SNMP - number of connected Clients


I run the lastest snapshot from master branch on my Accesspoints (Zyxel NWA1123-ac) and I they seem to work good. But I miss the ability to monitor the number of connected clients via SNMP. Any Ideas how to do this? I installed snmpd and collectd but librenms finds only few data - much fewer than with the factory software. Any hints to further information/documentation are welcome.

(@Mods: I would like to have write access to the wiki - I would like to edit the Wiki page of the NWA1123. I want to add information on how to connect via serial and add pictures of that process.)