上行正交分頻多重接取的隨機存取 (UORA) 是由IEEE 802.11ax定義的競爭式通道存取機制，並被採用於下一代Wi-Fi標準IEEE 802.11be。UORA遵循多通道時槽阿羅哈協議，多個使用者 (Station) 能夠同時傳輸其緩衝區狀態回報 (BSR)，並使存取點 (AP) 根據station的BSR促進上行封包傳輸。在上行傳輸中，AP可以預留部分資源單位 (RU) 作為專用RU，提供已知BSR的特定STA傳輸其封包；並將剩餘的RU作為隨機接入的資源單位 (RA-RU)，提供其他STA進行UORA。本論文提出了一種頻域式封包預留機制，STA利用UORA傳輸其BSR，並使用BSR為封包傳輸預留RU。我們進一步提出數學分析模型來研究在突發抵達情況下具有封包預留機制的UORA瞬態效能，並探討動態變化的RA-RU數量對UORA訪問成功機率和平均訪問延遲造成的影響。

Uplink OFDMA random access (UORA) is a contention-based channel access method defined by IEEE 802.11ax and also adopted in IEEE 802.11be for the next generation WiFi standard. The UORA adopts a multi-channel slotted ALOHA protocol, which allows multiple stations (STAs) to simultaneously transmit their buffer status reports (BSRs) and enables the access point (AP) to facilitate the uplink data transmissions from the STAs based on their BSRs. In the uplink, the AP can reserve the part of the RUs as dedicated RUs for specific STAs with known BSRs to transmit their data packets and allocate the remaining RUs as random access RUs (RA-RU) for the other STAs to transmit their BSRs using UORA. In this paper, we proposed a frequency domain packet reservation mechanism that allows STAs to transmit their BSRs using UORA and uses the BSRs to reserve dedicated RUs for data packet transmission. We further presented an analytical model to study the transient performance of UORA with the proposed mechanism under bursty arrivals. The effectiveness of the proposed analytical model is verified by simulations. The impact of the dynamic varying number of RA-RUs on the access delay of the data packets transmission and the access success probability of UORA was then explored.

[1] M. Kamel, W. Hamouda, and A. Youssef, “Ultra-dense networks: A survey,” IEEE Commun. Surveys Tuts., vol. 18, no. 4, pp. 2522–2545, 4th Quart., 2016.
[2] “IEEE P802.11ax/D3.3 Draft standard for information technology -- Telecommunications and information exchange between systems -- Local and metropolitan area networks -- Specific requirements -- Part 11: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications -- Amendment 1: Enhancements for high efficiency WLAN,” Dec. 2018.
[3] D. J. Deng, K. C. Chen, and R. S. Cheng, “IEEE 802.11ax: Next generation wireless local area networks,” in Proc. 10th Int. Conf. Heterogeneous Netw. Qual. Rel. Security Robustness (QShine), pp. 77–82, 2014.
[4] T. Uwai, T. Miyamoto, Y. Nagao, L. Lanante, M. Kurosaki, and H. Ochi, “Performance evaluation of OFDMA random access in IEEE802.11ax”, Proc. ISPACS 2016, 2016.
[5] L. Lanante, H. Ochi, T. Uwai, Y. Nagao, M. Kurosaki and C. Ghosh, ”Performance analysis of the 802.11ax UL OFDMA random access protocol in dense networks,” 2017 IEEE International Conference on Communications (ICC), Paris, May 2017.
[6] H. Yang, D. J. Deng, and K. C. Chen, “Performance analysis of IEEE 802.11ax UL OFDMA-based random access mechanism,” 2017 IEEE Global Communications Conference (GLOBECOM), Singapore, December 2017.
[7] J. Bai, H. Fang, J. Suh, O. Aboul-Magd, E. Au, and X. Wang, “Adaptive uplink OFDMA random access grouping scheme for ultradense networks in IEEE 802.11ax,” in 2018 IEEE/CIC International Conference on Communications in China (ICCC). IEEE, pp. 34–39, 2018.
[8] K. Dovelos and B. Bellalta, “Optimal resource allocation in IEEE 802.11ax uplink OFDMA with scheduled access,” arXiv preprint arXiv:1811.00957, 2018.
[9] D. Bankov, A. Didenko, E. Khorov, and A. Lyakhov, “OFDMA uplink scheduling in IEEE 802.11ax networks,” IEEE International Conference on Communications (ICC), pp. 1–6, May 2018.
[10] G. Naik, S. Bhattarai, and J.-M. J. Park, “Performance analysis of uplink multi-user OFDMA in IEEE 802.11ax,” IEEE International Conference on Communications (ICC), pp. 1-6, May 2018.
[11] S. Bhattarai, G. Naik, and J.-M. J. Park, “Uplink resource allocation in IEEE 802.11ax,” IEEE International Conference on Communications (ICC), pp. 1–6, May 2019.
[12] D. G. Filoso, R. Kubo, K. Hara, S. Tamaki, K. Minami, and K. Tsuji, “Proportional-based resource allocation control with QoS adaptation for IEEE 802.11ax,” IEEE International Conference on Communications (ICC), pp. 1–6, June 2020.
[13] B. Binoy and B. S. Vineeth, “Minimum delay scheduling under average power constraint for 802.11ax uplink,” IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS), pp. 1-5, Dec. 2019.
[14] M. Wu, J. Wang, Y. Zhu, and J. Hong, “High throughput resource unit assignment scheme for OFDMA-based WLAN,” IEEE Wireless Communications and Networking Conference (WCNC), pp. 1–8, April 2019.
[15] B. Bellalta and K. Kosek-Szott, “AP-initiated multi-user transmissions in IEEE 802.11ax WLANs,” Ad Hoc Networks, vol. 85, pp. 145–159, Mar. 2019.
[16] N. Shahin, R. Ali, S. W. Kim, and Y. Kim, “Cognitive backoff mechanism for IEEE802.11ax high-efficiency WLANs,” Journal of Communications and Networks, vol. 21, no. 2, pp. 158–167, Apr. 2019.
[17] C. Wei, R. G. Cheng and S. L. Tsao, “Modeling and estimation of one-shot random access for finite-user multichannel slotted ALOHA systems,” IEEE Communications Letters, vol. 16, no. 8, pp. 1196-1199, August 2012.
[18] C. Wei, R. G. Cheng and S. L. Tsao, “Performance analysis of group paging for machine-type communications in LTE networks,” IEEE Transactions on Vehicular Technology, vol. 62, no. 7, pp. 3371-3382, Sept. 2013.
[19] R. G. Cheng, C. M. Yang, R. Harwahyu, and F. Bariq, “Uplink OFDMA-based random access mechanism with bursty arrivals for IEEE 802.11ax Systems,” submitted to IEEE Communications Letter, Dec. 2020.
[20] Li-Ping Yu, “Performance analysis of packet reservation mechanism for IEEE 802.11ax uplink OFDMA-based random access (UORA),” Master Thesis, NTUST, Nov. 2020.
[21] Y. J. Choi, S. Park, and S. Bahk, “Multichannel random access in OFDMA wireless network,” IEEE J. Sel. Areas Commun., vol. 24, no. 3, pp. 603–613, Mar. 2006.
[22] R. G. Cheng, F. M. Al-Taee, J. Chen, and C. Wei, “A dynamic resource allocation scheme for group paging in LTE advanced networks,” IEEE Internet Things J., vol. 2, no. 5, pp. 427–434, Oct. 2015.
[23] Y. Zheng, J. B. Wang, Q. H. Chen, and Y. H. Zhu, “Retransmission number aware channel access scheme for IEEE 802.11ax based WLAN,” Chinese Journal of Electronics, vol. 29, no. 2, pp. 351-360, May. 2020.