The Many Faces of 3G 122
An anonymous reader writes "Did you ever notice how each new generation of cell-phone tech gets branded '3G,' and the previous thing is retroactively downgraded to some lesser number of Gs? An MIT engineer explains why in this brilliant essay about '3G' over the last 10 years, showing how the cell carriers have kept offering it and swiping it away to sell more stuff. He cites numerous Cingular/AT&T and Sprint press releases showing how the companies have made '3G' into a brand name ideally suited for amnesiac consumers. Meanwhile, no cell carrier is foolish enough to sell you bottom-line throughput like an ISP in 1996 — you could actually hold them to that (PDF)."
Re:4G? (Score:5, Informative)
Uhhh, wasn't that the iPhone 4, not the iPhone 4G?
Re:3G/4G (Score:4, Informative)
http://en.wikipedia.org/wiki/3G [wikipedia.org]
Re:3G and 4G is consumer friendly (Score:2, Informative)
...
You saw a picture on the Internet from some Android dev phone that said WCDMA on it ... and so you inferred from that ... that AT&T doesn't use GSM, it uses CDMA ...
You are, without a doubt, an idiot.
Considering the number of times I've carried my phone between AT&Ts network and Europe ... and simply swapped sim cards ... or that the frequencies the AT&T phones all use are GSM freqs ... or ... you know what, why bother ... you saw some image on the Internet, it must be true, everyone else must be confused.
Re:4G? (Score:5, Informative)
What about Sprint? (Score:5, Informative)
Sprint, at least is calling its LTE [wikipedia.org] network "4G", as it rolls it out.
As I understand it:
As I see it, the xG shorthand is a way to track the evolution of the network, link level, and physical layers. Every time one of those changes, you get a new "generation" of cell phones.
Re:4G? (Score:5, Informative)
No. Especially since this iPhone 4G thing came out. It was in the news, you might have heard about it.
The iPhone 4 supports 3.5G (HSPA+)
http://www.google.com/search?q=3.5g+iphone+4 [google.com]
4G is the new 3G
It's all just marketing talk and the details are buried in the fine print
Re:Not really... (Score:5, Informative)
No, I've also not seen that. When they introduced GPRS, it was 2.5G. When they introduced UMTS, it was 3G. Then some companies rolled out EDGE because Apple insisted on using ancient crappy standards that everyone else had skipped for compatibility with backwards networks in the USA, and it was 2.75G. Then they deployed various HSPA variations, and they were mostly 3.5G. A few places are deploying LTE or WiMax, and this is 4G, or 3.9G if it doesn't quite meet the requirements of 4G.
2G was well defined, as meaning digital. 4G is also well defined, with features like an all-IP network, 100Mb/s mobile bandwidth (1Gb/s stationary), and so on. 3G is not so well defined, but it's generally understood to mean something in the same category as UMTS.
Maybe the confusion is just a US thing?
Re:What about Sprint? (Score:3, Informative)
Sprint is working on 4G WiMax, which is a completely different thing than LTE. Everyone else (Verizon, AT&T) are going to be moving to LTE, and Sprint [1] has made random mentions of supporting LTE eventually as well. T-Mobile is going to be moving to LTE, but as of now, they are getting their "3.5G" stuff[2] out there in the interim.
My hope: The cell companies get a ton of tower sharing agreements and get LTE deployed widely. Not just metro areas, but in the sticks where I get almost no coverage, or if I do get coverage, it will be GPRS. This way, we can dispense with devices that have two versions of GSM 3G, CDMA devices with no R/UIM, iDen stuff, and just have phones that "just work" regardless of provider.
[1]: Sprint has a lot of wireless networks. CDMA, GSM (for people traveling abroad with "world phones" that have dual radios), iDEN, WiMax, and LTE. Just the fact they have so much real estate makes them going to be in business 5-10 years from now.
[2]: It can be argued that HSPA+ is faster than Sprint's WiMax. The main differences is that HSPA+ has two channels, one for voice, and one for data, and 4G does VoIP and puts everything as data.
Re:Not really... (Score:5, Informative)
A few places are deploying LTE or WiMax, and this is 4G, or 3.9G if it doesn't quite meet the requirements of 4G.
Ah, er, what? TFA explains it this way "You might notice that Sprint is currently selling Mobile WiMAX as “4G.” Mobile WiMAX is part of IMT-2000 — the 3G standard. Verizon Wireless is selling something called “LTE” as “4G” — it ain’t in IMT-Advanced either. Today’s “4G” products are like the “3G” of 2002 and 2003 — they will become “3.75G” as soon as the next hot thing comes out."
So, everything called 4G today is a lie vs the ITU spec in IMT-Advanced. Faster than 3g, possibly, but not 4G in any stretch of the imagination (unless you are in sales). Sounds like you've been sold. Give TFA a try, it's a good read!
Re:3G and 4G is consumer friendly (Score:5, Informative)
It is common to refer to phones that us SIM cards as "GSM" phones, because they work on networks that are GSM. And it is common to refer to phones that use no SIM cards as "CDMA", because they work on networks that are CDMA. So you're still an idiot, you may be right, but you're still an idiot.
Re:3G/4G (Score:3, Informative)
To the consumer, 2G means slow data rates, 3G means faster data rates, and 4G means even faster data rates, and that's it. They should think that, that's how it's been marketed to them. To cell network engineers, apparently, those terms mean something entirely different. Seems like a lesson in the value of not reusing the same terms for engineering and marketing.
Re:What about GSM? (Score:3, Informative)
Meh, the business bullshitters in charge also use the G, mostly to stand for "Generation". So the parent is mostly correct in that context.
Verizon / Sprint started as CDMA (code division multiple access, GPS satellite signals also use this) networks, vs. everyone else who started as GSM use TDMA (time division multiple access).
In CDMA, all units basically transmit on the same wide frequency, but have a unique code to distinguish their signal from others. In TDMA, all the units get timeslices (~120 per second) and narrower frequency bands, and transmit bursts of packets during their allotted timeslice. That's why you can hear GSM phones cause audible humming (apparently at 217Hz) when you place them near an amplified speaker. Also made GSM phones theoretically more energy efficient, since they don't have to broadcast the carrier wave the entire time they transmit.
http://www.smartdevicecentral.com/article/that+crazy+gsm+buzz/199379_1.aspx [smartdevicecentral.com]
Originally CDMA might have been a bit better for sparse country networks, and GSM better suited for densely populated city networks, but with the new standards emerging around the "3G" timeframe, they both pretty much incorporated each other's technologies into the newer WCDMA standards.
Here's my dicey understanding of the GSM generations:
(See the bottom of http://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution [wikipedia.org] for the actual standards lumped under each G)
POTS (Plain old telephone service) : 64kbps line that carries uncompressed 8kHz 8-bit mono audio (that's why phone calls sound like crap when they're on TV / Radio talk shows). Also sort of explains why the fastest dialup modems were around 56k (after data protocol and error correction overhead).
1G AMPS: the old analog(ue) brick mobile phones the rock stars used in the 80s
GSM 2G voice: 8kHz 8-bit mono audio compressed using some codec that allows them to fit it in a ~7kbps - ~13kbps stream at roughly the same audio quality, except with compression artifacts. Different phones would support different codecs, but would fall back to some lowest common denominator. That's why some mobile calls sounded like crap while others sounded somewhat better. The data mode was called 3GPP (ha! 3G before the new meaning of 3G!) and could give you roughly the same data rates.
GSM 2.5G data: Then GPRS came along and gave you 56-114kbps, I think mostly by allowing you to use more timeslots if no one else was using them.
GSM 2.5G data the second: EDGE came along and gave you ~240kbps, mainly by squeezing more data bits into the carrier wave.
GSM 3G makes it more CDMA-like, where it can also use more of the frequency spectrum to pack bits. So now you can hog up to 1Mbps from the spectrum by using more timeslots and more of the available spectrum bandwidth.
GSM 4G: I'm not really sure where they're going with LTE Advanced, but more of the same, probably. Which means we'll probably have bunch more 3.5G brandings running around for a bit.
I rolled out 2.5G and 3G on CDMA, let me explain (Score:3, Informative)
First off, there's no technical article that's going to be worse than a person who has no idea what he's talking about, and who's basing his observations on technical details as given by a salesperson. From what I RTFA, it's the basis of this discussion, but it can't be. Using the typical car anaology, you've built a race car with no tires.
First off, 3G is a generic term. If I say 3G for wireless telecomm, I'm referring to CDMA2000, which is a 3rd generation of wireless data protocol. 2.5 G was never really accepted as 3G because it didn't implement all the standards, such as real time allocation, and it was circuit switched packet data (laymans terms: wireless modem). Getting back to "3G", a third generation of iPhone can be called 3G, but still work on the 4th generation of wireless standards, right next to a 4th generation iPhone (4G) running on an older 3G data network (Sprint, whoever). In an attempt to keep this discussion simple, we'll just stick to the wireless, 3rd generation data format when saying, "3G."
Before 3G data was sent over the air on dedicated channels. If you wanted to have more data, you set asside more time, or codes (TDMA or CDMA). However if network modeling was bad, you either banged on the headroom for data (surfing Google took longer), or voice (calls didn't go out or come in). Carriers in the US from my observation are always giving priority to voice. So the common configuration was to give them more "pipe" and higher priority.
Enter 3G CDMA, aka CDMA 2000. Initially there was only one way to implement 3G, later developers came up with newer formats that were backwards compatible in most cases, such as EV, EV-D, and EV-DO. These all have meanings, feel free to Google. In a nutshell though, they're all different implementations of 3G. 3G, or CDMA2000, allows the cell site to allocate pipes by usage and type. So, if you're data surfing at 1am, when no one is around making voice calls, you get the full pipe and your data screams. Use the same phone, on the same cell site at 12 noon, and you get the minimum pipe, and if everyone's on voice calls, you may not get out at all until a slot opens up. This is not to be confused with "breathing" (where cell sites expand and contract RF coverage according to usage). That's at the RF, or Layer 1 if you will.
When you start mingling WiMax and other technologies, you're now blurring the usage of the term. WiFi is not typical CDMA (I'm only hedging with "typical" because I don't know what modulation method wifi uses). Back to car analogies, it's like buying a 2009 car, putting a 2010 engine in it, and calling it a 2010. Yes part of it is a new generation, but it's still a 2009. Adding Wifi to a CDMA phone didn't take it from 3G to 4G, so from a logical techology standpoint, going WiMax isn't either. It's a different format, frequency, and usage.
Eventually, all these technologies will blur and the author will be correct in being confused. The telecom manufacturers (lucent, nortel, etc) have been moving the "ip up the train." In the beginning, they went out a specific trunk to a rack mounted shelf of modems (2.5 G, circuit switched packet data) which either went into another backend, or out a plain old telephone line (POTS). With the original implementation,, data shared RF with voice, came in the tower, went through the switch, which then split out data out a PRI interface (T1) to a server which converted over to TCP/IP and then used Home/Foreign Agents to manage real-time changing points of connection within a network. In laymans terms, you could jump in your car in San Diego, fire up your laptop, and drive from SD to New York without changing the IP address your laptop was assigned. When I left telecom (early 2000s), they were rolling out IP from the Site Controllers back. Meaning, the Mobile Switch back at the main office didn't break it out. The eventual plan back then was IP from the cell site. Everything coming out was TCP/IP, regardless of data or voice. 3G still all applies, because