This paper proposes an analytical model for the throughput of the enhanced distributed channel access (EDCA) mechanism in the IEEE 802.11p medium-access control (MAC) sublayer. Features in EDCA such as different contention windows (CW) and arbitration interframe space (AIFS) for each access category (AC) and internal collisions are taken into account. The analytical model is suitable for both basic access and the request-to-send/clear-to-send (RTS/CTS) access mode. Different from most of existing 3-D or 4-D Markov-chain-based analytical models for IEEE 802.11e EDCA, without computation complexity, the proposed analytical model is explicitly solvable and applies to four access categories of traffic in the IEEE 802.11p. The proposed model can be used for large-scale network analysis and validation of network simulators under saturated traffic conditions. Simulation results are given to demonstrate the accuracy of the analytical model. In addition, we investigate service differentiation capabilities of the IEEE 802.11p MAC sublayer.

This paper proposes an extension to Session Initiation Protocol (SIP) for contextualized service delivery in a service delivery platform (SDP) that enables device specific multimedia delivery. SIP separates between session establishment and description and is thus, amenable to be extended for advanced implementations which make it an ideal platform for service creation. Device specific multimedia delivery needs rich and flexible device descriptions, and our approach proposes advanced device descriptions through semantic technologies. The proposed SIP extensions have been implemented on a SIP Application Server which functions as SDP in IP Multimedia Subsystem (IMS). The validation of the proposed extensions is shown through an Android SIP client application that acts as a device browser and recommender for different multimedia services to users. An example device user agent (UA) application has also been implemented on a laptop.

In this paper we present simulation results for our implementation of Adaptive Route Change (ARC) application for cooperative Intelligent Transportation Systems (ITS). The general purpose of the application is to generate recommendations for alternative driving routes in order to avoid traffic congestion. The Adaptive Route Change (ARC) application is implemented in an integrated cooperative ITS simulation platform. For the evaluation we chose a reference scenario defining two distinct traffic flows through an urban area that provides four crossings with traffic light controls. We were interested to evaluate the impacts of ARC on fuel and traffic efficiency. For that we introduced five performance metrics (average trip duration, average fuel consumption, average stop duration, maximum queue size and average queue size behind traffic lights) and evaluated ARC in a series of simulations with varied application penetration rates and traffic volume. The results indicate that ARC systems could reduce traffic congestion in intersections and improve fuel consumption. We observe up to one quarter reduction in average trip time and almost one third reduction in average stop time. Fuel consumption is also reduced by up to 17.3%, while average queue size and maximum queue size reduce more than 50%.

This paper proposes a Green Light Optimized Speed Advisory (GLOSA) application implementation in a typical reference area, and presents the results of its performance analysis using an integrated cooperative ITS simulation platform. Our interest was to monitor the impacts of GLOSA on fuel and traffic efficiency by introducing metrics for average fuel consumption and average stop time behind a traffic light, respectively. For gathering the results we implemented a traffic scenario defining a single route through an urban area including two traffic lights. The simulations are varied for different penetration rates of GLOSA-equipped vehicles and traffic density. Our results indicate that GLOSA systems could improve fuel consumption and reduce traffic congestion in junctions.

This paper presents a new multi-channel MAC protocol for Vehicular Ad Hoc Networks, namely, Asynchronous Multi-Channel MAC (AMCMAC). The AMCMAC supports simultaneous transmissions on different service channels, as well as, allowing other nodes to make rendezvous with their provider/receiver or broadcast emergency messages on the control channel. We compare the performance of the proposed protocol with that of IEEE 1609.4 and Asynchronous Multichannel Coordination Protocol (AMCP), in terms of throughput on control and service channels, channel utilization, and the penetration rate of successfully broadcast emergency messages. We demonstrate that AMCMAC outperforms IEEE 1609.4 and AMCP in terms of system throughput by increasing the utilization of control channel and service channels. In addition, AMCMAC mitigates both the multi-channel hidden terminal and missing receiver problems which occur in asynchronous multichannel MAC protocols.

In this paper, we propose a novel position-based routing protocol designed to anticipate the characteristics of an urban VANET environment. The proposed algorithm utilizes the prediction of the node's position and navigation information to improve the efficiency of routing protocol in a vehicular network. In addition, we use the information about link layer quality in terms of SNIR and MAC frame error rate to further improve the efficiency of the proposed routing protocol. This in particular helps to decrease end-to-end delay. Finally, carry-n-forward mechanism is employed as a repair strategy in sparse networks. It is shown that use of this technique increases packet delivery ratio, but increases end-to-end delay as well and is not recommended for QoS constraint services. Our results suggest that compared with GPSR, our proposal demonstrates better performance in the urban environment.

This paper studies the impacts of vehicular communications on efficiency of traffic in urban areas. We consider a Green Light Optimized Speed Advisory application implementation in a typical reference area and present the results of its performance analysis using an integrated cooperative intelligent transportation systems simulation platform. In addition, we study route alternation using vehicle-to-infrastructure and vehicle-to-vehicle communications. Our interest was to monitor the impacts of these applications on fuel and traffic efficiency by introducing metrics for average fuel consumption, average stop time behind a traffic light and average trip time, respectively. For gathering the results, we implemented two traffic scenarios defining routes through an urban area including traffic lights. The simulations are varied for different penetration rates of application-equipped vehicles, driver's compliance to the advised speed and traffic density. Our results indicate that Green Light Optimized Speed Advisory systems could improve fuel consumption, reduce traffic congestion in junctions and the total trip time. Copyright © 2011 John Wiley & Sons, Ltd.

This paper proposes an analytical model for the throughput of the Enhanced Distributed Channel Access (EDCA)mechanism in IEEE 802.11p MAC sub-layer. Features in EDCA such as different Contention Windows (CW) and Arbitration Interframe Space (AIFS) for each Access Category (AC), and internal collisions are taken into account. The analytical model is suitable for both basic access and the Request-To-Send/Clear-To-Send (RTS/CTS) access mode. The proposed analytical model is validated against simulation results to demonstrate its accuracy.

PRE-DRIVE C2X is a project funded within the 7th Framework Programme of the EU to support the development and introduction of cooperative systems. One major part of this work is the creation of a comprehensive tool set of simulation models integrating all fields of expertise involved. The objective is to create, test and apply an integrated simulation tool set that allows to simulate and evaluate the interaction between vehicle traffic, vehicular communication and co-operative applications. Each of these three areas is treated by dedicated models. Additionally the environmental effects are modelled by a separate modelling approach with detailed algorithms for vehicle dynamics and engine behaviour. The process to arrive at such a model combination from user requirements over pre-existing know-how and other significant steps are described as well as the current status of the work.

This intelligent multimedia adaptation and delivery framework tailors to ubiquitous environments, so that users can experience multimedia content using multiple devices in various mobility situations.

This paper demonstrates the advantages of using structured multimedia documents for session management and media distribution in ubiquitous environments. We show how document manipulations can be used to perform powerful operations such as content to context adaptation and presentation continuity. When consuming media in ubiquitous environments, where the set of devices surrounding a user may change, dynamic media adaptation and session transfer become primary requirements. This paper presents a working system, based on a representative scenario, in which multimedia content is distributed and adapted to a movable user to best suit his/her contextual situation. The implemented scenario includes the following scenes: content selection using a personal mobile phone, content distribution to the most suitable device according to the user's context, and presentation continuity when the user moves to another location. This paper introduces the underlying document manipulations that turn the scenario into a working system.

This paper introduces an architecture, together with an implemented scenario, capable of dynamically adapt the way mobile users consume and interact with multimedia content. The architecture is based on a representative scenario identified by the European project SPICE, in which multimedia content is distributed to a user independently of his/her contextual situation. The implemented scenario includes the following scenes: content selection using a personal mobile phone, content distribution to the most suitable device according to the user's context, and presentation continuity when the user moves to another location. This paper reports on the defined architecture and the current status of its implementation. It shows the initial results in the form of screenshots.

This paper introduces a distributed system for next generation multimedia support in dynamically changing pervasive computing environments. The overall goal is to enhance the experience of mobile users by intelligently adapting the way a service is presented, in particular by adapting the way the user receives multimedia content from the service and how he interacts with the service. The system tailors this presentation to the user's context, for instance based on his current activity (e.g., driving or walking) or the characteristics of the devices that surround him (e.g., devices for multimedia rendering and user interaction devices). The system integrates with the (IMS-based) service platforms of "beyond 3G" telecom operators and allows multimedia content to be rendered on multiple devices at the same time. It can also dynamically and seamlessly adapt the way a service is presented while it is being used (e.g., from gesture-based input to voice commands). These changes are triggered by changes in the user's context (e.g., when the user gets into his car). This paper discusses the system's requirements, presents an architecture proposal and describes its current implementation.

The current access to mobile services a user has, is defined by the user's mobile terminal as the single entry point to an operators network. This comes along with a set of limitations. Although performance and multimedia capabilities of mobile devices are constantly increasing, user-service interaction is still limited due to physical constraints imposed by the form factor. Another drawback is the varying ability of devices to download and execute new services. At the same time it is not possible to synchronise, exchange or share the user's data and media content among different devices. In order to overcome these limitations this paper presents the concept of the Distributed Communication Sphere and the according architectural framework that allows its management. This framework defines functional components to enable multi-device delivery of communication and media service sessions, user input interpretation, terminal management and resource discovery. It also provides flexible service delivery through the dynamic desktop component and relies on intelligent service enablers of the underlying service platform architecture, such as context-awareness, service provisioning and personal profile enablers. The work has been performed as part of the EU IST-SPICE (027617) project targeting intelligent extensions for next generation service platforms.

Autonomic Communication is a new communication paradigm that has been proposed as a way to design new self-organizing, self-healing, self-optimizing, self-protecting and evolvable networks. The motivation comes from the problems created by the unstructured and haphazard growth of the Internet. Among the many guiding principles of Autonomic Communication is context-awareness. In this paper, we discuss architecture for context dissemination in Autonomic networks based on the Autonomous Decentralized Community Communication for information dissemination.

The aim of the paper is to introduce a natural language processor enabling mobile multimodal interfaces to receive user driven free speech in order to enable more natural voice interaction with mobile applications and services to control devices in smart environments. Free speech of users is continuously analysed and matched against semantically defined device service commands. The concept and requirements of the language processor and the semantic description for application commands will be explained. Further the paper elaborates on how this concept was fitted into the general concept of a mobile multimodal interface and elaborates on implementation aspects of the language processor. The feasibility of the approach has been shown in a prototypical implementation. The work has been carried out as part of the research on mobile multimodal interfaces within the IST-FP6 MobiLife project. First order or main headings should commence at the left hand margin of each column, and should be in capitals and can be in bold. Except at the top of a new column the first order heading should be preceded by two lines of space and followed by two lines of space

The IST project MobiLife (IST-2004-511607) is approaching Context-Awareness from the perspective of mobile applications and their enabling components. It envisions a highly distributed and loosely coupled solution in order to exchange context information on different semantic context levels between applications, enabling components and raw context sources. Semantic meaning of the context information exchanged is added via distributed ontology’s attached to it. The definition of the mechanism and interfaces is described by the MobiLife Context Management Framework. Actual context data used within MobiLife applications is provided and defined by a number of specific context providers. New context providers can be easily introduced based on the generic definition of them. The paper aims to provide the overview to the MobiLife context-awareness approach and describes its usage by the means of two MobiLife applications.