Major Airtel 4G issue: No internet while on voice call

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So i've been using Airtel 4G in Delhi/NCR for over a month and sometime back I realised that while I am on a call, I cannot use internet in parallel. It used to work fine while I was on 3G.

This is a major issue. If you ask me why I need to do that, here are some use cases:
1. While in a cab from Gurgaon to Delhi, I join hour long conference calls. I would like to check and reply to some emails in parallel. Or check what are the timings of a movie this evening - if the call is too boring ;)
2. A friend calls to ask my opinion on a phone he is about to buy in a shop and I say "Hold on, let me check" and I can't use internet in parallel so I can't see what he is asking my opinion for.

I'm sure you have your own use cases. I called up Airtel CC and they say this is how 4G is supposed to work, you will not get internet in parallel. And I was like, really? You are gonna take a major step back while rolling out 4G? He also said this is how 4G is supposed to work, and I was like NO. I have tried 4G in Sweden, UK and Thailand and internet works fine in the background while you are on call. He also said only 10-15% of the people use Internet while on call so it should not be an issue. And then instead of exploding, I smiled. You see I've matured in ways of reducing my stress while talking to Airtel CC.

So it seems some corners have been cut to roll this out. Instead of spending thousands of crores on the ad campaigns, maybe they could've reserved some money for this basic requirement of 4G. Can they really call this as 4G? Isn't there some minimum set of requirements... like getting an ISI mark?

Anyone out there also facing this? BTW I'm using an iPhone 6 and tried it on my wife's iPhone 6 too... same issue.

UPDATE on 21-Sep-2015 (Thread started on 14-Aug-2015)
Well in a nutshell, no real update and the issue continues to persist. Someone from Airtel persisted with me and got some checks done with the "backend team" but about 2 weeks are going to pass after the checks and the issue still exists!
 
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I think CDMA had this issue. You lost access to Internet while on a call. Not sure if 4G LTE has a similar issue. Never heard of it.
 
CDMA and GSM 2G had same issue because both call and data used same network. But with 3G this was solved and we could have call and data together.
I guess Airtel is using 4G for data and 2G for voice call, but I don't understand why both can't work in parallel. May be both call and data are using same frequency range or same network parameters.
 
evn i am ON AIRTEL 4G,
Issue i am facing is that when i am on 4g network(4g preferred) and if some one calls they gets busy tone.
 
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if they are using 2G/3G for calls, why can't they use that network for basic data connectivity? :D
 
Airtel is using CSFB (circuit switched fall back) for voice calls.

When the mobile recieves a call, it switches to 3G/2G. LTE being a pure packet switched network cannot deal with calls except when using VoLTE and therefore fallback to 2G/3G is needed in absence of VoLTE.

Nice document by Ericsson detailing CSFB: Source


If it falls back to 3G, data can be used. If it falls back to 2G, data cannot be used.
 


That's the limitation of bloody Apple phones. My Huawei got option of lte/wcdma only so you filter out 2g network completely which is in shit state right now.
 

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