A simple transmitter precoding technique for MAI/ISI rejection in the forward link of a wireless TDD/DS-CDMA system

This paper proposes a simple transmitter precoding (TP) scheme for MAI/ISI rejection in the forward link of a multiuser time division duplex (TDD) direct sequence (DS) CDMA system operating over multipath fading channels. In particular, we develop a linear precoding scheme using a cyclic prefix (CP) strategy that allows for simple matched filtering at the mobile unit. To maintain the transmitter power normalised to the number of active users, two power constrained TP schemes are introduced. Numerical results are provided to present the capacity improvement using the proposed TP scheme. These results are compared to those of a traditional (no-precoding) DS-CDMA system with a Rake receiver.