Extended DRX (e-DRX) is a concept which is very helpful for IoT devices which has requirement of long run battery. DRX is the concept which is being used in LTE to increase battery life. But for IoT devices, using DRX was not able to support long run battery. That's why a new concept came "extended DRX" which uses HyperSFN (Hyper System Frame Number) concept to support eDRX.
Earlier, System Frame Number and Sub Frame both were being used for most of synchronization operations. Since there was a need of higher value of time synchronization HyperSFN concept came into picture. The value range of System Frame number is 0 to 1023. Once SFN reaches to 1023 and again it starts with 0, value of HyperSFN is incremented by 1. By using HyperSFN, synchronization time can be increased more than 2 hours.
UE/IoT device whichever connects to network it sends eDRX information to MME in attach request message if devices support.
MME includes the received eDRX information into S1-AP paging message sends to eNodeB. If eNodeB also support this feature then the value of eDRX information is taken into account to calculate paging occasion.
