Methods and systems are disclosed for communicating in a wireless communications system utilizing a plurality of frequency bands for downlink (DL) transmission and a plurality of frequency bands for uplink (UL) transmission. In an embodiment, a mobile device receives a DL signal via a DL frequency band. The DL signal contains DL-UL frequency band association information which is used to determine a UL frequency band for UL transmission. The mobile device configures its radio-frequency (RF) circuitry to operate in the UL frequency band for UL transmission.