Well you have asked a rather brod question and ppl can answer it based on their experience.
There are tools that are track issues connected to Mobile station. like. Both i and ii use the UL and DL Signalling events and commands to teack as to what happed to the specific call or handset in idle mode when some issue was experianced
Based on Handset softwares.
Pocket TEMS, NIMO Handheld, Test, NetMon etc.
Tools teaking with secondary equipment help.
TREMS, Agilent, NIMO being the commonly used ones.
Some more advanced tools use probe based solutions that are connected to the Vendor Equipment BTS , BSC, Links ” ABis or Ater”
ASTELLIA, CommProve solutions.
Then there are further tools used for iteration / frequency planning.
Asset, OPTIMI etc.
Stats Reporting tools like Metrica etc.
Then there are tools that are vendor specific and vendor supplied that rely on the raw counters pegged at the BSC. e.g RNO , NPA for Alcatel, MARS for Motorola etc.