Abstract:
Massive MIMO (Ma-MIMO) is one of the basic enabler technologies for 5G wireless com-munication networks to provide higher spectral efficiency (SE) by using large number of
antennas and serves many users simultaneously in the same frequency–time resources. In
a Ma-MIMO downlink (DL) system, the base station (BS) estimates the channel using
uplink (UL) training but a pilot contamination (PC) is the major challenge in multi-cell
Ma-MIMO system. This challenge causes severe inter-cell Interference at the home cell
and then limits the performance of the system. Precoding techniques with pilot reuse
factor(PRF) are used to mitigate the PC effect. The performance of DL multicell Ma-MIMO system is analayzed under spatial correleted Rayleigh fading channel with both
perfect and imperfect channel state information (CSI). Precoding is used to mitigate
the intra-cell interferences and PRF reduces the PC effect by assigning orthogonal pi-lots to neighboring cells. SE performance of multi cell Ma-MIMO system is analyzed
with maximum ratio transmitter (MRT), zero forcing (ZF )and minimum mean square
error(MMSE) precoding techniques and combined with PRF. Performance comparison
of precoding techniques showed that MMSE provides the best SE performance for both
CSI and it has highest SE at PRF of four among all when the number of antennas are
changed. When both the number of users and antennas are increased simultaneously
and M >> K, the SE is improved by more than 25% and also system performance with
perfect CSI is better than imperfect CSI.
Key Words: CSI, Ma-MIMO, PRF, PC, Precoding