【資料名稱】：Beamforming for MIMO-OFDM Wireless

【資料作者】：Sun xiantao

【資料日期】：2010

【資料語言】：英文

【資料格式】：PDF

【資料目錄和簡介】：

MIMO-OFDM is considered a very promising solution for present and future
wireless communications because of its proven bandwidth e±ciency and diversity
and multiplexing bene¯ts. Beamforming is one approach to achieve these bene¯ts.
In this work, we study beamforming in two contexts: quantized feedback beamform-
ing and beamforming in the presence of interference.

We ¯rst study quantized feedback beamforming and compare three di®er-
ent quantized feedback schemes for a MIMO-OFDM system. Their performance
is evaluated in terms of average error probability or packet error rate degradation
and overhead. We consider di®erent types of Doppler spectra, di®erent values of
delay spread, and di®erent power allocation schemes, and we assess the bene¯ts and
restrictions of beamforming in these di®erent scenarios.

A MIMO-OFDM system may su®er serious degradation in environments with
high delay spread. In order to study this degradation, we ¯rst characterize the
intercarrier interference and intersymbol interference using a per-tone processing
model. Then a new ICI/ISI-aware beamforming scheme is proposed for use in a
MIMO diversity system. We also propose suboptimal but e±cient beamforming
algorithms to achieve the beamforming gain while mitigating the interference.
In order to further improve throughput performance, an enhanced ICI/ISI-
aware beamforming with a spatial multiplexing capability is proposed. Two schemes
are studied. The ¯rst one iteratively optimizes the steering vectors to minimize the
total mean square error of the estimation. The second one attempts to minimize the
interference leakage and results in a closed-form solution with reduced complexity.