WO2016061804A1

WO2016061804A1 - Pedestrian detection

Info

Publication number: WO2016061804A1
Application number: PCT/CN2014/089399
Authority: WO
Inventors: Zeng YANG; Qingshan Zhang
Original assignee: Harman International Industries Inc
Current assignee: Harman International Industries Inc
Priority date: 2014-10-24
Filing date: 2014-10-24
Publication date: 2016-04-28
Anticipated expiration: 2017-04-24
Also published as: CN106574968B; CN106574968A

Abstract

A pedestrian detection method and a vehicle mounted communication system are provided. The methods includes: presenting a position relation between a vehicle and a pedestrian device to a user, which position relation is calculated based on angular distribution of incident power of a first and a second signal, where the first and the second signals were received by an antenna mounted on the vehicle from the pedestrian device through a wireless network at a first time point and a second time point respectively, and the first and the second signals are different from each other. By employing the method, pedestrian detection may be more convenient and more accurate, and no specific hardware is required for the vehicle.

Description

PEDESTRIAN DETECTION

TECHNICAL FIELD

The present disclosure generally relates to pedestrian detection.

BACKGROUND

Nowadays, pedestrian detection methods have emerged in driving assistance systems to improve driving safety. In some solutions, pedestrians are detected based on their Global Positioning System (GPS) data which is prone to be falsified and has poor accuracy. In some embodiments, vehicles obtain position information of pedestrians through Wi-Fi Direct. In the Wi-Fi Direct method, specific hardware is required on vehicles, which increases cost.

SUMMARY

In one embodiment, a pedestrian detection method is provided. The method includes: presenting a position relation between a vehicle and a pedestrian device to a user, which position relation is calculated based on angular distribution of incident power of a first and a second signals, where the first and the second signals are received by an antenna mounted on the vehicle from the pedestrian device through a wireless network at a first time point and a second time point respectively, and the first and the second signals are different from each other.

In some embodiments, the first and the second signals may be from a same Wi-Fi frame or two different Wi-Fi frames. In some embodiments, a Wi-Fi frame may be a probe request frame, an authentication request frame or an association request frame.

In some embodiments, the Wi-Fi frame is a response to a beacon frame broadcasted by an electronic device mounted on the vehicle, where the electronic device is configured as a Wi-Fi access point, such that the pedestrian device can detect the electronic device and send out the Wi-Fi frame.

In some embodiments, the position relation between the vehicle and the pedestrian device may include an incidence angle of the first and the second signals. In some embodiments, incident power of the first and the second signals along a plurality of angles is calculated； and one of the plurality of angles which has the greatest calculated incident power is selected as the incidence angle.

In some embodiments, the time interval between the first and the second time points may be within a range from λ/4v to 2λ/v, where λ stands for wavelength of the first and the second signals and v stands for the velocity of the vehicle.

In some embodiments, the first and the second signals may be selected from signals received by the antenna to calculate the position relation between the vehicle and the pedestrian device based on the velocity of the vehicle.

In some embodiments, the first and the second signals are decoded to obtain Media Access Control (MAC) addresses contained therein, respectively, and if the decoded MAC addresses are the same, the position relation between the vehicle and the pedestrian device is calculated based on the angular distribution of incident power of the first and the second signals.

In some embodiments, phase recovering is performed to the first and the second signals to obtain first and second corrected signals, channel estimation of the first and the second corrected signals is calculated, and the position relation is calculated based on angular distribution of incident power of the first and the second corrected signals.

In some embodiments, the position relation between the vehicle and the pedestrian device may be presented on a display screen mounted on the vehicle.

In some embodiments, the position relation between the vehicle and the pedestrian device may include a distance between the vehicle and the pedestrian device. In some embodiments, the distance between the vehicle and the pedestrian device may be calculated based on strength of the first and the second signals.

In some embodiments, after a third signal is received by the antenna from the pedestrian device through the wireless network at a third time point, the position relation is calculated based on angular distribution of incident power of the first, second and third signals.

In some embodiments, there are a plurality of antennas mounted on the vehicle. The first signal is received by the plurality of antennas from the pedestrian device at different time points respectively, the second signal is received by the plurality of antennas from the pedestrian device at different time points respectively, and the position relation is calculated based on angular distribution of incident power of the first and the second signals received by the plurality of antennas.

In one embodiment, a pedestrian detection method is provided. The method includes: an antenna mounted on a vehicle receiving a first and a second signals from a pedestrian device through a wireless network at a first position and a second position respectively； and an electronic device mounted on the vehicle calculating a position relation between the vehicle and the pedestrian device based on an estimated distance between the first and the second positions, and the first and the second signals.

In some embodiments, the position relation between the vehicle and the pedestrian device may include an incidence angle of the first and the second signals. In some embodiments, the incidence angle may be calculated using a Direction of Arrival (DOA) estimation method.

In one embodiment, a pedestrian detection system mounted on a vehicle is provided. The pedestrian detection system may include: a wireless communication device and a processing device configured to: after the wireless communication device receives, through an antenna mounted on the vehicle, a first and a second signals from a pedestrian device at a first time point and a second time point respectively, calculate a position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second signals, where the first and the second signals are different from each other； and control a presenting device to present the position relation to a user.

In some embodiments, the wireless communication device may be configured to broadcast a beacon frame as a Wi-Fi access point, such that the pedestrian device can detect the wireless communication device and send out the first and the second signals in response to the beacon frame.

In some embodiments, the first and the second signals may be from a same Wi-Fi frame or two different Wi-Fi frames. In some embodiments, the Wi-Fi frame may be a probe request frame, an authentication request frame or an association request frame.

In some embodiments, the position relation between the vehicle and the pedestrian device may include an incidence angle of the first and the second signals. In some embodiments, the processing device may be configured to: calculate incidence power of the first and the second signals along a plurality of angles； and select one from the plurality of angles which has the greatest calculated incident power as the incidence angle.

In some embodiments, the processing device may be further configured to decode the first and the second signals to obtain MAC addresses contained therein, respectively； determine whether the decoded MAC addresses are the same； and if yes, calculate the position relation between the vehicle and the pedestrian device based on the angular distribution of incident power of the first and the second signals.

In some embodiments, the processing device may be further configured to: perform phase recovering to the first and the second signals to obtain first and second corrected signals； obtain channel estimation of the first and the second corrected signals； and calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second corrected signals.

In some embodiments, the presenting device may be mounted on the vehicle. In some embodiments, the presenting device may be a displaying device.

In some embodiments, the position relation between the vehicle and the pedestrian device may include a distance between the vehicle and the pedestrian device. In some embodiments, the processing device may be further configured to: obtain strength of the first and the second signals； and calculate the distance between the vehicle and the pedestrian device based on the strength of the first and the second signals.

In some embodiments, the processing device may be further configured to: after the wireless communication device receives, through the antenna mounted on the vehicle, a third signal from the pedestrian device at a third time point, calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first, second and third signals.

In some embodiments, the processing device may be configured to: after the wireless communication device receives, through a plurality of antennas mounted on the vehicle, the first signal from the pedestrian device at different time points respectively and the second signal from the pedestrian device at different time points respectively, calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second signals received by the plurality of antennas.

In one embodiment, a pedestrian detection system mounted on a vehicle is provided. The pedestrian detection system may include: a wireless communication device and a processing device configured to: after the wireless communication device receives, through an antenna mounted on the vehicle, a first signal and a second signal from a pedestrian device at a first position and a second position respectively, calculate a position relation between the vehicle and the pedestrian device based on an estimated distance between the first and the second positions, and the first and the second signals.

In some embodiments, the position relation between the vehicle and the pedestrian device may include an incidence angle of the first and the second signals. In some embodiments, the processing device may be configured to calculate the incidence angle of the first and the second signals using a DOA estimation method.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

FIG. 1 is a schematic diagram of a sensor array.

FIG. 2 is a flow chart of a pedestrian detection method 100 according to one embodiment；

FIG. 3 is a schematic diagram of a simulated antenna array formed in the pedestrian detection method 100；

FIG. 4 is a flow chart of a pedestrian detection method 200 according to one embodiment；

FIG. 5 is a schematic diagram of a simulated antenna array formed in the pedestrian detection method 200； and

FIG. 6 is a schematic block diagram of a pedestrian detection system 300 mounted on a vehicle according to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

In communication technology, Direction of Arrival (DOA) estimation is commonly used for signal source location. In signal processing literature, DOA denotes the direction from which usually a propagating wave arrives at a point, where usually a set of sensors are located. The set of sensors forms what is called a sensor array. FIG. 1 illustrates a sensor array, including a plurality of sensors 1 to N. The sensor array is configured to receive signals and sensors in the array are uniformly arranged with a distance interval d. Assume a signal source s (t) impinges on the sensor array with an incidence angle θ₀, and a propagation speed of the signal is the speed of light c. Referring to FIG. 1, if the received signal at sensor 1 is x₁ (t) ＝s (t) , the signal will be received by sensor i (i＝1, 2, …, N) with a delay of △_i given by Equation (1) :

Those skilled in the art can understand that a delay of a signal represents a phase shift. Therefore, the signal x_i (t) received at sensor i may be represented by Equation (2) :

where ω is an angular frequency of a beam carrying the signals x_i (t) .

In DOA beamforming technology, the beam is steered through all look directions to find DOA of an incident signal by adjusting the delay or phase shift. The delay or phase shift w_i of a beamformer on the i^th sensor is represented by a “look” angle θ, and an output of the beamformer is given by Equation (3) :

Based on Equation (2) and Equation (3) , Equation (4) is obtained:

where |y (t) |² is a power value of the output of the beamformer and indicates incident power of the received signal, and Equation (4) indicates angular distribution of the incident power of the received signal.

From Equation (4) , the power value of the output of the beamformer reaches a maximum value |Ns (t) |² when θ＝θ₀. Therefore, based on Equation (4) , when the “look” angle θ enables the power value of the output of the beamformer to be maximum, a value of the “look” angle θ can be considered as a value of the incidence angle θ₀. In this manner, the DOA is estimated.

To detect pedestrians, a vehicle may calculate a direction of a pedestrian based on the DOA technology. From above, a primary condition of using the DOA estimation technology is that the vehicle receives a signal from the pedestrian. In some embodiments, to enable a pedestrian device to send a signal to the vehicle, the vehicle may perform a wireless connection establishment process with the pedestrian device, for example, a Wi-Fi connection establishment process. During the process, the vehicle can obtain Wi-Fi frames from the pedestrian device. Based on the Wi-Fi frames, the vehicle may determine the direction of the pedestrian to realize pedestrian detection.

FIG. 2 illustrates a flow chart of a pedestrian detection method 100 according to one embodiment.

Referring to FIG. 2, in S101, a vehicle broadcasting a beacon frame as a Wi-Fi access point.

In some embodiments, the vehicle may be configured as a Wi-Fi access point and broadcast beacon frames periodically so that clients around (for example, a pedestrian device) can detect the access point. In some embodiments, after detecting the Wi-Fi access point based on the beacon frame, clients, such as pedestrian devices, may send a probe request frame as a response to the beacon frame to the access point to connect to it.

In some embodiments, the vehicle may employ a Service Set Identifier (SSID) within a predetermined SSID range. Pedestrian devices in need of this pedestrian detection application may set a higher priority to vehicles whose SSIDs are within the predetermined SSID range, while other pedestrian devices may set a lower priority to the vehicles whose SSIDs are within the predetermined SSID range.

In S103, receiving a plurality of signals from a pedestrian device at a plurality of positions and at a plurality of time points respectively through one antenna.

Referring to FIG. 3, FIG. 3 illustrates a schematic diagram of a simulated antenna array formed in the pedestrian detection method 100. In some embodiments, there is one antenna mounted on the vehicle. As the vehicle moves, the antenna may receive signals at successive locations along its moving direction at different time points, as if several antennas are respectively arranged at the successive locations. Therefore, a simulated antenna array is formed, which is the base of employing the DOA technology to determine an incidence angle of the received signals, thereby a direction of the pedestrian is obtained.

It should be noted that, the vehicle may receive various signals during driving, such as signals from pedestrian devices, signals from other vehicles or noises. The plurality of signals may be a portion of the various signals, which are selected for subsequent calculation.

It should be noted that, receiving a plurality of signals at a plurality of positions and at a plurality of time points respectively means receiving one signal at each of the plurality of positions and at each of the plurality of time points. In some embodiments, receiving a signal from the pedestrian device at a time point means the vehicle actively sampling the signal sent from the pedestrian device at the time point.

In some embodiments, the plurality of signals are contained in one frame, such as a Wi-Fi frame (for example, a probe request frame) , sent by the pedestrian device carried by a pedestrian. In some embodiments, the plurality of signals may be contained in other frames, such as an authentication request frame or an association request frame. In some embodiments, the plurality of signals are contained in different Wi-Fi frames sent by the pedestrian device.

Referring to FIG. 3, the vehicle V₀ is travelling along a v-axis direction and an antenna 1 is mounted on the vehicle V₀. When drives to a first position P₁, the antenna 1 receives a first signal s₁ (t) at a first time point t₁. When drives to a second position P₂, the antenna 1 receives a second signal s₂ (t) at a second time point t₂. When drives to a third position P₃, the antenna 1 receives a third signal s₃ (t) at a third time point t₃. When drives to a fourth position P₄, the antenna 1 receives a fourth signal s₄ (t) at a fourth time point t₄. In this example, the first, second, third and fourth signals, contained in a Wi-Fi frame, are broadcasted by the pedestrian device via an electromagnetic wave. Further, wavelength of the Wi-Fi frame is much greater than a distance between the vehicle V₀ and the pedestrian. Therefore, an incidence angle of the plurality of signals can be considered as a same value θ.

In some embodiments, once receiving a signal from the pedestrian device, the vehicle may decode the signal to obtain a MAC address therein to identify the pedestrian device. In some embodiments, the vehicle may decode the plurality of signals to obtain MAC addresses contained therein, respectively； determine whether the decoded MAC addresses are the same； and if yes, determine that the plurality of signals are sent from the same pedestrian device and can be used in subsequent calculation.

In some embodiments, for example, in a crowded scenario, the vehicle may receive Wi-Fi frames from a plurality of pedestrian devices for connecting with the vehicle. To avoid channel mitigation, the vehicle may reject requests of some of the plurality of pedestrian devices, only performing a Wi-Fi connection establishment process with a portion of the plurality of pedestrian devices.

In S105, performing phase recovering to the plurality of signals to obtain a plurality of corrected signals.

To use the DOA estimation technology in pedestrian detection, phase continuity of the plurality of signals should be ensured. In some embodiments, once receiving a signal from the pedestrian device, the vehicle may perform phase recovering to the signal to obtain a corrected signal. For example, the vehicle may estimate a frequency offset of the received signal and perform corresponding compensation to the received signal based on the estimated frequency offset.

In S107, obtaining channel estimation of the plurality of corrected signals.

In some embodiments, the plurality of signals may be contained in a Wi-Fi frame, that is, the plurality of signals are 802.11 Orthogonal Frequency Division Multiplexing (OFDM) symbols substantially. Therefore, the plurality of corrected signals may correspond to channel estimation for certain pilots.

Similar to a scenario of the sensor array described above, the channel estimation of the plurality of corrected signals corresponds to x_i (t) in Equation (3) .

In S109, estimating distances between each of the plurality of positions and a first position of the plurality of positions based on the plurality of time points and the velocity of the vehicle.

The first position of the plurality of positions means a position where the vehicle first receives one of the plurality of signals at a first time point.

In some embodiments, the distances may be calculated based on the velocity of the vehicle and time intervals between each of the plurality of time points and the first time point. In some embodiments, the velocity of the vehicle may be obtained from a sensor mounted on the vehicle.

To employ the DOA technology, a distance interval between adjacent positions among the plurality of positions may be within a suitable range, such as

where λ is wavelength of the plurality of signals, to ensure calculation accuracy. Namely, the time interval between adjacent time points among the plurality of time points may be within a suitable range, such as λ/4v～2λ/v. In some embodiments, the plurality of signals are contained in a Wi-Fi frame. In some embodiments, an operating frequency of Wi-Fi technology may be 2.4GHz or 5.8GHz. Taking the operating frequency of 5.8GHz for example, the wavelength is 0.05 meters, and the distance interval may be within a range from 0.01 meters to 0.1 meters accordingly. Assuming the velocity of the vehicle is 60Km/h, a time interval between adjacent time points among the plurality of time points is around 0.6ms to 6ms. That is to say, the vehicle may sample signals every 0.6ms to 6ms to ensure the calculation accuracy. Considering a length of a Wi-Fi frame is about 2ms, if the vehicle obtains each of the plurality of signals every 0.6ms, the plurality of signals may include three or four signals.

In some embodiments, the greater the velocity of vehicle is, the shorter the time interval between the adjacent time points is and the more signals the vehicle samples, which leads to higher calculation accuracy.

In S111, calculating a position relation between the vehicle and the pedestrian device based on the channel estimation of the plurality of corrected signals, and the estimated distances between each of the plurality of positions and the first position of the plurality of positions.

In some embodiments, the position relation between the vehicle and the pedestrian device may include an incidence angle of the plurality of signals. In some embodiments, the incidence angle represents an angle between a first straight line defined by the pedestrian and the antenna of the vehicle and a second straight line which is perpendicular to a vehicle length direction. For example, in FIG. 3, the incidence angle θ is used to represent the position relation between the vehicle V₀ and the pedestrian device.

Based on the simulated antenna array, the incidence angle can be calculated based on Equation (3) . In the scenario of the sensor array, the sensors are arranged with a same distance interval d. However, in some embodiments, the distances between the adjacent positions among the plurality of positions may not be the same. Therefore, Equation (3) needs to be modified to satisfy pedestrian detection application. In some embodiments, the incidence angle of the received signals may be calculated based on Equation (5) , which is obtained from Equation (3) and indicates angular distribution of incident power of the plurality of signals:

where |y (t) |² is a power value of an output of a beamformer formed based on the plurality of signals and indicates the incident power of the plurality of signals,

ω is an angular frequency of the plurality of signals, t_i is the time point receiving each of the plurality of signals, v is the velocity of the vehicle, θ is the incidence angle of the plurality of signals, c is the speed of light, and x_i (t) is the channel estimation of the plurality of corrected signals.

Based on the DOA estimation technology, as the frequency of the plurality of signals and the light of speed are known, and the time intervals, the velocity of the vehicle and the channel estimation of the plurality of corrected signals are obtained, a value of the incidence angle θ which enables |y (t) |² to be the maximum value is the incidence angle of the plurality of signals received from the pedestrian device. In this manner, a direction of the pedestrian is obtained.

In some embodiments, if the calculated incidence angle θ is greater than 0°, the vehicle may determine that the pedestrian device locates in a direction (90-θ) degrees away from a driving direction of the vehicle. In some embodiments, if the calculated incidence angle θ is smaller than 0°, the vehicle may determine that the pedestrian device locates in a direction (90+θ) degrees away from a direction opposite to the driving direction of the vehicle.

For example, referring to FIG. 3, if the calculated incidence angle θ is 30°, the vehicle V₀ may determine that the pedestrian locates in a direction 60 degrees away from the driving direction of the vehicle V₀.

In some embodiments, the position relation may further include a distance between the vehicle and the pedestrian device. In some embodiments, the vehicle may obtain strength of the plurality of signals and further obtain the distance between the vehicle and the pedestrian device based on the strength of the plurality of signals. Combining the direction of the pedestrian device and the distance between the vehicle and the pedestrian device, location of the pedestrian may be more accurate.

It should be noted that, the vehicle may not necessarily have internet access. The vehicle exchanges Wi-Fi frames with the pedestrian device for calculating the position relation between the vehicle and the pedestrian device. That is to say, the vehicle may not actually establish Wi-Fi connection with the pedestrian device.

In some embodiments, if the vehicle obtains the position relation between the vehicle and the pedestrian device after receiving the plurality of signals contained in the Wi-Fi frame from the pedestrian device, the vehicle may reject a connection request from the pedestrian device. For example, after the vehicle calculates an incidence angle of a probe request frame received from the pedestrian device, the vehicle may not send a probe response frame to the pedestrian device.

In some embodiments, if the vehicle fails to calculate the position relation based on the plurality of signals, the vehicle may continue to perform the Wi-Fi connection establishment process with the pedestrian device, that is, the vehicle continues to exchange Wi-Fi frames with the pedestrian device. For example, if the vehicle determines that the plurality of signals contained in the probe request frame are not enough to obtain the position relation based on the DOA estimation technology, the vehicle may send a probe response frame to the pedestrian device, so that the pedestrian device may send an authentication request frame to the vehicle, which gives the vehicle another chance to calculate position information of the pedestrian device.

In S113, presenting the position relation between the vehicle and the pedestrian device to a driver in the vehicle.

In some embodiments, based on the incidence angle of the plurality of signals, the direction of the pedestrian may be displayed on a screen for assisting driving. In some embodiments, the direction of the pedestrian may be informed to the driver through an acoustic signal.

In some embodiments, the vehicle may share calculated position information of the pedestrian with other vehicles around through Vehicular Ad Hoc Networks (VANET) . The vehicle may also obtain estimated position information of the pedestrian device from other vehicles. Therefore, the vehicle may obtain more accurate position information of the pedestrian by combining the position information calculated by itself with the position information estimated by other vehicles.

In some embodiments, the pedestrian device may add some related information into the frame carrying the plurality of signals. In some embodiments, the related information may include the pedestrian’s GPS data, heading, velocity and etc. The vehicle may combine the related information with the calculated position information of the pedestrian device to obtain better pedestrian location.

In some embodiments, the more antennas the vehicle is provided with, the more signals the vehicle receives and the more accurate the pedestrian detection is. In some embodiments, considering costs of antennas, a number of the antennas may be within a suitable range, such as one to four or one to eight.

FIG. 4 illustrates a flow chart of a pedestrian detection method 200 according to one embodiment.

Referring to FIG. 4, in S201, a vehicle broadcasting a beacon frame as a Wi-Fi access point.

In some embodiments, the vehicle broadcasts beacon frames periodically as a Wi-Fi access point to attract client devices around to request to connect with it.

In S203, receiving a plurality of signals from a pedestrian device at a plurality of positions and at a plurality of time points respectively through two antennas.

In some embodiments, after receiving the beacon frame from the vehicle, pedestrian devices around as a client device may send a probe request frame to the vehicle. In some embodiments, the plurality of signals may be contained in the probe request frame. In some embodiments, the plurality of signals may be contained in other frames, such as an authentication request frame or an association request frame. In some embodiments, the two antennas may be arranged along a vehicle length direction, i.e., a driving direction of the vehicle.

Referring to FIG. 5, the vehicle V₁ is moving along a v’-axis direction. An antenna 1 mounted on the vehicle V₁ receives a first signal s’₁ (t) at a first position P’₁ and at a first time point t’₁, an antenna 2 mounted on the vehicle V₁ receives the first signal s’₁(t) at a second position P’₂ and at a second time point t’₂, the antenna 1 receives a second signal s’₂ (t) at a third position P’₃ and at a third time point t’₃, and the antenna 2 receives the second signal s’₂ (t) at a fourth position P’₄ and at a fourth time point t’₄.

In S205, performing phase recovering to the plurality of signals to obtain a plurality of corrected signals.

To use the DOA estimation technology in pedestrian detection, phase continuity of the plurality of signals should be ensured. Therefore, phase recovering is necessarily performed to the plurality of signals.

In S207, obtaining channel estimation of the plurality of corrected signals.

In some embodiments, channel estimation of the plurality of corrected signals may be obtained for facilitating subsequent calculation of an incidence angle of the plurality of signals.

In S209, estimating distances between each of the plurality of positions and a first position of the plurality of positions based on the plurality of time points, the velocity of the vehicle and an interval between the two antennas.

The first position of the plurality of positions means a position where the vehicle first receives one of the plurality of signals at a first time point. In some embodiments, the distances may be calculated based on the velocity of the vehicle, time intervals between each of the plurality of time points and the first time point, and the interval between the two antennas. In some embodiments, the velocity of the vehicle may be obtained from a sensor mounted on the vehicle.

Referring to FIG. 5, a first distance d’₁ between the first position P’₁ and the second position P’₂ may be calculated based on a time interval between the first time point t’₁ and the second time point t’₂, the velocity of the vehicle V₁ and an interval between the two

antennas

1 and 2. A second distance (d’₁+d’₂) between the first position P’₁ and the third position P’₃ may be calculated based on a time interval between the first time point t’₁ and the third time point t’₃, and the velocity of the vehicle V₁. A third distance (d’₁+d’₂+d’₃) between the first position P’₁ and the fourth position P’₄ may be calculated based on a time interval between the first time point t’₁ and the fourth time point t’₄, and the velocity of the vehicle V₁.

In S211, calculating an incidence angle of the plurality of signals based on the channel estimation of the plurality of corrected signals, and the estimated distances between each of the plurality of positions and the first position of the plurality of positions.

Referring to FIG. 5, similar to the above embodiment, the incidence angle θ’ may be calculated based on Equation (6) which indicates angular distribution of incident power of the plurality of signals:

where |y’ (t) |² is a power value of an output of a beamformer formed based on the plurality of signals and indicates the incident power of the plurality of signals,

ω is an angular frequency of the plurality of signals, d_i is the distance between one of the plurality of positions and the first position of the plurality of positions, θ’ is the incidence angle of the plurality of signals, c is the speed of light, and x_i (t) is the channel estimation of the plurality of corrected signals.

Based on the DOA estimation technology, a value of the incidence angle θ’ which enables |y’ (t) |² to be the maximum value is the incidence angle of the plurality of signals received from the pedestrian device. In this manner, a direction of the pedestrian is obtained.

In S213, presenting the position relation between the vehicle and the pedestrian device to a driver in the vehicle.

In some embodiments, the vehicle may display the position relation on a screen to a driver for assisting driving. For example, an arrow may be displayed pointing to the position of the pedestrian.

From above, based on movement of a vehicle provided with at least one antenna, a simulated antenna array may be formed on the vehicle. When the simulated antenna array receives signals from a pedestrian device carried by a pedestrian, the vehicle may calculate direction information of the pedestrian based on the received signals using the DOA estimation technology. Therefore, pedestrian detection may be realized.

FIG. 6 illustrates a schematic block diagram of a pedestrian detection system 300 mounted on a vehicle according to one embodiment. Referring to FIG. 6, the pedestrian detection system 300 includes an antenna 301, a wireless communication device 303, a processing device 305, a displaying device 307 and a memory device 309.

The antenna 301 may be configured to receive external signals and send the received signals to the wireless communication device 303. The wireless communication device 303 may be configured to broadcast beacon frames periodically as a Wi-Fi access point to attract pedestrian devices to send Wi-Fi frames to itself. In some embodiments, after broadcasting a beacon frame, the wireless communication device 301 may obtain a plurality of signals from a pedestrian device at a plurality of positions and at a plurality of time points respectively through the antenna 301. In some embodiments, the plurality of signals are contained in one frame, such as a Wi-Fi frame (for example, a probe request frame) , sent by the pedestrian device carried by a pedestrian. In some embodiments, the plurality of signals may be contained in other frames, such as an authentication request frame or an association request frame. In some embodiments, the plurality of signals may be contained in different Wi-Fi frames sent by the pedestrian device.

In some embodiments, a distance between adjacent positions among the plurality of positions may be within a range from a quarter of wavelength of the plurality of signals to twice of the wavelength.

In some embodiments, the processing device 305 may be further configured to decode the plurality of signals to obtain MAC addresses contained therein, respectively； determine whether the decoded MAC addresses are the same； and if yes, determine that the plurality of signals are sent from the same pedestrian device and can be used in subsequent calculation.

In some embodiments, the processing device 305 may be further configured to perform phase recovering to the plurality of signals to obtain a plurality of corrected signals to ensure phase continuity of the plurality of signals； obtain channel estimation of the plurality of corrected signals； estimate distances between each of the plurality of positions and a first position of the plurality of positions based on the plurality of time points and the velocity of the vehicle； and calculate a position relation between the vehicle and the pedestrian device based on the channel estimation of the plurality of corrected signals, and the estimated distances between each of the plurality of positions and the first position of the plurality of positions. In some embodiments, the first position of the plurality of positions means a position where the vehicle first receives one of the plurality of signals at a first time point. In some embodiments, the distances may be estimated based on the velocity of the vehicle and time intervals between each of the plurality of time points and the first time point.

In some embodiments, the position relation between the vehicle and the electronic device may refer to an incidence angle of the plurality of signals. In some embodiments, the incidence angle represents an angle between a straight line defined by the pedestrian and the antenna of the vehicle and a straight line which is perpendicular to a vehicle length direction. In some embodiments, the processing device 305 may be configured to calculate the incidence angle of the plurality of signals based on Equation (5) which indicates angular distribution of incident power of the plurality of signals:

ω is an angular frequency of the plurality of signals, ti is the time point receiving each of the plurality of signals, v is the velocity of the vehicle, θ is the incidence angle of the plurality of signals, c is the speed of light, and x_i (t) is the channel estimation of the plurality of corrected signals.

In some embodiments, a value of the incidence angle θ which enables |y (t) |² to be the maximum value is the incidence angle of the plurality of signals received from the pedestrian device. In some embodiments, the processing device 305 may be configured to determine a direction of the pedestrian based on the incidence angle θ.

In some embodiments, the processing device 305 may be further configured to calculate a distance between the vehicle and the pedestrian based on strength of the plurality of signals； and obtain a position of the pedestrian based on the direction of the pedestrian and the distance between the vehicle and the pedestrian.

In some embodiments, the processing device 305 may be further configured to control the displaying device 307 to present the direction or position of the pedestrian device to a driver in the vehicle.

In some embodiments, if the processing device 305 calculates the incidence angle of the plurality of signals or if the vehicle receives position information of the pedestrian from other vehicles, the processing device 305 may be further configured to control the wireless communication device 303 to reject a connection request from the pedestrian device. For example, the processing device 305 may not send a probe response frame to the pedestrian device.

In some embodiments, if it is determined that the plurality of signals are not enough to obtain the position relation, the processing device 305 may be further configured to control the wireless communication device 303 to continue the Wi-Fi connection establishment process with the pedestrian device.

In some embodiments, the processing device 305 may be configured to control a transmitter to broadcast the direction of the pedestrian. In some embodiments, a receiver in the vehicle may receive position information of the pedestrian from other vehicles. The processing device 305 may be further configured to determine the position of the pedestrian based on the direction of the pedestrian it calculates and the position information of the pedestrian received from other vehicles.

In some embodiments, the processing device 305 may be a CPU, or a MCU, or a DSP etc. , or any combination thereof. The memory device 309 may store an operating system and program instructions.

In some embodiments, there are a plurality of antennas 301 mounted on the vehicle. The wireless communication device 303 may be configured to obtain a plurality of signals from the pedestrian device at different positions and at different time points respectively through the plurality of antennas 301. The processing device 305 may be configured to calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the plurality of signals.

According to one embodiment, a non-transitory computer readable medium, which contains a computer program for pedestrian detection, is provided. When the computer program is executed by a processor, it will instruct the processor to: present a position relation between a vehicle and a pedestrian device to a user, which position relation is calculated based on angular distribution of incident power of a first and a second signals, where the first and the second signals were received by an antenna mounted on the vehicle from the pedestrian device through a wireless network at a first time point and a second time point respectively, and the first and the second signals are different from each other.

There is little distinction left between hardware and software implementations of aspects of systems； the use of hardware or software is generally a design choice representing cost vs. efficiency tradeoffs. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a mainly hardware and/or firmware vehicle； if flexibility is paramount, the implementer may opt for a mainly software implementation； or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

A pedestrian detection method, comprising:

presenting a position relation between a vehicle and a pedestrian device to a user, which position relation is calculated based on angular distribution of incident power of a first and a second signals,

where the first and the second signals are received by an antenna mounted on the vehicle from the pedestrian device through a wireless network at a first time point and a second time point respectively, and the first and the second signals are different from each other.
The method according to claim 1, wherein the first and the second signals are from a same Wi-Fi frame or two different Wi-Fi frames.
The method according to claim 2, wherein the Wi-Fi frame is a response to a beacon frame broadcasted by an electronic device mounted on the vehicle.
The method according to claim 1, wherein the position relation between the vehicle and the pedestrian device comprises an incidence angle of the first and the second signals.
The method according to claim 4, wherein incident power of the first and the second signals along a plurality of angles is calculated, and one of the plurality of angles which has the greatest calculated incident power is selected as the incidence angle.
The method according to claim 1, wherein the time interval between the first and the second time points is within a range from λ/4v to 2λ/v, where λ stands for wavelength of the first and the second signals and v stands for the velocity of the vehicle.
The method according to claim 1, wherein the first and the second signals are decoded to obtain Media Access Control (MAC) addresses contained therein, respectively, and if the decoded MAC addresses are the same, the position relation is calculated based on the angular distribution of incident power of the first and the second signals.
The method according to claim 1, wherein phase recovering is performed to the first and the second signals to obtain a first and a second corrected signals, channel estimation of the first and the second corrected signals is calculated, and the position relation is calculated based on angular distribution of incident power of the first and the second corrected signals.
The method according to claim 1, wherein after a third signal is received by the antenna from the pedestrian device through the wireless network at a third time point, the position relation is calculated based on angular distribution of incident power of the first, second and third signals.
The method according to claim 1, wherein there are a plurality of antennas mounted on the vehicle, where the first signal is received by the plurality of antennas from the pedestrian device at different time points respectively, the second signal is received by the plurality of antennas from the pedestrian device at different time points respectively, and the position relation is calculated based on angular distribution of incident power of the first and the second signals received by the plurality of antennas.
A pedestrian detection system mounted on a vehicle, comprising: a wireless communication device and a processing device configured to:

after the wireless communication device receives, through an antenna mounted on the vehicle, a first and a second signals from a pedestrian device at a first time point and a second time point respectively, calculate a position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second signals, where the first and the second signals are different from each other； and

control a presenting device to present the position relation to a user.
The pedestrian detection system according to claim 11, wherein the wireless communication device is further configured to broadcast a beacon frame as a Wi-Fi access point.
The pedestrian detection system according to claim 12, wherein the first and second signals are from a same Wi-Fi frame or two different Wi-Fi frames sent from the pedestrian device.
The pedestrian detection system according to claim 11, wherein the position relation between the vehicle and the pedestrian device comprises an incidence angle of the first and the second signals.
The pedestrian detection system according to claim 14, wherein the processing device is configured to:

calculate incidence power of the first and the second signals along a plurality of angles； and

select one from the plurality of angles which has the greatest calculated incident power as the incidence angle.
The pedestrian detection system according to claim 11, wherein the time interval between the first and the second time points is within a range from λ/4v to 2λ/v, where λ stands for wavelength of the first and the second signals and v stands for the velocity of the vehicle.
The pedestrian detection system according to claim 11, wherein the processing device is further configured to:

decode the first and the second signals to obtain MAC addresses contained therein, respectively；

determine whether the decoded MAC addresses are the same； and

if yes, calculate the position relation between the vehicle and the pedestrian device based on the angular distribution of incident power of the first and the second signals.
The pedestrian detection system according to claim 11, wherein the processing device is further configured to:

perform phase recovering to the first and the second signals to obtain first and second corrected signals；

obtain channel estimation of the first and the second corrected signals； and

calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second corrected signals.
The pedestrian detection system according to claim 11, wherein the processing device is further configured to: after the wireless communication device receives, through the antenna mounted on the vehicle, a third signal from the pedestrian device at a third time point, calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first, second and third signals.
The pedestrian detection system according to claim 11, wherein the processing device is further configured to: after the wireless communication device receives, through a plurality of antennas mounted on the vehicle, the first signal from the pedestrian device at different time points respectively and the second signal from the pedestrian device at different time points respectively, calculate the position relation between the vehicle and the pedestrian device based on angular distribution of incident power of the first and the second signals received by the plurality of antennas.