Supply decibels in the "RSSI" column, when that's all we have for an 802.11 capture?

[Guy Harris <guy () alum mit edu>]

In

        http://ask.wireshark.org/questions/18484/viewing-rssi-value-in-wireshark

somebody asks

        In Wireshark Version 1.8.2, I tried Edit -> Preferences... -> Columns -> Press "Add" button -> As "Field type" 
I choose "IEEE 802.11 RSSI" and finally I choose name "RSSI" and click on "Apply" button. The column appeared but there 
are no values in the column.

        After reading (http://ask.wireshark.org/questions/14963/how-to-get-the-field-did-unknown-4041-into-the-column), 
I compiled Wireshark Version 1.8.5 from source but still no values are appearing.

        The data was previously collected using pcap and I'm now opening it in Wireshark, how can I view the RSSI 
values ?

The problem is probably that there aren't, in the capture, values that are identified as "RSSI values".

"RSSI" isn't a term with only one definition; IEEE Std 802.11-2012 uses "RSSI" in at least two different senses, for 
example:

        Section 14.3.3.3 "RXVECTOR RSSI" clause says "The RSSI is an optional parameter that has a value of 0 to RSSI 
Max. This parameter is a measure by the PHY of the energy observed at the antenna used to receive the current PPDU. 
RSSI shall be measured between the beginning of the SFD and the end of the PLCP HEC. RSSI is intended to be used in a 
relative manner. Absolute accuracy of the RSSI reading is not specified."

        Table 6-7—ESS "Link Parameter Set" talks about "DataFrameRSSI" and "BeaconRSSI", saying "The received signal 
strength in dBm of received {Data,Beacon} frames from the network. This may be time-averaged over recent history by a 
vendor-specific smoothing function.").

Some radio information headers for 802.11 either don't have a provision for supplying "RSSI" in the sense of Section 
14.3.3.3 or do have it but also permit supplying signal strength in dB from some arbitrary reference point or dBm (dB 
from 1 milliwatt), so we cannot guarantee to be able to supply "RSSI" in the Section 14.3.3.3 sense.

Would it be useful to have the RSSI column display:

        the RSSI number, as is, if "RSSI" as a raw number, rather than as a signal strength in dB, was supplied;

        the dB number, followed by "dB", if dB from some arbitrary (unknown) reference point was supplied;

        the dB number, followed by "dBm", if dBm was supplied

so that the column shows at least *something* that Indicates the Received Signal Strength, even if it's not Section 
14.3.3.3 etc. RSSI, and indicates what's being shown (so people don't get confused if they see negative numbers or, at 
least, have "dB" or "dBm" to indicate that it's in decibels from some reference point)?
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