IEEE 802.11ah，是新修訂的應用在物聯網上的無線網絡協議。為了處理數千個IoT設備在同一區域中正常運行，他們針對MAC層採用一種新的通道訪問機制，稱為受限存取視窗(Restricted Access Window, RAW)，透過此機制將裝置分配在多個群組，在不同的時間存取通道來達到減少競爭的目的。傳統802.11ah協議的站使用CSMA / CA機制來競爭通道訪問的權限，然而在擁擠的網路環境下依然無法有效避免碰撞。如果多個裝置具有相同的倒退(backoff)值，則裝置彼此傳送的封包會發生碰撞，導致更長的網絡延遲。此外，裝置可能產生具有較高優先權的封包需要優先被處理，由於AP不知道哪些裝置擁有這些較高優先權的數據需要發送，導致它們有機會比具有一般優先權的數據更晚向AP發送，尤其是在裝置數量密集且有許多資料需要被處理的網路環境下。本文提出一種新穎的RAW機制來提高IEEE 802.11ah的效能，以過去研究的倒退值註冊方法提出了基於通知的優先權辨析之通道存取(CPDCA)機制用於降低碰撞發生，並且通過額外的RAW，AP可以得知具有較高優先級數據待發送的裝置，並且賦予這些要發送/接收的裝置更高的特權，讓他們可以優先地存取通道。除此之外，當裝置在向AP傳送資料時會註冊一個隨機的倒退值，因此AP就能知道這些裝置是否有數據要發送並將被AP標記為已知，AP可以對這些裝置進行有效的排程來避免在傳輸數據的過程中發生碰撞。模擬結果顯示，與傳統的IEEE 802.11ah相比，我們提出的CPDCA機制在每個時隙中裝置數量較高的環境下，能獲得較高的產能和較低的碰撞率，並且對於帶有高優先權數據的裝置能使他們盡早地傳送/接收資料。數據顯示，CPDCA機制對於那些具有高優先權的資料傳送完成的時間明顯低於使用傳統的IEEE 802.11ah方法和過去研究所提出的機制。

IEEE 802.11ah is a newly devised wireless network protocol for Internet of Things (IOT). In order to handle up to thousands of IoT devices in the signal-covered area, a new channel access mechanism called Restricted Access Window (RAW) is adopted in the MAC layer. Through the RAW mechanism, devices are separated into several groups to access the channel on different time to reduce collision. Stations of the traditional 802.11ah protocol use the CSMA/CA scheme to contend the channel access privilege, in which related stations generate backoff values and have retransmission when the collision happens. Since IEEE 802.11ah AP does not know which spontaneous stations have data frames of high priority to uplink, it may cause those spontaneous stations having high priority’s uplinked data frames to uplink data frames later than the stations with regular priority’s data frames, which especially can happen in the dense network environments that may have a lot of data frames to be processed. This work proposed the Claim-based Priority-Discriminated Channel Access (CPDCA) method, which has a newly devised RAW called the Claiming RAW to let those spontaneous stations having high priority’s uplinked data frames do claims of high priority’s data uplinking, to reduce collisions. In addition, instead of generating the random backoff time after the collision happens, which the traditional IEEE 802.11 protocol adopts, this work adopted the registered backoff time mechanism, for which a station registers its next backoff time to IEEE 802.11ah AP when its current channel access is finished, i.e., a station generates the backoff time before the collision happens, based on our lab-mates’ previous research [1]. Thus, IEEE 802.11ah AP is able to schedule stations’ channel accesses based on stations’ registered backoff time of stations to avoid collisions more effectively. Through the use of the Claiming RAW and the registered backoff time mechanisms, IEEE 802.11ah AP can know which stations have high priority’s uplinked data frames and then schedule these stations to have the higher privilege to access the channel. The simulation results shown that. Comparing with the traditional IEEE 802.11ah, the simulation results shown that the proposed CPDCA mechanism has a lower collision rate and higher throughput in the network environment having the higher number of stations in each time slot; the transmission time of those stations with high priority’s uplinked data frames using the CPDCA mechanism is much lower than that of using the traditional IEEE 802.11ah mechanism and the previous method proposed in [1].

[1]C. M. Huang, R. S. Cheng, and Y. M. Li, "The Registration-Based Collision Avoidance Mechanism for IEEE 802.11ah," Proceedings of the 16th International Symposium on Pervasive Systems, Algorithms and Networks (I-SPAN), pp. 240-255, 2019.
[2]R. M. Gomathi, G. H. S. Krishna, E. Brumancia, and Y. M. Dhas, "A Survey on IoT Technologies, Evolution and Architecture," Proceedings of the International Conference on Computer, Communication, and Signal Processing (ICCCSP), pp. 1-5, 22-23 Feb. 2018.
[3]K. Kaur, "A Survey on Internet of Things – Architecture, Applications, and Future Trends," Proceedings of the 1st International Conference on Secure Cyber Computing and Communication (ICSCCC), Jalandhar, India, pp. 581-583. , 2018
[4]P. V. Paul and R. Saraswathi, "The Internet of Things — A Comprehensive Survey," Proceedings of the International Conference on Computation of Power, Energy Information and Commuincation (ICCPEIC), pp. 421-426, 22-23 March 2017.
[5]R. Varshini and A. Karthikeyan, "Internet of Things – Evolution, Architecture and Real Time Application- Survey," Proceedings of the International Conference on Vision Towards Emerging Trends in Communication and Networking (ViTECoN), pp. 1-4, 30-31 March 2019.
[6]M. Abbasi, M. H. Yaghmaee, and F. Rahnama, "Internet of Things in Agriculture: A Survey," Proceedings of the 3rd International Conference on Internet of Things and Applications (IoT), pp. 1-12, 17-18 April 2019.
[7]H. Habibzadeh, K. Dinesh, O. Rajabi Shishvan, A. Boggio-Dandry, G. Sharma and T. Soyata, "A Survey of Healthcare Internet of Things (HIoT): A Clinical Perspective," IEEE Internet of Things Journal, VOL. 7, no. 1, pp. 53-71, Jan. 2020.
[8]H. Dai, Z. Zheng and Y. Zhang, "Blockchain for Internet of Things: A Survey," IEEE Internet of Things Journal, VOL. 6, no. 5, pp. 8076-8094, Oct. 2019.
[9]D. Tyagi, R. Agrawal, and H. M. Singh, "A Survey on MAC Layer Protocols for Machine to Machine Communication," Proceedings of the International Conference on Advances in Computing, Communication Control and Networking (ICACCCN), pp. 285-288, 12-13 Oct. 2018.
[10]H. Wang and A. O. Fapojuwo, "A Survey of Enabling Technologies of Low Power and Long Range Machine-to-Machine Communications," IEEE Communications Surveys & Tutorials, VOL. 19, NO. 4, pp. 2621-2639, 2017.
[11]N. Xia, H. Chen, and C. Yang, "Radio Resource Management in Machine-to-Machine Communications—A Survey," IEEE Communications Surveys & Tutorials, VOL. 20, NO. 1, pp. 791-828, 2018.
[12]N. Kaur, J. Malhotra, and H. Sarangal, "A Survey of PHY and MAC Technologies of High Data Rate WPAN," Proceedings of the 1st IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES), pp. 1-5, 4-6 July 2016.
[13]S. Aggarwal and A. Nasipuri, "Survey and Performance Study of Emerging LPWAN Technologies for IoT Applications," Proceedings of the 16th IEEE International Conference on Smart Cities: Improving Quality of Life Using ICT & IoT and AI (HONET-ICT), pp. 069-073, 6-9 Oct. 2019.
[14]W. Ayoub, A. E. Samhat, F. Nouvel, M. Mroue, and J. Prévotet, "Internet of Mobile Things: Overview of LoRaWAN, DASH7, and NB-IoT in LPWANs Standards and Supported Mobility," Proceedings of the IEEE Communications Surveys & Tutorials, VOL. 21, NO. 2, pp. 1561-1581, 2019.
[15]"IEEE 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 2: Sub 1 GHz License Exempt Operation," IEEE Std 802.11ah-2016 (Amendment to IEEE Std 802.11-2016, as amended by IEEE Std 802.11ai-2016), pp. 1-594, 2017.
[16]Y. Liu, J. Guo, P. Orlik, Y. Nagai, K. Watanabe, and T. Sumi, "Coexistence of 802.11ah and 802.15.4g Networks," Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), pp. 1-6, 15-18 April 2018.
[17]E. Khorov, A. Lyakhov, A. Krotov, and A. Guschin, "A Survey on IEEE 802.11 ah: An Enabling Networking Technology for Smart Cities," Computer Communications, VOL. 58, pp. 53-69, 2015.
[18]M. S. Meera and S. N. Rao, "A Survey of the State of the Art of 802.11ah," Proceedings of the IEEE International Conference on Computational Intelligence and Computing Research (ICCIC), pp. 1-4, 14-16 Dec. 2017.
[19]L. Qiao, Z. Zheng, W. Cui, and L. Wang, "A Survey on Wi-Fi HaLow Technology for Internet of Things," Proceedings of the 2nd IEEE Conference on Energy Internet and Energy System Integration (EI2), pp. 1-5, 20-22 Oct. 2018.
[20]L. Tian, J. Famaey, and S. Latré, "Evaluation of the IEEE 802.11ah Restricted Access Window mechanism for dense IoT networks," Proceedings of the 17th IEEE International Symposium on A World of Wireless, Mobile and Multimedia Networks (WoWMoM), pp. 1-9, 21-24 June 2016.
[21]B. Domazetović and E. Kočan, "Packet Error Rate in IEEE 802.11ah Use Case Scenarios," Proceedings of the 25th Telecommunication Forum (TELFOR), pp. 1-4, 21-22 Nov. 2017.
[22]Z. Zhu, Z. Zhong, and Z. Fan, "A station Regrouping Method for Contention based IEEE 802.11ah Wireless LAN," Proceedings of the 13th IEEE International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), pp. 1-6, 9-11 Oct. 2017.
[23]T. Chang, C. Lin, K. C. Lin, and W. Chen, "Traffic-Aware Sensor Grouping for IEEE 802.11ah Networks: Regression based Analysis and Design," Proceedings of the IEEE Transactions on Mobile Computing, VOL. 18, NO. 3, pp. 674-687, 2019.
[24]H. Mosavat-Jahromi, Y. Li, and L. Cai, "A Throughput Fairness-based Grouping Strategy for Dense IEEE 802.11ah Networks," Proceedings of the 30th IEEE Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), pp. 1-6, 8-11 Sept. 2019.
[25]X. Zhang and K. L. Yeung, "A Novel AID Shuffle Mechanism for RAW Slot Assignment in IEEE 802.11ah Networks," Proceedings of the 43rd IEEE Conference on Local Computer Networks (LCN), pp. 159-166, 1-4 Oct. 2018.
[26]J. Kim and I. Yeom, "QoS enhanced channel access in IEEE 802.11ah networks," Proceedings of the 17th International Symposium on Communications and Information Technologies (ISCIT), pp. 1-6, 25-27 Sept. 2017.
[27]N. F. Charania, M. K. Giluka, B. R. Tamma, and A. Franklin, "Dearf: Delay and Energy Aware Raw Formation Scheme to Support Delay Sensitive M2M Traffic in IEEE 802.11 ah Networks," arXiv preprint arXiv:1709.03723, 2017.
[28]N. Ahmed, D. De, and M. I. Hussain, "A QoS-aware MAC Protocol for IEEE 802.11ah-based Internet of Things," Proceedings of the 15th International Conference on Wireless and Optical Communications Networks (WOCN), pp. 1-5, 2-4 Feb. 2018.
[29]Y. Cheng, H. Zhou, and D. Yang, "Performance Evaluation of IEEE 802.11ah Triggered Restricted Access Window Mode in Industrial Real-Time Applications," Proceedings of the IEEE/CIC International Conference on Communications in China (ICCC), pp. 325-329, 16-18 Aug. 2018.
[30]T. Kim and J. M. Chang, "Enhanced Power Saving Mechanism for Large-Scale 802.11ah Wireless Sensor Networks," IEEE Transactions on Green Communications and Networking, VOL. 1, NO. 4, pp. 516-527, 2017.
[31]Y. Zhao, O. N. C. Yilmaz, and A. Larmo, "Optimizing M2M Energy Efficiency in IEEE 802.11ah," Proceedings of the IEEE Globecom Workshops (GC Wkshps), pp. 1-6, 6-10 Dec. 2015.
[32]Y. Wang, K. K. Chai, Y. Chen, J. Schormans, and J. Loo, "Energy-Delay Aware Restricted Access Window with Novel Retransmission for IEEE 802.11ah Networks," Proceedings of the IEEE 59th Global Communications Conference (GLOBECOM2016), pp. 1-6, 4-8 Dec. 2016.
[33]V. Loginov, E. Khorov, and A. Lyakhov, "On Throughput Estimation with TXOP Sharing in IEEE 802.11ah Networks," Proceedings of the IEEE International Black Sea Conference on Communications and Networking (BlackSeaCom), pp. 1-5, 6-9 June 2016.
[34]S. Kumar, H. Lim, and H. Kim, "Hierarchical MAC Protocol with Multi-Channel Allocation for Enhancing IEEE 802.11ah Relay Networks," Proceedings of the International Wireless Communications and Mobile Computing Conference (IWCMC), pp. 1458-1463, 24-28 Aug. 2015.
[35]A. Tandon, T. J. Lim, and U. Tefek, "Sentinel based Malicious Relay Detection in Wireless IoT Networks," Journal of Communications and Networks, VOL. 21, NO. 5, pp. 458-468, 2019.