Decoupled Uplink-Downlink Association in Full-Duplex Cellular Networks: A Contract-Theory Approach

We study the user association problem in full-duplex cellular networks, wherein base stations (BSs) are densely deployed with highly variable transmit powers and topologies. To enhance the system performance, decoupled UL-DL (DUDe) association is considered, which enables each user equipment (UE) to associate with different base stations in uplink (UL) and downlink (DL), respectively. For the DUDe in full-duplex communication (referred to as DFA) mode, the challenge arising due to the asymmetric information, which is private to the corresponding UEs but unknown to BSs and all the others (e.g. channel gains and intercell interferences), needs to be considered, To address this challenge, we propose a contract-theory based distributed user association approach. Specifically, the association process is modeled as a monopoly labor market, where the BSs act as employers and offer two-dimensional contracts to employees (i.e. UEs). Theoretical proof for contract feasibility is presented by providing sufficient and necessary conditions. To reach the optimality, a contract-theoretic decoupled user association algorithm is developed, in which a BS broadcasts the drafted contracts, and each UE self-selects the optimal contract by considering her own demands. Numerical results are presented to demonstrate the performance of proposed approach in terms of node utilities and social surplus.