PURPOSE: To receive pieces of answer information from all stations, to resend them when information from one station to a destination station is checked and found unreceived, and to shorten a packet error recovery time by tansmitting answer information on its addressed packet in the past cycle together with reservation information for a specific time during a reserved transmission period.

CONSTITUTION: For reserved communication between ground stations 2a and 2b and a communication satellite 1, a specific number of successive slots are gathered to constitute a cycle 5, which is assigned to a transmission cycle 16 and a reception cycle 17 at transmission and reception points 3 and 4. For reserved transmission in this cycle 5, answer information 13 showing whether its address packet in the past cycle 5 is received or not is transmitted together with the reservation information 14 for the specific time. Then, pieces of answer information 13 from all destination stations is checked and when the packet is not received, the packet is resent. Thus, an error recovery system is constituted and if an error occurs to a transmitted packet, the delay time up to the recovery is reduced to reduce information necessary for a request to resend.