Wireless Sensor Networks (WSNs) are being considered for a wide range of applications, however, they still face various challenges, e.g. short communication range and the hidden terminal problem, to name a couple. In this paper, we build up on our previous work in [1], present a WSN prototype that demonstrates this solution, and analyze its performance in different indoor conditions by measurement and simulation. The measurement study explores radio propagation, transmission efficiency and deployment of the proposed extended-range WSN. The simulations are performed for a large scale WSN, taking into account indoor propagation, enhanced 802.15.4 PHY and MAC models and sensor application. The measurements demonstrate the feasibility and performance of the first generation extended-range 802.15.4 WSN, while the simulation study shows the network performance and scalability in terms of transmission efficiency and energy cost.