A communication device for performing a codec rate adaptation comprises a storage device for storing instructions and a processing circuit coupled to the storage device. The processing circuit is configured to execute the instructions stored in the storage device. The instructions comprise receiving a first bit rate recommendation from a first cell; selecting a first codec rate according to the first bit rate recommendation and encoding a first plurality of packets according to the first codec rate; receiving a handover command; performing a handover to the second cell in response to the handover command; transmitting a bit rate query to the second cell after the handover; receiving a second bit rate recommendation from the second cell; and selecting a second codec rate according to the second bit rate recommendation and encoding a second plurality of packets according to the second codec rate.