5G NR OTA (Over The Air) Testing: Equipment and Measurements

5G OTA (Over-The-Air) testing refers to the process of evaluating and validating the performance of 5G devices, networks, and components in real-world conditions, without the need for physical connections or cables. Instead of using wired connections, OTA testing involves transmitting and receiving wireless signals through the air, simulating the conditions that users experience in everyday usage scenarios.

Let’s dive into 5G NR test and measurement equipment, including 5G OTA test equipment.

5G OTA (Over The Air) test equipment includes solutions from Keysight, Anritsu, R&S (Rohde & Schwarz), ETS-Lindgren, EMITE designs, and MVG solutions. 5G NR (New Radio) uses different frequency bands across different parts of the world. Moreover, there are significant changes in the 5G NR technology compared to the LTE standard, which include the use of mmWave frequencies, massive antenna arrays, dynamic PHY attributes, beamforming, and so on. Physical layer attributes are subcarrier spacing and the number of slots per subframe, among others.

Purpose of 5G Over-the-Air Testing

Here’s an overview of the key aspects and purposes of 5G OTA testing:

• Performance Assessment: OTA testing allows for the assessment of various performance parameters of 5G devices and networks, including signal quality, throughput, latency, coverage, and reliability.
• Antenna Characterization: Antennas play a crucial role in 5G communication systems. OTA testing enables the characterization of antenna performance, including radiation patterns, gain, efficiency, polarization, and beamforming capabilities. This helps ensure that devices can effectively transmit and receive signals in different directions and orientations.
• Conformance Testing: It ensures that 5G devices and networks meet specified performance criteria and interoperability standards set by 3GPP and FCC.
• Beamforming and MIMO Testing: OTA testing evaluates the effectiveness of Beamforming/MIMO techniques by analyzing signal propagation, spatial diversity, and beam steering capabilities in real-world scenarios.
• Field Trials and Optimization: OTA testing is often conducted during field trials and network deployments to optimize coverage, capacity, and quality of service. By assessing the performance of 5G devices and networks in actual deployment environments, operators can identify and address issues related to interference, handovers, mobility management, and overall network performance.
• User Experience Evaluation: Ultimately, OTA testing aims to ensure a seamless and satisfactory user experience with 5G services and applications.

Image alt: Keysight 5G test equipments

5G OTA (Over The Air) test setup should provide provisions to test DUT (Device Under Test) in both the near-field zone (Reactive, Radiating) and the far-field zone from the antenna used in the testing. The region up to the distance of $2D^2 / \lambda$ from the antenna is referred to as the near-field region.

Where, $D$ is the antenna diameter and $\lambda$ is the wavelength of free space.

The region above the distance of $2D^2 / \lambda$ is referred to as the far-field region.

The distance up to $0.62 * (D^3 / \lambda)^{0.5}$ is known as the reactive near field, whereas the distance between $0.62 * (D^3 / \lambda)^{0.5}$ and $2D^2 / \lambda$ is known as the radiating near field.

There are two frequency ranges used by 5G Base Stations and 5G UEs (User Equipment) viz. FR1 and FR2. FR1 spans from 450 to 6000 MHz, and FR2 spans from 24250 to 52600 MHz. Hence, 5G OTA test solutions or equipment should support both of these frequency ranges.

The figure below depicts equipment available from Keysight Technologies for 5G measurements. These Keysight 5G solutions are useful for performing 5G measurements, which includes a list of 5G measurements required to be performed on transmitter and receiver parts of the 5G Base Station and 5G UE (User Equipment).

Image Courtesy: Rohde & Schwarz

The figure above depicts a 5G OTA testing setup from Rohde & Schwarz. The setup uses an R&S spectrum analyzer. Refer to 5G OTA testing by R&S for more information.

The following measurements are required to be performed during 5G OTA testing:

• EIRP: Effective Isotropic Radiated Power.
• TRP: Total Radiated Power.
• EIS: Effective Isotropic Sensitivity.
• TIS: Total Isotropic Sensitivity.
• EVM: Error Vector Magnitude.
• ACLR: Adjacent Channel Leakage Ratio.
• SEM: Spectrum Emission Mask.

5G Test and Measurement Companies and Their 5G Testing Solutions

The following table mentions 5G OTA test and measurement companies and their solutions.

The other 5G OTA test and measurement companies are NI (National Instruments), NSI-MI, Boonton, Noisecom, and so on.

Conclusion

Overall, 5G OTA testing plays a critical role in the development, deployment, and optimization of 5G networks and devices, ensuring that they meet performance expectations and deliver the promised benefits of high-speed, low-latency, and reliable wireless connectivity.

References

• 3GPP TS38.521 part-1, part-2, part-3 and part-4
• TS 38.101 - User Equipment Radio Transmission and Reception
• TS 38.104 - BS Radio Transmission and Reception
• TS 38.141 - BS Conformance testing