A computer system including wireless terminals which transmit information, a business application server which performs a predetermined operation based on information received from the wireless terminals, and a base transceiver station which relays communications between the wireless terminals and the business application server, are provided. The base transceiver station, to manage said plural wireless terminals in groups, stores a group definition table showing a correspondence between the wireless terminals and the groups, stores the information received from the terminals in a state history table which manages the state history of the wireless terminals, extracts difference information between the information received from the wireless terminals and the information stored in the state history table, summarizes the extracted difference information for each group, and transmits it to the business application server. The data amount received by a business application server is thus reduced.