Vehicle to Vehicle Communications (V2V)

26th February 2020

In 2017 the US government requested comments to build a V2V standard see here . The benefits being that other vehicles can communicate their state, intentions, observed road conditions, etc BETTER than vehicle resident technologies that rely on line-of-sight. Their recommendation was to use the 6Mhz frequency which would require special radios, and have VERY limited data bandwidth. And be susceptible to HALL effect.

My recommendations and some description why:

Use LoRa 1km/50Kbps And/OR Bluetooth 4+ class 2 ~10m/3Mbps or class 1.5 ~20m Uses currently developed technology. Will require antenna to increase range. Allows rapid prototyping on Raspberry Pi 0w. No custom hardware.

Allows integration and expandibility; + camera = dashcam, possibly lane departure alerting, bad driver reporting, find stolen vehicles by plate#. +Carbon Monoxide detector +OBD2 integration = self diagnostic, good driver reporting +wifi=auto update, data upload. Multiple cameras/mirrors = blind spot detection.

Low cost of entry; Manufacturers can wire USB power near rear view mirror and leave rest to customer. RasPi0w $10 + Camera $10 + ODBC module $15 + LoRa hat $25

Government writeup recommended 2 algorithms to start with; Intersection Movement Assist (IMA) and Left Turn Assist (LTA)

IMA; possible algorithm;

V2V vehicles beacon their plate # to determine who is present. Signals to non-V2V vehicles; Switch between running lights and low beam (OR 4way flashers? Red/Y/Green leds behind RV mirror=easiest to implement) V2V vehicles compare 1st to 0kph. tie=play Rock/Paper/Scissors. Winning vehicle changes to low beam lights and proceeds.

LTA; possible algorithm;

Listen for speed of oncoming V2V vehicles. Refer to history if you have enough time to proceed given safety margin of ? 2 vehicle lengths? 10%? Is temperature below 1degC? +10%sm, have you or other V2V vehicles reported traction control past 1hr? +10%sm

What to beacon? plate#/VIN# = unique ID last 7 digits=49bits. speed 5kph increments 0-150kph 32options=5bits, Acceleration +3 hard accel to -3 hard brake -4=wheels locked still moving 4bits, turn signal status 0=off 1=left 2=right 3=4way 2bits, traction control engaged/road debris last hour #times 2bits , direction N/S/E/W 2bits, Transmission 0=park 1=reverse 2=fwd 3=cruise control engaged 2bits , (66bits total) GPS is typically 24bits but this can be reduced seeing as it is physically impossible to communicate with a vehicle in a different hemisphere (most of the time) LoRa has a max packet size of 255bytes(2040bits)/ sf12 max is 51bytes(408bits) , header=13bytes(104bits) =104+90

City/County police provide a list of no more than 100? of each item to find; Licence plate #’s, Wireless MAC addresses, Bluetooth MAC addresses, QR codes. Why? a find list allows versitility to emergeny services without privacy concerns of broadcasting every plate#.

OBD2 relevent info:

Service 1

0D 13 1 Vehicle speed 0-255km/h

0F 15 1 Intake air temperature -40 215 °C

11 17 1 Throttle position 0-100%

2F471Fuel Tank Level Input0100%

33511Absolute Barometric Pressure0255kPa

A41644Transmission Actual Gear

A61664Odometerhm

Service 09

0217Vehicle Identification Number (VIN)17-char VIN, ASCII-encoded and left-padded with null chars (0x00) if needed. ea ASCII char=7bits x17=119bits

Additional sensors required:

Accelerometer; to determine braking level

Compass

Microphone? turn signal status, horn

? Antilock & traction control status