Two-tier Cellular Networks with Frequency Selective Surface

A key challenge is how to improve the wireless capacity of cellular networks for both outdoor and indoor users. Whilst deploying low power femtocells can significantly improve the indoor capacity, its interference can erode the outdoor capacity. In order to maximise the performance of the co-frequency two-tier network, the research challenge is how to minimise their mutual interference through coordination and other methods. This paper proposes a controllable interface that acts as a dynamic barrier between the outdoor and indoor networks. The interfaces comprises of a frequency-selective-surface (FSS) which is a band-stop filter. The paper also demonstrates that without any FSS interfaces, the mutual interference between indoor and outdoor networks erodes the capacity of each other significantly. The benefit of the FSS interface is that it is able to mitigate the mutual interference to the extent that their capacities are maximised. The results show that by deploying FSS interfaces, an improvement of up to 1.3 fold in mean throughput, 4.6 fold in throughput fairness for outdoor users and 1.2 fold in mean throughput, 2 fold in throughput fairness for indoor users can be achieved. The analysis is conducted using both a theoretical stochastic geometry analysis and multi-cell simulation results.