Verizon and Sprint iPhone 4S and the limitations of CDMA

Verizon and Sprint iPhone 4S and the limitations of CDMA

iPhone 4S is the first iPhone to have both Verizon and Sprint CDMA versions available alongside the AT&T GSM version. CDMA is famous for its rock solid reliability and call quality and now that iPhone 4S is a world phone, it can even roam on international GSM network. However, CDMA brings with it some downsides as well, including lack of simultaneous voice and data over 3G, subtle quirks to SMS, and greatly reduced conference call options.

None of these are unique to iPhone 4S on Verizon or Sprint, but they're something to keep in mind if you're thinking of switching to one of those networks now that they have iPhone 4S.

So here's the deal.

There are some great advantages to CDMA. It tends to need less towers to cover greater areas so CDMA networks typically have better reception in more places. This also means they tend to sound better, more often for voice calls. If you use your iPhone as a phone -- who knew? -- and that's the most important thing to you, or if Verizon or Sprint provide the only reliable coverage in your area, than case closed.

If cost is a factor, well we've already put together that breakdown for you.

But if you want to know what you're getting into when it comes to the data and conference calling tradeoffs, there are several things to consider.

Note: We'll be using a lot of tech terms, so see our wireless networking guide for more on what all these acronyms mean.

Slower 3G data

iPhone 4S on AT&T and other GSM networks supports 14.4 Mbps HSPA+ download speeds. Depending on where you live, you may never get anywhere near that speed in the real world, but the potential is there.

By contrast, while CDMA-2000 give Verizon and Sprint great voice, their EV-DO rev A 3G data speeds are theoretically limited to about 3.1 Mbps.

No simultaneous voice and data

Verizon and Sprint's EV-DO Rev. A network does not support simultaneous voice and data the way HSPA and HSPA+ does for AT&T (and other GSM carriers).

That means if a call comes in while you're using 3G data -- surfing the web, Skyping, sharing your connection via personal hotspot -- you can either ignore the call and continue using 3G data, or answer the call and effectively put your 3G data connection on "pause". If you're on a call you won't receive email or push notifications and if you try to surf the web or download an app you'll be informed you're not connected to the 3G network. Once the call ends, 3G data reconnects and you can start using the internet again.

If you're on Wi-Fi as opposed to 3G data you can make calls and use data without a problem. It's only 3G data that cuts out during calls.

Verizon and Sprint have chosen not to roll out EV-DO Rev. B, which does support simultaneous data in favor of more quickly deploying a 4G LTE network (currently a hybrid CDMA-voice with LTE-data network, in the future a Voice over LTE network) and WiMax with LTE to follow, respectively. There are some phones that support Voice over Rev A (VoRA) aka SVDO which will allow for simultaneous voice and data on CDMA/EV-DO phones, but not the Verizon or Sprint iPhone. (See The Cell Phone Junky for more on the technology.)

SMS/Text splitting

SMS/Text messages are limited to 160 characters. On many phones, if a message exceeds 160 characters, the OS will be able to put it back together and still show it as a single message to both the sender and receiver.

On CDMA networks this doesnOn Verizon once an SMS hits 160 characters, any additional text is split off into a second message, after 320, a third message, etc. The same content is still delivered, it's just not presented as nicely. (In some cases the message parts might even appear out of order which is even more annoying.) Some users claim to seldom if ever experience this problem in the real world, others say it happens often enough to annoy them.

Limited conference calling

Verizon and Sprint's CDMA networks only supports "3 way calling" so you can only enter into a conference call with up to 2 other people (3 including yourself) at the same time. It doesn't matter if iPhone can handle more, CSMA networks and hence the Verizon and Sprint iPhone is limited to 3-way calling.

Likewise, handling conference calls is also more challenging on the CDMA iPhones since you can't take one party "private" or hang up on one caller while keeping the other active. You can only hang up on all of them at once.

Apple provides the following diagram in their knowledge base:

Verizon iPhone and the limitations of CDMA

The network

So yes, overall there are a lot of limitations to the way CDMA handles voice. However, if Verizon or Sprint has great coverage in your area, you're on Wi-Fi when you want to talk and surf, split SMS/Text messages rarely happen or don't bother you, and agile conference calling isn't a must-have business feature for your iPhone, you may not care.

Otherwise it's a compromise. Decide what's most important to you and which carrier best provides it. If anything is a deal-breaker, then that makes your choice much simpler.

For more information and help check out our iPhone 4S Forum.

Have something to say about this story? Leave a comment! Need help with something else? Ask in our forums!

Rene Ritchie

EiC of iMore, EP of Mobile Nations, Apple analyst, co-host of Debug, Iterate, Vector, Review, and MacBreak Weekly podcasts. Cook, grappler, photon wrangler. Follow him on Twitter and Google+.

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Reader comments

Verizon and Sprint iPhone 4S and the limitations of CDMA


Great article. A small comment regarding incoming calls: Once the call is incoming your internet connection is actually interrupted once you start receiving the call even before you choose to pick it up. The only thing you can do at that point is ignore the call as quickly as possible. I've had this happen to me numerous times when using my phone as a mobile hotspot (Very very annoying).

My concern is the speed if Sprint's 3G. I'm coming from Tmobile's HSPA+ Even though my current phone is capable of 14.4 mbps, I usually see 2-3 mbps.
As long as webpages load quickly and I can watch the occasional video without buffering interruption, the actual speed doesn't matter to me.

That was not the case at all with my old Sprint Pre. I wanted to like the network so bad but I couldnt take the atrociously slow 3G. I live in southern CT.

I'm definitely going to utilize Sprint's 30 day guarantee. And test out their network (I'm in Virginia). Hopefully I will not have to return my iphone after the 30 days!

The SMS/texting split is completely not true for GSM! I know many people with the AT&T iPhone and I get split messages with my Verizon iPhone if they send more than 160 characters! And if it is Verizon to Verizon texting if I use 1000 characters it will show up as one text. Get your facts straight. Besides that virtually everyone I know is a Verizon Wireless customer so I don't deal with these split messages.

I have a VZW Android phone and don't receive split messages from any carrier. I have noticed that I get a lot of repeat SMS from iPhone users on any network. 2 sometimes 3 times that ill repetitively receive the same message. They tell me its because of Android but it only happens on SMS from iPhone users.
Also usually when I do get a long txt message it defaults to an MMS instead of the 160 character limit it grooves on up to 1000.

Ha! So that's why text messages from my aunt's Verizon phone come as like six messages. My phone beeped six times in a row the other day and I thought it was spazzing out. Nope, just a long text that got split up.

This is a limitation of the actual phone(s) and not the network. The HTC Thunderbolt can Talk AND surf at the same time, while only being on 3G.

It actually is a limitation of the network, which is why the Thunderbolt is the only handset that supports it. It's also a contributing factor to the Thunderbolt's thickness, it has dual CDMA radios to make that a possibility, which is absurd to include to work around a networks inability.

Good article, but there's just one problem...
I can't keep a call for more than 5 minutes on AT&T. Just...forget it. Ain't happening.
So I give up simultaneous voice and data (only when not on wifi) to be able to keep a call going. Fair trade for me.

No shit. I've got to keep ATTWS since they're the only carrier that covers my entire family where they live. I wish ATTWS would figure out how to load-balance their WCDMA network where they have dual frequencies - if I'm in one of their new areas (850) or old coverage areas (1900), it's all good, but if I'm in Seattle or Portland with both WCDMA networks it's (s)hit-n-miss for calls (but data rates are blazing!)!

Yup its got an SVDA VoRA CDMA radio. Not two CDMA radios.. it's thickness is contributed to having that radio and the 4G LTE radio.

The thunderbolt isn't obnoxiously thick IMO and I do not own a thunderbolt, I did but it was a POS at launch so i got rid of it, but if Verizon or anyone else really cared, it is possible to Talk + Surf on the Verizon Network.

Rene, your section on SMS is incorrect. SMS to another phone on the same carrier will piece the multiple messages together. SMS to a different carrier will not, including one GSM carrier to another GSM carrier. There is no difference here between GSM and CDMA.
Furthermore, simultaneous data and voice is no longer a limitation of Verizon EVDO Rev. A. It's now squarely on phone makers to use capable chipsets, just as it is up to a phone maker to include a HSPA+ chipset if desired.

None of these affect me and being on the better network does. Would never consider leaving for AT&T. It's interesting to see what the real world HSPA+ speeds will be. Even if Rev. A gets "3.1 Mbps", I never see over 1.5. But I am not dismayed at all by this, I am just happy to have a data connection.

SMS is supposed to mean SHORT Message Service - but everyone seems to ignore that first "S"... :) If you have more than 160 characters - send a friggin' email :)

I already liked this comment, but I don't think that's sufficient. You are so right. I HATE when people routinely send novels over SMS.

You wanna know why ? Because people don't have time to log into their emails and type a damn email, also they want a faster reply, they don't wanna have to wait for an email. With text you get replies instantly.

I don't get it. If you have an iPhone you have your email WITH YOU, so saying you don't want to log onto it is a lame excuse.

Not really you wont have fast data connection everywhere so it would really be a pain in the ass to have to wait while logging into your email or actually waiting and not to mention most of these carriers dont allow unlimited data anymore so in retrospect text would be the easier way to go because it doesnt use data you'll always get instant replies.

So Verizon is Superman because of the call strength and reliability. AT&T is Batman because of it's the more experience, astute and sharper. Sprint is Wonder woman because, although a hero as well, not seen as such a threat and seldom considered part of the larger group.

To me, SPCS is more like Sybil, with multiple personalities - they've got EVDO, they've got WiMax, they're working on LTE, they've got 1XRTT, they've got IDEN, and they want T-Mo's GSM, WCDMA, and AWS.

Sprint is like Wonder Woman because it costs less, and in America a woman will often get paid less for doing the same job as a man.

I don't have AT&T 3G in my area or on the transits that I use (Often). Verizon 3G covers me where ever I go. I'm sure in a year or two Verizon's 4G LTE is going to cover more areas than AT&T's 3G (forget their 4G LTE, it'll take 20 years for them to make an LTE network that covers equal to Verizon's LTE & even after 20 years they'll be running their GSM-EDGE network !). Even when I try to use AT&T's GSM-EDGE in my basement, calls drop, left & right. Verizon is for those people who really want a reliable phone.

You guys are all missing the fact that any Wimax Sprint phone has had simultaneous voice and data since they came out. And, really how many of you ACTUALLY need simultaneous voice/data that don't also have access to a seperate device like an iPad, Android Tablet, or Laptop? So much focus on a feature less than 1% of users use less than 1% of the time.

I agree that simultaneous voice and data is overrated, but the Wimax argument is moot, since the iPhone won't support it. Personally, I don't care, since I live in Santa Monica, and can only get Wimax reception when I'm further inland. The lack of "4G" (Wimax) speeds will be a bigger problem for most people coming from another phone than voice/data multitasking.

This is a great article not just for iPhone users, or GSM/CDMA pros and cons. But a good description of how really networks work around. What i've seen in over a month of using Verizon's iPhone compare to my old BlackBerry I had with T-Mobile, is true that Verizon or any CDMA network you can't talk and surf the web at the same time, but in some devices. GSM like T-Mobile depends on the device. I couldn't do that on a BlackBerry but that's in the past. I don't mind the combo, i'm fine with Verizon and my iPhone...

I have to say that both networks have pros and cons and it comes down to personal use.
I use voice and data calls every single day and I really enjoy being able to access online documents to review them with clients while we're on phone calls.
Also being able to use my iPhone4 as a Mobile HotSpot while still being able to talk is a big plus for me.
There's nothing about Verizon I can knock and if you're on that network you can't miss what you've never had but as a person who rely's on the benefit of simultaneous voice & data AT&T happens to be my network of choice.
I personally am happy to have other networks join us with the iPhone experience since it will mean we'll truly be able to enjoy the iMessage & FaceTime experience with even more adapters joining the iPhone experience.
We as iPhone users already have to deal with the haters from the Android fan base so I say even though we're on different networks, we're actually on the same team so let's enjoy our iPhone experience no matter which network we choose.

I have a Verizon iphone 4, have never needed voice and data simultaneously, never dropped a call, never needed to talk to 4 people at the same time, and never had a text split up (regardless of length) to either me or the recipient. But maybe that's just me....

I look at it this way AT&T has had the iphone the longest as it started on AT&Ts network and they have had time to iron out a lot of the bugs and believe me there were quite a few. I had tons of dropped calls when I had my 3G and horrible data and when I first got my iphone 4 I had lots of problems but as the months went on it got better and better. I like the ability to check mail or respond to an SMS while I am on the phone as I use a bluetooth headset to talk and it makes it much easier to do this and you can check information or if you are talking to someone look something up and it comes in very handy.
Sprint has NOT had the data like the iphone generates so I know they will have issues and problems once the iphone goes live on their network. I had Sprint and I didn't like their service as it didn't sound very good everyone sounded like they were in a tunnel and I would get voice mails and sms messages sometimes a day later for some reason so I will stick with AT&T.
I think it really boils down to price and what features your carrier offers.
I know my parent's had someone get ahold of their number on VZN and they charged over 200 bucks of SMS charges for some service and NEVER let them know that it happened. It happened to me with AT&T and they sent me a text message about it!
So I like AT&T and will continue to support them as they have done very well for me!

service is different everywhere. whatever works for the person i guess. i live in olrando so service is great for all three carriers although my parents have att they suffer from alot of drop calls. at times they have data and voice outages. i have never suffered from any of that on sprint. i have been with sprint for 8 years and ive always had a reliable data speed. when i had my palm pre i would tether to my laptop and at times the speed would feel like highspeed internet which would really impress me. voice quality has always been great. the only problems i have is when i call people with att and it always sounds crappy. so for now ill stick to sprint until some other cheaper plan comes up else where.

Bingo. I've always been on Sprint and won't feel like I'm missing out if I can't surf the web while talking. OR I could just connect to WiFi to use the data while on a call.... so many places offer WiFi nowadays anyway.

It really depends on where you live that dictates your opinion about this issue.
If I am standing at a coffee shop in the heart of downtown Chicago, my signal can fluctuate from 1 bar to 4 in a span of 15 mins. In addition, if I am on a call in the same coffee shop, I might drop a call or I might not. It depends on where you are and what is going on around you wirelessly that will affect your signal.

I think it's rude to talk while browsing; then you have to make them repeat themselves because you didn't hear them. I'm a terrible multitasker, so if I'm on the phone, I'm not on the web.

I know the limitation of CDMA, but a least a phone call will interrupt the data. I had a phone on att(We did not have 3g here), so when I was using data I could not get a phone call.

This is a useless comparison because it looks only at protocol and not implementation. Fact is, AT&T is oversubscribing the crap out of their networks in major metropolitan areas - so any theoretical advantages to GSM are nil for the majority of users.

Not exactly true anymore. ATT is backhualing many towers with fiber and and installing more radios at cell sites which significantly increases capacity in preporation for their LTE rollouts. My area was 3G til around mid summer of 2011 when they rolled out HSPA+. My old iphone ran at around 1.3Mb/s down and 200k up. Now my Inspire runs an average around 5-6Mb/s down and 1-2Mb/s up. Big difference in less than 1 year.

Great article. I recently switched from the At&T iphone 4 to the Verizon iPhone 4s. I'm now able to stay on the phone during a long commute without getting dropped. The inability to efficiently conference call on Verizon may be a deal breaker for business users. I certainly didn't know about it until I encountered this Verizon problem. If AT&T had a reliable voice network it would be the "no-brainier" choice. I have AT&T three years to improve voice - in Manhattan and suburbs - and they failed. So I'm now happily stuck with an inferior technology.

Great article. I recently switched from the At&T iphone 4 to the Verizon iPhone 4s. I'm now able to stay on the phone during a long commute without getting dropped. The inability to efficiently conference call on Verizon may be a deal breaker for business users. I certainly didn't know about it until I encountered this Verizon problem. If AT&T had a reliable voice network it would be the "no-brainier" choice. I have AT&T three years to improve voice - in Manhattan and suburbs - and they failed. So I'm now happily stuck with an inferior technology.

I brought my Iphone 4s to a Verizon store for the conference call issue and they spent an hour updating, then ended up sending me a replacement iPhone which of course has the same limitations. I should've found this article before.

it should come with the adupte since siri is part of the iOS 5.0 software adupte. Along with iMessage and all of that good stuff. Im getting the 4s but if i was use i wouldn't upgrade if u already have the 4. hope this answers ur question. thumbs up please trying to get to level 2

If you want to install wzpvix, you should just go directly to the Verizon website. Go straight to The VZWPIX Site . I’ll write more tomorrow I am going to check it out and see if I can get it working.

I have an ATT HTC Inspire 4G phone and have no complaints. I can talk and surf at the same time which is a nice option. My entire area(Southeast Michigan) is covered by 3G/HSPA+ so no speed issues. Last spring I switched to Verizon for 3 months and got the HTC Thunderbolt which is an awesome phone. The problem is I am on the fringe of Verizon LTE here and the Verizon 3G speeds were very slow often running below 40 Kb/s so I switched back to ATT. I disagree with one point in this article. The Thunderbolt sounded very tinny and words were often pixely and cut off and when the person I was talking to spoke at the same time, you could only here half of the words. Now, my ATT Inspire sounds crystal clear and when two people talk at the same time you can here the entire words and no pixelating. Lastly, when I run a speedtest and get 5Mb/s down and 1.5 up I know which network is superior(excluding LTE). The BIG advantage Verizon has is their entire network is minimum 3G and ATT's BIG disadvantage is their 3G/HSPA+ network is limited to a much smaller geographical area :(

been trying to do the same and yes i have sprint and that just sux that i have to hang up with both to drop only one on a conference call...does the iphone 5 do this?