Understanding Geo Location Coordinates

The geo location agent builds an AP graph for each floor plan to which APs are assigned, based on the FTM AP to AP ranging results. The edges of the graph are the measured distances between the APs using the 802.11mc protocol. The AP graph location on the map depends on the geolocation reported by the anchor APs.

The following conditions must be met before the geo location agent can derive coordinates for APs on the floor:

• AP Graph Connectivity: Each AP on the floor must be able to determine the FTM distance to a minimum of three neighboring APs.

  If the AP Graph Connectivity requirement is not met for all the APs on the floor, the geo location agent creates several Sub-Graphs. Each Sub-Graph includes a subgroup of APs.

• Number of anchor APs: The AP Graph must be connected to a minimum of four anchor APs, with only one Sub-Graph per floor supported.

The APs belonging to Sub-Graphs might have geo location coordinates assigned. See the following scenarios and recommendations for corrective actions.

Sub-Graphs Scenario Examples

Sub-Graph-1(Clique-1)

The group of APs belonging to Sub-Graph-1 satisfy the AP Graph Connectivity and the Number of anchor AP requirements. As a result, the geolocation agent derived coordinates for each of them.

No corrective action required.

Sub-Graph-2(Clique-2)

The group of APs belonging to Sub-Graph-2 satisfy the AP Graph Connectivity but not the Number of anchor AP requirements. As a result, the geolocation agent did not derived coordinates for these APs.

Corrective actions:

• Install more USB-GPS dongles to satisfy the Number of anchor APs requirement for this Sub-Graph.
• Alternatively, install more APs between Sub-Graph1 and Sub-Graph2 to add more connections between the sub-graphs and merge them.

Sub-Graph-3(Clique-3)

When the AP Graph Connectivity rule is not met, but the Number of Anchor APs requirement is met, geolocation coordinates are not derived. Take the following corrective action:

Reposition the APs, or install more APs, to achieve connectivity with the rest of the APs on the floor.

Sub-Graph-4(Clique-4)

When neither requirement is met, geolocation coordinates are not derived. Take the following corrective actions:

• Install more USB-GPS dongles to satisfy the Number of anchor APs requirement for this Sub-Graph.
• Alternatively, reposition the APs or install more APs to achieve connectivity with the rest of the APs on the floor.