5G • 5G-Advanced (Rel-18)
Backscatter Modulation Mechanics
RF Impedance Modulation for Cellular Uplink Data Transmission
Communicates data by rapidly altering the antenna's electrical impedance, reflecting incident base station radio waves rather than transmitting active power.
Technical Explanation
Generating an RF carrier frequency consumes significant battery power. Ambient IoT devices transmit data by backscatter modulation: an internal transistor switches the antenna impedance between reflective and absorptive states in rhythm with binary data, reflecting the gNodeB's continuous wave signal back with Phase Shift Keying (PSK) modulation.
Key Functions
- Transmits uplink data by reflecting ambient radio waves without generating an active RF carrier
- Consumes less than 1 microwatt of electrical power to modulate high-speed digital data
- Applies binary phase-shift keying (BPSK) or amplitude modulation to reflected signals
- Allows cellular base stations to receive telemetry from completely unpowered objects
Specifications
3GPP TR 38.848 (Rel-18)
Interfaces
Uu (Backscatter Link)
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