Heterogeneous cloud radio access networks (HCRANs) are potential solutions toimprove both spectral and energy efficiencies by embedding cloud computing intoheterogeneous networks (HetNets). The interference among remote radio heads(RRHs) can be suppressed with centralized cooperative processing in the baseband unit (BBU) pool, while the intertier interference between RRHs and macrobase stations (MBSs) is still challenging in H-CRANs. In this paper, tomitigate this inter-tier interference, a contract-based interferencecoordination framework is proposed, where three scheduling schemes areinvolved, and the downlink transmission interval is divided into three phasesaccordingly. The core idea of the proposed framework is that the BBU poolcovering all RRHs is selected as the principal that would offer a contract tothe MBS, and the MBS as the agent decides whether to accept the contract or notaccording to an individual rational constraint. An optimal contract design thatmaximizes the rate-based utility is derived when perfect channel stateinformation (CSI) is acquired at both principal and agent. Furthermore,contract optimization under the situation where only the partial CSI can beobtained from practical channel estimation is addressed as well. Monte Carlosimulations are provided to confirm the analysis, and simulation results showthat the proposed framework can significantly increase the transmission datarates over baselines, thus demonstrating the effectiveness of the proposedcontract-based solution.
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