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Summary: AN EM-BASED OFDM RECEIVER FOR TIME-VARIANT C H A N N E L S
TAREQY. AL-NAFFOURI~,AHMADBAHAI',',and AROGYASWAMIPAULRAJ'
' Information Systems Lab
Electrical Engineering Department,
Stanford University, CA 94305
ABSTRACT
OFDM modulation combines the advantages of high achievable
rat- and relatively essy implementation. However, for proper
rec.overy of the input, the receiver needs accurate channel infor-
mation. In this paper, we propose an expectation-maximiaai~~
(EM) algorithm far joint channel and data recovery. The algo-
rithm makes use of the rich structure of the underlying communi-
Cation problem- a structure induced by the data and channel con-
straints. These constraints include pilots, the cyclic prefix (CP),
and the finitealphabet constraintson the data, and sparsity,finite
delay spread, and the statistical propertie9 of the channel (time
and frequencycorrelation) . Channel identification and equalisa-
tion is performed optimally and rewvery is achieved within the
same OFDM symbol wing an EM based Kalman filter.
1. INTRODUCTION
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