What are Pre5G and 4.5G? Migrating towards 5G networks

12 June 2017

Pre5G and 4G.G

Hoping to plug the gap between 4G and 5G, Pre5G and 4.5G are attempts by network vendors to push LTE A-Pro technology and realise 5G-like performance on 4G networks.

Why do we need Pre5G and 4.5G?

To break the gigabit-per-second speed barrier in advance of 5G's arrival. The first components of super-fast 5G mobile networks will likely not be installed until at least 2020. Then will begin a slow process of network upgrades that could take many years.

So is the global telecoms industry in stasis until 5G's arrival? Absolutely not. There’s now a race on to develop 5G pre-commercial prototypes, with the goal of achieving something approaching 5G speeds by pushing 4G networks to their absolute limit.

Both Pre5G and 4.5G are marketing speak for next generation network technology between 4G and 5G. They're a promise of 'tomorrow’s tech today', an attempt on the part of network vendors to convince operators to upgrade their existing 4G infrastructure ahead of 5G's introduction.

The phrase Pre5G was coined by ZTE in 2014, and the Chinese company and its partners presently use it to describe how technology created for 5G networks can be used to maximise 4G networks. Although it’s essentially involved in the same activities, ZTE’s major rival in China, Huawei, doesn’t use the term Pre5G. Instead, the Shenzhen-based company calls its 4.5G, a term it first used it in 2014 ahead of the standardisation by 3GPP of LTE-Advanced Pro.

That's key, because what Pre5G and 4.5G have in common is that they both describe the same stop-gap between what we have now, and what 5G will bring. That essentially translates as LTE-Advanced and LTE-Advanced Pro, with the latest technology added.

What are LTE-Advanced and LTE-Advanced Pro?

Since LTE-Advanced (LTE-A) is essentially 4G, LTE-Advanced Pro (LTE-A Pro) aims to significantly increase the data speeds and bandwidth available for mobile communications. Sometimes called Gigabit LTE, it's a stepping stone towards 5G – and that's exactly what Pre5G and 4.5G are. The key attributes that will define LTE-Advanced Pro are:

  • Data speeds in excess of 3Gbps (LTE-A: 1Gbps)
  • 640MHz of carrier bandwidth (LTE-A: 100MHz)
  • Latency: 2ms (LTE-A: 10ms)

What are the goals of Pre5G?

Designed to become available much earlier than 5G, though in many ways offering a similarly fast and reliable user experience to 5G, Pre5G networks will, says ZTE, offer both high bandwidth and low latency. The IMT-2020 (5G) promotion group, an organisation created by China to oversee 5G development, wants Pre5G to mean:

  • Peak downlink speeds of 100Mbps-1Gbps & increase average user bandwidth by five times
  • Increase system capacity by up to eight times
  • Connect 100 times more connections per unit area compared with 4G

What are the goals of 4.5G?

Aiming for higher peak downlink speeds, Huawei says that 4.5G networks will offer:

  • Peak downlink speeds of around 6 Gbps
  • Latency rates of around 10 milliseconds
  • The ability to support 100,000 connections within a square kilometre

What are the user benefits of Pre5G and 4.5G?

Immersive virtual reality (VR) and augmented reality (AR), 4K HDR video streaming, and cloud-based storage are all demanding faster mobile broadband now, and can’t wait for fully fledged 5G networks. Pre5G and 4.5G are attempts to improve the efficiency of the network spectrum, without increasing bandwidth,, to allow the development of mobile broadband services.

How do Pre5G and 4.5G differ from LTE-Advanced Pro?

LTE Advanced Pro promises gigabit peak data rates, faster throughput, lower latency, more capacity and better uniformity. However, despite being approved by the 3GPP in October 2015, LTE-Advanced Pro barely exists, and no mobile networks yet offer gigabit speeds, let alone 3Gbps. Besides, no smartphones could take advantage.

The network vendors behind the terms Pre5G and 4.5G are trying to convince operators to introduce LTE-Advanced Pro technologies such as Carrier Aggregation (CA), 4x4 MIMO, Wi-Fi link aggregation (LWA) and narrowband Internet of things (NB-IoT), but also to incrementally introduce new non-LTE-Advanced Pro technology specifically meant for 5G networks.

What 5G technologies are part of Pre5G and 4.5G?

Network vendors are currently experimenting with various antenna arrays, frequency bands and other technologies to make existing spectrum capable of offering 5G-like connectivity. Such technologies are numerous, but include:

  • Massive MIMO: a key 5G technology to improve spectrum efficiency, massive MIMO (multiple-input and multiple-output) uses large-scale antenna array to support both horizontal and vertical 3D beam-forming.
  • 4x4MIMO: a MIMO system with four input antennas and four output antennas that achieves higher transmission rates and reliability.
  • CA (carrier aggregation): expands network capacity by combining various channels, unifying fragmented spectrum to boost peak user data rates and overall network capacity. 5G could see the convergence of multiple wireless technologies.
  • LTE-Unlicensed & LAA (License Assisted Access): the use by telecoms operators of the unlicensed spectrum currently used for WiFi
  • 256QAM (quadrature amplitude modulation): this high-order modulation technique sees amplitude, frequency and phase of the radio waves modulated to carry more bits, increasing the uplink data speed.
  • CloudRAN: virtualises network functions and moves resources to the cloud, flexibly supporting 4G, 4.5G, 5G and Wi-Fi. It also enables network slicing.

Does Pre5G exist yet?

Only as sporadic experiments. Pre5G will use some candidate technologies for 5G. For example, in July 2017, ZTE, China Mobile (the world's largest telecoms carrier) and Qualcomm demonstrated a so-called Pre5G technology by achieving a peak network rate of 1Gbps on a TD-LTE commercial network in Quanzhou, Fujian, China. The technologies used included multi-carrier aggregation, 4x4 MIMO and 256QAM.

The gigabit era is coming. Whether you call it Pre5G or 4.5G, this shorthand for describing technology beyond 3G, but not quite 4G, is primarily about achieving ultra-fast mobile broadband speeds as quickly as possible. It boils down to two key presumptions by the telecoms industry; the amount of data traffic carried over mobile networks will continue to grow, and the average consumer will not care whether his or her phone's 1Gbps download rate is being achieved via 4G or 5G networks.

It's important to stress that terms Pre5G and 4.5G are primarily used as part of a marketing drive on the part of mobile network vendors ZTE and Huawei, and their technology partners, to promote LET-Advanced Pro. Whatever is understood by them, Pre5G and 4.5G should result in the most advanced 4G networks possible in advance of 5G's introduction, and herald the start of both gigabit speeds and ultra-low latency. However, for the peak data rates to 10Gbps and latency of under one millisecond promised by full-fledged 5G networks, consumers will have to wait until well into the 2020s. 

Useful reading: What Is 5G?

Jamie Carter
About Jamie Carter

Technical Writer at 5G.co.uk

Jamie has been writing journalism, books and white papers about science & nature for 20 years.

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