Based on the definition of the access network architecture and the forecast of voice and data traffic evolution, this paper derives engineering rules for radio network dimensioning of 3G femtocell-based access networks in isolated rural areas. Network dimensioning exercise focuses not only on the access network, but also on the necessary backhaul bandwidth and the required number of solar energy power supply units. Different femtocell-based deployments have been studied, whose appropriateness is related to the traffic and propagating conditions.