As the smartphone industry passes its decade-long run being the most popular consumer electronics of all time, the market is beginning to see signs of maturation and slowdown. Smartphone OEMs are now competing on innovations in form factor (i.e. the move to larger and bezel-less displays), cameras (i.e. biometric sensors and computational photography) as well as Artificial Intelligence (AI) services; trading slender technological leads from one flagship launch to another. However, one area of innovation that is crucial for OEMs to keep up with is LTE radio design; especially the ever more complex RF Front End as wireless carriers continues to evolve and advance the 4G standards with features like carrier aggregation, higher order modulation and use of 4x4 MIMO (downlink) throughout their networks.
The LTE radio design of a smartphone is rarely talked about as a key selling point of a new flagship smartphone as consumers simply expects it to work better than the previous model. The RF Front End (from the antenna to the transceiver) is an ever changing design of the modern smartphone riddled with complexity. In fact, the RF Front End (RFFE) is the only section of the smartphone design that is growing in the amount area it occupies on the main printed circuit board (PCB) of modern smartphones while board space for other electronics are shrinking over time. It is exactly this complexity that is enabling the advancement of LTE wireless speeds in every new flagship design as it makes more and more efficient use of the limited LTE spectrum available to the user.
In this whitepaper, IHS Markit will explore the factors leading to the ever-increasing complexity of a LTE RFFE, which directions leading handset OEMs are going to keep up with the RFFE complexity inflation and what solutions are available to OEMs – especially the smaller ones, i.e. Tier 2 players – to keep up with competitive designs. Further, leveraging findings from recent IHS Markit teardowns, we will investigate the latest LTE Category 18 designs from four different OEMs utilizing a varied spectrum of RFFE solutions from Qualcomm. This finding is significant as this level of vertical integration represents an industry first, a RFFE solution from modem to antenna made by one component vendor. In addition we will discuss how this new approach to taming the RFFE complexity can enable smaller OEMs to compete effectively with larger OEMs with dedicated RF design capabilities leveling the playing field for a market dominated by just a few brands.
LTE = Long Term Evolution
LTE is arguably the most successful wireless standard ever purposed for mobile communications in terms of adoption. As the name implies, LTE is designed to evolve and scale over time both in speed and capacity. To do so, a critical input to enable this technology is wireless spectrums which are typically auctioned off to wireless carriers by governments. When the first LTE smartphone hit the market in late 2010, it offered clear improvements over the existing 3G standards (WCDMA & EV-DO) in terms of data throughput and latency by virtue of the new OFDMA air interface. However, these early designs could only take advantage of one slice (or band) of the available spectrum at a time just like with its preceding 3G standard. The RFFE for these early 4G LTE devices were relatively simple and on par in complexity with the existing 3G RFFEs.
It wasn’t until the introduction of LTE category 4 devices did the industry begin on the long path to evolving LTE. LTE category 4 enabled carrier aggregation (CA) which is the bonding of disparate wireless frequencies into one larger virtual data pipe so to best utilize the various spectrum holdings of a particular wireless carrier. Along with the requirement for diversity antennas, the LTE smartphones in 2013/2014 added about twice as much complexity as the first-generation LTE devices.
Soon, leading smartphone OEMs started adding more LTE band support to their flagship devices to address the diversity of LTE frequencies all over the globe and to keep regional SKUs of a particular model to a minimum. Chart 1 below illustrates the evolution of leading flagship devices over the years along with the growing number of global LTE band support as well as corresponding levels of LTE category design. Correspondingly, Chart 1 below illustrates the design evolution of leading iPhone and Android LTE RFFE designs.
The next step-function in the LTE evolution was the introduction of higher order modulation (256QAM) in Cat-11 and higher devices which pushed the max theoretical throughput of a 3x20MHz system to 600mbps or 33% faster speeds. Also, 4x4 MIMO antennas layout was implemented shortly afterward to take advantage of additional spatial layers in the mid and high LTE bands. Again, these advancements added to the overall growing complexity in the RFFE. To combat this engineering problem, RF component manufacturers modularized Front End (downlink) and transmit (uplink) chains to include frequency specific components like low-noise filters, duplexers, switches and power amplifiers. These modular parts are known as FEM or PAMs (Front-End Modules & Power Amplifier Modules for both downlink and uplink radio chains respectively) which simplified the RFFE design as well as kept the PCB footprint inflation in check. Meanwhile, OEMs had to take on the burden of becoming world class RFFE designers in order to integrate and manage the runaway complexity of their RFFEs.
Chart 3 illustrate the generational growth in complexity of the RFFE using historical Apple iPhone models as example:
In January of 2016, Qualcomm and TDK announced a joint venture to develop RFFE components and provide additional choice and solutions to the industry. Before this announcement, major merchant mobile chipset providers such as Qualcomm and MediaTek relied on RF componentry from third party firms in their reference designs and it was up to the design integrator (whether it be an ODM or OEM) to put the pieces together and come up with a working RF solution for their particular smartphone model. This joint venture was a bold move to vertically integrate the RFFE portion of the supply chain, which would cover the length of the modem to antenna path. A year later, Qualcomm purchased the remaining shares TDK owned in the JV and began putting together all the missing components in the RFFE that did not have a Qualcomm label on it. This was an unprecedented move in the industry but what Qualcomm had ultimately created was a complete modem-to-antenna system solution to address the problem of growing RFFE complexity. Qualcomm brought together its existing envelope tracking, antenna tuner products, power amplifiers in gallium arsenide and CMOS as well as switching technology through another acquisition to augment those with the assets from the JV, namely BAW, SAW and TC-SAW filters as well as module capability to create a full RFFE solution.
As LTE RFFE designs gets increasingly more complicated heading into the gigabit LTE age, only the most well-funded smartphone OEMs can afford to employ an army of RF engineers to develop proprietary RF solutions. This creates an uneven playing field and a clear need for Tier 2 OEMs to move more quickly and update their smartphone designs with new innovations in order to maintain competitive. Qualcomm’s RFFE solution answer that need by allowing these OEMs to focus on market differentiators such as display, form factor and camera innovations, bringing them to market sooner and leaving Qualcomm to solve all the RF complications of advanced LTE RF.
Teardown Results (download whitepaper for details)
Sony was the first OEM to announce that it will leverage Qualcomm’s new complete RFFE solution at Mobile World Congress 2018 for its new Xperia XZ2 flagship line.
The LG G7 ThinQ is the successor to the G6 model from 2017 which, at the time, was a LTE Cat-11 device. LG relied on Qualcomm’s RFFE expertise to help them achieve a gigabit LTE Cat-16 design for the G7 ThinQ, which represents one of the first 4x4 MIMO antenna designs coming from LG. Of note on the LG G7 design is the use of Qualcomm RF360’s RF extractor at the GPS antenna. Qualcomm has won similar design slot wins with Samsung as well as Google’s Pixel with this RFFE solution.
HTC has long been a Qualcomm design brand. In fact, one of the first LTE smartphones ever produced was the HTC Thunderbolt featuring the first-generation Qualcomm LTE thin modem (MDM9600). For the CAT-18 design of its 6-inch flagship device, HTC used a similar RFFE design as the Sony Xperia XZ2 with three QDM front-end modules and three QPM transmit or power amplifier modules. Also, like the Sony, the HTC U12+ uses two QET4100 envelope trackers for carrier aggregation on the uplink or transmit portion of the RF chain. This would, of course, increase the LTE uplink or transmit speed 2 folds by leveraging two carriers instead of one. Also, the U12+ design uses an antenna tuner part from the Qualcomm RFFE portfolio.
OnePlus, a Chinese OEM who has created a loyal customer following particularly in Europe and North America markets, sells directly to consumers – bypassing the carriers – and thus, have a larger challenge in its RFFE needs as it needs to address a wider breath of locales and LTE support. For the RF front end, OnePlus leaned on Qualcomm to provide its FEM solutions. The OnePlus 6 includes the familiar 3 QDM solutions. However, for the transmit or PA modules, OnePlus opted for a Avago solution – likely to be able to address all of the 25 global LTE bands and CA combinations it supports in the fewest module or PCB space. The upcoming “red” SKU of the OnePlus 6 is expected to use a complete Qualcomm RFFE solution akin to the Sony or HTC models described previously.
In this whitepaper, IHS Markit has highlighted the growing complexities of LTE Advanced RFFE designs and the go-to-market challenges for Tier 2 smartphone OEMs as they face ever-increasing competitive forces. By relinquishing the engineering resources otherwise occupied by updating RFFE designs, these OEMs can outsource this problem area of smartphone design to an upstream supplier such as Qualcomm in order to focus on the meaningful design innovations that will make them stand out in the smartphone market landscape. Four teardowns of production smartphones with this Qualcomm solution were discussed, highlighting the first several design wins for this new integrated modem to antenna solution.
LTE RFFE will continue to get more complex and with 5G on the horizon, the prospect of a LTE + 5G RF front end would present a more than daunting engineering problem for any capable OEM to handle. As most global 5G implementations are of a Non-Stand Alone (NSA) variety, 5G wireless carriers will require smartphones that can operate both LTE and 5G NR simultaneously. While the Sub 6 Gigahertz section of the 5G radio can share some RF components with the LTE RFFE section (i.e. antennas), the millimeter wave portion of 5G NR will undoubtable require a new set of RFFE chains to take advantage of the wider bandwidth segment of the 5G NR spectrum to achieve the multiple gigabits per second data throughput.
Qualcomm has put together a valuable and unique solution for the smartphone components ecosystem with its RFFE products. By offering a complete modem to antenna designs to the mobile electronics supply chain, many of the complications of RFFE design has been solved, allowing nimble smartphone OEMs to concentrate on and develop compelling flagship devices faster. This complete solution also creates a disruption in the RFFE components market. Existing players in the RF FE – namely Avago (Broadcom), Skyworks and Qorvo – will now likely look to partner up with modems suppliers to offer similar solutions or improve their component technology. Ultimately, competition brings choices and drives down prices. This entry by Qualcomm certainly represents the first salvo in the RFFE marketplace.
Download the full whitepaper, Taking the Complexity out of LTE Radio Front End Designs.