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MIPI RFFE Version 3.0: More Precise Timing for 5G Components

Aug. 27, 2020
The third iteration of MIPI Alliance’s RF front-end interface specification is here, and it brings significant technical advances for 5G designers.

Bill Wong, Electronic Design’s Senior Editor and Content Director, talks with Jim Ross, chair of the MIPI RF Front-End Control Working Group, about how MIPI RFFE v3.0 relates to the ongoing 5G global rollout.

What types of developers would especially welcome the arrival of MIPI RFFE v3.0?

Anyone doing wireless communications and connecting to the 5G network is going to be interested in this new version of MIPI RFFE. In the 2G and 3G communications eras, it was almost strictly mobile applications that were concerned with control of the radio-frequency front end (RFFE). But 5G is bringing widespread change across all wireless communications—across the Internet of Things (IoT), industrial applications, automotive applications, and so on.

In this way, RF control for all of the wireless components that undergird these varied applications is foundational to 5G rollout everywhere. MIPI RFFE already is established as the de facto industry standard for control of the RF front end, so the release of this new version benefits everyone leveraging the 5G network moving forward.

What headaches are these developers experiencing, and how does MIPI RFFE v3.0 help them?

RF front-end system architects benefit from v3.0 because it enables more flexibility by delivering precise timing control of the RF components. Time collisions of multiple RFFE command sequences create a lot of headaches for developers, and now, simultaneously, 5G is bringing about an explosion in the number of RF bands to be managed, and the reconfiguration window has narrowed.

In developing MIPI RFFE v3.0, the working group concentrated on addressing the 3GPP 5G standard where it stands today. So, the new release substantially enhances the interface’s triggering features and functionality, and it streamlines and optimizes specifically for today’s challenges.

Tell us more about MIPI RFFE’s trigger features—what are triggers, and how do they relate to the timing-control requirements of 5G?

Since its initial release, MIPI RFFE has featured triggers, which basically equip the RF subsystem to configure multiple RF devices with very tight timing control. In v3.0, the working group specified more complementary triggers for synchronizing and scheduling register-setting changes. “Timed triggers,” “mappable triggers,” and “extended triggers” in MIPI RFFE v3.0 work in combination with one another to boost throughput efficiency and reduce packet latency.

Version 3.0 brings a transformational impact on timing precision—a 20X improvement, for example, for back-to-back triggering operations. In this way, the new version of MIPI RFFE enables fast, agile, semi-automated, and comprehensive control of individual RFFE subsystems and delivers against the more challenging timing requirements presented by the Frequency Range 1 (FR1) of traditional sub-6-GHz cellular bands of 5G.

How does v3.0 change business opportunities for RF device vendors, baseband and transceiver vendors, original equipment manufacturers (OEMs), or other users?

The technical advances of RFFE v3.0 allow OEMs and device vendors to quickly migrate to 5G systems without changing the physical layer of the interface. This backward compatibility is crucial. MIPI RFFE already has a large ecosystem of adopters and devices; the interface has been implemented in billions of devices using wireless connectivity worldwide—handsets, smartwatches, automobiles, and more.

What’s next for the MIPI RFFE working group?

We are already looking at a number of ideas for the next release of the interface, such as time-stringent RF front-end control for massive MIMO (multiple input, multiple output) and the 5G NR (new radio) FR2 (Frequency Range 2) operating in millimeter-wave (24.25 to 56 GHz) bands, for example. We are always evaluating new features that the user community needs to flourish.

We are currently in the requirements-gathering phase for the next generation of the interface, so this is a great time to get involved. The working group is especially eager for more input from the system or master side of the RF industry, but we welcome contributions from anyone in the industry, anywhere in the world.

Jim Ross has contributed to the MIPI RF Front-End Control Working Group since its inception in 2008 and has served as the group’s chair since 2011.

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