The advantages of a directional antenna with high gain are best exploited in large open areas. Below are shown several practical examples of such deployments, which would be very hard to realize using purely omnidirectional antennas.
Generally, the anchors with omnidirectional antennas have the disadvantage that the maximum grid of physical installation is 15×15 meters. If the anchors are put beyond this distance, they lose synchronization between each other and also the signal quality from the tags is severely degraded. Directional antennas let you have a much bigger space between the anchors with the same performance as in smaller spaces.
An open environment free of obstacles
In such an open environment, the anchors can be deployed as far away as possible. The anchors need to be oriented diagonally towards each other.
This case represents an ideal case (no obstacles, clear LoS) with one location cell containing 4 anchors. The antennas need to be oriented diagonally facing each other to achieve a good synchronization in the cell.
This is a similar case as the first one containing two location cells next to each other. There are 4 anchors per each cell, expanding the total area covered.
Because of the nature of the TDoA algorithm, the performance is decreased on the edges of the Location Area. In order to eliminate this, it’s best to use the anchors’ longer range and put them outside of the area where you wish to track. That way, the tags basically never reach the borders and the performance is stable.
A Livestock barn
In this open-area scenario with one much larger side than the other, you can stack multiple location cells next to each other.
Keep in mind though that the dimensions of the location cells should not exceed a 1:2 ratio, otherwise the accuracy may be decreased in the shorter axis (X axis in this case).
An industrial environment
In large open environments, the anchors can be also installed in the middle and form several location cells next to each other.
In the middle, four anchors need to be used around the column because of the directivity of the antenna.
A real example from an installation with anchors next to each other facing opposite directions can be seen on picture bellow.