Statistical Precoder Design for Space-Time-Frequency Block Codes in Multiuser MISO-MC-CDMA Systems

In this paper, we present a space-time-frequency joint block coding (STFBC) scheme to exploit the essential space-time-frequency degrees of freedom of multiuser multiple-input-single-output multicarrier code-division multiple-access systems. Specifically, we use a series of orthogonal random codes to spread the space-time code over several subcarriers to obtain multidiversity gains, whereas multiuser parallel transmission is applied over the same subcarriers by making use of multiple orthogonal code channels. Furthermore, to improve the system performance, we put forward to linear precoding the predetermined orthogonal STFBC, including transmitting directions selection and power allocation over these directions. We propose a precoder design method by making use of channel statistical information in time domain based on the Kronecker correlation model for the channels; thus, feedback amount can be largely decreased in multicarrier systems. In addition, we give the performance analysis from the perspectives of diversity order and coding gain, respectively. Moreover, through asymptotic analysis, we derive some simple precoder design methods, while guaranteeing a good performance. Finally, numerical results validate our theoretical claims.