IEEE 802.11ax: challenges and requirements for future high efficiency wifi

The popularity of IEEE 802.11 based wireless local area networks (WLANs) has increased significantly in recent years because of their ability to provide increased mobility, flexibility, and ease of use, with reduced cost of installation and maintenance. This has resulted in massive WLAN deployment in geographically limited environments that encompass multiple overlapping basic service sets (OBSSs). In this article, we introduce IEEE 802.11ax, a new standard being developed by the IEEE 802.11 Working Group, which will enable efficient usage of spectrum along with an enhanced user experience. We expose advanced technological enhancements proposed to improve the efficiency within high density WLAN networks and explore the key challenges to the upcoming amendment.Peer ReviewedPostprint (author's final draft

A Survey on Multi-AP Coordination Approaches over Emerging WLANs: Future Directions and Open Challenges

Recent advancements in wireless local area network (WLAN) technology include IEEE 802.11be and 802.11ay, often known as Wi-Fi 7 and WiGig, respectively. The goal of these developments is to provide Extremely High Throughput (EHT) and low latency to meet the demands of future applications like as 8K videos, augmented and virtual reality, the Internet of Things, telesurgery, and other developing technologies. IEEE 802.11be includes new features such as 320 MHz bandwidth, multi-link operation, Multi-user Multi-Input Multi-Output, orthogonal frequency-division multiple access, and Multiple-Access Point (multi-AP) coordination (MAP-Co) to achieve EHT. With the increase in the number of overlapping APs and inter-AP interference, researchers have focused on studying MAP-Co approaches for coordinated transmission in IEEE 802.11be, making MAP-Co a key feature of future WLANs. Moreover, similar issues may arise in EHF bands WLAN, particularly for standards beyond IEEE 802.11ay. This has prompted researchers to investigate the implementation of MAP-Co over future 802.11ay WLANs. Thus, in this article, we provide a comprehensive review of the state-of-the-art MAP-Co features and their shortcomings concerning emerging WLAN. Finally, we discuss several novel future directions and open challenges for MAP-Co.Comment: The reason for the replacement of the previous version of the paper is due to a change in the author's list. As a result, a new version has been created, which serves as the final draft version before acceptance. This updated version contains all the latest changes and improvements made to the pape

An optimization of network performance in IEEE 802.11ax dense networks

The paper focuses on the optimization of IEEE 802.11ax dense networks. The results were obtained with the use of the NS-3 simulator. Various network topologies were analyzed and compared. The advantage of using MSDU and MPDU aggregations in a dense network environment was shown. The process of improving the network performance for changes in the transmitter power value, CCA Threshold, and antenna gain was presented. The positive influence of BSS coloring mechanism on overal network efficiency was revealed. The influence of receiver sensitivity on network performance was determined

Insights on the Next Generation WLAN: High Experiences (HEX)

Wireless local area network (WLAN) witnesses a very fast growth in the past 20 years by taking the maximum throughput as the key technical objective. However, the quality of experience (QoE) is the most important concern of wireless network users. In this article, we point out that poor QoE is the most challenging problem of the current WLAN, and further analyze the key technical problems that cause the poor QoE of WLAN, including fully distributed networking architecture, chaotic random access, awkward ``high capability'', coarse-grained QoS architecture, ubiquitous and complicated interference, ``no place'' for artificial intelligence (AI), and heavy burden of standard evolving. To the best of our knowledge, this is the first work to point out that poor QoE is the most challenging problem of the current WLAN, and the first work to systematically analyze the technical problems that cause the poor QoE of WLAN. We highly suggest that achieving high experiences (HEX) be the key objective of the next generation WLAN

고밀도 무선랜 동시 전송 향상 기법

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 최성현.무선 통신에 대한 수요가 증가함에 따라, Wi-Fi로 흔히 알려진 IEEE 802.11 표준 기반 무선랜(WLAN, Wireless Local Area Network)은 어디에서나 찾아볼 수 있는 기술로 거듭났다. 이로 인해 무선랜의 고밀화, 즉 공간적으로 인접한 많은 AP(Access Point)와 STA(station)들이 동일한 주파수 채널을 사용하며 이로 인해 한 단말이 얻을 수 있는 성능이 제한되는 현상이 두드러지고 있다. 따라서 이러한 고밀도 무선랜 환경에서는 단일 전송에 대한 스펙트럼 효율 뿐만 아니라 주파수 자원의 공간 재사용(spatial reuse)의 중요성 또한 강조된다. 즉, 특정 공간 내에서 얼마나 많은 동시 전송이 가능한지가 중요한 이슈로 자리매김하고 있다. 본 학위논문에서는 고밀도 무선랜 환경에서 더 많은 동시 전송을 성공시키기 위하여 다음과 같은 세 가지 전략을 고려한다. (i) 매체접근제어(MAC, Medium Access Control) 계층의 ACK(Acknowledgment) 및 CTS(Clear-To-Send) 프레임에 대한 송신 전력 제어, (ii) 반송파 감지 임계값(CST, Carrier-Sense Threshold) 적응, (iii) 동시 송신 및 수신 (STR, Simultaneous Transmit and Receiver), 즉 동일대역 전이중 통신(in-band full duplex). 첫번째로, 본 학위 논문에서는 데이터 프레임에 의한 동일 채널 간섭(CCI, Co-Channel Interference)보다 덜 조명되어 왔던 MAC ACK 프레임에 의해 발생하는 CCI에 주목한다. 확률적 기하 분석(stochastic geometry analysis)을 기반으로 ACK 프레임의 송신 전력 조절의 필요성을 확인하였으며, 이를 바탕으로 동적 ACK 프레임 송신 전력 제어 알고리즘인 Quiet ACK(QACK)을 제안한다. QACK은 데이터 프레임 수신 중 수행되는 CCI 검출 및 CCI 전력 추정 기법과 ACK 프레임 전송 통계를 활용하여 세밀하고 신속하게 ACK 프레임의 송신 전력을 조절한다. 더불어, QACK을 바탕으로 CTS 프레임 송신 전력을 조절하여 더 많은 동시 전송이 시도될 수 있게 하는 Quiet CTS(QCTS)라는 알고리즘 또한 제안한다. QACK의 실현 가능성과 성능은 SDR(Software-Defined Radio) 기반 프로토타입을 통해 검증하며 기존 방식 대비 약 1.5배 높은 수율을 얻을 수 있음을 확인한다. 보다 일반적인 무선랜 환경에서의 QACK 및 QCTS의 성능은 ns-3를 사용한 다양한 시뮬레이션을 통해 평가한다. 다음으로, 동시에 더 많은 동시 전송이 시도될 수 있도록 간섭원(interferer node)과 목적 노드(destination node)에 따라 CST를 제어하는 ​​CST 적응 방법, FACT(Fine-grained Adaptation of Carrier-sense Threshold)를 제안한다. 제안하는 방법은 무선랜 표준에서 이미 정의되어 있는 기능을 사용하므로 상용 무선랜 기기에서 쉽게 구현할 수 있다. 또한 FACT 및 다른 CST 적응 기법과 함께 동작할 수 있는 CCA(Clear Channel Assessment) 오버헤드 감소 기법을 제안하며, 제안한 기법들의 성능을 ns-3 시뮬레이션을 통해 비교평가한다. 시뮬레이션 결과를 통해 제안한 방법이 기존 방법에 비해 네트워크 전체 수율을 큰 폭으로 향상시킬 수 있음을 확인한다. 마지막으로, 무선랜에서 STR을 가능하게하는 새로운 MAC 프로토콜, 즉 MASTaR(MAC Protocol for Access points in Simultaneous Transmit and Receive mode)를 기존 무선랜 표준을 준수하는 방법으로 제안한다. 또한 MASTaR 동작을 위해 필요한 물리계층에서 디지털 자가 간섭 상쇄(SIC, Self-Interference Cancellation) 전략을 제안하며 그 실현 가능성과 성능을 3차원 광선 추적(3D-ray tracing) 기반 시뮬레이션을 통해 다양한 측면에서 평가한다. 시뮬레이션 결과는 현재 무선랜 MAC 프로토콜보다 최대 2.58배 높은 수율이 MASTaR를 통해 얻어질 수 있음을 보인다. 요약하면, 본 학위논문에서는 ACK 및 CTS 프레임의 송신 전력 제어 알고리즘과 CST 적응 및 STR을 위한 프로토콜을 제안한다. 제안한 알고리즘 및 프로토콜의 실현 가능성과 성능은 수치 해석, 3차원 광선 추적, ns-3 기반 시스템 수준(system-level) 시뮬레이션, SDR 기반 프로토타입 등 다양한 방법론을 통해 입증한다.With increasing demand for wireless connectivity, IEEE 802.11 wireless local area network (WLAN), a.k.a. Wi-Fi, has become ubiquitous and continues to grow in number. This leads to the high density of WLAN, where many access points (APs) and client stations (STAs) operate on the same frequency channel. In a densely deployed WLAN, greater emphasis is placed on the importance of spatial reuse as well as spectral efficiency. In other words, it is of particular importance how many simultaneous transmissions are possible in a given area. In this dissertation, we consider the following three strategies to increase the number of successful simultaneous transmissions: (i) Transmit power control for medium access control (MAC) acknowledgment (ACK) and clear-to-send (CTS) frames, (ii) carrier sense threshold (CST) adaptation, and (iii) simultaneous transmit and receive (STR), i.e., in-band full-duplex communication. First, this dissertation sheds light on the co-channel interference (CCI) caused by 802.11 MAC ACK frames, which has been less studied than the CCI caused by data frames. Based on stochastic geometry analysis, we propose Quiet ACK (QACK), a dynamic transmit power control algorithm for ACK frames. Fine-grained transmit power adjustment is enabled by CCI detection and CCI power estimation in the middle of a data frame reception. A power control algorithm for clear-to-send (CTS) frame transmission, namely Quiet CTS (QCTS) is also proposed based on QACK. Our prototype using software-defined radio shows the feasibility and performance gain of QACK, i.e., 1.5X higher throughput than the legacy 802.11 WLAN. The performance of QACK and QCTS is further evaluated in more general WLAN environments via extensive simulations using ns-3. Second, a fine-grained CST adaptation method, which controls CST depending on both interferer and destination nodes, is proposed to improve spatial reuse in WLAN. The proposed method utilizes pre-defined functions in the WLAN standard, thus making itself easily implementable in commercial WLAN devices. Supplementary clear channel assessment (CCA) method is also proposed to further enhance network performance by reducing CCA overhead. The performance of the proposed methods is comparatively evaluated via ns-3 simulation. Simulation results show that the proposed methods significantly improve network throughput compared with the legacy method. Finally, a novel MAC protocol that enables STR in 802.11 WLAN, namely MASTaR, is proposed based on standard-compliant methods. Also, a digital self-interference cancellation (SIC) strategy is proposed to support the operation of MASTaR. The feasibility and the performance of MASTaR are extensively evaluated via 3D ray tracing-based simulation. The simulation results demonstrate that significant performance enhancement,e.g., up to 2.58X higher throughput than the current 802.11 MAC protocol, can be achieved by an STR-capable access point. In summary, we propose an algorithm for ACK and CTS transmission power control and two protocols each for CST adaptation and STR which enhance the efficiency of WLAN by enriching simultaneous transmission. The feasibility and the performance of the algorithm and protocols are demonstrated via various methodologies including numerical analysis, 3D ray-tracing, ns-3 based system-level simulation, and prototype using a software-defined radio.1 Introduction 1 1.1 Motivation 1 1.2 Overview of Existing Approaches 3 1.2.1 Transmit power control for CCI reduction 3 1.2.2 CST adaptation for better spatial reuse 3 1.2.3 MAC protocol for STR in WLAN 4 1.3 Main Contributions 7 1.3.1 Quiet ACK: ACK Transmit Power Control 7 1.3.2 FACT: CST adaptation scheme 8 1.3.3 MASTaR: MAC protocol for STR in WLAN 8 1.4 Organization of the Dissertation 9 2 Quiet ACK: ACK Transmit Power Control in IEEE 802.11 WLANs 10 2.1 Introduction 10 2.2 Numerical Analysis 12 2.2.1 System Model 13 2.2.2 AISR Expansion by ACK Power Control 18 2.2.3 Optimization of ACK Outage Tolerance 19 2.3 QACK: Proposed ACK power Control 21 2.3.1 CCI Detection and CCI Power Estimation 22 2.3.2 Link Margin Estimation 26 2.3.3 ACK Power Adjustment 29 2.3.4 Conditional QACK Enabling/Disabling 30 2.4 Prototyping-Based Feasibility Evaluation 30 2.4.1 Feasibility of CCI Detection and CCI Power Estimation 30 2.4.2 Throughput Enhancement by QACK 33 2.5 Simulation-based Performance Evaluation 34 2.5.1 Two BSS Topology 35 2.5.2 Multiple BSS Environment 38 2.5.3 Coexistence with Legacy Devices 41 2.6 Quiet CTS: Proposed CTS Power Control 41 2.6.1 Problem Statement 41 2.6.2 CTS Power Control 42 2.6.3 Relationship with Quiet ACK 44 2.6.4 Simulation Results 45 2.7 Summary 48 3 FACT: Fine-Grained Adaptation of Carrier Sense Threshold in IEEE 802.11 WLANs 49 3.1 Introduction 49 3.2 Preliminaries 50 3.2.1 IEEE 802.11h Transmit Power Control (TPC) 50 3.2.2 IEEE 802.11ah Basic Service Set (BSS) Color 52 3.3 FACT: Proposed CST Adaptation Scheme 52 3.3.1 Basic Principle 53 3.3.2 Challenges and Solutions 54 3.3.3 Specification 54 3.3.4 Transmit Power Adjustment 56 3.3.5 Conditional Update of CST 57 3.4 Blind CCA and Backoff Compensation 57 3.4.1 Blind CCA 58 3.4.2 Backoff Compensation 59 3.5 Performance Evaluation 59 3.6 Summary 63 4 MASTaR: MAC Protocol for Access Points in Simultaneous Transmit and Receive Mode 64 4.1 Introduction 64 4.2 Preliminaries 68 4.2.1 Explicit Block ACK 68 4.2.2 Capture Effect 69 4.3 MASTaR: Proposed MAC Protocol 70 4.3.1 PTX Identification 70 4.3.2 Initial Training 73 4.3.3 Link Map Management 73 4.3.4 Secondary Transmission 74 4.4 Feasibility Study 76 4.4.1 Analog SIC and Channel Modeling 76 4.4.2 Digital SIC for WLAN 79 4.5 Performance Evaluation 83 4.5.1 Simulation with UDP Data Traffic 87 4.5.2 Simulation with Voice and Data Traffic 100 4.6 Summary 102 5 Concluding Remarks 103 5.1 Research Contributions 103 5.2 Future Work 104 Abstract (In Korean) 110Docto