The next generation of cellular communications technology, 5G, is emerging to handle ever-increasing demands for mobile data—which will be exacerbated by the proliferation of connected Internet of Things (IoT) devices. Right now, 5G is undergoing research at organizations like the 5G Innovation Centre (5GIC) at the University of Surrey.
A detailed definition of 5G has yet to emerge, but Professor Rahim Tafazolli, director of 5GIC and the Institute of Communication Systems, describes it as follows on the 5GIC website: “5G will intelligently understand the demands of users in real time, dynamically allocating network resources depending on whether the connected device needed voice or data connectivity.”1 As for the 5G timeline, experts predict 5G will be in place by 2020.
Meanwhile, there is work to be done. For the United States, the FCC has issued a Notice of Inquiry regarding the use of the spectrum above 24 GHz for 5G. According to chairman Tom Wheeler, “This Notice of Inquiry we adopt… explores the possibility of facilitating the use of a huge amount of spectrum that could be used strategically to help meet the growing demand for wireless broadband.” He added, “By using innovative technologies that can simultaneously track and acquire multiple signals reflecting and ricocheting off obstacles in the physical environment, future devices might be able to leverage much higher frequency bands, those above 24 GHz, for mobile applications.”
Michael Barrick, business development manager at Anritsu, summarized the current state of 5G research: “While many institutions, carriers, and even infrastructure vendors have announced 5G projects, work to define 5G standards has not begun. Generational improvements to the 4G LTE standards continue, with work just being completed on Rel. 12 and starting on Rel. 13. The current industry thinking is that the ‘jump’ in technology that will signal the change from 4G to 5G will occur around the 2020 timeframe, and 5G concepts like ‘massive MIMO,’ millimeter-wave wideband channels, interference management, and support for IoT will all be included.”
The 5G vision
Roger Nichols of Keysight Technologies said, “The development of the fifth-generation of wireless will be across a broad range of diverse technologies. Virtually every aspect of the network, from the core network design, to the air-interface, to the UE/terminal architecture itself, will need to be changed to address the vision that has been painted.” Nichols leads Keysight’s 5G program, established in 2013 when the company was Agilent Technologies, and he reports to Keysight’s CTO Jay Alexander.
According to Nichols, “Wireless communication presents three significant areas that drive the need for testing. The first is that it represents at least one part of the communication link over a very hostile interface (the air). To maintain communication links, devices and systems have to operate to rather exacting tolerances, and researchers, designers, and manufacturers have to know that their approach will work and will meet the customer expectation.”
The second area, he said, stems from most wireless communications systems operating over a spectrum and in a manner regulated by most governments around the world. “The designers of these systems need to know that what they have done or will do is consistent with the constraints placed by these regulatory bodies,” he said.
And third, he said, a usable communications system must comply with accepted standards. “Designers and manufacturers must be confident that their work meets those standards,” he said.
In each of these three cases, he added, “Measurement companies like Keysight create solutions that enable engineers to see how their designs are working, ensure they meet regulatory standards, and are consistent with the industry standards to ensure compatibility around the world. 5G is no exception to this process, and given the demands of the industry, test solutions will have to provide even greater levels of insight in record time.”
From models to physical systems
Bob Kersey, marketing director for wireless test solutions at Anritsu, highlighted the key role test will play in 5G. “Test and measurement equipment is always central in moving any proposed new standard out of MATLAB models and into physical systems,” he said. “As standards become more complex and increasingly push the boundaries of technologies, test equipment must follow suit.” Consequently, a trend has been established to include test-equipment manufacturers in many of the early research initiatives.
Added Anritsu’s Barrick, “There is always a need for calibrated, traceable measurement systems in the development, manufacturing, and deployment of any new technology. At the physical layer, 5G will likely present extreme challenges in simulation of massive MIMO in the lab, particularly if tens or hundreds of independent and phase-coherent transceivers operating at millimeter-wave frequencies are needed.”
Andreas Roessler, technology manager at Rohde & Schwarz, elaborated on the challenges. 5G research, he said, involves frequencies in the millimeter-wave range and bandwidths of up to 2 GHz. Definition and standardization of a 5G physical layer will require adequate channel models, he said, adding, “As of today there are no detailed channel models available that cover all discussed scenarios and applications. These models especially are required for outdoor usage of these frequencies.” As for the role of instrumentation, he said, “Signal generation and analysis capabilities are required to design channel sounders and carry out measurements—typically, channel impulse response and amplitude and phase variations.”
Leveraging design and test
Charles Schroeder, director of product marketing for RF and wireless communications at National Instruments, said his company is applying its expertise in both embedded system design and test and measurement to the discovery and exploration phase of 5G as well as its design, development, and test. He said, “Engineers typically use RF test equipment, like a spectrum analyzer, to make performance measurements on communications hardware. However, one of the first roles of instrumentation in defining 5G is not to test the 5G hardware itself, but to validate new communications algorithms and approaches. For example, engineers are using spectrum analyzers to validate the new digital filter designs used in 5G waveform research.”
Schroeder added, “Given that customers are doing both physical measurements and algorithm validation, the ideal instrumentation platform enables engineers to validate both their algorithm design and hardware implementations. NI customers are using LabVIEW communications design software in combination with low-cost software-defined radio (SDR) hardware and PXI modular instrumentation to both prototype and test 5G solutions. For example, some of the world’s first millimeter wave and massive MIMO prototypes use the NI instrumentation platform.”
Courtesy of National Instruments
One example is the massive MIMO test bed at Lund University, which uses NI LabVIEW, USRP RIO, and PXI instruments (Figure 1).
He noted that NI has recently released the LabVIEW Communications System Design Suite, which offers a design environment closely integrated with NI SDR hardware for rapidly prototyping communications systems. “With LabVIEW,” he said, “communications designers can easily deploy their algorithms to processors and FPGAs, jump-start LTE and 802.11 applications, and drive innovation, all in a single integrated design environment.”
Exploring 5G
For its part, Keysight offers the SystemVue design software platform (Figure 2), and Nichols said the company is releasing the 5G Exploration Library for SystemVue in early 2015.
Courtesy of Keysight Technologies
“Our 5G Exploration Library is an excellent tool for researchers working on new waveforms and complex MIMO techniques, among many other things,” Nichols said. “Most already know that millimeter-wave (electromagnetic frequencies from 30 to 300 GHz) is getting a lot of attention due to the wide bandwidths available, which could yield ultrafast link speeds. We have been producing millimeter-wave test and measurement solutions since the 1980s and provided the first test solutions for WiGig and 802.11ad during the development of those standards.”
He noted that Keysight offers network analysis, signal generation, and signal analysis solutions for fundamental measurements at these frequencies as well as high-speed arbitrary waveform generators with waveform-creation software that allow researchers to explore complex and very broadband signals. “When these are coupled with our high-speed digitizers that contain flexible FPGA functionality as well as high-performance oscilloscopes plus our vector signal analysis software,” he said, “we provide extremely powerful tools to give engineers the insight they need.”
According to Roessler at Rohde & Schwarz, “The standard method to reach these frequencies in the mid and high gigahertz range is the up-conversion principle. Therefore, typically external mixers with frequency multipliers are used.” They not only multiply frequency, he said, but also the phase noise. Consequently, the signal generator providing the local oscillator (LO) frequency input and intermediate frequency (IF) input needs to have an excellent phase noise performance. “Rohde & Schwarz is known for its signal-generator solutions that have an outstanding phase noise performance,” he said. “In some cases, this performance can even be improved with additional hardware options.”
He specifically cited the SMW200A vector signal generator, a two-channel instrument for which both RF channels can provide up to 20 GHz in frequencies. “With this solution, it is possible to drive the LO and IF of an external mixer to reach millimeter-wave frequencies,” he said.
“A second, unique example,” he said, “is the Rohde & Schwarz FSW signal and spectrum analyzer. It is the only instrument on the market that supports frequencies up to 67 GHz in a single instrument while offering a built-in analysis bandwidth of 500 MHz. With external harmonic mixers, the frequency range can be extended up to 110 GHz. The 2-GHz wideband IF output of the FSW in conjunction with a Rohde & Schwarz RTO oscilloscope provides the required capabilities to analyze signals of up to 2 GHz of bandwidth.”
5G at the early stage
Asked about specific products, Kersey at Anritsu said, “5G is still at a very early stage, and much of the research is centered on fundamentals such as the multiple access and modulation schemes. Typically, research labs will use RF equipment, such as our vector signal generators, signal analyzers, and spectrum analyzers as part of their development of prototype and experimental systems. We have systems that integrate easily with MATLAB, allowing researchers a simple route to bridge from theory to physical realization.”
Barrick added, “Anritsu provides leading-edge 4G LTE test solutions for development, conformance/carrier acceptance, manufacturing, and repair of wireless devices.” He cited Anritsu’s capabilities in LTE-Advanced carrier aggregation and the company’s demonstration last November of support for Category 9 LTE with three-carrier aggregation (450 MB/s) using the MD8430A signaling tester (Figure 3). “Anritsu is on the extreme leading edge,” he said, “but we consider that we are still years away from 5G deployments, including test applications and products.”
Courtesy of Anritsu
Other companies, too, will be pursuing 5G test business. Although Aeroflex hasn’t reported details on its 5G strategy, it is a founding member of the 5GIC. The company’s website suggests that the TM500 family as well as the SVA vector signal analyzer and SGD digital signal generator will play a role.
Aeroflex’s current LTE product line includes a complete range of end-to-end test systems that covers R&D, performance, service, and manufacturing test applications for LTE-A TDD and FDD network equipment and terminals. Aeroflex says it has engineers working in centers around the world on its LTE and LTE-Advanced test systems to support the current and next generation of networks and devices.
Investment protection
As 5G evolves, engineers will want to take care in selecting test products that will remain useful. Schroeder at NI said, “As 5G solutions, let alone standards, are still in exploration and research, no one can describe with certainty how test-equipment needs will evolve for 5G. This uncertainty reinforces the need for a flexible test and measurement instrumentation platform such as PXI that allows for changing I/O requirements, higher bandwidths, and new waveform implementations. In contrast, organizations invested in legacy vendor-defined box instruments incur significant capital costs as they replace fleets of obsoleted instruments with the arrival of each new generation of wireless communication.”
According to Roessler, “The required hardware capabilities are already available from Rohde & Schwarz. Customers that invest today in our solutions do not require expensive hardware upgrades in the foreseeable future. As soon as 5G standardization picks up in related standardization bodies such as 3GPP, signal generation and analysis capabilities will be provided via simple software updates.”
And Kersey at Anritsu points out, “Regardless of the final decisions on 5G technologies, we can be sure from past experience that 5G will not replace legacy technologies. As has been the case with all new technologies from 2.5G onwards, 5G will need to co-exist and interwork seamlessly with legacy networks, and it is likely that at least some parts of the network infrastructure will be evolutions of existing components. We also know from experience that evolution of legacy networks does not stop when a new standard arrives. We can expect continued enhancement of 3G and 4G as carriers strive for returns on the investments they made in those networks.”
He added, “Even if 5G requires radically new hardware approaches in test systems, customers should still continue to see long-term returns on their investment in today’s test equipment.”
Nichols at Keysight concluded, “There is no 5G standard at this time, and we do not expect detailed 5G standards work to begin for some time—perhaps not for at least another year. Customers will make investments for measurement tools that are flexible and powerful so that they remain useful for many years to come.”
Reference
1. 5G Innovation Centre, University of Surrey.
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