IIT Kanpur has an excellent case study on experimental Rural Telephony network (RuralNet) using WLAN 802.11x
IIT- Kanpur )
OpenBTS is an open source implementation of GSM air interface (Um). Its based upon GNURadio and Astrix platforms.
There are a few patent issues involved in commercial deployment, due to the GSM patent restrictions.
Open BTS has been field tested see...
VNL are Gurgaon, NCR based starup has low cost GSM solution for rural telecom.
Dawesa Village case study...
TATA BP Solar has solution for Solar Power for rural Telecom.