arXiv subjects

Takaya Yamazato

Publications and source records attributed to Takaya Yamazato.

7 recordsLinked to original sources

arXiv2026

Layered construction of Message-Wise Unequal Error Protection Codes

Conventional communication systems are mainly designed to reduce error rates and increase transmission rates, and therefore usually provide uniform protection to all transmitted messages. However, in intent-oriented applications, different messages may have different semantic meanings and importance levels, requiring different levels of reliability. This paper proposes a layered construction of message-level unequal error protection (UEP) codes for short-blocklength communication. Instead of appending an explicit protection tag to each codeword, the proposed method embeds the protection structure directly into the Hamming-distance structure of the codebook. By assigning larger minimum intra-level distances to higher-importance message groups and imposing suitable inter-level distance constraints, the proposed codebook provides differentiated error-correction capabilities while enabling reliable importance-level classification at the receiver. Theoretical conditions for correct group classification are derived, and simulations over AWGN and VLC-ISI channels show that the proposed scheme improves BER performance and group classification accuracy compared with a tag-based ECC baseline.

cs.IT↗

arXiv2026

Feasibility Study of VLC-Based Collective Perception for Vehicular Communication

This study explores the use of Visible Light Communication (VLC) in Collective Perception (CP), a technology that enables vehicles and infrastructure to share sensor information to help reduce traffic accidents. Recent advances in Vehicle-to-Everything (V2X) communication have spurred growing research interest in CP. However, in regions such as the United States and Japan, only 30 MHz of radio spectrum is allocated for V2X, which is insufficient to effectively support CP. In this paper, we propose integrating VLC into V2X systems to enhance CP, complementing the existing 5.9 GHz band for V2X communications. VLC can coexist with wireless systems that use radio waves, providing an additional optical channel for data exchange. To the best of the authors' knowledge, this is the first study to investigate VLC for CP. We evaluate the feasibility of VLC-based CP through three experiments. First, we measured the application-level delay of a VLC-based CP system in a stationary indoor environment. Next, we evaluated its communication range in a stationary outdoor setting. Finally, to assess robustness under realistic conditions, we conducted driving experiments at vehicle speeds up to 90 km/h. The results demonstrate that VLC-based CP is feasible and could serve as a promising solution to spectrum scarcity in the 5.9 GHz band for future V2X communications.

eess.SP↗

arXiv2026

Channel Modeling and LED Spot Detection for Dense Image-Sensor Visible Light Communication

High-density LED arrays enable high-speed transmission in image-sensor-based visible-light communication (VLC) systems. However, when optical spots become blurred and spatially overlapped due to focal shift, resolution limitations, or interference, severe inter-symbol interference (ISI) occurs, significantly degrading decoding performance. Furthermore, radial distortion introduces geometric deformation of the LED grid, while vignetting leads to incomplete and asymmetric spot shapes at the periphery, both of which further hinder reliable signal detection. Existing methods mitigate ISI by reducing LED transmission signaling density. This paper proposes a robust decoding framework that maintains full LED signaling density. We introduce a pilot-aided geometric recognition method that uses a PSF-constrained Hough transform and circle-center alignment refinement. \textbf{In addition, radial distortion correction and vignetting-aware compensation are incorporated to restore geometric consistency and suppress edge-related detection errors.} By leveraging prior structural knowledge from pilot frames, the system effectively separates overlapping LED signals under severe optical distortion. Experimental results on a real-world VLC testbed confirm that the proposed method achieves superior decoding accuracy and throughput compared to conventional Hough-based and low-density baseline methods. The results highlight its potential for high-efficiency VLC applications in interference-prone environments.

cs.IT↗

arXiv2026

Real-world Latency Analysis of Vehicular Visible Light Communication with Multiple LED Transmitters and an Event-Based Camera

Event cameras offer high temporal resolution, low latency, and wide dynamic range, making them promising receivers for visible light communication (VLC) in vehicle-to-everything (V2X) applications. This work presents an event-camera-based VLC system addressing three key challenges: bandwidth saturation, multi-transmitter reception, and latency characterization. We adopt a positive-event-only mode and design a protocol that suppresses event generation while maintaining communication distance and a wide field of view. We also propose a method to identify multiple transmitters and demonstrate simultaneous reception from up to three LEDs. Finally, we evaluate end-to-end latency in real vehicular scenarios and show that the system meets cooperative perception requirements. These results demonstrate that event-camera-based VLC is a feasible complement to existing V2X technologies (e.g., RF).

cs.RO↗

arXiv2025

Performance Evaluation of an Integrated System for Visible Light Communication and Positioning Using an Event Camera

Event cameras, featuring high temporal resolution and high dynamic range, offer visual sensing capabilities comparable to conventional image sensors while capturing fast-moving objects and handling scenes with extreme lighting contrasts such as tunnel exits. Leveraging these properties, this study proposes a novel self-localization system that integrates visible light communication (VLC) and visible light positioning (VLP) within a single event camera. The system enables a vehicle to estimate its position even in GPS-denied environments, such as tunnels, by using VLC to obtain coordinate information from LED transmitters and VLP to estimate the distance to each transmitter. Multiple LEDs are installed on the transmitter side, each assigned a unique pilot sequence based on Walsh-Hadamard codes. The event camera identifies individual LEDs within its field of view by correlating the received signal with these codes, allowing clear separation and recognition of each light source. This mechanism enables simultaneous high-capacity MISO (multi-input single-output) communication through VLC and precise distance estimation via phase-only correlation (POC) between multiple LED pairs. To the best of our knowledge, this is the first vehicle-mounted system to achieve simultaneous VLC and VLP functionalities using a single event camera. Field experiments were conducted by mounting the system on a vehicle traveling at 30 km/h (8.3 m/s). The results demonstrated robust real-world performance, with a root mean square error (RMSE) of distance estimation within 0.75 m for ranges up to 100 m and a bit error rate (BER) below 0.01 across the same range.

cs.RO↗

arXiv2025

Distance Estimation in Outdoor Driving Environments Using Phase-only Correlation Method with Event Cameras

With the growing adoption of autonomous driving, the advancement of sensor technology is crucial for ensuring safety and reliable operation. Sensor fusion techniques that combine multiple sensors such as LiDAR, radar, and cameras have proven effective, but the integration of multiple devices increases both hardware complexity and cost. Therefore, developing a single sensor capable of performing multiple roles is highly desirable for cost-efficient and scalable autonomous driving systems. Event cameras have emerged as a promising solution due to their unique characteristics, including high dynamic range, low latency, and high temporal resolution. These features enable them to perform well in challenging lighting conditions, such as low-light or backlit environments. Moreover, their ability to detect fine-grained motion events makes them suitable for applications like pedestrian detection and vehicle-to-infrastructure communication via visible light. In this study, we present a method for distance estimation using a monocular event camera and a roadside LED bar. By applying a phase-only correlation technique to the event data, we achieve sub-pixel precision in detecting the spatial shift between two light sources. This enables accurate triangulation-based distance estimation without requiring stereo vision. Field experiments conducted in outdoor driving scenarios demonstrated that the proposed approach achieves over 90% success rate with less than 0.5-meter error for distances ranging from 20 to 60 meters. Future work includes extending this method to full position estimation by leveraging infrastructure such as smart poles equipped with LEDs, enabling event-camera-based vehicles to determine their own position in real time. This advancement could significantly enhance navigation accuracy, route optimization, and integration into intelligent transportation systems.

eess.IV↗

arXiv2025

Evaluation of Mobile Environment for Vehicular Visible Light Communication Using Multiple LEDs and Event Cameras

In the fields of Advanced Driver Assistance Systems (ADAS) and Autonomous Driving (AD), sensors that serve as the ``eyes'' for sensing the vehicle's surrounding environment are essential. Traditionally, image sensors and LiDAR have played this role. However, a new type of vision sensor, event cameras, has recently attracted attention. Event cameras respond to changes in the surrounding environment (e.g., motion), exhibit strong robustness against motion blur, and perform well in high dynamic range environments, which are desirable in robotics applications. Furthermore, the asynchronous and low-latency principles of data acquisition make event cameras suitable for optical communication. By adding communication functionality to event cameras, it becomes possible to utilize I2V communication to immediately share information about forward collisions, sudden braking, and road conditions, thereby contributing to hazard avoidance. Additionally, receiving information such as signal timing and traffic volume enables speed adjustment and optimal route selection, facilitating more efficient driving. In this study, we construct a vehicle visible light communication system where event cameras are receivers, and multiple LEDs are transmitters. In driving scenes, the system tracks the transmitter positions and separates densely packed LED light sources using pilot sequences based on Walsh-Hadamard codes. As a result, outdoor vehicle experiments demonstrate error-free communication under conditions where the transmitter-receiver distance was within 40 meters and the vehicle's driving speed was 30 km/h (8.3 m/s).

cs.RO↗