Network system for mobile radio communication

A network system for mobile radio communication includes a network constituted by a server unit and a client unit, a radio connection unit connected to a communication network, a public radio base station installed in a cell, and a mobile radio terminal which establishes a radio channel with the public radio base station while moving. The network system performs data communication between the server unit and the mobile radio terminal. Each of the server unit and the mobile radio terminal includes a buffer memory and an auxiliary storage unit which hold data. The mobile radio terminal includes an electric field strength monitoring section for monitoring slot errors or a reduction in electric field strength, a section for storing data in the buffer memory during data transmission to the server unit when the level based on slot errors or a reduction in electric field strength is equal to or higher than a threshold for line switching, a section for sending a line switching notification to the server unit, a section for sending a line switching request to the public radio base station, and a section for starting to transmit the data stored in the buffer memory upon reception of a response indicating completion of line switching from the public radio base station.