5G Researchers Take Aim at Moving Target
Research on 5G is proceeding on a variety of fronts, with organizations addressing topics ranging from algorithm development to antenna design. Products available for 5G test include software, software-defined radios, high-bandwidth oscilloscopes, arbitrary waveform generators, vector network analyzers, and reference solutions as well as complete communications test systems.
At this point, 5G is somewhat of a moving target, with frequencies not yet defined. For the United States, last October the FCC proposed new rules for wireless broadband at frequencies above 24 GHz; the FCC said the proposed rules are an opportunity to move forward on creating a regulatory environment in which emerging next-generation mobile technologies—including 5G mobile service—can take hold.
And as the standard evolves, universities and university-based research organizations are playing key roles. One such organization is the 5G Innovation Centre (5GIC), which opened a new building on the University of Surrey campus last September. Illustrating the international focus of the 5G research effort, in October the University of Surrey hosted a delegation led by Zhuang Rongwen, vice-minister, cybersecurity administration, of China, which saw a demonstration that showed how the new 5G-Sparse Coding Multiple Access radio waveform can support at least 300% more Internet-of-Things (IoT) devices than would be possible with 4G.
Keysight Technologies works with organizations including 5GIC (particularly through its acquisition last August of Anite, a supplier of software for wireless research) as well as with universities. Recently, Keysight, in collaboration with The University of California, San Diego (UCSD), said it has demonstrated the world’s first 64 (8×8) and 256-element (16×16), 60-GHz silicon wafer-scale phased-array transmitter with integrated high-efficiency antennas for Gb/s communications at 100 to 200 meters. With this demonstration, Keysight and UCSD have proven that a 5G communication link is not only possible, but also can deliver record performance, the company reported.
Keysight’s collaboration with UCSD builds on an earlier effort between the university and TowerJazz, which resulted in development of the industry’s first 64- and 256-element system-on-a chip (SoC) phased arrays operating at 60-GHz. Each wafer-scale SoC comprises a 60-GHz source, amplifiers, a distribution network, phase shifters, voltage-controlled amplifiers, and high-efficiency on-chip antennas. The chips were designed to meet the needs of 5G high-performance Gb/s data-rate communication systems with beamforming capabilities, and they also can find use in aerospace and defense systems.
To develop and demonstrate the communication link, UCSD relied on a suite of Keysight instruments (Figure 1) that included the M8190A arbitrary waveform generator, the E8267D PSG vector signal generator, and the DSOS804A Infiniium S-Series high-definition oscilloscope with 10-bit ADC. Researchers employed the Keysight E8257D PSG analog signal generator for local oscillator generation.
Courtesy of Keysight Technologies
The 60-GHz 802.11ad waveform UCSD required for the development effort was generated using Keysight’s Signal Studio software and analyzed using its 89600 VSA software. Keysight’s 81199A Wideband Waveform Center software also proved valuable, helping UCSD link transmit and receive, apply digital pre-distortion, and improve error-vector-magnitude.
The test-equipment lineup for the UCSD project illustrates the breadth of Keysight’s hardware and software offerings. “The best part about 5G for us is that 5G is not just a new air-interface design,” said Martha Zemede, 5G and IoT outbound marketing lead at Keysight. “The breadth of technology investment for this next generation means opportunity for us across our wide product line.”
From algorithms to analyzers
Dr. Li-Ke Huang, research and technology director at Cobham Wireless, said, “Cobham Wireless is actively involved in creating the core algorithms, the concept validation methods, and technologies of the potential 5G air interfaces with innovative, enabling, processing-platform architectures and technologies.”
He added, “The industry-standard TM500 network test system has recently added more LTE-Advanced features including 256 QAM, feICIC [further enhanced Inter-Cell Interference Coordination], five component carriers, and multi-RAT capability, which are consolidating in 4G systems and are all stepping stones on the path to 5G.”
Cobham is prepared for proposals for 5G to operate above 24 GHz. Huang said, “Our range of spectrum and signal analyzers includes microwave synthesized spectrum analyzers, scalar analyzers, and tracking generators up to 46 GHz”—including handheld and bench models. “They target R&D, EMI precompliance, manufacturing, installation, and service,” he said. “In the network infrastructure testing domain, we are actively researching into link-level technologies including modulation, waveform, beamforming, overall system designs, and the enabling of RF and platform technology components internally or in cooperation with leading partners that are domain experts in frequencies above 24 GHz.”
As for participating in 5G organizations, Huang said Cobham Wireless is a founding member of the 5GIC, which affords an opportunity for cooperation with other member companies including Aircom, the BBC, British Telecom, EE (the British mobile network operator and ISP formerly named Everything Everywhere), Fujitsu, Huawei, Rohde & Schwarz, Samsung, Telefónica, and Vodafone. “The 5GIC incorporates the world’s leading independent testbed for trialing emerging 5G ideas, proving concepts, validating standards and vendor inter-operability testing, and enabling the development and testing of 5G prototype technologies in a real-world situation,” he said. “The testbed covers an area of 4 km2, comprising indoor and outdoor environments, and supports broadband mobile and IoT.”
The air interface is one specific area that Cobham is addressing. “A new 5G air-interface design is required to meet the demanding and diverse design targets, which will have to be both flexible and programmable,” Huang said. “The software-defined air-interface design principle that is being proposed for 5G will allow the fundamental air-interface parameters—or even the air-interface architecture—to be dynamically changed according to the service scenarios.”
He said that at the Cobham Wireless booth at the Mobile World Congress 2015 (Figure 2), Dr. Razieh Razavi from the 5GIC demonstrated two proposed 5G air-interface algorithms that Cobham Wireless developed and compared their performance with that of OFDM. The demonstration showed that both filter bank multi-carrier (FBMC) and generalized frequency division multiplexing (GFDM) exhibit superior spectral purity compared with OFDM. “While FBMC is better than both OFDM and GFDM in terms of sideband suppression,” Huang said, “GFDM proves the most robust when a carrier offset is applied, and therefore both of the new air interfaces are likely to be used when 5G is deployed.”
Courtesy of Cobham Wireless
Communications system design
James Kimery, director for wireless research and software-defined radio at National Instruments, said, “5G research covers many design areas including communications systems, antennas, software, algorithms, core networks, and much more. Almost every aspect of a 5G network will be new, and therefore all components of the network must be designed, simulated, and prototyped.”
NI, he said, focuses on communications system design through the company’s platform-based approach encompassing software-defined radios (SDRs) and the LabVIEW Communications System Design Suite (Figure 3). “With this modular hardware and software platform, researchers can quickly transition from concept to prototype,” he said. Researchers can use NI SDRs and the LabVIEW suite to iterate on initial designs to optimize them based on real-world performance for both the UE and eNodeB—and even networks. “NI’s platform-based design approach spans more than the layer 1 algorithm design … [extending to] complete 5G communications systems, because the software can be developed, reused, and modified across multiple nodes,” he said.
Courtesy of National Instruments
Kimery added, “5G channel sounding is a narrow but important part of 5G system development. Wireless channels for the new spectrum must be measured to understand the channel characteristics and develop new algorithms and systems. Because of the flexibility of the NI platform, our SDRs and LabVIEW Communications also can be used for both prototyping as well as channel sounding.”
With regard to work at high frequencies, Kimery said NI has been providing millimeter-wave (mmWave) prototyping solutions for several years. “We have customers in academic research and industry prototyping with our platform to meet the design challenges of the next generation of wireless,” he said.
“For example,” he added, “NYU Wireless’ Professor Ted Rappaport has been using NI’s PXI FlexRIO modules and FAMs [FlexRIO adapter modules] with LabVIEW, and his team has collected data in New York City and Austin, Texas, over a number of frequencies including 28 GHz, 38 GHz, 72 GHz, and V-band. Professor Rapport is known as a pioneer in mmWave research, and his channel measurements have been used extensively across the industry.”
PHY layer testing
Chris Loberg, senior manager, performance instruments marketing, Tektronix, said his company addresses PHY layer testing of mmWave and wideband wireless links and radios as well as validation of the performance of high-throughput optical backhaul links.
For the optical backhaul, he said, Tektronix has announced the DPO77002SX 70-GHz oscilloscope along with the OM4525 optical modulation receiver for coherent optical formats. For NRZ-based optical formats, Tektronix introduced the DSA8300 sampling scope mainframe with the 80C15 (multimode and single-mode) optical sampling module.
“We are active in optical backhaul standards committees helping to define testing approaches in the IEEE 802.3 and OIF-CEI families of standards,” Loberg said. “In addition, we have collaborated with the French research organization IRCICA on a project to build better backhaul capacity for the future of 5G in France.” He added, “Tektronix coherent optical network products like the OM4525 coherent optical analyzer are ideal for use in seeking optical network optimization like the project at IRCICA.”
For mmWave and wideband wireless links, Loberg said, “Tektronix provides validation of 5G wireless signal modulation using the DPO77002SX 70-GHz oscilloscope with SignalVu software for demodulation and spectral analysis” (Figure 4). “SignalVu combines the signal-analysis engine of the RSA5000B real-time spectrum analyzer with the powerful triggering capabilities of the industry’s widest bandwidth DPO70000SX oscilloscope series,” he said, “enabling designers to evaluate complex signals up to 70 GHz without a need for an external downconverter.”
Courtesy of Tektronix
Combining hardware, software
In addition to the equipment used in the UCSD project, Zemede at Keysight listed many products the company makes that can serve in 5G test, including the W1906BEL 5G Baseband Exploration Libraries. “Keysight introduced the industry’s first 5G Exploration Libraries more than a year ago, with many updates since the introduction, providing ready-to-use reference signal processing intellectual property (IP) for 5G research,” she said.
Keysight also offers reference solutions—combinations of hardware and software—including the 5G Waveform Generation & Analysis Testbed Reference Solution and the 5G Channel Sounding Reference Solution. The latter, Zemede said, “… combines hardware, software, and measurement expertise providing the essential components of a 5G channel-sounding test platform, allowing researchers to define new channel models at image frequencies.” The testbed reference solution enables engineers and researchers to generate and analyze various types of 5G candidate and custom waveforms at RF, microwave, and mmWave frequencies with modulation bandwidths of up to 2 GHz.
For exploration beyond 24 GHz, Zemede said the M8190A precision arbitrary waveform generator and E8267D PSG vector signal generator with wideband I/Q inputs can generate wideband (2-GHz) test signals up to 44 GHz. “Higher frequencies can be achieved through the use of an array of upconverters that we offer,” she added.
“For signal analysis up to 50 GHz, the solution employs a PXA signal analyzer with S-Series oscilloscope,” she continued. “Higher frequencies, up to 90 GHz, can be achieved with a combination of Keysight’s M1971E wideband smart mixer along with a PXA and S-Series oscilloscope.”
Complementing the M8190A arbitrary waveform generator on the receiver side is the M9703B AXIe 12-bit, 3.2-GS/s wideband digitizer, which, Zemede said, offers phase-coherent channels scalable from eight to 104 channels with 1-GHz analysis bandwidth with interleaving mode. For image applications, Keysight’s M9362A 50-GHz multichannel quad downconverter is used in conjunction with the M9703B digitizer. In addition, the company’s PNA vector network analyzers provide mmWave capability for characterizing components.
Vendors continue to roll out test products for 5G. As this article was going to print, Rohde & Schwarz announced in December the R&S TS-5GCS channel sounding software (Figure 5), which works with an R&S FSW signal and spectrum analyzer and an R&S SMW200A vector signal generator to make it possible to measure channels in high-frequency bands. The R&S SMW200A has a frequency range of up to 40 GHz and is used as the sounding signal source. The R&S FSW operates as a receiver and can be employed with various frequencies and bandwidths. The R&S FSW85, for example, enables users to analyze sounding signals up to 85 GHz without an external mixer. Adding the R&S FSW-B2000 option extends the possible analysis bandwidth to 2 GHz.
Courtesy of Rohde & Schwarz
The R&S TS-5GCS software includes a selection of standard sounding signals such as the familiar FMCW (chirp) signals from radar technology. Employing these signals for channel sounding enables users to further optimize their sounding sequences in terms of spectral purity and crest factor, the company said. The sounding signals can be replayed directly on the R&S SMW200A signal generator.
And in December, Keysight announced a major update for its SystemVue 5G library in three main areas: PHY/modem, beamforming, and channel modeling. Zemede said Keysight added new baseband physical-layer modem technologies and reference IP as well as transmit/receive support for Universal Filtered OFDM (UF-OFDM), Filtered-OFDM (F-OFDM), FBMC, and GFDM (transmit only). The update also added system-level reference designs for digital, RF, and hybrid beamforming and parallelized RF behavioral models to be able to see the effects of beamforming algorithms at the system level. The update offers Extended 3GPP 3D MIMO channel modeling for 4G and added mmWave custom-channel-model integration.
In addition, Anritsu introduced an E-band option for its ShockLine MS46500B Series two- and four-port performance VNAs. The company said the option makes the MS46500B suitable for testing mmWave passive components used in 5G small-cell networks. From dedicated 5G tools to general-purpose hardware and software that can be applied to 5G research, you can expect many more products to follow.
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