There are so many implementation based schedulers are available.
- Round Robin:
this scheduler gives equal priority to every UE and schedules one after one.
- PF scheduler(propositional fair):
This scheduler will consider channel quality and fairness. Like I UE channel quality is poor if you schedules more data to those UE then its of no use because how ever it will be retx. So select a good channel condition UE and schedule more data, but to give fairness to other UE even if channel quality id poor schedule some fairness data to those UE. also based on through put some operator may schedule. They can ensure the same through put to all user. so based on running through put ENb will pick the UE
3 . QOS Scheduler :
This scheduler is purely based on the priority of the user and bearer(GBR,N-GBR,SRB). So always QOS scheduler will pick the UE which has either higher priority bearer or it will pick only the premium user. So in this scheduler there will be a starving of users. Mainly this scheduler will focus quality of service to those user who paid premium.
4 . Delay based Scheduler.
This kind of scheduler will give higher priority to delay sensitive bearers. This will work purely based on the bearer delay. If bearer delay is high then it will schedule only those bearers not UE basis.
Mainly all schedulers are implementation specific. based on operator requirement scheduler will be implemented.
Happy Learning :)