As 5G eRedCap devices prepare for mass market deployment, module makers and device vendors face a critical architectural decision that will impact their competitiveness for years to come. The choice between traditional Frequency Division Duplex (FDD) and Half-Duplex FDD (HD-FDD) isn’t just technical—it’s a business decision with measurable cost and performance implications that scale dramatically as IoT volumes grow.
This choice can result in a $4–$5 per-device cost difference for global deployment scenarios, while also affecting power efficiency, signal quality, module dimensions, and design size and complexity. For product managers dealing with cost pressures and with performance requirements, understanding these trade-offs is crucial.
What LTE-M and NB-IoT Can Teach Us About HD-FDD
This isn’t the first time the industry has faced such a decision. When the 3GPP introduced LTE-M and NB-IoT in Release 13, vendors could choose between FDD and HD-FDD architectures. The outcome was clear: HD-FDD became the dominant implementation, driven by cost, power, and integration advantages.
The $4–$5 Cost Penalty: Where FDD Expenses Add Up
FDD systems require duplexers—band-specific components that isolate transmit and receive frequencies. For global devices supporting 15+ bands across US, Europe, and Asia, this quickly scales:
- Regional single-carrier: +$1.5 per unit
- Multi-carrier: +$2 per unit
- Global SKU: +$4–$5 per unit
Beyond the duplexers themselves, FDD architecture requires additional RF switches as another BOM element, adding both cost and module area. Moreover, the addition of duplexers and switches increase signal loss, affecting both the transmitter path, requiring PA to transmit at higher power, and the receiver path, degrading signal-to-noise ratio, hence reducing cell coverage.
HD-FDD avoids these issues entirely by ensuring only the transmitter or the receiver is active at any point in time, eliminating the need for costly SAW duplexers. This approach also requires fewer switches since there’s no need for separate RF paths per band (which FDD requires due to band-specific duplexers).
HD-FDD Enables Global Scalability
By avoiding band-specific components (like duplexers) HD-FDD allows a single device to serve the global market, resulting in clear and meaningful cost reduction and development efficiency for product makers.
HD-FDD Improves Power, Coverage, and Signal Quality
- Power Efficiency: Up to 3x better efficiency in HD-FDD implementations compared to traditional FDD. This stems from both the TX/RX duty cycle and elimination of insertion losses on the transmitter side.
- Signal Received Quality (SNR): Removing duplexers and switches improves receiver sensitivity by 2–2.5 dB, directly enhancing signal-to-noise ratio performance.
- Coverage: HD-FDD enables coverage enhancement techniques for eRedCap that don’t exist in Cat 1bis. The improved received signal quality from eliminating RF losses directly translates to better cell coverage.
Sony’s live-network testing shows HD-FDD maintains live connections at coupling losses up to 154 dB utilizing Coverage Enhancement Mode A, significantly outperforming Cat 1bis devices, which disconnect from the network at around 145 dB MCL (Minimum Coupling Loss).
Short-Term Compatibility vs. Long-Term Efficiency
Despite HD-FDD’s proven benefits, adoption hasn’t been automatic. Many infrastructure teams default to FDD not because it’s better—but because it feels safer. It aligns with existing deployment patterns (e.g. 4G Cat 1bis), minimizes perceived friction, and avoids any potential need for infrastructure tweaks.
But that caution may come at a cost.
The shift to HD-FDD does require updated network scheduling algorithms and planning, but these software-based changes proved feasible during LTE-M deployments and NB-IoT rollouts. These updates are crucial to enable the dramatic cost saving, power reduction, and performance improvement discussed above.
For device makers, that creates a decision fork that becomes harder to reverse as eRedCap deployments scale: play it safe and lock in higher BOM costs for years, or align with the architectural path that’s already proven itself in prior IoT deployments. The risk isn’t in choosing HD-FDD—it’s in sticking with FDD until the market moves without you.
A Real-World Scenario: The Global Deployment Dilemma
Consider a global operator deploying asset trackers across logistics networks spanning urban centers with strong 5G coverage and rural areas where coverage remains sparse.
An FDD approach requires the user to choose between regional-based SKUs for limited geographical coverage or an expensive global SKU, inflating per-unit costs while still necessitating 4G fallback for coverage gaps.
Meanwhile, an HD-FDD implementation with OneSKU architecture reduces Bill Of Materials (BOM) costs significantly while enabling coverage enhancement techniques unavailable in fallback Cat 1 or Cat 1bis technologies—potentially reducing the coverage gap that created the fallback requirement in the first place.
Why This Architectural Decision Will Define Your Product’s ROI
“If you choose FDD today, your customers will pay more tomorrow,” explains Igor Tovberg, Director, Product Marketing and Strategic Partnerships at Sony Semiconductor Israel. “While HD-FDD may require upfront planning, it unlocks global flexibility, lower BOM, and better performance over the entire lifecycle.” In fact, HD-FDD enables truly global coverage across all cellular bands allocated for IoT applications in FR1 with a single hardware design.
In other words, device makers who commit to HD-FDD now can differentiate on both cost and performance as eRedCap matures. Those who default to FDD for short-term ease may find themselves boxed into expensive, region-specific SKUs that lose their edge.
What Leading eRedCap Vendors Are Doing Next
The 5G eRedCap market is at a tipping point. HD-FDD offers a rare combination of proven efficiency, lower cost, small form factor, and global scalability. The industry has already proven this approach works—LTE-M and NB-IoT’s success came directly from choosing HD-FDD over FDD alternatives.
Companies willing to make a bold, technically sound choice today will be positioned to lead tomorrow’s IoT deployments—especially as volumes ramp up and margins shrink.