5G Base Station Manufacturing: Yes, OTA Testing Can Be Done Cost-effectively
2019-04-05 | 5 min read
5G is disrupting the entire wireless lifecycle, from research and development (R&D) to the field. It represents a significant increase in complexity due in part to massive multiple input multiple output (MIMO), millimeter-wave (mmWave) frequencies, and beamforming. For 5G to be successful, network equipment manufacturers (NEMs) must find ways to test infrastructure equipment cost-effectively, provide high quality in accelerating timelines, and remain flexible to address spikes in volume, channel requirements, and more frequency bands.
The Quest for Wider Bandwidths
With 5G and the pursuit of wider bandwidths, NEMs have had to leave the familiar, yet very crowded frequency spectrum below 6 GHz. They need to operate at uncrowded frequencies in the more difficult mmWave spectrum. Referred to as frequency range 1 (FR1) in the 5G New Radio (5G NR) standard specification, frequencies below 6 GHz (recently extended to 7.125 GHz) are drastically different from the mmWave frequencies of 5G NR’s frequency range 2 (FR2), which go from 24.25 GHz to 52.6 GHz (soon to be upgraded to 114.25 GHz).
Less utilized than low frequencies, mmWave spectrum is giving users the data rates they want. mmWave spectrum allows wider bandwidths because many other applications do not use this space. However, the propagation characteristics of mmWaves are an issue. Higher diffraction, penetration, and atmospheric loss generate high path loss. Path loss, in turn, limits the range of wireless signals. This has prompted the use of phased array antennas and eliminated the space previously used to place probes.
Clearly, 5G results in a disruptive shift for base station manufacturing test operations from conducted test methods to over-the-air (OTA) testing. In an OTA measurement set-up, excess path loss between the instruments and the device under test (DUT) reduces the signal-to-noise ratio (SNR). Low SNR causes poor error vector magnitude (EVM) and adjacent channel power ratio (ACPR). ACPR is particularly important to minimize interference.
Overcoming Path Loss While Meeting Manufacturing Goals
R&D engineers can use high-performance microwave instruments to overcome the mmWave path loss challenge in their measurement set-up. In manufacturing, using such instruments can be overkill. They also increase the cost of test significantly. A banded solution that combines instruments of lower frequency range with an external mmWave transceiver provides the right balance between performance and price. Such a solution has the up and down conversion at the measurement plane. This reduces path loss and provides the needed performance at a much wider power range. The result is an affordable and flexible 5G manufacturing test solution for high frequencies.
Figure 1 highlights how a remote mmWave transceiver head reduces insertion loss in an OTA test set-up.
mmWave Challenges Are Intimidating, Not Insurmountable
mmWave frequencies are particularly challenging for NEMs. They provide link budget issues due to higher power loss at these frequencies. They also create the need for OTA testing, as the antennas are directly bonded onto the radio chip. These factors reduce the dynamic range, making accurate measurements significantly more difficult.
While mmWave frequencies may be intimidating to many, NEMs can effectively address the challenges they generate by partnering with test and measurement experts. Keysight provides innovative solutions for 5G base station manufacturing test that address the technical complexity brought by 5G while controlling its impact on cost and time.
Keysight’s OTA expertise goes beyond base stations. It spans the entire mobile ecosystem – component manufacturers, device makers, and NEMs, and the DUT workflow- R&D, design validation, and manufacturing. Our mmWave OTA portfolio for devices covers RF/Antenna/RCT, Protocol/Functional/PCT, and mobility and performance. Keysight’s gNB OTA portfolio spans RF/antenna, protocol/functionality performance/IoT, and manufacturing.
For more information on OTA challenges and solutions, join us at Keysight World on May 14, 2019. There is a focused session on this hot topic in the 5G track.