IMS 2017 Main Course: 5G!
Q: With the onset of the fifth-generation of mobile networks, what are your biggest concerns, and what do you foresee being the biggest challenges designers will face from an implementation standpoint?
By Ralf Stoffels, Senior Director, Product Marketing, Advantest
There’s no doubt that the transition to fifth-generation (5G) networks is coming; this was a key consensus at Mobile World Congress 2017. In fact, according to Intel, 5G is already here, and it’s just a matter of time until products are widely available. By most estimates, the full transition to 5G is still not expected until two to three years from now – most likely, in mid-2020.
The 5G standard promises new levels of speed and capacity for mobile/wireless communications with lower latency and greater flexibility than current 3G or 4G/LTE technologies. However, its new encoding technologies and chip structures will bring fresh challenges for design, test and manufacturing. Designers and makers of RF and mixed-signal chips used in mobile products that communicate on these new high-speed networks need to know that 5G ICs will be testable using technology that’s already available, rather than requiring cumbersome and costly development of new solutions that target next-generation standards. Older test-card architectures are based on technology that uses shared subsystem stimuli resources, which means that ICs have to be tested in slow, costly series fashion.
One approach is to utilize advanced test cards on a platform that can accommodate a wide range of devices. For example, some test cards are designed to boost parallelism, throughput, and cost savings. Scalable and adaptable for both current and future (i.e., 5G) devices, the cards can help eliminate at least one major headache associated with the emerging 5G era.
Additionally, some wave scales enable coverage of both existing and emerging 5G applications like 24-, 40- or 60-GHz. While the test head and cards, are all enabled for millimeter wave applications, the RF interface module enables an easy transition from current to future 5G applications, as well as a highly integrated RF solution.
By Roger Nichols, Director of 5G Programs, Keysight Technologies, Inc.
5G is more exhilarating than it is concerning. There are opportunities all over the map for the breadth of what we do from simulation and design to characterization, validation, and compliance testing. Perhaps a concern is the high rate of industry consolidation during the midst of this generational change. 5G is a major technology upheaval across the entire wireless supply chain. In previous generational changes, the market has been characterized by more than a handful of large players in each sub-market with myriad smaller companies and startups involved in a mix of enabling the larger players and challenging them to think differently—a great recipe for innovation.
Designers face the following key issues: Living up to the hype, new technologies for wireless realm, and physical realities in a virtualized world. The 5G vision means orders of magnitude improvement in all facets of network performance. Designers must manage this with exceptional diligence to accomplish these faster, shorter, bigger, and more efficient performance factors and make it affordable. In addition, many designers of sub-6 GHz radio systems are being asked to embrace carriers from 20 up to 90 GHz. The physics and practical ramifications are new to the mainstream designers and we all have much to learn. Lastly, the vision of virtualized and flexible networks shows tremendous promise in business model, network efficiency, and flexibility. There are profound barriers that exist in the physical networks that must be overcome for the virtualized vision to become real. Designers have their work cut out for them to build hardware and software solutions to overcome these physical limitations.
By Liam Devlin, CEO, Plextek RFI
5G will enable a whole range of new communications use cases, some of which may not even emerge until the full potential of high-speed, low-latency connectivity is released. 5G standards have yet to be fully defined, but it is clear that millimeter wave (mmWave) frequencies will be used to enable the very high data rate applications. There is currently a huge amount of development effort under way to realize practical mmWave systems capable of allowing mobile devices to achieve these promised high speeds. At the moment, many different strategies and frequency bands are under investigation. We believe that the first commercial mmWave 5G systems will be in the region of 28 GHz, and the FCC is supporting this band. Frequency bands around 37 and 39 GHz are also being promoted, and it is likely that multi-band devices will eventually be required.
Cell sizes for 5G will be much smaller than for 4G, in all probability below 100m. Many base station sites will therefore be required, which could for example be located on lamp posts. This densification is required not only because of the difficulty of achieving non line-of-sight connections over longer distances at higher frequencies, but also because if every user is to receive a high data rate then there will be a limit to the number of connections each base station will be able to support. It also means that urban areas will be first to benefit from 5G.
Most mmWave 5G systems are likely to be based on phased-array antenna architectures, and we are currently involved in designing custom MMICs and packaging techniques for these prototype systems. As progress is made during 2017 in allocating international frequency bands and in defining some of the 5G standards, there will be considerable work undertaken both on proving system implementations and on developing component parts that can be supplied at the right price point in high production volumes.
By Rick Wietfeldt, Ph.D., Chairman of the MIPI Alliance Technical Steering Group and Senior Director, Technology at Qualcomm
As 5G and earlier “pre-5G” devices employ techniques from the microwave textbooks, designers of consumer devices also need to consider factors outside the conventional microwave designer’s purview.
Higher frequency operation. A key aspect of 5G is increased data rate performance to the multi-Gbps regime. While other measures of increasing performance are leveling out as designers approach the Shannon-Hartley limit (as may be represented by Gbps-per-Hz), performance may be directly gained by increased bandwidth (the “Hz”), available at the higher microwave frequencies currently imagined up to 100 GHz where more spectrum is available and/or spectrum is aggregated across multiple bands. (For reference, current cellular operation is below 3 GHz.) Both require increased modem complexity in baseband and RF designs.
Adaptive antenna steering. Cellular designs often have deployed only one primary and secondary antenna for RF diversity and recently multiple input multiple output (MIMO) operation for improved performance, whose beams may generally be directed away from the device to increase the antenna gain, such as through a hemispherical beam. However, higher frequency operation narrows beam width where it may become a narrow pencil beam in a specific direction. Here, designers borrow from the microwave community’s technique of a larger number of antennas deployed in a phased array configuration to allow adaptive antenna steering (AAS). In addition to providing broad beam coverage (and the MIMO advantages above), it also enables antenna steering to improve the sensitivity and performance in a given direction or to a given user.
Increased TX Power and Mitigation. The Friis transmission equation states more power is lost (or higher path loss) at higher frequencies, which naturally results in increased transmission power to achieve the sensitivity limit of receivers. However, to reduce transmission power, mobile operators plan to deploy a higher density of closely spaced “small cells.”
Designers must continue adhering to regulatory limits of emissions on human tissue, as quantified by the specific absorption rate (SAR), and minimize power to maximize device battery life. Sensors in each phone may determine proximity to human tissue and signal a power reduction.
By Luc Langlois, Director, Global Solutions Team, Avnet
5G promises a unifying network architecture encompassing legacy 4G, WiFi, and IoT while expanding into new millimeter-wave spectrum bands to deliver peak rates of 10+ Gbps with very low latency. The goal of nearly limitless bandwidth anywhere and anytime poses unprecedented design challenges. Starting at the air interface, gains in spectral efficiency from massive Multi-Input, Multi-Output (MIMO) antenna arrays will demand innovative antenna technology and deep expertise in multi-rate digital signal processing. Designers will face the uncertainty of new radio waveforms, implementing various candidate algorithms of emerging 3GPP radio technologies with high order modulation schemes, while the specification is evolving towards commercial deployment scheduled for 2020.
Greater path loss at higher carrier frequencies will lead to cell densification with a heterogeneous mix of Small/Micro/Macro cells, requiring extensive system-level simulation to model the effects of multi-path fading channels and RF impairments in dense urban environments. System requirements will demand support for multiple standards including GSM, WCDMA, LTE (FDD & TDD), while planning for a wide range of use-cases from low-cost, low-energy, low-data rate links to ultra-reliable critical communications.
Successful 5G product development will require diverse, multi-disciplinary engineering teams with expertise in wideband RF signal chains to meet stringent receiver sensitivity, frequency-agile RF-sampling data conversion, high-speed digital design, and secure network design.
By Ashutosh Dutta, Ph.D., IEEE 5G Initiative Co-Chair, Lead Member, Technical Staff at AT&T
Unlike its previous predecessors, 5G is going to be revolutionary as it encompasses new services, technologies, frequencies, industries, and business models. It involves “rethinking” of fundamental areas including cell architectures, antennas, core networks, end points, circuits, and systems. Types of 5G applications include enhanced Mobile Broadband, critical tactile communications, such as remote surgery, Massive Machine-Type Communications, network slicing, and autonomous driving that rely on three pillars of 5G communications, namely massive content, massive sensing, and control. The benefits promised by 5G cut across multiple layers, including software-defined networking (SDN) and network-functions virtualization (NFV). Key 5G characteristics such as massive MIMO, new transmission technologies—namely mmWave, new waveforms, and shared spectrum access will affect the lower layers of the protocol stack giving rise to new chip design and devices.
Advanced inter-node coordination, simultaneous transmission and reception, device-to-device communications, wireless backhaul, and access integration will affect the network layers of the protocol stack. At the same time, flexible networks, flexible mobility, and context aware networking will largely be driven by automation, orchestration, and SDN aspects that mostly operate at the application layer. To ensure successful implementation, it is imperative that development in each of these layers be in sync as there is significant dependency and correlation. Hence, designers would need to look at the whole ecosystem and pay attention to the development of all the layers and protocols for harmonization. Interoperability of standards and protocols developed at each of these layers would be the most important thing to watch for, as lack of interoperability would lead to a deployment nightmare. Collaborations among various standards bodies and forums is extremely essential. Designers will also need to build prototypes or simulations and test functionalities in various testbeds before real deployment.
By David Ryan, Senior Business Development and Strategic Marketing Manager, MACOM
Sub-6 GHz and millimeter wave (mmW) 5G systems will rely on phased array technology to optimize signal link and data rate, leveraging large numbers of antennae elements configured in massive Multiple Input, Multiple Output (MIMO) architectures. These arrayed antennae configurations enable the advanced beamforming capabilities that are central to the 5G value proposition—but the complexity and density of these systems pose several design and assembly challenges.
Massive MIMO systems require compact front-end solutions, given how the element-to-element spacing decreases within tightly-clustered antenna configurations, particularly at higher frequencies. This in turn creates thermal challenges associated with generating significant RF power and dissipating the heat in a small area.
Gen4 GaN is ideally suited to counter these challenges, delivering considerably higher raw power density than incumbent LDMOS technology, which enables smaller device packages optimized for use within massive MIMO antenna systems. Gen4 GaN also provides more than 10 percentage points greater efficiency than LDMOS, easing thermal constraints considerably.
Another major challenge for 5G systems is the assembly of the final unit. A 64-antennae array will host a huge number of RF components (64 PAs, 64 switches, 64 LNAs, etc.), creating significant design and manufacturing complexity, with increased risk of poor final build yield. By leveraging higher level assemblies, however, component failures can be isolated to one of 64 modular subsystems, making it far easier to rework the board compared to an assembly comprised of thousands of individual components, compromised by a single failure.
5G massive MIMO systems are therefore particularly well positioned to leverage the design and assembly strategies embodied in Multifunction Phased Array Radar (MPAR) systems. First generation MPAR systems leverage higher level RF assemblies whereby the transmit/receive modules are SMT mounted to the PCB using industry standard manufacturing processes, streamlining system assembly and minimizing yield risks, which can reduce costs dramatically.
