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Wireless RF & Design
The radio side of Wi-Fi — the signal metrics, channel planning and antennas that decide whether coverage actually works.
// 2.4 GHz channel plan
241224372462 MHz
Only channels 1, 6, 11 don't overlap (each 20 MHz wide). Any other combination causes co-channel interference.
// RF concepts
| Frequency / channel | 2.4 / 5 / 6 GHz; width 20–160 MHz |
| Channel reuse | 2.4 GHz: only 1, 6, 11 non-overlapping |
| RSSI | Signal strength in dBm (closer to 0 = stronger) |
| SNR | Signal-to-noise ratio — higher is better |
| Attenuation | Signal loss through walls & distance |
| Interference | Co-channel, microwaves, Bluetooth |
// antenna types
| Omnidirectional | 360° coverage — general indoor |
| Directional (Yagi / panel) | Focused beam — point-to-point |
| Dish / parabolic | Very narrow, very long range |
// signal quality targets
| RSSI ≥ -67 dBm | Good — required for voice & smooth roaming |
| RSSI -67 to -70 | Usable for data |
| RSSI ≤ -80 dBm | Poor / unusable |
| SNR ≥ 20 dB | Minimum for reliable data |
| SNR ≥ 25 dB | Good — voice; ≥40 dB for top rates |
// dB quick math
| +3 dB | Doubles power (×2) |
| −3 dB | Halves power |
| +10 dB | ×10 power |
| +6 dB | Roughly doubles range (6 dB rule) |
// design rules
- Coverage vs capacity: more APs at lower power for density
- Run a site survey before deploying APs
- Channel bonding adds speed but uses up clean channels
- Roaming: clients hop between APs on the same SSID
- Target −67 dBm or better for voice / video