1. CSLI 5350G - Pervasive and Mobile Computing Week 3 - Paper Presentation “RPB-MD: Providing robust message dissemination for vehicular ad hoc networks” Name: Dinesh Bilimoria Date: Oct 2 nd, 2013

2. Research Paper 2 Bibliography: Liu C., Chigan C., "RPB-MD: Providing robust message dissemination for vehicular ad hoc networks", Ad Hoc Networks, Volume 10, Issue 3, May 2012, Pages 497-511

3. Background 3 Relative Position Based Addressing Model Total Relative Distance Dissemination Direction Range of Zone of Relevance (ZoR) During the message dissemination session,, each vehicle j with satisfying, should be in the intended receiver set. Set of Vehicles on ZoR Vehicle on Highway

4. Background 4 Directional Greedy Broadcast Routing (DGBR) Vehicle A is assumed to be the message source node, and it transmits the message to its front vehicles by its front directional antenna. In A’s communication range, vehicles B and C will receive this message at their first time, and they will contend to rebroadcast the message after their own period Ti Vehicle C, with the smallest Ti, will be the best next forwarder to rebroadcast the message with its two directional antennas. It will transit from inactive state to active state to act as the new message head. In the case that the message head E does not overhear any new rebroadcast after T, the network is considered to be disconnected and vehicle E will rebroadcast the message at an interval T’.

5. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 5 Objective  The goal is to reliably and efficiently disseminate messages to the vehicles in the zone-of-relevance using Relative Position Based Message Dissemination (RPB-MB). Proposal  Use only the forwarding state of message dissemination  Achieve robust message dissemination and reduce communication overhead using Directional Greedy Broadcast Routing (DGBR)  Implement RPB-MB based on local traffic density, speed and the number of neighbors. This can be achieved in real time by exchanging beacons among neighbors  Proposed protocol to be adaptive to real vehicular traffic using;

6. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks Message Forwarding State  In the forwarding state, every node goes thru 3 states and enter one stage; Active State: Node in this state is the Message Head Intermediate State: Node in this state are the Message Holders Inactive State:Node do not receive or have dropped the Message Failure Processing: When ACK is not received

7. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 7 Contributions  Guarantee high delivery ratio with acceptable latency and limited overhead using RPB-MD  Improve the dissemination reliability by rebroadcasting message dynamically using DGRB  Vehicular traffic density will significantly affect the network connectivity  Under varying traffic density, the message will be disseminated efficiently  RPB-MD can be extended to 2-D scenarios Assumptions  Vehicles can assume the relative distance between neighbors based on GPS position  Two directional antennas with bandwidth of 180 degrees are equipped  All the vehicles can acquire local vehicle traffic density and average vehicle velocity  Assume that all the vehicle nodes are synchronized  The vehicle communication range ie R is set to be uniform to calculate the neighbor's waiting weight

8. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 8 Message Dissemination  From Message Head 1 to Message Head n, the message is disseminated by DGBR which is based on relative distance and moving direction = Weight of Relative Distance = Ramp Function of Vehicle Velocity

9. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 9 Message Dissemination Scenarios Scenario CaseImpact Message holder (message head) does not receive the implicit ACK The old message head will rebroadcast the message again. If the new message head is in range, then it will send an implicit ACK Otherwise, the new message holders will contend to send the implicit ACK If the message head comes upon some fault to disseminate the message. The message holders, whose moving direction is the same as the message dissemination direction, will resume another contention to forward the message after certain time period t 1 GPS measurements will have certain amount of inaccuracy depending on the environment and systems RPB-MD will not suffer the problem of transmission failures due to location errors since it does not maintain neighbor tables. Sensitivity analysis of packet duplication Can have one packet duplication in a scenario where Vehicle V1 has a time period T1 and there exists another vehicle V2 with a time period such that where is the minimum time interval needed for packet suppression. Impact on Curving RoadConsider both routing in the road segment and routing in the intersection. Both road distance and traffic condition must be considered. In future how to select road segment reflecting dynamic road segment will require further research.

10. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 10 Evidence  Time parameters are designed dynamically and adaptively according to the message attributes and vehicular traffic density Evaluation of Prototype  Simulation experiments are conducted using four protocols: epidemic routing mechanism, GPSR, IVG and proposed RPB-MD protocol.  Metrics are used to compare performance, Data Delivery Ratio, Data Overhead, Average Delay, Network Reachability  RPB-MD can steadily hold very high delivery ratio at different vehicle densities  In epidemic routing, IVG and GPSR, there are more collisions than that of RPB-MD  The data delivery ratio of epidemic routing, IVG and GPSR decreases faster than that of RPB-MD when data sending rate increases.

11. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 11 Results

12. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 12 Shoulder of Giants  This research was build on previous car following model. Impact  Cited by 5 papers since 2012 This research also looked at other routing protocols; (1) destination sequenced distance vector (DSDV) routing (2) ad hoc on-demand distance vector (AODV) routing = Safety Distance between Rear Bumper and Rear Bumper = Co-efficient of the Maximum Accelerations

13. RPB-MD: Providing robust message dissemination for vehicular ad hoc networks 13 Open problems  Investigate ways to design an advanced cross-layer between MAC and routing layer to solve the problem of interference, scalability and connectivity in VANET.  Focus on the issues of message storage in the ZoR within the message lifetime. Discussion points  What is RPB-MD ?  Relative Position Based Message Dissemination  In which state does the Message Holders carry information?  Intermediate State  Which routing protocol was used to reduce communication overhead ?  Directional Greedy Broadcast Routing (DGBR)