Konstantinos Birkos

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.

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.

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).

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.

Security model for emergency real-time communications in autonomous networks

Towards the proliferation of architectures, tools and applications that have the potential to be used during an emergency rescue mission, we present a framework for emergency real-time communication using autonomous networks, called emergency Mobile Ad-hoc Networks (eMANETs). By eMANETs we refer to networks that are deployed in emergency cases where default telecommunications infrastructure has failed. Our goal is to design a security framework that will secure real-time communications during emergency rescue scenarios. The proposed framework consists of a secure routing protocol, intrusion detection provision and security extension for real-time communications using peer-to-peer overlays. We envisage that the results of this work will aid and serve the needs of any society against any event that threatens serious damage to human welfare or to the environment.

Peer selection and scheduling of H.264 SVC video over wireless networks

Scalable video enables flexible video delivery over IP networks. The adaptation of the video content to the network configuration and the networking conditions is the great advantage of scalable video. In this research work, on-demand H.264 SVC video delivery over wireless multi-hop single-frequency networks is studied. The main objective is to achieve the highest levels of video quality possible while ensuring fairness among competing video flows over a wireless network. With the main barrier being interference, each video receiver has to decide from which peer it will receive a specific layer. The problem of peer selection and layer allocation is formed as a Mixed Integer Linear Program (MILP). A relaxation as a Non-Linear Program (NLP) is also provided. Simulation results based on real input video sequences verify the validity of the theoretical approach.

Cloud for multimedia applications and services over heterogeneous networks ensuring QoE

This paper aims to identify open challenges and propose the future steps towards establishing QoE driven media aware clouds. Cloud computing emerges as technology that allows access to resources over the Internet, transparently and independently of the underlying infrastructure. This study identifies the research challenges that future media-aware cloud computing will need to address. This is important in order to support multimedia services and applications exchange with efficiency, seamlessness and with guaranteed perceived quality across heterogeneous networking technologies, user devices and preferences.

P2Care: A dynamic self-organized healthcare network for ubiquitous healthcare environment

Nowadays chronic diseases pose new challenges in the healthcare domain. Especially, in case of co-morbidities and multi-morbidities where the self-management affects negatively patients ailment, a dynamic, collaborative and self-organized approach is more suitable. In this paper we demonstrate P2Care, a dynamic and self-organized healthcare network for ubiquitous healthcare environment. P2Care exploits the functionalities of structured P2P networks for delivering personalized services in an efficient, scalable and network-friendly manner. Motivated by real-world social groups, P2Care organizes healthcare professionals, providers and patients in groups according to common characteristics and interests.

u-MCHC: A predictive framework for ubiquitous management of exacerbations in chronic diseases

Exacerbations are crucial events in chronic diseases that require continuous management. Knowledge of the exacerbation risk enhances patients quality of life and enables self-management and self-organizing of unscheduled doctor visits and/or hospitalization. This paper proposes a new framework for ubiquitous management of chronic diseases named u-MCHC. The proposed framework incorporates monitoring, decision-making, notification and management processes in order to deliver personalized therapeutical options and services. The delivery of services is realized by means of Next Generation Service Delivery Platform (NG-SDP). A prototype implementation of u-MCHC and its performance is demonstrated in a real world case for Chronic Obstructive Pulmonary Disease (COPD).

Enhanced failover mechanisms for tree-based peer-to-peer streaming

Peer-to-peer streaming has emerged as prominent networking approach for the delivery of real-time video content. The dynamic nature of the peers which is characterized by unpredictable arrivals or departures affects connectivity, stability and consequently the perceived video quality. This phenomenon is more evident in tree-based streaming. This work proposes enhanced failover mechanisms for peer-to-peer streaming over multiple multicast trees. Contrary to existing approaches, the proposed mechanisms take into account the order of arrival of peers and the diversity among different trees in order to provide backup links for the retrieval of missing packets during temporary disconnections. The proposed approaches have been evaluated through simulations both in terms of connectivity and video quality.