RF emitter/receiver TTL output and RSSI

I have a project and i want to check the numbers of pulses if the pulses
received are too much in short distance, and if the distance is higher
then the pulses are less. if not RF can you give some suggestions?
(distance and number of pulses received are my focus)

I read about RSSI and TDOA concepts..

so now i want to find an RF that has TTL output and i can apply the concept of RSSI/TDOA on it.