Prerequisites & Notation

Before You Begin

This chapter reverses the role of sensing in ISAC: instead of using the waveform to accomplish sensing as a byproduct (as in Ch. 13), we use the sensing output to improve the comms link. The sensed target positions and velocities are not the end product — they are a short-horizon forecast of the propagation channel, and using them turns channel estimation from a backward-looking problem into a forward-looking one. The prerequisites are OTFS channel estimation, joint beamforming, and classical estimation theory.

  • OTFS embedded-pilot channel estimation(Review OTFS Ch. 7)

    Self-check: Can you explain how DD-domain pilots estimate path delays and Dopplers?

  • OTFS-ISAC joint estimation-detection(Review OTFS Ch. 12)

    Self-check: Do you know how joint processing recovers both Θ\Theta and x\mathbf{x}?

  • MIMO-OTFS-ISAC beamforming(Review OTFS Ch. 13)

    Self-check: Can you state the covariance-based joint beamforming problem?

  • Extended Kalman filtering(Review OTFS Ch. 13 §4)

    Self-check: Are you familiar with EKF for tracking on the DD-angle grid?

  • Channel coherence and Doppler(Review Telecom Ch. 6)

    Self-check: Do you recall coherence time and its relation to maximum Doppler?

Notation for This Chapter

Symbols introduced or specialized in this chapter.

SymbolMeaningIntroduced
Θ^(t)\hat{\Theta}^{(t)}Estimated target scene at frame tts01
h^(t+1)\hat{\mathbf{h}}^{(t+1)}Predicted channel at frame t+1t+1 given sensing at tts02
ηpilot\eta_{\text{pilot}}Pilot overhead fraction (percent of resources used for pilots)s03
TpredT_{\text{pred}}Prediction horizon (frames or ms)s02
Bsense,Bcomms\mathcal{B}_{\text{sense}}, \mathcal{B}_{\text{comms}}Sensing and comms beam sets (mmWave beam codebook)s04
ρpred\rho_{\text{pred}}Prediction correlation between sensed state and channels02
← Ch 13The Sensing-Assisted Communication Paradigm