Tasos Dagiuklas

Hybrid multilayer mobility management with AAA context transfer capabilities for all-IP networks

This article presents a multilayer mobility management scheme for all-IP networks where local mobility movements (micro-mobility) are handled separately from global movements (macro-mobility). Furthermore, a hybrid scheme is proposed to handle macro-mobility (mobile IP for non-real-time services and SIP for real-time services). The internetworking between micromobility and macro-mobility is implemented at an entity called the enhanced mobility gateway. Both qualitative and quantitative results have demonstrated that the performance of the proposed mobility management is better than existing schemes. Furthermore, a context transfer solution for AAA is proposed to enhance the multilayer mobility management scheme by avoiding the additional delay introduced by AAA security procedures.

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).

An obstacle-aware human mobility model for ad hoc networks

In this work we present an obstacle-aware human mobility model for ad hoc networks. Typical examples where the nodes of mobile ad hoc networks are human-operated are natural or man-made disasters, military activities or healthcare services. In these scenarios, obstacles are an integral part of the areas where such networks are deployed in order to facilitate communication among the firemen, policemen, medics, soldiers, etc. In the proposed mobility model, the nodes of the network move around the obstacles in a natural and realistic way. A recursive procedure is followed by each node according to which every time an obstacle is encountered between the nodes current position and the final destination point, the node moves to the obstacles vertex that is closest to the destination. This process is repeated until the destination is reached. The obstacles are also taken into account in modeling the signal propagation. When a packet is transmitted through an obstacle, the power at which it is received is attenuated by a certain value representing the physical layer phenomena suffered by the signal. The model is implemented as an add-on module in Network Simulator ns-2. A thorough simulation study conducted highlights the differences of the proposed model with other mobility models, by investigating the properties of the resulting network topologies and their impact on network performance.

Two layer Denial of Service prevention on SIP VoIP infrastructures

The emergence of Voice over IP (VoIP) has offered numerous advantages for end users and providers alike, but simultaneously has introduced security threats, vulnerabilities and attacks not previously encountered in networks with a closed architecture like the Public Switch Telephone Network (PSTN). In this paper we propose a two layer architecture to prevent Denial of Service attacks on VoIP systems based on the Session Initiation Protocol (SIP). The architecture is designed to handle different types of attacks, including request flooding, malformed message sending, and attacks on the underlying DNS system. The effectiveness of the prevention mechanisms have been tested both in the laboratory and on a real live VoIP provider network.

A middleware architecture supporting seamless and secure multimedia services across an intertechnology radio access network

This article presents a middleware architecture to support multimedia services across intertechnology radio access networks in a secure and seamless manner. The proposed architecture uses the media-independent handover framework, where the handover decision function is based on triggering/collecting statistics from the physical, network, and application layers so that an ongoing multimedia session (video) can be transferred seamlessly and securely (using context transfer) across intertechnology radio access networks. Simulation results show that when a vertical handover is based on the proposed MIH framework (including the context transfer of AAA information), handover latency is reduced by 38 percent during WiFi to UMTS handover and 20 percent during UMTS to WiFi handover compared to a non-MIH-based handover scheme.

Simulating mission critical mobile ad hoc networks

In this paper we present a mobility model for ad hoc networks operating in mission critical situations, like for example natural or man-made disasters, military activities or emergency healthcare services. The proposed model captures the properties of mobility in situations like the above by incorporating hierarchical node organisation, typical for such scenarios modes of node activity, event-based destination selection and presence of physical obstacles that affect both the node movement and the signal propagation. The nodes are divided into groups with each group leader responsible for choosing the destination points. These choices resemble the events that occur in the network deployment area and the corresponding missions that are assigned to the node groups. The proposed model includes two modes of node activity that represent the two types of nodes primarily comprising such networks: the emergency workers and the medical staff. Each event belongs to a certain class, according to which reinforcements are called to provide further assistance. The conducted simulation study highlights the differences between the proposed model and other mobility models, by investigating their properties in terms of the resulting network topology and their impact on the performance of an ad hoc network operating under a well known routing protocol.

Novel cross-layer scheme for video transmission over LTE-based wireless systems

In this paper, a novel cross-layer scheme is presented for video transmission over LTE-based wireless systems. The proposed cross-layer scheme takes into account parameters from the application layer (I-based versus P-based packets), MAC Layer (Scheduling packets according to their importance) and Physical Layer (Linear Precoding). All these parameters are considered within a novel resource allocation algorithm with transmission rate constraints suitable for video applications. Simulations results have shown that the proposed cross-layer scheme performs better in terms of system throughput and perceived video quality against similar cross-layer schemes.

Modeling human mobility in obstacle-constrained ad hoc networks

In this paper we present a mobility model for ad hoc networks consisting of human-operated nodes that are deployed in obstacle-constrained environments. According to this model, the network nodes move around the obstacles in a way that resembles how humans bypass physical obstructions. A recursive procedure is executed by each node at its current position to determine the next intermediate destination point until the final destination point is reached. The proposed mobility model is validated using real-life trace data and studied using both mathematical analysis and simulations. Furthermore, the model is extended to incorporate several operational aspects of ad hoc networks in mission critical scenarios, where it is best applicable. These extensions include hierarchical node organization, distinct modes of node activity, event-based destination selection and impact of the physical obstacles on signal propagation. The model is implemented as an add-on module in Network Simulator (ns-2).

A model of network related QoE for 3D video

Three Dimensional video quality comprises a variety of perceptual attributes, including overall image quality, naturalness, presence, perceived depth, comfort, immersiveness, etc. This paper proposes a novel objective QoE model for 3D video streaming that takes into account network parameters (i.e. packet losses)and is based on the relationship between objective and subjective video quality measures. The investigation is concerned with stereoscopic video (left-and-right views). The analysis of the results indicate that the proposed QoE model has a strong correlation with MOS scores, hence can be effectively used in predicting the overall image quality of 3D videos transmitted over lossy networks.

Hybrid broadcast and broadband networks convergence for immersive TV applications

This article proposes a converged broadcast and broadband platform in order to deliver 3D media to both mobile and fixed users with guaranteed minimum quality of experience (QoE). The work presented offers an ideal business model for operators having both digital video broadcast and Internet Protocol (IP)-based media services. To that end, the DVB and peer-to-peer Internet technologies will be combined to provide sufficient resources for supporting high-bandwidth high-quality 3D multiview video. The motivations behind combining these technologies are outlined with an emphasis on their complementary characteristics. In addition, the overall design of the proposed architecture is presented focusing on the protocols that are exploited to achieve the interworking of the underlying technologies. Moreover, innovative key techniques for supporting both fixed and mobile users in an efficient manner are introduced.