| Applicable versions | NetSim Academic | NetSim Standard | Netsim Pro |
| Applicable Releases | v11 | v12 | v13 |
Given below are some 802.15.4 (ZigBee) protocol functionalities relevant to this analysis.
- At a transmitter (source node or intermediate node), when a packet transmission leads to an error or collision retransmission is attempted (if Ack request is enabled). The number of packet retransmissions is decided by the Retry limit variable set in the GUI.
- If the Retry limit is hit then the packet is dropped by the source / intermediate transmitter.
- Sensor nodes in NetSim are assumed to have an infinite buffer and hence packets cannot be dropped due to buffer overflow at intermediate nodes.
The Max Frame Retry limit is set to 3 by default in the Datalink layer section of the sensor's ZigBee interface properties as shown below:
The NetSim Packet Trace file records details of each packet transmitted by each node including the packet status (successful/collided/dropped/errored). A pivot table can be used to analyze this quickly.
When simulating a congested network users would see packet losses due to collisions and errors. In addition, packet losses can occur due to drops, when the retry limit is hit after attempting multiple re-transmissions.
All these effects can lead to a low packet delivery ratio (PDR).
Useful links
1. NetSim IoT overview: https://www.tetcos.com/iot-wsn.html