The latency is built up out of different aspects;
- The measurement interval; The interval the SENSIT sensor verifies it status changed, default set at 1 second.
- The overdrive filter; The overdrive delay set in the SENSIT sensor is by default set at 8 seconds.
- The number of hops; The number of hops a message needs to arrive at the Data Collector, every hop takes about 2 seconds.
- Passive collisions; In a busy car park multiple SENSIT sensors want to transmit their status change message simultaneous, which might create passive collisions. In order to reduce this we advise to ensure that each SENSIT sensor can at least communicate with 2 Relay Nodes offering multiple communication paths.
Example with default settings and without passive collisions:
The magnetic and optical sensor measures every second if the status of the bay is changed. The overdrive filter waits 8 seconds before it transmits the event. In this example the event is transmitted via 2 Relay Nodes; first from the SENSIT to the nearest Relay Node and then from this Relay Node to the Relay Node close to the Data Collector and finally from this Relay Node to the Data Collector. The total (worst-case) time needed is: Measurement + overdrive + SENSIT -> RN + RN -> RN + RN ->Data Collector = 1+8+2+2+2 = 15s
Example with default settings and with one passive collision:
The magnetic and optical sensor measures every second if the status of the bay is changed. The overdrive filter waits 8 seconds before it transmits the event. In this example the event is transmitted via 2 Relay Nodes; the sequence of transmitting the messages is the same as in the example above but now a collision occurred in the first transmission; another SENSIT transmitted an event at the same time to the Relay Nodes. The total (worstcase) time needed is now: Measurement + overdrive + collision + SENSIT -> RN + RN -> RN + RN -> Data Collector = 1+8+10+2+2+2 = 25s