Uplink training for multicell massive multiple-input-multiple-output systems: a combination of time-shifted and time-aligned pilot approaches

초록

Pilot contamination reduction can improve the achievable uplink and downlink rates in a multicell massive multiple-input-multiple-output system. To this end, this study first proposes two schemes to mitigate the effect of pilot contamination by implementing uplink training with time-aligned and time-shifted pilot transmissions. Accordingly, these techniques enable the system not only to exploit the advantages of time-shifted training but also to benefit from the use of conventional systems that improve the achievable rates. The authors introduce channel estimation in matrix form by estimating from a near minimum mean square error method. Furthermore, linear detector and precoding methods are used for a base station with a finite number of antennas in order to derive the closed-form lower bounds of the achievable rates with two uplink training schemes for both uplink and downlink transmissions. Finally, numerical results are presented to verify the analysis.

키워드