9/19/2023 0 Comments United states transmit power wifi![]() 80 MHz channels actually take a 6 dB SNR hit compared to 20 MHz, making it a challenge to use the wider channels for high density deployments (and also limited bandwidth availability). In existing frequency bands, with constant EIRP, we achieve the maximum SNR with 20 MHz channels. One of the tradeoffs in Wi-Fi and RF in general is that each time the channel bandwidth is doubled, the noise floor is also doubled (increased by 3 dB). In the US, Wi-Fi 6E low power indoor devices must comply with a spectral density of 5 dBm/MHz (there is a proposal to increase PSD to 8 dBm/MHz, which is still open as of this writing). Power Spectral Density is the amount of power over a given bandwidth. When the channel bandwidth is doubled, so is the effective power, but PSD remains constant. ![]() With 6E, we’re moving to a constant PSD, which means effective EIRP increases and decreases by 3 dB per channel width. In the Wi-Fi industry, we’re used to a constant EIRP across channel bandwidths and haven’t really had to care about PSD. Upon reading this blog, the reader should have a better understanding of PSD and how it relates to EIRP. Regulators typically set EIRP limits for Wi-Fi devices to comply with: among several other requirements, one of which is Power Spectral Density (PSD – the topic of this blog. Whatever the notation, they’re all cut from the same cloth, meaning they measure essentially the same thing, just at different parts in the RF path. ![]() Some vendors use EIRP to represent the transmit power of an access point, others use total power out and others still use per chain transmit power. Most Wi-Fi folks are familiar with and understand the concept of EIRP to represent power, although they may not know what exactly it stands for, which is Equivalent Isotropically Radiated Power (EIRP).
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