Software Platforms Bridge The Design/Verification Gap For 5G Communications Design

We are entering the third phase of information connectivity, one that will change the use of wireless technology dramatically. The first phase connected homes and businesses through wired telephony and the early internet via dial-up modems. Over the last few decades, the development of communication networks has been superseded by wireless mobile technology connecting people instead of places. Today, there are over 7 billion mobile devices in the world connecting over 3.8 billion people. An example of this shift from connecting places to connecting people is the demise of the desk phone. Thanks to our mobile devices and internet video connections such as Skype, the desk phone has steadily become a relic of the past. The next frontier will be to connect things. It has been well published that within the next decade we expect to connect at least 10 times the number of things as people.

This new era will usher in a host of new wireless technologies to support the internet of things (IoT) and the underlying infrastructure to be defined as the 5th generation network standards known as 5G, currently in the early conceptual phase. The promise of increased information bandwidth and faster response times (low latency) for real-time wireless control with minimal power consumption are highly attractive system goals, as shown in Figure 1. Achieving these goals will pose a significant challenge to design teams working on the enabling semiconductor technology and infrastructure that will define the physical (PHY), medium access control (MAC), and routing layers of future 5G networks. Although the technical requirements necessary to make 5G and IoT a commercial success are demanding, the economic potential and business opportunities are enormous. Thus, billions of dollars are being poured into industry and academia research.

Figure 1: 5G goals for communication speeds and response time (latency) to support wireless control called for with the industrial internet of things (IIoT) and IoT.

5G networks will likely be based on multi-radio access technology (multi-RAT) using existing cellular base stations to ensure broad coverage and high mobility and interspersed small cells for capacity and indoor service. These future networks will use a combination of small cell and macrocell base stations, as well as cellular and WiFi, with considerable research into using WiFi for cellular traffic offloading. Although there is not yet full agreement on which technology will address the 5G challenge, researchers are converging on four vectors:

• Massive multiple-input/multiple-output (MIMO) technology explores a dramatic increase in the number of antennas a base station employs for mobile device coverage, as well as high-speed backhaul links
• Network densification includes space (dense deployment of small cells to achieve greater coverage using more nodes) and spectral (utilizing larger portions of radio spectrum in diverse bands)
• 5G waveforms look to improve bandwidth utilization through structural improvements of signals and modulation techniques
• Millimeter-wave (mmWave) frequencies will exploit new spectrum (3-300 GHz) frequency ranges, once considered too exotic for commercial use, to provide very large bandwidths capable of delivering multi-Gbps data rates, as well as the opportunity for extremely dense spatial reuse to increase capacity

Every radio component, from power amplifiers (PAs), to filters, to antennas, will play a key role in realizing 5G/IoT connectivity. System performance will require that these electrical components function as mini systems with ever-increasing levels of integration and functional density. Figure 2 shows a combination of the 3rd Generation Partnership Project (3GPP) and the International Telecommunications Unit’s (ITU) 5G standards specification timeline. Phase 1 has been defined as looking at the sub-40 GHz frequency bands and with bandwidths greater than 100 MHz. However, Phase 2 includes research up to 100 GHz. Phase 2 is only 15 months, which is a very short amount of time. If researchers want to be successful during Phase 2 and have relevant work to submit for the IMT 2020 specifications, research needs to begin now.

Figure 2: 3GPP and ITU timeline for 5G standards specification.

Fortunately, advancements in microwave and signal processing technologies such as gallium nitride (GaN) transistors, new microwave monolithic integrated circuit (MMIC)/extreme MMIC devices, heterogeneous “More-than-Moore” integration, cost reductions for front-end modules/packaging, new mmWave silicon ICs, and advanced antenna integration/electronic beam steering will enable new wireless technologies standards such as 802.11ax, WiGig, and the ambitious goals being outlined for 5G. The challenges in IC and system design include the nonlinear distortion of PAs, phase noise, IQ imbalance, highly-directional antenna design, and more.

Electronics targeting 5G/IoT applications will incorporate novel materials, new semiconductor devices, interconnect technology, and circuit architectures within existing and evolving platforms such as modules and sub systems. The task of developing and integrating this new technology is easier said than done. Technology integration at this level is implemented by numerous design groups and engineering disciplines working in unison. Coordinating design activity between design groups/disciplines requires a pragmatic, top-down/bottom-up approach cognizant of overall system performance while maintaining awareness of the detailed electrical interactions between structures channeling high-frequency/speed signals within the physical design. Design trends in high-frequency component integration are steering engineers to approach electronic design differently than in the past.

The challenge for product development teams targeting 5G/IoT opportunities will be to shorten the design cycle and reduce failure through proper up-front planning, specify realistic radio-block performance, outline detailed circuit requirements, verify via electromagnetic (EM) (and possibly multi physics) simulation, and perform early prototype testing with the ability to incorporate results back into the system simulation. For organizations of any size, the top-down/bottom-up approach calls for design tool integration that includes a system-level understanding of overall performance based on data representing individual components from a range of simulation and/or measurement sources.

Managing the design project through system simulation helps guide the early development process and enables integrators to generate a link budget (accounting for losses and gains through the signal chain), define the component specifications, and monitor the overall performance. Design detail from circuit/EM simulation and/or measurement is added as it becomes available. A design platform that supports system-level data management of circuit/EM simulation and/or measurement-based results should be able to directly access this data through tool interoperability.

For the process described, research and development (R&D) teams will be able to manage the overall development project using a data flow specific to their process technology (foundries, vendors), integrating their simulation (optimization, yield analysis), physical design (layout, PDKs, design rules) and verification (electromagnetic, test) across all design software/measurement phases. The electrical design phase is best served by a unified design platform that integrates physical design (layout and process stack-up) with the following capabilities:

• High-frequency circuit – linear, steady-state nonlinear (frequency-based harmonic balance) and transient (non-steady-state time domain)
• Communication systems – behavioral component models, waveform sources, digital modulation
• EM analysis – simulates electrical behavior of 2D (planar) and 3D structures excited with high-frequency signals. Electrical interaction between radio blocks is more prevalent when they are tightly integrated into a small form factor without the benefit of distance and/or shielding to prevent performance-crippling behavior from EM coupling.
• Manufacturing analysis such as yield and corner analysis to access the impact of manufacturing tolerances
• Interoperability between physical design tools (layout), manufacturer/IC fab device models, measurement data, and multi-physics verification

NI, a leading collaborator with top industry and academic 5G researchers, offers this interoperability through its RF/microwave design software and hardware/software measurement solutions. NI AWR Design Environment is a platform that integrates the company’s Visual System Simulator (VSS) system design software, Microwave Office circuit simulation software, AXIEM planar EM simulation, Analyst 3D finite element method (FEM) EM simulation, and links to third-party EM simulators from Sonnet and ANSYS, as well as computer-aided design (CAD) tools from Cadence, Mentor Graphics, and Zuken. The platform also provides a link from simulation to prototype testing through interoperability with NI’s LabVIEW, a system-design platform and development environment that supports test instrument control, data acquisition, and industry automation (Figure 3).

Figure 3: High-frequency product development flow accelerated through shared data models and design automation using NI AWR Design Environment and LabVIEW design platforms.