QoS-Guaranteed User Scheduling and Pilot Assignment for Large-Scale MIMO-OFDM Systems.

The combination of the large-scale multiple-input–multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM) transmissions is a promising candidate for future wireless communication systems. We investigate a quality of service (QoS) guaranteed user-scheduling algorithm for large-scale MIMO-OFDM systems, where pilots are assigned to served users. In general, a wireless channel concentrates its energy on a specific region in the angle and delay domains. We suggest to reuse pilots based on this channel property in a macrocellular environment, thus reducing pilot overhead significantly. In the presence of contamination caused by the pilot reuse, we analyze the asymptotic behavior and design an interference cancelation (IC) precoder. For both the simple matched filter (MF) precoder and the sophisticated IC precoder, we derive achievable rates under pilot contamination, which are metrics for QoS. Further, according to the analysis under a special case, the number of QoS-guaranteed users proves to be maximized when an equispaced property in the angle domain is satisfied. The theoretical result facilitates a low-complexity user-scheduling algorithm. Numerical results confirm our analysis and proposed pilot scheme, and they show that the proposed scheduling algorithm can select out the maximum served users with guaranteed QoS. [ABSTRACT FROM AUTHOR]