Prerequisites & Notation
Before This Chapter
Chapter 18 is a research-agenda overview of topics where the RIS theory is still maturing. It assumes familiarity with the entire preceding book and wider communications theory β wideband (OFDM) signaling, information theory (capacity), and a standards-track viewpoint (3GPP, ETSI).
Notation for This Chapter
Additional notation for wideband and time-varying RIS analysis.
| Symbol | Meaning | Introduced |
|---|---|---|
| Frequency-dependent RIS phase response (complex) | ||
| Total signal bandwidth (Hz) | ||
| Number of OFDM subcarriers | ||
| Channel coherence time (s) | ||
| RIS control-loop latency (s) | ||
| Aging efficiency: fraction of ideal SNR preserved | ||
| RIS-aided channel capacity (bits/s/Hz) | ||
| Doppler frequency |