Enhanced dead reckoning method
View Patent ↗An enhanced dead reckoning method determines the position of a participating vehicle. The participating vehicle is unable to receive signals from global positioning satellites. The position is calculated by way of observed time difference calculations and received signal strength indications. The position is also calculated by communicating with other participating vehicles or egress points.
1. A method for determining the position of a first vehicle, comprising the steps of:
estimating a position of the first vehicle according to a dead reckoning method;
receiving a data packet from an apparatus via a WiFi radio communication link, wherein the position of the apparatus is known;
deriving a signal to noise ratio for the packet received at the first vehicle position and calculating a proximity of the first vehicle location to the apparatus location based on the magnitude of the signal to noise ratio;
refining the first vehicle position estimate based on the calculated proximity.
2. The method of claim 1 , wherein a fixed egress point comprises the apparatus, and wherein the egress point is located near a roadside.
3. The method of claim 2 , wherein the Wifi radio communication link is established between:
a first WiFi radio on the first vehicle that comprises a first dipole antenna, wherein the first dipole antenna points approximately toward a front end of the vehicle; and
a second WiFi radio located at the position of the apparatus that comprises a first directional high gain antenna and a second directional high gain antenna, wherein the first and second antennas point in a first and a second direction of traffic flow.
4. The method of claim 2 , further comprising the steps of:
measuring, at the first vehicle, a received signal strength indication (RSSI) of a signal from the apparatus;
creating a query packet comprising the RSSI;
transmitting the query packet to the apparatus;
calculating a distance between the first vehicle and the apparatus based on pre-generated terrain calibration data for the egress point; and
further refining the first vehicle position estimate based on the calculated distance.
5. The method of claim 4 , wherein the terrain calibration data are pre-generated using field measurements and post-processing simulations using wave-propagation tools.
6. The method of claim 2 , wherein the WiFi radio communication link is established via an enhanced IEEE 802.11 infrastructure mode.
7. The method of claim 1 , wherein a second vehicle comprises the apparatus.
8. The method of claim 7 , wherein the WiFi radio communication link is established via an enhanced IEEE 802.11 ad-hoc mode.
9. The method of claim 1 , further comprising the steps of:
assuming that the first vehicle and the apparatus are on a road; and
using data from a database representation of the road to further refine the position estimate for the first vehicle.