Cross-Layer Multimedia QoS Provisioning over Ad Hoc Networks

The HCPR scheme is implemented as an extension to the OPNET simulation software and is analysed in detail for its QoS performance to deliver multimedia applications over ad hoc networks. It is compared with three well-known and widely used routing protocols: Ad Hoc On Demand Distance Vector (AODV), Optimised Link State Routing (OLSR), and Geographic Routing Protocol (GRP). Several networking scenarios have been carefully configured with variations in networks sizes, applications, codecs, and routing protocols to extensively analyse the proposed scheme. The HCPR enabled ad hoc network outperforms the well-known routing schemes, in particular for relatively large networks and high QoS network loads. These results are promising because many QoS schemes do work for small networks and low network loads but are unable to sustain performance for large networks and high QoS loads. Several directions to extend this research for future work are given.

Design and Analysis of Battery-Less Sensor Networks

One of the major limiting factors preventing wide use of wireless sensor networks in practical scenarios is power consumption. Battery-less or passive sensors promise to alleviate this issue and enable a wide variety of embedded sensor applications such as structural health and vehicular monitoring, biomedical applications, smart homes, and smart grids. Embedding these sensors in structures without the need for changing batteries, their rugged design to withstand harsh environments, and coded communication with multiple access features makes this technology a desirable candidate for a variety of applications. Design and analysis of these sensors from a cross layer point of view is studied in this book chapter. State of the art in fabrication and test of this new class of wireless sensor systems is also reviewed. Interactions between lower layer with passive sensors and upper layer with active sensors—a different perspective on cross layer—is exploited to achieve significant performance gains in terms of signal to noise and interference ratio, correlation peak to side-lobe ratio, operation range, and data rate.

Joint Resource Allocation and Interference Mitigation Techniques for Cooperative Wireless Networks

This chapter presents joint interference suppression and power allocation algorithms for DS-CDMA and MIMO networks with multiple hops and amplify-and-forward and Decode-and-Forward (DF) protocols. A scheme for joint allocation of power levels across the relays and linear interference suppression is proposed. The authors also consider another strategy for joint interference suppression and relay selection that maximizes the diversity available in the system. Simulations show that the proposed cross-layer optimization algorithms obtain significant gains in capacity and performance over existing schemes.

Cross-Layer Optimization for Video Transmission over WLAN

As IEEE 802.11 wireless devices have become increasingly widespread, providing Quality of Service in the context of H.264/AVC, the video coding standard for future multimedia networking, has become an important issue in the fields of communication and networking. Cross-Layer Adaptive Video Prioritization (CAVP) is a cross-layer framework that prioritizes video frame transmission according to the application-layer information and the MAC layer transmission condition. In this chapter, a Peak Signal-to-Noise Ratio (PSNR) estimation method is proposed to sort out different priorities of H.264/AVC (Advanced Video Coding) video frames at the application layer to provide user-centric media quality estimation. Compared to previous heuristic algorithms, the authors also investigate a theoretic access delay estimator to monitor the wireless medium access delay at the MAC layer. In addition, an admission control is employed to serve the delay-sensitive video application and to give higher priority to those critical video frames. Video packets are dynamically classified into different 802.11e access categories according to the level of wireless medium access delay and the priority of the video frames. The myths of naïvely prioritizing video packets based on I/P/B types as well as naïvely assign packets to high priority access categories in 802.11e are resolved. Rather than creating complex scheme that is unable to be implemented in practical scenarios, the authors design the proposed scheme with practical implementability in mind. The proposed scheme is implemented with Click kernel module and the MadWifi WLAN driver. The performance of proposed CAVP design is evaluated by both NS-2 simulations and real testbed experiments, and results show that it enhances receiving video quality in error-prone wireless networking environments.

Replication Strategies for Video On-Demand over Wireless Mesh Networks

In this chapter, dependencies between the different protocol layers and across the hops through WMNs will be exploited to deliver video streaming with high QoE. Specifically, a cross-layer optimization approach is applied to a replication strategy for video on-demand over WMNs. Additionally, the authors consider a distributed implementation algorithm, namely Mod&Timer, to handle the placement of replicas for saving storage resources of the network. Simulation results are shown to demonstrate that the proposed cross-layer design outperforms many existing schemes in terms of QoE. More importantly, compared to other strategies without cross-layer interaction, the proposed cross-layer design satisfies the heterogeneous bandwidth constraint of end users.

Cross-Layer Design in Cognitive Radio Networks

Radio spectrum has become a precious resource. Most frequency bands have been allocated for exclusive use in the US. However, studies have shown that a very large portion of the radio spectrum is unused or underused for long periods of time at a given geographic location. Therefore, allowing users without a license to operate in licensed bands while causing no interference to the license holder becomes a promising way to satisfy the fast growing need for spectrum resources. Dynamic spectrum access and cognitive radio are technologies for enabling opportunistic spectrum access and enhancing the efficiency and utilization of the spectrum. A cognitive radio adapts to the environment in which it operates by sensing the spectrum and then opportunistically exploiting unused and/or underused frequency bands in order to achieve certain performance goals. Due to the close coupling and interaction among protocol layers, the optimal design of opportunistic spectrum access and cognitive radio networks calls for a cross-layer approach that integrates signal processing and networking with regulatory policy making. This chapter introduces basic concepts, design issues involved, and some recent development in this emerging technological field. Future research directions are also briefly examined.

Cross-Layer Design in Wireless Sensor Networks

New and diverse applications for Wireless Sensor Networks (WSNs) have led to new challenges. Cross-layer approaches have proven to be the most efficient optimization techniques for these problems, since they are able to take the behavior of the protocols at each layer into consideration to overcome the constraints for WSNs. Thus, this chapter focuses on identifying the core problems of WSNs and collects available cross layer solutions for them that have been proposed. The literature on cross-layer protocols, protocol improvements, and design methodologies for WSNs are reviewed, and a taxonomy is proposed in order to provide insights on the identification of cross-layer design in WSNs. The open issues are discussed in detail for future research, and precautionary guidelines for cross layer design to WSNs are indicated.

Cross-Layer Techniques for Reliable Wireless Video Communication

Designing wireless video communication system is a challenging task due to high error rates of wireless channels, limited and dynamically varying bandwidth availability, and low energy and complexity requirements of portable multimedia devices. Scalable video coders having excellent rate-distortion performance are most suited to cope with time varying bandwidth of wireless networks, but encoded bits are extremely sensitive to channel errors. This chapter presents a reliable video communication system exploring opportunities offered by various network layers for improved overall performance, while optimizing the resources. More specifically, cross-layer approach for Unequal Error Protection (UEP) of scalable video bitstream is the main theme of this chapter. In UEP, the important bits are given a higher protection compared to the other bits. Conventionally, UEP is achieved by using Forward Error Correction (FEC) at the application layer. However, UEP can also be provided at the physical layer using hierarchical modulation scheme. In this chapter, the authors discuss cross-layer design methodology for UEP that rely on interaction between the application layer and the physical layer to achieve reliable and high quality end-to-end performance in wireless environments. The discussion is mainly focused for wavelet coded video, but it is applicable to other embedded bitstreams as well.

Cross-Layer Monitoring in Cloud Computing

This book chapter describes the different aspects related to designing a suitable monitoring architecture for Cloud Computing, aiming to support cross-layer monitoring across all layers available in the Cloud stack. For this purpose, the importance of monitoring services in Cloud scenarios is outlined, followed by a comprehensible analysis of a wide set of distributed monitoring solutions. After that, the particular requirements related to cross-layer monitoring for Cloud Computing architectures are identified and explained. Then, diverse aspects which may fit a monitoring architecture for fulfilling such requirements are explained. Finally, some future research directions and conclusions are highlighted.

Applications of “Cross-Layer” in Video Communications over Wireless Networks

Because of the impact of noise, interference, fading, and shadowing in a wireless network, there has been a realization that the strict layering of wireline networks may be unsuitable for wireless. It is the volatility over time that demands an adaptive solution and the basis of adaptation must arise by communication of the channel conditions along with the datalink settings. Video communication is particularly vulnerable because, except when reception is decoupled from distribution as in multimedia messaging, there are real-time display and decode deadlines to be met. The predictive nature of video compression also makes it susceptible to temporal error propagation. In this chapter, case studies from the authors’ experiences with broadband wireless access networks and personal area wireless networks serve to illustrate how information exchange across the layers can benefit received video quality. These schemes are all adaptive and serve as a small sample of a much greater population of cross-layer techniques. Given the importance of multimedia communications as an engine of growth for networked communication, “cross-layer” should be the first consideration in designing a video application.