Index Modulation for Modulation on Conjugate-Reciprocal Zeros (IM-MOCZ)

This paper investigates the application of Index Modulation (IM) to Modulation on Conjugate-Reciprocal Zeros (MOCZ) to enhance spectral efficiency (SE) in short packet communications. The proposed IM-MOCZ scheme splits an $N$-bit message into two streams: $N-K$ bits select one of $2^{N-K}$ uniquely designed codebooks, while the remaining $K$ bits are transmitted with conventional MOCZ using the selected codebook. At the receiver, Root Finding Minimum Distance (RFMD) and Direct Zero-Testing (DiZeT) detectors evaluate all candidate codebooks and compute penalty metrics, with a majority-vote rule selecting the most confident codebook and recovering the transmitted message. The proposed IM-MOCZ provides higher SE gains than conventional MOCZ, and simulations demonstrate improved bit error rate (BER) performance for larger $K$ relative to $N$.