1. ABSTRACT Currently, drivers must utilize a third-party, such as a radio or broadband device, to learn about local traffic conditions. However, this information is often out of date by the time it reaches a driver, and the area covered by such services is often limited. The fastest and most efficient way to transmit information about road conditions to drivers would be to create vehicle-to-vehicle wireless networks. This way, cars can freely share information with each other in real-time, allowing drivers to be more aware of the current conditions. This project demonstrates the capabilities and potential impact of vehicle-to-vehicle networks. It uses modified versions of existing WiFi technology and the emerging Wireless Access in the Vehicular Environment (W.A.V.E.) family of protocols, operating between 5.85GHz and 5.925 GHz. W.A.V.E. is currently proposed through draft amendment IEEE 802.11p. The system detects specific events from the existing computer systems in a Toyota Prius and communicates this information wirelessly to nearby drivers. A GPS receiver is also used to provide accurate location and timing synchronization to within 20 μs. Information received from other vehicles is selectively displayed to the user, and in emergency settings a tone is generated to ensure that the driver can react quickly enough to avoid a dangerous situation. Location Division Multiple Access (LDMA) was implemented to allow for multiple vehicles to transmit without message collision. We were able to successfully demonstrate the generation, retransmission, and reception of event information, triggered from both simulated and real events in the vehicle. AUTHORS : Andrew Avrin CTE ’09 Brandon Duick EE ’09 Daniel Lustig EE ‘09 ADVISOR: Dr. Rahul Mangharam DEMO TIMES: Thursday, April 23 rd, 2009 10:30 AM 1:30, 3:00, 3:30 PM GROUP #17 Department of Electrical and Systems Engineering UNIVERSITY OF PENNSYLVANIA Vehicle-to-Vehicle Communication Platform IN-VEHICLE UNIT The in-vehicle unit is composed of three subsystems: a networking element (the router), an interface to the vehicle’s existing computers and sensors (the controller), and a graphical display. The operational flow of the unit is seen below. To detect events the unit takes advantage of the controller-area network (CAN) bus which allows for communication among the various control units in a Toyota Prius. This bus is accessible through the on-board diagnostics port found above the driver’s right knee. The controller analyzes the messages on the bus, and if it is determined that a safety related incident has occurred, it notifies the router so that an alert can be broadcast to other drivers. RESULTS Hardware SetupOverview of PartsExample GUI The value of the RSSI, or Received Signal Strength Indicator, shows that even as the signal strength drops, the number of packets successfully received remains high. NETWORKING SPECIFICATIONS When an incident or an event is detected from within a particular vehicle, it is immediately transmitted to any other vehicles within range. Nearby vehicles then retransmit this information if it is determined to still be relevant. The scheme used to prevent transmissions from colliding is Location Division Multiple Access, or LDMA. The map is divided into a grid, and a vehicle may only retransmit a message it receives within a particular time window, determined by its position within the grid. However, since it is important for the vehicles nearest to an incident to be informed as quickly as possible, this scheme is only employed for retransmissions. The image on the left represents LDMA implemented only as a function of latitude. The image on the right represents LDMA implemented in two dimensions. Each color represents a particular time window for transmission. Two specific messages that are found on the bus are shown in the table below. As an example, the controller can check for a sudden halt by monitoring the latest speed and the last known brake strength. The router combines the vehicle-state information with GPS data to form a WiFi packet. This packet is transmitted at 5.9 GHz, according to the IEEE 802.11p W.A.V.E. standard. Other vehicles receive these packets, and determine based on the message contents and the local GPS data whether or not to notify the driver. MESSAGE PROPAGATION The above diagram shows how a message is propagated and processed between three cars. When a car receives a new message which is still relevant, it notifies the driver and retransmits that message to other cars in range. When it receives a duplicate message, it does not notify the driver or retransmit it. ID#Description Brakes0x030 Byte 4: Strength: 0x00=out, 0x7F=full brake Speed0x3CAByte 2: Speed in km/h Timing Synchronization between Units 20μs Time from Event Occurrence to Notification of Driver in Area ~30ms