Inside MIPI RFFE v2.1: Enabling the 5G transformation

Article By : Jim Ross & Victor Wilkerson

Updates to the standardized framework for mixing and matching components for RF front-ends will help designers create 5G products.

If there’s one safe bet about the future of smartphones, tablets, laptops, and other mobile devices, it’s this: their radio frequency (RF) front ends will be even more complex than they are today.

The latest example is 5G, which increases front-end complexity in at least two ways. First, it uses a much wider range of bands than previous cellular generations: from 600 MHz to 40 GHz, with the potential for using additional bands at even higher frequencies within the next decade.

Second, marketing is already making 5G synonymous with gigabit speeds. To deliver on that promise—or at least be noticeably faster than 4G—5G will have to aggregate not only multiple bands, but also multiple technologies, notably Wi-Fi. LTE already supports carrier aggregation, but it will be more complex with 5G when it yokes together even more bands that are more widely spaced.

One thing that doesn’t change with 5G is that consumers and business users want speed and reliability. That was the case with 3G and 4G, but 5G’s complexity makes life ever more challenging for system designers. This is particularly true considering the need to provide RF components suitable for the variety of bands required for worldwide operations under these emergent needs.

More control required

To help mitigate those challenges, the MIPI Alliance recently released the latest specification for its RF Front-End Control Interface (MIPI RFFE). Like its predecessors, MIPI RFFE v2.1 provides a common framework (Figure 1) for controlling multiple components, such as power amplifiers, low-noise amplifiers, filters, switches, power-management modules, and antenna tuners, to name a few. MIPI RFFE can be used when each function is in a separate device or when all the functions are integrated into one device, due to a point-to-multipoint architecture.

Figure 1 Example of an RFFE system configuration

By providing a common framework, MIPI RFFE v2.1 eliminates the scalability, economy, and compatibility drawbacks that plague proprietary control interfaces. For example, that commonality makes it easier to use components from multiple vendors, such as to get best-of-breed solutions or the most affordable ones.

MIPI RFFE v2.1 also gives system designers the additional control they’ll need to support multiple bands. MIPI RFFE provides a means to load configuration information ahead of time, and then to trigger it to occur at a later time. It also provides a way to assign multiple devices to a bus identification, thus addressing more than one component at a time. This allows for configuration changes to be synchronized across multiple components, if desired.

MIPI RFFE’s commonality also enables faster time to market and lower development costs because it’s easier to reuse a successful design in other products. The Internet of Things (IoT) market is notoriously price sensitive, so reduced development costs help increase the chances that those devices can be priced competitively yet profitably. These benefits are among the reasons why mobile RF front-end devices based on MIPI RFFE sell in billions of units each year.

Although MIPI RFFE is best known for its use in cellular devices, Wi-Fi products such as laptops and tablets are increasingly using the specification. This trend is partly due to another development that began over a decade ago: Wi-Fi complementing cellular and vice-versa, such as smartphones automatically switching to a wireless local area network (WLAN) to conserve the customer’s cellular data bucket.

MIPI RFFE also is increasingly common in the most mobile device of all: connected vehicles. Whether it’s Wi-Fi for passenger broadband, cellular for navigation and remote diagnostics, or dedicated short range communications (DSRC) for safety, MIPI RFFE will play an instrumental role as RF content increases in vehicles.

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Jim Ross is chair of the MIPI RFFE Working Group and Technical Director at Skyworks Solutions, Inc.

Victor Wilkerson is vice chair of the MIPI RFFE Working Group and Principal Digital Design Engineer at Qorvo US, Inc.

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