Channel estimation algorithms and their implementations
for mobile receivers are considered in this paper.
The 3GPP long term evolution (LTE) based pilot structure
is used as a benchmark in a multiple-input multiple-output
(MIMO) orthogonal frequency division multiplexing
(OFDM) receiver. The decision directed (DD) space alternating
generalized expectation-maximization (SAGE)
algorithm is used to improve the performance from that of
the pilot symbol based least-squares (LS) channel estimator.
The performance is improved with high user velocities,
where the pilot symbol density is not sufficient. Minimum
mean square error (MMSE) filtering is also used
in estimating the channel in between pilot symbols. The
pilot overhead can be reduced to a third of the LTE pilot overhead with DD channel estimation, obtaining a ten percent
increase in data throughput. Complexity reduction and
latency issues are considered in the architecture design.
The pilot based LS, MMSE and the SAGE channel estimators
are implemented with a high level synthesis tool,
synthesized with the UMC 0.18 μm CMOS technology
and the performance-complexity trade-offs are studied. The
MMSE estimator improves the performance from the simple
LS estimator with LTE pilot structure and has low power
consumption. The SAGE estimator has high power consumption
but can be used with reduced pilot density to
increase the data rate.National Science FoundationTekesElektrobitRenesas Mobile EuropeAcademy of FinlandNokia Siemens NetworksXilin
