Right off the bat, I will tell you that this is not a super-technical article. If you want one of those, you won’t get much better than this long essay at ExtremeTech that really goes into the aspects of LTE that you would want to know before going into a first-year RF engineering class. This article is really for those of you who want to sound good at parties or impress your less technical friends when you’re at parties.
The first thing you need to know is that LTE is primarily a data technology. Unlike other technologies that started as voice systems, LTE is a more-or-less completely new way of looking at the way that data gets to a mobile device. That’s not to say it’s completely different, because at its very basic level it’s compatible with GSM, the mobile standard used in Europe and by AT&T and T-Mobile here in the US. LTE came about when the GSM committee decided on a plan for the “long term evolution” of its standard, keeping in mind that the future of mobile telephony was data-based, not voice based. They built standards to maximize data and then found ways to do voice over those standards. This is completely different from the way that things were done in the past.
There are some special things about LTE technology that set it apart. It is compatible with GSM, so carriers that use GSM technology for voice can implement it easily. It’s compatible in the sense that the transmitting equipment is essentially the same, although voice GSM is transmitted at a different frequency than LTE. A carrier like AT&T can put LTE into place more easily because its towers are already spaced at the right distance, and the transmission systems work well together. A carrier like Verizon needs to find new cell sites for LTE because it travels at smaller distances than CDMA, the voice technology used in Asia and by Verizon.
A major breakthrough with LTE is that it uses a pair of broadcast frequencies, one for downloads and one for uploads, and these can be optimized to take advantage of the fact that most users crave download speed and don’t care much about uploads. This allows for a much more efficient use of the limited amount of broadcast spectrum available. LTE also is designed for aggregation, meaning that you can actually be using two different broadcast bands at the same time to allow for even faster transfers when there’s some available bandwidth. This aggregation technology allows carriers to buy random little chunks of spectrum and use them as needed, where in the past you needed to have a really big chunk of spectrum for everyone to use.
Ultimately, LTE is going to make all phones in the US more compatible and simpler, as it eventually allows carriers to wind down their pre-LTE networks. This means that more equipment will work with all carriers, assuming it has the radio technology to broadcast and receive on all the different frequencies used. Already, many high-end smartphones can be used interchangeably on the AT&T, T-Mobile, and Verizon networks because all those carriers do use very similar types of LTE implementations. However, this one-for-all plan currently only works in areas where all carriers have implemented the latest LTE technologies, like Voice over LTE which will let you make voice calls using the LTE radios.
Voice-over-LTE is really just a gateway to the big goal, which is “Everything over LTE.” LTE is, when you get right down to it, the real third generation of mobile telephony, even though marketing departments already stole the term “3G” for earlier data implementations. If you look at things really broadly, you had analog (AMPS) phones until the mid-2000s, and then they were replaced by digital (GSM/CSMA/TDMA) phones, and as we get closer to the 2020s, expect phones that are LTE-only, keeping costs and weight down and improving battery life.