| 摘要 |
This invention ensures that that switching to direct communication goes well. A control device transmits, to each terminal that is to perform direct communication, a request to ascertain whether or not direct communication is possible. Each terminal ascertains whether or not direct communication is possible and transmits the result of said ascertainment to the control device. On the basis of the ascertainment results sent from the terminals, the control device determines whether or not direct communication is possible, and if so, the control device transmits, to the terminals, a request to switch to direct communication. This prevents situations in which, upon switching to direct communication, communication is not actually possible. |
