Rpl
Download as PPT, PDF1 like2,388 views
This paper evaluates the performance of the Routing Protocol for Low power and lossy networks (RPL) under mobility in vehicular ad hoc networks (VANETs). It shows that fine-tuning RPL's timers, including using an immediate response to topology changes and an adaptive timer approach, can improve packet delivery ratio by up to 20% compared to the standard RPL implementation. Simulation results demonstrate that decreasing the DIO message period and ETX probe period improves delivery ratio, but also increases overhead. An adaptive timer approach is recommended to balance performance and overhead with changing network conditions.
Rpl
- 1. A ComprehensiveA Comprehensive Evaluation of RPLEvaluation of RPL under Mobilityunder Mobility Kevin Lee, Raghuram Sudhaakar, Jianxia Ning, Lillian Dai, Sateesh Addepalli, Flavio Bonomi * Paper accepted by Consumer Communications And Networking Conference (CCNC 2012) Special Session Information Dissemination in Vehicular Networks * Extended paper submitted to Focus Issue on Vehicular Ad-hoc Networks in International Journal of Vehicular Technology in February 2012
- 2. Introduction • Traffic offloading from 3G to WiFi AP to save money • Multihop-to-infrastructure WiFi access reduces the number of AP deployments • Intuitively, tree structure is formed with root of the tree at the AP • Consider Routing Protocol for Low power and lossy networks (RPL)
- 3. RPL Operation 0 1 1 3 2 2 2 1DIO DIO DIO DIO DIO DIODIO DIO DIODIO DIO DIODIO DIO 2 3 3 3 3 2 • Directed Acyclic Graph (DAG) Information Option (DIO) messages are broadcast to build the tree; includes a node’s rank (its level), ETX, etc. • ETX probe is sent periodically to probe neighboring ETX
- 4. RPL Fine Tuning for VANETs • Timer fine-tuning: – Immediate ETX probing for a new neighbor – Immediate broadcasting DIO msg upon new parent election – Immediate broadcasting DAO msg upon new parent election • Loop avoidance and detection: – Stamp DIO msg with parent’s ID; – If a node that receives the DIO msg is equal to the parent’s ID in the DIO msg, it’ll discard the DIO msg
- 5. Loop Avoidance and Detection
- 6. Qualnet Evaluation Setup AP 5000m 2500m 25mph, 45mph, 65mph Packet delivery ratio (PDR) and overhead are obtained with varied DIO msg period and ETX probe period Car 1Car 2Car 3Car 7
- 7. Rank Change & Duration wrt Time and Speed • Lead car (Car 1) establishes conn @ 199s/79s @ 25mph/65mph • Rank duration is 22s for 25mph and 9s for 65mph 25mph 65mph
- 8. ETX Probe Period on PDR • The packet delivery ratio decreases as ETX probe interval increases -- delayed response to changing topology
- 9. ETX Probe Period on Overhead • As the probe period increases, the number of ETX probes decreases • PDR does not degrade as much for ETX probe period 1s, 3s, and 5s => topology change is on the level of 5s granularity => An adaptive timer approach for ETX probe recommended
- 10. DIO Msg Period and Speed on PDR • PDR drops as DIO msg period increases • PDR drops as speed increases for a given DIO msg period • Diminishing return with decreasing DIO msg period suggests trickle
- 11. • The lower the DIO msg period, the higher the DIO msg overhead DIO Msg Period and Speed on Overhead • DIO msg overhead increases with increasing speed
- 12. • PDR before and after changes • The improvement is about 20% Modified RPL Improvement
- 13. Conclusion • Studied the impact of DIO msg period and ETX probe period on PDR and overhead => Show the value and advantage of trickle timer • Fine tune RPL and improve its performance in vehicular networks by 20% • Future work: – More complex sim. scenario – Consider speed and direction in forming a tree – Consider trickle timer for ETX probe period
Editor's Notes
- #3: * Wireless service providers such as AT&T and Verizon have changed from a fixed monthly fee to a tiered or per bit pricing structure for data usage. As free WiFi networks become more accessible from vehicles, users will have a strong economic incentive to opportunistically offload data traffic from 3G and 4G links to free WiFi links. * Since WiFi deployment is not prevalent, enabling vehicles to access roadside WiFi through other vehicles (multihop-to-infrastructure) allow more vehicles to take advantage of data offloading.
- #6: A node selects a parent based on the received DIO msgs and calculates its rank: Let’s say a node receives 3 DIO’s from three neighbors. It will consider neighbors whose rank is less than its own. Based on its link etx to each node and their respective ETX to the root, the node can establish ETX using either of the two nodes. The node can then determine who its parent is.
- #9: 10-node caravan traversing a 5000m-long road Inter-node distance is maintained at 250m Traces of 25mph, 45mph, and 65mph Two-way CBR traffic are sent from any car of the caravan