Cryptography Reference
In-Depth Information
Figure 3.6 - Minimum distances required for 4-PSK modulation and a Gaussian
channel as a function of packet size, for some coding rates and
PER
=10
−
7
and
PER
=10
−
11
.
3.4.2 MHD required with 8-PSK modulation
Here we consider an 8-PSK modulation on a Gaussian channel implemented us-
ing the principle of the "pragmatic" approach, as presented in Figure 3.7. This
approach first involves encoding the data flow in packets to produce codewords
that are then randomly permuted by the interleaver
Π
, with a permutation law
drawn randomly. The contents of the permuted codewords are then organized
in groups of 3 bits using a Gray coding, before being modulated in 8-PSK. The
demodulator provides the received symbols from which we extract the log like-
lihood ratios (LLRs) for all the bits of the packets. Finally, inverse interleaving
and decoding complete the transmission chain.
