1 TDMA Slot Reservation in ClusterBased VANET Ph

1 TDMA Slot Reservation in Cluster-Based VANET Ph. D. Gathering By Mohammad S. Almalag Advisor Michele C. Weigle Department of Computer Science Old Dominion University Norfolk, VA 11/17/2011

2 11/17/2011 Introduction Vehicular Ad-Hoc Network (VANET): ▫ Increase traveler safety ▫ Decrease traveling time and fuel consumption ▫ Increase on board luxury

3 11/17/2011 Introduction Applications categories: • Safety • Non-safety q Co-operative Collision warning [V-V] q Traffic Information q Intersection Collision Warning q Data Transfer q Approaching Emergency Vehicle q Parking Lot Payment q Work Zone Warning [R-V] q Electronic Toll Collection

4 11/17/2011 Introduction Dedicated Short Range Communication (DSRC) channels:

5 11/17/2011 Introduction IEEE 1609. 4 standard:

6 11/17/2011 Problem • Safety messages requirements ▫ High reliability ▫ Every 100 msec Non-Safety messages almost shut down [Wang, ACM VANET 2008] Low Medium Traffic Density High

7 11/17/2011 Objective The main objective: ▫ Allow vehicles to efficiently exchange both safety and non-safety messages while meeting safety message requirements

8 04/27/2011 TDMA Time Division Multiple Access (TDMA) is a method used to enable multiple nodes to transmit on the same frequency channel.

9 11/17/2011 TDMA Assignment Assumptions: Clusterhead based clustering scheme One transceiver on-board vehicles are equipped with GPS 1 CCH (cch) 6 SCHs (k) N vehicles τ is the slot size in SCHs a mini-slot on the control channel to contain at least 64 bytes; (i. e. assuming k=6, this implies a slot size of 384 bytes)

10 11/17/2011 TDMA Assignment

11 11/17/2011 TDMA Assignment • Each vehicle in the cluster will receive a local ID (from 1 to N). • The CH will have always ID 1. • ID 0 is reserved for a “virtual vehicle”. • In each logical frame vehicle j, owns: ▫ channel j mod k during time slot ; we also say that vehicle j owns the ordered pair ▫ The j-th mini-slot of slot mod on channel cch

12 11/17/2011 TDMA Assignment SCH: (39 mod 6) = 3 During slot • Example: And CCH: 4 th mini-slot in slot 6 -1=5 ▫ Number of vehicles N = 61, k = 6, vehicle j’s ID= 39

13 11/17/2011 TDMA Assignment ▫ Notice that the Integer Division Theorem guarantees that if i ≠ j then either: or i mod k ≠ j mod k, or both

14 04/27/2011 Intra-cluster Communication • Lightweight communication protocols • Each vehicle uses its own mini-slot to disseminate safety beacons • First byte, 28 = 128 different situations.

15 04/27/2011 Intra-cluster Communication Example: 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 vehicle in the cluster. (multicast group) 125 : confirmation of “Hello” message. 126 : vehicle will transmit a request during its upcoming slot (i. e. , next slot). 127 : vehicle will use its upcoming slot to transmit.

16 04/27/2011 Intra-cluster Communication Disseminating intra-cluster safety /governance messages: ▫ Emergency messages: Disseminated by CH. 127 for broadcast N-bit vector for subset ▫ Cluster control messages: Disseminated by CH

17 11/17/2011 Intra-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: Set up without CH intervention. Big group of vehicles: Set up with CH intervention.

18 11/17/2011 Inter-cluster Communication Vehicle-to- Infrastructure (V 2 I): 17

19 11/17/2011 Questions

20 04/27/2011 Cluster maintenance Cluster topology changes: ▫ ▫ ▫ CH leaving the cluster. A new vehicle joining the cluster. A cluster member leaving the cluster. Two single hop clusters get in range of each other. A multi-hop cluster shrinks into a one-hop cluster.