Thermal noise is generated by the components inside the radio itself. External interference comes from other devices transmitting on the same frequency. Engineers use the to measure signal quality. If the SINR is too low, the data becomes unreadable. Solutions: Diversity and MIMO

A dedicated PDF for Chapter 4 is often hosted by academic institutions, covering modulation and demodulation foundations.

: A highly regarded complete textbook PDF (500+ pages) that builds from basic detection to MIMO and frequency diversity. MRCET Lecture Notes

Practical explanations of Phase-Locked Loops (PLL), carrier phase, and timing recovery.

[Digital Baseband] <---> [DAC / ADC] <---> [Mixer / Local Oscillator] <---> [Power Amp / LNA] <---> [Antenna] Transmitter Chain