PACKET ARRIVAL CONFIRMING METHOD, CENTER STATION AND USER STATION

摘要

PROBLEM TO BE SOLVED: To provide a packet arrival confirming method which can reduce the frequency capacity of a communication line and the number of time slots for securing a confirmation signal when the number of user stations being the objects of the distribution of data is large in a multicast communication system of 'one-to-many' which uses a radio line, and to provide a center station and a user station. SOLUTION: Backward lines common to plural user stations for making a response to a center a station by plural user stations are allocated to the number M of packet signals which the center station continuously transmits. The user stations try the reception of M-pieces of packet signal transmitted from the center station. When the packet signal which cannot correctly be received exists, the backward line which is made to correspond to the packet signal is use and the response signal which does not arrive yet is transmitted to the center station. The center station transmits M- pieces of packet signal and monitors the presence or absence of the response signal by M-piece of backward lines. When the center station detects the response signal on the backward lines, it recognizes the existence of the user station which cannot correctly receive the corresponding packet signal.