Chapter 9: Wi-Fi, Bluetooth & The Connected World
9.1 Wi-Fi: Your Home's Wireless Highway
Wi-Fi uses microwaves to create a local wireless network. The 2.4 GHz band has longer range but is crowded. The 5 GHz band is faster but shorter range.
| Wi-Fi Standard | Year | Frequency | Max Speed | Range |
|---|---|---|---|---|
| Wi-Fi 4 | 2009 | 2.4 & 5 GHz | 600 Mbps | ~70 m |
| Wi-Fi 5 | 2014 | 5 GHz | 3.5 Gbps | ~35 m |
| Wi-Fi 6 | 2020 | 2.4 & 5 GHz | 9.6 Gbps | ~35 m |
| Wi-Fi 7 | 2024 | 2.4, 5, 6 GHz | 46 Gbps | ~30 m |
9.2 Bluetooth: Short-Range Connections
Bluetooth uses 2.4 GHz at much lower power (~1 mW vs Wi-Fi's 100 mW), limiting range to ~10 m but making it very energy-efficient.
It uses frequency hopping — switching between 79 channels up to 1,600 times per second for interference resistance.
9.3 Cellular Networks: From 1G to 5G
| Gen | Year | Technology | Speed | Innovation |
|---|---|---|---|---|
| 1G | 1980s | Analog voice | 2.4 kbps | First mobile phones |
| 2G | 1990s | Digital voice | 64 kbps | Text messaging |
| 3G | 2000s | Mobile data | 2 Mbps | Mobile internet |
| 4G | 2010s | Broadband | 100 Mbps | Video streaming |
| 5G | 2020s | Massive IoT | 10 Gbps | Autonomous vehicles |
5G uses three frequency ranges:
- Low-band (< 1 GHz) — great range, moderate speed
- Mid-band (1–6 GHz) — balanced range and speed
- Millimeter wave (24–39 GHz) — extremely fast but short range
9.4 How Data Rides on Waves
Digital data (1s and 0s) is encoded into wave patterns through digital modulation:
- ASK (Amplitude Shift Keying): 1 = strong signal, 0 = weak signal
- FSK (Frequency Shift Keying): 1 = higher frequency, 0 = lower frequency
- PSK (Phase Shift Keying): 1 = phase shifted, 0 = not shifted
Modern systems like 256-QAM (used in Wi-Fi 6) encode 8 bits per symbol using 256 combinations of amplitude and phase!
📊 Diagram: Three rows showing the same binary data (101) encoded using ASK, FSK, and PSK modulation schemes.