Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Electrical and Computer Engineering

Supervisor

Wang, Xianbin

Abstract

Due to the few available Wi-Fi channels and the existence of other technologies, the channel selected by an access point (AP) to be assigned to the network is of extreme importance for network performance due to different interference conditions at different channels. While channel selection algorithms have been proposed, very few of them are user-centric, which could incur a large signaling overhead. As a result, in this thesis, a channel selection algorithm with a low-overhead station (STA) reporting mechanism is proposed, which utilizes the spatial correlation of interference by clustering close-by STAs in order to reduce the feedback overhead by adopting cluster-based feedback instead of STA-based. As a result, the channel selection feedback overhead could be reduced without sacrificing the accuracy of the feedback.

In addition, the lack of coordination between APs exacerbates performance degradation due to interference. As a result, multi-AP coordination has become inevitable. Multiple studies have proposed multi-AP coordination schemes which aim to achieve coordination in either the spatial or the frequency domain. Despite the improvement shown by current multi-AP coordination schemes, their uni-dimensional design places a limitation on the ability of the network to coordinate the transmissions sufficiently in varying scenarios where the domain for coordination is not guaranteed to remain suitable. As a result, this thesis proposes a multi-AP coordination scheme with a multi-dimensional design that aims to manage interference by allowing the APs to concurrently deploy coordination on both the spatial and frequency domains, thus providing a higher degree of reliability.



Summary for Lay Audience

Due to the few Wi-Fi channels and the existence of other technologies, the channel selected by an AP to be assigned to the network is important for network performance due to different interference conditions at different channels. While channel selection algorithms have been proposed, very few consider feedback from the STAs on the candidate channels, which could incur a large signaling overhead. As a result, in this thesis, a channel selection algorithm with a low-overhead STA reporting mechanism is proposed to address this challenge. The proposed algorithm makes use of the spatial correlation of interference by clustering close-by STAs to reduce the feedback overhead by adopting cluster-based feedback instead of involving each STA. Hence, the channel selection feedback overhead could be reduced without sacrificing the accuracy of the information.

In addition, the increasing density of WLAN networks has led to the ubiquitous existence of interference among multiple basic service sets (BSSs). Given the limited available radio resources and the growing density of WLAN networks, coordinated transmissions between different APs have become inevitable in the upcoming Wi-Fi standard, IEEE 802.11be, to improve performance in ultra-dense deployment scenarios. 802.11be introduces coordinated spatial reuse (CSR), where the transmission power of each neighboring co-channel AP at a different location is adjusted to keep the interference between BSSs to be at a tolerable level. Despite the improvements shown by CSR, it suffers in ultra-dense deployments without being able to guarantee tolerable interference conditions due to the spatial proximity of STAs from different BSSs, a fundamental limitation of spatial domain coordination. Hence, this thesis proposes a multi-AP coordination scheme with a multi-dimensional design that aims to manage interference by allowing the APs to adopt coordination on both the spatial and frequency domains. Consequently, a multi-AP network is not limited to a single sub-optimal domain for coordinated interference minimization and can adopt whichever dimension is more suitable to the given deployment scenario. Through simulation results and analysis, it is demonstrated that the proposed multi-AP coordination algorithm achieves the design goal. As a result, the proposed algorithm is necessary for improving performance in future ultra-dense WLAN deployments.

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