Rayleigh Fading

The process of convolving a synthetic signal with a time-varying channel impulse response (CIR) to replicate the destructive and constructive interference of real-world propagation environments. Rayleigh fading is a specific statistical case of this broader emulation technique, modeling the scenario where no single path is dominant.

• Key Mechanism: Convolution of the transmitted waveform with a tapped delay line.
• Application: Creating realistic training data for channel-robust fingerprinting models.
• Relationship: Rayleigh fading defines the amplitude distribution of the tap coefficients in the emulator.

A statistical model for emulating a propagation channel where a dominant line-of-sight (LOS) signal component coexists with scattered multipath components. The ratio of the power in the dominant path to the power in the scattered paths is defined by the K-factor.

• Key Distinction: When K = 0 (no LOS), the Rician distribution mathematically collapses to a Rayleigh distribution.
• Use Case: Modeling environments like a factory floor with a visible transmitter, versus a cluttered urban canyon without one.
• Parameterization: K-factor is the critical parameter for transitioning between Rician and Rayleigh regimes.

The simulated change in a signal's carrier frequency caused by relative motion between a transmitter and receiver. In a Rayleigh fading context, Doppler shift is characterized by a Doppler spectrum, such as the classic Jakes model, which defines the spectral broadening of a pure tone.

• Impact: Causes time-variant fading, where the channel coherence time is inversely proportional to the maximum Doppler frequency.
• Simulation Parameter: Maximum Doppler shift (Hz) is a primary input to the channel emulator.
• Relationship: The combination of multipath delays and Doppler shifts creates a doubly-selective fading channel.

A time-domain representation of a multipath channel's effect on a transmitted signal, used as a filter kernel to synthetically impose delay spread and fading on a clean waveform. For Rayleigh fading, the tap magnitudes of the CIR follow a Rayleigh probability density function.

• Structure: Modeled as a tapped delay line (TDL) where each tap has a specific delay, amplitude, and phase.
• Key Metric: The delay spread (e.g., RMS delay spread) quantifies the temporal dispersion of the channel.
• Implementation: The CIR is convolved with the synthetic IQ samples to produce the impaired signal.

A fundamental noise model that adds a statistically random, spectrally flat signal to a waveform to emulate the thermal noise floor of electronic components and the channel. It is a separate, additive impairment distinct from the multiplicative fading of the Rayleigh channel.

• Key Parameter: Signal-to-Noise Ratio (SNR) defines the power ratio between the signal and the AWGN.
• Statistical Property: Noise samples are independent and identically distributed (i.i.d.) with a Gaussian distribution.
• Combined Effect: A complete synthetic impairment pipeline applies AWGN after the multipath fading convolution to model the receiver's noise floor.

A parameter set defining the intensity and relative delay of multipath components in a channel model, used to configure a tapped delay line (TDL) for emulating specific environmental fading. Standardized PDPs, such as those from ITU-R or 3GPP, define profiles like 'Vehicular A' or 'Pedestrian B'.

• Configuration: Specifies the number of taps, their relative delays (ns), and average power (dB).
• Rayleigh Assumption: Each tap's amplitude is assumed to fade independently with a Rayleigh distribution.
• Purpose: Provides a repeatable, standardized test condition for evaluating fingerprinting model robustness.