Multibeam-time transmit diversity for OFDM-CDMA

This paper proposes employing a fixed multibeam transmit array and a space-time block code (STBC) in orthogonal frequency-division multiplexing code-division multiple access (OFDM-CDMA) downlink transmission. We use an STBC that has the same number of column vectors as the number of beams to orthogonalize the signals transmitted from all of the beams. Orthogonality is thus maintained among signals transmitted from a number of beams that have large sidelobes or are subject to wide angular spread. The results of simulation show that the proposed scheme provides beam diversity gain and that it can alleviate multiuser interference (MUI) by allocating several users to different symbols in an STBC matrix while assigning them all to the same spreading code