From Silicon To Software

 

5G SoC Design: Why You Need Fast, Thorough Chip-Level Testing

5g soc designBy Varun Agrawal, Senior Staff Product Marketing Manager, Synopsys Verification Hardware Solutions

5G, the next generation of wireless communications, is delivering bigger and better transformations thanks to its speed (10-20 Gbps peak data rates), latency (<0.5ms ultra-low fronthaul), and coverage density (million+ devices/km2). In our already well-connected world, this means faster and better-performing video streaming, online gaming, autonomous vehicle functions, robotic manufacturing equipment, and an array of other applications that rely on massive amounts of data throughput.

The increasing number of devices and systems connecting to 5G networks puts pressure on the infrastructure to deliver the fastest data rates at the lowest latency possible for seamless user experiences. This, in turn, creates pressure on device and systems manufacturers and chip vendors to accommodate traffic patterns that previously were uncommon. Since these devices and systems include safety-critical things like self-driving cars and medical equipment, high reliability and high quality of service (QoS) are essential.

Four new technologies have emerged to support the demands on 5G networks and applications:

  • Millimeter waves
  • Beamforming
  • Massive multiple-input and multiple-output (MIMO)
  • Small cell

Validating all of these technologies together presents a huge challenge. In this blog post, I’ll discuss what’s needed to perform end-to-end testing effectively and efficiently for 5G Open Radio Access Network (O-RAN) system on chips (SoCs). You can also learn more by watching the on-demand webinar, “What’s Needed to Perform End-to-End Testing for 5G Open Radio Access Network SoCs.”

Four New 5G Technologies

First, let’s go over the four new 5G technologies. The frequency spectrum for 5G New Radio (NR) is wider and subdivided into two frequency bands, FR1 (below 6 GHz) and FR2 (24-54 GHz) to accommodate multi-gigabit throughput. Most operators around the world have implemented FR1. When more throughput is needed, higher frequencies must be used, so most of these operators have also expanded, or have plans to expand, on the FR2 spectrum. FR2 frequencies are millimeter waves (24 GHz and beyond).

Millimeter waves have limited range and cannot penetrate dense materials, such as concrete walls and cars. A new concept has come about with 5G to address these limitations: beam steering and beam switching, both of which are capable due to beamforming. Beamforming involves using multiple radiating elements that combine to create a single antenna with a stronger and more targeted signal. As more radiating elements are combined, the resulting beam becomes more focused and stronger, while the resulting parasite signals weaken.

Beamforming, in turn, relies on massive MIMO, which involves deployments of radio units with hundreds of antennas that can form and steer the signal to increase the signal-to-noise (SNR) ratio without increasing spectrum usage. The fourth new 5G technology on our list is small cell, which are indoor or outdoor extensions of the 5G network that service small areas with a high density of users, providing relatively low RF power output, size, and range.

In a 5G network, different functions are assigned to different entities. Whether the ultimate objective is high throughput or low latency, and depending on the desired user density and transport network performance, chip designers pursue a particular functional split to provide the right balance between QoS and implementation price.

Promoting an open, intelligent, virtualized, and fully interoperable radio access network (RAN) is the O-RAN Alliance. Its standards are geared toward enabling “a more competitive and vibrant RAN supplier ecosystem with faster innovation.” For 5G, the Alliance supports the radio unit handling the lower PHY and RF functions as well as being in charge of complex operations, such as IQ decompression, precoding, or beamforming to improve performance and increase spectral efficiency. The standards are opening the doors to new market entrants with products for network operators, which means that ensuring interoperability is essential.

What’s Your 5G Design Testing Strategy?

Radio unit SoCs for 5G should support all four of the new technologies discussed, which makes validating these chips all the more challenging. Unlike the typical internet structure, in 5G implementations, link synchronicity is a requirement as data is sent through uplink and downlink carriers. What’s the best way to test the SoC design with real-life traffic? How can the blocks in the SoC that manage complex operations be simulated? And all in an expedient manner while conforming to O-RAN Alliance standards?

This is where a testing strategy with the proper testing tools can help. One option is a physical tester, a large, expensive box with a backplane and multiple internet ports that generate traffic to test the bandwidth of each port, providing real-time analysis. Testers need to be able to run different scenarios and different payloads. However, when a bug is found in silicon, it’s difficult to fix because the tester doesn’t pinpoint its exact location. Say a request is sent for a video, but the video comes back distorted. Could it be at the software layer, where the video is reconstructed, or is it due to an issue while the SoC is buffering content before transferring the video? Even if you are able to determine the spot, you’d still need to embark on a silicon revalidation process. And you might be facing multiple bugs in a given design.

With the complexity of 5G radio units, new test capabilities are needed to identify communication bottlenecks. Given the modular nature of the distribution unit and radio unit architecture, along with the variety of functional splits, system testing should be implemented early. Open protocols require additional compliance, interoperability, and performance verification. For faster time-to-market, an ideal scenario would maintain continuity between the pre- and post-silicon validation environments.

The industry is moving to test at the pre-chip level. In addition to ensuring that the chips will perform as expected, another goal is to lower the risk of chip re-spins, a costly and time-consuming endeavor. By simulating real-life scenarios and pinpointing design issues, pre-silicon testing can also help accelerate time-to-market.

First 5G O-RAN Virtual Verification Solution

To address these 5G system verification challenges, Synopsys and Keysight, a member of the O-RAN Alliance, have teamed up to create the industry’s first 5G O-RAN virtual verification solution. The solution, for O-RAN fronthaul 7.2 radio unit ASIC design verification, offers maximal test coverage of O-RAN downlink/uplink workflows and O-RU processing blocks. It also conducts detailed design verification of the Ethernet transport sub-system with nanosecond performance analysis. On the Keysight side, its 5G testing suite validates 5G radio unit chips in the design stage, with a focus on analog-to-digital conversion; tests IQ decompression, pre-coding, and digital beamforming; generates complex industry-compliant scenarios in minutes; supports simultaneous downlink/uplink traffic; and provides strong results analysis for debugging. Synopsys brings to the solution its powerful ZeBu® Server emulation system for pre-silicon testing. Compared to competitive offerings, ZeBu Servers delivers more than 2x the emulation performance for SoC verification and software bring-up.

5G SoC verification virtual testing

With the Synopsys 5G-ORAN virtual verification solution, designers can benefit from the continuity of applying the insights gleaned in the pre-silicon setup, well before the register-transfer level (RTL) is frozen, to use in post-silicon stage testing. The end-to-end flow eliminates the inefficiencies of working with disjointed tools, while preserving the data integrity and creating an exact modulation of the RF signal to be tested. Emulators like the ZeBu Server systems can shorten the time-to-results from months down to days.

“Together, Keysight and Synopsys offer a solution that lowers the risk of chip re-spins, accelerates time-to-market, and delivers excellent ROI,” said Razvan Arhip, product manager, 5G & Networking Pre-silicon Test Solutions at Keysight. “With the ability to accurately test their 5G SoCs early in design cycles and use the same test cases to validate throughout the chip development lifecycle, users can get high-performing 5G chips to market faster to advance innovations that bring more robust connectivity.”

Summary

As of early 2021, roughly one-third of the world’s countries had access to 5G. With the super-fast networks continuing their global 5G rollout, the technology promises to transform the way we live, work, and play with its robust connectivity. Ensuring that the underlying chips in the 5G infrastructure will meet performance demands requires thorough testing. With their 5G O-RAN virtual verification solution, Synopsys and Keysight are accelerating pre-silicon verification of 5G systems and radio units, helping chip designers achieve the promises of the latest generation of wireless connectivity.

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