VANET Applications Use-Cases

Transcription

1 VANET Applications Use-Cases VANET communications (V2V and V2I) can be used for dozens of potential applications with highly diverse requirements. Below we identify the most representative VANET applications and analyze their requirements through use-cases. 1. Assist driver with signage 1.1. Traffic Signal/Stop Sign/Rail Crossing Violation Warning Use Case Goal Preconditions Involved components (any logical components both h/w and s/w involved in application implementation Traffic Signal/Stop Sign Violation Warning Warn the driver that he/she is about to violate a traffic signal prescribing a stop (red light, flashing red light, stop sign, rail road crossing etc.). 1.Traffic light/stop sign/rrc (an instance of infrastructure) is equipped with DSRC devices capable to communicate their location, status, and timing 2. Traffic light/stop sign/rrc (an instance of infrastructure) communication system is operational (up and running) 3. Vehicle communication system, computing devices and information processing units are operational 4. Communication link between the traffic light/stop sign/rrc can be established pieces of information source of components Traffic signal status and timing information Traffic light controller Controller circuitry with parameters such as 1. Type (e.g. 3-state, 4-state, dedicated permissive or protective) 2. Signal phases, their sequence and duration of cycles (phases φ1 φ1 can be used to determine the directions controlled with respect to the heading) 3. splits, gaps, offsets and their characteristics

2 Participants Success End Condition Failed End Condition Traffic signal or stop sign stopping location Distance from the car to the stopping location and the s direction Traffic light controller (normally 4 cycles, 4 splits and 3 offsets define all possible plans of operation) 4. Time-of-Day or Traffic Responsive Settings 5. Preemption capability and schedule (e.g. smooth, dwell, add only, etc.) GPS location of the intersection controlled by a traffic light controller GPS + sensors + software capable of calculating estimated time to the sign given its GPS coordinates and data from the sensors (speed, acceleration, heading) Type of road surface Either sensors (how bumpy the road is) or digital map (if detailed enough to include this information) Weather conditions Either sensors (wipers activity, traction control, outside thermometer, etc.); if not available/reliable, weather information can be updated/requested by an application via DSRC Type of brakes and their characteristics (sensitivity) Read-only data sitting on the bus; readily available and not requiring computation 1. Traffic light controller (circuitry controlling the intersection, i.e. not individual light plates) 2. Vehicle a. Has preemption authority (ambulance, fire truck, police car) b. Regular 3. Warning is issued to the driver 4. Warning is aborted (only in case of traffic light): a. if calculations indicate the distance is safe provided that the traffic light is about to change to green b. if established that it was the wrong traffic light (perpendicular to the heading of the, down below the bridge, etc.) Warning is not issued to the driver 1. Communication ure a. communication dropped b. message cannot be processed c. message cannot be verified or there is a property violation (cannot verify it was sent by a stop sign etc.)

3 Trigger Operation description 2. Sensor ure/ambiguous data a. location (GPS), speed, acceleration, heading 3. Software ure a. unable to complete computation b. unable to complete computation within time constraints 4. Other A beacon broadcasted from the traffic light/stop sign/rrc is received within the communication range. 1. When within communications range, a car receives a beacon broadcasted from the infrastructure signage (traffic signal, stop sign, or RRC). 2. Upon receipt, this information is processed for relevance (distance and heading) and validity (authentication and property check). 3. Calculations are carried out to estimate braking distance given information received from the infrastructure, collected from the sensors and GPS. 4. If estimating location of a complete stop is ahead (based on heading) of the stopping point broadcasted by the traffic sign/stop sign and the timing of the traffic sign indicates it will be orange/red when the will be crossing the stopping point, a warning message is issued. 5. Otherwise the warning is aborted Safety relation Not safety related Safety relevant In-car system Driver Involvement Communication x Safety critical C2C C2I x I2C x One-way x Two-way x Unicast x Broadcast x Timing Timing constraints 1 sec Periodically sent x Security Requirements Authentication ID required Location required Property required Integrity Required Confidentiality Not required Privacy ID required Location Not required Other?? Auditability Required Threats Motivation Joke, harm Target Vehicle safety Attacker s skill Low - high Technical effort Wireless access to car or road side unit, manipulate sensors, disable traffic signs The following communication patterns are anticipated for this application: x

4 Case 1: Asynchronous broadcast from a stationary node (traffic light controller) to all mobile nodes (s) in the transmission range within the intersection controlled by a traffic light controller. The information broadcasted will include minimal amount of information sufficient for determination of stopping distance such as GPS coordinates, current cycle, cycle length, phasing, etc.) Advisory decision is not solely based on the traffic light current cycle in the direction coinciding with the heading (i.e. green light might not be enough). Stopping distance and time are calculated based on the sensor values (weight, acceleration, position) adjusted for weather conditions (wind, road surface). If the current cycle is go, the stopping time will be compared to the duration of the current cycle to assert the cycle will not change to stop without allowing enough time for the to come to a complete stop. If the current cycle is stop, the stopping distance will be compared to the distance to the intersection (or prescribed location to stop) authenticate pass relevant pass yes determine relevance verify integrity determine if need to advise to stop issue warning broadcast message (location, phase, cycle, etc.) irrelevant no discard traffic light controller (intersection)

5 Case 2: Synchronous unicast from/to a stationary node (traffic light controller) to a privileged mobile node in case of preemption is needed. In this case, the normal traffic light cycle is suspended and replaced by the preemption sequence supported by the traffic light controller (smooth, dwell, add only) followed by resumption of the normal traffic light cycle. It should be noted that the latest regulations prohibit all red cycle for preemption. Preemption procedures are internally handled by the controller circuit logic(e.g. how much time is allocated per phase in preemption mode, split distribution, delay and response time are defined out of the scope of this application). Priority of preemption (two or more distinct emergency s are approaching the intersection) might or might not be handled by the traffic light controller and may need to be handled separately (proximity based). Irrespectively of whether or not an emergency cleared the intersection, the traffic light controller will exit preemption mode unconditionally after preemption sequence is complete (even thought preemption requests are queued, upon completion of the preemption phase, the normal regime of operation is always enforced prior to handling the next request). priveleged request preemption authenticate request right of the way message log for audit discard preemption success message succeed issue success/ proceed with causion message traffic light controller (intersection) irrelevant message broadcast as defined in case 1 authenticate pass determine relevance relevant trigger preemption issue ACK succeed trigger rebroadcast Security requirements for the above communication patterns include:

6 1. authenticity of the received messages including assertion of certain attributes and rights (make sure that a message indeed comes from a traffic light or an authorized emergency response ) 2. anonymity (make sure that identities of the communicating parties are not disclosed). 3. integrity (make sure replay attacks are prevented)