What is LTE and how does it work?

When you are looking for any 4G products like smartphones, dongles or other SIM-enabled devices, you are likely to come across a term ‘LTE’. This term may be confusing for some people especially if you are not fully conversant with the relationship between 4G and LTE.

LTE stands for Long Term Evolution and it is the leading technology that enables the fourth generation of mobile networks or 4G. It makes efficient use of the network resources, reduces the latency in data transfer, and also reduces the overall network complexity. LTE provides 4G migration paths for key 3G technologies including Universal Mobile Telecommunication System (UMTS) and CDMA2000.

How does LTE work?

While LTE is the leading technology that enables 4G, it is not the only one that can allow mobile operators to move to 4G. There is another technology called WiMax (Worldwide Interoperability for Microwave Access) that also provides a path for the 4G upgrade. However, LTE has been the primary technology used worldwide for 4G because it allows operators both on GSM/UMTS and cdmaOne/CDMA2000 to migrate. As a result, LTE can be seen as a step towards streamlining the mobile network evolution. It makes efficient use of the network resources, reduces the latency in data transfer, and also reduces the overall network complexity.

If you look at the high-level network diagram below, you may notice that the radio network in 4G is a bit leaner as compared to that in the 3G UMTS network. GSM and UMTS networks have BSC (Base Station Controller) and RNC (Radio Network Controller) respectively to provide the radio network control function, but in 4G, this responsibility sits with the 4G base station eNodeB.

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In 2G and 3G networks, the conventional voice calls are only possible through the circuit-switched part of the network. LTE networks have the Voice over LTE (VoLTE) capability to provide voice calls through the packet-switched part of the network. However, there is a circuit-switched fall-back option that mobile operators often use for voice calls. More about VoLTE in this dedicated post.

Unlike GSM and UMTS networks, LTE uses separate multiple-access technologies for the uplink and the downlink. It uses Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink. More about OFDMA in this dedicated post.

How fast is LTE?

The data speed you get with LTE depends on which flavour of LTE your mobile operator offers and how they have deployed it. There can be multiple deployment combinations with variations to channel bandwidth and modulation techniques. When an LTE deployment uses 20 MHz channel with 64 QAM (Quadrature amplitude modulation), the network can offer speeds of up to 300 Mbps in the downlink and 75 Mbps in the uplink. The downlink helps with the downloads and uplink helps with the uploads. LTE is much more efficient than the earlier 3G technologies, and it also reduces the latency in data transfer. With LTE Advanced and LTE Advanced Pro, the downlink speeds can move up to 1Gbps and 3Gbps respectively. These results represent the maximum achievable rates in ideal network conditions.

In real life, factors like the distance between the user and the base station, the number of users the base station is serving and obstacles like buildings etc. impact the achievable data rates. Just because your phone is showing a full 4G signal (signal bar) doesn’t guarantee super high 4G speeds. In busy hours, you may experience slower speeds even if you are getting a full signal. We can summarise the peak achievable speeds from the different variants of LTE below.

  • The regular LTE – up to 300 Mbps in the downlink
  • LTE Advanced – up to 1Gbps in the downlink
  • LTE Advanced pro – up to 3 Gbps in the downlink

In real-life where many people use the mobile network simultaneously from various locations and in different ways, what we eventually get are the average data speeds. Have a look at this post to find out what average speeds you can expect from LTE.

Just like its earlier 3G counterpart, 4G SIMs also exist in both voice/text & data as well as data-only formats. The former can be used in smartphones while the latter in mobile broadband dongles, tablets or any other mobile device. If you live in an area with decent 4G coverage, you can use LTE as an alternative to fixed broadband service.

What about 5G?

The need for higher data speed has been one of the key drivers for the evolution of mobile communications standards. While LTE may seem perfect for most of our use cases today, the fifth-generation networks (5G) will take things to a whole new level. 5G uses New Radio (NR) technology and can provide much higher speeds, much lower latency and also supports a large number of devices.

The full demand for 5G networks will evolve over time as we become more and more digital. The lower latency of 5G and the support for a large number of devices make it ideal for many market verticals e.g. manufacturing. For the general public, the most obvious benefit will be the super high data speeds they may get in locations with decent 5G coverage. 4G and 5G will co-exist for a very long time which means it will only make things better for the customers.

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