Social media, video streaming, online gaming, you name it, our smartphones are better connected than ever and we’re consuming more and more data as a result. 4G LTE is the current generation of wireless technology making all of this a reality, although carriers are quickly transitioning to 5G in many countries. 4G does all this at much faster speeds than the older 3G and 2G standards. But what is LTE, exactly?
In this article, we’ll be taking a look at how LTE works, the hardware associated with it, its benefits, and how this all relates to the smartphone in your pocket.
What is LTE and how does it work?
The most notable differences between LTE and its predecessors are the changes in frequency and bandwidth usage. With 3G, the 2100MHz band was the main global frequency, with a 900MHz option for longer range coverage. There are many more 4G LTE bands, the use of which will vary depending on your country and even your specific carrier. Popular spectrum includes the 800, 1800, and 2600 MHz bands, with 700, 1900, and 2300 used by a few carriers also.
With 4G LTE, these frequencies are split into Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD). FDD spectrum requires pair bands, one for uplink and one for downlink. TDD uses a single band as uplink and downlink on the same frequency, but these are time-separated instead. There are 31 pairs of LTE bands that operate between 452 MHz and 3,600 MHz and an additional 12 TDD bands between 703 MHz and 3,800 MHz. Higher frequencies allow for faster transmission in built-up areas, while lower frequencies offer additional coverage distance but more limited bandwidth. These bands typically offer between 10 and 20 MHz of bandwidth for data transfer, although they are also commonly split up into smaller 1.4, 3, and 5 MHz chunks too.
FDD is the LTE variation that is regularly seen in North American, European, and some Asian markets. TDD has been implemented in China and India as the wider bandwidth allows for more users per Mhz. This is why you should always be careful to double-check LTE bands and carrier compatibility when importing phones from other countries.
LTE uses two different radio links for downlink and uplink — from tower to device and vice versa. For the downlink, LTE uses an OFDMA (orthogonal frequency division multiple access), which requires MIMO. MIMO, which stands for Multiple Input Multiple Output, uses two or more antennas to reduce latency significantly and boost speeds within a given channel. Standard LTE can accommodate up to a 4×4 arrangement (the first digit is the number of transmit antennas, and the second, the number of receive antennas). For the uplink (from device to tower), LTE uses an SC-FDMA (single carrier frequency division multiple access) signal. SC-FDMA is better for uplink because it has a better peak-to-average power ratio.
There’s a lot to the underlying technology. But in a nutshell, 4G LTE enables more spectrum bands to provide more bandwidth than 3G. This results in higher data speeds and better quality connections than previous generations.
What is LTE Advanced and how does it work?
Standard 4G LTE is outdated now. Modern 4G networks are based on LTE-Advanced technology. As the name implies, LTE-Advanced is simply an evolved version of current LTE connectivity, using a variety of additional techniques to warrant the “advanced” name. The new functionalities introduced in LTE-Advanced are Carrier Aggregation (CA), better use of existing multi-antenna techniques (MIMO), and support for Relay Nodes. All of these are designed to increase the stability, bandwidth, and speed of LTE networks and connections.
We’ve also seen the arrival of LTE-Advanced Pro — also known as Gigabit LTE in some markets — (3GPP Release 13 and up). So how does this differ from standard LTE-A?
The key to faster data via LTE-Advanced is the introduction of 8×8 MIMO in the downlink and 4×4 in the uplink, allowing for multiple carrier bands to be aggregated together to improve signal strength and bandwidth. Carrier aggregation sends and receives data over multiple bands, increasing the amount of throughput for faster speeds. Each LTE band has a bandwidth of either 1.4, 3, 5, 10, 15, or 20 MHz, giving us a maximum bandwidth of 100 MHz with five combined. Although this will vary depending on the bandwidth available in your particular area.
LTE-Advanced Pro/Gigabit LTE touts carrier aggregation with up to 32 component carriers. Theoretically, these provide a maximum download speed of approximately 3.3 Gbps and 1.5 Gbps upload. However, the hardware modem found inside your smartphone probably isn’t quite that fast and network coverage certainly isn’t good enough to meet that criteria yet.
Another important part of the LTE-Advanced puzzle is quadrature amplitude modulation (QAM). This technique essentially crams more bits of information into the signal sent from a tower to your phone. Higher QAM delivers more information in a signal and thus faster speeds. We’ve previously seen 64QAM being used in LTE-A, but LTE-Advanced networks from the likes of Verizon, T-Mobile and others use 256QAM too. This particular version of QAM dramatically boosts bandwidth and, much like massive MIMO, is another foundational technology used in 5G. In fact, Qualcomm says 256QAM boosts download speeds by 33 percent over 64QAM.
How fast is LTE?
Now that we’ve outlined what LTE is, how fast is it?
The major benefit for consumers with 4G is faster download speeds. However, the quality and speed for your connection will clearly vary based on the number of users and the strength of the signal. Most LTE networks provide between 10 and 20 Mbps download speeds, according to the latest OpenSignal research. The fastest 4G LTE countries boast up to 50 Mbps download speeds on average, although that’s still a rarity for most consumers.
For comparison, older 3G networks can vary quite widely in their actual results. HSPA networks can peak at around 14 Mbps download and 6 Mbps upload, but they rarely come close to this. Typically, a good LTE network is at least 5 to 10 times faster than the best 3G coverage.
The tech inside your phone
“What is LTE?” is just part of the puzzle. There’s more to this technology. As you have probably figured out, 4G has been an evolving standard and it continues to change as we move towards a future with 5G technology. As such, the hardware inside our smartphones has changed over the years to keep pace with faster LTE networks.
To keep things relatively simple, user equipment is split into a number of different categories, each designed to offer a set of features and speeds based on a specification release. This is often the number that you’ll see listed on a smartphone specification sheet. Release 10 introduced the speed and MIMO improvements that come with LTE-Advanced, but there are newer Release up to Category 16 for 5G on the way too. Here’s a comparison of how some of them break down.
|Max Download||Max Upload||MIMO Config.||Release #|
|Category 6||300Mbps||51Mbps||2 or 4||10|
|Category 9||450Mbps||51Mbps||2 or 4||11|
|Cateogy 10||450Mbps||102Mbps||2 or 4||12|
|Cateogy 12||600Mbps||102Mbps||2 or 4||12|
Mobile SoC manufacturers bundle 4G modems with their processing components into the main chip, as it is such an essential technology. For example, Qualcomm’s Snapdragon 855 features the company’s own X24 LTE Category 20 modem. However, the latest Snapdragon 865 doesn’t feature an integrated 4G LTE modem, as the company is transitioning over to 5G using an external modem.
The road to 5G
The roll-out of fast 4G networks isn’t over yet. There are still many more customers to bring online and infrastructure to improve across the globe. Even legacy technologies are set to stick around for a good while yet. 4G adoption is set to hit almost nine billion devices in 2020, even though the industry is quickly moving towards 5G connectivity.
5G is really another evolutionary step that started with 4G. Just like LTE-Advanced, 5G technology further increases the range of available bands, aggregating data from an even wider range of spectrum frequencies. These include sub-6GHz and very high mmWave frequencies. Just like LTE and LTE-A, 5G requires new radio technologies from carriers and new hardware inside our smartphones. These technologies are set to become mainstream throughout 2020.