Good reply,
You're correct about a modem being non-professional equipment, there are some excellent PN Scanner/Decoders used in these system - Rohde & Schwarz TSMW, TSMU, TMSL, however a modem is representative of a customers experience.
SNR is not really used as Ec/No (Chip energy over noise) is more useful. The scanners mentioned supply a CINR figure - Carrier Interference Noise Ratio.

General testing is carried out with a user device modem/mobile and a Scanner as this is not controlled by network commands.

Si

There are plenty of expensive software solutions for this that are used at a professional level (ROMES, NEMO TEMS etc).
If you are after a free solution, the AT commands of most units Huewai, Option etc will give you network information,
For example: Signal as RSSi. (look under 3GPP TS 27.007) AT+CSQ? gives a number 0 (-113dBm or Less) to 31 (-51dBm or greater)

Failing that a lot of the dashboards have open APIs (in the UK Vodafones dashboard gives you access to lots of information)
Most of the Samsung mobiles have a diagnostic screen giving levels Scrambe Code and Cell IDs

For more info Siroda.co.uk or pm me

Si