Communication terminal device, communication system, and communication control method

A communication system comprising a first communication system specializing in packet communication, a second communication system supporting voice communication, and a communication terminal device performing data communication via said first communication system or said second communication system, wherein:

• said communication terminal device requests said first communication system to execute a suspension procedure before performing voice communication via said second communication system,
• said communication terminal device requests said first communication system to execute a resumption procedure after said voice communication is finished,
• said first communication system holds access control information indicating a total or a partial restriction of an access between said communication terminal device and said second communication system sent from said second communication system,
• said first communication system sends, in response to a request for sending said access control information, said access control information to said communication terminal device that has performed said request,
• said first communication system executes a procedure to suspend said communication terminal device, if said received access control information indicates a restriction of less than a predetermined level on the access between said communication terminal device and said second communication system, and
• said first communication system does not execute a procedure to suspend said communication terminal device if said received access control information indicates a total restriction or a restriction of equal to or greater than the predetermined level on the access between said communication terminal device and said second communication system.

A communication control method comprising:

• a first communication step in which data communication in a first communication mode specializing in packet communication via a first communication system is performed;
• a second communication step in which data communication in a second communication mode supporting voice communication via a second communication system is performed;
• an instruction input step in which input of a voice communication start instruction is received;
• and
• a control step, wherein:
• said control step comprises the following steps of:
• performing data communication via said first communication system until said input of a voice communication start instruction is received in said instruction input step;
• when said input of the voice communication start instruction is received in said instruction input step,
• requesting said second communication system to send-access control information indicating a total or a partial restriction of an access between a communication terminal device and said second communication system, receiving said access control information sent from said second communication system in response to said request, and
• determining not to perform data communication via said second communication system if said received access control information indicates a total restriction or a restriction of equal to or greater than a predetermined level on the access between said communication terminal device and said second communication system, and determining to perform the data communication via said second communication system if said received access control information indicates a restriction of less than the predetermined level, and
• preventing said second communication unit from performing data communication if it is determined not to perform data communication via said second communication system in the control step, and controlling the first communication step to request said first communication system to execute a suspension procedure and controlling said second communication step to perform voice communication via said second communication system if it is determined to perform data communication via said second communication system in the control step.