Introduction to 4G/LTE and carrier aggregation.

4G and LTE are terms that are often use interchangeably, but there are some significant differences between them.

An introduction into 4G/LTE

LTE is a standard that was developed by the 3GPP (3rd Generation Partnership Project) and was first commercially deployed in December 2009 in Stockholm and Oslo by Telia.

4G is a specification defined the United Nation's International Telecommunication Union (ITU). In a nutshell, it requires:

  • peak throughput of 100 Mbps for rapidly moving devices (cars, trains, etc.)
  • peak throughput of 1 Gbps for slowly moving devices (pedestrians)

What's the difference between 4G and LTE?

While many people refer to 4G and LTE interchangably, they are different.

The 4G specification defines a minimum theoretical speed, but for a long time LTE networking infrastructure couldn't actually meet these speeds. This didn't stop networks from branding their LTE networks as "4G" or "4G LTE", however. It wasn't until LTE-Advanced (connecting to LTE on multiple frequencies at once) was deployed that LTE could meet 4G's specifications and call itself 4G.

A lot of confusion stems from the fact that some networks in the USA and Canada branded some evolved versions of their 3G networking (namely HSPA+) "4G", despite it still actually being 3G.

When these networks then started rolling out real 4G infrastructure, they were left with an issue: they had already released 4G, so they couldn't actually call 4G by its actual name without confusing customers. Some networks chose to brand services as "4G LTE", while others chose even more confusing names, such as "5Ge" on AT&T.

Eventually, most consumers and networks shortened this to just "LTE", resulting in the confusing system we have today. Thankfully, these schenanigans seem to have fizzled away with 5G.

North AmericaRest of World
4GHSPA/HSPA+ (still 3G)
LTE/4G LTE4G LTE (trials only)

What is LTE-Advanced (4G+)?

LTE-Advanced is the first version of LTE to truly comply with the 4G specification.

LTE-A does this by including special technology called carrier aggregation (CA). CA allows your device to communicate with a 4G LTE network on multiple frequencies at the same time. For example, in the UK on Vodafone, your phone would likely connect to bands 7 and 20 at the same time, aggregating their theoretical throughput (speed). By doing this, it can significantly increase the theoretical speed available to users.

There are different types of carrier aggregation: intra-band contiguous; intra-band non-contiguous; and inter-band non-contiguous. These sound far more complex than they really are.

Intra-band contiguous

Your phone makes multiple connections on a single frequency band, in one continuous block of frequencies.

Diagram of intra-band contiguous carrier aggregation

Intra-band non-contiguous

Your phone makes multiple connections on a single frequency band, in one or more blocks of frequencies.

Diagram of intra-band non-contiguous carrier aggregation

Inter-band non-contiguous

Your phone makes multiple connections on two or more frequency bands.

Diagram of inter-band non-contiguous carrier aggregation