LTE stands for Long Term Evolution, and is a protocol for wireless high speed data communications which is developed and standardized by the Third Generation Partnership Project, or 3GPP. LTE was originally put forward by Japanese carrier NTT DoCoMo (it is now trying to promote “5G”), and it was only in late 2009 that the first live networks were launched in Norway and Sweden. At the time of publishing (Dec 2014), South Korea currently has the most advanced LTE network in the world.
LTE is commercially called “4G LTE” or “4G” depending on the country and the carriers. The “4G LTE” term has been used because a number of carriers used “4G” to name wireless protocols that were really 3.5G (HSPA+ or WiMax) for marketing reasons. This is mainly a marketing tactic that started in America, but you may find the same terminology used abroad.
As LTE took over in terms of speed and long-term prospect of evolution, 4G is no longer used for lesser protocols in countries where LTE is growing fast.
At first, the cost of LTE technology was the main reason why carriers were reluctant to deploy it. Historically, Verizon Wireless has been the first carrier to deploy it in the U.S.A (with the HTC Thunderbolt). Later on, the ongoing cost reduction makes it possible for carriers to actually save on infrastructure costs with LTE deployments, and that is when LTE’s adoption has really accelerated.
“LTE” is a broad term, and the technological foundation will remain for a long time, so in order to differentiate between several LTE evolutions, the industry is using different LTE Categories to describe the LTE network capabilities. There are 11 different categories that are defined, and from a consumer perspective, they mainly differ in terms of theoretical speed. See the table below (source = Wikipedia):
|User equipment category||Maximum L1 datarate
number of DL MIMO
|Maximum L1 datarate
|Category 0||1.0||1||1.0||Rel 12|
|Category 1||10.3||1||5.2||Rel 8|
|Category 2||51.0||2||25.5||Rel 8|
|Category 3||102.0||2||51.0||Rel 8|
|Category 4||150.8||2||51.0||Rel 8|
|Category 5||299.6||4||75.4||Rel 8|
|Category 6||301.5||2 or 4||51.0||Rel 10|
|Category 7||301.5||2 or 4||102.0||Rel 10|
|Category 8||2,998.6||8||1,497.8||Rel 10|
|Category 9||452.2||2 or 4||51.0||Rel 11|
|Category 10||452.2||2 or 4||102.0||Rel 11|
|Category 11||603||2 or 4||51||Rel 11|
|Category 12||603||2 or 4||102||Rel 11|
|Category 13||391.7||2 or 4||150.8||Rel 12|
|Category 14||3,917||8||9,585||Rel 12|
|Category 15||750||2 or 4||226||Rel 12|
|Category 16||979||2 or 4||N/A||Rel 12|
|Category 17||25,065||8||N/A||Rel 13|
|Category 18||1174||2 or 4 or 8||N/A||Rel 13|
|Category 19||1566||2 or 4 or 8||N/A||Rel 13|
Note that these speeds are maximum theoretical numbers, which are used to compare the maximum potential of the technology under ideal conditions (like transmission happening over less than 1 meter distance,etc.c…). The Maximum L1 datarate can also rely on one of more channels, which may or many not be available.
In practical terms, we would not suggest to purchase only based on the LTE category, but if all else is being equal, this is an interesting factor that can make a difference. More likely, most devices from the same generation, and the same price point will feature similar radio capabilities.
LTE Bands and compatibility
The LTE Bands (radio frequencies) can be arguably more important to you for three main reasons:
- Use your phones on different networks/countries
- Switch carriers and still have good LTE support
- Resell your phone to a potentially larger market
Although the core LTE technology is very similar worldwide, each country has allocated different bands (frequencies) for wireless carriers to carry LTE data. This is very messy, and very much unlike WiFi, which uses the same radio frequency worldwide. 3G was also much less fragmented from that point of view.
You can read more about TDD vs. FDD, but the short story is that TDD uses less radio spectrum, and is therefore suited for places where there was not as much available spectrum to use. Most of the world uses FDD and TDD is used when FDD is inconvenient. In general, you don’t have to worry about it, except if you go to a country where they use TDD.
Why such a large number of bands?
The proliferation of LTE bands is mostly due to governments worldwide rushing to auction radio frequencies for billions of dollars, without concerting one another and without enough planning. In the rush, we have been left with a messy 44 LTE Bands. On top of that, LTE has split into two families, FDD (frequency division duplex) and TDD (time division duplex), which are not compatible.
You can look at the specifications of your device (Example: Galaxy S5 specs) to see which bands it supports. From there, you can figure out if LTE support is possible with a specific carrier or network.
At first, devices only supported a couple of bands, which made things very difficult to launch new hardware worldwide because each version required a different assembling process. However, as time went on, wireless companies built technologies to support more and more bands.
Qualcomm’s RF360 is one such technology, but the whole industry is working towards supporting as many as they can in a single device. Ideally, a single device could work on every single LTE band. However, much work needs to be done.