Transmit adaptive array without user-specific pilot for 3G CDMA

The transmit adaptive array (TxAA) is one of the promising closed-loop downlink diversity schemes being considered for the third generation wireless systems based on code division multiple access (CDMA). The TxAA technique originally proposed, requires a user-specific auxiliary pilot for coherent demodulation. This affects the capacity of the system due to additional power being used by this pilot. The mobile receiver requires additional hardware correlators for demodulating the pilot. Since different channels in spread spectrum systems are distinguished by their spreading sequences, it also uses up an additional Walsh code per user. This paper proposes a decision directed method for demodulation which does not require a user-specific pilot. Our simulations demonstrate that the performance of the technique is comparable to that of the method based on a user specific pilot.