Performance analysis of closed-loop pre-equalisation for multiuser multiple-input multiple-output with multicarrier code division multiple access systems

The use of multiple transmit and receive antennas is widely recognised as an effective technology to boost the capacity of wireless communication systems. Moreover, the combination of multiple-input multiple-output (MIMO) systems with multicarrier code division multiple access (MC-CDMA) offers a strong alternative to satisfy the demand for high data rates with rigorous quality-of-service (QoS) restrictions. In this study, this paper applies a closed-loop pre-equalisation methodology under a unified framework for MIMO and MC-CDMA systems that satisfies the QoS target with a single-user-based detector while minimising the power of the pre-equalisation factors. It is of particular interest to investigate the impact and limitations of combining the robustness of the feedback scheme with the degrees of freedom available in the system, given in terms of the number of subcarriers and multiple antennas. The contribution of this work includes the derivation of the distributed and centralised optimal closed-loop pre-equalisation solutions under the MIMO-MC-CDMA structure. The results and analysis illustrate important gains in the form of power savings, enabled by the spatial diversity of the MIMO scheme.