Throughput analysis of the ieee 802.11p enhanced distributed channel access function in vehicular environment

Abstract 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

Mobile multimodal user interfaces

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mobile Multimodal User Interfaces.

A multitude of information, single and structured multimedia contents are available from the World Wide Web at ever increasing variety, in different modalities (e. g. audio, text, and video) and formats. Yet users of Mobile and Web applications are typically not experiencing these in original quality or layout, due to the form factor limitations of their mobile devices. Awkwardly, the surrounding devices which could accommodate a better experience are mostly left out in Mobile application interaction scenarios. On the way to achieve a true Mobile Multimodal User Interfaces experience, dynamic user interface adaptation for Mobile applications has to be tailored to pervasive multi-device environments and automated adaptation should put users in the middle. Relevant context information, like the available devices or user’ location has to be considered to achieve a new user interaction experience. One of the key problems is the lack of suitable device descriptions for multimodal adaptation and their consistent integration through various discovery mechanisms (e. g. Bluetooth, UPnP, SIP). Further, optimal delivery of multimedia content across different devices with their varying capabilities, especially using structured or complex multimedia has not been studied thoroughly yet. Finally user interaction should be enabled across all available devices, so that a user can freely interact using their preferred input modality. According to the stated problems, the research in this thesis focuses on modality device descriptions and discovery, intelligent multimedia presentation delivery and exchangeable modalities application control. Contributions include a system architecture definition for Mobile Multimodal User Interfaces, named the User Interface Adaptation Function (UIAF), a device description approach for user interface devices suitable for quality comparison with multimedia contents, mechanisms for inclusion of different discovery means in one consistent discovery framework, a framework for exchangeable modalities application control and an extensive adaptation process definition for multimedia presentation delivery. Background information is provided by a thorough related work review for multimodal user interfaces, multimedia and ubiquitous computing with challenges identified. Based on this analysis the UIAF system design is presented. The proposed new functionalities ate defined within the system architecture. Finally, the scenario based evaluation presents two realisations of the UIAF for mobile terminal and service platforms

CLWPR A novel cross-layer optimized position based routing protocol for VANETs

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

Performance evaluation of an Adaptive Route Change application using an integrated cooperative ITS simulation platform

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%

Asynchronous multi-channel MAC for vehicular ad hoc networks

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

Throughput analysis of the IEEE 802.11p enhanced distributed channel access function in vehicular environment

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

A COMPREHENSIVE SIMULATION TOOL SET FOR COOPERATIVE SYSTEMS

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