Associate Professor Minseok Kim of Niigata University (at the time of the interview in March 2022) is working on his research theme of radio propagation measurements in outdoor mobile communication environments. He has been selected for a research and development project by the Ministry of Internal Affairs and Communications (commonly known as "National Project") and is contributing to the development of next-generation mobile communication systems.
For the reseach and field test of 6G mobile base stations and mobile terminals, the TB-1 Field Time Sync Generator has been adopted to obtain a precise one-second pulse synchronized to UTC between two remote locations.
In mobile communications research, devices that simulate mobile base stations and mobile terminals must be time synchronized for evaluation. In the laboratory environment, the signal from one rubidium oscillator can be distributed to each device, so that they are synchronized with the same reference signal.
However, for evaluation in field like outdoor environment, it is develped with a method to synchronize mobile base stations and a mobile terminals in different locations.
In field evaluations, the signal from a single rubidium oscillator cannot be distributed due to the long distance between two points. In addition, using two rubidium oscillators at each location cannot provide the accurate synchronized signals because they are independent oscillators each other.
Cesium oscillators, which are more accurate than rubidium oscillators, were considered, but they are too expensive and difficult to transport.
This led to the adoption of the TB-1 Field Time Sync Generator, which provides the same time synchronization source between two remote locations.
Time synchronization in the laboratory（Synchronized by one rubidium oscillator signal because distance between the base station and the terminal is short.）
In remote outdoor locations, if individual rubidium oscillators are used, the timing of rubidium oscillators will be different from each other.
To synchronize the signal from rubidium oscillators (FS725) that will be used in mobile base station and mobile terminals, a high-precision time signal (1 second pulse synchronized to UTC) generated by TB-1 is input to each as a reference signal. We have confirmed that the rubidium oscillators can be synchronized with high precision by this method.
Even between remote outdoor locations, rubidium oscillators are synchronized to each other with high precision through TB-1.
Synchronization between rubidium oscillators was confirmed in the laboratory. (Right photo : GNSS antenna was attached to the window）
After confirming the synchronization of rubidium in the laboratory, a field evaluation was conducted in the area around Kannai Station in Yokohama. TB-1 enabled us to measure the radio propagation characteristics in the actual use environment.