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

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

August 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

August 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; a;b;a R/A] Building location Repeater presence Initial data transmission distance Transmission interval Maximum number of retransmissions Retransmission interval

August 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

August 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

August 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

August 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

August 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

August 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

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

August 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

August 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

August Scenario Setup TX RX1 Building RX4 RX3 RX2 Sidewalk

August 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

August 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

August 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

August 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 , Nov Two-ray Model

August 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.

August 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

August 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

August Knife Edge Model 1 ≤ ν ≤ 2.4 ν ≤ ≤ ν ≤ 0 0 ≤ ν ≤ 1 ν > 2.4 Ld(ν) =

August 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

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

August 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

August Vehicle Traffic Simulator Traffic Flow Characteristic Input Scenario Input Vehicle Management Road Traffic Light Management

August Simulation Setup Screen Scenario Input Traffic Flow Characteristic Input

August 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

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

August 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

August 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

August 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

August 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 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

August Effects of Collision Warning System Animation of Intersection warning system Intersection Collision Scenario

August 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

August 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