Using multiple co-channel femtocells as relays to increase the performance of the outdoor user

The deployment of femtocells comes as a solution to increase indoor coverage although it may also increase the interference level in the network. In this paper we evaluate the use of multiple co-channel femtocells as relays to the outdoor user in a cognitive radio context, where the outdoor user can be seen as a primary user and the indoor users are seen as secondary users. We show that multiple co-channel femtocells, besides allowing several secondary users to access the spectrum, may considerably increase the performance of the primary user if the femtocells act as relays to the primary signal. Moreover, results show that with the increase of the number of cooperative co-channel femtocells the capacity constraints on the backhaul can be relaxed.