Cooperative Strategies for Inter-cell Interference Management in Dense Cellular Networks

The number of mobile devices and the amount of traffic generated by them has grown at a tremendous pace in the last years and it is expected to continue growing. This growth contrasts with the limited bandwidth that needs to be shared among users. Network densification has been proposed as a promising technique to satisfy the previous demands over a shared bandwidth. This is realized by increasing the density of base stations deployed. Although network densification can improve the signal-to-interference-plus-noise ratio (SINR) of the users located close to the serving base station, it can also increase the inter-cell interference received by other users. In current cellular networks, base stations deal with inter-cell interference by splitting the bandwidth in two parts. The first one is assigned to users with low interference (typically in the cell center) and it is reused in each cell. The second one is assigned to users with high interference (typically in the cell edge) and it is orthogonalized between users connected to different base stations. This cooperative allocation of bandwidth resources requires sharing channel state information (CSI) through a backhaul link. However, when orthogonalizing resources, the amount of resources that each user receives decreases with the number of users. Furthermore, the operating costs of maintaining a backhaul link for CSI sharing and the amount of CSI that needs to be exchanged between base stations and users makes such interference management techniques infeasible to be implemented in dense networks. These constraints urgently call for cooperative techniques that can reuse resources, while keeping the exchange of CSI between base stations to a minimum. The proximity of base stations and users in dense networks results in finding strong overhearing links between nodes that have no intentional communication, such as between users and interfering base stations or between different base stations. These overhearing capabilities of the network can be exploited to deal with inter-cell interference while reducing the CSI exchange and reusing resources. The proposed strategies are able to show the performance gains and trade-offs that can be achieved by using the overheard information in an altruistic way.