Wireless Resource Management Strategies in High Density Wireless LANs
양창목 · Seoul National University Open Repository (Seoul National University) · 2020
IEEE 802.11 wireless local area network (WLAN), also referred to Wi-Fi, has been developed and enhanced constantly to meet demand for explosively increasing mobile data traffic and applications.This demand leads to popularization of Wi-Fi devices, use of multiple mobile devices, and increase of the number of devices.However, as more users in the limited areas, the density of networks becomes higher progressively compared to the past, resulting in new problems, such as increased collision/interference level, throughput starvation, energy waste, and lack of wireless resources in WLANs.These problems are not much highlighted in the past since numerous devices and high density networks had not be considered carefully, but the next generation Wi-Fi will necessarily become and pursue high density.In this dissertation, we address the problems in the newly added features, wide bandwidth operation and target wake time (TWT).These two new features are related to wireless resources, frequency and time.For wide bandwidth operation, we investigate hidden node problem with wide bandwidth operation, in which interference only exist on secondary channels, called secondary hidden problem.We propose HIA-Tus, adjusting transmission bandwidth if secondary hidden interference is detected.We evaluate the feasibility of HIATus with extensive measurement results, and predict the performance of HIATus, achieving 14.4× higher throughput compared with the baseline 802.11ac.For TWT, we first address scheduling strategies with TWT.We demonstrate the issues for TWT scheduling, such as requirements and scheduling result notice to the STAs, and propose a method how to get the information for scheduling by applying features in the standard.Then, we apply existing scheduler to TWT, max-rate and proportional fairness.We evaluate the performance of TWT with extensive ns-3 simulation results, including not only throughput performance but also power consumption i and energy efficiency.We demonstrate that TWT always achieves energy efficiency, and throughput efficiency can be enhanced when the network becomes denser.All the strategies and methods proposed in this work are thoroughly standard-compliant.We also investigate existing rate adaptation schemes with TWT.TWT yields new problem with the conventional loss-based rate adaptation schemes, since TWT has a nature of transmission interruption and it disturbs to collect loss statistics.We demonstrate that the performance of loss-based rate adaptation, e.g., Minstrel, is degraded severely with TWT.For uplink rate control in TWT, we propose VAULT, a received SNR-based uplink rate control scheme using trigger frame.We implement VAULT in ns-3 and evaluate the performance of VAULT, achieving up to 73% higher throughput compared with Minstrel without statistics reset.In summary, we claim issues in the new features for the next-generation WLANs, which are related to wireless resource, i.e., frequency and time.We demonstrate the problems in the features, which had not been exposed before.Then we propose new schemes and strategies to solve the problems for the new features.The proposed schemes and strategies have been evaluated with extensive measurement and simulation results.All the proposed schemes and strategies in the dissertation are thoroughly standard-compliant.