5G • 5G-Advanced (Rel-18)
Ambient Continuous Wave (CW)
Continuous Wave RF Illumination for Passive Tags
Unmodulated radio frequency tone transmitted by the gNodeB to energize passive ambient tags and provide a carrier for backscatter reflection.
Technical Explanation
Passive tags require an external electromagnetic carrier to reflect. In Rel-18, base stations configure dedicated Continuous Wave (CW) or unmodulated carrier tones on unused subcarriers or guard bands. Passive tags harvest power from this tone, modulate it via impedance switching, and reflect it back to the base station receiver.
Key Functions
- Transmits dedicated pure RF carrier tones to energize nearby passive tags
- Embeds illumination tones within unused guard bands of standard 5G carriers
- Provides stable unmodulated carrier references for clean backscatter reflection
- Coordinates illumination power to comply with local RF exposure regulations
Specifications
3GPP TR 38.848 (Rel-18)
Interfaces
Uu (CW Illumination)
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