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Currently in my training and I am covering SNR and RSSI ratings and there is a question I have.

[b]If Cisco has a RSSI range of 0-100 with 100 being the best[/b] and [b]say Atheros has a RSSI range of 0-60 and 60 being the best[/b] can I assume in thinking that a rating of 60 from Atheros is the same as a rating of 100 from Cisco. Because obviously a rating of 60 from Cisco wouldn't be very good.

I understand that the RSSI ratings are arbitrary to each vendor, but can you explain how a max rating of 60 is any different from a max rating of 100 just based on vendor.

Thanks,

No comparison. just arbitrary numbers not traceable to an established standard.

The spec has defined this parameter called RSSI, which is a measure of received signal strength. The RSSI is sent from the PHY to the MAC to indicate the signal strength of a received frame. The spec provides 8 bits (256 levels) for the RSSI value, but it does require that all bits are used, nor does it match any of these values with a minimum or maximum physical power level.

That being the case, any vendor must both arbitrarily decide what values to use in the range from 0-255, and then assign those power levels (again, arbitrarily) to actual power measurements.

Atheros may decide to use 0-60, while Cisco uses 0-100. However, 60 for Atheros may be -40 dBm, while 100 for Cisco means -25 dBm. 0 could also mean different things. For Atheros, it could be -98 dBm, while for Cisco it means -92 dBm.

In that way, the RSSI parameter is utterly non-standard across the industry.

Hopefully, RCPI (received channel power indicator) and RSNI (received signal-to-noise indicator) when they are made available will help.

You can't believe the trouble trying to convince customers that client devices with different radios measure RSSI (or signal level) differently. Trying to map other various settings from one manufacturer to the other is also difficult.

Why not just ditch RSSI or set a standard?

Infael,

Remember, RSSI [b]is[/b] part of the standard ! RCPI is part of the new standard, it just isn't available universally (yet).

Standards makers take many years to come to a consensus, and the standards sometimes take even more years to finally bear fruit.

The one I'm waiting for is 802.11r - I just won't hold my breath :-)