Table of Contents
Properties of the Mobile Radio Propagation Channel
Statistical Description of Multipath Fading
The Mobile Radio Propagation Channel
Time Dispersion Frequency dispersion
Fading is characterised by two distinct mechanisms
Time dispersion of narrowband signal (single frequency)
Doppler shift
Doppler Spectrum
Derivation of Doppler Spectrum
Vertical Dipole
How do systems handle Doppler Spreads?
Autocorrelation of the signal
Derivation of Autocorrelation of IQ-components
For uniform angle of arrival
Relation between I and Q phase
Autocorrelation of amplitude R2 = I2 + Q2
How to handle fast multipath fading?
Frequency Dispersion
Frequency Dispersion: Delay Profile
RMS Delay Spread and Maximum delay spread
Typical Delay Spreads
Typical Delay Profiles
How do systems handle delay spreads?
Frequency and Time Dispersion
Scatter Function of a Multipath Mobile Channel
Correlation of Fading vs. Frequency Separation
Inphase and Quadrature-Phase Components
PPT Slide
Normalized Envelope Covariance
PPT Slide
Coherence Bandwidth
Effects of fading on modulated radio signals
Effects of Multipath (I)
Effects of Multipath (II)
Time Dispersion Revisited
Time Dispersion Revisited: Duration of Fades
Two-state Model
Level crossings per second
Derivation of Level Crossings per Second
Covariance matrix of (I, Q, I’, Q’)
Joint PDF of R, R’, F, F’
Level Crossings per Second
Average Fade / Nonfade Duration
Average nonfade duration
How to handle long fades when the user is stationary?
Optimal Packet length
Optimal Packet length
Derivation of Optimal Packet length
Average fade duration
Conclusion
|
