Layered Wireless Video Multicast Using Relays

2013

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.

2009 IEEE Wireless Communications and Networking Conference, 2009

Wireless video multicast enables delivery of popular events to many wireless users in a bandwidth efficient manner. However, providing good and stable video quality to a large number of users with varying channel conditions remains elusive. In our previous work, we integrated layered video coding with cooperative communication to enable efficient and robust video multicast in infrastructure-based wireless networks [1]. Through simulation and analysis, we showed that cooperative multicast improves the multicast system performance and the coverage area. In this work, we integrate the proposed system with packet level Forward Error Correction (FEC) and evaluate the viability of the system in a realistic environment. We implement the system at the MAC layer and report the experimental results in a medium size (i.e., 8 stations) testbed. The experimental results confirm that the new cooperative MAC protocol for multicast, delivers superior performance.

IEEE Transactions on Multimedia, 2000

With the increased popularity of mobile multimedia services, efficient and robust video multicast strategies are of critical importance. In a conventional multicast system, the source station transmits at the base rate of the underlying network so that all the nodes can receive the data correctly. The performance of such a multicast system is limited by the node with the worst channel conditions, which usually corresponds to the nodes at the edge of the multicast coverage range. To overcome this problem, we propose a two-hop cooperative transmission scheme where in the first hop the source station transmits the packets and the nodes who receive the packets forward the packets simultaneously in the second hop using Randomized Distributed Space Time Codes (R-DSTC). We further integrate this randomized cooperative transmission with layered video coding to provide users different video quality based on their channel conditions. The performance of the system is evaluated and compared with a conventional multicast system. Our results show that the proposed cooperative system significantly improves the performance compared to conventional multicast.

2010 IEEE International Conference on Acoustics, Speech and Signal Processing, 2010

Recently, much progress has been made on the cross-layer optimization of video streams in multiple access networks. The key idea is to use the granular data structure of compressed video to trade quality with bits, and optimally prioritize transmissions given the available bandwidth, in order to obtain proportionally optimal video quality across video streams. Herein, we discuss the effect and potential benefit of using a cooperative-relay strategy in a wireless network, where proportionally optimal video schedules are computed via a multi-user Markov decision process. The idea is that feeble signals of nodes that are located far away from the destination can be enhanced via the cooperation of intermediate nodes, acting as cooperative relays. Our contribution is to indicate a possible solution that would require relatively modest changes to the multi-user optimization framework, while warranting a uniformly better experience to the video users thanks to cooperative coding.

IEEE Journal on Selected Areas in Communications, 2000

We investigate the impact of cooperative relaying on uplink and downlink multi-user (MU) wireless video transmission. The objective is to maximize the long-term sum of utilities across the video terminals in a decentralized fashion, by jointly optimizing the packet scheduling, the resource allocation, and the cooperation decisions, under the assumption that some nodes are willing to act as cooperative relays. A pricing-based distributed resource allocation framework is adopted, where the price reflects the expected future congestion in the network. Specifically, we formulate the wireless video transmission problem as an MU Markov decision process (MDP) that explicitly considers the cooperation at the physical layer and the medium access control sublayer, the video users' heterogeneous traffic characteristics, the dynamically varying network conditions, and the coupling among the users' transmission strategies across time due to the shared wireless resource. Although MDPs notoriously suffer from the curse of dimensionality, our study shows that, with appropriate simplications and approximations, the complexity of the MU-MDP can be significantly mitigated. Our simulation results demonstrate that integrating cooperative decisions into the MU-MDP optimization increases the resource price in congested networks and decreases the price in uncongested ones. Additionally, our results show that cooperation allows users with feeble direct signals to achieve improvements in video quality on the order of 5 − 10 dB peak signal-to-noise ratio, with less than 0.8 dB quality loss by users with strong direct signals.

Proceedings of the 6th ACM workshop on Wireless multimedia networking and computing - WMuNeP '11, 2011

Advancements in video coding, compact media display, and communication devices, particularly in emerging broadband wireless access networks, have created many foreseeable and exciting applications of video broadcast/multicast over the wireless medium. For efficient and robust wireless video broadcast/multicast under fading, this thesis presents and examines a novel crosslayer framework that exploits the interplay between applying protections on a successively refinable video source and transmitting through a layered broadcast/multicast channel. The framework is realistically achieved and evaluated by using multiple description coding (MDC) on a scalable video source and using superposition coding (SPC) for layered broadcast/multicast transmissions. An analytical model using the total received/recovered video bitstreams from each coded wireless broadcast/multicast signal is developed, which serves as a metric of video quality for the system analysis and optimization. An efficient methodology has demonstrated that optimal power allocations and modulation selections can be practically determined to improve the broadcast/multicast video quality. From the information-theoretical perspective, a general closedform formula is derived for the end-to-end distortion analysis of the proposed framework, which is applicable to any (n, k) protection code applied on a successive refinable source with a Gaussian distribution over layered Gaussian broadcast channels. The results reveal the scenarios for the proposed framework to lead to a lower distortion than a legacy system without any protection. By analyzing the characteristics of the closed-form formula, an efficient O(n log n) algorithm is developed to determine optimal k values in the (n, k) protection codes that minimize the distortion under the framework. Finally, a cross-layer design of logical SPC modulation is introduced to achieve layered broadcast/multicast for scalable video. It serves as an alternative for practically implementing the proposed framework of coded wireless video broadcast/multicast, if the iv hardware-based SPC component is not available in a wireless system. In summary, the thesis presents comprehensive analyses, simulations, and experiments to understand, investigate, and justify the effectiveness of the proposed cross-layer framework of coded wireless video broadcast/multicast. More importantly, this thesis contributes to the advancement in the related fields of communication engineering and information theory by introducing a new design dimension in terms of protection. This is unique when compared to previously-reported layered approaches that are often manipulating conventional parameters alone such as power and modulation scheme. The impact of this dimension was unapparent in the past, but is now proven as an effective means to enable high-quality, efficient, and robust wireless video broadcast/multicast for promising media applications. v Over the years while commencing my studies at the University of Waterloo, many of my lifelong lessons were learned through exceptional individuals who have made distinctive influences on me, in both subtle and unsubtle ways. First, I express my deepest gratitude to my supervisor, Professor Pin-Han Ho, for supporting me over the years with endless generosity, for giving me so much freedom and open-minded guidance to explore and discover exciting research ideas, and for cultivating me to become an independent researcher and lifelong learner with his inspiring encouragement. I also present a special appreciation to my Ph.D. exam committee member, Professor En-hui Yang, for helping me to build a solid background and cultivate creative thinking for new areas of research, for sharing generous and stimulating discussions with me, and for being my role-model of a passionate teacher and persistent researcher with wide-range of wisdoms. My appreciation extends to Professor Liang-Liang Xie, who has been resourceful to me with his valuable advices to my research, and charismatic to me with his teaching style as one of my best learning experiences in his class at Waterloo. I would like to thank Professor Johnny Wong as my external committee and Professor Danny H.K. Tsang as my lifelong mentor, who opened my eyes and minds through the journey of my Ph.D. study. I would also like to deeply thank Professor Xiaohong Jiang to serve as my external committee with his generous time and support. I lovingly extend my gratitude to Dr. Flora Li for her adoring support and care during final stages of this work. I would like to thank Xiang Yu and James Ho, who have been my wonderful friends and research collaborators. There were many impactful and enjoyable moments in the discussions with them that inspire me endlessly for my research ideas. I would also like to thank many friends and colleagues at Waterloo, with whom I have had the pleasure to work with over the vi years. These include Fen Hou, Jing-qing Mei, Gary Yeung and all the helpful individuals such as

IEEE Transactions on Multimedia, 2015

In this paper, a cooperative multicast scheme that uses Randomized Distributed Space Time Codes (R-DSTC), along with packet level Forward Error Correction (FEC), is studied. Instead of sending source packets and/or parity packets through two hops using R-DSTC as proposed in our prior work, the new scheme delivers both source packets and parity packets using only one hop. After the source station (access point, AP) first sends all the source packets, the AP as well as all nodes that have received all source packets together send the parity packets using R-DSTC. As more parity packets are transmitted, more nodes can recover all source packets and join the parity packet transmission. The process continues until all nodes acknowledge the receipt of enough packets for recovering the source packets. For each given node distribution, the optimum transmission rates for source and parity packets are determined such that the video rate that can be sustained at all nodes is maximized. This new scheme can support significantly higher video rates, and correspondingly higher PSNR of decoded video, than the prior approaches. Three suboptimal approaches, which do not require full information about user distribution or the feedback, and hence are more feasible in practice are also presented. The proposed suboptimal scheme with only the node count information and without feedback still outperforms our prior approach that assumes full channel information and no feedback.

2011 31st International Conference on Distributed Computing Systems, 2011

A primary challenge in multicasting video in a wireless LAN to multiple clients is to deal with the client diversity -clients may have different channel characteristics and hence receive different numbers of transmissions from the AP. A promising approach to overcome this problem is to combine multi-resolution (layered) video coding with interlayer network coding. The fundamental challenge in such an approach is to determine the strategy of coding the packets across different layers that maximizes the number of decoded layers at all clients. This paper makes three contributions.

Wireless Communications and Mobile Computing, 2007

Exploiting directional antenna technology in wireless networks has become an attractive option because of the potential capacity increase through spatial reuse. Such development apparently has profound impact to wireless multimedia applications. While the advantages of directional transmission in single hop networks (e.g. WLANs and cellular systems) have been evident, it has also been recognized that multi hop directional networks may suffer long transmission delays and frequent link breakages if conventional routing protocols (e.g. AODV and DSR) are used. This is mainly due to the unique feature of directional transmission commonly known as "node deafness". To address this problem, we propose a multi-path routing scheme which focuses more on minimizing per-hop delays instead of traditional route length. We further propose a differentiated service (DiffServ) framework for layered video transport over multi hop directional network using QoS aware multi-path routing as well as class based queuing (CBQ). Both network layer and application layer simulation results are presented to demonstrate the effectiveness of the proposed video transport scheme over directional networks.

Limited bandwidth and high packet loss rate pose a serious challenge for video streaming applications over wireless networks. Even when packet loss is not present, the bandwidth fluctuation as a result of an arbitrary number of active flows in an IEEE 802.11 network, can significantly degrade the video quality. This paper aims to enhance the quality of video streaming applications in wireless home networks via a joint optimization of video coding technique, admission control algorithm, and Medium Access Control (MAC) protocol. Using an Aloha-like MAC protocol, we propose a novel admission control framework, which can be viewed as an optimization problem that maximizes the average quality of admitted videos, given a specified minimum video quality for each flow. We present some hardness results for the optimization problem under various conditions, and propose some heuristic algorithms for finding a good solution. In particular, we show that a simple greedy layer-allocation algorithm can perform reasonably well, although it is typically not optimal. Consequently, we present a more expensive heuristic algorithm that guarantees to approximate the optimal solution within a constant factor. Simulation results demonstrate that our proposed framework can improve the video quality up to 26% as compared to those of the existing approaches.