By Majeed Ahmad
Another disruptive generational change in wireless has officially arrived with the announcement of a finished 5G standard. The 3rd Generation Partnership Project (3GPP) has announced the completion of the Release 15 specification for 5G New Radio (NR). It consists of a standalone version and a non-standalone version that can operate simultaneously, and both are forward-compatible with future 5G standards.
This brings forth another day of reckoning for the design and development of test solutions that can keep up with the breathtaking pace of 5G innovation. These test and measurement solutions allow engineers to develop accurate signal propagation models and thus help expedite the design process at the chip, device and network levels.
The NR standard encompasses new concepts and technologies that include new radios, frequencies and the ability to direct signals at users. That inevitably demands new test procedures that characterize 5G designs while the standards continue to evolve.
The dilemma is how to quickly identify test challenges and continuously improve test functionality in a timely manner as 5G standards evolve, especially when there’s still more work to be done regarding 5G infrastructure, chips, modems, phones and antennas. Moreover, alongside the evolution of the 5G standard, the wireless industry has to manage millimeter wave (mmWave) adoption as well as control the cost of new test and measurement solutions.
Evolution of 5G Standards
For a start, it's worth mentioning that the transition from 3G to 4G was smoother because of similarities like frequency coverage, signal propagation and other engineering parameters. However, while the new NR standard leverages the legacy LTE channels in its non-standalone version, mmWave frequencies will be used as the data pipe to provide high-bandwidth services.
Furthermore, the NR specification utilizes several chunks of the new spectrum ranging from 2.5 GHz to 40 GHz frequencies. The FR1 frequency range — spanning from 450 MHz to 6 GHz — conforms to the existing LTE deployments where testing challenges have been successfully managed. However, while engineers will continue to use the sub-6 GHz frequencies, the NR deployments also utilize mmWave frequencies to offer five times more bandwidth currently available on LTE networks.
And everything changes at higher frequencies, including beamforming, over-the-air (OTA) testing and propagation losses. First and foremost, the use of mmWave frequencies will inevitably lead to far more complex radios than currently being used in LTE designs. That, in turn, translates into new test challenges relating to higher carrier frequencies, wider bandwidths, advanced antennas and OTA measurements.
Take beamforming, for instance, which adds another layer of complexity to 5G designs. On one hand, it mandates accurate RF measurements in active beamforming environments; on the other hand, too many RF tests make this practice costly and tedious. Also, beamforming demands changes in RF chip design, both for power amplifiers and transceiver ICs, and for minimizing propagation loss, antenna arrays must also be integrated into the RF chipset or module.
Here, the cabled test methodologies become less viable, giving way to a new breed of OTA solutions that are bound to manage the cost detriment. In other words, the OTA methodologies have to be redefined for the Release 15 specification all over again. And that includes the elimination of specific OTA tests while simplifying others.
Viable 5G Testing
So how do engineers and test professionals maintain economic efficiencies while creating test and measurement solutions for the new version of the 5G standard? How can they develop new test methods for speedy deployments of new 5G technologies built around the NR standard? Especially when the early NR networks are going to be deployed with dual connectivity while operating in multi-standard and multi-band modes?
Moreover, new devices and radio access technologies will be added as the 5G standards evolve. Amid all this uncertainty, billions of dollars of investment are at stake, and what's required is globally accepted conformance and certification processes that can economically validate 5G systems and test the emerging 5G equipment.
So it's imperative that platform-based test solutions are employed to deal with quickly changing 5G design landscape. This will simplify adding test use cases for the new versions of the 5G standard. Additionally, a platform-based approach will allow engineers to reuse the same measurement investments in multiple phases of the 5G design cycle.
The following section will provide a few test use cases catering to both sub-6 GHz and mmWave 5G designs. It will show how a combination of hardware and software components can help create modular platforms for testing sub-6 GHz and mmWave 5G designs.
5G NR: Test Case Studies
First, let's take the example of a modular test solution that caters to the sub-6 GHz spectrum. It comprises a vector signal transceiver (VST) and measurement software specifically designed for sub-6 GHz 5G NR systems. Here, the transceiver system features 1 GHz of instantaneous signal generation and analysis bandwidth of up to 6 GHz.
It works alongside the NI-RFmx NR measurement software which has evolved in conjunction with the 3GPP specifications. The software offers 5G waveforms measurement capability that is compliant with the non-standalone version of the NR standard. It allows designers to test both OFDMA and DFT-s-OFDM carrier aggregated waveforms with flexible subcarrier spacing from 15 kHz to 120 kHz.
The next test case study relates to NI's mmWave transceiver system that works alongside application-specific software and can transmit and receive wide-bandwidth signals of up to 2 GHz bandwidth in real-time, covering the frequency range of 27.5 GHz to 29.5 GHz. NI has employed this transceiver system both as an access point and user device for channel measurements in the 3GPP and Verizon 5G specifications.
The communications prototyping systems can help 5G designers understand and measure physical characteristics of the new mmWave spectrum. The transceiver system works with baseband software that emulates the physical layer compatible with the proposed 3GPP and Verizon 5G specifications. It is ready-to-run software based on a source code developed in the LabVIEW system design environment.
The 5G juggernaut is just beginning, and is unchartered territory for the test and measurement industry. So, in order to create cost-effective as well as scalable test solutions for the embryonic 5G NR standard, a modular approach has its merits.
A new era in wireless communications has kick-started with the arrival of 5G NR standard. Buckle up for a series of new test methods and platforms.