Editorial: Why Simultaneous Data and Voice on Verizon’s iPhone Doesn’t Matter

In the wake of the announcement of the Apple iPhone 4 on Verizon, one question I’ve seen come up is if the Verizon version will be able to use voice and data simultaneously, as on AT&T’s version.  Typically, some of the answers to the question range from the half-right to the hilariously incorrect with a lot of confusion in between. I think a better question would be: Does it even matter at this point?

In order to understand why AT&T touts simultaneous voice and data as an advantage, you have to look at their network. I’ll get to the iPhone in a bit.

UMTS (and by extension HSPA/HSPA+) uses a 5MHz channel to transmit voice and data over the air, with the capability to further “split” the channel into two 2.5MHz sub-channels in case one person is sending both voice and data at the same time. In contrast, Verizon’s CDMA network uses a much smaller 1.25MHz channel to send voice and data, with no way to split the channel further, forcing either data access and no voice calls or voice calls and no data access.

With that out of the way, you might be wondering how Verizon is able to offer Skype Mobile on its phones since it requires both a voice and data plan. Simple: a little network and software trick called IMS or Internet Multimedia Subsystem.  IMS is built into a CDMA EVDO Rev. A network and overlay by converting the initial outgoing call into a data session, “moving it” onto the data network via application and network flags. The carrier has to turn on the IMS on the backend in order for simultaneous voice/data to work and the developer has to include the support for IMS into the program, otherwise it’s not going to work.

Now, back to the iPhone. Reports started coming out last summer that Verizon was working on Voice Over Revision A for the iPhone. This is IMS, it is not new nor is it exclusive to the iPhone as many erroneously reported.

Now that its been confirmed that that the iPhone 4 will not support simultaneous data/voice, is browsing and talking on the phone really that important to current and potential iPhone users? Only if you care about bullet points. The reality is that few, if any people will actually use such a feature frequently enough to take it into account as a purchasing decision and only see it as a novelty.

Sure, it would be nice to talk on a headset and browse on Mobile Safari on Verizon’s network at the same time, but that would lead to intense battery drain and temperature issues as the chipset would be handling a phone call over VOIP and a data session over EVDO, something that’s conveniently overlooked on AT&T’s claims. In fact, the only people that see it as an advantage are those that care more about spec sheets than real-world utility. Just try using AT&T’s impacted data network… with half the bandwidth you normally get.

Should you worry about the possible availability or lack of simultaneous voice/data on the Verizon iPhone? In my opinion, not one bit.

Humberto Saabedra is the Editor-in-Chief of AnimeNews.bizPhoneNews.com and an occasional columnist for Ani.me. He can also be found musing on things at @AnimeNewsdotbiz

22 responses to “Editorial: Why Simultaneous Data and Voice on Verizon’s iPhone Doesn’t Matter”

  1. Nanfy

    Actually I use a lot of simultaneous voice and data at the same time. As an Network architect I’m often using logmein and other remote apps on 3.25G or whatever its called now, while talking on the phone to the local tech.

  2. Christopher Price

    I’m sure there are specific usage scenarios, but even in those cases, I tend to agree that it is more of a buzz feature… Wi-Fi is going to be necessary for business-critical situations, especially on an impacted network like AT&T.

    The only major usage scenario that I prefer simultaneous data and voice is while stuck on hold. And, I’d prefer a Clear Spot in those cases since I then have 4G data over Wi-Fi anyways.

  3. chad

    nanfy,you apple fanboy’s are all alike,you will defend at@t and apple to the death,you know the cartoon on youtube if apple put out a brick and called it a iphone people like you would still buy it and scream to the heaven’s about how great it is.verizon and att both have the iphone it’s a win win for the consumer’s.

  4. Nanfy


    I don’t have an iphone nor would I ever pay for ATT or Even verizon service. I have a company provided tmobile G2 and my personal phone is a sprint samsung epic 4g with 9 lines under my account. So please don’t generalize next time. You seem to have forgotten that tmobile is also gsm and can do voice and data at the same time.

  5. geo

    When I had the original 2G iPhone on ATT it was a bummer because I couldn’t surf the web if I was waiting on a client call, otherwise the call went to voicemail. Don’t know if that’s an issue for Verizon.

  6. chad

    then why are commeting on something that has nothing to do with the iphone or your service,and i do know that at@t and t-moble are gsm and sprint and verizon are cdma,still data and talk at the sametime is not a big issue with the average consumer plain and simple

  7. Nanfy


    The editorial states that Simultaneous Data and Voice isn’t a major feature. Well for certain people it is and I am one of them. I commented that this feature is important to me. It has nothing do with the iphone in particular but a limitation of CDMA networks. For someone who is mobile and works a lot from there phone its important.

    You went ahead labeled me as an att and apple fanboy when I didn’t even mention anything about either att, the iphone, or apple. I simple said that Simultaneous Data and Voice which is available on gsm networks is important to me and I gave my specific usage scenario.

    You can call me a GSM fanboy if you want. I’ll take my hspda+ over evdo rev A anyday along with the blessing of a sim card.

  8. Christopher Price

    Geo, your calls shouldn’t have been bounced to voicemail. EDGE and GPRS data both have call sensing, where you have the opportunity to pause the data session and take the call.

    The same is true with CDMA, though a few early EVDO devices had bugs with this feature.

    As to SIM cards, well, my take on them is that they are only beneficial because of the poor backend solutions that CDMA carriers had for years. Verizon now allows CDMA device swapping in-the-field, because of the fact that they don’t use SIMs on CDMA.

    Unfortunately, the stigma of earlier versions of *228 have convinced Verizon to go to SIM cards for LTE, which means in-the-field swapping will die before people could even really discover its utility. It’ll now be left to MEID vendors like Clear to convince people that SIMs are unnecessary and do more stifling than innovation (especially on the plan/pricing side of things).

  9. Nanfy

    It is widely predicted that Clear is in a lot of financial trouble. They may go under within the next 6 months. Sprint will be left to pick up the full bill and continue operating the wimax network themselves with the other minority stakeholders.

    CDMA networks will be relegated to the bargain basement carriers like metro, cricket, and soon to be sprint.

    Once Verizon goes Voice over LTE, most of America will be Sim based except for sprint with the rest of the discount bunch.

  10. zephxiii

    Wow this article is a big FAIL!!

    Sorry, i’ve never experienced a suddenly huge drain in battery life or increase in phone temperature when using this feature. In addition you really think a phone call on UMTS uses 2.5mhz??? CITE YOUR REFERENCES!! Also, don’t you know using half of the HS-DSCH in the 5mhz channel will get you around 5mbps????

    FAIL FAIL FAIL!!!!!!!!!!!!

    You sound like a VZW defender!!! lol

    IT’s better to have features than to not have them!!

  11. Chris

    I may not be the average user, but I tether daily for work. I can’t always be in range of wi-fi. When I was on VZW, it was frustrating when phone calls came in. Always had the choice to either sacrifice remote desktop sessions or take the call. And if I wanted to take the call, closing remote desktop sessions quickly so that the session wouldn’t close “unexpectedly” took time. No guarantee of being able to pick up the call in time. And never mind working on an issue with a client where you’re both trying to look at the same server and discuss over the phone. Some one sends you an email while you’re on a conference call – drop off, get email, & call back.

    My overall experience between AT&T & VZW – I have had the dropped calls on both network, neither one worse than the other for me. The lack of simultaneous voice/data was the deal breaker for me when I left VZW after 10+ years. I think my biggest issue with VZW – I lived with “crippled” phones that were 2 years behind other carriers so VZW could test the overall impact to their network. You couldn’t get a Motorola Razr on VZW for 4 years after it came out. The CDMA version was there, it just took years to approve it. And when it was approved, basic functionality was dropped – file transfrer via bluetooth, for instance. Tethering – dropped. Every phone from VZW was like that – some random feature was disabled on a phone other carriers had 2 years prior VZW’s release.

    As for the speeds – each carrier at any given time is going to have the “fastest” network. At this point, unless you’re streaming HD video, it seems the bandwidth should be ok for most usage. It’s a p*ssing match no carrier actually wins, or at least for long. On AT&T, I’m currently getting 3.7 Mbps downstream. EV-DO is currently less, but adequate, unless you receive a phone call.

    Once VZW’s network is upgraded, and the advertised speeds & simultaneous voice/data are reality, I evaluate if I make the switch back. At that point, it’s a question of 2 things. First, did Apple cave on any VZW concerns of adverse network impact & disable any iPhone (or whatever Jesus phone is available at the time I switch) features, and which carrier is offering the best deals.

    As a disclaimer – yes I have an iPhone, I have upgraded each year from a 3g to a 3gs to a 4. About the only platform I haven’t owned or used is Android & Windows 7. Out of all the phones I’ve had, the iPhone has been the most reliable. Don’t like the control Jobs puts on your phone? Jailbreak. Until something more reliable & flexible comes along, I’ll stick with my fanboy iPhone on a crippled (but more flexible) network.

  12. Phoneman

    I use voice and data at the same time every day on Sprint’s 4G network.

    This article leaves out several instances when people might find it useful, such as…

    Talking to someone one the phone who is giving me an address. I am putting the address in the navigation app as they give it to me.

    Talking to someone on the phone and one of us sends the other a picture or an email. Don;t want to get off the phone, confirm it was received, and then call back to discuss it.

    Someene already mentioned the remote sessions. And that would have to be a huge issue for any IT pro. You are remoted into a computer, while talking to the end user or field tech.

    Really, to me, not having simultaneous voice and data it just as bad, or even worse, as not having call waiting. If you get another call while you’re on a call, you want to get that call. You don’t want to miss an important call just because you were on another call.

    Well if you get an important email while you’re on a call, you won’t want to miss that either.

    I see this as one of those things that people will pretend it isn’t important, and then when they get the feature later this year and realize what they’ve been missing, they will be very happy to have it.

  13. Dihce

    It’s obvious that the writer of the blog has never used the simultaneous voice and data. But I have often been on the phone and an off the wall question or reference comes up and I use my phone to look it up. 9 times out of 10 I don’t notice a drop in speed, call quality, or the call at all. There has been times when I noticed a slight drop in speed, but not enough to make a difference.

    The iPhone 4 has a great battery, so the extra battery drain is minimal. I’ve never had “Excessive heat” generated from using both services.

    long reply – short; This guy doesn’t realize how differently people that currently have the iPhone use their phones. It’s one of the best multi-tasking phones on the market hands down, and the people that use them Multi-task on it more than any other phone…

  14. JDub

    It cracks me up how defensive people are about their mobile carrier… relax, people. Take a deep breath and turn off Fox News for a minute.

    Simultaneous voice and data is important to me. I use 2500+ mobile minutes per month and often need to look up an address or other item while on a call in my car.

  15. Noelle

    Well this year or possibly next year, it all won’t matter. CDMA is getting an upgrade to SVDO/1X Advanced to allow simultaneous data and voice. I know VZW and Sprint both have plans for it later. Upgrading CDMA2000 will remain in place for another decade until 4G matures. SVDO is comparable to HSPA+, however it’s up to the carriers to adopt the new standards. SVDO will eventually speed 32MB down.


  16. DavidP

    After having simultaneous voice and data theres no going back, this is a major feature like call waiting you might not use it that much but when you need it…you need it! Just today I was on the phone talking with a friend about her birthday party and her pics on facebook, I was able to keep the calling going and review her facebook page at the same time. Another time I was on the phone with a client to confirm an important, I’m sorry but you guys are sleeping on the value of that simultaneous voice and data brings. My Sprint EVO with 4G data and 3G voice working at the same time is just too nice. That is all.

  17. Christopher Price

    4G and 3G simultaneously is a different situation. On the Verizon iPhone, there is no LTE or 4G access. You would be in a situation comparable to AT&T, where voice and data would have to share the same spectrum. As we’ve seen on AT&T’s impacted network, that doesn’t go so well.

    While we don’t know yet how Verizon will handle iPhone, we could see similar impacting and performance issues, which would make simultaneous voice and data even worse.

    With WiMAX, you’re really using two networks; CDMA for the voice, and WiMAX for the data session. That works much better, and gives you performance worthy enough to actually take advantage of the feature. T-Mobile’s network has lesser dividends in this arena, due to having HSPA+ as well as an under-utilized network.

    A Verizon iPhone that included LTE, for example, would continue to use CDMA for the voice network. Verizon has already confirmed this is how their smartphones would operate. At that point, I see simultaneous voice and data becoming much more viable of an option.

    Until then, I am content with my Clear Spot and having 4G as an external option that actually delivers working performance, regardless of if I’m on a call or not.

  18. Brian

    My question is this… I don’t surf while on the phone. Phone calls are phone calls.. my concern is IM services and other background programs. If you have AIM or Yahoo or say Line 2, a 2nd line app for the iphone running and you get a call on Verizon… does it log you out of all of these and back when the call is over? How does that work?

  19. Phoneman

    @ Christopher Price
    So you’d rather pay for 2 data plans instead of just having the feature built in?

    I’d rather just have simultaneous voice and data on the phone. If the performance sucked, then I’d still have the option to get a Clear Spot if needed.

    I used to use simultaneous voice and data on AT&T often. The performance wasn’t the same as my super phone on Sprint’s 4G, but it got me by.

  20. Christopher Price


    Clear 4G service is as low as $25/month (on iSpot). That’s for unlimited 4G data, over a reliable network. Compared to AT&T at $25 for 2 GB (of impacted 3G data).

    Not to mention that I am not using the same bandwidth from the same radio. And, my 4G service is no-contract, so I don’t have to pay when I don’t need it.

    I firmly believe wireless gateways are the future, and eventually voice will be all-VoIP, negating the need for this costly and inefficient technology.

  21. Miles Erickson

    I too use voice and data simultaneously (normally Bluetooth tethering of my iPhone 4’s data connection to my MacBook Pro) on a daily basis while working in the field. The Verizon iPhone would simply not work for me, unless I had a separate Verizon internet device like a MiFi… but that would come at a much higher monthly cost than the AT&T iPhone 4 plus tethering.

  22. Natesh Sood

    Great article! Very good read for anyone looking to understand the true technology behind simultaneous data and voice and whether it is a factor or not.