LDPC-Based Space–Time Coded OFDM Systems

chenpeng3361

LDPC-Based Space–Time Coded OFDM Systems Over Correlated Fading Channels: Performance
Analysis and Receiver Design
Ben Lu, Student Member, IEEE, Xiaodong Wang, Member, IEEE, and Krishna R. Narayanan, Member, IEEE
Abstract—We consider a space–time coded (STC) orthogonal
frequency-division multiplexing (OFDM) system with multiple
transmitter and receiver antennas over correlated frequencyand
time-selective fading channels. It is shown that the product
of the time-selectivity order and the frequency-selectivity order
is a key parameter to characterize the outage capacity of the
correlated fading channel. It is also observed that STCs with large
effective lengths and ideal built-in interleavers are more effective
in exploiting the natural diversity in multiple-antenna correlated
fading channels. We then propose a low-density parity-check
(LDPC)-code-based STC-OFDM system. Compared with the
conventional space–time trellis code (STTC), the LDPC-based
STC can significantly improve the system performance by exploiting
both the spatial diversity and the selective-fading diversity
in wireless channels. Compared with the recently proposed
turbo-code-based STC scheme, LDPC-based STC exhibits lower
receiver complexity and more flexible scalability.We also consider
receiver design for LDPC-based STC-OFDM systems in unknown
fast fading channels and propose a novel turbo receiver employing
a maximum a posteriori expectation-maximization (MAP-EM)
demodulator and a soft LDPC decoder, which can significantly
reduce the error floor in fast fading channels with a modest computational
complexity. With such a turbo receiver, the proposed
LDPC-based STC-OFDM system is a promising solution to highly
efficient data transmission over selective-fading mobile wireless
channels.
systems integrate the techniques of antenna array spatial diversity
and channel coding and can provide significant capacity
gains in wireless channels. However, many wireless channels
are frequency-selective in nature, for which the STC design
problem becomes a complicated issue. On the other hand, the
orthogonal frequency-division multiplexing (OFDM) technique
transforms a frequency-selective fading channel into parallel
correlated flat-fading channels. Hence, in the presence of frequency
selectivity, it is natural to consider STC in the OFDM
context. The first STC-OFDM system was proposed in [4]. In
this paper,we provide system performance analysis and receiver
design for a new STC-OFDM system over correlated frequencyand
time-selective fading channels.
We first analyze the STC-OFDM system performance in
correlated fading channels in terms of channel capacity and
pairwise error probability (PEP). In [5], information-theoretic
aspects of a two-ray propagation fading channel are studied.
More recently, in [6] and [7], the channel capacity of a multiple-
antenna system in fading channels is investigated, and in
[8] the limiting performance of a multiple-antenna system in
block-fading channels is studied, under the assumption that

ahshima

论文一篇

ahshima

thanks

zlsx

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fpga_sh

谢谢楼主提供资料

hg103

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hg103

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