Apple iPhone 4S: Thoroughly Reviewed
by Anand Lal Shimpi & Brian Klug on October 31, 2011 7:45 PM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone
- iPhone 4S
Improved Baseband - No Deathgrip
We’ve mentioned already that the 4S is more of an evolution of the CDMA iPhone 4 than the GSM/UMTS iPhone 4, and where that’s most obvious is again is its cellular architecture. When we reviewed the GSM/UMTS iPhone 4, we investigated and explained why its design made it especially prone to unintended attenuation when held a certain way. Apple remedied the situation somewhat by giving away free cases, but only in the case of the CDMA iPhone 4 was the fundamental design issue remedied by adding receive diversity with a second cellular antenna at the top.
The 4S builds on this architecture by incorporating the same diverse receive path with two U shaped antennas at top and bottom, and adding transmit diversity to the equation. I’m being a bit fast and loose with the term “diversity” here, since the 4S cannot transmit simultaneously on both antennas, but rather switches between the two antennas based on which has the least receive fading. Receive diversity is a bit more interesting to explain, since the 4S appears to be able to dynamically decide whether to select one of the two receive paths (in the case that one is much more faded than the other), or combine the two (using something like maximal-ratio combining) and get a better quality equivalent signal.
When I talked about the CDMA 4’s receive diversity scheme, I went into detail to prove that this feature was present. With the 4S, these diversity features are much easier to talk about because Apple has been directly forthcoming about the feature this time. In addition, the transmit switching part of the equation is discussed at length in Apple’s FCC disclosure (since the FCC is interested in scrutinizing transmitters), and even includes a nice diagram.
The device is capable of switching between the Primary/ANT1 and Secondary/ANT2 Antennas. The antenna switching is implemented with a physical, "break-before-make" switch such that only one antenna can be used for cellular transmission at a time.
To re-state the evolution that Apple has taken with this design, the GSM/UMTS 4 had one transmit and receive chain, the CDMA 4 added a second receive chain for diversity, and the 4S now has two receive chains and the ability to switch between two transmit chains. The result is that the phone no longer is prone to fading on either the forward or reverse link due to being held near the feed points for one chain.
To be totally thorough, you can immediately see that the 4S still incorporates the same overall design however, complete with a a U.FL connector at the bottom and a feed cable that runs up the side of the PCB to the top. From here it obviously terminates somewhere that makes contact with the top antenna.
Encircled in red: Top antenna feed cable (Original photo courtesy iFixit)
When we saw that the CDMA iPhone used Qualcomm’s MDM6600, we made an educated guess that the next device would likely be based on the same baseband. It turned out that this was pretty close to the case, as the iPhone 4S uses an unannounced Qualcomm MDM6610.
Encircled in blue: Qualcomm MDM6610 and PM8028, Red: Bottom antenna U.FL connector. Note to the right the two test pads for the two chains. (Original photo courtesy iFixit)
There are some immediate differences that stick out about MDM6610 versus MDM6600. First, 6610 doesn’t appear to include an internal transceiver, unlike MDM6600 which previously included a transceiver in its package. MDM6610’s package is correspondingly smaller, at 10x10 mm, compared to 6600’s 9.8x12.2 mm, but again you have to factor in the fact that the transceiver isn’t inside that package anymore. Based on those facts and the state of 28nm maturity, it’s almost certain that MDM6610 is still a 45nm part. The 4S uses Qualcomm’s RTR8605 IntelliCeiver transceiver for cellular RF management and also for GLONASS/GPS. We’ve seen RTR8600 before, and RTR8605 appears to just be an improvement upon that part with the same functionality. In fact, inside the MDM6610’s AMSS it’s just referred to as RTR8600.
Qualcomm isn’t ready to talk at all about MDM6610, but I’ve done a little digging and know more about this part. First off, it’s referred to as codename “Trek” inside the Qualcomm AMSS (Advanced Mobile Subscriber Software), whereas MDM6600 in the CDMA iPhone was referred to as “Phoenix.” When we first saw that the 4S was using a baseband that hasn’t been announced, we assumed it was an Apple specific one-off. However, after some digging I uncovered a reference to a GSM/UMTS only part as well: “MDM6210MDM6610”. For those that aren’t familiar, the 2 connotes GSM/UMTS compatibility, 6 adds 1x/EVDO. Apple appears to have secured MDM6610 exclusivity for the time being, but I expect we’ll see a more formal announcement of the MDM6x10 family down the road. This is pretty much par for the course for Apple when it comes to component sourcing.
| iPhone 4S - Network Support | |||||
| GSM/EDGE Support | 850 / 900 / 1800 / 1900 MHz | ||||
| UMTS/HSDPA/HSUPA Support | 850 / 900 / 1900 / 2100 MHz | ||||
| HSDPA/HSUPA Speeds | 14.4 Mbps / 5.76 Mbps | ||||
| CDMA2000 1x/EVDO Support | EVDO Rev.A (800 / 1900 MHz) | ||||
| Baseband Hardware | Qualcomm MDM6610 | ||||
MDM6610 also appears to inherit all the air interfaces that MDM6600 had, including WCDMA/HSPA+ with HSDPA 14.4, HSUPA 5.76, GSM, CDMA 1x/EVDO (up to Rev.B, though Apple notes only A is used at present), and finally GPS/GLONASS. Superficially, there don’t appear to be any major differences beyond using an external transceiver to accommodate diversity and transmit switching. In addition, the 4S contains all the same bands as the GSM/UMTS iPhone 4.
I was initially worried that Apple would go the same route that it did with both iPhone 4 launches and initially not include FieldTest. Thankfully, the 4S includes FieldTest right out of launch, which works for both CDMA and GSM/UMTS provisioned 4Ses.
iPhone 4S Field Test under CDMA Mode
There’s a corresponding difference in the interface for the two modes. On CDMA iPhone 4S mode, there are tabs for 1x and EVDO, and Rx signal strength fields for both receive paths, as well as the current transmit power. What’s interesting here is that when using the 4S in CDMA mode, you can see the receive strength change for each antenna when held.
iPhone 4S Field Test under UMTS/GSM Mode
On the GSM/UMTS provisioned iPhone 4S, you don’t get individual receive strength for each chain, instead just the effective RSCP from either the selected chain or combined. If you grip the phone while watching this, you can sometimes watch RSCP race to –130 dBm and then switch entirely to the other antenna and race back up to an acceptable number. As a reminder, to get into FieldTest dial *3001#12345#* - you can then keep numerics instead of bars in the top left by force quitting FieldTest after launching it (hold down power/lock until power off appears, then hold the home button).
So how does the 4S do in our actual attenuation testing? Very well actually. I watched the RSCP of one NodeB and held the 4S all the same ways we’ve done since the 4, recorded a bunch of data, and averaged it together. What we’re measuring here is reported in dBm, and less attenuation is better (0 dBm = 1 mW).
| Signal Attenuation Comparison in dB - Lower is Better | ||||||||
| Cupping Tightly | Holding Naturally | Holding in Case | On an Open Palm | |||||
| iPhone 4S | 10.8 | 8.8 | - | 4.3 | ||||
| CDMA iPhone 4 | 16.5 | 15.5 | 9.0 | 7.9 | ||||
| GSM/UMTS iPhone 4 | 24.6 | 19.8 | 7.2 | 9.2 | ||||
| Samsung Galaxy S 2 | 18.4 | 5.9 | - | 12.2 | ||||
| Droid 3 | 16.0 | 11.3 | - | 5.0 | ||||
| HTC Sensation | 15.0 | 10.0 | 8.0 | 0.0 | ||||
| Samsung Droid Charge | 10.0 | 10.0 | 5.0 | 0.0 | ||||
| HTC Thunderbolt - LTE | 5.3 | 2.5 | - | 4.4 | ||||
| HTC THunderbolt - EVDO | 6.5 | 0.8 | - | 7.2 | ||||
| LG Optimus 2X | 13.7 | 9.3 | - | 5.9 | ||||
| Nexus S | 13.3 | 6.1 | - | 4.3 | ||||
| Droid 2 | 11.5 | 5.1 | - | 4.5 | ||||
| BlackBerry Torch | 15.9 | 7.1 | - | 3.7 | ||||
| Dell Streak | 14.0 | 8.7 | - | 4.0 | ||||
| Droid X | 15.0 | 5.1 | - | 4.5 | ||||
| iPhone 3GS | 14.3 | 1.9 | 3.2 | 0.2 | ||||
| HTC Nexus One | 17.7 | 10.7 | 7.7 | 6.7 | ||||
When we reviewed the CDMA iPhone 4, I made mention of the fact that this was the first iPhone 4 I felt comfortable using without a case. This same confidence continues with the 4S, which is in practice completely usable without a case, unlike the GSM/UMTS iPhone 4. Since launch time, Anand and myself have been using our 4Ses without cases, and the difference is dramatic.
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ados_cz - Tuesday, November 1, 2011 - link
I have the 4S now and the problem is gone but once my girlfriend comes with her 4, I will make a video and post it to prove you wrong. People have no problems only in areas where signal is really strong. Why would I possibly want to lie?wonderfield - Tuesday, November 1, 2011 - link
What's of concern here is not whether the issue (signal loss) can be demonstrated but whether the phone is, in Brian's/Anand's words, "usable" with the defect or not. It's certainly possible for the GSM iPhone 4 to be rendered unusable in a low signal strength area with a natural, right-handed grip just as it can be rendered unusable with a death grip. That's not to say the phone will be unusable in most scenarios, however, because in most scenarios the phone should function properly. There are certainly edge cases, and the issue is more significant for those who're left-handed and for those who live/work in very poor coverage areas (where it can become an issue), but, again, that's not the typical use case. It's why I categorize Brian's claim that the GSM 4 is not usable without a case as being disingenuous.Realistically, you don't need a "really strong" signal to have not have any problems with the phone, you only need a signal great enough to overcome any attenuation introduced by making contact with the antenna. The extent of the attenuation, as demonstrated in another Anandtech article to which you might refer, is not as significant as portrayed by some media outlets.
ados_cz - Tuesday, November 1, 2011 - link
As far as the need for good signal went I needed to use the case all the time otherwise I would always have to hold the phone in unnatural way. iPhone 4/S is a really beautiful piece of hardware and It was really upseting that I had to use the case and spoil the desing. My close friend living just 15 miles next to me in Perth does not use the case and when he does not care to not to hold the phone in sensitive area, the call drops. It happend to me with him on the phone on few occasions. Few of my friends at uni need to use the case for iPhone 4 as well. The problem was not overstated. Either learn to hold the phone unnaturaly avoiding joining those two critical antenna strips or use a case. I opted for a case. My friend in the London got on well without case, but he learned to hold it by the to when calling. Anyway, I am glad that I have the 4S now and I think my girlfriend does not mind the case on her (former mine) iPhone 4. It so well made piece of hardware and so affordable here in Britain. You are being ripped off in US. Check the deals for iPhones on www.three.co.uk I got mine iPhone 4 for 69 pounds 5 months ago with two years contract for 35 pounds a month (2000 mins any network, 5000 mins mine network, unlimited 3G data with no fairu user policy). I paid 189 pounds for girlfriends (now mine) 4S for 32GB white version just few days ago and she got the same 35 pounds contract.Tetracycloide - Tuesday, November 1, 2011 - link
"I have hundreds of friends who have iPhone 4's who've never had any issue with signal loss at all."Really? Name them. Numbered from one to at least two hundred if you please.
Overstating the strength of your anecdotal evidence doesn't make you look right it makes you look biased.
For what it's worth, I think you're a huge tool for, well, being such a huge tool.
doobydoo - Wednesday, November 2, 2011 - link
Don't be ridiculous.To label someone a 'tool' for stating that their friends don't have issues with signal loss on a phone, is quite frankly ironic.
To suggest I would list my friends names in a bid to convince such a low level individual is even more ridiculous than the rest of your comment (which is a lot).
If you really need hard evidence, I'd point you in the direction of the millions of iPhone customers who gave the iPhone 4 the highest satisfaction ratings of any phone, full stop. Bit hard to imagine that happening if they cant make calls on it, don't you think?
To claim I'm overstating my quite logical claim doesn't make you look right, it makes you look biased.
Tetracycloide - Wednesday, November 2, 2011 - link
I labeled you a tool because your response to another commenter saying they experienced an issue you and 'your friends' never saw was 'your a liar' or more literally "For what it's worth, I don't believe you anyway." That's where you were a tool, that part right there.Your 'hundreds' comment was absurd and you know it. To obtusely pretend I'm actually asking you for a list of names and act like that's absurd (it was obviously rhetorical) is to miss the point which was: you do not actually have 200+ individual examples from 'friends' to draw from. That's absurd.
Your claim was hardly 'logical' it was an absurdly overblown statistic that, even if it was accurate, would still be anecdotal. As are you're 'millions of iPhone customers' by the way. The phone looses signal if held incorrectly. That is the objective reality, full stop.
doobydoo - Friday, December 2, 2011 - link
How ironic that your justification for calling me a tool, is that I essentially disbelieved someone else, after that's all your comments to me are based on.Not only that, but how ridiculous and illogical to say someone is a tool for not believing something. Grow up?
'Hundreds' is not absurd at all, perhaps it sounds absurd to a social recluse? But I can actually name at least 200 friends of mine who use iPhones. Sorry if having friends is a strange concept to you. How dare you claim that you 'do not believe' my 200+ friends claim - that makes you a tool (it's a definition handed down to me by someone special).
Even if my claim was anecdotal, so what? Your criticism of my claim wasn't that it was anecdotal, and I never masqueraded it as anything other than what it was?
The 'MILLIONS' of iPhone customers is not anecdotal at all, by the way - they HAVE factually given the iPhone 4 the best user ratings of any phone of all time. That's reality, fact, pure and simple. They wouldn't do this, if they couldn't make phone calls, don't you agree?
I own an iPhone 4, and it doesn't LOSE (wtf is 'looses') signal in any meaningful way (as in, it never affects call quality or causes calls to be dropped) if held in any way I want. Unbelievable that you make such claims then try to define them as 'objective' - exactly the criticism you levy at me.
gcor - Monday, October 31, 2011 - link
Reading the specs on a lead acid 12v battery I have, I discovered that the higher the load in amps, the lower the total amp hours the battery will output. For example, the spec's say that a particular model can deliver a max of 1 amp hour over 20 hours, but only .5 amp hour over 12 hours.I'm guessing this is also true for the batteries in smartphones and laptops. This assumption seems to be supported when looking at the 3D gaming battery life results in the review, where a 10% increase in power consumption on the 4S, resulted in a 25% drop in battery life.
I assume this has implications for the "race to sleep" concept, as an increase in amp draw by the device may reduce the battery efficiency enormously, as well as actually using more power.
Anyway, just a thought to add into the mix when estimating a % speed increase required for a pay off in additional sleep.
Pliablemoose - Monday, October 31, 2011 - link
Your recommendations mirror my own thoughts, picked up 3 iP4's in the last month, 2 ATT models to put on Straight Talk for $499/year each with unlimited talk text and data (yes, I know it's not really unlimited data) for my kids, and a Verizon iP4 for me. I actually replaced a ThunderBolt with an iP4, got tired of the poorly executed radio software and the constant reboots to keep it connected. The ThunderBolt is a heck of a 4G LTE modem, sort of a poor phone, and definitely a brick with the extended battery it needs get me through a day of web surfing and stock trading.Saving my upgrade next year for an iP5, and keeping my fingers crossed for at least a 4" screen.
ltcommanderdata - Monday, October 31, 2011 - link
"Furthermore Apple even seems to be ok with combining a process shrink with a new architecture as we saw with the iPhone 3GS. It's generally thought of as a risky practice to migrate to both a new process technology and a new architecture in the same generation, although if you can pull it off the benefits are wonderful."I don't believe Apple has actually pushed a new process and architecture simultaneously. Up to now, the iPod Touch was generally the test platform for new processes as a shrink on an existing architecture.
The full evolution is:
iPhone 2G/1st gen iPod Touch/iPhone 3G 412MHz ARM11 90nm
2nd gen iPod Touch 533MHz ARM 11 65nm
iPhone 3GS 600MHz Cortex A8 65nm
3rd gen iPod Touch 600MHz Cortex A8 45nm
iPad 1/iPhone 4/4th gen Touch 1GHz/800MHz Cortex A8 45nm
iPad 2/iPhone 4S 1Ghz/800MHz Cortex A9 45nm
It is curious that we haven't seen a shrink of an existing chip as a pilot for a next gen process, either Samsung 32nm or TSMC 28nm, although the iPod Touch not being updated this year didn't leave many options. It would no doubt be too risky to put a new process pilot chip on the iPhone 4S. I believe iFixit did find some different markings on the 2011 iPod Touch, but I haven't heard about any size difference so that makes a large shrink unlikely. Is there any chance the 2011 iPod Touch could be piloting the A4 on a TSMC 40nm process as a means of getting that relationship off the ground? Is there enough commonality in the tools for the 40nm and 28nm processes to make piloting on 40nm a worthwhile interim step?