2.11. Wireless Principles

💡 First Principle: Wireless networking uses radio frequency (RF) signals that pass through walls but are affected by distance, interference, and obstacles. Unlike wired networks where each port is isolated, wireless is a shared medium where all devices in range compete for the same spectrum. Think of it like a room full of people talking—the more people, the harder it is to hear anyone clearly.

What happens without proper RF planning: Imagine two conference rooms with APs both set to channel 1. Users in both rooms experience slow speeds, dropped connections, and complaints about "bad WiFi." The APs are stepping on each other's transmissions. Switching one AP to channel 6 or 11 immediately fixes the problem. RF channel planning isn't optional—it's essential.

Consider this real-world issue: Users report that WiFi works fine in the morning but slows to a crawl at lunch. Investigation reveals the AP is near the break room microwave. Microwaves operate at 2.4 GHz—exactly where WiFi lives. Every time someone heats their lunch, they're jamming the wireless network. Understanding interference sources helps you predict and prevent these problems.

The exam tests: Channel selection (especially 1, 6, 11 for 2.4 GHz), signal strength concepts (RSSI, SNR), and why AP placement matters. You don't need to be an RF engineer, but you need to understand these principles.