OFDMA系统频率同步算法综述-Orthogonal frequency division multiple access
(OFDMA) has recently attracted vast research attention from
both academia and industry and has become part of new
emerging standards for broadband wireless access. Even
though the OFDMA concept is simple in its basic principle, the
design of a practical OFDMA system is far from being a trivial
task. Synchronization represents one of the most challenging
issues and plays a major role in the physical layer design. The
goal of this paper is to provide a comprehensive survey of the
latest results in the field of synchronization for OFDMA
systems, with tutorial objectives foremost. After quantifying
the effects of synchronization errors on the system performance,
we review some common methods to achieve timing
and frequency alignment in a downlink transmission. We then
consider the uplink case, where synchronization is made
particularly difficult by the fact that each user’s signal is
characterized by different timing and frequency errors, and the
base station has thus to estimate a relatively large number of
unknown parameters. A second difficulty is related to how the
estimated parameters must be employed to correct the uplink
timing and frequency errors. The paper concludes with a
comparison of the reviewed synchronization schemes in an
OFDMA scenario inspired by the IEEE 802.16 standard for
wireless metropolitan area networks.
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