609: The MODEM 1 performs, based on the frequency band update acknowledgment message, transmission and reception. After receiving the frequency band update acknowledgment message, the MODEM 1 initiates an access and synchronization process in the target cell corresponding to the low frequency band. After the access and synchronization are successful, the MODEM 1 performs transmission and reception with a network by using an occupied radio frequency device, namely, the service resource.

In this embodiment of this application, when the MODEM 1 and the MODEM 2 are in the DSDA mode, the arbitration apparatus stores a correspondence table of capability configuration of radio frequency devices. The correspondence table may include at least one of a table of frequency bands that do not conflict and that are corresponding to the two MODEMs or a table of frequency bands that conflict and that are corresponding to the two MODEMs. The arbitration apparatus determines, according to the configured correspondence table, whether service resources used for the services on the two SIMs conflict. If the service resources used for the services on the two SIMs do not conflict, the arbitration apparatus may maintain the DSDA mode. This ensures normal execution of the services on the two SIMs, and effectively utilizes the service resources.

3. A DSDS mode is switched to a DSDA mode for services on two SIMs.