Takaaki Kishigami

Advanced millimeter-wave radar system using coded pulse compression and adaptive array for pedestrian detection

This paper reports a radar system design using millimeter-wave for vehicular and pedestrian safety around intersections. The proposed system design and associated key algorithms are embedded into a prototype and verified in an anechoic chamber and a trial intersection. The system covers 30 cm range resolution, 5-degree angle resolution, 95% detection rate and 10% false alarm rate. The results therefore prove the system feasibility for future automotive safety application.

Advanced code sequences design for pedestrian detection in millimeter-wave pulse-compression radar system

The paper proposes code sequences with an optimized criterion for precisely detecting pedestrians in the presence of vehicles in millimeter-wave pulse-compression radar system. The criterion named FR (Floor-Ratio) focuses on the maximum of sidelobes. The code sequences based on FR attain higher maximum sidelobe suppression compared to the ones based on conventional criterion. Computer simulation and experimental measurement have been done for verification. Consequently, our work proves the effectiveness of the proposed code sequences with the criterion for next generation millimeter-wave radar systems.

Millimeter-wave radar combining Tx beamforming and Rx array processing for precise pedestrians detection

The advanced radar detection method which combines Tx beamforming and Rx array processing with highresolution direction of arrival (DOA) estimation is proposed. The proposed method associates DOA estimation direction with Tx beamforming direction (TxD-DOA) for a high accuracy detection for multiple targets in millimeter-wave radar system. Computer simulation and experiment evaluation verify the improvement effects of the TxD-DOA method. We have confirmed that the suppression of multiple radar reflection waves by the transmission beam scanning brings the better DOA estimation accuracy and higher angular resolution of the TxD-DOA for multiple human targets.

Advanced wide field of view millimeter-wave radar using orthogonal complementary codes

This paper reports a radar system design using 79GHz millimeter-wave for vehicular and pedestrian safety around intersections. The proposed system design and associated key algorithms are embedded into a prototype and verified in an anechoic chamber and a field experiment. The system covers the distance of 40m and the azimuth angle of 120° range with high range and angular resolution (20cm, 5-degree), and can detect pedestrians within short budget of 100ms by using orthogonal complementary codes which are transmitted by Tx dual beamscanning to suppress the interference between the two divided area. The results therefore prove the system feasibility for future automotive safety application.

Millimeter-wave MIMO radar with unequally spaced L/T-shaped arrays

This paper proposes L- and/or T-shaped Tx and Rx arrays for MIMO radar, which enable to enhance azimuth and elevation angular resolution to the maximum under the limitation on the number of the array elements. The proposed L/T-shaped Tx and Rx arrays include unequally spacing between array elements to be minimum redundancy array on the virtual Rx array, and two-dimensional (2D) interpolation on the Rx virtual array is proposed in order to suppress sidelobes in 2D angular profiles. Computer simulation and experimental measurements have been done for verification. Consequently, our work proves the effectiveness of the proposed MIMO radar array to enhance angular resolution in MIMO radar systems.

Orthogonal complementary codes with Doppler-offset for MIMO radar waveforms

The paper proposes the MIMO waveforms consisted of Doppler-offset orthogonal complementary codes (DO-OCC) for realizing high update rate MIMO system. The DO-OCC waveforms have low cross-correlation among multiplexed waves and low autocorrelation peak side-lobe level (PSL) even in a channel fluctuation condition. Computer simulation and experimental measurements have been done for verification. Consequently, our work proves the effectiveness of the proposed MIMO waveforms for high update rate MIMO radars systems.

79GHz-band radar cross section measurement for pedestrian detection

This paper presents radar cross section (RCS) measurement for pedestrian detection in 79GHz-band radar system. For a human standing at 6.2 meters, the RCS distributions median value is -11.1 dBsm and the 90 % of RCS fluctuation is between -20.7 dBsm and -4.8 dBsm. Other measurement results (human body poses beside front) are shown. And we calculated the coefficient values of the Weibull distribution fitting to the human body RCS distribution.

An iterative interference canceller with log-likelihood ratio compensation for LDPC coded MIMO systems

This paper proposes a new iterative interference canceller (IIC) with log-likelihood ratio (LLR) compensation for low-density parity-check (LDPC) coded multi-input multi-output (MIMO) systems in order to mitigate the influence of error propagation. The proposed IIC compensates the LLR, which is obtained from the LDPC decoding, by adding the LLR obtained at previous turns of iteration. Computer simulation results show that the proposed the IIC with LLR compensation can obtain 3dB of Eb/N0 gain for achieving WER=10 -3 compared with the IIC without LLR compensation and requires less than 1dB of additional Eb/N0 compared with the maximum a posteriori (MAP) demodulator.

On the performance of practical VIP-MIMO-OFDM systems for future wireless LAN

This paper examines the practical feasibility of the proposed Varying Interleave Patterns (VIP)-MIMO scheme in accordance with OFDM-based IEEE802.11a standards and IEEE802.11n channel models for future wireless LAN. For the sake of acquiring more diversity gain in the VIP-MIMO scheme using spatial multiplexing, both interleave size and the number of iterative decoding are of special importance although an iterative decoder gives rise to delays. IEEE802.11a standards require sending an ACK frame within a specific period, and IEEE802.11 future standards including IEEE802.11n are also demanding the period as a backward compatibility. The simulation results of a VIP-MIMO-OFDM system with an iterative decoder considering the above points indicate significant improvements in S/N over a legacy system. We therefore clarify the promising faculty of the VIP-MIMO-OFDM system.

A low-complexity beamforming algorithm for 3G macro-cellular system to reduce interference from high data rate users

A beamforming algorithm for a macro cell base station (BS) is proposed. The method has the following three features. Firstly, each direction of arrival (DOA) of waves from mobile terminals to the BS is calculated by the modified Fourier beamformer using a real number correlation vector (RV-Fourier), which greatly reduces complexity. Secondly each DOA is estimated accurately even if there are high power interference waves, applying the technique to subtract the other users correlation vector. Lastly, nulls in interference directions are formed using the modified directionally constrained minimization of power (DCMP) method, which does not need the derivation of the inverse correlation matrix. In comparison with the conventional recursive least-squares (RLS) method, the proposed method requires a much smaller computational load (about 10-20%). Simulation results show that the tracking performance of the proposed method excels RLS when the terminals are moving fast.