Transmission
Signal Impairment
Attenuation: Loss of energy
$$dB = 10 \cdot \log_{10}\left(\frac{P_{2}}{P_{1}}\right)$$ $P_{1}$: Initial power $P_{2}$: Final power
$$dB = 20 \cdot \log_{10}\left(\frac{V_{2}}{V_{1}}\right)$$ $V_{1}$: Initial Voltage $V_{2}$: Final Voltage
Distortion
Different frequencies will be warped (in phase) differently as the signal travels. Therefore the receiver signal will be distorted.
Noise
- Thermal noise: From random movements of electrons in the conductor.
- Induced noise: Electromagnetic (motors, machines…)
- Crosstalk: Another wire affects this line
- Impule noise: lightning, thunderstorms…
Signal-to-Noise ratio
$$SNR=\frac{\text{average signal power}}{\text{average noise power}}$$
$$SNR_{dB} = 10 \cdot \log_{10}(SNR)$$
Data rate limit
Depends on three factors
- Available bandwidth
- Level of the signals we use
- Quality of the channel (noise level, SNR)