Polar Coded OFDM with Code-Frequency Index Modulation

In this paper, we introduce a polar coded orthogonal frequency division multiplexing with code-frequency index modulation (PC-CFIM) scheme, designed to enhance spectral efficiency (SE) while improving error performance. At the transmitter, PC-CFIM divides the information bits into two subsets. One subset is utilized for selecting the spreading code index, and the other is utilized for polar coded OFDM with index modulation (PC-OFDM-IM). In the proposed PC-CFIM framework, the polar-coded sequence is spread using the indices from code domain index modulation. At the receiver, the system employs code index selection coupled with polar decoding to ensure accurate retrieval of information bits. The integration of polar code with hybrid index modulation significantly improves interference resilience, thereby reducing bit error rates (BER). Moreover, the transmission of additional bits via the spreading code index further enhances the system’s SE. Simulation results show that compared to the conventional PC-OFDM-IM, the proposed PC-CFIM significantly improves the BER performance with enhanced SE.