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Enabling rapid 5G roll-out

With the rollout of 5G expected to ramp up in the coming year, a complete spectrum of test & measurement solutions will be required, according to Meik Kottkamp.

As the rollout of 5G starts to ramp up in 2019, we will move a step closer to enjoying the much-anticipated benefits this new technology will bring. Higher data rates will radically improve the experience of using mobile networks for both business and leisure activities and reduced latency will enable new applications, which require a deterministic real-time response, such as autonomous driving, remote surgery for eHealth, virtual reality and cloud robotics for Industry 4.0.

Finally, increased capacity will also significantly reduce or eliminate congestion issues and facilitate M2M communications at a scale which will take system interconnectivity to a new level.

The three main focuses of 5G enhancements, namely enhanced mobile broadband (eMBB), massive machine type communications (mMTC) and ultra-reliable low latency communication (URLLC) all come with their own technology challenges, however, including the spectrum shift to higher frequencies and the need for advanced antenna arrays to enable beamforming and Massive MIMO.

The advent of 5G will result in a far more complex technology that will require the techniques that have previously been developed and used to test preceding generations to be optimised and rethought.

Leading engineering companies will have to develop new test methods that ensure that the commercialisation of 5G products and solutions are viable across different industries and applications.

Network and end-user equipment developers have already been making steady progress in addressing these challenges over the last few years but critical to the successful rollout is the development of test and measurement equipment that enables developers to evaluate the performance and standards compliance of this new equipment in the lab, in production and in the field.

To get 5G equipment to market quickly, efficiently and economically requires T&M vendors to work closely with both the top tier equipment makers and the standards authorities to resolve their own set of technical challenges and provide a complete spectrum of T&M solutions that are both fit for purpose and have a low cost of ownership.

The solutions to these challenges are both evolutionary and revolutionary. Since both 4G and 5G are based on OFDM, existing equipment designed for 4G can often be upgraded, in some cases just with software, to make it suitable for 5G.

This will certainly be the case with signal generators and spectrum and signal analyzers from leading, established T&M equipment vendors, like Rohde & Schwarz, that look to design in this future-proofing in order to reduce not only development costs for themselves, but notably also the total cost of ownership of their products for their customers.

In other cases, hardware evolution will be required. This is the case for example with vector network Analysers, which are now required to have true multiport test capabilities to support Massive MIMO. A top of the range 5G analyser can now boast support for up to 24 ports in real time, which can be increased to 288 ports using a switch matrix. This is important as Massive MIMO antenna arrays typically have 128 antenna elements or more.

Simultaneous testing of LTE and 5G terminal devices, necessary for the network architecture favoured by the majority of network operators, also requires hardware enhancements, in part because OTA measurement solutions need additional shielded chambers.

Where evolution of existing T&M equipment or designs is not feasible however, technological revolution is required. A clear example in this category is a consequence of the introduction of new frequency bands. The implementation of components, chipsets, modules, wireless devices and base stations in the 28 GHz or 39 GHz band requires much higher integration density and the use of active antenna systems in order to enable efficient beamforming.

The need for low path loss and small size lead to highly integrated PCBs that include antennas, amplifiers and analogue phase shifters.

As a result, RF connectors are no longer available and the cabled methods currently used to validate the performance of 5G technology will no longer be able to be used. All of which means that over-the-air (OTA) test solutions will have to be rolled out to replace existing conducted measurement methods.

However, OTA testing at sub-6 GHz frequencies is very difficult as far-field analysis would require very large chambers measuring 10m or more. One innovative solution to this problem is to make near-field measurements under far field conditions.

At cm-/mmWave frequencies compact antenna test range (CATR) solutions apply, which create far field conditions in close vicinity to the DUT (See opposite).

CATR realises the NF-FF transformation with a well-designed and highly accurate produced mirror. The reflector weight significantly increases below 6 GHz operation, since massive MIMO antennas easily reach radiating dimensions greater than 70 cm or 80 cm. The cost, fabrication time and handling of large heavy mirrors becomes prohibitive.

Using an antenna array, it is possible to create a planar field that allows for a quiet zone of 1 metre in diameter within a measurement distance of 1.5 metres, thus enabling much more convenient and cost-effective equipment to be used (See below).

All of this means that for test engineers, increased frequencies, new package technologies, great antenna counts and the like, will make it extremely difficult to keep capital and operating costs down.

While new OTA testing techniques can certainly help they bring other challenges with their successful implementation, whether that is measurement accuracy or taking into account business considerations such as minimising the impact on time to market to the development of new, innovative test and measurement solutions.

As mentioned, with the introduction of mMTC and URLLC in particular, 5G facilitates a whole new range of applications from automated driving to IoT and cloud robotics. This broadens the field of test and measurement to encompass additional requirements such as safety and security, where reliability, deterministic low latency, authentication and encryption are critical.

A T&M equipment supplier with products already in these markets and an experience in topics such as cybersecurity and radio monitoring will have much to contribute to 5G testing in these areas.

Clearly 5G test and measurement is a complex and rapidly evolving topic. Successful T&M equipment suppliers will need to build on their success and experience in 4G, evolving the software and hardware where feasible to minimise costs both for themselves and for their customers. They will need to leverage their close relationships with those customers and work together to develop solutions for 5G that will enable those customers to access the new markets first.

Taking an active role in driving the new standards from within the standards bodies, paarticularly the 3GPP, is providing the advanced insight that will also facilitate early market access.

Finally, as new 5G-enabled applications evolve, many industry watchers suggest that single-source, broad-range T&M suppliers will have most to offer to companies which are keen to make early gains in those developing markets.

Author details: Meik Kottkamp is Technology Manager Wireless at Rohde & Schwarz

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Meik Kotthamp

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