coding technique for OFDM, details... Need Help.

ofdm details

Hi All,

Currently I'm Working on Coded version of OFDM.(COFDM)
walking new in this field, need some Guide and reference that'd help me to follow.

i need some theoretical reference and matlab simulation for different coding.

thanks in advance.

mahmud

cofdm pommier

You could read some documents first:
1. COFDM: an overview of Zou, W.Y.; Yiyan Wu;
2. Description and features of the COFDM systems of Pommier, D.
3. CD3-OFDM: A novel demodulation scheme for fixed and mobile receivers of V. Mignone and A. Morello
4. Coded Orthogonal Frequency Division Multiplex of BERNARD LE FLOCH, MICHEL ALARD
Good luck!

Added after 4 hours 34 minutes:

Coded OFDM
By using time and frequency diversity OFDM provides a means to
transmit data in a frequency selective channel. However, it does not
suppress fading itself. Depending on their position in the frequency
domain, individual subchannels could be affected by fading. This
requires the use of channel coding to further protect transmitted data.
Among those channel coding techniques, trellis coded modulation
(TCM)45 combined with frequency and time interleaving is
considered the most effective means for a frequency selective fading
channel.
TCM combines coding and modulation to achieve high coding gain
without affecting the bandwidth of the signal. In a TCM encoder,
each symbol of n bits is mapped into a constellation of n+l bits,
using a set-partitioning rule.45 This process increases the
constellation size and effectively adds additional redundancy to
trellis-code the signal. A TCM code can be decoded with a soft
decision Viterbi decoding algorithm,46 which exploits the soft
decision nature of the received signal. The coding gain for a twodimensional
TCM code over a Gaussian channel is about 3 dB for a
bit error rate (BER) of IO-'.
It should be mentioned that one of the advantages of OFDM is that it
can convert a wideband frequency selective fading channel into a
series of narrowband and frequency non-selective fading
subchannels by using parallel and multicarrier transmission. Coding
OFDM subcarriers sequentially by using specially designed TCM
codes for frequency non-selective fading channel is the major reason
for using COFDM for terrestrial broadcasting. However, the
searching of the best TCM code is still on going.
Although trellis codes produce improvements in the signal-to-noise
ratio ( S N ) , they do not perform well with impulsive or burst noise.
Besides electromechanical sources of burst noise, burst noise is also
caused by NTSC co-channel interference and phase noise which can
cause data-dependent crosstalk. In general, transmission errors have
a strong time/frequency correlation. Interleaving plays an essential
role in channel coding by providing diversity in the time domain.
Interleaving breaks the correlation and enables the decoder to
eliminate or reduce local fading throughout the band and over the
whole depth of the time interleaving. Interleaving depth should be
large enough to break long straight errors.

details about ofdm

Thanks a lot,

exactly what i wanted. looking for those paper's.
i'll let u know.

again thanks.

mahmud

use of channel coding in ofdm

mahmud_dbm said:

Thanks a lot,

exactly what i wanted. looking for those paper's.
i'll let u know.

again thanks.

mahmud

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