Developments in microwave and millimeter-wave systems have enabled remote sensing techniques traditionally used in long-range applications to be employed in the relatively closer range applications of detection and classification of human presence and measurement of human properties. This paper reviews the techniques used in microwave remote sensing of humans and discusses prominent examples of experimental systems from the literature. Radar techniques have been developed for measuring the time-varying scattering returns from the various parts of the human body during motion, which are used for human presence detection and the classification of human activities. The effects of breathing and heartbeat are also detectable using Doppler radar techniques, which is applicable to medical applications as well as search-and-rescue and security. Recent developments in distributed radars have enabled the direct measurement of the angular velocity of moving people, and passive systems have also been developed which provide a complementary detection mode that can aid in detection and classification of humans.

A Review of Microwave Wireless Techniques for Human Presence Detection and Classification

In this letter, a localization algorithm, which combines Hough transform and Doppler processing, is proposed for Doppler radar human sensing applications. The Hough transform is first applied to extract the interested target components and real-time estimate their instantaneous frequencies (IFs). Then, based on the IF estimation result, the target movement trajectories are synthesized by Doppler processing. To improve the detection accuracy and robustness, a generalized linear model is proposed for Hough transform, which can achieve highly dimensional frequency fitting to compensate the nonlinear error, meanwhile maintaining a low level of computational complexity for real-time processing. Experimental results are presented to illustrate the performance of the proposed algorithm.

Human Target Localization Using Hough Transform and Doppler Processing

MIMO Doppler Radar Using Khatri-Rao Product Virtual Array for Indoor Human Detection

The 5-th generation mobile communication system (5G), which is the next generation communication system, is being developed. In 5G, it is assumed that multiple cells with different frequency bands will be used. The attenuation of signal power due to propagation loss in free space and the reflection of radio waves from buildings, etc., differs depending on the frequency. In this paper, a radio propagation measurement is performed for micro and milli-meter waves (5 and 19GHz bands), which will be used in 5G. The outdoor propagation characteristics of each frequency band based on the measured channel state information are evaluated in terms of the signal to noise ratio and channel capacity.

Comparison of SNR and channel capacity with micro and milli-meter wave bands based on outdoor propagation measurement

MIMO technique can improve system performance not only communication system but also radar system. In this paper, we propose a quasi-MIMO Doppler radar for indoor human detection. In the indoor measurements, multipath reflections by wall, floor, and furniture, often make human detection difficult. Doppler filtering is introduced to remove these undesired response and extract radar echoes by human in motion before target detection. Also virtual array technique based on the Khatri-Rao matrix product is introduced in the MIMO radar detection. Experimental results are reported to shown performance improvement especially in angular resolution.

Indoor human detection by using quasi-MIMO Doppler radar

MIMO radar and Khatri-Rao (KR) product virtual array are the methods for increasing angular resolution of the array radar. The KR product is not suited to radar because KR product needs data property of uncorrelated wave incidence. However, when we extract responses of moving targets having different Doppler frequencies by Doppler filtering, the KR product array works almost properly because their correlation become low. In this report, we show the availability of the MIMO radar with the KR product virtual array for indoor location estimation by experiment.

Yosuke Wakamatsu

Papers

MIMO Doppler Radar Using Khatri-Rao Product Virtual Array for Indoor Human Detection

Indoor human detection by using quasi-MIMO Doppler radar

MIMO Doppler radar using Khatri-Rao product virtual array for human location estimation