When deploying a bonded 40 MHz wide channel, what is the approximate difference in the noise floor perceived by a client compared to an unbonded 20 MHz channel?

When deploying a bonded 40 MHz wide channel, what is the approximate difference in the noise floor perceived by a client compared to an unbonded 20 MHz channel?

• A. 2 dB
• B. 3 dB
• C. 8 dB
• D. 4 dB

Answer: (B)

Doubling the channel width increases the noise power the receiver has to deal with. Thermal noise scales with bandwidth, so going from 20 MHz to 40 MHz doubles the noise power. In dB, doubling power is about 3 dB, so the noise floor a client sees on a bonded 40 MHz channel is roughly 3 dB higher than on a 20 MHz channel. If the signal power stays the same per Hz, the SNR drops by about 3 dB. The other numbers don’t match the simple bandwidth-doubling effect.

Doubling the channel width increases the noise power the receiver has to deal with. Thermal noise scales with bandwidth, so going from 20 MHz to 40 MHz doubles the noise power. In dB, doubling power is about 3 dB, so the noise floor a client sees on a bonded 40 MHz channel is roughly 3 dB higher than on a 20 MHz channel. If the signal power stays the same per Hz, the SNR drops by about 3 dB. The other numbers don’t match the simple bandwidth-doubling effect.