After reading the whole thread Location by triangulation i came to conclusion that 2nd generation gateways which allow TDoA for localization in indoor are available but with additional costs to decrypt the metadata. So, a cost effective solution would be RF fingerprinting and implement machine learning technique in application server to compute the position in real time. Since, its just a proposal so, it would be great if anyone could contribute to this thread.
I am interested to know if i could use https://www.thethingsnetwork.org/ or should use https://github.com/brocaar/loraserver
for my application development.
If anyone who did something like this could share her/his experience it would be great.