Moving beyond regional SKUs can reshape mobile radio design and global user experience
Every year original equipment manufacturers (OEMs) face the daunting task of forecasting demand for multiple regional variants of the same product to fulfil market requirements. An American smartphone might carry bands 2, 4, 5, 12, 13, 25, 26, 66, and 71, while its European counterpart might support bands 1, 3, 5, 7, 8, and 20. For consumers, these geographical differences are of little consequence and only become apparent when travelling abroad when they may experience patchy coverage or slower data rates. For OEMs, however, regional fragmentation equates to higher costs, complex logistics and environmental challenges.
Why are there so many smartphone variants?
The underlying reason lies in spectrum allocation. Each country licenses frequencies differently, and operators build their respective networks accordingly. In Europe, Band 20 (800 MHz) provides wide-area rural coverage whilst Band n78 (3.5 GHz) underpins 5G capacity. In China, Band 41 (2.6 GHz TDD) and Band n79 (4.5 GHz) are prevalent in densely populated areas. The US, on the other hand, spreads its coverage across n71 (600 MHz), n77 (3.7 GHz), and n41 is heavily used by T-Mobile.
In theory, it should be possible to build a universal device that supports all these regional differences. The reality, however, is somewhat different with the RF front end being the Achilles Heel. Each band typically requires its own filter, switch, and, most critically, duplexer. When smartphones first took off, the component count was manageable as the number of commercial cellular bands was relatively small.
By 2016, however, imec research was already predicting the need for tunable duplexers. Today’s smartphones can include twenty-plus duplexers, and future devices may need 50 or more. Without reconfigurable components, the RF front end becomes too bulky, too costly, and too power-hungry for a universal device.
As a result, ODMs must produce multiple model variants to match local frequency requirements. Not only does this drive up manufacturing costs, it creates logistical and environmental hurdles that ripple through the entire supply chain.
The true cost of SKU fragmentation
The implications of SKU fragmentation caused by these regional differences go far beyond production. For consumers, roaming experiences often fall short of expectations, and advanced features such as VoLTE can become unreliable. Operators also feel the pinch as their hefty spectrum investments go underutilised, whilst certification requirements multiply with every additional SKU. OEMs, however, carry the heaviest burden: fragmented supply chains limit flexibility, unsold stock cannot be shifted across regions, and trade-in or refurbishment values drop sharply. What begins as a technical constraint in the RF front end ultimately cascades into a costly, inefficient, and unsustainable business model across the entire manufacturing ecosystem.
The industry vision: One global device
The long-term ambition is clear: a single, universal SKU that can dynamically adapt to all 3GPP-defined low- and mid-band frequencies. For consumers, this would eliminate roaming issues and ensure advanced features work seamlessly worldwide. Operators could maximise the return on their spectrum investments, and OEMs could finally overcome the inefficiencies of SKU fragmentation, streamlining production, reducing waste, and enabling global refurbishment programs. A universal SKU is more than an engineering breakthrough, it represents a vision for a smarter, more sustainable, and truly global mobile industry.
The tunability challenge over the years
The missing link to the global device dilemma has been the lack of tunability in the RF front end, particularly duplexers. Over the past 10 years, academia and industry have chipped away at this problem.
- June 2017: Ericsson, together with Lund University, published “Two Tunable Frequency Duplexer Architectures for Cellular Transceivers.” They proposed duplexer designs that combine filtering and cancellation, but struggled with selectivity versus loss.
- 2018: The University of Bristol demonstrated cancellation-based duplexers with strong performance but complex calibration.
- 2021: Dakotah Simpson (University of Colorado Boulder) and collaborators produced highly selective, tunable, balanced bandpass filters using mixed technology resonators, but integration remained a barrier
- Other frontier work: There is also emerging research in transformer-based or electrically balanced tunable duplexers, especially targeting mmWave bands (important for 5G/6G). Although many of these are still at proof-of-concept or lab demonstrators, they indicate what might be possible once integration, cost, and size challenges are further addressed.
Prototypes for all these approaches successfully demonstrated that tunable duplexers were technically feasible, but none were ready for mass-market deployment. The designs were often too complex to integrate efficiently into a compact smartphone RF front end, exhibited higher-than-acceptable insertion losses, or could not cover the full range of frequency bands needed for global operability. In summary, whilst the research validated the concept, the step from laboratory proof-of-concept to commercially viable, scalable devices remained out of reach.
A turning point: Software-defined RF
Momentum is now shifting, largely driven by pioneering research carried out by Dr. Leo Laughlin, whose work has demonstrated that the long-standing barriers to tunable duplexing can be overcome. Instead of relying on banks of fixed filters, his approach leverages reconfigurable architectures and advanced cancellation techniques to dynamically manage transmit and receive paths. This research is now being commercialized through Forefront RF,which is developing a software-defined RF front-end that uses self-interference cancellation to replace multiple fixed duplexers with a single reconfigurable block. By tuning in software, the architecture aims to reduce size, power consumption, and integration complexity.
Alongside this, other research streams are exploring MEMS-based tunable filters and adaptive cancellation loops. Together, these efforts show that the gap between laboratory prototypes and manufacturable solutions is finally beginning to close.
For OEMs, the challenge of managing multiple SKUs is more than just an engineering headache — it is a strategic and financial burden. A single, globally adaptable device could transform this status quo.
Illustrative estimates for OEMs shipping 10M and 100M devices annually:
| Category | Impact at 10M Units | Impact at 100M Units |
| Logistics & Forecasting Efficiency (20–30% lower overhead) | $20–30M savings | $200–300M savings |
| Component & Manufacturing Savings ($0.50–$1.00 per device) | $5–10M savings | $50–100M savings |
| Reduced Scrapping (1–2% of production) | $50–100M saved | $500M–1B saved |
| Refurbishment & Resale Uplift | Tens of millions in added lifecycle value | Billions in added lifecycle value |
A universal future
The smartphone industry has long promised global connectivity, and the vision of a truly global device is finally within reach. By rethinking the RF front end with reconfigurable duplexers and filters, the industry can break free from the limitations of regional SKUs. This shift does more than simplify RF design; it has the potential to transform the economics, logistics, and sustainability of the entire mobile ecosystem. The next generation of smartphones can — and should — work everywhere, finally delivering a truly global device that no longer needs a passport.
