95 research outputs found
Multimedia Streaming through Wireless Networks
An overview of wireless networks, cross-layer optimization techniques, and advances in wireless LAN technologies is presented. This paper presents a scalable and adaptive system-level approach to wireless multimedia in the emerging, Proactive Enterprise computing environment. A Distributed Network Information Base with Service Agents at each node is proposed to enable network-wide, proactive adaptation with adaptive routing and end-to-end Quality of Service (QoS) management. The paper suggests that a combination of technological advancements in emerging wireless networks, node-level cross-layer optimizations, and the proposed distributed cross-node system-level architecture are all required to efficiently scale and adapt wireless multimedia in the current market
Enhancement of Adaptive Forward Error Correction Mechanism for Video Transmission Over Wireless Local Area Network
Video transmission over the wireless network faces many challenges. The most critical challenge is related to packet loss. To overcome the problem of packet loss,
Forward Error Correction is used by adding extra packets known as redundant packet or parity packet. Currently, FEC mechanisms have been adopted together with Automatic Repeat reQuest (ARQ) mechanism to overcome packet losses and avoid network congestion in various wireless network conditions. The number of FEC packets need to be generated effectively because wireless network usually has varying network conditions. In the current Adaptive FEC mechanism, the FEC packets are decided by the average queue length and average packet retransmission times. The Adaptive FEC mechanisms have been proposed to suit the network condition by generating FEC packets adaptively in the wireless network. However, the current Adaptive FEC mechanism has some major drawbacks such as the reduction of recovery performance which injects too many excessive FEC packets into the network. This is not flexible enough to adapt with varying wireless network condition. Therefore, the enhancement of Adaptive FEC mechanism (AFEC) known as Enhanced Adaptive FEC (EnAFEC) has been proposed. The aim is to improve recovery performance on the current Adaptive FEC mechanism by injecting FEC packets dynamically based on varying wireless network conditions. The EnAFEC mechanism is implemented in the simulation environment using Network Simulator 2 (NS-2). Performance evaluations are also carried out. The EnAFEC was tested with the random uniform error model. The results from experiments and performance analyses showed that EnAFEC mechanism outperformed the other Adaptive FEC mechanism in terms of recovery efficiency. Based on the findings, the optimal amount of FEC generated by EnAFEC mechanism can recover high packet loss and produce good video quality
Reliable Multicast transport of the video over the WiFi network
Le transport multicast est une solution efficace pour envoyer le mĂȘme contenu Ă plusieurs rĂ©cepteurs en mĂȘme temps. Ce mode est principalement utilisĂ© pour fournir des flux multimĂ©dia en temps rĂ©el. Cependant, le multicast classique de l IEEE 802.11 n'utilise aucun mĂ©canisme d acquittement. Ainsi, l Ă©chec de rĂ©ception implique la perte dĂ©finitive du paquet. Cela limite la fiabilitĂ© du transport multicast et impact la qualitĂ© des applications vidĂ©o. Pour rĂ©soudre ce problĂšme, 802.11v et 802.11aa sont dĂ©finis rĂ©cemment. Le premier amendement propose Direct Multicast Service (DMS). D'autre part, le 802.11aa introduit GroupCast with Retries (GCR). GCR dĂ©finit deux nouvelles politiques de retransmission : Block Ack (BACK) et Unsolicited Retry (UR).Dans cette thĂšse, nous Ă©valuons et comparons les performances de 802.11v/aa. Nos rĂ©sultats montrent que tous les nouveaux protocoles multicast gĂ©nĂšrent un overhead de transmission important. En outre, DMS a une scalabilitĂ© trĂšs limitĂ©e, et GCR-BACK n'est pas appropriĂ© pour des grands groupes multicast. D autre part, nous montrons que DMS et GCR-BACK gĂ©nĂšrent des latences de transmission importantes lorsque le nombre de rĂ©cepteurs augmente. Par ailleurs, nous Ă©tudions les facteurs de pertes dans les rĂ©seaux sans fil. Nous montrons que l'indisponibilitĂ© du rĂ©cepteur peut ĂȘtre la cause principale des pertes importantes et de leur nature en rafales. En particulier, nos rĂ©sultats montrent que la surcharge du processeur peut provoquer un taux de perte de 100%, et que le pourcentage de livraison peut ĂȘtre limitĂ© Ă 35% lorsque la carte 802.11 est en mode d Ă©conomie d'Ă©nergie.Pour Ă©viter les collisions et amĂ©liorer la fiabilitĂ© du transport multicast, nous dĂ©finissons le mĂ©canisme Busy Symbol (BS). Nos rĂ©sultats montrent que BS Ă©vite les collisions et assure un taux de succĂšs de transmission trĂšs important. Afin d'amĂ©liorer davantage la fiabilitĂ© du trafic multicast, nous dĂ©finissons un nouveau protocole multicast, appelĂ© Block Negative Acknowledgement (BNAK). Ce protocole opĂšre comme suit. L AP envoi un bloc de paquets suivi par un Block NAK Request (BNR). Le BNR permet aux membres de dĂ©tecter les donnĂ©es manquantes et d envoyer une demande de retransmission, c.Ă .d. un Block NAK Response (BNAK). Un BNAK est transmis en utilisant la procĂ©dure classique d accĂšs au canal afin d'Ă©viter toute collision avec d'autres paquets. En plus, cette demande est acquittĂ©e. Sous l'hypothĂšse que 1) le rĂ©cepteur est situĂ© dans la zone de couverture du dĂ©bit de transmission utilisĂ©, 2) les collisions sont Ă©vitĂ©es et 3) le terminal a la bonne configuration, trĂšs peu de demandes de retransmission sont envoyĂ©es, et la bande passante est prĂ©servĂ©e. Nos rĂ©sultats montrent que BNAK a une trĂšs grande scalabilitĂ© et gĂ©nĂšre des dĂ©lais trĂšs limitĂ©s. En outre, nous dĂ©finissons un algorithme d'adaptation de dĂ©bit pour BNAK. Nous montrons que le bon dĂ©bit de transmission est sĂ©lectionnĂ© moyennant un overhead trĂšs rĂ©duit de moins de 1%. En plus, la conception de notre protocole supporte la diffusion scalable de lavvidĂ©o. Cette caractĂ©ristique vise Ă rĂ©soudre la problĂ©matique de la fluctuation de la bande passante, et Ă prendre en considĂ©ration l'hĂ©tĂ©rogĂ©nĂ©itĂ© des rĂ©cepteurs dans un rĂ©seau 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
Secure Layered Transmission in Multicast Systems with Wireless Information and Power Transfer
This paper considers downlink multicast transmit beamforming for secure
layered transmission systems with wireless simultaneous information and power
transfer. We study the power allocation algorithm design for minimizing the
total transmit power in the presence of passive eavesdroppers and energy
harvesting receivers. The algorithm design is formulated as a non-convex
optimization problem. Our problem formulation promotes the dual use of energy
signals in providing secure communication and facilitating efficient energy
transfer. Besides, we take into account a minimum required power for energy
harvesting at the idle receivers and heterogeneous quality of service (QoS)
requirements for the multicast video receivers. In light of the intractability
of the problem, we reformulate the considered problem by replacing a non-convex
probabilistic constraint with a convex deterministic constraint. Then, a
semidefinite programming relaxation (SDR) approach is adopted to obtain an
upper solution for the reformulated problem. Subsequently, sufficient
conditions for the global optimal solution of the reformulated problem are
revealed. Furthermore, we propose two suboptimal power allocation schemes based
on the upper bound solution. Simulation results demonstrate the excellent
performance and significant transmit power savings achieved by the proposed
schemes compared to isotropic energy signal generation.Comment: 7 pages, 3 figures, accepted for presentation at the IEEE
International Conference on Communications (ICC), Sydney, Australia, 201
Framework for Content Distribution over Wireless LANs
Wireless LAN (also called as Wi-Fi) is dominantly considered as the most pervasive
technology for Intent access. Due to the low-cost of chipsets and support for high data
rates, Wi-Fi has become a universal solution for ever-increasing application space
which includes, video streaming, content delivery, emergency communication,
vehicular communication and Internet-of-Things (IoT).
Wireless LAN technology is defined by the IEEE 802.11 standard. The 802.11
standard has been amended several times over the last two decades, to incorporate the
requirement of future applications. The 802.11 based Wi-Fi networks are
infrastructure networks in which devices communicate through an access point.
However, in 2010, Wi-Fi Alliance has released a specification to standardize direct
communication in Wi-Fi networks. The technology is called Wi-Fi Direct. Wi-Fi
Direct after 9 years of its release is still used for very basic services (connectivity, file
transfer etc.), despite the potential to support a wide range of applications. The reason
behind the limited inception of Wi-Fi Direct is some inherent shortcomings that limit
its performance in dense networks. These include the issues related to topology
design, such as non-optimal group formation, Group Owner selection problem,
clustering in dense networks and coping with device mobility in dynamic networks. Furthermore, Wi-Fi networks also face challenges to meet the growing number of Wi
Fi users. The next generation of Wi-Fi networks is characterized as ultra-dense
networks where the topology changes frequently which directly affects the network
performance. The dynamic nature of such networks challenges the operators to design
and make optimum planifications.
In this dissertation, we propose solutions to the aforementioned problems. We
contributed to the existing Wi-Fi Direct technology by enhancing the group formation
process. The proposed group formation scheme is backwards-compatible and
incorporates role selection based on the device's capabilities to improve network
performance. Optimum clustering scheme using mixed integer programming is
proposed to design efficient topologies in fixed dense networks, which improves
network throughput and reduces packet loss ratio. A novel architecture using
Unmanned Aeriel Vehicles (UAVs) in Wi-Fi Direct networks is proposed for
dynamic networks. In ultra-dense, highly dynamic topologies, we propose cognitive
networks using machine-learning algorithms to predict the network changes ahead of
time and self-configuring the network
Mobile Ad hoc Networking: Imperatives and Challenges
Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, "ad-hoc" network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANET\u27s characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future
Recommended from our members
Design of interface selection protocols for multi-homed wireless networks
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University on 10 December 2010.The IEEE 802.11/802.16 standards conformant wireless communication stations have multi-homing transmission capability. To achieve greater communication efficiency, multi-homing capable stations use handover mechanism to select appropriate transmission channel according to variations in the channel quality. This thesis presents three internal-linked handover schemes, (1) Interface Selection Protocol (ISP), belonging to Wireless Local Area Network (WLAN)- Worldwide Interoperability for Microwave Access (WiMAX) environment (2) Fast Channel Scanning (FCS) and (3) Traffic Manager (TM), (2) and (3) belonging to WiMAX Environment. The proposed schemes in this thesis use a novel mechanism of providing a reliable communication route. This solution is based on a cross-layer communication framework, where the interface selection module uses various network related parameters from Medium Access Control (MAC) sub-layer/Physical Layer (PHY) across the protocol suite for decision making at the Network layer. The proposed solutions are highly responsive when compared with existing multi-homed schemes; responsiveness is one of the key factors in the design of such protocols. Selected route under these schemes is based on the most up to date link-layer information. Therefore, such a route is not only reliable in terms of route optimization but it also fulfils the application demands in terms of throughput and delay. Design of ISP protocol use probing frames during the route discovery process. The 802.11 mandates the use of different rates for data transmission frames. The ISP-metric can be incorporated into various routing aspects and its applicability is determined by the possibility of provision of MAC dependent parameters that are used to determine the best path metric values. In many cases, higher device density, interference and mobility cause variable medium access delays. It causes creation of âunreachable zonesâ, where destination is marked as unreachable. However, by use of the best path metric, the destination has been made reachable, anytime and anywhere, because of the intelligent use of the probing frames and interface selection algorithm implemented. The IEEE 802.16e introduces several MAC level queues for different access categories, maintaining service requirement within these queues; which imply that frames from a higher priority queue, i.e. video frames, are serviced more frequently than those belonging to lower priority queues. Such an enhancement at the MAC sub-layer introduces uneven queuing delays. Conventional routing protocols are unaware of such MAC specific constraints and as a result, these factors are not considered which result in channel performance degradation. To meet such challenges, the thesis presents FCS and TM schemes for WiMAX. For FCS, Its solution is to improve the mobile WiMAX handover and address the scanning latency. Since minimum scanning time is the most important issue in the handover process. This handover scheme aims to utilize the channel efficiently and apply such a procedure to reduce the time it takes to scan the neighboring access stations. TM uses MAC and physical layer (PHY) specific information in the interface metric and maintains a separate path to destination by applying an alternative interface operation. Simulation tests and comparisons with existing multi-homed protocols and handover schemes demonstrate the effectiveness of incorporating the medium dependent parameters. Moreover, show that suggested schemes, have shown better performance in terms of end-to-end delay and throughput, with efficiency up to 40% in specific test scenarios
A Study on the Usage of Cross-Layer Power Control and Forward Error Correction for Embedded Video Transmission over Wireless Links
Cross-layering is a design paradigm for overcoming the limitations deriving from the ISO/OSI layering principle, thus improving the performance of communications in specific scenarios, such as wireless multimedia communications. However, most available solutions are based on empirical considerations, and do not provide a theoretical background supporting such approaches. The paper aims at providing an analytical framework for the study of single-hop video delivery over a wireless link, enabling cross-layer interactions for performance optimization using power control and FEC and providing a useful tool to determine the potential gain deriving from the employment of such design paradigm. The analysis is performed using rate-distortion information of an embedded video bitstream jointly with a Lagrangian power minimization approach. Simulation results underline that cross-layering can provide relevant improvement in specific environments and that the proposed approach is able to capitalize on the advantage deriving from its deployment
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
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