Motion state detection apparatus and method based on wireless signals and system
Embodiments of this disclosure provide a motion state detection apparatus and method based on wireless signals and a system, in which variations of energy distribution of reflection points with time are calculated according to wireless signals reflected from a space where an object that is detected is located, and a motion state of the object is determined according to the variations. Thus, the training of the recognition model is not needed, the detection process is simple and detection results are reliable, and are applicable to various different application scenarios.
1. A microwave radar system, comprising:
a signal transmitter configured to transmit wireless signals to a space where an object is located;
a signal receiver configured to receive wireless signals reflected;
a memory; and
a processor coupled to the memory and configured to:
calculate variations of energy distribution of reflection points with time according to the wireless signals reflected, the wireless signals being microwave radar signals; and
determine a motion state of the object detected according to the calculated variations of energy distribution of reflection points with time, the motion state comprising a stationary state and a nonstationary state,
wherein the processor is configured to:
calculate distribution of energies of the reflection points at two moments relative to at least one of position information of the object and a moving speed of the object, and
calculate a similarity between distributions at the two moments, which measures the variations of energy distribution of reflection points with time.
2. The microwave radar system according to claim 1 , wherein the at least one of position information of the object comprises:
a distance between the object and a wireless signal transmission source, or coordinates of a position where the object is located in a coordinate system established with the wireless signal transmission source as a center.
3. The microwave radar system according to claim 1 , wherein the processor is configured to:
perform one-dimensional Fourier transform, two-dimensional Fourier transform and angles of arrival estimation on the wireless signals that are reflected to obtain energies and speeds of the reflection points at the two moments and a distance between the object and a wireless signal transmission source, and
calculate distribution of energies of the reflection points at the two moments relative to the distance between the object and the wireless signal transmission source and the moving speed of the object according to the energies and speeds of the reflection points at the two moments and the distance between the object and the wireless signal transmission source.
4. The microwave radar system according to claim 1 , wherein,
the two moments respectively contain a predetermined number of frames.
5. The microwave radar system according to claim 1 , wherein,
the processor determines that the object is in the stationary state when the variations of energy distribution of reflection points with time satisfy a predetermined condition.
6. The microwave radar system according to claim 5 , wherein,
the variations of energy distribution of reflection points with time are denoted by a similarity between the distributions at the two moments, the similarity being measured by a Kullback-Leibler divergence (KL divergence) or a Jensen-Shannon divergence (JS divergence) of the distribution at the two moments, and
when the KL divergence or the JS divergence is less than a threshold, the processor determines that the object is in the stationary state.
7. The microwave radar system according to claim 1 , wherein,
the processor calculates variations of energy distribution of all reflection points or reflection points with energies greater than a threshold with time.
8. A method of motion state detection based on wireless signals, the method being applied in a microwave radar system and the method comprising:
transmitting wireless signals to a space where an object is located;
receiving wireless signals reflected;
calculating variations of energy distribution of reflection points with time according to the wireless signals reflected, the wireless signals being microwave radar signals; and
determining a motion state of the object according to the calculated variations of energy distribution of reflection points with time, the motion state comprising a stationary state and a nonstationary state,
the calculating variations of energy distribution of reflection points with time according to wireless signals reflected from a space where an object that is detected is located comprises:
calculating distribution of energies of the reflection points at two moments relative to at least one of position information of the object and a moving speed of the object, and
calculating a similarity between distributions at the two moments, which measures the variations of energy distribution of reflection points with time.