i ∈ {1,…, l}	: an index in a labeled training dataset when a target is located at l different locations
yXi ∈	: the i-th target location in X coordinate
yYi ∈	: the i-th target location in Y coordinate
zij ∈	: an RSSI measurement of j-th sensor node corresponding to the i-th target location yXi, yYi
ri = {Zi1,…, Zin} ∈ n	: an RSSI observation set collected from all n sensor nodes
${\left\{r_i,y_{\text{X}i}\right\}}_{i=1}^l$	:a labeled dataset for X coordinate
${\left\{r_i,y_{\text{Y}i}\right\}}_{i=1}^l$	: a labeled dataset for Y coordinate
${\left\{r_i\right\}}_{j=1}^u$	: an unlabeled dataset with the number of u data points
fX (r → yX) :	the function mapping an RSSI measurement set r to X coordinate position
fY (r → yY) :	the function mapping an RSSI measurement set r to Y coordinate position.