Optimising the quality of experience in 5G

Tommi Jämsä, senior manager of Channel Emulation Research and Technology at Anite, looks at some of the key challenges that need to be overcome to enable 5G, including increasing the radio channel bandwidth available to the wireless device and improving the spectral efficiency of the radio channel

Optimising the quality of experience in 5G

As the mobile industry plans next generation technologies, the pressure for wireless communications systems to do more, more quickly and more securely, increases.

5G is being talked about as a transformational technology, designed to address a wide range of services and wireless connectivity. The emphasis is on combining new technologies with existing ones, trillions of devices, huge data volumes and universal availability with a wide range of applications from mobiles to wearables, automotive to industrials and the Internet of Things.

Mobile networks and devices will become radically more complex and operators and device manufactures will need to fulfil challenging requirements in order to achieve expected performance levels and end-user Quality of Experience.

Optimising the Quality of Experience by focusing on capacity density
Quality of user experience is influenced by a number of factors, including data rates, latency, reliability, battery life, security and network coverage. The mobile industry has used 4G LTE technology to primarily maximise capacity, targeting peak data rates of 1 Gbps for nomadic (almost fixed) and 100 Mbps for mobile users (as specified by ITU-R¹).

5G will steer the focus more towards capacity density, and aims to enable 1,000 times the overall wireless capacity per square kilometre of what is currently available in LTE. This equates to significantly more wireless connections, potentially accessing data at rates of up to 10 Gbps.

In order to achieve above capacity density goals, the industry favours a number of approaches to improve the radio access network including; increasing the radio channel bandwidth available to the wireless device and improving the spectral efficiency of the radio channel.

Increasing the channel bandwidth at higher frequencies
Increasing channel bandwidth in the currently allocated and congested spectrum is challenging. Doing so in a contiguous block to achieve a 1,000 fold increase in capacity is impossible.

This is leading many researchers to look at centimetre and millimetre-wave frequencies (3 – 30 and 30 – 300 GHz) where spectrum is much more readily available on a global basis (essential to support international roaming and for 5G to benefit from the economies of scale of a unified technology across the globe).

The frequency bands discussed among key industry players include cellular bands below 6 GHz, as well as higher frequency bands such as 10 GHz, 28 GHz, 32 GHz, 43 GHz, 46 – 50 GHz, 56 – 76 GHz, and 81 – 86 GHz. However, these bands are only speculative right now. RF bandwidths are assumed to be around 100 MHz below 6 GHz, but may be up to a few GHz at millimetre bands.

Since current radio channel models are not adequate and radio wave propagation at such high frequencies is not well known, many industry players emphasise the importance of defining a channel model early in the development phase. Last spring, the Anite-led task group within the METIS² project published the world’s first channel models for 5G, an essential step in developing candidate 5G technologies.

Improving spectral efficiency using MIMO technology
One of the ways 5G technology is expected to improve spectral efficiency is to make use of Massive MIMO³. Massive MIMO will utilise tens – or even hundreds – of antenna elements within the base station and possibly dozens in the mobile device.

The much greater number of antenna elements used by Massive MIMO will make conventional conductive testing more difficult compared to 4G. Over-the-Air testing is therefore predicted to play an even larger role in device or infrastructure performance verification for 5G technologies.

Industry collaborations accelerating 5G development and testing
The complexity outlined above is likely to put more emphasis on testing as new mobile devices and infrastructure are developed for 5G technology. To accelerate 5G technology development and testing, key industry players are working towards addressing the above challenges and have formed a number of international organisations, research bodies and projects including EU Horizon 2020, 5G-PPP, METIS and Virtuoso.

Initiated by Intel, Project Virtuoso (Virtualised environment for communication system development and optimisation), was established to develop “virtualised” testing environments in order to accelerate 4G and 5G technology development and testing. The project benefits from Anite’s Virtual Drive Testing Modelling Tool, which uses Anite’s Propsim channel emulator to “virtually” recreate the field environment in the laboratory.

This enables quick, realistic and repeatable benchmarking of devices and base stations.
To conclude, quality of experience using 5G technologies will rely on improved capacity density, leading to increased complexity. This in turn will require advanced and virtual testing methodologies using established and market leading channel model expertise to ensure devices and infrastructure perform as expected.

Notes
1 ITU-R The International Telecommunication Union’s Radio communication Sector issues a global recommendation for radio communication. ITU-R ‘Requirements related to technical performance for IMT-Advanced radio interface(s)’, Report ITU-R M.2134 (2008), available online http://www.itu.int/.

² METIS (Mobile and wireless communications Enablers for Twenty-twenty (2020) Information Society) is an Integrated Project under the Seventh Framework Programme for research and development (FP7).

³ MIMO (Multiple Input Multiple Output) antenna configurations where both the base station and the device are equipped with multiple transmit/receive antennas.

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