Infrastructure dependent wireless multicast - the effect of spatial diversity and error correction

The use of multiple Access Points (APs) with one AP placed at the middle of a coverage area and the remaining placed at the edge may reduce the Packet Error Rate (PER) experienced by a group of multicast receivers. This paper shows that Spatial Diversity can augment the channel quality experienced especially by those nodes which are located farther from the Master AP, i.e. the AP at the middle, however this study also demonstrates the need for error correction scheme. The aim of this analysis is to propose a means of enhancing the infrastructure end of an IEEE 802.11n Wireless Local Area Network (WLAN), such that multicast data can be delivered reliably in order to guarantee that the received video has an adequate Peak Signal to Noise Ratio (PSNR), but with the constraint that the Medium Access Control (MAC) and the Physical (PHY) layer of the receivers are not modified, hence a legacy IEEE 802.11n node may join the multicast group and experience good Quality of Service.peer-reviewe

Robust wireless video multicast using distributed antennas-based IEEE 802.11n infrastructure

Wireless Video Multicast is prone to suffer from frequent packet losses, resulting from the fact that the IEEE 802.11 standard does not use any mechanisms such as Acknowledgements and retransmissions, to combat the errors that are common in the dynamic wireless medium. However this paper shows that the infrastructure can be adapted to reduce the wireless errors, by using spatial diversity and spatial expansion to combat the wireless medium's random nature. This is obtained by adding a number of antennas placed equidistantly at the edge of the coverage area, using the same total transmit power that would be used with one transmit antenna. Moreover, this paper shows that since the IEEE 802.11n, the standard which facilitates the use of multiple antennas, states that the maximum number of antennas at any transceiver is four, two Access Points can be used to transmit the same data packet in orthogonal time slots to transmit good quality H.264 video resulting in all nodes experiencing an average Peak Signal to Noise Ratio greater than 36dB for MCS-5 and MCS-6 for a coverage area having radius of 60m. Since only two time slots are used, these results are obtained with a ½ code rate which is an improvement to the code rate used in current cooperative schemes.peer-reviewe

Video QoS/QoE over IEEE802.11n/ac: A Contemporary Survey

The demand for video applications over wireless networks has tremendously increased, and IEEE 802.11 standards have provided higher support for video transmission. However, providing Quality of Service (QoS) and Quality of Experience (QoE) for video over WLAN is still a challenge due to the error sensitivity of compressed video and dynamic channels. This thesis presents a contemporary survey study on video QoS/QoE over WLAN issues and solutions. The objective of the study is to provide an overview of the issues by conducting a background study on the video codecs and their features and characteristics, followed by studying QoS and QoE support in IEEE 802.11 standards. Since IEEE 802.11n is the current standard that is mostly deployed worldwide and IEEE 802.11ac is the upcoming standard, this survey study aims to investigate the most recent video QoS/QoE solutions based on these two standards. The solutions are divided into two broad categories, academic solutions, and vendor solutions. Academic solutions are mostly based on three main layers, namely Application, Media Access Control (MAC) and Physical (PHY) which are further divided into two major categories, single-layer solutions, and cross-layer solutions. Single-layer solutions are those which focus on a single layer to enhance the video transmission performance over WLAN. Cross-layer solutions involve two or more layers to provide a single QoS solution for video over WLAN. This thesis has also presented and technically analyzed QoS solutions by three popular vendors. This thesis concludes that single-layer solutions are not directly related to video QoS/QoE, and cross-layer solutions are performing better than single-layer solutions, but they are much more complicated and not easy to be implemented. Most vendors rely on their network infrastructure to provide QoS for multimedia applications. They have their techniques and mechanisms, but the concept of providing QoS/QoE for video is almost the same because they are using the same standards and rely on Wi-Fi Multimedia (WMM) to provide QoS

WiLiTV: A Low-Cost Wireless Framework for Live TV Services

With the evolution of HDTV and Ultra HDTV, the bandwidth requirement for IP-based TV content is rapidly increasing. Consumers demand uninterrupted service with a high Quality of Experience (QoE). Service providers are constantly trying to differentiate themselves by innovating new ways of distributing content more efficiently with lower cost and higher penetration. In this work, we propose a cost-efficient wireless framework (WiLiTV) for delivering live TV services, consisting of a mix of wireless access technologies (e.g. Satellite, WiFi and LTE overlay links). In the proposed architecture, live TV content is injected into the network at a few residential locations using satellite dishes. The content is then further distributed to other homes using a house-to-house WiFi network or via an overlay LTE network. Our problem is to construct an optimal TV distribution network with the minimum number of satellite injection points, while preserving the highest QoE, for different neighborhood densities. We evaluate the framework using realistic time-varying demand patterns and a diverse set of home location data. Our study demonstrates that the architecture requires 75 - 90% fewer satellite injection points, compared to traditional architectures. Furthermore, we show that most cost savings can be obtained using simple and practical relay routing solutions

Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Wi-Fi Enabled Healthcare

Focusing on its recent proliferation in hospital systems, Wi-Fi Enabled Healthcare explains how Wi-Fi is transforming clinical work flows and infusing new life into the types of mobile devices being implemented in hospitals. Drawing on first-hand experiences from one of the largest healthcare systems in the United States, it covers the key areas associated with wireless network design, security, and support. Reporting on cutting-edge developments and emerging standards in Wi-Fi technologies, the book explores security implications for each device type. It covers real-time location services and emerging trends in cloud-based wireless architecture. It also outlines several options and design consideration for employee wireless coverage, voice over wireless (including smart phones), mobile medical devices, and wireless guest services. This book presents authoritative insight into the challenges that exist in adding Wi-Fi within a healthcare setting. It explores several solutions in each space along with design considerations and pros and cons. It also supplies an in-depth look at voice over wireless, mobile medical devices, and wireless guest services. The authors provide readers with the technical knowhow required to ensure their systems provide the reliable, end-to-end communications necessary to surmount today’s challenges and capitalize on new opportunities. The shared experience and lessons learned provide essential guidance for large and small healthcare organizations in the United States and around the world. This book is an ideal reference for network design engineers and high-level hospital executives that are thinking about adding or improving upon Wi-Fi in their hospitals or hospital systems

Reliable Multicast transport of the video over the WiFi network

Le transport multicast est une solution efficace pour envoyer le même contenu à plusieurs récepteurs en même temps. Ce mode est principalement utilisé pour fournir des flux multimédia en temps réel. Cependant, le multicast classique de l IEEE 802.11 n'utilise aucun mécanisme d acquittement. Ainsi, l échec de réception implique la perte définitive du paquet. Cela limite la fiabilité du transport multicast et impact la qualité des applications vidéo. Pour résoudre ce problème, 802.11v et 802.11aa sont définis récemment. Le premier amendement propose Direct Multicast Service (DMS). D'autre part, le 802.11aa introduit GroupCast with Retries (GCR). GCR définit deux nouvelles politiques de retransmission : Block Ack (BACK) et Unsolicited Retry (UR).Dans cette thèse, nous évaluons et comparons les performances de 802.11v/aa. Nos résultats montrent que tous les nouveaux protocoles multicast génèrent un overhead de transmission important. En outre, DMS a une scalabilité très limitée, et GCR-BACK n'est pas approprié pour des grands groupes multicast. D autre part, nous montrons que DMS et GCR-BACK génèrent des latences de transmission importantes lorsque le nombre de récepteurs augmente. Par ailleurs, nous étudions les facteurs de pertes dans les réseaux sans fil. Nous montrons que l'indisponibilité du récepteur peut être la cause principale des pertes importantes et de leur nature en rafales. En particulier, nos résultats montrent que la surcharge du processeur peut provoquer un taux de perte de 100%, et que le pourcentage de livraison peut être limité à 35% lorsque la carte 802.11 est en mode d économie d'énergie.Pour éviter les collisions et améliorer la fiabilité du transport multicast, nous définissons le mécanisme Busy Symbol (BS). Nos résultats montrent que BS évite les collisions et assure un taux de succès de transmission très important. Afin d'améliorer davantage la fiabilité du trafic multicast, nous définissons un nouveau protocole multicast, appelé Block Negative Acknowledgement (BNAK). Ce protocole opère comme suit. L AP envoi un bloc de paquets suivi par un Block NAK Request (BNR). Le BNR permet aux membres de détecter les données manquantes et d envoyer une demande de retransmission, c.à.d. un Block NAK Response (BNAK). Un BNAK est transmis en utilisant la procédure classique d accès au canal afin d'éviter toute collision avec d'autres paquets. En plus, cette demande est acquittée. Sous l'hypothèse que 1) le récepteur est situé dans la zone de couverture du débit de transmission utilisé, 2) les collisions sont évitées et 3) le terminal a la bonne configuration, très peu de demandes de retransmission sont envoyées, et la bande passante est préservée. Nos résultats montrent que BNAK a une très grande scalabilité et génère des délais très limités. En outre, nous définissons un algorithme d'adaptation de débit pour BNAK. Nous montrons que le bon débit de transmission est sélectionné moyennant un overhead très réduit de moins de 1%. En plus, la conception de notre protocole supporte la diffusion scalable de lavvidéo. Cette caractéristique vise à résoudre la problématique de la fluctuation de la bande passante, et à prendre en considération l'hétérogénéité des récepteurs dans un réseau sans fil.The multicast transport is an efficient solution to deliver the same content to many receivers at the same time. This mode is mainly used to deliver real-time video streams. However, the conventional multicast transmissions of IEEE 802.11 do not use any feedback policy. Therefore missing packets are definitely lost. This limits the reliability of the multicast transport and impacts the quality of the video applications. To resolve this issue, the IEEE 802.11v/aa amendments have been defined recently. The former proposes the Direct Multicast Service (DMS). On the other hand, 802.11aa introduces Groupcast with Retries (GCR) service. GCR defines two retry policies: Block Ack (BACK) and Unsolicited Retry (UR).In this thesis we evaluate and compare the performance of 802.11v/aa. Our simulation results show that all the defined policies incur an important overhead. Besides, DMS has a very limited scalability, and GCR-BACK is not appropriate for large multicast groups. We show that both DMS and GCR-BACK incur important transmission latencies when the number of the multicast receivers increases. Furthermore, we investigate the loss factors in wireless networks. We show that the device unavailability may be the principal cause of the important packet losses and their bursty nature. Particularly, our results show that the CPU overload may incur a loss rate of 100%, and that the delivery ratio may be limited to 35% when the device is in the power save mode.To avoid the collisions and to enhance the reliability of the multicast transmissions, we define the Busy Symbol (BS) mechanism. Our results show that BS prevents all the collisions and ensures a very high delivery ratio for the multicast packets. To further enhance the reliability of this traffic, we define the Block Negative Acknowledgement (BNAK) retry policy. Using our protocol, the AP transmits a block of multicast packets followed by a Block NAK Request (BNR). Upon reception of a BNR, a multicast member generates a Block NAK Response (BNAK) only if it missed some packets. A BNAK is transmitted after channel contention in order to avoid any eventual collision with other feedbacks, and is acknowledged. Under the assumption that 1) the receiver is located within the coverage area of the used data rate, 2) the collisions are avoided and 3) the terminal has the required configuration, few feedbacks are generated and the bandwidth is saved. Our results show that BNAK has a very high scalability and incurs very low delays. Furthermore, we define a rate adaptation scheme for BNAK. We show that the appropriate rate is selected on the expense of a very limited overhead of less than 1%. Besides, the conception of our protocol is defined to support the scalable video streaming. This capability intends to resolve the bandwidth fluctuation issue and to consider the device heterogeneity of the group members.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Interoperability of wireless communication technologies in hybrid networks: Evaluation of end-to-end interoperability issues and quality of service requirements

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication “anywhere, any time with anyone”. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues. The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies). The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks. Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications. The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way. The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools. This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks. Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research. It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites. The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation

무선랜 비디오 멀티캐스트의 문제 발견 및 성능 향상 기법

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 최성현.Video multicast, streaming real-time videos via multicast, over wireless local area network (WLAN) has been considered a promising solution to share common venue-specific videos. By virtue of the nature of the wireless broadcast medium, video multicast basically enables scale-free video delivery, i.e., it can deliver a common video with the fixed amount of wireless resource regardless of the number of receivers. However, video multicast has not been widely enjoyed in our lives due to three major challenges: (1) power saving-related problem, (2) low reliability and efficiency, and (3) limited coverage. In this dissertation, we consider three research topics, i.e., (1) identification of practical issues with multicast power saving, (2) physical (PHY) rate and forward erasure correction code (FEC) rate adaptation over a single-hop network, and (3) multi-hop multicast, which deal with the three major challenges, respectively. Firstly, video multicast needs to be reliably delivered to power-saving stations, given that many portable devices are battery-powered. Accordingly, we investigate the impact of multicast power saving, and address two practical issues related with the multicast power saving. From the measurement with several commercial WLAN devices, we observe that many devices are not standard compliant, thus making video multicast performance severely degraded. We categorize such standard incompliant malfunctions that can result in significant packet losses. We also figure out a coexistence problem between video multicast and voice over Internet protocol (VoIP) when video receivers runs in power saving mode (PSM). The standard-compliant power save delivery of multicast deteriorates the VoIP performance in the same WLAN. We analyze the VoIP packet losses due to the coexistence problem, and propose a new power save delivery scheme to resolve the problem. We further implement the proposed scheme with an open source device driver, and our measurement results demonstrate that the proposed scheme significantly enhances the VoIP performance without sacrificing the video multicast performance. Second, multi-PHY rate FEC-applied wireless multicast enables reliable and efficient video multicast with intelligent selection of PHY rate and FEC rate. The optimal PHY/FEC rates depend on the cause of the packet losses. However, previous approaches select the PHY/FEC rates by considering only channel errors even when interference is also a major source of packet losses.We propose InFRA, an interference-aware PHY/FEC rate adaptation framework that (1) infers the cause of the packet losses based on received signal strength indicator (RSSI) and cyclic redundancy check (CRC) error notifications, and (2) determines the PHY/FEC rates based on the cause of packet losses. Our prototype implementation with off-the-shelf chipsets demonstrates that InFRA enhances the multicast delivery under various network scenarios. InFRA enables 2.3x and 1.8x more nodes to achieve a target video packet loss rate with a contention interferer and a hidden interferer, respectively, compared with the state-of-theart PHY/FEC rate adaptation scheme. To the best of our knowledge, InFRA is the first work to take the impact of interference into account for the PHY/FEC rate adaptation. Finally, collaborative relaying that enables selected receiver nodes to relay the received packets from source node to other nodes enhances service coverage, reliability, and efficiency of video multicast. The intelligent selection of sender nodes (source and relays) and their transmission parameters (PHY rate and the number of packets to send) is the key to optimize the performance. We propose EV-CAST, an interference and energy-aware video multicast system using collaborative relays, which entails online network management based on interference-aware link characterization, an algorithm for joint determination of sender nodes and transmission parameters, and polling-based relay protocol. In order to select most appropriate set of the relay nodes, EV-CAST considers interference, battery status, and spatial reuse, as well as other factors accumulated over last decades. Our prototype-based measurement results demonstrate that EV-CAST outperforms the state-of-the-art video multicast schemes. In summary, from Chapter 2 to Chapter 4, the aforementioned three pieces of the research work, i.e., identification of power saving-related practical issues, InFRA for interference-resilient single-hop multicast, and EV-CAST for efficient multi-hop multicast, will be presented, respectively.1 Introduction 1 1.1 Video Multicast over WLAN 1 1.2 Overview of Existing Approaches 4 1.2.1 Multicast Power Saving 4 1.2.2 Reliability and Efficiency Enhancement 4 1.2.3 Coverage Extension 5 1.3 Main Contributions 7 1.3.1 Practical Issues with Multicast Power Saving 7 1.3.2 Interference-aware PHY/FEC Rate Adaptation 8 1.3.3 Energy-aware Multi-hop Multicast 9 1.4 Organization of the Dissertation 10 2 Practical Issues with Multicast Power Saving 12 2.1 Introduction 12 2.2 Multicast & Power Management Operation in IEEE 802.11 14 2.3 Inter-operability Issue 15 2.3.1 Malfunctions of Commercial WLAN Devices 17 2.3.2 Performance Evaluation 20 2.4 Coexistence Problem of Video Multicast and VoIP 21 2.4.1 Problem Statement 21 2.4.2 Problem Identification: A Measurement Study 23 2.4.3 Packet Loss Analysis 27 2.4.4 Proposed Scheme 32 2.4.5 Performance Evaluation 33 2.5 Summary 37 3 InFRA: Interference-Aware PHY/FEC Rate Adaptation for Video Multicast over WLAN 39 3.1 Introduction 39 3.2 Related Work 42 3.2.1 Reliable Multicast Protocol 42 3.2.2 PHY/FEC rate adaptation for multicast service 44 3.2.3 Wireless Video Transmission 45 3.2.4 Wireless Loss Differentiation 46 3.3 Impact of Interference on Multi-rate FEC-applied Multicast 46 3.3.1 Measurement Setup 47 3.3.2 Measurement Results 47 3.4 InFRA: Interference-aware PHY/FEC Rate Adaptation Framework 49 3.4.1 Network Model and Objective 49 3.4.2 Overall Architecture 50 3.4.3 FEC Scheme 52 3.4.4 STA-side Operation 53 3.4.5 AP-side Operation 61 3.4.6 Practical Issues 62 3.5 Performance Evaluation 65 3.5.1 Measurement Setup 66 3.5.2 Small Scale Evaluation 67 3.5.3 Large Scale Evaluation 70 3.6 Summary 74 4 EV-CAST: Interference and Energy-aware Video Multicast Exploiting Collaborative Relays 75 4.1 Introduction 75 4.2 Factors for Sender Node and Transmission Parameter Selection 78 4.3 EV-CAST: Interference and Energy-aware Multicast Exploiting Collaborative Relays 80 4.3.1 Network Model and Objective 80 4.3.2 Overview 81 4.3.3 Network Management 81 4.3.4 Interference and Energy-aware Sender Nodes and Transmission Parameter Selection (INFER) Algorithm 87 4.3.5 Assignment, Polling, and Re-selection of Relays 93 4.3.6 Discussion 95 4.4 Evaluation 96 4.4.1 Measurement Setup 96 4.4.2 Micro-benchmark 98 4.4.3 Macro-benchmark 103 4.5 Related Work 105 4.5.1 Multicast Opportunistic Routing 105 4.5.2 Multicast over WLAN 106 4.6 Summary 106 5 Conclusion 108 5.1 Research Contributions 108 5.2 Future Research Directions 109 Abstract (In Korean) 121Docto