Pilot sequence design for multi-cell distributed MIMO systems with large-scale CSI

When non-orthogonal pilots are used in multi-cell systems, channel estimation would be corrupted by inter-cell interference. To tackle this problem, the design of pilot sequences for multi-cell distributed multiple-input multiple-output (MIMO) systems is addressed in this paper. We explore this issue by introducing discriminatory treatment of different channel parameters. Generally, the large-scale channel state information (CSI) is predictable and could be regarded as priori information in pilot design, due to its slowly-varying characteristics. In particular, by assuming the large-scale CSI is known a priori, we derive a lower bound on the achievable sum rate in the downlink with a linear detector at the mobile terminal (MT), taking both intercell interference and channel estimation error into account. The problem of pilot sequence design is first formulated, of which the target is to maximize the lower bound of the achievable sum rate with a total pilot power constraint for each cell. Afterwards, we solve the problem by introducing the iterative concave-convex procedure (CCCP) with the demonstration of its convergence. Simulation results illustrate the validity and superiority of the proposed pilot design scheme.