Hi,
Please help with my question. I have problem some times my voice is slightly Breaking in other end. This is happening with some of my calls.
I also have several other turned on cell phones with SIM cards in my room.
Do they affect the quality of the call which I make on my main phone?
I’m pretty sure not, but I like to ask 
I also have some suspicion that it is the fault of my main phone.
For your understanding every phone is receiving most of the radio signals around him most of the time and continuesly doing measurements of those signals strenghts.Therefore your question regarding the interference of the receiver is answered by it I think and the answer is No.To visualize it download the app named ForceLTE which is a free android app through that you can see the radio signals currently your device is listening into.Thank you.
If you’re facing LTEsignal interference and voice call problems, first check if it happens everywhere or only at a specific location home/office. Many times it’s due to weak signal coverage, high network congestion, or interference from nearby towers operating on the same or adjacent frequency bands. Try basic steps like switching between LTE/3G, turning airplane mode ON/OFF, or restarting the phone. Also check if VoLTE is enabled properly—misconfigured VoLTE often causes call drops or poor call quality. If the issue continues on multiple devices, it’s best to raise a complaint with the operator so they can check network optimization or interference issues from their side.
I know I took a long time to reply, but this may still be useful to someone.
The network has undergone many changes, but one issue remained. Whenever the phone negotiated EVS with one particular mobile network in my country, the codec would always fall back from EVS to EFR after some time. This consistently happened whenever the remote party on that network was using an iPhone, Sony, Motorola, or Pixel device.
The network that was causing the issue on my side enforces max-red=220 during calls, meaning SDP/RTP parameters related to voice frame redundancy. My impression is that my old Nokia 8 simply did not understand or properly handle this parameter.
I should add that the fallback to EFR occurred only with one of the call participants, which is entirely possible with EVS.
Actually If A party offers Primary codec as EVS but EFR supported in SDP offer and lets say B party has only one codec which is EFR,then codec used end to end is completely depend on how we configure the network. By the way,EFR is never used in IMS and the mentioned paramaeter some what related to why that is not used but lets say B party only support AMR and Aparty selct first codec as EVS but AMR is also supported,Then you can configure the network in two ways.The most common method is enabling TrFO(Transcorder free Operation).Transcoding which is converting one RTP stream with one codec to another is high Processor incentive function therefore by norm almost all networks are trying to minimise this in there MGWs.What that means is when B party offer answer with AMR reached A party GW Aparty GW is forcing A party UE to use AMR so without transcoding end to end call will get established with AMR even though how bad UEA needs EVS.Thats the normal implimentation of almost all networks in the entire world.But If you dont care about MGW capacity you can switch TrFO off which means A party connected SBG will convert the AMR stream to EVS vice versa.Which means Aparty will here evrything via EVS codec while B party will get the low quality AMR.
That is exactly how the symptom manifests: one side continues to hear clean, crystal-clear EVS, while the other side does not. This occurs after a few minutes of the call, sometimes even sooner. The signaling on both terminals still continuously indicates EVS-SWB. Nevertheless, thank you for the explanation.
Does the fact that the terminals continue to indicate EVS-SWB despite audibly degraded AMR-like quality suggest that transcoding has occurred?
Codec Negotiation usually gets completed before B party answers the call.Which means before the call starts.But If you are seeing it in a middle of the call which means one party has done a handover to either 3G or 2G which dont handle EVS.I am quite sure the network you are in is TrFO enabled which means end to end codec is negotiated before call starts.If it is happening in the middle of the call suggesting that your network are full of handovers.Lets say initially call is setup end to end EVS,even that is the case if one party dropped it to AMR if TRFO is enabled then both party will get dropped to AMR via special signalling arrangment unless one party is not supporting the lower codec.When it comes to codec there are two types of codecs.which is Narrowband codecs,Eg:G.711,G.729,AMR etc. others are wide band Codecs,Eg: EVS, AMR-WB(HD voice ).The quality difference of those two is extremely high so anyone can notice it.