I would like to know the algorithm of switching between 4g/3g/2g. When will the phone switch from 4G to 3G or from 3G to 2G, when we select for corresponding option in the mobile phone. Is it based on dBm/RSCP etc? I am looking for some technical document. TY
Hello! The technical term for this procedure is called the ``handover.'' Some references call it ``handoff.'' The technical documents that describe the handover of the UE from 4G LTE to other radio access technologies can be found in 3gpp TS36.331 under Inter-RAT mobility. As for the handover from 3G to 2G or to 4G, you can find the same information in 3gpp TS25.331 also by searching for inter-RAT.
The caveat is that reading the 3gpp standards can be tricky to researchers who are not familiar with the approach. Feel free to ask further if you need further details.
Now, answering the other question you posted. Generally inter-RAT handovers are based on signal strength measurements (aka LTE RSRP or WCDMA RSCP quantities which are reported in a translated dBm scale). A measurement gap is required in order for the UE to measure the received signal strength of the target technology as well.
Good luck!
Technically, there is no "switching". The 3G standard is backward compatible to 2G and as well 4G is backward compatible to 3G. If you have a 4G phone in a 3G network, it will work fine but you will not have the 4G feature.
By mobility IRAT Inter Radio Acces Technologies based on Radio Quality and coverage Thd we can switch from 4G/3G/2G Ben Levitan
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