Portable terminal and its communication method, and wireless network system

A communication method of a mobile terminal apparatus capable of standing by while switching among a plurality of communication systems and performing wireless communication with a base station capable of providing neighbor base station information, the method including

• a neighbor base station information acquisition step of acquiring neighbor base station information from a base station communicated with at present,
• a signal strength monitoring step of monitoring a signal strength in a communication system being used,
• a system hand-off step of performing hand-off to a communication system different from the communication system used at present stored in the neighbor base station information when the present signal strength becomes lower than a predetermined amount,
• a reselection step of releasing a session of the communication system used at present, attempting acquisition for the plurality of communication systems, and attempting position registration by a successfully acquired communication system, and
• a reselection inhibit step of selecting a first mode of inhibiting the processing of the reselection step, when the neighbor base station information received in the neighbor base station information acquisition step includes information indicating a communication system different from the communication system used at present, or selecting a second mode not inhibiting the processing of the reselection step when the neighbor base station information does not include the information indicating the communication system.

A wireless network system comprising:

• a plurality of base stations;
• and
• a mobile terminal apparatus capable of standing by while switching among a plurality of communication systems, wherein
• the base station can provide neighbor base station information to the mobile terminal apparatus when communicating with the mobile terminal apparatus,
• the mobile terminal apparatus includes
• a communication part capable of communication with the base station by selecting one of the communication systems, and
• a control part changing the communication system used by the communication part and making the communication part perform the wireless communication, and
• the control part executes
• neighbor base station information acquisition processing of acquiring the neighbor base station information from the base station communicated with at present by the communication part,
• signal strength monitor processing of monitoring a signal strength in the communication system used at the communication part,
• system hand-off processing of performing hand-off to a communication system different from the communication system used at present stored in the neighbor base station information when the present signal strength becomes lower than a predetermined amount,
• reselection processing of releasing a session of the communication system used at present by the communication part, attempting acquisition for the plurality of communication systems, and attempting position registration by a successfully acquired information system, and
• reselection inhibit processing of selecting a first mode of inhibiting the reselection processing, when the neighbor base station information received in the neighbor base station information acquisition processing includes information indicating a communication system different from the communication system being used at present at the communication part, or selecting a second mode not inhibiting the reselection processing when the neighbor base station information does not include the information indicating a communication system.