Hidekuni Yomo

Overview of a Software Defined Downlink Inner Receiver for Category-E LTE-Advanced UE

With the soaring development cost of deep sub-micron silicon and the fast-growing diversity in wireless communications, software defined baseband becomes more and more important for handheld devices. However, most software defined receivers reported in previous literatures are still far away from fulfilling the requirement of emerging wireless standards such as the LTE-Advanced. The category-E User Equipment (UE) defined in LTE-Advanced, as the most demanding category for handheld devices, requires processing 2 concurrent data streams at around 300Mbps aggregated throughput. It is not clear whether SDR baseband processors can tackle this challenge. In our work, we explore the feasibility for software defined baseband for LTE-Advanced. With a highly customized SDR baseband processor, we have recently accomplished a software defined downlink inner receiver for Category-E LTE-Advanced UE. The implemented inner receiver includes fully fledged synchronization and data detection functionalities, including coarse CFO estimation/compensation, I/Q imbalance estimation/compensation, OFDMA demodulation, channel estimation, fine SCO/CFO estimation/compensation, MIMO channel processing, MIMO data detection and LLR generation. This paper is intended to bring an overview for the work and emphasizes key aspects that enable the feasibility of the work. In this paper, we will introduce the algorithm and processor architecture co-design flow, overall receiver functionalities, important optimizations and implementation results.

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.

Algorithm-Architecture Co-Optimization of Area-Efficient SDR Baseband for Highly Diversified Digital TV Standards

The rapidly evolving and diversifying wireless landscape demands highly flexible wireless chipsets. Due to the ultimate programmability, SDR solutions are becoming more and more attractive. However, the programmability overhead is still a concern for the silicon area cost of SDR solutions. In this work, we prove that, with algorithm and architecture co- design, SDR solutions can be very competitive even when compared to highly optimized ASICs. Specifically, we show a baseband processor design that can support ISDB-T, DVB-T and ATSC, but the area cost is still comparable to the combination of ASICs which handle the three terrestrial digital TV standards respectively.

Frequency-domain interferometric imaging and velocity vector estimation using networked ultra-wideband 80-GHz array radar systems

For tracking multiple moving targets, a multi-radar system employing ultra-wideband millimeter-wave array antennas is introduced. To separate the multiple echoes and the different Doppler velocities of the targets, the frequency-domain interferometric technique is used and is followed by an interferometric imaging process. The system consists of multiple radar modules that are well-separated, allowing measurements of the Doppler velocities from different lines of sight. Thus, in addition to constructing high-resolution images, the multi-radar system is able to estimate the velocity vector of each target, which has been demonstrated in practice through measurements.

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.

Estimation of Doppler Velocities From Sub-Nyquist Ultra-Wideband Radar Measurements

Many conventional Doppler analysis techniques for radar sensors suffer from velocity ambiguity when confronted with targets that are moving at speeds higher than the Nyquist velocity. This paper proposes a signal processing method for estimating accurately the Doppler velocity of targets from such sub-Nyquist radar data. The hypothesis tested in the paper is the possibility of circumventing the velocity ambiguity by exploiting the high range resolution of ultra-wideband radar sensors, more specifically incorporating the texture method applied to the signal envelope intensity profile. We employ a millimeter-wave radar sensor operating at 60 GHz to measure a rotating cylinder and a walking human to investigate the applicability of the proposed approach. The experimental results indicate that the proposed method can estimate the Doppler velocity accurately without aliasing from sub-Nyquist data, demonstrating that the use of the texture method is promising for resolving the ambiguity caused by sub-Nyquist sampling. The advantage of the proposed method is that the ambiguity can be resolved simply with the signal processing technique, and the approach does not require any custom hardware, such as nonuniform samplers. An important future study based on this paper is the application of the proposed approach to develop a low-cost radar system with a low sampling rate that can measure fast-moving targets.

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.

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.