BASE TECHNIQUES

DISTANCE COMPUTATION

In order to compute position several methods relies on computing distance between nodes, several approaches are available

time of arrival (ToA) , the distance is computed as $l i g h t s p ee d * T o A$
Received signal strength indication (RSSI) , the distance is computed by the received signal strength

position can be computed using several geometrical and non geometrical approaches:

given 2 reference points $re f_{1}, re f_{2}$ TDoA is the set of points where

$T o A (re f_{1}) = T o A (re f_{2})$

the position is determined by computing distances from 3 reference points

based on the fact that the distance between 2 reference points is known, it computes the position using the Carnot’s theorem:

\displaylines a^{2} = b^{2} + c^{2} - 2 b c * cos α b^{2} = a^{2} + c^{2} - 2 a c * cos β

The current position is determined by the closest reference point to the node, ToA or RSSI can be deployed

This is a statistical approach based on the knowledge of the deployment environment and of a dataset of observations made of it (e.g. RSSI)

this approach is composed by two phases

Preliminary phase data are collected by observation and monitoring of the environment
Operational phase environment observation are compared to the collected data to estimate position

Several things can cause error in position measurement such as: