A method and wireless communication system for providing channel assignment information used to support an uplink (UL) channel and a downlink (DL) channel. The system includes at least one Node-B and at least one wireless transmit/receive unit (WTRU). The WTRU communicates with the Node-B via a common control channel, the UL channel and the DL channel. The WTRU receives a message from the Node-B via the common control channel. The message includes an indication of whether the message is intended for assigning radio resources to the UL channel or the DL channel. The WTRU determines whether the message is intended for the WTRU and, if so, the WTRU determines whether the message is for assigning radio resources to the UL channel or the DL channel. The WTRU takes an appropriate action based on whether the message is for assigning radio resources to the UL channel or the DL channel.