What is 5G? All the details of the new super-fast mobile internet technology explained

There's a lot of buzz in the tech world about 5G, a next generation wireless networking technology that promises superfast mobile internet speeds capable of delivering high bandwidth content on the go. Envision streaming virtual reality experiences, video and music to hundreds of mobile users without the network breaking a sweat.

However, it's important to note that 5G doesn't exist – yet. The specifications of the technology are being set out by global mobile standards body 3GPP. Meanwhile, mobile network operators are focused on trying to get as much as they can out of their existing 4G networks.

To help you navigate this exciting, but rather complicated concept, here's an explanation of what exactly 5G is, and some of the technical terms you will hear mentioned frequently from now on, such as in this 5G news round-up from Mobile World Congress 2017, which contains announcements from the likes of Intel, Qualcomm, Ericsson, Nokia and BT.

What is 5G?

5G will be the next generation of mobile network technology, enabling multi-gigabit per second (Gbps) internet speeds. In comparison, standard 4G LTE mobile networks provide average download speeds of up to 15Mbps in the UK, while the fastest 4G+ services offer an average download speed of 90Mbps (speeds provided by EE).

For 5G signal transmission, the plan is to occupy part of the currently unused 28GHz and 39GHz bands, and refarm sub-6GHz frequency bands which are currently used for radio, TV and 4G transmission.

What are millimetre waves?

Millimetre waves fall in the extremely high frequency (EHF) class, also known as terahertz radiation, which ranges from 30GHz to 300GHz. These frequencies are found in the electromagnetic spectrum between microwaves and infrared waves, and have wavelengths measured between 1-10mm.

Millimetre wave offers more bandwidth than the sub-6GHz frequencies currently in use for 4G networks, but its use is hindered by a signal that only carries a few kilometres from the transmitter due to high free space loss and atmospheric absorption.

With sub-6GHz frequencies being heavily crowded by existing communications technology, researchers are looking toward the vacant millimetre wave spectrum to expand their wireless networks. Research has shown that a network using millimetre wave will be possible, even though there are still many technical challenges that need to be solved.

What is 5G NR?

5G New Radio (5G NR) is the new specification that is being devised by the 3GPP. The global mobile operator body GSMA is determined to see mobile operators deploy 5G wireless networks by 2020, but the industry is now aiming to make this possible by 2019.

At MWC 2017 in Barcelona in February, a large number of key players in the global mobile industry, from smartphone manufacturers to telecommunications technology firms and mobile operators, agreed to collectively support and back the 5G NR specification, which is a huge step in the right direction.

The firms that have agreed to support 5G NR include: AT&T, NTT DoCoMo, SK Telecom, Vodafone, Ericsson, Qualcomm, British Telecom, Telstra, Korea Telecom, Intel, LG Uplus, KDDI, LG Electronics, Telia Company, Swisscom, TIM, Etisalat Group, Huawei, Sprint, Vivo, ZTE and Deutsche Telekom.

To deliver true 5G (known as 'Standalone 5G NR'), extensive infrastructure upgrades will have to be rolled out, such as new mobile base stations and transmitters. The consumer market will also be waiting for mobile phone manufacturers to produce 5G capable phones.

It is unlikely that all this will be in place for a sudden switchover in 2019; instead the industry is going to gradually implement the new technology in stages. 'Non-Standalone 5G NR' will be the focus, making use of the existing 4G LTE radio and evolved packet core network and then adding a new 5G radio access carrier.

What is MU-MIMO?

Multi-user, Multiple Input, Multiple Output (MU-MIMO) is a Wi-Fi technology introduced in 2015 that enables routers to connect and transmit data from multiple devices simultaneously using beamforming.

MU-MIMO works by transmitting radio signals in different directions at particular angles in order to better detect where the devices connecting to the internet are located in a room. The antenna makes small changes every now and then to strengthen radio signals going in some directions, while signals going in other directions are cancelled out.

This Wi-Fi technology can also be applied to mobile networks. Current mobile base stations send singals out in a wide beam, but really the operator is only trying to connect to where a user and their device is located. All the rest of the signal waves being sent out that don't connect to a device are wasted.

Mobile operators want to use MU-MIMO for millimetre wave transmissions because a direct line-of-sight connection (point A to point B) is needed to transmit data at high speed. Unfortunately people and their devices are unlikely to always be situated in an unobstructed path to the nearest mobile base station.

Beamforming means that the user's device communicates with the mobile base station to let it know where its exact location is. Then, the mobile base station can immediately modify its phase and power to provide a better signal.

Existing mobile networks connect with millions of users every second, but each connection is an individual conversation that the network is having with each user's smartphone. With MU-MIMO, the network can connect to multiple devices at the same time and use less bandwidth, instead of a blanket broadcast of signals over a specific geographic area, which means that there is more bandwidth available that isn't being wasted.

What is OFDM?

OFDM stands for Orthogonal Frequency-Division Multiplexing, which is a form of digital signal modulation in which a single data stream is split across multiple separate narrowband channels at different frequencies to avoid mixing up transmissions from multiple users.

Imagine that the signal from the mobile network to the mobile base station and your smartphone is one big highway. Each text message you send to a contact is like a car on that highway, and the message your friend sends in return is another car.

The mobile operator needs to make sure not to mix up all the messages being sent over the network, so it puts a guard between each message. It might take 2 seconds for each message to be sent and received by the network, including the time to put the guard down.

With OFDM, instead of one car being sent down the highway, the message is split into four cars (four separate streams) that travel down the highway at the same speed. As there are four cars, not one, each car is lighter and travels faster, and there is narrower guard between each of the four parts, so the total time taken to send the message is shorter than sending it the old way.

Also, splitting the message into four parts reduces interference and disturbance caused by electromagnetic fields from one signal affecting another signal in an adjacent circuit (known as crosstalk).

What is adaptive self-contained TDD?

TDD stands for Time Division Duplex, a single frequency band used to both transmit and receive data. The technology works by having the mobile network assign alternating time slots for transmitting and receiving data, whether it's voice, a text message or video. The data is transmitted in serial binary format.

This technology works well to save spectrum space as it only needs one channel of frequency, but it requires precise timing and synchronisation to make sure that the timeslots don't overlap and corrupt the data flowing between the mobile network and the user's device.

Imagine that each timeslot is like a single frame on the network, and each frame contains the message (being uploaded or downloaded to the internet), as well as details about the time it has been allocated.

In the 5G future, the mobile industry wants to improve TDD so that each frame contains even more information, such as the upload or download scheduling information, the data being transmitted and the acknowledgement.

This enables mobile operators to have intricate control over how and when each message is sent over the network. So for example, in the event of a natural disaster, if the police and first responders urgently need the network to communicate to save lives, the mobile operator will change the timeslots so that the police and firemen get the most bandwidth.

In this case, the regular user who is streaming a YouTube video or FaceTime-ing their friend, will experience slower mobile internet as their timeslots for uploading and downloading data will be moved to the back of the queue.

What is 5G TF?

Verizon says that it has built a 5G network and that it is piloting 5G pre-commercial services in 11 cities (Washington DC, Miami, Seattle, Sacramento, Houston, Denver, Dallas, Brockton (MA), Bernardsville (NJ), Atlanta and Ann Arbor) starting from Spring 2017.

Verizon is not supporting the 3GPP's proposed 5G NR specifications. Instead, it is working with a large number of partners including Ericsson, Nokia, Samsung and Qualcomm in the Verizon 5G Technology Forum (5G TF) and using technical specifications developed from this to extend Verizon's 28/39 GHz frequency bands.

Since 5G doesn't exist yet and there are still many challenges to be resolved for millimetre wave, and the fact that Nokia is working closely with Verizon, we wouldn't be surprised if the mobile operator is using Nokia's 4.5G and 4.9G technologies to expand the capabilities of its existing 4G LTE network to provide higher mobile internet speeds.