A method and apparatus for estimating channelization codes in a wireless transmit/receive unit (WTRU) using blind code detection (BCD). A WTRU receives communication bursts and detects a midamble in the received burst. A candidate code list is generated in accordance with the detected midamble. The candidate code list includes channelization codes intended for both the intended WTRU and other WTRUs. Active channelization codes among the codes in the candidate list are identified, and the identified codes are forwarded to a multi-user detector (MUD). The present invention resolves SF ambiguity in the downlink of TSM. Since the orthogonal variable spreading factor code maintains the orthogonality between codes of different SF, SFs of other WTRUs follow the SF of the intended WTRU. Moreover, since the data for other WTRUs is not used in symbol processing after MUD, the performance of MUD for the intended WTRU is preserved with the SF ambiguity of other WTRUs.