PERFORMANCE EVALUATION OF CROSS-LAYER DESIGN WITH DISTRIBUTED AND SEQUENTIAL MAPPING SCHEME FOR VIDEO APPLICATION OVER IEEE 802.11E

The rapid development of wireless communication imposes several challenges to support QoS for real-time multimedia applications such as video stream applications. Researchers tackled these challenges from different points of view including the semantics of the video to achieve better QoS requirements. The main goal of this research is to design a UDP protocol to realize a distributed sequential mapping scheme (DSM) with a cross-layer design and evaluate its accuracy under different network conditions. In DSM, the perceived quality of a multi-layer video is addressed by mapping each video layer into channel resources represented as queues or access categories (ACs) existing in IEEE 802.11e MAC layer. This research work further investigates the efficiency of this scheme with actual implementation and thorough simulation experiments. The experiments reported the efficiency of this scheme with the presence of different composite traffic models covering most known traffic scenarios using Expected Reconstructed Video Layers (ERVL) and packet loss rate as accuracy measures. This research work also investigates the accuracy of calculating the ERVL compared to its value using actual readings of layers drop rate. The effect of changing the ACs queue size on the ERVL is studied. The use of this scheme shows zero-drop in the base layer in almost all scenarios where no ongoing traffic is presented except that the testing video sessions between nodes. In these experiments, the ERVL continuously reported high values for the number of expected reconstructed video layers. While these values dramatically vary when introducing ongoing different composite traffic models together with the testing video sessions between nodes. Finally, a 40% increase in the ACs queue size shows significant improvement on ERVL while an increase of the queue size beyond this value has very little significance on ERVL

802.11n performance analysis for a real multimedia industrial application

In spite of their limitations, wireless networks are being increasingly used in industrial environments. The electromagnetic phenomena that can occur, along with the interference that may occur due to it being an open medium, mean that fluctuations in latencies are often produced. These drawbacks limit the use of wireless networks for distributed factory applications where timeliness is essential. Recent standards, such as 802.11n, offer some interesting characteristics applicable to factory automation. In particular, QoS support and a very high data rate aids their operation under non-saturation conditions, allowing their satisfactory use as an industrial network. In this paper, the potential of these networks is analyzed in a real world scenario and their performance is compared with an idealized scenario. In both cases the priorities behave as expected, however, the algorithms for an auto-rate functioning perform badly in real world situations, especially in industrial scenarios such as those analyzed here, where the mobility of sources and the interference produced by other sources produce frequent rate changes, leading to a reduction in network performance. (C) 2014 Elsevier B.V. All rights reserved.This work is supported by the MCYT of Spain under the project TIN2013-47272-C2-1-R.Silvestre Blanes, JL.; Berenguer Sebastiá, JR.; Sempere Paya, VM.; Todoli Ferrandis, D. (2015). 802.11n performance analysis for a real multimedia industrial application. Computers in Industry. 66:31-40. https://doi.org/10.1016/j.compind.2014.08.00331406

Advanced Wireless LAN

The past two decades have witnessed starling advances in wireless LAN technologies that were stimulated by its increasing popularity in the home due to ease of installation, and in commercial complexes offering wireless access to their customers. This book presents some of the latest development status of wireless LAN, covering the topics on physical layer, MAC layer, QoS and systems. It provides an opportunity for both practitioners and researchers to explore the problems that arise in the rapidly developed technologies in wireless LAN

A selective delayed channel access (SDCA) for the high-throughput IEEE 802.11n

Abstract— In this paper we investigate the potential benefits of a selective delayed channel access algorithm (SDCA) for the future IEEE 802.11n based high-throughput networks. The proposed solution aims to resolve the poor channel utilization and the low efficiency that EDCA’s high priority stations adhere due to shorter waiting times and consequently to the network’s degrading overall end performance. The algorithm functions at the MAC level where it delays the packets from being transmitted by postponing the channel access request, based on their traffic characteristics. As a result, the flow’s average aggregate size increases and consequently so is the channel efficiency. However, in some situations we notice that further deferring has a negative impact with TCP applications, thus we further introduce a traffic awareness feature that allows the algorithm to distinguish which flows are using the TCP protocol and override any additional MAC delay. We validate through various simulations that SDCA improves throughput significantly and maximizes channel utilization

Distributed Medium Access Control for QoS Support in Wireless Networks

With the rapid growth of multimedia applications and the advances of wireless communication technologies, quality-of-service (QoS) provisioning for multimedia services in heterogeneous wireless networks has been an important issue and drawn much attention from both academia and industry. Due to the hostile transmission environment and limited radio resources, QoS provisioning in wireless networks is much more complex and difficult than in its wired counterpart. Moreover, due to the lack of central controller in the networks, distributed network control is required, adding complexity to QoS provisioning. In this thesis, medium access control (MAC) with QoS provisioning is investigated for both single- and multi-hop wireless networks including wireless local area networks (WLANs), wireless ad hoc networks, and wireless mesh networks. Originally designed for high-rate data traffic, a WLAN has limited capability to support delay-sensitive voice traffic, and the service for voice traffic may be impacted by data traffic load, resulting in delay violation or large delay variance. Aiming at addressing these limitations, we propose an efficient MAC scheme and a call admission control algorithm to provide guaranteed QoS for voice traffic and, at the same time, increase the voice capacity significantly compared with the current WLAN standard. In addition to supporting voice traffic, providing better services for data traffic in WLANs is another focus of our research. In the current WLANs, all the data traffic receives the same best-effort service, and it is difficult to provide further service differentiation for data traffic based on some specific requirements of customers or network service providers. In order to address this problem, we propose a novel token-based scheduling scheme, which provides great flexibility and facility to the network service provider for service class management. As a WLAN has small coverage and cannot meet the growing demand for wireless service requiring communications ``at anywhere and at anytime", a large scale multi-hop wireless network (e.g., wireless ad hoc networks and wireless mesh networks) becomes a necessity. Due to the location-dependent contentions, a number of problems (e.g., hidden/exposed terminal problem, unfairness, and priority reversal problem) appear in a multi-hop wireless environment, posing more challenges for QoS provisioning. To address these challenges, we propose a novel busy-tone based distributed MAC scheme for wireless ad hoc networks, and a collision-free MAC scheme for wireless mesh networks, respectively, taking the different network characteristics into consideration. The proposed schemes enhance the QoS provisioning capability to real-time traffic and, at the same time, significantly improve the system throughput and fairness performance for data traffic, as compared with the most popular IEEE 802.11 MAC scheme

Optimum WLAN Protocol and Network Architecture Identification for VOIP Application

This research developed a novel algorithm to evaluate Voice over Internet Protocol (VoIP) metrics of different IEEE 802.11 technologies in order to identify the optimum network architecture among Basic Service Set (BSS), Extended Service Set (ESS), and the Independent Basic Service Set (IBSS). The proposed algorithm will yield the rank order of different IEEE 802.11 technologies. By selecting the optimum network architecture and technology, the best overall network performance that provides a good voice quality is guaranteed. Furthermore, it meets the acceptance threshold values for the VoIP quality metrics. This algorithm was applied to various room sizes ranging from 2x3m to 10x14m and the number of nodes ranged from one to forty. The spatial distributions considered were circular, uniform, and random. The Quality of Service (QoS) metrics used were delay, jitter, throughput and packet loss