Page 338 - Kaleidoscope Academic Conference Proceedings 2024

2024 ITU Kaleidoscope Academic Conference

interleaver. The interleaved bits are then mapped to 256- adapted to (255, 239) RS codes. Generally, the code rate of
QAM symbols. We use QAM to increase the spectral the RS code is above 0.8. Here the RS codes have 239
efficiency of our system. The 256 QAM symbols are information symbols and 16 parity symbols.

1

LDPC Interleaver S/P …

QAM mapped Reed
Solomon alphabets

Figure 3. Bit interleaved precoded RS codes.

proposed scheme. Hence, along with being spectrally
Thus, the code’s spectral efficiency is about 0.93, and this efficient, the proposed method is energy efficient as well.
code could be better adapted to the bandwidth-limited
channel. Usually, a symbol with 8 bits is widely used in
8
computers or other fields and 2 is a coefficient commonly

used in ℱ(2 ) Thus, it becomes convenient for the
hardware implementation and experimental validation with
a symbol of 8 bits.

Spectral efficiency of the proposed scheme – We calculate
the spectral efficiency of the proposed scheme as

= 2 log ( ) ( /2 ) (20)
2

where = 956, = 1912, = 239 = 255. We get

= 7.37 /2 with the proposed scheme.
Figure 4. High Fading Regime
4. RESULTS AND DISCUSSIONS

We now simulate the technique proposed in Section 3 and
compare the performance with that of the LDPC-coded
scheme, i.e., without BICM precoding. We show the results
obtained in terms of BER vs. E b /N o in Figs. 4 - 5 for two
levels of fading. The high fading and moderate fading is
modeled using Eq. 2. We vary the value of and used in
Eq. 2 from 4.2 to 4.0 and 1.6 to 1.9, respectively to model
the effects of high fading and moderate fading in this work.
For both the results, the simulations are carried out at the
end user data rate of 1 Gbps.

-4
For reporting E b /N o gain, we fix the target BER as 10 and
the comparative scheme as the LDPC coded scheme. In
both fading regimes (Figs. 4 and 5), the BICM precoded Figure 5. Moderate Fading Regime
RS-coded system performs better than conventional LDPC
schemes. In a high fading regime, a coding gain of 13.3 dB 5. CONCLUSIONS
is obtained over a target BER, whereas the gain in the
moderate fading regime is 15 dB. This shows that we can This paper proposes a novel approach to overcoming the
save more than 50 % of transmitted power using the Eb/No penalty incurred due to the fading channel in an

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