A communication system for performing a communication via a radio relay apparatus (110, 210) located in an upper airspace, wherein a plurality of gateway stations for forming radio sections of a plurality of feeder links with the radio relay apparatus (110, 210) are disposed at a plurality of locations geographically separated from each other on the ground or on the sea, wherein the communication system comprises a base station connected to the plurality of gateway stations, and wherein a feeder link is a link between the radio relay apparatus (110, 210) and the base station via the gateway station, and a service link is a link between the radio relay apparatus (110, 210) and a terminal, characterized in that the communication system comprises a management apparatus for managing current position information of each of the radio relay apparatus (110, 210), the gateway stations and the base station, wherein, in each of a plurality of forward links for transmitting a signal to the radio relay apparatus (110, 210) via the plurality of gateway stations, each of the plurality of gateway stations is adapted to: calculate an offset according to both delay times of a transmission delay time between the base station and the gateway station and a propagation delay time between the gateway station and the radio relay apparatus (110, 210), based on the current position information of each of the radio relay apparatus (110, 210), the gateway stations and the base station which is acquired from the management apparatus; and shift a transmission timing of the signal by the calculated offset. wherein a plurality of gateway stations for forming radio sections of a plurality of feeder links with the radio relay apparatus (110, 210) are disposed at a plurality of locations geographically separated from each other on the ground or on the sea, wherein the communication system comprises a base station connected to the plurality of gateway stations, and wherein a feeder link is a link between the radio relay apparatus (110, 210) and the base station via the gateway station, and a service link is a link between the radio relay apparatus (110, 210) and a terminal, characterized in that the communication system comprises a management apparatus for managing current position information of each of the radio relay apparatus (110, 210), the gateway stations and the base station, wherein, in each of a plurality of forward links for transmitting a signal to the radio relay apparatus (110, 210) via the plurality of gateway stations, each of the plurality of gateway stations is adapted to: calculate an offset according to both delay times of a transmission delay time between the base station and the gateway station and a propagation delay time between the gateway station and the radio relay apparatus (110, 210), based on the current position information of each of the radio relay apparatus (110, 210), the gateway stations and the base station which is acquired from the management apparatus; and shift a transmission timing of the signal by the calculated offset. calculate an offset according to both delay times of a transmission delay time between the base station and the gateway station and a propagation delay time between the gateway station and the radio relay apparatus (110, 210), based on the current position information of each of the radio relay apparatus (110, 210), the gateway stations and the base station which is acquired from the management apparatus; and shift a transmission timing of the signal by the calculated offset.