Analysis and Design of Channel Estimation in Multicell Multiuser MIMO OFDM Systems

Abstract—This paper investigates the uplink transmission in
multicell multiuser multiple-input multiple-output (MIMO) orthogonal
frequency-division multiplexing (OFDM) systems. The
system model considers imperfect channel estimation, pilot contamination
(PC), and multicarrier and multipath channels. Analytical
expressions are first presented on the mean square
error (MSE) of two classical channel estimation algorithms [i.e.,
least squares (LS) and minimum mean square error (MMSE)]
in the presence of PC. Then, a simple H-infinity (H-inf) channel
estimation approach is proposed to have good suppression
to PC. This approach exploits the space-alternating generalized
expectation–maximization (SAGE) iterative process to decompose
the multicell multiuser MIMO (MU-MIMO) problem into a series
of single-cell single-user single-input single-output (SISO) problems,
which reduces the complexity significantly. According to
the analytic results given herein, increasing the number of pilot
subcarriers cannot mitigate PC, and a clue for suppressing PC is
obtained. It is shown from the results that the H-inf has better
suppression capability to PC than classical estimation algorithms.
Its performance is close to that of the optimal MMSE as the
length of channel impulse response (CIR) is increased. By using
the SAGE process, the performance of the H-inf does not degrade
when the number of antennas is large at the base station (BS).

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