在第五代行動通訊中，確保傳輸可靠性以及達到超低延遲的要求是非常重要的，本篇論文針對有限區塊長度機制下解碼轉發中繼的無線通訊系統進行研究。來源端根據卜瓦松程序生成狀態更新封包，依據硬體多工能力，封包可借助全雙工或半雙工模式下的中繼傳送至目的端，但透過中繼傳輸可能產生額外延遲，導致狀態更新封包不能及時的被接收，這會使物聯網裝置收到非即時資訊的封包影響狀態更新的效率。我們提出適用於全雙工及半雙工中繼系統的封包更新策略，並引入信息年齡作為衡量狀態更新封包的新鮮度指標，並且我們各別針對所提出的四種更新策略分析其平均信息年齡的近似理論值，最後透過模擬结果驗證近似理論值的正確性，以及顯示系统性能受關鍵参数的影響，並且結果顯示所提出的更新策略可優於無中繼幫忙協助的傳輸系統。

In the fifth generation (5G) communication, it is crucial to ensure transmission reliability and achieve ultra-low latency requirement. In this thesis, we consider a decode-and-forward (DF) relaying wireless communication system under a finite block length regime. The source generates status update packets according to a Poisson process. To improve the reliability of communication, the packets will be transmitted to the destination through the help of full-duplex (FD) or half-duplex (HD) relay. However, the status updates may not be received in time when transmitted through relay assistance, and it will cause the Internet of Things (IoT) device to receive status updates with outdated information. We propose the status update policies for FD and HD relaying systems, and the age of information (AoI) is exploited as a metric to measure the freshness of status updates. The average AoI for the four proposed update policies are analyzed theoretically. Simulation results are presented to verify the analysis accuracy and demonstrate the system performance subject to numerous key parameters. Our results reveal that the proposed update policies outperform the transmission system without the help of relays.

[1] A. Al-Fuqaha, M. Guizani, M. Mohammadi, M. Aledhari, and M. Ayyash, “Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications,”IEEE Communications Surveys & Tutorials, vol. 17, no. 4, pp. 2347–2376, 2015.

[2] X. Liu and N. Ansari, “Green Relay Assisted D2D Communications With Dual Batteries in Heterogeneous Cellular Networks for IoT,” IEEE Internet of Things Journal, vol. 4, no. 5, pp. 1707–1715, 2017.

[3] H. Chen, R. Abbas, P. Cheng, M. Shirvanimoghaddam, W. Hardjawana, W. Bao, Y. Li, and B. Vucetic, “Ultra-Reliable Low Latency Cellular Networks: Use Cases, Challenges and Approaches,” IEEE Communications Magazine, vol. 56, no. 12, pp. 119–125, 2018.

[4] M. Dai, P. Wang, S. Zhang, B. Chen, H. Wang, X. Lin, and C. Sun, “Survey on Cooperative Strategies for Wireless Relay Channels,” Transactions on Emerging Telecommunications Technologies, vol. 25, no. 9, pp. 926–942, 2014.

[5] J. N. Laneman, D. N. Tse, and G. W. Wornell, “Cooperative Diversity in Wireless Networks: Efficient Protocols and Outage Behavior,” IEEE Transactions on Information theory, vol. 50, no. 12, pp. 3062–3080, 2004.

[6] S. Ikki and M. H. Ahmed, “Performance Analysis of Cooperative Diversity Wireless Networks over Nakagami-m Fading channel,” IEEE Communications letters, vol. 11, no. 4, pp. 334–336, 2007.

[7] I. Maric and R. D. Yates, “Bandwidth and Power Allocation for Cooperative Strategies in Gaussian Relay Networks,” IEEE Transactions on Information Theory, vol. 56, no. 4, pp. 1880–1889, 2010.

[8] Y. Gu, H. Chen, Y. Li, and B. Vucetic, “Ultra-Reliable Short-Packet Communications: Half-Duplex or Full-Duplex Relaying?” IEEE Wireless Communications Letters, vol. 7, no. 3, pp. 348–351, 2018.

[9] S. Kaul, R. Yates, and M. Gruteser, “Real-Time Status: How Often Should One Update?” in Proc. IEEE INFOCOM, 2012, pp. 2731–2735.

[10] S. Farazi, A. G. Klein, and D. R. Brown, “Age of Information in Energy Harvesting Status Update Systems: When to Preempt in Service?” in Proc. IEEE International Symposium on Information Theory (ISIT), 2018, pp. 2436–2440.

[11] V. Kavitha, E. Altman, and I. Saha, “Controlling Packet Drops to Improve Freshness of information,” CoRR, vol. abs/1807.09325, 2018. [Online]. Available: http://arxiv.org/abs/1807.09325

[12] R. Wang, Y. Gu, H. Chen, Y. Li, and B. Vucetic, “On the Age of Information of Short-Packet Communications with Packet Management,” in Proc. IEEE Global Communications Conference (GLOBECOM), 2019, pp. 1–6.

[13] T. Riihonen, S. Werner, and R. Wichman, “Hybrid Full-Duplex/Half-Duplex Relaying with Transmit Power Adaptation,” IEEE Transactions on Wireless Communications, vol. 10, no. 9, pp. 3074–3085, 2011.

[14] Y. Polyanskiy, H. V. Poor, and S. Verdu, “Channel Coding Rate in the Finite Blocklength Regime,” IEEE Transactions on Information Theory, vol. 56, no. 5, pp. 2307–2359, 2010.

[15] E. Najm, R. Yates, and E. Soljanin, “Status Updates Through M/G/1/1 Queues with HARQ,” in Proc. IEEE International Symposium on Information Theory (ISIT), 2017, pp. 131–135.

[16] D. Zheng, Y. Yang, L. Wei, and B. Jiao, “Decode-and-Forward Short-Packet Relaying in the Internet of Things: Timely Status Updates,” IEEE Transactions on Wireless Communications, vol. 20, no. 12, pp. 8423–8437, 2021.

[17] B. Makki, T. Svensson, and M. Zorzi, “Finite Block-length Analysis of the Incremental Redundancy HARQ,” IEEE Wireless Communications Letters, vol. 3, no. 5, pp. 529–532, 2014.

[18] K. Chen and L. Huang, “Age-of-Information in the Presence of Error,” in Proc. IEEE International Symposium on Information Theory (ISIT), 2016, pp. 2579–2583.

[19] Y. Gu, H. Chen, Y. Zhou, Y. Li, and B. Vucetic, “Timely Status Update in Internet of Things Monitoring Systems: An Age-Energy Tradeoff,” IEEE Internet of Things Journal, vol. 6, no. 3, pp. 5324–5335, 2019.