1. UNIT I – Wireless channels

2. TOPICS Path loss models: Free Space and Two-Ray models
Link Budget design
Parameters of mobile multipath channels
Time dispersion parameters
Coherence bandwidth
Doppler spread & Coherence time
Small Scale fading
Fading effects due to multipath time delay spread
Fading effects due to doppler spread

3. Introduction
Wireless communication – broadcasting and reception of signals by an appropriate receiver through wireless medium (air)

4. Characteristics of wireless channels
Path loss
Fading
Interference
Doppler shift

5. Path Loss
Ratio of power of the transmitted signal to the power of same signal received by reciever.
Dependent on radio frequency used and nature of terrain
Path loss models – Free space & Two ray
Free space – no attenuation of signals, only direct path
Two ray – direct path & Reflected path

6. Fading Fluctuations in signal strength when received at the receiver.
Types – (1) Fast/small scale fading (2) slow/large scale fading.
Fast fading – rapid fluctuations in amplitude, phase or multipath delays.
Slow fading – objects partially absorb the transmissions
Counter measure – Diversity & Adaptive modulation

7. Interference Types : (1) ACI (2) CCI (3) ISI Interference
Counter measure
ACI
Guard band
CCI
Usage of directional antennas, dynamic channel allocation
ISI
Adaptive equalization

8. Doppler shift
Change in frequency when transmitter and receiver are mobile in nature.
Higher frequency – when both move towards
Lower frequency – when both move away