Cross-Layer Architecture for Adaptive Video Multicast Streaming Over Multirate Wireless LANs

Multicast video streaming over multirate wireless LANs imposes strong demands on video codecs and the underlying network. It is not sufficient that only the video codec or only the underlying protocols adapt to changes in the wireless link quality. Research efforts should be applied in both and in a synchronized way. Cross layer design is a new paradigm that addresses this challenge by optimizing communication network architectures across traditional layer boundaries. This paper presents cross-layer architecture for adaptive video multicast streaming over multirate wireless LANs where layer-specific information is passed in both directions, top-down and bottom-up. The authors jointly consider three layers of the protocol stack: the application, data link and physical layers. The authors analyze the performance of the proposed architecture and extensively evaluate it via simulations. The results show that the real-time video quality of the overall system can be greatly improved by cross-layer signaling.     

A New Systematic Framework for Autonomous Cross-Layer Optimization

Cross-layer optimization solutions have been proposed in recent years to improve the performance of wireless users that operate in a time-varying, error-prone network environment. However, these solutions often rely on centralized cross-layer optimization solutions that violate the layered network architecture of the protocol stack by requiring layers to provide access to their internal protocol parameters to other layers. This paper presents a new systematic framework for cross-layer optimization, which allows each layer to make autonomous decisions to maximize the wireless user's utility by optimally determining what information should be exchanged among layers. Hence, this cross-layer framework preserves the current layered network architecture. Since the user interacts with the wireless environment at various layers of the protocol stack, the cross-layer optimization problem is solved in a layered fashion such that each layer adapts its own protocol parameters and exchanges information (messages) with other layers that cooperatively maximize the performance of the wireless user. Based on the proposed layered framework, we also design a message-exchange mechanism that determines the optimal cross-layer transmission strategies, given the user's experienced environment dynamics.     

Application-driven cross-layer optimization for video streaming over wireless networks

Mobile multimedia applications require networks that optimally allocate resources and adapt to dynamically changing environments. Cross-layer design (CLD) is a new paradigm that addresses this challenge by optimizing communication network architectures across traditional layer boundaries. In this article we discuss the relevant technical challenges of CLD and focus on application-driven CLD for video streaming over wireless networks. We propose a cross-layer optimization strategy that jointly optimizes the application layer, data link layer, and physical layer of the protocol stack using an application-oriented objective function in order to maximize user satisfaction. In our experiments we demonstrate the performance gain achievable with this approach. We also explore the trade-off between performance gain and additional computation and communication cost introduced by cross-layer optimization. Finally, we outline future research challenges in CLD.     

Cross-Layer Optimized Video Streaming Over Wireless Multihop Mesh Networks

The proliferation of wireless multihop communication infrastructures in office or residential environments depends on their ability to support a variety of emerging applications requiring real-time video transmission between stations located across the network. We propose an integrated cross-layer optimization algorithm aimed at maximizing the decoded video quality of delay-constrained streaming in a multihop wireless mesh network that supports quality-of-service. The key principle of our algorithm lays in the synergistic optimization of different control parameters at each node of the multihop network, across the protocol layers-application, network, medium access control, and physical layers, as well as end-to-end, across the various nodes. To drive this optimization, we assume an overlay network infrastructure, which is able to convey information on the conditions of each link. Various scenarios that perform the integrated optimization using different levels ("horizons") of information about the network status are examined. The differences between several optimization scenarios in terms of decoded video quality and required streaming complexity are quantified. Our results demonstrate the merits and the need for cross-layer optimization in order to provide an efficient solution for real-time video transmission using existing protocols and infrastructures. In addition, they provide important insights for future protocol and system design targeted at enhanced video streaming support across wireless mesh networks     

3D visual experience oriented cross-layer optimized scalable texture plus depth based 3D video streaming over wireless networks

3D video streaming over the mobile Internet generally incurs the inferior 3D visual experience due to the time-varying characteristics of wireless channel. The conventional video streaming optimization methods generally neglect the harmony among different networking protocol layers. This paper proposes a cross-layer optimized texture plus depth based scalable 3D video streaming method to improve the expected 3D visual experience of the user by systematically considering the application layer texture-video/depth/FEC bit-rate allocation, MAC layer multi-channel allocation, and physical layer modulation and channel coding scheme (MCS) selection. In the cross-layer optimization, a networking-related 3D visual experience model which fuses the overlapped retinal view visual quality and depth sensation with mimicking human vision system is established to predict the 3D visual experience under the specific parameter configurations of different protocol layers. The efficiency and effectiveness of the proposed cross-layer optimized 3D video streaming method has been validated by subjective and objective experimental results.     

Cross-layer architecture for scalable video transmission in wireless network

Multimedia applications such as video conference, digital video broadcasting (DVB), and streaming video and audio have been gaining popularity during last years and the trend has been to allocate these services more and more also on mobile users. The demand of quality of service (QoS) for multimedia raises huge challenges on the network design, not only concerning the physical bandwidth but also the protocol design and services. One of the goals for system design is to provide efficient solutions for adaptive multimedia transmission over different access networks in all-IP environment. The joint source and channel coding (JSCC/D) approach has already given promising results in optimizing multimedia transmission. However, in practice, arranging the required control mechanism and delivering the required side information through network and protocol stack have caused problems and quite often the impact of network has been neglected in studies. In this paper we propose efficient cross-layer communication methods and protocol architecture in order to transmit the control information and to optimize the multimedia transmission over wireless and wired IP networks. We also apply this architecture to the more specific case of streaming of scalable video streams. Scalable video coding has been an active research topic recently and it offers simple and flexible solutions for video transmission over heterogeneous networks to heterogeneous terminals. In addition it provides easy adaptation to varying transmission conditions. In this paper we illustrate how scalable video transmission can be improved with efficient use of the proposed cross-layer design, adaptation mechanisms and control information.     

Dissecting the performance of YouTube video streaming in mobile networks

Video streaming applications constitute a significant portion of the Internet traffic today, with mobile accounting for more than half of the online video views. The high share of video in the current Internet traffic mix has prompted many studies that examine video streaming through measurements. However, streaming performance depends on many different factors at different layers of the TCP/IP stack. For example, browser selection at the application layer or the choice of protocol in transport layer can have significant impact on the video performance. Furthermore, video performance heavily depends on the underlying network conditions (eg, network and link layers). For mobile networks, the conditions vary significantly, since each operator has a different deployment strategy and configuration. In this paper, we focus on YouTube and carry out a comprehensive study investigating the influence of different factors on streaming performance. Leveraging the Measuring Mobile Broadband Networks in Europe (MONROE) test bed that enables experimentation with 13 different network configurations in four countries, we collect more than 1800 measurement samples in operational mobile networks. With this campaign, our goal is to quantify the impact of parameters from different layers on YouTube's streaming quality of experience (QoE). More specifically, we analyze the role of the browser (eg, Firefox and Chrome), the impact of transport protocol (eg, TCP or QUIC), the influence of network bandwidth, and signal coverage on streaming QoE. Our analysis reveals that all these parameters need to be taken into account jointly for network management practices, in order to ensure a high end‐user experience.     

Combining the rate adaptation and quality adaptation schemes for wireless video streaming

Video streaming service over wireless networks is a challenging task because of the changes in the wireless channel conditions that can occur due to interference, fading, and station mobility. Moreover, the IEEE 802.11 WLAN standard does not contain any specifications for the rate adaptation scheme which are useful for improving the wireless link utilization. To provide efficient wireless video streaming service, the rate adaptation scheme should be applied at the low layer and the quality adaptation scheme should be considered at the high layer. To meet this requirement of wireless video streaming, we propose a new cross-layer design for video streaming over wireless networks. This design includes the rate adaptation scheme in the data link and physical layers and the quality adaptation scheme in the application layer. The rate adaptation scheme adjusts the data transmission rate based on the measured RSSI at the sender-side and informs the quality adaptation scheme about the rate limits. Then the quality adaptation scheme utilizes this rate limits to adjust the quality of the video stream. Through performance evaluations, we prove that our cross-layer design improves the wireless link utilization and the quality of the video stream simultaneously.     

Mobility support in wireless Internet

The tremendous advancement and popularity of wireless access technologies necessitates the convergence of multimedia (audio, video, and text) services on a unified global (seamless) network infrastructure. Circuit-switched proprietary telecommunication networks are evolving toward more cost-effective and uniform packet-switched networks such as those based on IP. However, one of the key challenges for the deployment of such wireless Internet infrastructure is to efficiently manage user mobility. To provide seamless services to mobile users, several protocols have been proposed over the years targeting different layers in the network protocol stack. In this article we present a cross-layer perspective on the mobility protocols by identifying the key features of their design principles and performance issues. An analysis of the signaling overhead and handoff delay for some representative protocols in each layer is also presented. Our conclusion is that although the application layer protocol is worse than the protocols operating in the lower layers, in terms of handoff delay and signaling overhead, it is better suited as a potential mobility solution for the next-generation heterogeneous networks, if we consider such factors as protocol stack modification, infrastructure change, and inherent operational complexity.     

Cross-Layer Radio Resource Allocation for Multicarrier Air Interfaces in Multicell Multiuser Environments

Packet scheduling over shared channels is one of the most attractive issues for researchers dealing with radio resource allocation in wireless networks as modern systems' different traffic types, with different application requirements, need to coexist over the air interface. Recently, attention has been attracted to multicarrier techniques and the application of cross-layer approaches to the design of wireless systems. In this paper, a radio access network using a multicarrier air interface is considered in a multicell multiuser context. We propose a new cross-layer scheduling algorithm that manages channel, physical layer, and application-related information; we compare its performance with a previously published cross-layer strategy and with simpler well-known channel-aware or channel-unaware techniques and then discuss its optimization. We investigate the performance in terms of perceived user quality and fairness in the presence of mixed realistic traffic composed of H.264 video streaming with tight bounds on the delay jitter and file transfer protocol (FTP) data. To support video traffic, application-suited buffer-management techniques are also considered in conjunction with scheduling, and link adaptation is implemented at the physical layer to better exploit channel fluctuations. The role of scheduling and resource-allocation functionalities are discussed. It is shown that the cross-layer strategy proposed guarantees the same performance obtained by the previously published algorithm while reducing complexity. Moreover, under heavily loaded conditions, the cross-layer scheduling strategy provides a significant gain with respect to simple channel-aware or channel-unaware techniques.     

A cross-layer framework for multi-layer-video multicast with QoS requirements in multirate wireless networks

We propose a cross-layer framework for efficient multi-layer-video multicast with rate adaptation and quality-of-service (QoS) requirements in multirate wireless networks. We employ time division multiple access at the physical layer to transmit different video layers' data. The multicast sender then dynamically regulates the transmission rate and time-slot allocation based on the channel state information (CSI) and loss QoS requirements imposed by upper protocol layers. Under our proposed cross-layer framework, we first design a rate adaptation algorithm to fulfill the diverse loss QoS requirements for all video layers while achieving high multicast throughput. We then develop a time-slot allocation scheme which synchronizes data transmission across different video layers. Also conducted are simulation results to validate and evaluate our designed adaptive multicasting schemes under the proposed cross-layer framework.     

仿真研究无线多跳网络跨层协议设计的优劣

为了改善无线多跳网络的性能，很多研究表明跨层协议设计比OSI模型更适合无线网络。本文分析了无线多跳网络的特征及对各协议层的影响，给出了跨层协议设计对网络性能的改善以及它可能带来的问题，并针对速率自适应MAC协议和网络层路由协议之间的相互影响给出了仿真实例，结果证明跨层协议设计要充分考虑不同协议之间的相互影响，合理规划、谨慎实施，否则网络的性能不升反降。     

Adaptive cross-layer protection strategies for robust scalable video transmission over 802.11 WLANs

Robust streaming of video over 802.11 wireless local area networks poses many challenges, including coping with bandwidth variations, data losses, and heterogeneity of the receivers. Currently, each network layer (including physical layer, media access control (MAC), transport, and application layers) provides a separate solution to these challenges by providing its own optimized adaptation and protection mechanisms. However, this layered strategy does not always result in an optimal overall performance for the transmission of video. Moreover, certain protection strategies can be implemented simultaneously in several layers and, hence, the optimal choices from the application and complexity perspective need to be identified. In this paper, we evaluate different error control and adaptation mechanisms available in the different layers for robust transmission of video, namely MAC retransmission strategy, application-layer forward error correction, bandwidth-adaptive compression using scalable coding, and adaptive packetization strategies. Subsequently, we propose a novel adaptive cross-layer protection strategy for enhancing the robustness and efficiency of scalable video transmission by performing tradeoffs between throughput, reliability, and delay depending on the channel conditions and application requirements. The results obtained using the proposed adaptive cross-layer protection strategies show a significantly improved visual performance for the transmitted video over a variety of channel conditions.     

A Generic Framework for Cross-Layer Optimisation in Wireless Personal Area Networks

Wireless Personal Area Networking (WPAN) is introduced as a new concept for next generation wireless systems. WPANs are short-range wireless systems operating in the direct surrounding of the user. A reference architecture for short-range wireless communications has been designed covering the end-to-end system design. Traditional protocol stack implementations based on layering do not function efficiently in wireless environments due to inefficiency, inflexibility and suboptimality of the functionalities in the different layers. Specifically in WPAN and other short-range wireless systems the performance benefits from a cross-layer design strategy, supporting adaptability and optimizing the use of resources over multiple layers of the protocol stack. In this paper we advocate cross-layer optimisation for WPAN systems and introduce a centralised control structure for interaction between different layers in master or leader devices. The control structure adapts the link characteristics to the channel state and user requirements. Allowing for the support of heterogeneous services, each with their own quality-of-service demands, in wireless environments.     

Cross-layer mobile WiMAX MAC designs for the H.264/AVC scalable video coding

To effectively provide the QoS of streaming services in mobile WiMAX systems, this paper proposes a cross-layer design between the streaming server and mobile WiMAX base stations. We will show that for each user the implementation of multiple connections with feedback information of the available transmission bandwidth is critical for supporting H.264/AVC-based scalable video coding in which the transmission packets can be further separated into multiple levels of importance. To quantify the performance, a mobile WiMAX simulation platform including both the video encoder/decoder and IEEE 802.16e MAC controls is developed.     

Cross-layer feedback architecture for mobile device protocol stacks

Applications using traditional protocol stacks (e.g., TCP/IP) from wired networks do not function efficiently in mobile wireless environments. This is primarily due to the layered architecture and implementation of protocol stacks. One mechanism to improve the efficiency of the stack is cross-layer feedback, that is, making information from within one layer available to another layer of the stack. For example, TCP retransmissions can be reduced by making it aware of network disconnections or handoff events. We highlight the need for a cross-layer feedback architecture and identify key design goals for an architecture. We present our ECLAIR architecture, which satisfies these design goals. We describe a prototype implementation that validates ECLAIR. We also discuss other cross-layer architectures and provide a cross-layer design guide.     

Cross-Layer Modeling of Wireless Channels: An Overview of Basic Principles

To optimize performance of applications running over wireless channels, state-of-the-art technologies incorporate a number of channel adaptation mechanisms at different layers of the protocol stack. These mechanisms affect the way communication is performed and their joint effect is often difficult to predict. Recently, to evaluate joint operation of these mechanisms, a number of cross-layer performance models have been proposed. These models abstract functionality of layers providing channel adaptation and characterize performance of information transmission at higher layers, where it is usually standardized. While cross-layer performance models differ in some details, most of them are similar in the way they approach the problem. In this paper we identify similarities between these models, formulate step-by-step cross-layer modeling procedure and discuss its basic components.     

Cross-layer design for resource allocation in 3G wireless networks and beyond

Cross-layer design approaches are critical for efficient utilization of the scarce radio resources with QoS provisioning in the third-generation wireless networks and beyond. Better system performance can be obtained from information exchanges across protocol layers, which may not be available in the traditional layering architecture. This article provides an overview of cross-layer design approaches for resource allocation in 3G CDMA networks, summarizes state-of-the-art research results, and suggests further research issues. In addition, a cross-layer design approach for real-time video over time-varying CDMA channels is proposed, where link layer resource allocation benefits from information in both the application and physical layers. Simulations results are given to demonstrate the effectiveness of the proposed approach.     

下一代无线网络中的跨层设计

下一代无线通信系统必须能够与互联网实现信息交互,这就需要利用通信协议来实现系统与其他通信系统间的互连互通。但是,现有通信协议基于OSI标准,其协议栈按照严格的分层方式工作,很难适应快速变化的无线通信环境。通过对现有协议栈进行改进,加入跨层设计方案则有助于改善下一代无线系统性能。文章简要分析了分层协议栈局限性,讨论了跨层设计原理,并系统地阐述了跨层设计时物理层、链路层、网络层、传输层和应用层协议应考虑的因素。     

Cross-Layer Design for QoS Support in Multihop Wireless Networks

Due to such features as low cost, ease of deployment, increased coverage, and enhanced capacity, multihop wireless networks such as ad hoc networks, mesh networks, and sensor networks that form the network in a self-organized manner without relying on fixed infrastructure is touted as the new frontier of wireless networking. Providing efficient quality of service (QoS) support is essential for such networks, as they need to deliver real-time services like video, audio, and voice over IP besides the traditional data service. Various solutions have been proposed to provide soft QoS over multihop wireless networks from different layers in the network protocol stack. However, the layered concept was primarily created for wired networks, and multihop wireless networks oppose strict layered design because of their dynamic nature, infrastructureless architecture, and time-varying unstable links and topology. The concept of cross-layer design is based on architecture where different layers can exchange information in order to improve the overall network performance. Promising results achieved by cross-layer optimizations initiated significant research activity in this area. This paper aims to review the present study on the cross-layer paradigm for QoS support in multihop wireless networks. Several examples of evolutionary and revolutionary cross-layer approaches are presented in detail. Realizing the new trends for wireless networking, such as cooperative communication and networking, opportunistic transmission, real system performance evaluation, etc., several open issues related to cross-layer design for QoS support over multihop wireless networks are also discussed in the paper.