Radar-based sensing and concealed weapon detection technologies have been attracting attention as a measure to enhance security screening in public facilities and various venues. For these applications, the security check must be performed without impeding the flow of people, with minimum human effort, and in a non-contact manner. We developed technologies for a high-throughput walk-through security screening called Invisible Sensing (IVS) and implemented them in a prototype system. The IVS system consists of dual planar radar panels facing each other and carries out an inspection based on a multi-region screening approach as a person walks between the panels. Our imaging technology constructs a high-quality radar image that compensates for motion blur caused by a person's walk. Our detection technology takes multi-view projected images across the multiple regions as input to enable real-time whole-body screening. The IVS system runs its functions by pipeline processing to achieve real-time screening operation. This paper presents our IVS system along with these key technologies and demonstrates its empirical performance.

This paper proposes a method for cooperative multi-static Multiple Input Multiple Output (MIMO) radar that can estimate the number of targets. The purpose of this system is to monitor humans in an indoor environment. First, target positions within the estimation range are roughly detected by the Capon method and the mode vector corresponding to the detected positions is calculated. The mode vector is multiplied by the eigenvector to eliminate the virtual image. The spectrum of the evaluation function is calculated from the remaining positions, and the number of peaks in the spectrum is defined as the number of targets. Experiments carried out in an indoor environment confirm that the proposed method can estimate the number of targets with high accuracy.

An analytic expression of the Capon spectrum is derived for two uncorrelated incident signals. On the basis of this theoretical formulation, we discuss the effect of a factor arising from the inner product of mode vectors with respect to the incident angles, which compromises the resolution. We show numerical examples to demonstrate the effect that the inner product of mode vectors has on the shape of the Capon spectrum.

Based on the reconstruction of the augmented interference-plus-noise (IPN) covariance matrix (CM) and the estimation of the desired signal's extended steering vector (SV), we propose a novel robust widely linear (WL) beamforming algorithm. Firstly, an extension of the iterative adaptive approach (IAA) algorithm is employed to acquire the spatial spectrum. Secondly, the IAA spatial spectrum is adopted to reconstruct the augmented signal-plus-noise (SPN) CM and the augmented IPNCM. Thirdly, the extended SV of the desired signal is estimated by using the iterative robust Capon beamformer with adaptive uncertainty level (AU-IRCB). Compared with several representative robust WL beamforming algorithms, simulation results are provided to confirm that the proposed method can achieve a better performance and has a much lower complexity.

This paper presents a new approach for the Capon beamformer to provide robustness against array pointing errors. This robustness is achieved by incorporating an uncertainty constraint with diagonal loading and injected pseudo-interference. A simple performance analysis of this new beamformer is also investigated. Simulation results demonstrate that the power estimator has excellent performance.

This paper proposes a new MAC scheme for ATM based Passive Optical Network (APON) which follows the ITU-T recommendation G.983.1. MAC schemes for APON mostly adopt single-side scheduling in which only OLT (Optical Line Termination) schedules upstream access order for ONUs (Optical Network Units) that inform cell arrival information to OLT. In this paper, we propose a MAC scheme called double-side scheduling protocol (DSP) in which both OLT and ONU participate in scheduling process. Through the computer simulation we find out that the CDV (cell delay variation) performance of the real-time service can be improved remarkably using fewer overhead slots than that of the MAC schemes adopting CDV control algorithm. For the proposed MAC scheme, we present grant field format, minislot format, divided slot format, and scheduling algorithm.

This paper proposes three MAC protocols over APON to provide residential and small business customers with multimedia services. The proposed protocols support the frame structure of ITU-T recommendation G.983.1 and also provide diverse ATM service classes such as CBR, rtVBR, nrtVBR, ABR, and UBR traffics. Each service is allocated on the basis of priority. Especially, for allocating CBR and rtVBR services, each protocol uses different cell arrival timing information which is achieved with specific coding and ranging procedure. Focusing the difference of cell arrival timing information, we will investigate the performance of proposed protocols. For the proposed MAC protocols, we present grant field format, minislot format, and bandwidth allocation algorithm. Computer simulation shows the performance of the proposed protocols in terms of CDV and delay, comparing with the normal FIFO protocol.

This paper proposes a novel MAC scheme over APON based on the cell arrival timing information to provide residential and small business customers with multimedia services. The proposed scheme supports the frame format of ITU-T recommendation G.983 and also provides diverse ATM service classes such as CBR, rtVBR, nrtVBR, ABR, and UBR traffics. Each service is allocated on the basis of priority and cell arrival timing information. Especially, the CBR and rtVBR services, which are sensitive to delay and CDV, are allocated with higher priority and more exact arrival timing resolution which is achieved with specific coding and ranging procedure. For the proposed MAC scheme, we present grant field format, minislot format, and bandwidth allocation algorithm. Computer simulation results show that the performance of the proposed scheme is significantly improved in terms of CDV and delay time in case of CBR and rtVBR services, comparing with the normal FIFO scheme.