Phase alignment transmit diversity for TDD systems

Phase alignment transmit diversity (PATD) is a novel technique for adjusting the phases of transmit adaptive antennas arrays based on joint optimisation of multiple users signals. This technique is equivalent to transmit adaptive antennas (TxAA) for the single user case. However, as the number of users jointly optimised increases, the gains remain significant but sub-optimal compared to TxAA gains. PATD uses a single parameter for all the users at the same time, minimising implementation complexity and costs. In the UMTS TDD mode case PATD is completely transparent to the MS receiver whereas TxAA requires modifications in the receiver structure (i.e. requires as many channel estimates as users sharing the same time slot). PATD can also be applied to broadcast PMR systems