Efficient Data Dissemination in Vehicular Ad Hoc Networks

Abstract

In recent years, Vehicular ad hoc networks (VANETs) have gained a lot of attention both from academia and industry due to their flexibility to provide uninterrupted services such as-entertainment, adaptive route selection, etc., to the end. In VANETs, vehicles interact with other vehicles and to the fi xed infrastructures for data dissemination. In VANETs vehicles act as intelligent sensing units having communication and computation capabilities with Application Unit (AU), and On Board Unit (OBU) installed in them. These units can be used in wide range of applications including alert generation, community services, tra c management, etc. and can also impart security, safety and comfort to the on board passengers. With an increasing use of vehicular communications, there may be congestion in the network and quality of service may be compromised. This results in a performance degradation in data dissemination also. A number of research proposals for effi cient data dissemination have been laid down since its inception. Most of the existing solution for data dissemination in VANETs were unable to provide a comprehensive scheme to meet the Quality of Service (QoS) parameters. Moreover, the existing schemes were unable to provide reliable communication and the broadcast storm problem was not been solved completely. Hence, there was a need of a new solution that meets the desired QoS parameters and ensures reliable communication. To address the challenge of meeting the QoS parameters also with changing topology in high mobility scenario, a Quality-Aware Data Dissemination (QADD) scheme has been proposed for VANETs. The protocol was tested for delay incurred, extra messages generated and percent active links with varying vehicle density and speed. QADD successfully overcomes the broadcast storm and gray zone problems and has lowered the generation of extra messages as compared to SOBP [1] and DDOR [2] schemes. The recovery algorithm proposed in this proposal makes it fault tolerant. To improve the effi cacy of data dissemination and to target the problem of heavy congestion, a context aware congestion resolution scheme namely Minimum Calculated Desired Time (MCDT) has been proposed. The scheme is flexible to work in fi ve stages of vehicular state transition and is divided into four phases, i.e., construction, maintenance, message transition, and recovery. Minimum angle method [3] is modifi ed and used as recovery protocol. Links are classi fied into zones of stability based on the received signal strength. The scheme calculates virtual connectivity, and decides the forwarding vehicle based upon the real-time parameters. The impact of varying speed and density on Packet Delivery Ratio (PDR), End-to-End Delay (E2ED) and overhead is evaluated and compared with GyTAR [4] and A-STAR [5]. The MCDT scheme outperformed the other schemes on probability of successful transmission, average content distribution rate, downloading speed and resource utilization with lower overhead and average load indicating an improvement in e fficiency. Blind offloding of messages in the network especially during emergency causes broad cast storm problem which results in reduced PDR and increased delay. Using the game theoretic approach, a Reliability-aware Intelligent Data Dissemination (ReIDD) protocol has been proposed to mitigate this issue. Payo ff is calculated for vehicles and weights are assigned to links to calculate reliability. Vehicles with stable links are included in cluster and data is transmitted based on highest cumulative payoff of the possible route. The scheme is executed with varying learning rates of nodes. PDR, Query Response Time (QRT) and reliability are examined and results indicate an increase in performance with lower learning rates. An improvement of 68% in E2ED is observed in the proposed scheme which strengthens its candidature as a solution of broadcast storm problem. Application of VANETs can be extended to offl oading the cellular data in real-time to share the load due to overwhelming growth in mobile data traffi c. In Real-time Data Dissemination and offloading (RDDO) proposal, game theory is applied and utility of each vehicle is calculated by taking connectivity, density, speed and angle of movement of vehicle into account. Utility of WiFi Access Points (APs) is calculated based on the distance from destination, available bandwidth, area of the network and its communication radius. From the results obtained, it is clear that RDDO scheme had an edge over existing state-of-the art protocols in message progress, extra messages exchanged, message dissemination speed, and E2ED.