Non-Coherent Multi-User Short-Packet Communications with MOCZ: Techniques, Challenges, and Future Directions

Abstract

Non-coherent communication schemes have attracted increasing interest for multi-user short-packet transmissions due to their robustness to channel uncertainty and suitability for ultra-reliable low-latency communication (URLLC). Modulation on conjugate-reciprocal zeros (MOCZ) offers an alternative signaling paradigm by encoding information into the zeros of the transmitted signal, enabling data recovery without explicit channel estimation. This paper presents a conceptual study of multi-user MOCZ (MU-MOCZ) systems, focusing on two representative multiplexing strategies: time-division multiplexed (TDM) MU-MOCZ, where users are served sequentially, and z-domain multiplexed (ZDM) MU-MOCZ, which enables simultaneous transmissions using distinct regions of the z-plane. For both schemes, the underlying principles of zero allocation and z-domain organization are discussed, supported by illustrative examples that clarify the operational behavior of the respective multi-user frameworks. The paper highlights key design considerations and trade-offs associated with multi-user MOCZ signaling while preserving its non-coherent nature, and outlines potential research directions toward scalable MU-MOCZ frameworks for next-generation short-packet communication systems.

Keywords

• Internet of things
• MOCZ
• Non-coherent
• Short packet communication
• Polynomial zeros
• z-transform

References

1. Alevizos, P. N., Bletsas, A., & Karystinos, G. N. (2017). Noncoherent short packet detection and decoding for scatter radio sensor networking. IEEE Transactions on Communications, 65(5), 2128–2140.
2. Basar, E. (2016). Index modulation techniques for 5G wireless networks. IEEE Communications Magazine, 54(7), 168–175.
3. Chen-Hu, K., Liu, Y., & Armada, A. G. (2020). Non-coherent massive MIMO-OFDM down-link based on differential modulation. IEEE Transactions on Vehicular Technology, 69(10), 11281–11294.
4. Dikmen, O. (2024). Iterative power control for maximizing spectral efficiency in cell-free massive MIMO systems. IEEE Access, 12, 133834–133847.
5. Dikmen, O., & Kulaç, S. (2019). Determination of effective mode selection for ensuring spectrum efficiency with massive MIMO in IoT systems. Sensors, 19(3), 706.
6. Ding, Z., Lei, X., Karagiannidis, G. K., Schober, R., Yuan, J., & Bhargava, V. K. (2017). A survey on non-orthogonal multiple access for 5G networks: Research challenges and future trends. IEEE Journal on Selected Areas in Communications, 35(10), 2181–2195.
7. Dorner, S., Clausius, J., Cammerer, S., & Brink, S. T. (2023). Learning joint detection, equalization and decoding for short-packet communications. IEEE Transactions on Communications, 71(2), 837–850.
8. Durisi, G., Koch, T., & Popovski, P. (2016a). Toward massive, ultrareliable, and low-latency wireless communication with short packets. Proceedings of the IEEE, 104(9), 1711–1726.

9. Durisi, G., Koch, T., Ostman, J., Polyanskiy, Y., & Yang, W. (2016b). Short-packet communications over multiple-antenna Rayleigh-fading channels. IEEE Transactions on Communications, 64(2), 618–629.
10. Eren, T. (2024). Dynamic codebook design in non-coherent short-packet communications using modulation on conjugate-reciprocal zeros. In Proceedings of the 8th International Symposium on Innovative Approaches in Smart Technologies (ISAS) (pp. 1–6).
11. Eren, T. (2025a). Non-coherent short-packet communications: Novel z-domain user multiplexing. Digital Signal Processing, 156, Article 104777.
12. Eren, T. (2025b). Generalized dynamic codebook design for non-coherent short-packet communications: Radius control and placement of complex-conjugate reciprocal zero pairs. International Journal of Multidisciplinary Studies and Innovative Technologies (IJMSIT), 9(1), 94–101.
13. Eren, T. (2025c). Adaptive SNR-based higher-order MOCZ for short-packet communications. 9th International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT), Ankara, Türkiye, 1–6.
14. Feng, C., & Wang, H. M. (2021). Secure short-packet communications at the physical layer for 5G and beyond. IEEE Communications Standards Magazine, 5(3), 96–102.
15. Hassan, B., Baig, S., & Asif, M. (2021). Key technologies for ultra-reliable and low-latency communication in 6G. IEEE Communications Standards Magazine, 5(2), 106–113.
16. Hsu, Y. T., Yang, Y. Q., Lee, S. K., Lee, H. C., & Lin, M. C. (2020). An uplink multiple access scheme using pilot-free channel estimation. IEEE Communications Letters, 24(6), 1226–1230.
17. Jihas Khan, J., & Jacob, L. (2022). Efficient resource allocation in 5G URLLC with packet duplication based macro-diversity. Computer Communications, 191, 459–466.
18. Lee, B., Park, S., Love, D. J., Ji, H., & Shim, B. (2018). Packet structure and receiver design for low latency wireless communications with ultra-short packets. IEEE Transactions on Communications, 66(2), 796–807.
19. Li, S., Dong, Z., Chen, H., & Guo, X. (2021). Constellation design for noncoherent massive SIMO systems in URLLC applications. IEEE Transactions on Communications, 69(7), 4387–4401.
20. Liu, Y., Qin, Z., Elkashlan, M., Nallanathan, A., & McCann, J. A. (2017). Non-orthogonal multiple access in large-scale heterogeneous networks. IEEE Journal on Selected Areas in Communications, 35(12), 2667–2680.
21. Ngo, K. H., Guillaud, M., Decurninge, A., Yang, S., & Schniter, P. (2020). Multi-user detection based on expectation propagation for the non-coherent SIMO multiple access channel. IEEE Transactions on Wireless Communications, 19(9), 6145–6161.
22. Ostman, J., Durisi, G., Strom, E. G., Coskun, M. C., & Liva, G. (2019). Short packets over block-memoryless fading channels: Pilot-assisted or noncoherent transmission? IEEE Transactions on Communications, 67(2), 1521–1536.
23. Popovski, P., Chen, Z., Elias, K., de Carvalho, E., Abbas, R., Abdulsattar, C., ... & Nielsen, J. J. (2019). Wireless access in ultra-reliable low-latency communication (URLLC). IEEE Transactions on Communications, 67(8), 5783–5801.
24. Roger, S., Calabuig, D., Cabrejas, J., & Monserrat, J. F. (2014). Multi-user non-coherent detection for downlink MIMO communication. IEEE Signal Processing Letters, 21(10), 1225–1229.
25. Siddiqui, A. A., Bedeer, E., Nguyen, H. H., & Barton, R. (2024). Spectrally-efficient modulation on conjugate-reciprocal zeros (Se-MOCZ) for non-coherent short packet communications. IEEE Transactions on Wireless Communications, 23(3), 2226–2240.
26. Sun, Y., Zhang, Y., Dou, G., Lu, Y., & Song, Y. (2023). Noncoherent SIMO transmission via MOCZ for short packet-based machine-type communications in frequency-selective fading environments. IEEE Open Journal of the Communications Society, 4, 1544–1550.
27. Vaseghi, S. V. (2007). Multimedia signal processing: Theory and applications in speech, music and communications. John Wiley & Sons.
28. Walk, P., & Xiao, W. (2021). Multi-user MOCZ for mobile machine type communications. In Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC) (pp. 1–6).
29. Walk, P., Jung, P., & Hassibi, B. (2019). Mocz for blind short-packet communication: Basic principles. IEEE Transactions on Wireless Communications, 18(11), 5080–5097.
30. Walk, P., Jung, P., Hassibi, B., & Jafarkhani, H. (2020). MOCZ for blind short-packet communication: Practical aspects. IEEE Transactions on Wireless Communications, 19(10), 6675–6692.
31. Wang, H. M., Yang, Q., Ding, Z., & Poor, H. V. (2019). Secure short-packet communications for mission-critical IoT applications. IEEE Transactions on Wireless Communications, 18(5), 2565–2578.
32. Xu, C., Ishikawa, N., Rajashekar, R., Sugiura, S., Maunder, R. G., Wang, Z., Yang, L. L., & Hanzo, L. (2019). Sixty years of coherent versus non-coherent tradeoffs and the road from 5G to wireless futures. IEEE Access, 7, 178246–178299.
33. Yang, K., Dou, G., Li, C., & Ge, X. (2025). An optimized method of modulation and demodulation via BMOCZ for non-coherent short packet communications. AEU - International Journal of Electronics and Communications, 198, Article 155822.
34. Zheng, C., Zheng, F. C., Luo, J., Zhu, P., You, X., & Feng, D. (2024). Differential modulation for short packet transmission in URLLC. IEEE Transactions on Wireless Communications, 23(7), 7230–7245.