Tell us about yourself!
Look for "algorithms based on RSSI method" - this is the only way
You can't use Arduino at all for this purpose. 1) you need hi presion osc. crystals those freq deviation will give you +/-180 m of accuracy error 2) Much higher freq, cause 8mhz - will give you 300.000.000m/s /8 000 000Hz = +/-38m of error 3) And arduino it self has problems to count amount of cpu steps.