Source: Pcmag.com/

For average consumers, ‘3G’ and ‘4G’ are two of the most mysterious terms in the mobile technology dictionary, but they’re used relentlessly to sell phones and tablets. If you’re shopping for a new phone, the answer isn’t clear-cut, and you shouldn’t always go for the higher number. Our primer will help explain which technology to pick.

3G vs. 4G: What Are They?
First things first, the “G” stands for a generation of mobile technology, installed in phones and on cellular networks. Each “G” generally requires you to get a new phone, and for networks to make expensive upgrades. The first two were analog cell phones (1G) and digital phones (2G). Then it got complicated.

Third-generation mobile networks, or 3G, came to the U.S. in 2003. With minimum consistent Internet speeds of 144Kbps, they were supposed to bring “mobile broadband.” There are now so many varieties of 3G, though, that a “3G” connection can get you Internet speeds anywhere from 400Kbps to more than ten times that.

New generations usually bring new base technologies, more network capacity for more data per user, and the potential for better voice quality, too.

4G phones are supposed to be even faster, but that’s not always the case. There are so many technologies called “4G,” and so many ways to implement them, that the term is almost meaningless. The International Telecommunications Union, a standards body, tried to issue requirements to call a network 4G but they were ignored by carriers, and eventually the ITU backed down. 4G technologies include HSPA+ 21/42, WiMAX, and LTE (although some consider LTE the only true 4G of that bunch, and some people say none of them are fast enough to qualify.)

There’s one rule to follow: Each generation will offer faster Internet speeds than the last, that is, on the same carrier. Sprint’s WiMAX 4G is almost always faster than its CDMA 3G. But AT&T’s 3G HSPA can be faster than MetroPCS’s 4G LTE. You can rely on speeds to move up within your carrier, though.

This confusion is why we run our annual Fastest Mobile Networks story, which tests 3G and 4G networks in 20 cities nationwide. In last year’s tests, we generally found that Verizon’s 4G LTE network was the fastest, followed by T-Mobile 4G HSPA+, AT&T 4G HSPA+, Sprint 4G WiMAX, MetroPCS 4G LTE, Verizon 3G, and Cricket 3G, with Sprint 3G pulling up the rear. As AT&T and Sprint roll out new LTE networks, we expect them to be competitive with Verizon’s LTE speeds.

Check out Fastest Mobile Networks 2011 to find out which 3G or 4G network is fastest in your city.

Would you like to know more about LTE, which is becoming the global standard for 4G? Read our primer on What Is LTE? over at ExtremeTech.

When to Go For 4G
The mobile carriers are still building out their 4G networks, so first, you need 4G coverage to appreciate a 4G phone. Of the national carriers, Verizon and T-Mobile have the broadest 4G coverage. AT&T currently covers about a quarter of the U.S. population.

Sprint is in the middle of switching 4G systems, from WiMAX to LTE. The two are incompatible, so you must check coverage in your city for the specific variety of 4G you’re buying.

If you like to surf the Web and especially stream video, 4G can be heaven. If you connect a laptop to your mobile link, 4G makes a huge difference. In general, anything involving transferring large amounts of data gets a big boost from 4G. Watch out for the data limits on your service plan, though; it’s easy to use up a lot of data very quickly with 4G.

If you have a 3G phone and you’ve been frustrated with clogged-up networks, 4G may be the solution. You’ll be switching to a different, less-trafficked network for your Internet data. 4G won’t solve any dropped call problems, though, as all calls will be made over 3G networks until carriers switch to voice-over-LTE during the next few years.

Finally, if you want to future-proof yourself, get a 4G phone. 4G coverage is only going to get better, and that’s where the carriers are spending most of their money right now. As we move into 2013 and 2014, some carriers will even try to switch subscribers to 4G-only phones which make voice calls over the LTE network.

When to Buy 3G
If you want an iPhone, it’ll be 3G. End of story. We’re done. Apple may be releasing a 4G LTE iPhone later this year, but the company doesn’t currently have a 4G model. (The “4” in iPhone 4 refers to the model number, not the mobile technology.)

If you live in an area that doesn’t have 4G coverage, there’s no advantage to a 4G phone. In fact, you’ll have serious battery life problems if you buy an LTE phone and don’t disable 4G LTE, as the radio’s search for a non-existent signal will drain your battery quickly.

In general, if you value battery life more than Internet speeds, there’s still life in 3G yet. We’ve seen significantly shorter usage times on 4G devices than on 3G devices, most notably on Verizon and Sprint phones. (Our LTE explainer goes into detail as to why that’s the case, and why T-Mobile’s HSPA+ 42 is currently the least battery-hogging form of 4G.) We’ll see that situation improve over the next two years as integrated 3G/4G chips arrive, and then as carriers switch to 4G for voice calling. Of course, you can also buy a 4G phone and turn the option off using a menu option or downloaded app.

I hope this clears up the 3G vs. 4G dilemma. If you have anything to add, please continue the discussion in the comments below.

Source: Pcmag.com/

Two basic technologies in mobile phones, CDMA and GSM represent a gap you can’t cross. They’re the reason you can’t use AT&T phones on Verizon’s network and vice versa. But what does CDMA vs. GSM really mean for you?

CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for the two major radio systems used in cell phones. Both acronyms tend to group together a bunch of technologies run by the same entities. In this story, I’ll try to explain who uses which technology and what the real differences are.

Which Carries are CDMA? Which are GSM?
Five of the top seven carriers in the U.S. use CDMA: Verizon Wireless, Sprint, MetroPCS, Cricket, and U.S. Cellular. AT&T and T-Mobile use GSM.

That means we’re mostly a CDMA country. It also means we’re not part of the norm, because most of the world is GSM. The global spread of GSM came about because in 1987, Europe mandated the technology by law, and because GSM comes from an industry consortium. What we call CDMA, by and large, is owned by chipmaker Qualcomm. This made it less expensive for third parties to build GSM equipment.

There are several variants and options carriers can choose, like toppings on their technological ice cream. In this story we’ll be talking about U.S. networks.

What CDMA vs. GSM Means to You
For call quality, the technology you use is much less important than the way your carrier has built its network. There are good and bad CDMA and GSM networks, but there are key differences between the technologies. Here’s what you, as a consumer, need to know.

It’s much easier to swap phones on GSM networks, because GSM carriers put customer information on a removable SIM card. Take the card out, put it in a different phone, and the new phone now has your number. What’s more, to be considered GSM, a carrier must accept any GSM-compliant phone. So the GSM carriers don’t have total control of the phone you’re using.

That’s not the case with CDMA. In the U.S., CDMA carriers use network-based white lists to verify their subscribers. That means you can only switch phones with your carrier’s permission, and a carrier doesn’t have to accept any particular phone onto its network. It could, but typically, U.S. carriers choose not to.

In other words, you can take an unlocked AT&T phone over to T-Mobile (although its 3G may not work well because the frequency bands are different). You can’t take a Verizon phone over to Sprint, because Sprint’s network rejects non-Sprint phones.

3G CDMA networks (known as “EV-DO” or “Evolution Data Optimized”) also, generally, can’t make voice calls and transmit data at the same time. Once more, that’s an available option (known as “SV-DO” for “Simultaneous Voice and Data Optimization”), but one that U.S. carriers haven’t adopted for their networks and phones.

On the other hand, all 3G GSM networks have simultaneous voice and data, because it’s a required part of the spec. (3G GSM is also actually a type of CDMA. I’ll explain that later.)

So why did so many U.S. carriers go with CDMA? Timing. When Verizon’s predecessors and Sprint switched from analog to digital in 1995 and 1996, CDMA was the newest, hottest, fastest technology. It offered more capacity, better call quality and more potential than the GSM of the day. GSM caught up, but by then those carriers’ paths were set.

It’s possible to switch from CDMA to GSM. Two carriers in Canada have done it, to get access to the wider variety of off-the-shelf GSM phones. But Verizon and Sprint are big enough that they can get custom phones built for them, so they don’t see the need to waste money switching 3G technologies when they could be building out their 4G networks.

The Technology Behind CDMA vs. GSM
CDMA and GSM are both multiple access technologies. They’re ways for people to cram multiple phone calls or Internet connections into one radio channel.

GSM came first. It’s a “time division” system. Calls take turns. Your voice is transformed into digital data, which is given a channel and a time slot, so three calls on one channel look like this: 123123123123. On the other end, the receiver listens only to the assigned time slot and pieces the call back together.

The pulsing of the time division signal created the notorious “GSM buzz,” a buzzing sound whenever you put a GSM phone near a speaker. That’s mostly gone now, because 3G GSM (as I explain later) isn’t a time division technology.

CDMA required a bit more processing power. It’s a “code division” system. Every call’s data is encoded with a unique key, then the calls are all transmitted at once; if you have calls 1, 2, and 3 in a channel, the channel would just say 66666666. The receivers each have the unique key to “divide” the combined signal into its individual calls.

Code division turned out to be a more powerful and flexible technology, so “3G GSM” is actually a CDMA technology, called WCDMA (wideband CDMA) or UMTS (Universal Mobile Telephone System). WCDMA requires wider channels than older CDMA systems, as the name implies, but it has more data capacity.

Since its inception, GSM has had many more add-ons and evolutions than CDMA. As I mentioned above, WCDMA is considered the 3G version of GSM technology. To further speed things up, the 3GPP (the GSM governing body) released extensions called HSPA, which have sped GSM networks up to as fast as 42Mbps, at least in theory.

Our CDMA networks, meanwhile, are stuck at 3.6Mbps. While faster CDMA technologies exist, U.S. carriers chose not to install them and have instead turned to 4G LTE to be more compatible with global standards.

The Future is LTE
The CDMA vs. GSM gap will close eventually as everyone moves to 4G LTE, but that doesn’t mean everyone’s phones will be compatible. LTE, or “Long Term Evolution,” is the new globally accepted 4G wireless standard. All of the U.S. carriers are turning it on. For more, see 3G vs. 4G: What’s the Difference?.

The problem is, they’re turning it on in different frequency bands, with different 3G backup systems, and even, in Clearwire’s case, using an LTE variant (TD-LTE) that doesn’t work with any other U.S. carrier’s phones.

Furthermore, it’s not like the 2G and 3G networks are going away any time soon. Carriers have told us they’re leaving their UMTS and EVDO networks live until at least 2020. So we will not enter a European-style paradise of interchangeable phones anytime soon.

So what does all of this mean for you? If you want to switch phones often, use your phone in Europe, or use imported phones, go with GSM. Otherwise, pick your carrier based on coverage and call quality in your area. Our Readers’ Choice and Fastest Mobile Networks awards are a great place to start.