Systems, methods, and instrumentalities are disclosed to provide antenna transmit diversity. A wireless transmit/receiver unit (WTRU) may comprise multiple antennas. A channel condition for each of the antennas may be determined. A probing phase may be used in order to determine the channel conditions. During a period of the probing phase, a probing signal from each antenna may be transmitted during a respective time interval. The WTRU transmit power may or may not be held constant. A Node B may receive each probing signal and determine channel quality information. The Node B may adjust the determined channel quality information if there is a power offset between the signals. The Node B may send the channel quality information to the WTRU. The WTRU may switch an antenna to use for uplink transmission based on the received channel quality information.
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