A Preference-Based Unified Criterion for Virtual MIMO Technology

Virtual MIMO (V-MIMO) is an advanced technology in uplink systems, and a well-designed user pairing scheme in V-MIMO systems can effectively exploit multi-user diversity to yield a significant performance gain. Recently, main attention has been devoted to the crucial user pairing issue with consideration of three key metrics, i.e., spectrum efficiency, energy efficiency and fairness. In this paper, we investigate the unified tradeoff among all the three metrics for V-MIMO systems with user pairing. We first formulate the three key metrics in a united form and derive a straightforward unified criterion (SUC) based on the user-specific preference to depict system performances. Through discussing several preference-based cases of the SUC, we observe that a portion of spectrum efficiency is considered redundantly. Thus, a modified unified criterion is proposed to remove the partial redundancy provided by spectrum efficiency contribution to the objective function. Based on the two unified criteria, we propose a user pairing scheme to balance the tradeoff flexibly. Simulation results show that, compared with existing user pairing schemes, the proposed scheme achieves a dynamical tradeoff among spectrum efficiency, energy efficiency and fairness.