ICI Mitigation for Pilot-Aided OFDM Mobile Systems Yasamin Mostofi, Member, IEEE and Donald C. Cox, Fellow, IEEE IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 4, NO.2, MARCH 2005. 老師：高永安 學生：蔡育修. Outline. Introduction System model Piece-Wise Linear Approximation Method I
ICI Mitigation for Pilot-Aided OFDM Mobile SystemsYasamin Mostofi, Member, IEEE and Donald C. Cox, Fellow, IEEEIEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 4, NO.2, MARCH 2005
reasons---1.near-constant channel in each frequency subband. 2.prevent ISI.
Assume perfect timing synchronizaton
The channel output y
The FFT of sequence y
An estimate of Hi,0 can then be acquired at pilot：
using them for data detection results in poor perfor-mance.
For normalized Doppler of up to 20%, linear approxi-
mation is a good estimate of channel time-variations.
We will derive the frequency domain relationship.
Therefore, we approximate
we will have
An FFT of y：
The output prefix vector
or both adjacent symbols.
T+(N/2)*Ts for the former and T for the latter.
Estimate of the slopes in region 2：
Utilizing two slopes introduces a minor change in (8).
It can be easily shown the frequency domain relationship
delay and Doppler spread at the price of higher compu-
to the average interference power.
compare it to the that of the “no mitigation” case.
Estimated channel taps are compared with a Threshold.
Let MAV represent the tap with maximum absolute value.
All the estimated taps with absolute values smaller than
MAV/γ for some γ>=1 will be zeros.
that are separated by 20μs.
ters with total delay of 36.5μs.
in the absence of
noise for both channels.
received SNR for achieving a Pb = 0.2.
estimate channel time-variations in each OFDM symbol.
received SNR to a value close to that of the case with no