We have carried out research and development of next generation (5G) wireless communication systems in dense user environments utilizing advanced photonic technologies. Especially, we have focused on a heterogeneous wireless communication system, which includes 4G, 3G, WiFi and millimeter-wave wireless links, with broadband, low latency, low-power consumption and low-cost. In this report, photonic-based millimeter-wave wireless links of ultra-small cells (atto-cells) in a big football stadium are discussed. Advantages of an asymmetric millimeter-wave link combined with terminal localization techniques are also pointed out. Some basic experimental results on the millimeter-wave wireless links in an actual big football stadium are also reported.
The high-speed train in Japan connects megalopolises through many tunnels or underground routes. To provide seamless internet connectivity to the hundreds of passengers on the train, a new backhaul communication system is proposed in a millimeter-wave band by Radio over Fiber. We have shown that a vector-modulated signal can be generated by multiplying the radio frequency in the optical domain to avoid effects of chromatic dispersion in an optical fiber. In this paper, we show characteristics of long distance transmission by Radio over Fiber. Also, we present our concept and report on the relationship between the symbol rate and the modulation accuracy of the 96 GHz band signal generated by frequency doubling using RoF.
Some helicopters strike the power lines under the good weather conditions. Helicopter pilots sometimes have some difficulties to find such long and thin obstacles. We are developing an obstacle detection and collision warning system for civil helicopters in order to solve such problems. A color camera, an Infrared (IR) camera and a Millimeter Wave (MMW) radar are employed as sensors. This paper describes the results of different flight tests that show good enhancement of radar detection over 800m range for power lines. Additionally, we exhibit the processed fusion images that can assist the pilots in order to recognize the danger of the power lines.
Helicopters often strike against obstacles such as power lines. We are developing an obstacle detection and warning system for civil helicopters to reduce such collisions. A color camera, an Infrared (IR) camera and a Millimeter Wave (MMW) radar are employed as its sensors. This paper describes an image and data fusion of color and infrared images with the millimeter wave information. An outline of the obstacle detection and warning system is described first. Then, we propose a newly developed on-board system based on a fast AD converter. A new algorithm is also proposed to identify the nearest target using the radar signal where there are other far large-RCS obstacles. As the result, the system can achieve 30 cycles per second of IR and color image acquisition, radar data processing, distance calculation, fusing all data and displaying them. Finally, we propose a future plan for flight experiments planned in this year.
Helicopters often strike against thin obstacles such as power lines. To prevent such collisions,we are developing an obstacle detection and warning system for helicopters. An Infrared (IR)camera,a color camera and a Millimeter Wave (MMW)radar are employed as its sensor components.This paper describes the performance of the system. 94GHz FMCW radar has been developed for this system. The Vivaldi antenna has been fabricated for the radar. The range accuracy of the radar is tested by the measurements. The radiation pattern of the Vivaldi antenna is measured in the anechoic chamber. The validity of the IR camera to detect obstacles is evaluated by the flight measurements.IR
images, collected by the measurements are employed to analyze the effect of the background brightness and to develop new rendering techniques to enhance obstacles. The results show that the accuracy of the FMCW radar is within 5%. The Vivaldi antenna has good characteristics but its transition circuit deforms the total antenna pattern. It is shown that IR camera greatly increases the possibility to detect obstacles even in poor visibility. The normal distribution in the IR spectrum proves to be enough to analyze the image and to derive the obstacle information. The IR image rendered by the pseudo color method is effective to enhance obstacles.