WiFi Calling bit rate vs Cellular


    I have a kind of complicated question... I'll try to break it down like a fraction for y'all.


    1. When making calls, does tmobile give higher call quality to calls via cellular or calls over wifi.

    2. What is the bit rate for each one of those options.

    3. T-Mobile pushes for WiFi calling for a lot of reasons, but the quality of calls on T-Mobile vs my Ooma are very different. I LOVE my Ooma phone and my all are FLAWLESS . Why would the call quality be different if they are on the same WiFi network. ( 40 mbps down and 5mbps up... very stable)

      All replies

      • tmo_mike_c

        Re: WiFi Calling bit rate vs Cellular

        Hey dellman87 thanks for breakin' this fraction down like a math teacher!


        1. This question is kind of tough to answer. Call quality depends a number of factors like the type of connection that you have to the network or the Wi-Fi connection you're on. For the Wi-Fi calling, T-Mobile can only guide you through steps on the device to make sure it's properly set up. None of the those steps would dictate what kind of call quality you would get on Wi-Fi. The other factor that would contribute to the call quality would depend on the ISP's ability to handle VoIP, their connection speeds, the router and modem, as well as how the hardware is set up. As for the T-Mobile network, the connection you're getting would contribute to the call quality. For example, those connected to the 2G service vs the 4G service may have a different call quality experience. (We also have The specified item was not found. which will start a whole different conversation. )
        2. Each connection has it's own range for bit rates. Our T-Mobile network bands & technologies page as some information about Mbps and Kbps for the different connections. For example, 4G (HSPA+) you'll see speeds that range from 21 to 42 Mbps.
        3. This one, I'm a little confused on. We give our customer's the option of using Wi-Fi calling especially in instances where it makes the most sense to use it.

        Why would the call quality be different if they are on the same WiFi network. ( 40 mbps down and 5mbps up... very stable)

        This is where you've kind of stumped me. I'm not exactly sure what you meant here. T-Mobile's network and someone's personal Wi-Fi would be to separate connections. As I mentioned before, call quality would part equipment and part connection. Both of which would have it's on contribution to the call quality.

          • dellman87

            Re: WiFi Calling bit rate vs Cellular

            Thank you for the response Mike. I'll explain some of my questions a little better.


            1. Given I have a 5 bar LTE connection, OR a Wifi connection of 40 mbps down and 5mbps up - Calling to a landline number (so non HD caling) Which would deliver the BEST call quality? Do you have a bit rate guide? Wifi Calling provides ___ rate and LTE gives you ___ (w/o HD calling enabled b/c it has to be another T-Mobile device w/ feature enabled)


            2. My Ooma and my phone would be on the same wifi network. Why is my ooma giving me better voice quality vs my Note 5 on the same wifi network?

              • tmo_mike_c

                Re: WiFi Calling bit rate vs Cellular

                Okay, so since call quality can sometimes be a matter of perception, I'd like to speak on the technical factors that will put you in the most ideal position to experience the best call quality. (I'll just kick my feet up real quick and get comfy cause this conversation might get deep )


                So, in the example that you used for the Wi-Fi connection, you've put yourself in a great position to have really great call quality from a technical standpoint. In the same breath, I'd say if you had 5 bars of LTE, you've still put yourself in a great place for great call quality. The best call quality in both situations but you'd still have to hear a call on both phones and compare them for yourself. Again, this will be, in part, a matter of perception.


                As for a bit rate breakdown, the only reference we have is the T-Mobile network coverage link I posted earlier but this is only a measurement of upload/download speeds in relationship to the specific connection you have. Sorry this won't have a bit rate of Wi-Fi Calling vs cellular network calling.


                To your Ooma vs Note 5 call quality question, this would be in relationship to what I mentioned earlier. Since the phones are put in the same conditions (same Wi-Fi connection) it's safe to say the quality isn't being effected by something like your internet connection or modem/router hardware. So, now we'd need to see if we're dealing with 1 of 2 scenarios.


                1. The Note 5 had great quality at one point and now it's somehow degraded overtime.


                2. Are you comparing two different phones and you're simply noticing a significant difference in call quality and want to know why that is?


                If it's a degradation in call quality, we'd be looking at the software, possibly hardware of the Note 5. Resetting the device would be the software fix. If you're simply comparing the 2 devices, that's where it gets a little tricky. I can only debate call quality from a technical standpoint. Meaning for example, phone A that has 1 bar of 2G signal may not experience the same call quality as phone B that has 5 bars of strong 4G LTE signal on the same network.

                  • dellman87

                    Re: WiFi Calling bit rate vs Cellular

                    I appreciate you taking the time to reply to my complicated questions. I believe the answer I am looking for is unknown, looks like T-Mobile only gives you guys the face value answers you need to get by, I'm looking for something more on the technical side, which seems no one knows the answer to (I've reached out to multiple people)


                    Thank you for the reply!

                      • tmo_mike_c

                        Re: WiFi Calling bit rate vs Cellular

                        No problem. Sorry we don't have the specifics you're looking for. That's a unique question that has a lot of moving parts involved in the answer. As I mentioned before, what we have are the kbps and mbps you can expect to get on our network. We do always appreciate a challenging question though, so thanks for posting!