Long Term Evolution (LTE) is a form of 4G technology that supports mobile data traffic. It offers a significant increase in data transfer rates compared to prior mobile data generations (GPRS, EDGE, and 3G). Theoretically, the maximum download speed offered by LTE is in excess of 300 Mbps; upload speeds max at 75 Mbps. However, these speeds may vary across regions and with different service providers. LTE supposedly competes with Worldwide Interoperability for Microwave Access (WiMAX), which is another 4G technology. LTE-compatible mobile devices became available after 2010. Similar to other Global System for Mobile communication (GSM) technologies like 2G and 3G, LTE is backwards compatible – meaning an LTE-capable device can also work on 3G or 2G SIM cards.
LTE Advanced (LTE-A) is an enhanced version of LTE that offers three times much faster speeds than standard LTE and also adds fresh wireless transmission abilities. Theoretical maximum speed on LTE-A is 1 Gbps; real-world download speeds being 100 Mbps or more. LTE is not designed to handle text messages, voice calls, network alerts, etc. LTE specifications were put in place as only a data network. To make voice calls on an LTE SIM, operators have to revert to 2G or 3G systems. Voice over LTE (VoLTE) is a service based on LTE that provides voice services, or the ability to make calls over LTE.
History and Adoption
LTE was developed by 3rd Generation Partnership Project (3GPP) in 2004 as a project. In March 2008, the International Telecommunication Union Radiocommunication Sector (ITU-R) devised a set of mobile data technology that would be much faster than 3G, and called 4G. However, LTE is not technically 4G because it does not meet the original 4G standards set by ITU-R, which was almost impossible to achieve at that time. The global telecommunication sector relaxed its 4G specifications thereafter so that any wireless technology that was a significant improvement over 3G could be considered 4G. This resulted in LTE, along with WiMAX and HSPA+, being referred to as 4G technologies.
Sweden and Norway are the countries who first got LTE in 2009. LTE first came to America in 2010 courtesy MetroPCS (a mobile network provider). The UK received its first 4G LTE connection in October 2012, thanks to a T-Mobile and Orange joint venture, which was called Everything Everywhere (EE). Bharti Airtel was the first to launch LTE in India. Japan got its first LTE service in 2010 courtesy NTT DoCoMo.
LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) – a popular multi-user variant of Orthogonal Frequency Division Multiplexing (OFDM). OFDM is used for downlink (transferring information from tower to device) purposes, which entails usage of Multiple Input Multiple Output (MIMO). MIMO enables several connections to a particular device, resulting in increased connection stability and decreased latency (the time taken for a data packet to move from its origin to destination).
For uplinks (moving data from device to tower), LTE uses a Single Carrier Frequency Division Multiple Access (SC-FDMA) that does not have multiple connection routes. This is because, unlike a tower, an LTE mobile device doesn’t have a powerful signal heading back to the cell tower. In case such signals were present, mobile phones would have had disastrous battery endurance numbers. SC-FDMA is also a MIMO setup.
LTE-TDD and LTE-FDD
Also, LTE uses Frequency Division Duplex (FDD). FDD is a form of full-duplex communication. It uses two unique radio frequencies for uplink and downlink. A good level of guard band is used to separate the bands so that the receiver and transmitter do not interfere with each other. FDD is used widely in cellular technology systems – for instance, the GSM system.
Time Division Duplex (TDD) is another full-duplex communication format. It uses only one frequency, which alternates between downloading and uploading information. The space allotted for downloading and uploading is not equal, and the ratio could be altered if more data has to be sent or received, or vice-versa.
Despite these variations, LTE-FDD and LTE-TDD are almost identical at their cores – 90 percent to be precise. This means mobile device chipsets and networks could use both LTE versions. LTE-TDD is a less common option and seen as an alternative to LTE-FDD. LTE-FDD is quite widespread in the West, whereas LTE-TDD is more common in Asian countries such as China.
LTE works on different bands and frequencies across regions, which means the LTE experience may vary across countries. Both FDD LTE and TDD LTE bands have their own frequencies. Band 1 to Band 30 are FDD LTE bands. Band 33 to Band 44 are TDD LTE bands. Japan, South Korea and Philippines are on Band 1 (2110 – 2170 MHz). Band 3 (1805 – 1880 MHz) caters to Australia, South Korea, United Kingdom, Singapore, etc. Other bands such as Band 8 (925 – 960 MHz), Band 7 (2620 – 2690 MHz) and Band 17 (734 – 746 MHz) also have their own coverage areas. Band 3 (1800 MHz) and Band 7 (2600 MHz) are the most popular bands.
There are different FDD LTE frequencies for uplinks and downlinks. TDD LTE bands don’t have the same frequency for both downlink and uplink. The aforementioned numbers denote FDD LTE downlink frequencies. More frequency bands can be added in the future based on the increasing demand for mobile communications.
Why are these bands essential? If operators used the same LTE bands, there will be connection interferences between them. More megahertz (MHz) means improved connection, and a more robust and widespread network. These bands determine data capacity, which means more people can access 4G data on larger bands (such as 2600 MHz) simultaneously and a lesser number of people on narrower bands (such as 800 MHz). However, lower frequency bands are much more capable of penetrating walls when compared to bigger frequency bands – which means the signal is better indoors on smaller bands. Some operators may start with smaller frequencies and increase the size after more users move from prior networks to LTE.
Asian countries usually have smaller bands compared to Western countries since most of their houses are made from concrete, meaning bigger bands will have a hard time making it inside the houses through such walls. There is comparatively more glass used in the houses in the West.