Data-Driven Code-Hopping for MC-CDMA Precoding Schemes

A novel code optimization scheme is presented for the downlink of multicarrier code division multiple access (MC-CDMA) systems employing phase shift keying (PSK) modulation. The optimization is based on dynamically re-allocating the available signature waveforms amongst the users on a symbol-by-symbol basis in order to manipulate and utilize interference amongst them. By applying the appropriate allocation criteria destructive interference between users is minimized while constructive is maximized. As a result, employing this on top of conventional schemes enhances the received signal to interference-plus-noise ratio (SINR) without additional transmitted power-per-user investment. The trade-off to the resulting performance improvement is the need for transmission of some extra side information, which by using the proposed processing is kept to a minimum. While performance benefits can be expected for various scenarios, the focus of this paper is on MC-CDMA precoding schemes. Analysis and simulations show a considerable bit error rate (BER) reduction for the case of decorrelating precoding methods.