal and the second signal to a frequency domain, and the first characteristic and the second characteristic may include a first set and a second set, respectively, of complex values representing magnitudes and phases of the frequency components in the bandwidth of the first signal and the second signal, respectively. Detecting the movement may include detecting that a difference between the first characteristic and the second characteristic exceeds a threshold. The transmitted wireless signal may be a transmitted radio-frequency (RF) wireless signal. The source device may comprise a second wireless sensor device in the space. A first set and a second set of complex values may be determined from the first received wireless signal and the second received wireless signal, respectively, and movement of the object based on a difference between the first set of complex values and the second set of complex values may be detected. The difference between the first set of complex values and the second set of complex values can include at least one of a difference in phase or a difference in amplitude for one or more of the frequency components. The first received wireless signal and the second received wireless signal can be filtered to generate a first output signal and a second output signal, respectively, and the first output signal and the second output signal can be down-converted to generate the first signal and the second signal, respectively.

A second example is a motion detection process. Wireless signals based on a wireless transmission repeated by a source are received at a wireless sensor device in a space. The received wireless signals are analyzed, by operation of a processor, to detect movement of objects in the space. The analysis includes determining complex values representing magnitudes and phases of respective frequency components of each of the received wireless signals, and detecting movement of an object in the space based on a change in the complex values.

Implementations of the second example may, in some cases, include one or more of the following features. Movement may be detected when the change exceeds a threshold value. Determining the complex values may include using a Fast Fourier Transform (FFT) algorithm. The wireless transmission may include a wireless radio frequency (RF) signal.

A third example is a motion detection system. The motion detection system includes a source device and a sensor device. The source device is operable to transmit a transmitted wireless signal repeatedly. The sensor device is operable to receive wireless RF signals based on the transmitted wireless signal that is transmitted multiple times. The sensor device has a processor configured to determine complex values representing magnitudes and phases of frequency components of respective signals based on the received wireless RF signals. The sensor device has a processor configured to detect motion of an object based on a comparison of the complex values.

Implementations of the third example may, in some cases, include one or more of the following features. The source device and the sensor device may be a same device. The processor may be configured to determine the complex values using a Fast Fourier Transform (FFT) algorithm. The processor may be configured to detect motion of the object when a difference between at least two of the complex values exceeds a threshold value. The sensor device may include a radio path and down-conversion circuitry, and the radio path can include a filter. The sensor device can be configured to input electronic signals of the received wireless RF signals to the radio path, and an output of the radio path may be coupled to an input of the down-conversion circuitry. The down-conversion circuitry may be operable to down-convert a RF signal to a baseband signal, and the down-conversion circuitry may be operable to output the respective signals based on the received wireless RF signals.