| 摘要 |
PROBLEM TO BE SOLVED: To prevent the malfunction of medical equipment, etc., and to secure the mobility of a radio terminal by using visible light or infrared light for an uplink from a radio terminal to radio base station and using radio waves for a downlink from the radio base station to the radio terminal. SOLUTION: Visible light or infrared light is used for the uplink from a radio terminal 1-1 to a radio base station 1-2, while a radio wave is used for the downlink from the station 1-2 to the terminal 1-1. That is, when the terminal 1-1 receives from a terminal 1-7 in a communication network 1-3, the network 1-3 transmits a calling signal by a downlink radio wave 1-5 from the station 1-2 which is closest to the terminal 1-1. The terminal 1-1 rings an internal ringer and notifies a user of an incoming call. The user moves to the range of a light- receiving part 1-20a which enables optical communication among light-receiving parts 1-20a, 1-20b,...1-20n of the station 1-2 and faces a light-emitting part 1-10 of the terminal 1-1 to the part 1-20a of the station 1-2 and responds to an incoming call. |
