Energy Efficient Symbol-Level Precoding Design for MIMO-OCDM Systems

Orthogonal chirp division multiplexing (OCDM) emerges as a promising technique for multi-carrier communication systems in next-generation networks, offering better multipath diversity exploitation compared to orthogonal frequency division multiplexing (OFDM). In this paper, we study symbol-level precoding (SLP) design for reducing power consumption in the multiple-input multiple-output orthogonal chirp division multiplexing (MIMO-OCDM) systems through the idea of non-strict phase rotation constructive interference (non-strict CI), which leads to the proposed SLP methods. Our proposed methods minimize the total power of the transmitted signal on a symbol-by-symbol basis and address this optimization challenge by transforming it into a non-negative least-squares (NNLS) problem. Furthermore, frequency domain pre-equalization (pre-FDE) is incorporated into the SLP algorithm with non-strict CI, which not only enhances transmit power efficiency but also facilitates the acquisition of more optimal perturbation vectors. Numerical evaluations of the two SLP methods demonstrate substantial power savings, which are over 80.72% and 83.87%, respectively, compared with traditional MIMO-OCDM systems while simultaneously improving BER performance.