Delay-Reliability Trade-off in MIMO-Enabled IEEE 802.11-Based Wireless Sensor and Actuator Networks

AbstractOne of the main challenges in Wireless Sensor and Actuator Networks (WSAN) is the delay caused by shared and nondeterministic behavior of wireless communication medium. The Retry-Limit parameter of IEEE 802.11 standard can be used to control packet reliability, whereas other parameters mostly effect on the packet delay. In this paper, at first the delay-reliability trade-off in WSANs based on MIMO-Enabled IEEE 802.11 standard, utilizing Enhanced Distributed Channel Access (EDCA) at Medium Access Control (MAC) layer and Maximum Likelihood Spatial Multiplexing at PHYsical (PHY) Layer is studied. Then two simple adaptive schemes have been proposed to minimize packet delay while satisfying the required reliability at noisy factory environment

Video streaming over 802.11 wlan with content-aware adaptive retry

10.1109/ICME.2005.1521525IEEE International Conference on Multimedia and Expo, ICME 20052005723-72

Video streaming over 802.11 WLAN with content-aware adaptive retry

Robust video streaming over error-prone wireless LANs (WLANs) poses many challenges. In this paper, we propose a timestamp-based content-aware adaptive retry (CAR) mechanism for MPEG video streaming over 802.11 WLANs, where the MAC dynamically determines whether to send or discard a packet based on its retransmission deadline. The retransmission deadline is assigned to each packet according to its temporal relationship and error propagation characteristics with respect to other video packets in the same GOP. The proposed scheme avoids late packets by eliminating the impact of random backoff deference and co-channel interference with proper initial delay introduced at the receiver. Simulation results show CAR significantly improves video quality and saves channel bandwidth. 1

The application of network coding to multicast routing in wireless networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 58-62).This thesis considers the application of network coding and opportunistic routing to improve the performance of multicast flows in wireless networks. Network coding allows routers to randomly mix packets before forwarding them. This randomness ensures that routers that hear the same transmission are unlikely to forward the same packets, which permits routers to exploit wireless opportunism with minimal coordination. By mixing packets, network coding is able to reduce the number of transmissions necessary to convey packets to multiple receivers, which can lead to a large increase in throughput for multicast traffic. We discuss the design of a multicast enabled variant of MORE, a network coding based protocol for file transfer in wireless mesh networks, and evaluate this extension, which we call MORE-M, in a 20-node indoor wireless testbed. We compare MORE-M to a wireless multicast protocol that takes an approach similar to that of wired multicast by using the ETX metric to build unicast routing trees. We also compare MORE-M to a multicast enabled variant of the ExOR routing protocol. Experiments show that MORE-M's gains increase with the number of destinations, and are 35-200% greater than that of ExOR. We then consider the problem of video streaming in a wireless local area network for applications such as video conferencing. A network coding based protocol that uses opportunistic receptions at clients is proposed. We evaluate the design in our testbed and demonstrate that the use of network coding and, in particular, the use of wireless opportunism increase the quality of the video stream.by Michael Jennings.S.M

Greediness control algorithm for multimedia streaming in wireless local area networks

This work investigates the interaction between the application and transport layers while streaming multimedia in a residential Wireless Local Area Network (WLAN). Inconsistencies have been identified that can have a severe impact on the Quality of Experience (QoE) experienced by end users. This problem arises as a result of the streaming processes reliance on rate adaptation engines based on congestion avoidance mechanisms, that try to obtain as much bandwidth as possible from the limited network resources. These upper transport layer mechanisms have no knowledge of the media which they are carrying and as a result treat all traffic equally. This lack of knowledge of the media carried and the characteristics of the target devices results in fair bandwidth distribution at the transport layer but creates unfairness at the application layer. This unfairness mostly affects user perceived quality when streaming high quality multimedia. Essentially, bandwidth that is distributed fairly between competing video streams at the transport layer results in unfair application layer video quality distribution. Therefore, there is a need to allow application layer streaming solutions, tune the aggressiveness of transport layer congestion control mechanisms, in order to create application layer QoE fairness between competing media streams, by taking their device characteristics into account. This thesis proposes the Greediness Control Algorithm (GCA), an upper transport layer mechanism that eliminates quality inconsistencies caused by rate / congestion control mechanisms while streaming multimedia in wireless networks. GCA extends an existing solution (i.e. TCP Friendly Rate Control (TFRC)) by introducing two parameters that allow the streaming application to tune the aggressiveness of the rate estimation and as a result, introduce fair distribution of quality at the application layer. The thesis shows that this rate adaptation technique, combined with a scalable video format allows increased overall system QoE. Extensive simulation analysis demonstrate that this form of rate adaptation increases the overall user QoE achieved via a number of devices operating within the same home WLAN

Adaptive multimedia streaming control algorithm in wireless LANs and 4G networks

E-learning has become an important service offered over the Internet. Lately many users are accessing learning content via wireless networks and using mobile devices. Most content is rich media-based and often puts significant pressure on the existing wireless networks in order to support high quality of delivery. In this context, offering a solution for improving user quality of experience when multimedia content is delivered over wireless networks is already a challenging task. Additionally, to support this for mobile e-learning over wireless LANs becomes even more difficult. If we want to increase the end-used perceived quality, we have to take into account the users’ individual set of characteristics. The fact that users have subjective opinions on the quality of a multimedia application can be used to increase their QoE by setting a minimum quality threshold below which the connection is considered to be undesired. Like this, the use of precious radio resources can be optimized in order to simultaneously satisfy an increased number of users. In this thesis a new user-oriented adaptive algorithm based on QOAS was designed and developed in order to address the user satisfaction problem. Simulations have been carried out with different adaptation schemes to compare the performances and benefits of the DQOAS mechanism. The simulation results are showing that using a dynamic stream granularity with a minimum threshold for the transmission rate, improves the overall quality of the multimedia delivery process, increasing the total number of satisfied users and the link utilization The good results obtained by the algorithm in IEEE 802.11 wireless environment, motivated the research about the utility of the newly proposed algorithm in another wireless environment, LTE. The study shows that DQOAS algorithm can obtain good results in terms of application perceived quality, when the considered application generates multiple streams. These results can be improved by using a new QoS parameters mapping scheme able to modify the streams’ priority and thus allowing the algorithms decisions to not be overridden by the systems’ scheduler

Temporal Video Transcoding in Mobile Systems

La tesi analizza il problema della transcodifica temporale per la trasmissione del video in tempo reale su reti mobili. Viene proposta un’architettura di transcodifica temporale e un nuovo algoritmo di ricalcolo dei vettori di moto per il transcoder temporale H.264. Per fronteggiare il problema della riduzione costante della banda del canale wireless nelle reti infrastrutturate, vengono proposte diverse politiche di frame skipping basate sul dimensionamento del buffer del transcoder per garantire una comunicazione in tempo reale. Il moto di un frame e il numero di frames consecutivi scartati vengono inoltre considerati per migliorare la qualità del video transcodificato. E’ stato inoltre proposto e studiato un sistema di trasmissione video per reti veicolari con protocollo IEEE 802.11, basato su transcodifica temporale. Questo sistema permette di scartare quei frames il cui tempo di trasmissione supera un massimo ritardo ammisssibile al di sopra del quale tali frames non verrebbero comunque visualizzati. Il sistema proposto permette un notevole risparmio di banda e migliora la qualità del video evitando che molti frames consecutivi vengano scartati a causa della congestione