5G is pushing the boundaries of wireless communications, enabling use cases that rely on Gbps data rates, exceptionally low latency and ultra-high reliability. These stringent requirements need increased mobile network densification, with the installation and activation of many new cell sites and small cells. To deliver quality of service and ensure network performance, mobile network operators must deploy and validate these 5G sites accurately and efficiently. As they move to 5G, operators still need to support, maintain and test existing wireless technologies, i.e., 3G, LTE, as well as 5G-NR. This is already the reality for many operators, reflected in a recent EXFO survey where over 40 percent of respondents replied that wireless bands deployed in their regions included a mix of sub-2.4 GHz, sub-6 GHz and mmWave frequencies.

5G Field Testing Challenges

5G is presenting new challenges for mobile network operators, contractors and field service technicians to validate networks. The separation between fiber and RF environments is becoming blurry; it’s less clear where one ends and the other starts. Given this evolving environment, these are the main challenges for 5G field testing:

  • A new air interface is now deployed, with advanced technologies like mMIMO and beamforming making the RF environment more complex to navigate
  • There are tighter constraints on network synchronization and any timing issues will impact RF performance: user equipment (UE) transmitting at the same time as the radio in time-division duplex (TDD) systems, cell sites interfering with each other, handover issues and slow to no throughput
  • Analyzing spectrum can be difficult because of the wider bandwidths and more interference falling inside the channel, making troubleshooting a longer process. Intermittent signals such as TDD add complexity to the spectrum analysis
  • To deploy 5G faster, the first non-standalone (NSA) 5G installations used 4G uplinks. Since 4G was powering these NSA networks, issues on the 4G network can degrade the 5G experience.

These operational challenges mandate new, innovative test processes. To get the most from their investments, operators need field-focused RF testing solutions that both scale and adapt as their networks change. To address this market requirement, EXFO developed an innovative, modular RF testing solution that adapts as the networks evolve.

EXFO’s 5GPro Spectrum Analyzer is the industry’s first field-tech optimized, scalable RF spectrum analyzer that delivers accurate RF over-the-air (OTA) measurements. It’s the only modular RF testing solution analyzing LTE and 5G NR environments, with the ability to analyze sub-6 GHz (FR1) and mmWave (FR2) bands using a compact, field-upgradable instrument. Designed for simplicity of use, the 5GPro Spectrum Analyzer enables field techs and contractors to easily identify and resolve issues and close out jobs faster.

The 5GPro supports several complex test scenarios:

Figure 1

Figure 1 The RTSA capability enables interfering signals to be easily identified.

Figure 2

Figure 2 The 5G NR signal analyzer supports mMIMO and beamforming characterization.

Catching Transient Interferers - Real-time spectrum analysis (RTSA) can show signals that are masked inside larger channel bandwidths. RTSA uses various color densities reflecting the intensity of the signal, enabling the interferer signal to be detected quickly (see Figure 1). The 5GPro Spectrum Analyzer is an RTSA with 100 MHz of analysis bandwidth that provides continuous acquisition of RF signals. Quick characterization of wireless signals and detection of intermittent interference is possible using the RTSA’s persistence and spectrogram view.

The 5GPro Spectrum Analyzer also brings innovation and intelligence to RF testing with a smart user interface, featuring built-in expertise and patent-pending features like intelligent peak detection and “snap to peak.” With snap to peak, field techs can use the touch screen to identify interferers with a moveable window, enabling the user to easily search for the highest amplitude interferer and attach a marker.

5G NR Signal Analyzer - The 5G NR signal analyzer capabilities of the 5GPro enable analyzing complex technologies like mMIMO and beamforming. A quick check of power parameters of the synchronization signal block validates whether all beams are being transmitted. As an example, Figure 2 shows a signal in the CBRS band around 3.5 GHz. If the cell site is operating correctly, the signal analyzer should receive eight beams (0 to 7), with RSRP, RSRQ and SINR for each beam.

The 5GPro Spectrum Analyzer supports the demodulation of 5G NR signals and can validate OTA performance of cell sites to ensure smooth communication with UE. This application will analyze up to 64 beams and display the 12 strongest, showing the corresponding power measurements and beamforming metrics.

As LTE is not going away soon, the 5GPro Spectrum Analyzer also demodulates LTE signals and provides key metrics, including sector and group ID, physical cell ID (PCI), duplexing mode (frequency or time), RSRP (dBm), RSRQ (dB) and RSSI (dBm).

Spectrum Analysis using Gated Sweep - TDD is a transmission protocol where the uplink and downlink signals are transmitted on the same frequency using synchronized timed intervals. Spectrum and interference analysis for TDD require the use of a measurement technique called gated sweep, which visualizes the uplink or downlink spectrum by only displaying data within a specified range of timeslots. The 5GPro Spectrum Analyzer can display TDD uplink or downlink signals with a simplified gated sweep, saving time when analyzing the spectrum or interference.

Validate Timing and Synchronization - As 5G has more stringent timing requirements, it is important to ensure all network elements are synchronized with the correct time of day, frequency and phase. This requires either a quick check of the 1588 PTP protocol, to ensure a valid link to the grand master (GM), or an advanced test to ensure proper timing accuracy with time error (TE). The 5GPro Spectrum Analyzer is part of the comprehensive FTB 5GPro test kit with easy to configure 1588 PTP and TE testing and a high accuracy GNSS receiver (see Figure 3). EXFO’s best-in-class timing and synchronization helps operators save some 90 percent in troubleshooting time.

Figure 3

Figure 3 A time error measurement used to validate timing accuracy at various points in the network.

RF Spectrum Analysis Over CPRI - With 5G NSA, RF spectrum analysis over CPRI is used to analyze the 4G uplinks that are the anchors of the 5G downlinks. Any passive intermodulation (PIM) or interference on the 4G uplink must be resolved because of the impact on the quality of the 5G communication. EXFO’s iORF provides an intelligent and automated way to perform RF spectrum analysis over CPRI, enabling users with any skill level to detect external or internal RF interference or PIM in less than two minutes. If the issue is external, the user can switch from the iORF application to the 5GPro Spectrum Analyzer to hunt for the interferer.

Single, Complete Test Solution

EXFO’s 5GPro Spectrum Analyzer is available on the FTB 5GPro test kit for a complete all-in-one solution to validate 4G and 5G networks. In addition to sub-6 GHz and mmWave spectrum testing, the FTB 5GPro supports fiber inspection and characterization, CPRI, eCPRI, O-RAN, RF spectrum analysis over CPRI, up to 100G Ethernet, timing and synchronization. This comprehensive solution reduces the number of devices field technicians need to carry, speeding jobs and reducing the total cost of ownership for operators and contractors.

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