1. OKI Project - Phase 2 Simulator Development Overview Department of Electrical and Computer Engineering The Ohio State University August 2004

2. 2 Topics Overview Wireless simulator Physical layer modeling Traffic and driver behavior simulator Next steps Demonstration

3. August 20043 Overview Advance the simulators developed for OKI phase 1 Incorporate new features/considerations –Wireless simulator [Alberto Avila] Multiple transmissions, retransmission interval, repeater Real-time interface with vehicle traffic simulator –Physical model [Heelim Teh] Incorporate modulation, reflection, blockages, and shadowing –Intelligent transportation system (ITS) [Yiting Liu] Real-time interface vehicle traffic simulator with wireless simulator Collision warning system implementation Driver behavior model implementation

4. August 20044 Offline Wireless Simulator Objective: Accurate representation of broadcast medium performance Based on protocol and physical specifications Incorporate physical layer to determine path loss and frame error rate Flexibility on scenario parameters: MAC protocol [Dolphin; 802.11 a;b;a R/A] Building location Repeater presence Initial data transmission distance Transmission interval Maximum number of retransmissions Retransmission interval

5. August 20045 Offline Wireless Simulator Dolphin protocol (CSMA) [Phase 1] Multiple transmissions within area Retransmissions within interval [5] Physical specification [Phase 1] Transmit power [10 dBm] Receiver sensitivity [-82 dB] Repeater Single retransmission Initial data update Data update interval Repeater [single retransmission] Transmission intervals Retransmission attempts

6. August 20046 Statistical information: - Packet collision probability - Vehicle density - Frame error rate - Latency Statistical information: - Packet collision probability - Vehicle density - Frame error rate - Latency Trace files: - Vehicle information - Vehicle position - Vehicle velocity Offline Wireless Simulator Vehicle Traffic Simulator Input Parameters: - Vehicle density - Vehicle throughput - Transmission interval Physical layer model Statistical information: - Packet collision probability - Vehicle density - Frame error rate - Latency Multiple scenarios with different input parameters Offline Wireless Simulator

7. August 20047 Offline Wireless Simulator Simulation data available: Vehicle packet collision rate Base station packet collision rate Vehicle density Out of range average Frame error rate Coverage rate Delivery rate

8. August 20048 Online Wireless Simulator Objective: Provide packet transmission success determination Low latency Incorporate physical layer to determine path loss and frame error rate Why? Offline simulator is computation, memory intensive CSIM is event driven, virtual time scale

9. August 20049 Online Wireless Simulator Functionality: Estimate collision rate probability for specific scenario parameters and vehicle conditions Low latency response (< 200 msec) Encapsulate data from offline wireless simulator Handle a variety of simulation scenarios: Intersection type (signal/no signal) Repeater Building Transmission interval; retransmissions

10. August 200410 Vehicle Traffic Simulator Packet Generator Collision Warning System Allows real-time feedback to the vehicle traffic simulator. This, in turn, enables driver behavior to be affected by information received from other vehicles through the online wireless simulator. Communication protocol Protocol parameters Scenario parameters Vehicle density Vehicle positions Vehicle sources Receiver vehicle Source vehicle Reception time Online Wireless Simulator Driver Behavior Online Wireless Simulator Offline simulator data - Density - Distance - Interval -.... Physical layer model

11. August 200411 Wireless Simulation Results No signal, low throughput Signal, med/high throughput

12. August 200412 Physical Layer Offline Wireless Simulator Physical layer model Leveraged by both offline and online wireless simulators Online Wireless Simulator Offline simulator data - Density - Distance - Interval -.... Physical layer model

13. August 200413 Objective: Provide a simple and accurate channel model for the Dedicated Short Range Communications (DSRC) in an urban environment Determine path loss, frame error rate Functionality: Flexibility for different physical environments and conditions: Buildings Repeater Vehicle types Physical Layer

14. August 200414 Scenario Setup TX RX1 Building RX4 RX3 RX2 Sidewalk

15. August 200415 Line-of-sight communication: - TX↔RX2, TX↔RX3 No-line-of-sight communication: Shadowing caused by other vehicles on the street: - TX↔RX4 Blockage caused by building at the corners: - TX↔RX1 Possibilities

16. August 200416 When the source and the destination vehicle have a clear, unobstructed communication. For example, between TX and RX2, RX3. I can see you, too! I can see you! Line-of-Sight Line-of-sight Communication

17. August 200417 When there is line-of-sight, the received power is mainly contributed by the direct path and the reflection. Two-ray Model Direct path r t h0h0 Distance: r Reflection path r r htht hrhr Virtual reflection surface

18. August 200418 Path Loss [1] r t : distance between TX ant. and RX ant. = r r : reflection path length from TX ant. to RX ant. = R: reflection coefficient. k: wave number. h t : TX antenna height. h r : RX antenna height. h 0 : virtual reflection surface height. [1]: Y. Oda, K. Tsunekawa and H. Hata, “Advanced LOS path loss model in microcellular mobile communications”, IEEE Trans. Vehicular Technology, vol. 49, (6) pp.2121-2125, Nov. 2000 Two-ray Model

19. August 200419 Virtual Reflection Surface [h 0 ] Due to different traffic densities and street characteristics, reflected ray does not necessarily come from the ground. Each h 0 corresponds to a specific traffic density and street characteristic. To get h 0 : –Collect field test results. –Compute the free space propagation path loss. –Use the difference between the above two and the two- ray path loss equation to computer h 0.

20. August 200420 When there are large obstacles between the source and the destination vehicles, the line-of-sight communication is obstructed. Communications between TX and RX1, RX4. ??? Where are you? Obstacle No-line-of-sight Communication

21. August 200421 TX RX4 d1d1 d2d2 h α RX2 For modeling shadowing effect. Ex., TX ↔ RX4 Fresnel integral: [2] where the Fresnel-Kirchoff parameter ν = Knife Edge Model [2] T. S. Rappaport, Wireless Communications. New Jersey: Prentice Hall, 2002

22. August 200422 Knife Edge Model 1 ≤ ν ≤ 2.4 ν ≤ -1 -1 ≤ ν ≤ 0 0 ≤ ν ≤ 1 ν > 2.4 Ld(ν) =

23. August 200423 Finding a virtual source located in the line-of- sight with both the transmitter and receiver. Virtual Source Model TX r rsrs wsws VS RX1 x Building

24. August 200424 Path loss (dB):, r ≤ r b, r > r b, where Virtual Source Model

25. August 200425 Vehicle Traffic Simulator Message Generator Collision Warning System Driver Behavior ITS Components Vehicle traffic simulator (VTS): Simulates traffic network and intersection behavior Message generator Sends messages when vehicles cross specific borders Collision warning system Generates warning message based on received information Driver behavior module Simulates individual vehicle’s response to various warning messages

26. August 200426 Vehicle Traffic Simulator Traffic Flow Characteristic Input Scenario Input Vehicle Management Road Traffic Light Management

27. August 200427 Simulation Setup Screen Scenario Input Traffic Flow Characteristic Input

28. August 200428 Vehicle Management Turning Normal Driving Vehicle Following Vehicle Management Driver information: Its own speed Its own position data from DGPS Turning direction Other vehicles in Line-of-sight and the estimated distance and speed Status of traffic lights

29. August 200429 Traffic Light Management Scenario Input Cycling Time Direction Status Cycling Time ( Two Phase): G=25sec; Y=5sec

30. August 200430 Message Generator Initial data update Data update interval Predefined Transmission Set: Initial data update Data update interval Retransmission times Send messages when vehicle crosses data update interval borders Retransmissions

31. August 200431 Collision Warning System Three level warning system:  Warning level 1-- ELEVATED Danger ahead; Need to decelerate  Warning level 2-- HIGH Moderate danger ahead; Decelerate immediately  Warning level 3--SEVERE Critical situation; Severe danger ahead Stop immediately Collision probability

32. August 200432 Collision Warning System Time-to-collision (TTC): –The time required for two vehicles to collide if they continue at their present speed and on the same path –The lower the TTC, the higher the collision risk Time-to-avoidance (TTA): –The required stopping distance time R: relative distance : : relative velocity l i : Vehicle i’s length along the route contention  : Speed reduction parameter If 1, then full stop μ: Friction coefficient

33. August 200433 Collision Warning System Get communication data Compute route contention If no route contention –No warning Else –Compute TTC and TTA –If TTC >= TTA+ driver’s response time (1.93 s -2.53 s) If deceleration>=TTA deceleration –No warning Else if deceleration < TTA deceleration –Warning level 1 Else if no acceleration –Warning level 2 Else (acceleration) –Warning level 3 Else –No warning

34. August 200434 Effects of Collision Warning System Animation of Intersection warning system Intersection Collision Scenario

35. August 200435 Driver Response Module Aggressive driver: – Only response to warning level 3 – Initial accelerator release only Normal driver: – Response to both warning level 3 and level 2 – Braking to warning level 3 – Decelerate slowly to warning level 2 Conservative driver: – Response to all the warnings – Braking to warning level 3 and warning level 2 – Decelerate quickly to warning level 1

36. August 200436 Next Steps General –Evaluate QoS for collision avoidance application Wireless simulator –Improve correlation of scenario and traffic conditions to collision rate probability –Incorporate different types of traffic for multiple intersection applications Physical layer –Incorporate configurable modulation type –Handle various obstacle types Traffic simulator –Improve collision warning system –Provide a more detailed driver model