ANALYTICAL INSIGHTS INTO THE AVERAGE BLOCK ERROR RATE OF FLUID ANTENNA SYSTEMS UNDER SHORT-PACKET CONSTRAINTS

(Received: 22-Apr.-2026, Revised: 12-Jun.-2026 , Accepted: 29-Jun.-2026)

Authors Chi-Bao Le, Tin Phu Tran,

Keywords #Fluid antenna systems #Short-packet communications #Block error rate #Ultra-reliable low-latency communications #Throughput #Reliability

Abstract Fluid antenna systems (FASs) offer immense spatial diversity within compact spaces. However, existing performance analyses predominantly rely on Shannon's capacity bounds, assuming infinite blocklength transmissions. To address the strict requirements of emerging Internet-of-Things (IoT) and ultra-reliable low- latency communications (URLLCs), this paper investigates a point-to-point FAS under short-packet communication (SPC) constraints. We rigorously derive closed-form analytical expressions for the average block error rate (BLER), effective system throughput and reliability. Furthermore, we conduct an asymptotic analysis in the high signal-to-noise ratio (SNR) regime, mathematically revealing that the system's diversity order is strictly determined by the rank of the spatial correlation matrix. Extensive Monte Carlo simulations validate the high accuracy of our proposed analytical models, demonstrating that increasing the number of fluid ports drastically reduces the BLER.

References

[1] B. Hassan, S. Baig and M. Asif, "Key Technologies for Ultra-reliable and Low-latency Communication in 6G," IEEE Communications Standards Magazine, vol. 5, no. 2, pp. 106-113, 2021.

[2] M. Adhikari and A. Hazra, "6G-enabled Ultra-reliable Low-latency Communication in Edge Networks," IEEE Communications Standards Magazine, vol. 6, no. 1, pp. 67-74, 2022.

[3] T. Q. Duong, D. Van Huynh, S. R. Khosravirad, V. Sharma, O. A. Dobre and H. Shin, "From Digital Twin to Metaverse: The Role of 6G Ultra-reliable and Low-latency Communications with Multitier Computing," IEEE Wireless Communications, vol. 30, no. 3, pp. 140-146, 2023.

[4] X. Zhao, J. Liu, Y. Wang and J. Wang, "CryptoMamba-SSM: Linear Complexity State Space Models for Cryptocurrency Volatility Prediction," IEEE Open J. of the Computer Society, vol. 7, pp. 226-243, 2026.

[5] Y. Zhu, Y. Hu, X. Yuan, M. C. Gursoy, H. V. Poor and A. Schmeink, "Joint Convexity of Error Probability in Blocklength and Transmit Power in the Finite Blocklength Regime," IEEE Transactions on Wireless Communications, vol. 22, no. 4, pp. 2409-2423, 2023.

[6] M. Yin, Y. Yang, J.-M. Wu and B. Jiao, "Opportunistic Bits in Short-packet Communications: A Finite Blocklength Perspective," IEEE Transactions on Communications, vol. 69, no. 12, pp. 80858099, 2021.

[7] C. Feng, H.-M. Wang and H. V. Poor, "Reliable and Secure Short-packet Communications," IEEE Transactions on Wireless Communications, vol. 21, no. 3, pp. 1913-1926, 2022.

[8] C. M. W. Basnayaka, D. N. K. Jayakody, T. D. P. Perera and M. Beko, "DataAge: Age of Information in SWIPT-driven Short Packet IoT Wireless Communications," IEEE Internet of Things Journal, vol. 11, no. 16, pp. 26984-26999, 2024.

[9] F. A. Pereira de Figueiredo, "An Overview of Massive MIMO for 5G and 6G," IEEE Latin America Transactions, vol. 20, no. 6, pp. 931-940, 2022.

[10] H. Q. Ngo, G. Interdonato, E. G. Larsson, G. Caire and J. G. Andrews, "Ultradense Cell-free Massive MIMO for 6G: Technical Overview and Open Questions," Proceedings of the IEEE, vol. 112, no. 7, pp. 805-831, 2024.

[11] N. T. Nguyen, V.-D. Nguyen, H. V. Nguyen, H. Q. Ngo, A. L. Swindlehurst and M. Juntti, "Performance Analysis and Power Allocation for Massive MIMO ISAC Systems," IEEE Transactions on Signal Processing, vol. 73, pp. 1691-1707, 2025.

[12] Y. Lu, J. Zhang, E. Shi, P. Zhang, D. W. Kwan Ng, D. Niyato and B. Ai, "Energy-efficient RIS-Aided Cell-free Massive MIMO Systems: Application, Opportunities and Challenges," IEEE Wireless Communications, vol. 32, no. 4, pp. 148-155, 2025.

[13] B. Di, H. Zhang, Z. Han, R. Zhang and L. Song, "Reconfigurable Holographic Surface: A New Paradigm for Ultra-massive MIMO," IEEE Transactions on Cognitive Communications and Networking, vol. 11, no. 6, pp. 3761-3783, 2025.

[14] T. C. Rapudu and O. O. Oyerinde, "Machine Learning-based Channel Estimation for Multi-RIS-assisted mmWave Massive-MIMO OFDM System in a Dynamic Environment," IEEE Transactions on Wireless Communications, vol. 24, no. 6, pp. 5297-5309, 2025.

[15] K. N. Le, "Impact of Fading Correlation and Finite-blocklength Regimes on Secrecy," IEEE Transactions on Vehicular Technology, vol. 72, no. 3, pp. 4068-4072, 2023.

[16] C. Psomas, P. J. Smith, H. A. Suraweera and I. Krikidis, "Continuous Fluid Antenna Systems: Modeling and Analysis," IEEE Communications Letters, vol. 27, no. 12, pp. 3370-3374, 2023.

[17] C. Wang, Z. Li, K.-K. Wong, R. Murch, C.-B. Chae and S. Jin, "Ai-empowered Fluid Antenna Systems: Opportunities, Challenges and Future Directions," IEEE Wireless Communications, vol. 31, no. 5, pp. 34-41, 2024.

[18] W. K. New, K.-K. Wong, C. Wang, C.-B. Chae, R. Murch, H. Jafarkhani and Y. Hao, "Fluid Antenna Systems: Redefining Reconfigurable Wireless Communications," IEEE Journal on Selected Areas in Communications, vol. 44, pp. 1013-1044, 2026.

[19] T. Gong, P. Gavriilidis, R. Ji, C. Huang, G. C. Alexandropoulos, L. Wei, Z. Zhang, M. Debbah, H. V. Poor and C. Yuen, "Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies and Future Directions," IEEE Communications Surveys & Tutorials, vol. 26, no. 1, pp. 196-257, 2024.

[20] K.-F. Tong, B. Liu and K.-K. Wong, "Designs and Challenges in Fluid Antenna System Hardware," Electronics, vol. 14, no. 7, [Online], Available: https://www.mdpi.com/2079-9292/14/7/1458, 2025.

[21] D. Bepari, S. Mondal, A. Bhowal, K. Singh, H. Shin, K.-K. Wong and D. W. K. Ng, "Fluid Antennas: Pioneering a New Era in Next-generation Wireless Communications," IEEE Communications Surveys & Tutorials, vol. 28, pp. 5596-5631, 2026.

[22] P. Ramírez-Espinosa et al., "A New Spatial Block-correlation Model for Fluid Antenna Systems," IEEE Trans. on Wireless Communications, vol. 23, no. 11, pp. 15829-15843, 2024.

[23] X. Zhu et al., "UAV-enabled Short-packet Communication via Fluid Antenna Systems," arXiv: 2602.06206, DOI: 10.48550/arXiv.2602.06206, 2026.

[24] Z. Zhang et al., "Finite-blocklength Fluid Antenna Systems," arXiv: 2509.15643, [Online], Available: https://arxiv.org/abs/2509.15643, 2026.

[25] X. Zhu et al., "Fluid Antenna Systems: A Geometric Approach to Error Probability and Fundamental Limits," IEEE Trans. on Wireless Communications, vol. 25, pp. 17195-17209, 2026.

[26] X. Zhu et al., "Fluid Antenna Systems Enabling 6G HRLLC with Port Switching Delay," arXiv: 2605.06275, [Online], Available: https://arxiv.org/abs/2605.06275, 2026.

[27] X. Zhu et al., "Fluid Antenna System-enabled UAV Communications in the Finite Blocklength Regime," IEEE Transactions on Wireless Communications, vol. 25, pp. 16714-16729, 2026.

[28] G. L. Stüber, Principles of Mobile Communication, 4th Edn, ISBN: 978-3-319-55615-4, Springer Nature, 2017.

[29] H. Zhao and D. Slock, "Analytical Insights into Outage Probability and Ergodic Capacity of Fluid Antenna Systems," IEEE Wireless Communications Letters, vol. 14, no. 5, pp. 1581-1585, 2025.

[30] M. Khammassi et al., "A New Analytical Approximation of the Fluid Antenna System Channel," IEEE Trans. on Wireless Communications, vol. 22, no. 12, pp. 8843-8858, 2023.

[31] W. K. New et al., "Fluid Antenna System: New Insights on Outage Probability and Diversity Gain," IEEE Trans. on Wireless Communications, vol. 23, no. 1, pp. 128-140, 2024.

[32] T.-H. Vu, T.-V. Nguyen, Q.-V. Pham, D. Benevides da Costa and S. Kim, "STAR-RIS-enabled Short-packet NOMA Systems," IEEE Trans. on Vehicular Technology, vol. 72, no. 10, pp. 13764-13769, 2023.

[33] T.-T. T. Nguyen, X.-X. Nguyen and N. V. T. Nguyen, "Short-packet Communications for Pinching-antenna Systems," IEEE Communications Letters, vol. 30, pp. 1270-1274, 2026.

[34] L. T. T. Huyen, B. A. Duc, X. N. Tran, B. C. Nguyen, L. T. Dung and T. M. Hoang, "BLER and BER Performance of RSMA in Multi-antenna Systems over Nakagami Fading Channels," IEEE Internet of Things Journal, Early Access, DOI: 10.1109/JIOT.2026.3686852, 2026.

[35] G. N. Tran and S. Kim, "Performance Analysis of Short Packets in NOMA VLC Systems," IEEE Access, vol. 10, pp. 6505-6517, 2022.