Max. Number of Tags at One Location Area 

Number of Tags within the RTLS is theoretically unlimited, however there is a radio channel limit. 

The max. number of tags has physical limit as each Tag blink consume portion of channel time. Total channel utilization depends on tag refresh interval and selected RF profile. The lower refresh interval the more transmissions within second from each tag and thus less total number of available tags within the same vicinity. 

Note: Please keep in mind that the number of Tags calculated below applies for the multiple Tags in the same radio range (location cell). There is no limitation for total number of Tags running across the whole system.

The Tag sends blinks periodically plus a random offset through a so-called ALOHA channel access method is employed. Once more Tags are in the same radio range their positions are estimated by the same set of Anchors and if they transmit at the same time, collision occurs. In this case, position might not be calculated. Therefore, one needs to think about the channel utilization for a given application.

The table below shows the total Tag number for RF4, RF5 profiles and refresh interval. Please do not use other modes for Tags.

Calculation example: Probability of collision depends on the blink length. ALOHA access method has 18% limit where there is high probability of transmissions without collisions. Let us calculate an example where Tags have the same refresh interval 1s and RF5 profile is used. Blink time for this profile is 0.175ms. Therefore, the number of Tags within the same physical vicinity without collisions is 1028 (1000ms/0.175ms*0.18).

Once the blink message is equipped with sensor data, the utilization of the radio channel will be higher with the same RF profile and Refresh interval. The following table shows the maximum Tag number for a given RF profile and refresh interval, if the quaternions (3D orientation) are sent.