1. July 2007
doc.: IEEE p
Jan. 2010
Case Study for reduced priority management frames – Vehicular Safety Communication
Date:
Author(s):
Name
Affiliation
Address
Phone
John Kenney
VSC3 and Toyota InfoTechnology Center
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

2. DSRC – Dedicated Short Range Communication
July 2007
doc.: IEEE p
Jan. 2010
DSRC – Dedicated Short Range Communication
An FCC-endorsed vehicular communication technology based on 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
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

3. July 2007
doc.: IEEE p
Jan. 2010
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)
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

4. Example Safety Applications
July 2007
doc.: IEEE p
Jan. 2010
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)
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

5. Emergency Electronic Brake Lights
July 2007
doc.: IEEE p
Jan. 2010
Emergency Electronic Brake Lights
WIRELESS
MESSAGE
STOPPED
EEBL ALERTS DRIVER
REAR-END COLLISION
ENOUGH DISTANCE
TO STOP
WITHOUT
EEBL
WITH
EEBL
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

6. V2V Safety Communication
July 2007
doc.: IEEE p
Jan. 2010
V2V Safety Communication
Safety Apps
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
SAE J2735 message
IEEE Layer 3/4
IEEE channel switching
IEEE & p
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

7. 802.11p Communication Outside the context of a BSS No BSS setup
July 2007
doc.: IEEE p
Jan. 2010
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 p)
Management frames generally of lower priority than data frames.
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

8. July 2007
doc.: IEEE p
Jan. 2010
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 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.
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A

9. July 2007
doc.: IEEE p
Jan. 2010
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)
requirement to map management frames to AC-VO conflicts with goals of vehicular safety communication.
Kenney – Toyota/VSC3
Rai, Bai, and Kenney: VSC-A