Document Type

Theses, Ph.D

Disciplines

2. ENGINEERING AND TECHNOLOGY, 2.2 ELECTRICAL, ELECTRONIC, INFORMATION ENGINEERING, Electrical and electronic engineering

Abstract

The IEEE 802.11ax standard was approved in February 2021. This standard allows users to access different channel bandwidths to transmit their packets under the Orthogonal Frequency Division Multiple Access (OFDMA) mechanism. As the number of Internet users and the number of Internet applications increase, the allocation of channel resources has been a challenge in WLANs. Different types of applications, such as real-time video conferencing, online gaming and large-scale data transfers, generate different requirements in terms of throughput, latency and reliability. Consequently, the diversity in users’ channel bandwidth demands is increasing. Under the OFDMA mechanism, the packets can be allocated into Resource Units (RUs) for simultaneous transmission according to their demands for channel bandwidth, and packets generated by multiple users can be allocated into the same RU to improve the channel utilisation. However, RU allocation is granular which means the network can only allocate an integer number of RUs rather than allocate a fractional number of RUs. Therefore, when the network allocates three or more RUs to complete packet transmissions that could be completed with only two RUs, this reduces channel utilisation and increases channel wastage. Hence, how to allocate as few RUs as possible to support packet transmissions without sacrificing user experience has been a challenge in deploying the IEEE 802.11ax OFDMA mechanism. In addition, since each RU can be used to transmit packets generated by multiple users, it is necessary to prevent the packets generated by a given user from always being transmitted first, as this may result in a large disparity in the user experience, thereby causing unfairness in the network. Therefore, controlling the fairness of the WLANs has also been a challenge for RU allocation under the IEEE 802.11ax OFDMA mechanism. To improve the channel utilisation and the fairness of WLANs under the IEEE 802.11ax OFDMA mechanism, this thesis first proposes a Dynamic Programming algorithm combined with Timsort (DPT). DPT improves the channel utilisation by Dynamic Programming (DP) and improves the fairness with Timsort which controls the order of packet transmissions in each RU according to the average waiting time per packet of the users who generate these packets. However, if the packets that need to arrive at the receiver in order are allocated into different RUs or Timsort changes their order, it will cause packets to be reordered. To preserve packet ordering, this thesis proposes an Improved Dynamic

Programming algorithm combined with Timsort (IDPT) to solve the RU allocation problem for the IEEE 802.11ax OFDMA mechanism. The simulation experiments compare the channel utilisation, Jain’s Fairness Index (JFI), R-value and calculation time of DPT and IDPT with other optimisation techniques. According to the simulation results, DPT can generate a RU allocation scheme that improves the efficiency and fairness of the network, but it can result in packet re-ordering issues. IDPT improves the fairness by a dynamic RU allocation interval control and preserves packet ordering with an acceptable trade-off with regard to channel utilisation

DOI

https://doi.org/10.21427/461H-1516

Creative Commons License

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.

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