1. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 1 Case Study for reduced priority management frames – Vehicular Safety Communication Date: 2010-1-18 Author(s): NameAffiliationAddressPhoneemail John Kenney VSC3 and Toyota InfoTechnology Center 574-272-1403johnkenney@alumni.nd.edu

2. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 2 DSRC – Dedicated Short Range Communication An FCC-endorsed vehicular communication technology based on 802.11 in the 5.9 GHz band 75 MHz allocated in the US (7 x 10 MHz channels w/ 5 MHz guard) 30 MHz pledged in Europe Japan is pursuing similar technology

3. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 3 Applications Primary applications are safety – collision prevention and mitigation Secondary applications include –Mobility (traffic, navigation, in-vehicle signage, eco-driving) –Tolling –Commercial (retail advertisements, Internet access)

4. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 4 Example Safety Applications Vehicle-to-vehicle communication (V2V) –Forward Collision Warning –Emergency Electronic Brake Lights –Do Not Pass Warning –Blind Spot Warning –Intersection Collision Avoidance Vehicle-to/from-Roadside Infrastructure (V2I) –Intersection Collision Avoidance based on intersection messages: Geographic Intersection Description (GID) Signal Phase And Timing (SPAT)

5. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 5 Emergency Electronic Brake Lights WITH EEBL WITHOUT EEBL WIRELESS MESSAGE STOPPED EEBL ALERTS DRIVER REAR-END COLLISION ENOUGH DISTANCE TO STOP

6. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 6 V2V Safety Communication Relies primarily on frequent broadcasts by each vehicle of important state info, including: –Position –Speed, acceleration, heading –Brake and stability status –Vehicle size –Recent path history –Predicted path –Special event flags –GPS corrections See SAE J2735 Message Set Dictionary standard Safety AppsIEEE 802.11 & 802.11p SAE J2735 message IEEE 1609.3 Layer 3/4 IEEE 1609.4 channel switching

7. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 7 802.11p Communication Outside the context of a BSS No BSS setup No beacon, probe, authentication, association, … Management frames most likely in DSRC are: –Vendor Specific Action frame (will be used for a variety of purposes, including advertising services on other DSRC channels) –Timing Advertisement frame (defined in 802.11p) Management frames generally of lower importance than data frames. Would like to be able to send with lower priority.

8. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 8 Performance Concerns Packet delivery rate in dense, fast-moving traffic Example: –3 kbit safety message –10 messages per vehicle per second –20 vehicles per lane per km –Communication range +- 500 meters –10 MHz channel, 6 Mbps OFDM –10 lanes x 20 Veh/lane/km x 30 kbit/veh/sec x 1 km = 6 Mbps Realistic traffic saturates channel. High collision rate.

9. doc.: IEEE 802.11 11-10-0095-00-00ae Submission Jan. 2010 Kenney – Toyota/VSC3Slide 9 Access Priority Channel dominated by vehicle safety messages (data frames) Most vehicle safety messages are routine –Occasional event content raises importance –Sender not always aware when content is critical for collision avoidance Channel is shared with other traffic, including management frames (VSA, TA) 802.11 requirement to map management frames to AC-VO conflicts with goals of vehicular safety communication.