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Micro-Doppler signature contribution of range bins containing scatterers, where bin1 corresponds to 24.7310 m and each bin is .0375m apart. Bin 8 and bin 9 contain no target scatterers so were not included.
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This paper considers how the estimation of radar target micro-motions may be combined with localization of scattering centers leading to a niche data set to describe complex targets. Micro-Doppler signature analysis has been demonstrated as an effective way to acquire information about a target by estimating its unique micro-motions. Targets have a...
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Context 1
... [23]. The spectrogram provides the Doppler response of all of the scattering centers of the person. Conversely, the spatial distributions of the scattering centers producing each distinct Doppler component cannot be determined. When a wideband waveform is used to illuminate the target, the situation is quite different to the narrowband case. Fig. 4 shows the collection of range profiles over time for the same target as considered in Fig. 2. The individual scattering centers of the target are now clearly discernable in range and the slight change in range as the target moves is visible. However, this increase in spatial information comes at a cost: it is no longer possible to ...
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... three dimensional view of the data in [15], [24] respectively, but do not provide detailed analysis. The results of taking the STFT in every range bin produces multiple spectrograms that show the micro-motions of all the scattering centers at a specific location. The spectrograms of range bins that contain scatterers from the simulation are shown Fig. 4. narrowband system in Fig. 3 assuming their scattering center properties do not vary over the bandwidth for the wideband system. It can be seen that over time the scattering centers move in and out of range bins. When there is a target present in the range bin, the frequency of the scatterer can be determined easily. It can also be ...
Context 3
... centers in each range bin can be approximated. One approach is to use a local maxima search on the spectrogram data of each range bin. Here, a threshold of -10 dB from the maximum value was found to give a good estimate of the local maxima while excluding sidelobes and noise. The locations of the local maxima corresponding to bin 11 from Fig. 4 is seen in Fig. 6. This process of local maxima extraction can be repeated for the spectrogram data of each range bin. Using the local maxima extraction results for each range bin, a sum of number of discrete frequency contributors in each range bin over time is shown in Fig. 7 depicting the number of components over time in range. ...
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Citations
... The Doppler effects occur when either a wave source or a target is in motion. The magnitude of a frequency difference between the emitted signal and the reflected signal is proportional to the relative velocity between the wave sensor and the target [22][23][24]. Figure 1 illustrates that the radar sensor is fixed, so only the target movement can generate the Doppler frequency. A voltage-controlled oscillator (VCO) generates a carrier wave, and the corresponding signal is transmitted via the TX antenna, which goes into a mixer at the same time. ...
... Both the transmission and the reflected waves, with frequencies of f T X and f R X , are fed into the mixer and mixed into the Doppler frequency. difference between the emitted signal and the reflected signal is proportional to the relative velocity between the wave sensor and the target [22][23][24]. Figure 1 illustrates that the radar sensor is fixed, so only the target movement can generate the Doppler frequency. A voltage-controlled oscillator (VCO) generates a carrier wave, and the corresponding signal is transmitted via the TX antenna, which goes into a mixer at the same time. ...
Hand gesture recognition, which is one of the fields of human–computer interaction (HCI) research, extracts the user’s pattern using sensors. Radio detection and ranging (RADAR) sensors are robust under severe environments and convenient to use for hand gestures. The existing studies mostly adopted continuous-wave (CW) radar, which only shows a good performance at a fixed distance, which is due to its limitation of not seeing the distance. This paper proposes a hand gesture recognition system that utilizes frequency-shift keying (FSK) radar, allowing for a recognition method that can work at the various distances between a radar sensor and a user. The proposed system adopts a convolutional neural network (CNN) model for the recognition. From the experimental results, the proposed recognition system covers the range from 30 cm to 180 cm and shows an accuracy of 93.67% over the entire range.
... Sensing-related problems include lighting conditions (poor illumination), thermal conditions (increased radiative heat), occlusion, and atmospheric phenomena (fog, mirages). Besides these, radar-based systems are independent of privacy-related conditions since the target information does not rely explicitly on target shapes but can be derived from microscale movements based on micro-Doppler signatures [33][34][35][36][37][38]. ...
... For example, in [40], PCA was used to determine the histogram of the most influencing PC for a given time window, from which the mean and variance were used as features. Another example is [37], where the number of discrete frequency components was determined using spectrograms that contain micro-Doppler signatures, providing useful information about the locations of small-scale motions. ...
The importance of radar-based human activity recognition has increased significantly overthe last two decades in safety and smart surveillance applications due to its superiority in vision-based sensing in the presence of poor environmental conditions like low illumination, increasedradiative heat, occlusion, and fog. Increased public sensitivity to privacy protection and the progressof cost-effective manufacturing have led to higher acceptance and distribution of this technology.Deep learning approaches have proven that manual feature extraction that relies heavily on processknowledge can be avoided due to its hierarchical, non-descriptive nature. On the other hand, MLtechniques based on manual feature extraction provide a robust, yet empirical-based approach, wherethe computational effort is comparatively low. This review outlines the basics of classical ML- andDL-based human activity recognition and its advances, taking the recent progress in both categoriesinto account. For every category, state-of-the-art methods are introduced, briefly explained, and theirrelated works summarized. A comparative study is performed to evaluate the performance andcomputational effort based on a benchmarking dataset to provide a common basis for the assessmentof the techniques’ degrees of suitability.
... Sensing-related problems include lighting conditions (poor illumination), thermal conditions (increased radiative heat), occlusion, and atmospheric phenomena (fog, mirages). Besides these, radar-based systems are independent of privacy-related conditions since the target information does not rely explicitly on target shapes but can be derived from microscale movements based on micro-Doppler signatures [33][34][35][36][37][38]. ...
... For example, in [40], PCA was used to determine the histogram of the most influencing PC for a given time window, from which the mean and variance were used as features. Another example is [37], where the number of discrete frequency components was determined using spectrograms that contain micro-Doppler signatures, providing useful information about the locations of small-scale motions. ...
The importance of radar-based human activity recognition increased significantly over the last two decades in safety and smart surveillance applications due to its superiority towards vision-based sensing in the presence of poor environmental conditions, like illumination, increased radiative heat, occlusion, and fog. An increased public sensitivity for privacy protection, and the progress of cost-effective manufacturing, led to a higher acceptance and distribution. Deep learning approaches proved that the manual feature extraction that relies heavily upon process knowledge can be avoided by its hierarchical, non-descriptive nature. On the other hand, ML techniques based on manual feature extraction provide a robust, yet empirical based approach where the computational effort is comparatively low. This review outlines the basics of classical ML- and DL-based human activity recognition and its advances while taking recent progress of both categories into regard. For every category, state-of-the-art methods are introduced, briefly explained and discussed in terms of their pros, cons and gaps. A comparative study is performed to evaluate the performance and computational effort based on a benchmarking data set to provide a common basis for the assessment of the techniques’ degree of suitability.
... Ultra-wideband range-Doppler radar with 2.5-GHz bandwidth is used in Sachs and Herrmann (2015) to provide range information for target localization. Range-Doppler radars are also used in Cammenga et al. (2015) to detect physiological (heartbeat, respiration) and motion parameters to identify a fallen person. Characteristics corresponding to the detected heartbeat, respiration, and motion, or combinations thereof, are proposed to differentiate between an animal present in the room and the fallen person. ...
... Characteristics corresponding to the detected heartbeat, respiration, and motion, or combinations thereof, are proposed to differentiate between an animal present in the room and the fallen person. A range-Doppler radar can also resolve targets and thereby permits the radar to handle more Emerging technologies for in-home care for the elderly, frail, and vulnerable adults than one person in the field of view (e.g., Cammenga et al., 2015). In this case, both the intended elderly and other person(s) in the room would be monitored. ...
To Cite this Chapter: Balakrishnan S, El Ansari W, Dakua SP. (2024) Emerging technologies for in-home care for the elderly, frail, and vulnerable adults. In: Artificial intelligence, Big data, blockchain and 5G for digital transformation of the healthcare industry: A movement towards more resilient and inclusive societies. Patricia Ordoñez de Pablos and Xi Zhang (Eds). Elsevier, pp. 21-40.
This chapter explores emerging radar-based fall detection systems for in-home care of elderly, frail, and vulnerable adults. It discusses the potential benefits, clinical evidence, and real-world applications while addressing the practical challenges, ethical, legal, and social considerations. The chapter emphasizes the importance of continued research, user-centered design, and integration with other technologies to improve the quality of life and safety for this population.
... In the framework of wave scattering problems, the Doppler effect [11,23] characterizes the property that the motion of a target modulates the frequency of the reflected signal initially emitted by a source. For motions with uniform velocity, the Doppler frequency shift can be easily obtained [9] while for more general movements it is estimated by combining simple models and signal processing techniques [6,7,11,12,24,29,32]. During the last years, the radar detection of non uniformly moving scatterers was applied to a wide variety of problems because of the availability of newly designed high-frequency sensors and devices. ...
... A crucial advantage of high-frequency radar sensing is its sensitivity to micro movements (see e.g. [11,12]) of obstacles involving several moving parts, which results in the micro-Doppler effect [11,12] used nowadays in many applications [1,4,7,12,21]. In the automotive industry, micro-Doppler sensing has recently been applied with success [17,24,27,29] to the contactless detection of vital signs, in particular for the breathing of children left alone on the back seat of overheating cars. ...
... In the framework of wave scattering problems, the Doppler effect [25,52] characterizes the property that the motion of a target modulates the frequency of the reĆected signal initially emitted by a source. For motions with uniform velocity, the Doppler frequency shift can be easily obtained [23] while for more general movements it is estimated by combining simple models and signal processing techniques [19,20,25,27,53,67,70]. During the last years, the radar detection of non uniformly moving scatterers was applied to a wide variety of problems because of the availability of newly designed high-frequency sensors and devices. ...
... Furthermore, the THz frequency range will be used in the coming years (e.g. at the frequency 140 GHz). A crucial advantage of high-frequency radar sensing is its sensitivity to micro movements of obstacles involving several moving parts, which results in the micro-Doppler effect [25] used nowadays in many applications [3,17,20,27,46]. In [27], the authors consider the micro-Doppler effect, and derive explicit analytical formulas for elementary micro-motions, which are then used on real radar data problems, while other works treat randomly moving scatterers [72]. ...
... In [27], the authors consider the micro-Doppler effect, and derive explicit analytical formulas for elementary micro-motions, which are then used on real radar data problems, while other works treat randomly moving scatterers [72]. This phenomenon is used with great success from drone detection [17] or the analysis of pedestrian movement [20,27,46] to the modeling of the effect of the rotation of helicopter rotor blades on the radar signature of the aircraft [3]. In the automotive industry, micro-Doppler sensing has recently been applied with success [36,53,62,67] to the contactless detection of vital signs, in particular for the breathing of children left alone on the back seat of overheating cars. ...
A finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry.A finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry.
... For a motion with uniform velocity, the Doppler frequency shift can be computed easily [13]. The prediction of Doppler shifts for more general movements is commonly obtained through simple approximate models combined with signal processing [9,10,15,16,31,38,40]. ...
... A major advantage of high-frequency radar sensing is its sensitivity to micro movements [15,16], when the scatterer includes 1 several moving parts. This results in the so-called micro-Doppler effect [15,16], which is used with great success from drone detection [8] or the analysis of pedestrian movement [10,16,29] to the modeling of the effect of the rotation of helicopter rotor blades on the radar signature of the aircraft [2]. In the automotive industry, micro-Doppler sensing has recently been proposed [23,31,36,38] for the contactless detection of vital signs like breathing of infants left alone on the back seat of overheating cars. ...
We propose a multi-harmonic numerical method for solving wave scattering problems with moving boundaries, where the scatterer is assumed to move smoothly around an equilibrium position. We first develop an analysis to justify the method and its validity in the one-dimensional case with small-amplitude sinusoidal motions of the scatterer, before extending it to large-amplitude, arbitrary motions in one- and two-dimensional settings. We compare the numerical results of the proposed approach to standard space–time resolution schemes, which illustrates the efficiency of the new method.
... For a motion with uniform velocity, the Doppler frequency shift can be computed easily. The prediction of Doppler shifts for more general movements is commonly obtained through simple approximate models combined with signal processing [9,10,12,13,28,35,37]. ...
... A major advantage of high-frequency radar sensing is its sensitivity to micro movements [12,13], when the scatterer includes several moving parts. This results in the so-called micro-Doppler effect [12,13], which is used with great success from drone detection [8] or the analysis of pedestrian movement [10,13,26] to the modeling of the effect of the rotation of helicopter rotor blades on the radar signature of the aircraft [2]. In the automotive industry, micro-Doppler sensing has recently been proposed [20,28,33,35] for the contactless detection of vital signs like breathing of infants left alone on the back seat of overheating cars. ...
We propose a multi-harmonic numerical method for solving wave scattering problems with moving boundaries, where the scatterer is assumed to move smoothly around an equilibrium position. We first develop an analysis to justify the method and its validity in the one-dimensional case with small-amplitude sinusoidal motions of the scatterer, before extending it to large-amplitude, arbitrary motions in one-and two-dimensional settings. We compare the numerical results of the proposed approach to standard space-time resolution schemes, which illustrates the efficiency of the new method.
... Features related to respiration, heartbeat, and motion, or combinations of them, are used to differentiate between a pet present in the room and the fallen person. A range-Doppler radar can resolve many objects and therefore allows the radar to take into account more than one user in the observed environment (e.g., [54]). In this situation, both the elderly and other persons in the environment will be monitored. ...
Wi-Fi technology has strong potentials in indoor and outdoor sensing applications; it has several important features which makes it an appealing option compared to other sensing technologies. This study presents a survey on different applications of Wi-Fi-based sensing systems such as elderly people monitoring, activity classification, gesture recognition, people counting, through the wall sensing, behind the corner sensing, and many other applications. The challenges and interesting future directions are also highlighted.
... Features related to respiration, heartbeat, and motion, or combinations of them, are used to differentiate between a pet present in the room and the fallen person. A range-Doppler radar can resolve many objects and therefore allows the radar to take into account more than one user in the observed environment (e.g., [54]). In this situation, both the elderly and other persons in the environment will be monitored. ...
Wi-Fi technology has strong potentials in indoor and outdoor sensing applications, it has several important features which makes it an appealing option compared to other sensing technologies. This paper presents a survey on different applications of Wi-Fi based sensing systems such as elderly people monitoring, activity classification, gesture recognition, people counting, through the wall sensing, behind the corner sensing, and many other applications. The challenges and interesting future directions are also highlighted.
