TDMA Slot Reservation in Cluster-Based VANETS

Mohammad S. AlmalagDissertation Defense

April 3, 2013

Advisor: Michele C. Weigle

Research Question

Can VANETs accommodate non-safety applications’ use of the spectrum while still meeting the requirements of safety applications?

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Outline • Background• Related Work• Thesis Statement • TC-MAC • Evaluation• P2P File Sharing using TC-MAC• Conclusion• Future Work

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BackgroundVANETVehicular Ad-Hoc Network (VANET):

▫Increase traveler safety▫Decrease traveling time and fuel

consumption▫Increase on board luxury

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BackgroundApplications

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Application categories:

• Safety Emergency Electronic Brake

Light

Co-operative Collision warning

Intersection Collision Warning

Approaching Emergency Vehicle

• Non-safety File sharing

Traffic Information

Parking Lot Payment

Electronic Toll Collection

BackgroundMessages• Update messages (periodic)

▫Broadcast every 100 msec▫Speed, position, direction, etc.

• Safety messages▫Event-driven▫Very high priority ▫High reliability

• Non-safety message▫High transmission rate▫Low priority

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BackgroundDSRC/WAVEDedicated Short Range Communication (DSRC)

channels

Wireless Access in Vehicular Environments (WAVE)

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The problem

• Scalability: Poor channel reliability

• Hidden terminal

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The problem

• Safety message requirements▫ High reliability▫ Lifetime 100 msec

[Wang, ACM VANET 2008]

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Non-Safety messages almost shut down

Low Medium High

Traffic Density

Related WorkMAC PROTOCOLS FOR VANETClassified into three different categories1.Channel partitioning:

▫ Time Division Multiple Access (TDMA), Frequency-Division Multiple Access (FDMA) and Code-Division Multiple Access (CDMA)

2.Random access:▫ Contention based protocols, CSMA

3.Taking turns:▫ Polling (master-slave) or token ring

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Related WorkMAC PROTOCOLS FOR VANETExamples:1.VeSOMAC (Yu and Biswas, 2007)

▫ TDMA + location based▫ Does not considerV2I communication

2.VeMAC (Omar et al., 2011)▫ TDMA + 2 transceivers▫ Includes vehicles in both directions + RSU in one TDAM frame▫ 2 transceivers + Overhead

3.PP-CSMA (Yang et al., 2005) 1. CSMA + priority scheme + polling scheme2. Does not consider Broadcasting!

4.MCTRP (Bi et al., 2009)▫ Token ring + 2 transceivers + road conditions▫ Uses CSMA CA mechanism for inter-ring communication

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Thesis Statement

TDMA slot reservation in cluster-based VANETs will improve the performance of delivering non-safety messages with little impact on the delivery of safety messages.

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Outline • Background• Related Work• Thesis Statement • TC-MAC • Evaluation• P2P File Sharing using TC-MAC• Conclusion• Future Work

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My Approach

1. Solves network scalability and hidden terminal problems

2. Fair transmission for safety and non-safety messages

3. Lightweight TDMA assignment scheme 4. Efficiently manages cluster with changes

of topology5. Develop TC-MAC cluster-based MAC

protocol6. Evaluate TC-MAC vs. WAVE

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TC-MACStructure •Based on multi-channel DSRC layout

▫1 CCH and 6 SCHs

•TDMA technique using local IDs for accessing the channels

•Cluster-based protocol▫Clusterhead (CH) scheme

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TC-MACTDMA• Time Division Multiple Access (TDMA) is a

method used to enable multiple nodes to transmit on the same frequency channel

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TC-MACTDMA Frame

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TC-MACTDMA Frame

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TC-MACLocal IDs

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• Each vehicle in the cluster will receive a local ID (0 to Nmax -1):▫ CH will always have ID 1▫ ID 0 is reserved for a virtual vehicle

TC-MACTDMA Slot Assignment

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TC-MACIntra-cluster Communication• Lightweight communication protocol• Each vehicle uses its own mini-slot to disseminate

safety/update messages• First byte, 28 = 128 different situations. Examples:

▫ 0: vehicle is not communicating at the moment▫ 1: vehicle is involved in communicating with some other

vehicle in the cluster. (Unicast)▫ 2: vehicle is involved in communicating with some other

vehicles in the cluster. (multicast group)▫ 3: vehicle is involved in communicating with a vehicle or

RSU outside the cluster▫ 4: the CH is leaving the cluster

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TC-MACIntra-cluster Communication• Disseminating intra-cluster non-safety messages:

▫ Unicast: Set up without CH intervention. Using the local ID for channel and slot time.

▫ Multicast: Small group of vehicles (<5):

Set up without CH intervention. Large group of vehicles (>=5):

Set up with CH intervention.

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TC-MACIntra-cluster Communication

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ClusteringClusterhead Election•Based on the traffic flow:

▫Lane Weight▫Little overhead▫Network Connectivity Level (NCL)▫Average Distance Level (ADL)▫Average Velocity Level (AVL)▫Clusterhead Level (CHL):

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iiii AVLADLtNCLCHL )(

ClusteringCluster Maintenance•The behavior of many vehicles may

change the topology of the cluster:1. A Clusterhead leaving the cluster2. A new vehicle joining the cluster3. A cluster member leaving the cluster4. Two clusters come in range of each other5. A multi-hop cluster shrinks to a one-hop

cluster

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ClusteringCluster MaintenanceA Clusterhead leaving the cluster :

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ClusteringCluster MaintenanceA new vehicle joining the cluster :

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ClusteringCluster MaintenanceTwo clusters come in range of each other:

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CDMA/TC-MACInter-cluster communication• CDMA/TC-MAC hybrid protocol for inter-

cluster communication.• CDMA code for each cluster

▫Intra-cluster communication• Two protocols:

1.Code assignment protocol

2.Recovery protocol

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CDMA/TC-MACCode assignment protocol• Select a CDMA code to the cluster

Done by the CH

• 18 different CDMA codes:▫ Based on the highway and the cluster’s directions▫ 2 codes are global for each highway direction▫ 4 codes for each traffic direction

1 code is temp ▫ Two clusters with two different codes between clusters sharing

the same code

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CDMA/TC-MACRecovery protocol• Solve the issue of having two clusters in

range of each other and sharing the same code

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CDMA/TC-MACDISSEMINATING INTER-CLUSTER MESSAGES• Setup:

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Outline • Background• Related Work• Thesis Statement • TC-MAC • Evaluation• P2P File Sharing using TC-MAC• Conclusion• Future Work

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EvaluationExperiment Plan

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•NS-3 network simulator▫For VANET, (Arbabi and Weigle, 2010):

Intelligent Driver Model (IDM) MOBIL lane change model

•Network settings:▫Transmission range = 300 m▫Max. safety message size = 200 bytes▫Max. non-safety message size = 1200 bytes▫Date rate = 6 Mbits/sec▫CCHI = SCHI = 0.050 sec

EvaluationExperiment Plan

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•Clusterhead Election:▫Scenarios:

Implemented for a highway Different number of lanes, 2, 3, and 4 lanes 2 exits, on the right

25% of vehicles on the rightmost lane take the exit

▫Evaluation metrics: The number of CH changes

▫Comparison: Lowest-ID, Highest-degree, and Utility Function

algorithms

EvaluationClusterhead Election (Results)

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Exit 1

Traffic Flow

EvaluationClusterhead Election (Results)

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Exit 2

Traffic Flow

EvaluationExperiment Plan

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•TC-MAC:▫Scenarios:

Implemented for a highway Different number of lanes, 2, 3, and 4 lanes Different vehicles densities Single-hop and two-hop clusters

▫Evaluation metrics: Reliability of safety messages

Direct safety/update messages Indirect safety messages

Throughput of non-safety messages

EvaluationTC-MAC (Frame)

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EvaluationTC-MAC (Frame)

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EvaluationTC-MAC (Results)

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• Single-hop cluster, all vehicles in the cluster are engaged in communications during their own slot time on the SCHs

EvaluationTC-MAC (Results)

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• Single-hop cluster, half vehicles in the cluster are engaged in communications during their own slot time on the SCHs

EvaluationWAVE (Results)

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• Percentage of collisions during the CCHI for WAVE using a single-hop cluster

EvaluationWAVE (Results)

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• Reliability of Safety messages in WAVE using a single-hop cluster

EvaluationTC-MAC (Results)

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• The Throughput of non-safety messages using TC-MAC in a single-hop cluster

EvaluationWAVE (Results)

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• The Throughput of non-safety messages using WAVE in a single-hop cluster

Outline • Background• Related Work• Thesis Statement • TC-MAC • Evaluation• P2P File Sharing using TC-MAC• Conclusion• Future Work

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ApplicationP2P File Sharing Using TC-MAC

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• Large-scale file sharing between two vehicles• Using their slots on the SCHs• Using un-used slots on the SCHs

▫Needs CH permission • Single-hop cluster

ApplicationExample

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• Assume vehicle A with local ID=4 wants to share a 4 MB MP3 file with vehicle B with local ID=15▫A will make the handshake with B▫A will request time slots on the SCHs from the

CH

ApplicationExample

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• To ensure that vehicles A and B are still receiving update messages from other vehicles nearby during the transmission of the shared file▫Switching on the SCH is required

ApplicationResults

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0 12 32 58# of Slots Borrowed

ApplicationResults

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0 12 32 58# of Slots Borrowed

ApplicationResults

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0 12 32 58# of Slots Borrowed

Conclusion

•TC-MAC performs better than WAVE▫Collision free▫Higher reliability of safety messages▫High throughput of non—safety messages▫Support high densities▫Support topology changes, through the

local IDs•CH election algorithm:

▫Fewer CH head changes compared to other algorithms

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My Contributions

• Summary of existing MAC protocols for VANETs▫  "MAC Protocols for VANETs", in Mobile Ad Hoc Networking, Cutting Edge

Directions, 2nd ed., 2013.

• A multi-channel cluster-based TDMA MAC protocol to coordinate intra-cluster communications (TC-MAC)▫ [IEEE VTP, 2012], [MP2P, 2013]

• A CH election and cluster formation algorithm based on the traffic flow and a cluster maintenance algorithm. ▫ [ON-MOVE, 2010]

• A multi-channel cluster-based CDMA/TDMA hybrid MAC protocol to coordinate inter-cluster communications▫ [IEEE Transactions on Intelligent Transportation Systems, in preparation]

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Future Work•Further Analysis:

▫The  effect of guard intervals▫Three-hop clusters▫Different data rates

•Design a numbering scheme for cluster members▫Missed update messages

•Enhance the utilization on the SCHs▫By using the un-used slots on the SCHs.

•Speed-based clustering▫Highways with different speed for each lane

•CDMA/TDMA evaluation using simulation

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Publications• Mohammad Almalag, Michele C. Weigle, Stephan Olariu, and Samy El-

Tawab, Peer-to-Peer File Sharing in VANETs Using TC-MAC, Proceedings of the International Workshop on Mobile Peer-to-Peer Computing (MP2P) San Diego, CA, March 2013.

• Mohammad Almalag, Stephan Olariu, and Michele C. Weigle, TDMA Cluster-based MAC for VANETs (TC-MAC), Proceedings of the IEEE Workshop on VANETs From Theory to Practice (VTP). San Francisco, CA, June 2012.

• Mohammad S. Almalag and Michele C. Weigle. Using Traffic Flow for Cluster Formation in Vehicular Ad-hoc Networks. Proceedings of the Workshop On User Mobility and Vehicular Networks (ON-MOVE), Denver, CO, October 2010, pp. 631-636.

• Book Chapter: Mohammad Almalag, Stephan Olariu, and Michele C. Weigle. MAC Protocols for VANETs. In S. Basagni, M. Conti. S. Giordano, I. Stojmenovic, eds., editors, Mobile Ad Hoc Networking: Cutting Edge Directions, 2nd Edition. Wiley-IEEE Press, March 2013.

• Book Chapter: Mohammad S. Almalag. Safety-related vehicular applications. In Stephan Olariu and Michele C. Weigle, editors, Vehicular Networks From Theory to Practice. Chap- man & Hall/CRC, 2009.ACM (Association for Computing Machinery).

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Thank you

Questions Mohammad Salem Almalag

Department of Computer Science Old Dominion University

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