FIG. 6 is a schematic diagram of a method for performing a communication service by using a plurality of modems according to an embodiment of this application. 601: A first modem MODEM 1 performs a voice service in a millimeter-wave frequency band. 602: A second modem MODEM 2 performs a data service in a high frequency band. The MODEM 1 and the MODEM 2 are in the DSDA mode. 603: When a terminal moves, the MODEM 1 of the terminal sends a MODEM 1 measurement report to a base station. It should be noted that operations 601 to 603 are similar to operations 501 to 503 shown in FIG. 5. Details are not described herein again.

604: The MODEM 1 receives, from the base station, a switching instruction for a voice service, where the switching instruction is used to instruct the MODEM 1 to switch from the millimeter-wave frequency band to a low frequency band. For example, the base station sends the switching instruction for the voice service to the MODEM 1 based on the MODEM 1 measurement report. The switching instruction is used to instruct the MODEM 1 to switch from the millimeter-wave frequency band to a low frequency band. In other words, the switching instruction is used to instruct the MODEM 1 to switch from an original cell to a target cell.

605: The MODEM 1 indicates to the arbitration apparatus that the MODEM 1 needs to be switched to a low frequency band. For example, the MODEM 1 may send an indication message to the arbitration apparatus, where the indication message may indicate that the MODEM 1 needs to be switched to a low frequency band.