Signals Research Group trusts the prototype measurement system designed by Rohde & Schwarz to meet the aggressive timeline of early 5G adopters. The US-based research consultancy used the R&S®TSMA autonomous drive test scanner for their independent 5G test network benchmark study to collect downlink performance metrics for the Beam Reference Signals (BRS), including RSRP, CINR, RSRQ, PCI, etc., of 28 GHz millimeter wave radio signals. Signals Research Group (SRG) reported in February 2018 that measurements had been conducted in Houston, Texas, where Verizon Wireless operates a 28 GHz trial network.

Verizon is currently using the 5GTF specification that we discussed in a previous post. It is important to know that 5GTF and 5G New Radio (5G NR) are two separate sets of specifications with some obvious incompatibilities between them. However, given the SRG study’s focus and the emphasis on millimeter wave propagation, the findings from these measurements could be equally applicable to the industry-defined 3GPP standard 5G NR (the “real 5G”).

SRG’s measurement campaign examined, in particular, the promises of mmWave spectrum for mobile communications (mmWave signal propagation). Other targets included the characterization of the most likely radio conditions of fixed customer premise equipment (CPE) in the 5GTF network environment. This helped to determine the best physical location for a CPE in a home or office setting.

5G benchmark study methodology

In the report preview, SRG describes the methodology for the independent 5G test network benchmark study as follows: “For our benchmark study of the Verizon 5GTF commercial trial network, we used the Rohde & Schwarz TSMA scanner. R&S designed the prototype measurement system, featuring the R&S®TSMA autonomous drive test scanner, which contains the  R&S®TSME ultra-compact drive test scanner and an integrated PC, to meet the aggressive timeline of early 5G adopters. To enable measurements at 28 GHz, the scanner’s frequency range is extended by using a down-conversion approach.

Utilizing fast frequency tuning algorithms, a special version of R&S®ROMES drive test software allows Rohde & Schwarz to down-convert up to eight 100 MHz wide component carriers transmitted at 28 GHz into an intermediate frequency range that can be processed and displayed. In the Houston market, we identified four 100 MHz wide component carriers within each cell sector.”

The SRG study involved a combination of walk tests and stationary tests. The walk tests were conducted with an omnidirectional antenna; for the stationary tests, a horn antenna was used to emulate the CPE’s receive situation and to determine the best physical location for it in a home or office setting.

The entire measurement solution is fitted into a battery-powered backpack that lasts up to eight hours, and thus enables coverage measurements in the field. SRG collected all log files for their tests with a single charge, so they never had to stop testing to change batteries.

An external PC or tablet controls the backpack, and the R&S®ROMES drive test software displays several coverage-related parameters for 5GTF such as BRS RSRP, BRS RSRQ, BRS CINR, PCI, and more. Users can easily determine the strongest beam index in a given area. They can also detect potential multi-path issues via channel impulse response measurements.

For coverage evaluation, RSRP and CINR metrics are of most interest. Since the industry is also interested in data rates, SRG made some CINR adjustments and, together with some assumptions, they calculated an estimated peak data rate at given receive locations.

5G test network benchmark study results

For obvious reasons, we can only report initial results from the publically available SRG report preview, on which this blog post is based. The 5GTF measurements provided useful information about 28 GHz performance attributes:

  • They indicated the amount of signal diffraction due to window glass, buildings, parked cars, and even balding heads.
  • They analyzed the impact of tree foliage, varying near-line-of-sight (LOS), non-line-of-sight (NLOS) and near-line-of-sight conditions, and school buses passing just in front of the horn antenna at the receiving side.

SRG summarized that they “walked away pretty stoked about the prospects for 5G millimeter wave systems”.  However, the report concludes that millimeter waves and beamforming are not a panacea that can fulfill the world’s fixed and mobile broadband needs. Anything and everything can influence a millimeter wave signal – to varying degrees.

But if the goal is to deliver downlink/uplink broadband speeds that exceed what most US consumers can get from their fixed-line service provider today, then the Verizon approach can make ends meet. However, if end-users expect reliable connections at Gigabit-per-second speeds, well, then some might get disappointed …

So much from the preview report on the 5G test network benchmark study conducted with our 5G prototype measurement solution.

In my next post, I’ll talk about 5G NR, the global standard for a unified 5G wireless air interface. I’ll explain how it differs from Verizon’s 5GTF specification and how Rohde & Schwarz mobile network testing enables initial coverage measurements.

Stay tuned!

Read the previous posts of our 5G series:
– Learn in part 1 “The role of mobile network testing on the path to 5G” how 5G represents a paradigm shift in the development process of the next generation of mobile communications.
– Learn in part 2 “5G: initial 5GTF coverage measurements” how the US operator Verizon Wireless targets fixed wireless access (FWA) in the 28 GHz frequency band.