1 QoS in IEEE 802.11-based Wireless Networks: A Contemporary Survey Aqsa Malik, Junaid Qadir, Basharat Ahmad, Kok-Lim Alvin Yau, Ubaid Ullah. Abstract—Apart from mobile cellular networks, IEEE 802.11- requirements at a lower cost. In IEEE 802.11 WLANs, the based wireless local area networks (WLANs) represent the error and interference prone nature of wireless medium—due most widely deployed wireless networking technology. With the to fading and multipath effects [2]—makes QoS provisioning migration of critical applications onto data networks, and the emergence of multimedia applications such as digital audio/video even more challenging. The combination of best-effort routing, and multimedia games, the success of IEEE 802.11 depends datagram routing, and an unreliable wireless medium, makes critically on its ability to provide quality of service (QoS). A lot the task of QoS provisioning in IEEE 802.11 WLANs very of research has focused on equipping IEEE 802.11 WLANs with challenging. features to support QoS. In this survey, we provide an overview of In this survey, we provide a focused overview of work these techniques. We discuss the QoS features incorporated by the IEEE 802.11 standard at both physical (PHY) and media access done to ensure QoS in the IEEE 802.11 standard. We have control (MAC) layers, as well as other higher-layer proposals. We the following three goals: (i) to provide a self-contained also focus on how the new architectural developments of software- introduction to the QoS features embedded in the IEEE defined networking (SDN) and cloud networking can be used to 802.11 standard; (ii) to provide a layer-wise description and facilitate QoS provisioning in IEEE 802.11-based networks. We survey of techniques adopted for ensuring QoS in the IEEE conclude this paper by identifying some open research issues for future consideration. 802.11 networks; and (iii) to survey the applications of new networking architectures—such as software defined networks Index Terms—Quality of service (QoS), IEEE 802.11, wireless (SDN) and cloud computing—for QoS provisioning in the networks. IEEE 802.11-based WLANs. Contributions of this paper: A lot of research has been I. INTRODUCTION conducted on the topic of QoS [3], including numerous The IEEE 802.11 wireless local area networking (WLAN) surveys that have focused on the QoS problems for specific standard defines one of the most widely deployed wireless wireless networks such as wireless sensor networks (WSNs) technologies in the world. The popularity of wireless network- [4], wireless mesh networks (WMNs) [5], and IEEE 802.11- ing is driven by the ubiquity of portable mobile hand-held based WLANs [6] [7] [8] [9]. Our work is different from the devices, and the convenience of untethered communications. previous work in that we provide an updated account of QoS With the increasing deployment of multimedia content on literature in IEEE 802.11-based wireless networks including a the Internet—such as digital video, voice over IP (VoIP), discussion of recent architectural developments, such as cloud videoconferencing, and multi-player networked games—along computing and SDN, that facilitate finer network management with the deployment of time-sensitive critical applications, control, so we have reinvigorated the interest of the research there is a strong motivation to develop QoS features to meet community in providing high QoS in IEEE 802.11-based the more stringent performance requirements [1]. wireless networks. In addition to highlighting the QoS features While the Internet and data networking models of the incorporated into the IEEE 802.11 networking standard, we arXiv:1411.2852v1 [cs.NI] 11 Nov 2014 IEEE 802.11 WLAN technology, which are based on the also highlight different QoS approaches pertaining to different datagram delivery model of IP, provide simple, adaptive and layers of the TCP/IP model. fault resilient network, they are ill-suited to QoS provisioning. The underlying datagram model of IP is a best-effort service— Organization of this paper: This survey is organized in i.e., while the network tries to deliver packet to the destination the following way. In Section II, we provide a broad-based correctly without any packet losses, it makes no guarantees. introduction on the general area of Internet QoS. In Section Multimedia applications, in particular, need stronger guaran- III, we present the QoS features which are intrinsic to IEEE 1 tees about the minimum throughput and maximum latency to 802.11 for the physical (PHY) and the medium access control work satisfactorily. An expensive solution for ensuring QoS is (MAC) layers. We provide an overview of the IEEE 802.11 to overprovision. Most of the Internet QoS effort has focused a/b/g and higher-throughput IEEE 802.11 standards (802.11 on how to get a network with less capacity meet application n/ac/ad) in Sections III-A and III-B. We follow this by a discussion on MAC layer QoS features proposed in IEEE Aqsa Malik, Basharat Ahmad and Ubaid Ullah are students at the School 802.11 in Section III-C. Apart from the QoS features that are of Electrical Engineering and Computer Science (SEECS) at the National part of the IEEE 802.11 standard, various work has focused University of Sciences and Technology (NUST), Pakistan. Junaid Qadir is an Assistant Professor at the Electrical Engineering Department of SEECS, NUST. Kok-Lim Alvin Yau is an Associate Professor at the Faculty of Science 1We note here that the IEEE 802.11 standard directly addresses the PHY and Technology, Sunway University, Malaysia and MAC layers only. 2 on QoS improvement including work at the network layer TABLE I (discussed in Section IV), the transport layer (discussed in ACRONYMS USED IN THIS PAPER. Section V), the application layer (discussed in Section VI) Acronym Expanded Form as well as cross-layer work (discussed in Section VII). The promise of recent architectural developments, such as cloud AMC Adaptive Modulating Scheme APSD Automatic Power Save Delivery computing and SDN, in enabling QoS, along with a survey ARQ Automatic Repeat reQuest of proposed work, is provided in Section VIII. Thereafter, we ATM Asynchronous Transfer Mode discuss some open research issues in Section IX. Finally, we BER Bit Error Rate BPSK Binary Phase Shift Keying provide concluding remarks in Section X. CAC Call Admission Control CAP Control Access Period CbWN Cloud-based Wireless Network To facilitate the reader, acronyms used in this paper are CW Contention Window collected in Table I as a convenient reference. DCF Distributed Coordination Function DFS Distributed Fair Scheduling DIFS DCF Interframe Space II. INTERNET QOS—A BROAD INTRODUCTION DiffServ Differentiated Services DSSS Direct-Sequence Spread Spectrum There has been a lot of work on Internet QoS, the bulk of EDCA Enhanced Distributed Channel Access which has focused on wired networks [10] [11]. While many EDCF Extended DCF EDD Earliest Due Date of the ideas developed for Internet QoS are also applicable FEC Forward Error Correction more broadly to wireless QoS, wireless networks do provide FHSS Frequency Hopping Spread Spectrum some unique challenges motivating the development of new FCFS First-Come First-Served FIFO First In First Out methods [12]. In this section, we provide a broad overview of HCF Hybrid Coordination Function the abundant literature on Internet QoS. HCCA HCF Controlled Channel Access IntServ Integrated Services The original applications of the Internet—such as file trans- LTE Long-Term Evolution fer and email—are elastic applications which are not bound MAC Media Access Control by stringent performance requirements, and therefore match MDP Markov Decision Process MPDU MAC Protocol Data Unit well with the Internet’s datagram delivery model. The modern MPLS Multiprotocol Label Switching Internet world, which is full of multimedia applications, re- MIMO Multiple Input Multiple Output quires QoS guarantees that users have come to expect from the NUC Network Utilization Characteristic OMAR Opportunistic Medium Access and Adaptive Rates telecommunications networking world. To support multimedia OSAR Opportunistic Scheduling and Auto Rate and other interactive/high performance applications, there is a PCF Point Coordination Function need to support QoS features through QoS provisioning that PIFS PCF Interframe Spacing PHB Per-Hop Behaviour provides resource assurance along with service differentiation. PSTN Public Switched Telephone Network Various techniques have been developed to facilitate QoS QAM Quadrature Amplitude Modulation provisioning, including (i) congestion control, (ii) admission QoE Quality of Experience QoS Quality of Service control, and (iii) traffic shaping and engineering. RTS Request To Send In the remainder of this section, we study the problems SDN Software Defined Networking of resource allocation and service differentiation, and will SIFS Short Interframe Spacing SISO Single Input Single Output introduce the techniques of admission control, congestion STA (Wireless) Station control, scheduling, as well as traffic shaping and engineering SWN Software Defined Wireless Network that can be used to facilitate QoS provisioning. TDM Time Division Multiplexing TXOP Transmission Opportunity VoIP Voice over IP VM Virtual Memory A. Resource Allocation WFQ Weighted Fair Queuing Fundamentally, many QoS issues stem from the problem WLAN Wireless Local Area Networking WRR Weighted Round Robin of resource allocation. A computer network is composed WSN Wireless Sensor Network of various resources—such