What you really need to know about 4G LTE

As the hype around 4G cellular networks begins to really heat up — AT&T, Sprint, T-Mobile, Verizon Wireless, and even cheapo carrier Metro PCS are flogging its faster speed and greater bandwidth in their ads — it’s time to be clear on what 4G really does for you and if it’s worth factoring into your smartphone and tablet plans. The short answer: not yet.

4G means fourth-generation; today’s devices and cellular networks use a mix of third-generation (3G) and late second-generation (2.5G) technologies. Even after a decade of 3G availability, we all know how often that 3G symbol on our iPhones or Androids goes away, replaced with an icon indicating a slower, 2.5G network such as EDGE or GPRS. Certainly, 3G isn’t where it needs to be yet, and now you’re being sold 4G.

First, let’s sort out what 4G really means
Per the definition of the standards body International Telecommunications Union, a 4G network is supposed to deliver at least 100Mbps throughput from a fast-moving vehicle such as a car or train or 1Gbps from a stationary position. It’s also supposed to abandon the spread spectrum technology used in 3G networks for frequency-division technologies such as OFDMA that basically packetize network traffic much as the Ethernet protocol does for LANs. That way, individual channels aren’t hogged up by individual connections as happens today.

There are no 4G networks on the market today that do these things. The two standards that meet these requirements are LTE-Advanced and WirelessMAN-Advanced, neither of which is anywhere near real-world deployment.

But there are three technologies that get the 4G label in the carriers’ marketing, and for the next three to five years at least, they’ll be what 4G means in a practical sense. They are LTE, WiMax, and HSPA+ with backbone assist. After the ITU said none of these networks qualified as 4G last year, its carrier members quickly twisted arms and got the ITU to claim that “precursor” technologies leading to these standards could use the 4G label. That means LTE and WiMax.

HSPA+ doesn’t count because it is simply a faster version of the HSPA 3G technology long used by AT&T and T-Mobile. Both carriers claim that combined with a faster backbone network in some locations, HSPA+ speeds can equal those of LTE. That may or may not be true at any specific location, but it doesn’t matter. As carriers move to first “precursor” 4G technologies and then true 4G, 3G technologies are nearly at the end of their capabilities. Today’s faux 4G from AT&T and T-Mobile will not fool anyone in a few years.

AT&T knows that, which is why it is planning its first LTE deployments later this year. T-Mobile is likely to be absorbed into AT&T, so its customers will get LTE that way. If the feds somehow grow a spine and block that acquisition, current owner Deutsche Telekom has been starving T-Mobile for years of capital infrastructure funds, so T-Mobile is likely to ride its faux 4G for the foreseeable future.

LTE is deployed today in parts of some cities by Verizon Wireless and Metro PCS. Sprint too recently adopted LTE by partnering with a new infrastructure provider named LightSquared that gained notoriety for a proposed deployment approach that could have scrambled GPS signals (unsurprisingly, that proposal has since been adjusted). LTE is also forward-compatible with LTE-Advanced, the 4G versions likely to come next in the United States; any LTE devices in use when LTE-Advanced makes its debut should continue to function on it.

Sprint is also a partner in Clearwire, a company that has deployed WiMax networks in several dozen U.S. cities. However, that partnership is on the rocks, and Clearwire is now belatedly looking to joing the LTE club. WiMax is more like Wi-Fi than LTE in its underlying technology approach, which means it requires unique radios in devices that use it. Thus, very few smartphones or mobile hotspots can use WiMax. This means WiMax is essentially a dead end for those yearning for 4G’s promised faster speeds.

LTE is clearly the only route to 4G, but it’s not a single road
It should be obvious that, carrier marketing aside, LTE technology will be the first real move to 4G networks.

Already, several Android smartphones come with LTE radios in addition to 3G radios; if you live in an area with LTE and prefer Android, you can be one of the first to ride the faster 4G wave. Available now are various LTE-enabled Android smartphones from HTC, Motorola, and Samsung, plus an LTE version of the Samsung Galaxy Tab 10.1. Expected next month is the LTE-enabled Motorola Mobility Xoom tablet. A BlackBerry Curve model is also widely expected to be available in an LTE edition next month, and RIM may also ship its promised LTE-based BlackBerry PlayBook tablet by the Christmas holidays.

Apple has been mum on its LTE plans from the iPhone. Although some rumors say the expected iPhone upgrade coming this fall will sport an LTE radio in addition to 3G, I suspect it’ll be 2012 before Apple enters the LTE arena, once the radio parts are more proven and the LTE networks are more widely deployed.

You might think that once all the carriers have adopted LTE, you’ll be able to buy a smartphone, tablet, or mobile hotspot and use it with the carrier of your choice.

Think again. LTE devices will be as tied to carriers as CDMA devices are to Sprint or Verizon and as GSM devices are to AT&T or T-Mobile. This is not necessarily a technical issue with LTE, just as it is not with GSM, as evidenced by the many countries that forbid such tie-ins — which explains why you can move an unlocked phone across carriers in many countries.

In the United States, a major reason for the lock-in is the fact that carriers have licensed different bands of the 4G radio spectrum, as they have with the 3G spectrum. Thus, the 3G radios in an AT&T device access different radiofrequency bands than those in a T-Mobile device, though both companies use the same GSM technology. That’s why an unlocked AT&T iPhone accessing a T-Mobile network must use 2.5G frequencies. The same is true across the major CDMA carriers: Sprint, Verizon, and Metro PCS. Verizon has said that this radiofrequency divide will continue into LTE, and LTE devices designed for competitors won’t work on its LTE network and vice versa.

There is of course a straightforward solution to the radiofrequency divide: the use of radios that access all 3G and LTE spectrum bands. That’s what a “world” phone’s radio does. Such radios cost a litle more, but the real reason they are not standard is that the U.S. carriers don’t want their customers to be able to easily change providers, as they can in other parts of the world. Mobile device makers — even Apple, though to a lesser extent — design their device models specifically for each carrier to honor such customer lock-in requirements.

There you have it: the truth about 4G in general and LTE in particular. 4G is coming, but slowly and in a way that perpetuates today’s carrier lock-in strategies. I wouldn’t make 4G compatibility a litmus test for choosing a new smartphone, tablet, or mobile hotspot, but if a device you happen to like for the carrier you prefer is available in a 4G model, give it serious consideration. After all, the 3G parts also work.