Michail Tsagkaropoulos

Energy efficient and perceived QoS aware video routing over Wireless Multimedia Sensor Networks

Wireless Sensor Networks (WSNs) have an ever increasing variety of multimedia based applications. In these types of applications, network nodes should ideally maximize QoS and minimize energy expenditures in video communication. This article presents PEMuR, a novel dual scheme for efficient video communication, which aims at both energy saving and high QoS attainment. To achieve its objectives, PEMuR proposes the combined use of an energy aware hierarchical routing protocol with an intelligent video packet scheduling algorithm. The adopted routing protocol enables the selection of the most energy efficient routing paths, manages the network load according to the energy residues of the nodes and prevents useless data transmissions through the proposed use of an energy threshold. In this way, an outstanding level of energy efficiency is achieved. Additionally, the proposed packet scheduling algorithm enables the reduction of the video transmission rate with the minimum possible increase of distortion. In order to do so, it makes use of an analytical distortion prediction model that can accurately predict the resulted video distortion due to any error pattern. Thus, the algorithm may cope with limited available channel bandwidth by selectively dropping less significant packets prior to their transmission. Simulation results demonstrate the effectiveness of the proposed scheme.

Power efficient video multipath transmission over wireless multimedia sensor networks

This paper proposes a power efficient multipath video packet scheduling scheme for minimum video distortion transmission (optimised Video QoS) over wireless multimedia sensor networks. The transmission of video packets over multiple paths in a wireless sensor network improves the aggregate data rate of the network and minimizes the traffic load handled by each node. However, due to the lossy behavior of the wireless channel the aggregate transmission rate cannot always support the requested video source data rate. In such cases a packet scheduling algorithm is applied that can selectively drop combinations of video packets prior to transmission to adapt the source requirements to the channel capacity. The scheduling algorithm selects the less important video packets to drop using a recursive distortion prediction model. This model predicts accurately the resulting video distortion in case of isolated errors, burst of errors and errors separated by a lag. Two scheduling algorithms are proposed in this paper. The Baseline scheme is a simplified scheduler that can only decide upon which packet can be dropped prior to transmission based on the packet’s impact on the video distortion. This algorithm is compared against the Power aware packet scheduling that is an extension of the Baseline capable of estimating the power that will be consumed by each node in every available path depending on its traffic load, during the transmission. The proposed Power aware packet scheduling is able to identify the available paths connecting the video source to the receiver and schedule the packet transmission among the selected paths according to the perceived video QoS (Peak Signal to Noise Ratio—PSNR) and the energy efficiency of the participating wireless video sensor nodes, by dropping packets if necessary based on the distortion prediction model. The simulation results indicate that the proposed Power aware video packet scheduling can achieve energy efficiency in the wireless multimedia sensor network by minimizing the power dissipation across all nodes, while the perceived video quality is kept to very high levels even at extreme network conditions (many sensor nodes dropped due to power consumption and high background noise in the channel).

Optimizing Video Transmission over Wireless Multimedia Sensor Networks

This paper proposes an efficient packet scheduling scheme for minimizing perceived video distortion and power consumption over multipath wireless multimedia sensor networks. The proposed scheduling algorithm is responsible for transmitting the video packets over selected multipaths according to their importance (high priority packets over high bandwidth paths). Moreover, whenever the aggregate transmission rate available at the network cannot support the required transmission rate due to high packet loss probability, the scheduling algorithm can selectively drop combinations of video packets prior to transmission to adapt the rate of the sender to the limitations of the wireless channel capacity. The video packets that will be dropped prior to transmission are selected based on a recursive distortion prediction model that has been customized for H.264/AVC coding scheme and counts for isolated losses, burst of losses and losses separated with small lag. Two scheduling algorithms are proposed. The baseline scheme utilizes a novel distortion prediction model and decides upon which packet can be dropped prior to transmission based on the packets impact on the video distortion. Moreover, the power aware packet scheduling is an extension of the baseline capable of estimating the power that will be consumed by each node during the transmission; hence it can control the power consumption by selectively drop the least significant video packets prior to transmission. Simulation results indicate the efficiency of the proposed scheduling scheme in terms of received video distortion (PSNR) and power consumption.

A hybrid scheme for video transmission over wireless multimedia sensor networks

The introduction of multimedia capable sensors has posed new challeges for classic Wireless Sensor Networks that are henceforth required to provide both power and quality efficent routing. This paper proposes an innovative protocol for power and perceived QoS aware routing of multimedia content over Wireless Multimedia Sensor Networks. The proposed scheme comprises the advantages of both energy efficient hierarchical routing and video packet schedulling according to the packets importance. The hierarchical routing algorithms are often utilized for bandwidth efficiency and power control over Wireless Sensor Networks. In addition, packet scheduling is widely adopted as an effective rate adaptation technique in wireless multimedia communications. Both these techniques are combined in a proposed scheme which firstly, utilizes nodes with the highest residual energy and low power-cost paths, in order to perform the routing and secondly, predicts the distortion of video packets and selects to either drop them or transmit them according to the current channel bandwidth limitations. The simulation results prove the efficiency of the proposed combined scheme in terms of power consumption and received video distortion (PSNR).

Intelligence packet scheduling for optimized video transmission over wireless networks

This paper presents an intelligent packet scheduling scheme based on an analytical distortion model for Multi-Referenced H.264 video over 802.11 wireless networks. This model considers that video distortion in H.264 video codecs is based on multi-reference video frames, as opposed to previous video standards. The model has been verified with actual video distortion measurements and it has been compared with a simple additive model that omits the correlation between the frames. The packet dropping that is required in the case of the available transmission rate is limited, takes into consideration the impact of the loss of the frame on the resulting video distortion that depends not only on the distortion of the particular frame but on the distortion effect that propagates to the correlated frames. Furthermore, simulation results show that the proposed model accurately captures the distortion effect for reference based H.264 coding and the improves the reconstructed video quality when is implemented in rate adaptation via packet scheduling.

Enhanced vertical handover based on 802.21 framework for real-time video streaming

This paper presents a novel middleware architecture in order to support multimedia services across inter-technology nodes in a seamless manner and with minimum perceived QoS degradation. The proposed architecture is based on the Media Independent Handover (MIH) framework. The novelty of the proposed architecture is based on a number of enhancements on top of the original MIH scheme. Firstly, the handover decision function is based on triggering/collecting statistics from physical, network and application layer, so that an ongoing multimedia session (video) can be transferred seamlessly. Secondly, the original MIH scheme is coupled with a novel mechanism that updates the video encoding parameters in real time, allowing video QoS adaptation and/or video QoS based vertical handover based on an estimated value of the current Peak Signal to Noise Ratio received by the mobile user. The simulation results carried out with the NS-2 tool parametrized for supporting MIH functionality and H.264 encoded video traffic, have shown a significant improvement both in the received video QoS in terms of PSNR and the network throughput, during WiFi to UMTS handover, under the proposed scheme.

Study of the QoS of video traffic over integrated 3G-WLAN systems

This paper studies the effects on the Quality of Service (QoS) of video across integrated 3G-WLAN networks. QoS has been qualitatively evaluated in terms of packet loss and perceived video quality (PSNR). The video traffic is simulated in this converged environment as a two dimensional Markov chain model. This model has been validated by comparing packet loss of the model with that obtained from real video data. In order to sustain QoS in 3G network, a forced handover policy mechanism is employed instructing video sources with highest bit rate to switch towards the WLAN networks. The simulation results that both packet loss within the converged network is reduced and loss occurrence affecting the perceived video quality is reduced.

Service continuity over intertechnology RATs

This paper proposes a novel architecture that integrates Media Independent Handover (MIH) 802.21 framework and IP Multimedia Subsystem (IMS) functionalities in order to support multimedia services across intertechnology Radio Access Networks (RANs) in a secure and seamless manner. MIH framework is responsible for deciding and triggering a handoff based on physical, network and application layer statistics so that an ongoing multimedia session can be transferred seamlessly and securely (using context transfer) across inter-technology Radio Access Networks. In parallel, IMS provides the functionalities for providing uninterrupted service continuity across different network domains during vertical handoffs. The paper proposes a novel integration between MIH and IMS that results in minimizing handoff latency and improving perceived video quality in terms of PSNR. Real testbed experiments indicate that during a inter IMS domain, MIH vertical handoff with security enhancements, the handoff delay is reduced by 12sec during a 3G-WiFi handover as opposed to a non-integrated MIH/IMS architecture.

Valuing quality of experience: A brave new era of user satisfaction and revenue possibilities

Telecommunication market today is defined by a plethora of innovative products and technologies that constantly raising the bar of technical feasibility in both hardware and software. Meanwhile users constantly demand better quality and improved attributes for all applications, becoming less and less tolerant in errors or inconsistencies. Evaluation methods that were dominant for several years in the field seem to have limited effect on assess end-user satisfaction, leading to unhappy customers and lower revenue for key market players. Ensuring Quality of Service (QoS) proved no longer capable to increase market share therefore a novel evaluation method is necessary. The aim of the present paper is to present a new framework of user-oriented quality assessment that tries to measure the overall experience derived from a telecommunication product. Provided that modern services are based over the principal of sharing an overall experience with others, it seems certain that the new method of estimating Quality of Experience (QoE) will produce much better results, needed by both providers and customers.

On the Impact of MIH Triggering Techniques on the Performance of Video Streaming across Heterogeneous RATs

This paper evaluates the performance of IEEE 802.21 Media Independent Handover (MIH) framework through test-bed experiments conducted on a wireless platform that allows seamless handoff across heterogeneous radio access technology networks of mobile terminals with on-going video sessions. The scope of the study is to evaluate how MIH performs under different handover triggering techniques and to monitor the impact at both packet loss and perceived video quality due to vertical handover. We propose a handover decision policy as part of the MIH framework, which is based on parameters from the physical, network and application layers, gathered from MIH capable mobile terminals and MIH controlled radio access networks. Real testbed experiments demonstrate that triggering from application layer can maintain and optimize QoS better than the network layer triggering.