DONC: Delay-based Opportunistic Network Coding Protocol

International audienceGenerally, vehicular ad hoc networks (VANETs) carry information public in nature, which benefits most of the vehicular nodes involved. Therefore broadcasting data becomes an interesting option for disseminating data in VANETs. Broadcasting also offers advantages of flexibility and lack of a defined topology. However broadcasting in dense networks can cause collisions due to unnecessary packet retransmissions (broadcast storm problem). Delay-based vehicular broadcast mechanisms have been proven efficient in reducing redundant packet transmissions in dense networks. However, packet losses due to poor wireless medium quality and high mobility render delay-based mechanisms highly incapable of reducing number of packet retransmissions. In this paper, we present a Delay-based Opportunistic Network Coding protocol called 'DONC', which uses Network Coding opportunistically to improve dissemination of broadcast data in loss-prone VANETs and reduce packet retransmissions. We simulate DONC protocol in ns2 and compare it with a delay-based VANET broadcast mechanism. Results prove that DONC protocol outperforms other delay-based mechanisms, specially in the scenario of lossy VANETs

Improving Delay-Based Data Dissemination Protocol in VANETs with Network Coding

In vehicular ad hoc networks (VANETs), for a large number of applications, the destination of relevant information such as alerts, is the whole set of vehicles located inside a given area. Therefore dissemination with efficient broadcast is an essential communication primitive. One of the families of broadcast protocols suitable for such networks, is the family of delay-based broadcast protocols, where farthest receivers retransmit first and where transmissions also act as implicit acknowledgements. For lossless networks, such protocols may approach the optimum efficiency. However with realistic loss models of VANET wireless communication, their performance is noticeably degraded. This is because packet losses have a double effect: directly on the amount of successfully received packets and indirectly with implicit acknowledgement misses. In this article, in order to combat the effects of packet losses, we combine delay-based broadcast with network coding, through a new protocol: Delay-based Opportunistic Network Coding protocol (DONC). By design, DONC aims at cancelling the twofold effects of packet and implicit acknowledgement losses. We describe the details of the DONC protocol, and we study its behavior, with realistic models and simulations. Results illustrate the excellent performance of the protocol

DONC: Delay-based Opportunistic Network Coding Protocol

International audienceGenerally, vehicular ad hoc networks (VANETs) carry information public in nature, which benefits most of the vehicular nodes involved. Therefore broadcasting data becomes an interesting option for disseminating data in VANETs. Broadcasting also offers advantages of flexibility and lack of a defined topology. However broadcasting in dense networks can cause collisions due to unnecessary packet retransmissions (broadcast storm problem). Delay-based vehicular broadcast mechanisms have been proven efficient in reducing redundant packet transmissions in dense networks. However, packet losses due to poor wireless medium quality and high mobility render delay-based mechanisms highly incapable of reducing number of packet retransmissions. In this paper, we present a Delay-based Opportunistic Network Coding protocol called 'DONC', which uses Network Coding opportunistically to improve dissemination of broadcast data in loss-prone VANETs and reduce packet retransmissions. We simulate DONC protocol in ns2 and compare it with a delay-based VANET broadcast mechanism. Results prove that DONC protocol outperforms other delay-based mechanisms, specially in the scenario of lossy VANETs

Forward Prediction Scheduling: Implementation and Performance Evaluation

International audienceUse of multi-homing has became important in order to provide customers with better communication experience. This has been made possible with widespread use of mobile and wireless technology and its capacity to support many network interfaces simultaneously. Connection-oriented transport layer protocols ensure in-order delivery of data during transmission. However multipath transfers cause out-of-order data at receiver side which leads to higher re-ordering costs and data retransmissions. In this paper we present a transport layer implementation for a data scheduling mechanism, which offers to exploit multi-homing for parallel transfer of data. We implement our mechanism using a Linux-Kernel based version of Stream Control Transport Protocol (SCTP) as our testbed and prove that our mechanism significantly improves communication performance

A Data-Scheduling Mechanism for Multi-Homed Mobile Terminals with Disparate Link Latencies

International audienceA mobile terminal equipped with multiple network interfaces can often be found under coverage of multiple access networks. Multihoming enables mobile terminals to communicate simultaneously through multiple interfaces. Connection-oriented transport layer mechanisms ensure reliable, in-order delivery of data, however parallel data transfers in multihoming face problems due to out-of-order reception of data which causes fast-retransmissions and limit the communication throughput. In this paper, we propose a transport layer based mechanism which stripes one flow''s data across multiple disjoint paths efficiently, reducing possible occurrence of out-of-order data. Our mechanism estimates arrival times of data packets to be sent through available paths in an association, and decides which packets are to be sent through each path. We compared our mechanism with a relatively closer approach called Westwood SCTP. We illustrate with the help of simulation results that our mechanism proves to improve multipath communication

Intelligent data-striping: a predictive scheduling mechanism

International audienceNew-age mobile devices are often equipped with multiple network interfaces, which can be exploited simultaneously by sharing a single traffic load over more than one available path. However, parallel data transfers introduce a serious risk to in-order data delivery for transport layer primitives. This is principally due to the difference in characteristics of one path from the other. It becomes crucial that the data be received in-order to avoid fast-retransmissions and head-of-line blocking problem at the transport layer. In this paper, we propose an intelligent transport layer scheduling mechanism which stripes data from one flow to multiple distinct paths and aggregates available resources efficiently. Our mechanism first estimates the arrival times of each packet to be received at the receiver. It then schedules the outgoing packets in a way as to avoid data re-ordering at the receiver. Simulation results show that our mechanism efficiently reduces out-of-order data delivery at reception. Comparing our proposal with Concurrent Multipath Transfer (CMT), an SCTP based load-sharing technique; we show that it outperforms CMT in case of disparate path delays