Yoshihisa Okumura

Okumura began his professional career in 1950 with Nippon Telegraph and Telephone Public Corporation (NTT, now privatised), where he collected radio propagation data in the 150 to 1920 MHz bands.

Okumura's careful study in various topographical environments in metropolitan, suburban, rural and even mountainous regions at distances from 1 to 100 km was published in 1968.

[3] His 10-year survey included varying the height of the antennas from ground level to 10 meters which helps in planning radio coverage of mobile phone cell towers.

The curves he published have become known as the Okumura Model and were critical to identifying the 800 MHz band as an appropriate target for mobile phone operation.

About 1970, Okumura was promoted to the directorship of the Mobile System Research Section of the Electrical Communication Laboratory (ECL) of NTT.