The first publicly available LTE mobile network was launched in the Scandinavian cities of Stockholm and Oslo in 2009. That was over ten years ago, and a lot has happened since then in the ever-changing world of mobile communications. Today, the LTE technology has become synonymous with 4G and vice versa. We frequently see terminologies and symbols like 4G, 4G+, LTE, LTE+ popping up on our smartphones. Since its first launch in 2009, many enhancements have been added to the LTE technology. These enhancements are steps towards evolving the LTE technology to meet the 4G network requirements and reach a level that ensures its seamless co-existence with the new 5G networks. As a result, we have seen multiple terminologies over the last 10 years of LTE, including LTE-Advanced, LTE-Advanced Pro, LTE-A, LTE+, 4G+ and probably some other similar variants. In this post, we aim to look at the bigger picture first and then get into the details of LTE-Advanced and LTE-Advanced Pro to understand how these technologies differ from the original LTE network launched a decade ago. But first, let us clarify some of the terminologies to avoid any potential confusions.
Is 4G the same as LTE and LTE+?
4G is the fourth generation of mobile networks enabled by a technology called LTE – Long Term Evolution. Like any other technology, LTE went through an evolutionary period after its first launch and is still evolving. LTE-Advanced and LTE-Advanced Pro are versions of LTE that incorporate a range of enhancements to make the 4G technology more suitable for current and future use cases while also making the 5G migration easier. As far as the terminologies are concerned, the original LTE (2009) is shown on mobile phones as either LTE or 4G. The next LTE update, LTE-Advanced is represented on the mobile phones by the LTE+ or 4G+ symbols. The last but still evolving update, LTE-Advanced Pro, is a huge step forward but does not add a new symbol on the mobile phone and is still shown as LTE+ or 4G+ on the mobile phones.
What is the original LTE standard?
LTE and LTE-Advanced are 4G mobile network technologies where LTE-Advanced is a later version of the original LTE. Let us look at the original LTE standard first to appreciate the value the later technologies bring.
The first launch of LTE mobile networks took place in 2009 based on the requirements and specifications defined by 3GPP. 3GPP or 3rd Generation Partnership Project is a partnership of various standards organisations. These organisations work together under the 3GPP umbrella to define and improve UMTS, LTE, LTE-Advanced and other inter-related technology standards. You can learn more about 3GPP by clicking on this link that will take you to their website. The way it works is that different releases from 3GPP come periodically with specifications on existing and new cellular technologies and enhancements. The specifications for the original LTE were defined in 3GPP release 8. The work continued in the following release, release 9, to lay a solid foundation for the LTE networks.
The original LTE technology has the ability to operate in both FDD – Frequency Division Duplex and TDD – Time Division Duplex techniques. This is a significant step as it allows key 3G technology standards including UMTS, CDMA2000, and TD-SCDMA, to take the LTE route for 4G migration. Therefore, LTE is a key step towards the convergence of mobile network technologies because it enables all key 3G technologies to use a single technology for 4G upgrade. You can read more about the duplexing schemes for 4G LTE and 5G NR in this post.
One key requirement for the original LTE standard was to offer flexibility in how the frequency spectrum can be used. LTE can operate in a range of carrier bandwidths going all the way up to 20 MHz. LTE uses different access technologies for the downlink and uplink, which is different from how the 3G technologies work. LTE employs Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink.
What is the difference between LTE and LTE-Advanced?
The initial launch of LTE was followed by LTE-Advanced, which was specified by 3GPP in release 10. LTE-Advanced introduced many improvements into the existing LTE networks, and capacity was identified as one of the key areas. The features included higher data rates, more efficient use of the frequency spectrum, improvements to the antenna technologies, the capacity to serve more users simultaneously, and enhanced network coverage solutions. Have a look at release 10 at 3GPP’s website for the exact information.
LTE-Advanced was required to offer peak data rates of 3 Gbps in the downlink and 1.5 Gbps in the uplink. In case you are wondering, these are peak data speeds and the average speeds are generally considerably lower. Please check out an earlier post from us on the average LTE speeds by clicking here. LTE-Advanced is backwards compatible which basically means that any earlier LTE devices that existed before LTE-Advanced launch, would still be able to access the LTE-Advanced network so a customer would not need to buy a new device just to be able to access the LTE-Advanced frequencies. However, the post-LTE-Advanced devices may be able to access a wider range of LTE-Advanced features as opposed to the earlier devices.
One key feature within LTE-Advanced was carrier aggregation which allowed mobile operators to use the frequency spectrum more efficiently. With carrier aggregation, multiple frequency channels can be combined to achieve much higher bandwidth, resulting in much higher data rates for the end-users. Carrier aggregation is further supported by improvements to the underlying antenna technologies to make the overall spectrum usage even more efficient. This is accomplished through improvements to spatial multiplexing (MIMO-Multiple Input Multiple Output) to transmit a higher number of multiple data streams to increase the overall data rate. In LTE-Advanced, the number of transmission layers increased to 8 for downlink and 4 for uplink.
The concept of heterogeneous networks or HetNet is not new, and LTE-Advanced includes capabilities that make it easier to plan and deploy HetNets. As a result, a range of different kinds of cell sites such as the main cell site (macrocell), microcells, picocells can work together to create the required network coverage and capacity. The key addition here is the use of relaying technologies in the form of relay nodes. Relay nodes can lead to improvements in both coverage and capacity of a cellular network. They work similarly to small cells and repeaters, but there are advantages of using relay nodes. From a coverage viewpoint, relay nodes are better than repeaters because repeaters amplify everything in the signal, i.e. the actual information content plus noise. Relay nodes are small base stations, not that different from small cells, but they have the ability to utilise the existing mobile base station for backhaul purposes. Instead of using dedicated fibre or other solutions, relay nodes can work with macrocells (eNodeB) to serve end-users. It does not change anything on the device side because the user devices see the relay nodes as normal cell sites.
What is LTE-Advanced Pro?
LTE-Advanced Pro can be considered somewhere between 4G and 5G, which is why it is often referred to as 4.5G. The LTE technology is expected to evolve beyond LTE-Advanced and LTE-Advanced Pro and co-exist with 5G to create an ecosystem that can cater to a wide variety of basic and advanced use cases. Therefore, LTE-Advanced Pro is fully aligned with the 5G technology and will continue to evolve in parallel with 5G.
LTE-Advanced Pro was introduced in 3GPP release 13 at some point in 2015. LTE-Advanced Pro offers a range of new features as well as enhancements to the existing LTE-Advanced features. Carrier aggregation, which was already supported in LTE-Advanced went through some improvements to take the maximum carrier bandwidth to a whole new level. Unlike LTE-Advanced which could aggregate 5 carriers, LTE-Advanced Pro has the ability to aggregate up to 32 carriers and enable a maximum bandwidth of 640 MHz. This bandwidth can take the peak data rates to up to 25 Gbps in the downlink. The carrier aggregation enhancements in LTE-Advanced Pro are coupled with improved support for multi-antenna transmission.
A key feature that piggybacks on carrier aggregation improvement is License Assisted Access or LAA. You can read more specific information on this solution on Ericsson’s page here. Basically, this feature allows the LTE networks to use a combination of licensed and unlicensed frequency bands to boost data rates considerably for the end-users. As explained in one of our posts here, the frequency spectrum is one of the most fundamental resources of a mobile operator with regulatory and financial considerations. The prospect of using unlicensed spectrum can be seen as an attractive opportunity. This is where carrier aggregation helps, as it allows a mobile operator to aggregate a licensed frequency band with an unlicensed band (generally 5 GHz) to achieve higher dates without using additional licensed spectrum. However, the License-Assisted Access feature does not allow LTE-Advanced Pro networks to use the unlicensed frequency band on its own. The unlicensed band must be used together with the assistance of a licensed frequency band which still acts as the primary carrier. The licensed carrier addresses all the critical tasks, including signalling and is complemented by the unlicensed band for additional bandwidth and data rates. The unlicensed frequency band, usually 5GHz, is used for less demanding services where “best-effort” is the way to go. For services where assurance of service quality is critical, the licensed spectrum is used.
Other key features of LTE-Advanced Pro include the introduction of Narrowband IoT (NB-IoT) in release 13, improvements in broadcasting capability, enhancements in Device-to-Device (D2D), and addition of Vehicle-to-Vehicle (V2V) and Vehicle-to-Everything (V2X) services in release 14.
Finally to answer the original question in few words…
LTE stands for Long Term Evolution, and it is a technology that enables 4G mobile networks. LTE-Advanced and LTE-Advanced Pro are enhanced versions of LTE that aim to evolve the LTE technology so it can reach its full potential as a 4G technology while also building capabilities that make the co-existence of 4G LTE and 5G NR networks easier. 4G+ and LTE+ are just symbols that represent LTE-Advanced and LTE-Advanced Pro. The original LTE is shown on mobile phones as either LTE or 4G.