Cross-layer Optimization Strategies Research Articles

Design and evaluation of novel VoIP link adaptation algorithm based on GTS function

This paper deals with design of novel VoIP link adaptation algorithm from the speech quality critical conditions point of view. The algorithm design is based on cross-layer optimization principle. In the case of this algorithm, the cross-layer optimization strategy uses an interaction of application layer and network layer methods, such as a method of improved speech quality critical conditions detection based on PESQ score (speech quality parameter) and GTS function, respectively. The primary goal of this algorithm is improving speech quality in the VoIP connections, which are established in the respective link. The assessment of speech quality is carried out by means of the accomplished PESQ algorithm. The GTS function is used for the purpose of transmission bit rate control (limitation). Our experiments show that this approach can lead to the improvement of speech quality in respective VoIP connections.

Multi-user video streaming over multi-hop wireless networks: A distributed, cross-layer approach based on priority queuing

Emerging multi-hop wireless networks provide a low-cost and flexible infrastructure that can be simultaneously utilized by multiple users for a variety of applications, including delay-sensitive multimedia transmission. However, this wireless infrastructure is often unreliable and provides dynamically varying resources with only limited quality of service (QoS) support for multimedia applications. To cope with the time-varying QoS, existing algorithms often rely on non-scalable, flow-based optimizations to allocate the available network resources (paths and transmission opportunities) across the various multimedia users. Moreover, previous research seldom optimizes jointly the dynamic routing with the adaptation and protection techniques available at the medium access control (MAC) or physical (PHY) layers. In this paper, we propose a distributed packet-based cross-layer algorithm to maximize the decoded video quality of multiple users engaged in simultaneous real-time streaming sessions over the same multi-hop wireless network. Our algorithm explicitly considers packet-based distortion impact and delay constraints in assigning priorities to the various packets and then relies on priority queuing to drive the optimization of the various users' transmission strategies across the protocol layers as well as across the multi-hop network. The proposed solution is enabled by the scalable coding of the video content (i.e. users can transmit and consume video at different quality levels) and the cross-layer optimization strategies, which allow priority-based adaptation to varying channel conditions and available resources. The cross-layer strategies - application layer packet scheduling, the policy for choosing the relays, the MAC retransmission strategies, the PHY modulation and coding schemes - are optimized per packet, at each node, in a distributed manner. The main component of the proposed solution is a low-complexity, distributed, and dynamic routing algorithm, which relies on prioritized queuing to select the path and time reservation for the various packets, while explicitly considering instantaneous channel conditions, queuing delays and the resulting interference. Our results demonstrate the merits and need for end-to-end cross-layer optimization in order to provide an efficient solution for real-time video transmission using existing protocols and infrastructures. Importantly, our proposed delay-driven, packet-based transmission is superior in terms of both network scalability and video quality performance to previous flow-based solutions that statically allocate resources based on predetermined paths and rate requirements. In addition, the results provide important insights that can guide the design of network infrastructures and streaming protocols for video streaming.

MOS-Based Multiuser Multiapplication Cross-Layer Optimization for Mobile Multimedia Communication

We propose a cross-layer optimization strategy that jointly optimizes the application layer, the data-link layer, and the physical layer of a wireless protocol stack using an application-oriented objective function. The cross-layer optimization framework provides efficient allocation of wireless network resources across multiple types of applications run by different users to maximize network resource usage and user perceived quality of service. We define a novel optimization scheme based on the mean opinion score (MOS) as the unifying metric over different application classes. Our experiments, applied to scenarios where users simultaneously run three types of applications, namely voice communication, streaming video and file download, confirm that MOS-based optimization leads to significant improvement in terms of user perceived quality when compared to conventional throughput-based optimization.

Collaborative resource exchanges for peer-to-peer video streaming over wireless mesh networks

Peer-to-peer collaboration paradigms fundamentally change the passive way wireless stations currently adapt their transmission strategies to match available resources, by enabling them to proactively influence system dynamics through exchange of information and resources. In this paper, we focus on delay-sensitive multimedia transmission among multiple peers over wireless multi-hop enterprise mesh networks. We propose a distributed and efficient framework for resource exchanges that enables peers to collaboratively distribute available wireless resources among themselves based on their quality of service requirements, the underlying channel conditions, and network topology. The resource exchanges are enabled by the scalable coding of the video content and the design of cross-layer optimization strategies, which allow efficient adaptation to varying channel conditions and available resources. We compare our designed low complexity distributed resource exchange algorithms against an optimal centralized resource management scheme and show how their performance varies with the level of collaboration among the peers. We measure system utility in terms of the multimedia quality and show that collaborative approaches achieve ~50% improvement over non-collaborative approaches. Additionally, our distributed algorithms perform within 10% system utility of a centralized optimal resource management scheme. Finally, we observe 2-5 dB improvement in decoded PSNR for each peer due to the deployed cross-layer strategy

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 wireless multimedia transmission: challenges, principles, and new paradigms

Wireless networks are poised to enable a variety of existing and emerging multimedia streaming applications. As the use of wireless local area networks spreads beyond simple data transfer to bandwidth-intense, delay-sensitive, and loss-tolerant multimedia applications, addressing quality of service issues become extremely important. Currently, a multitude of protection and adaptation strategies exists in the different layers of the open systems interconnection (OSI) stack. Hence, an in-depth understanding and comparative evaluation of these strategies are necessary to effectively assess and enable the possible trade-offs in multimedia quality, power consumption, implementation complexity, and spectrum utilization that are provided by the various OSI layers. This further opens the question of cross-layer optimization and its effectiveness in providing an improved solution with respect to the above trade-offs. In this article we formalize the cross-layer problem, discuss its challenges, and present several possible solutions. Moreover, we also discuss the impact the cross-layer optimization strategy deployed at one station has on the multimedia performance of other stations. We introduce a new fairness concept for wireless multimedia systems that employs different cross-layer strategies, and show its advantages when compared to existing resource allocation mechanisms used in wireline communications. Finally, we propose a new paradigm for wireless communications based on competition, which allows wireless stations to harvest additional resources or free up resources as well as optimally and dynamically adapt their cross-layer transmission strategies to improve multimedia quality and/or power consumption.