<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Methodology of FPGA Implementation and Performance Evaluation of Polar Coding for 5G Communications</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Juliy Boiko</string-name>
          <email>boiko_julius@ukr.net</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Volodymyr Druzhynin</string-name>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Serhii Buchyk</string-name>
          <email>buchyk@knu.ua</email>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ilya Pyatin</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Andrii Kulko</string-name>
          <email>kulko.andrii@gmail.com</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Khmelnytskyi National University</institution>
          ,
          <addr-line>11 Instytuts'ka str., Khmelnytskyi, 29016</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Khmelnytskyi Polytechnic Professional College by Lviv Polytechnic National University</institution>
          ,
          <addr-line>10 Zarichanska str., Khmelnytskyi, 29019</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Military Institute of Taras Shevchenko National University of Kyiv</institution>
          ,
          <addr-line>60 Volodymyrska str., Kyiv, 01033</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>Taras Shevchenko National University of Kyiv</institution>
          ,
          <addr-line>60 Volodymyrska str., Kyiv, 01033</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <fpage>15</fpage>
      <lpage>24</lpage>
      <abstract>
        <p>This article is devoted to the study of noise immunity of an infocommunication system with Polar Coding (P-C). The results of evaluating the performance of the Successive Cancellation (S-C) decoder are presented. The main contribution of this paper is the result of the compromise between high latency and Field Programmable Gate Array (FPGA) resources to implement a P-C decoder for 5G communications. The stages of channel polarization, the mathematical description of P-C, and the features of their description in binary channels are presented separately. This is achieved by the method of mathematical modeling of information and statistical characteristics of P-C for different code configurations. To check the correctness of the decisions made, a comparative description of the advantages and disadvantages of P-C decoding algorithms is given. The specifics of the FPGA implementation of the S-C algorithm have been studied. Based on the results of the experiment, the noise immunity of the P-C channel was assessed when changing the length of the code block, adding Cyclic Redundancy Check (CRC), and reversing bits at different code rates. It is expected that the results will be useful in optimizing the design process of real P-C circuits.</p>
      </abstract>
      <kwd-group>
        <kwd>1 5G</kwd>
        <kwd>FPGA</kwd>
        <kwd>polar codes</kwd>
        <kwd>decoding</kwd>
        <kwd>SNR</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Providing tasks related to the transmission of
information in mobile telecommunications is
certainly accompanied by a variety of error
scenarios [
        <xref ref-type="bibr" rid="ref1 ref2 ref3">1–3</xref>
        ]. Among the main factors in the
occurrence of errors, emphasis should be placed
on random noise, as well as the imperfection of
devices, which distorts streaming data on the
receiving side. In such situations, where the
concept of the receiver correcting such errors
without additional information from the
transmitter is involved, the forward error
Correction (FEC) Format Is Implemented [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ].
      </p>
      <p>
        When implementing 5G NR technology [
        <xref ref-type="bibr" rid="ref5 ref6 ref7">5–
7</xref>
        ], the solution to the above problems is
carried out by implementing the physical layer
channel coding format through the integration
of P-C and QCLDPC codes [
        <xref ref-type="bibr" rid="ref10 ref8 ref9">8–10</xref>
        ]. In general, 5G
implementation contains the concept of
increasing capacity for the eMBB deployment
scenario—mobile communications; URLLC—
ultra-reliable communication with minimal
latency and mMTC—machine-type mass
communications. This broad palette of 5G [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ]
implementations places a demand on channel
encoders/decoders to support a variety of
code lengths for both user and control data,
including robust implementation of automatic
repeat request (HARD) data.
      </p>
      <p>
        Analysis of reliable P-C application scenarios
allows us to confidently assert that such codes
can increase communication throughput and,
importantly, are characterized by simplified
encoding/decoding procedures. In this case,
you should pay attention to the S-C algorithm
[
        <xref ref-type="bibr" rid="ref12">12</xref>
        ], which, due to its satisfactory complexity,
has shown its effectiveness in real applications.
Another important property of this algorithm
is that it creates wide possibilities in the
context of improving hardware architecture. We
must emphasize that for P-C the compromise
between high latency and FPGA resources is a
problem area for reliable decoder
implementations in the task of ensuring high
throughput of information channels [
        <xref ref-type="bibr" rid="ref13 ref14">13, 14</xref>
        ].
      </p>
      <p>
        A significant part of the available literature
does not take into account the specifics of
codes for 5G scenarios, as well as the process
of encoding them, taking into account their
further widespread use in the design of
encoding circuits using FPGAs. The work [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ]
proposes a concept for implementing
performance enhancement by introducing
Polar Code Modulation with Physical Network
Coding (PM-PNC) over Two-Way Relay
Channels (TWRC). The article [
        <xref ref-type="bibr" rid="ref16">16</xref>
        ] focuses on
describing a proposed method for building a
Multi-Kernel (MK) P-C for 5G, based on large
kernels of the same size to improve the quality
of error correction. The paper [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ] proposes a
new coding scheme for 5G and P-C
MIMOOFDM systems to improve the efficiency of
channel error correction. The use of
Convolutional Neural Networks (CNN)
technology along with the use of P-C was
proposed, which resulted in a significant
increase in the reliability of the circuits. The
proposed work [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ] compares LDPC and P-C
for robust implementations of 5G NR-URLLC
channel coding schemes. An assessment of P-C
performance for the described scenarios is
given. Reasonable and balanced
recommendations for the design and practical
application of polar codes are reflected in
several current publications [
        <xref ref-type="bibr" rid="ref19 ref20 ref21 ref22">19–22</xref>
        ].
      </p>
      <p>Before formulating the problem statement
for the research presented in the article, we
will touch upon certain aspects of P-C. We
emphasize that P-C is a family of Error
Correction Codes (ECC), which are capable of
achieving the throughput of memoryless
symmetric channels. Such codes, with
sufficient correction capacity, can satisfy the
requirements for high-quality error correction
for current block lengths and reliable decoding
algorithms. It is these key factors that
determine the intensive use of such codes in 5G
applications.</p>
      <p>
        Analysis of the principles of P-C decoding
allows us to give such a characteristic to
decoding algorithms. In the case of SC, an
alternating bit evaluation of the message from
1 to N is implemented based on the format of
the decision procedure. Therefore, it is
important to note that the asymptotic
performance of the S-C generally corresponds
to the channel capacity, although in the case of
finite code lengths, it is not always satisfactory.
In this context, S-CL (successive cancellation
list) decoding minimizes errors [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ]. Note that
practical schemes for using P-C can be
implemented in a concatenated format with
other codes, in particular CRC [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. We also
have to decouple the recursive P-C decoding
scheme using Bhattacharyya Parameters (BP)
[
        <xref ref-type="bibr" rid="ref24">24</xref>
        ]. Analysis of the above-described works of
leading authors allows us to formulate the
main issues that are addressed in the article.
Thus, the complexity of the code determines
the amount of energy consumed by the
decoder, the amount of memory used, latency,
and the overall computing power. Channel
coding uses a set of operations on a data
stream aimed at error correction. In such a
context, to improve coding performance, it is
necessary to synthesize highly productive code
for efficient channel error localization. It is also
important to solve the problem of synthesizing
a decoding scheme with minimal cost,
satisfactory encoding rate, and computational
complexity.
      </p>
      <p>The proposed work contains an addition to
the works of the authors described above
regarding the study of a communication
system with an S-C decoder on an FPGA. Using
MATLAB tools, the effectiveness of the
proposed FPGA solutions was studied and the
decoding noise immunity was assessed.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Channel Polarization and Polar</title>
    </sec>
    <sec id="sec-3">
      <title>Encoder</title>
      <p>From the point of view of designing P-C using
FPGAs, it is quite important to maintain a
balance between the delay value and the
available matrix resources, which will directly
affect the increase in the performance of a
high-throughput decoder.</p>
      <p>The general form of description of the P-C code
word is х, implemented by representing the
code length as N=2n and by K as the number of
information bits. In addition, frozen bits in the
form N-K are described.
where   =   ⋅  2⊗ is the representation of
the generator matrix; BN is the form of the
degree.
permutation matrix,  2</p>
      <p>⊗ is the n-th Kronecker
 =  ⋅   ,
 2 = |
1
1
0
1</p>
      <p>|,</p>
      <p>Formula 3 represents the generator matrix
for</p>
      <p>N = 8.</p>
      <p>Thus,
the
encoding
scheme
equivalent to the generator matrix is shown in
× log2 0,5[ ( |0)+ ( |1)]
 ( | )</p>
      <p>( ) =
∑</p>
      <p>√ ( |0) ( |1),
where</p>
      <p>( | ) we denote the transition
probabilities between output y and input x.
(1)
(2)
(3)
(4)
(5)</p>
      <p>
        It should be noted that the parameters used
act as
measures of rate and
degree
of
reliability. So, by I(W) we mean the highest
rate while ensuring reliable communication
through W. Then Z(W) is interpreted as the
upper limit on the probability of error in the
case of a maximum likelihood decision. We
emphasize that in this case Z(W) and I(W)
belong to the values [
        <xref ref-type="bibr" rid="ref1">0, 1</xref>
        ]. An example of the
action of a binary channel with erasure (B-EC)
on a sequence of bits is shown in Fig. 2.
Channel capacity I(W)≈1 in the case of Z(W)≈0,
and I(W)≈0 in the case of Z(W)≈1 is described
by formulas 6 and 7 [26].
      </p>
      <p>(a)
(b)
on a sequence of (a) input and (b) output bits
An example of channel capacity calculation for
N = 8 is shown in Fig. 3. We used the following
indicators for calculation:
• Code length N = 8.
• Code rate R = 0.5.
• Number of information bits K = N*R = 4.
• Number of frozen bits F = N-K = 4.
• Positional configuration of information
bits Ai∊ (5,3,2,1).
• Positional configuration
of the bits
subjected to freezing A∊ (8,7,6,4).</p>
      <p>Therefore,
before
transmitting
the
sequences, the indices of the ascending-sorted
data sequence are divided into two sets. Thus,
in this design, the first set is formed by indices
of data transmitted in the absence of
interference in the channel. While the second
set covers known indices that are frozen and
transmitted over noisy channels.
Binary Symmetrical Channel (B-SC) and B-EC
refer to symmetrical channels. The polarization
operation can then be interpreted as the
formation of N independent copies of a given
BDMC channel W of another set of N channels
{  ( ): 1 ≤  ≤  } exhibiting the effect of
polarization in such an interpretation that
when N becomes large, the symmetric terms of
the capacity  (  ( )) are directed to 0 or 1 for
all indices (see Fig. 4a). This operation consists
of a channel combining step and a channel
splitting step. In Fig. 4a we present the effect of
channel polarization for conditions when W
enters the B-EC with probability ε=0.5. Fig. 4a
shows that  (  ( )) tends to be close to 0 for
small i and 1 for large i (is the node number, Fig.
4b) The binary tree formed by channel
polarization is shown in Fig. 4b.
An initial tree node is connected to channel W.
Such a node W forms a top path W2(1) and a
bottom path W2(2) that is connected to two
nodes at level 1. The path W2(1) in turn
generates branches of W4(1) and W4(2) so on.
Path W2(i) is located at level n of the tree at
node number i, counting from above.</p>
      <p>Let’s analyze Fig. 4a. By the concept
under consideration, the upper limit of BP
corresponds to the state of the channel
with the highest noise level, while the
lower limit characterizes the state of the
minimum noise. Consequently, the ideal
state is determined by the discontinuity
area in the BP extrema. At the transmitter
side, K information bits are inserted into
the noiseless channels, and N-K frozen bits
are inserted into the corresponding pure
noise channels to create an input vector  1
to be transmitted by the W channel. We use
the BP parameter as a measure of
reliability. Then such a parameter sets the
upper limit on the probability of decision
error for the maximum probability in the
case of a transmission channel of a binary
configuration.</p>
    </sec>
    <sec id="sec-4">
      <title>3. Polar Decoder Concept</title>
      <p>
        The basic polar decoding algorithm is already
mentioned in the S-C article. There are also
known decoding algorithms with higher
performance for relatively short codewords but
with greater complexity, such as the S-CL
algorithm, the successive cancellation list
decoding algorithm using CRC (CA-S-CL) [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], and
the Belief Propagation (PB) algorithm [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. The
PB algorithm is well known for its application in
LDPC decoding [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], in which soft messages are
exchanged between nodes. In addition, the S-LC
method stores a list of solutions and selects the
best solution using sorting. Both have better
performance, especially since the SLC algorithm
provides the best BER gain for P-C with short
block lengths. We will focus on the S-C decoding
algorithm for FPGA implementation due to its
satisfactory complexity.
      </p>
      <p>Fig. 5 shows the FPGA implementation of
the S-C decoder.</p>
      <p>Each decoding stage is made up of N/2
nodes of type f and g (see Fig. 5), which are
connected in a structure conceptually similar
to a Fast Fourier Transform (FFT) butterfly.
Nodes implement basic Likelihood Functions
(LLR) like:
 ( ,  ) = 2
ℎ [ ℎ (2) ⋅  ℎ ( )],
2
 ( ̂ ,  ,  ) = (1 − 2 ̂ ) +  ,
Estimated values are calculated as follows:
 ̂ = {
0,</p>
      <p>Pr( | ̂0−1,   = 0)
Pr( | ̂0−1,   = 1)</p>
      <p>≥ 1
1, otherwise</p>
      <p>
        Equation (8) can be replaced by the
minimum sum approximation, which is
described by the expression:
(6)
(7)
(8)
(9)
 ( ,  ) = min(| |, | |),
where a, b is the LLR.
This approximation is typical for calculating
the control node for the LDPC code [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]. The
node g implementing (7) is a conditional
addition/subtraction conditional on the value
of the decision bit  ̂ , where  ̂ is the bit
representing the partial sum modulo 2 of the
previously calculated bits. The rule for
calculating partial sums of  ̂ is based on a
structure that copies the corresponding P-S.
Inside the Flow Data Graph (FDG) decoder
there is an integrated FDG encoder. Then the
partial sum  ̂ for node, g1,2 is equal to  ̂2 ⊗
 ̂3, and the corresponding partial sum g3,4 is
equal to  ̂6. This means that to update node g,
its output must determine  ̂6. Then for hard
messages, we get the following rule:
      </p>
      <p>This approximation is used to calculate the
control node. The S-C decoding algorithm is
implemented by solving the following
problems. In the first stage, the LLR (12) is
determined and a hard decision is made. In the
next, second stage, solutions are recursively
propagated from the current nodes to the
corresponding previous stage.</p>
      <p>Thus, the end of the decoding process is the
selection of the codeword with the most
reliable path. In general, one can point to the
improved performance of SCL compared to SC.
This is especially noticeable at low noise levels
and low LLR values. However, the SCL
algorithm is more complex than the SC
algorithm and, in addition, the decoder has an
increased delay compared to the decoder
implemented in the article using the SC
algorithm.</p>
      <p>Conducting a brief digest of P-C decoding
algorithms, we emphasize that the CA-SCL
algorithm [27] is an improved SCL algorithm
for medium and short-length code structures.
We emphasize that CRC is a frequency
structure used to localize errors in several
information transmission schemes. In this
case, the K-bit encoder input block contains a
structure of k information bits and an m-bit
CRC sequence. CA-SCL-based decoding then
performs a CRC check to reliably determine
the codeword. This design is characterized by
increased productivity.</p>
      <p>It is necessary to mention the design of the
BP decoder described by Arikan [26]. The
structure of FDG here is similar to SC. However,
in this case, the transfer of hard decisions is
replaced with BP by estimates between check
nodes and variable nodes. In this case, you can
get a performance gain compared to SC, but
using the concept of parallelism is quite
problematic. Consequently, the BP decoder has
increased complexity and limited throughput
compared to the SC implementation</p>
    </sec>
    <sec id="sec-5">
      <title>4. Development of a Low</title>
    </sec>
    <sec id="sec-6">
      <title>Complexity Decoder</title>
      <p>The graph configuration (Fig. 5) during S-C
decoding is formed by 2n trees in binary form
[28, 29]. To optimally use the resources of the
FPGA circuit, one tree was built in binary form
with the option of having custom nodes.</p>
      <p>This architectural design of the P-C decoder
was based on the use of the same pair of LLRs
for a pair of nodes of type f and g. This
approach allows you to concentrate nodes of
type f and g in one processor unit. As noted
above, one evaluation tree of a binary design
was used—ûi (8). In this configuration, we
received
processing
a</p>
      <p>decoder
units, and
formed</p>
      <p>from
here the</p>
      <p>LLR
2n-1
is
estimated by</p>
      <p>making a hard decision. In
addition, the set of bit decisions used for the g
nodes in the processing units is concentrated
in memory for current use.</p>
      <p>Let’s consider an eight-point P-C model
based on the formation of two combinational
decoders with N=4. This format is used to
implement the parallel computing structure,
and the generated graph for N = 8 is used to
generate the input data of combinational
decoders. The calculation
of node
g is
implemented by supplying the output of the
encoder with correctly identified bits and
using the output of the decoder to make
decisions at node g in the next stage. In the
structure of the binary tree for the S-C
decoder, when some of the blocks are inactive,
an updated set of LLR channels is added.</p>
      <p>To implement a node of type f, in the
minimum sum (min-sum) approximation, the
circuit includes a component that solves the
ABC function to calculate the absolute value of
the output. A comparator circuit is used to
identify the
minimum
value. The circuit
includes two multiplexers, where the first
determines the
minimum
code value and
generates the comparator output signal. Then
the
output
of this
multiplexer
and
its
additional code are transmitted to the input of
the second multiplexer in Fig. 6а.</p>
      <p>The output signal of the XOR element
generates a multiplexer selection signal. We
calculate the min-sum using the following
form:</p>
      <p>The
node function
is formed by
conditional
depends
on
addition/subtraction,
which
the
bit
value
ûs at
the
corresponding point in the decoder functional
graph. Depending on the value, “a” is selected
in one of the warehouses, or the additional
code “a” is selected (Fig. 6b). This component
implements the adder. Node g is defined by the
following expression:
 ( ̂ ,  ,  ) = (1 − 2 ̂ ) +  ,
(13)

= 
∗ min(
(  ) ∗ 
(  ),  
(  )
(  )).
g</p>
      <p>(12)
(a)
(b)
the absolute value, CS is the compare and
select, MUX is the multiplexer, and (b) g: SUM
is the adder</p>
    </sec>
    <sec id="sec-7">
      <title>5. Experimental Studies of the</title>
    </sec>
    <sec id="sec-8">
      <title>Decoder</title>
      <p>We conducted the research by implementing
the communication system in MATLAB, Fig. 7.</p>
      <p>To implement the P-C encoder and decoder,
we selected the FPGA System-on-Chip (SoC)
Intel DE10-Standard Development Kit. The
Cortex-A9 processor has two integrated cores
with programmable logic. The Cyclone V SE
5CSXFC6D6F31C6N SoC integrates an
ARMbased Hard Processor System (HPS),
consisting of a processor, peripherals, and
memory interfaces coupled to an FPGA fabric.
To ensure the tasks of transmitting
information in a communication system via
PC, we supplemented the structure of the
encoded message with a CRC. The main
purpose of adding redundancy is to increase
noise immunity. Fig. 8 shows the general
shape of the resulting frame and the shape of
the generator polynomial:
Using the above expression, the following bit
sequence is formed: CRC-11 = [1 1 1 0 0 0 1 0
0 0 0 1]; CRC is effective as an external error
detection code. In the case when the code
length m does not agree with the length of the
encoded frame (2log(M)), it is necessary to use the
rate matching procedure by puncturing in N-M
positions, with a total codeword length of N.</p>
      <p>The next step is to carry out digital phase
modulation and transmit the signals into the
channel. The following operations are
performed in the receiver: demodulation; rate
restoration when the encoded sequence size
(N) is updated, in particular by the number of
punctured positions (P) of the codeword and
is sent to the decoder; polar decoding to
restore the transmitted message (described
above in the article); redundancy
implemented in the form of CRC is removed.</p>
      <p>Fig. 9a shows the results of a study of the
number of bit errors from the signal-to-noise
ratio (SNR) for a communication system with
BPSK modulation and different code block
lengths.</p>
      <p>There is no bit reversal, a CRC of 11 bits is
connected. For a P-C with block length M = 32
and code rate R = 1/2, the number of
informative bits taking into account CRC:
K = 16. The number of encoded bits at the
output of the P-C encoder is n = 32. In this case,
there is no puncturing of P-C positions for rate
matching [30].
(b)
Figure 9: Dependence of BER on Eb/N0 for a
communication system (a) With different code
block lengths: 1 is the 32 bits; 2 is the 64 bits;
3 is the 128 bits; 4 is the 256 bits; 5 is the 512
bits; 5 is the 1024 bit; (b) With CRC and bit
reversal
Fig. 9b shows the results of a study of BER
versus SNR [31] for a communication system
with CRC and bit reversal.</p>
      <p>From the results obtained, we can conclude
that with an increase in the size of the data
block (codeword) from 64 bits to 1024 bits,
the noise immunity of the communication
system increases by 1 dB.</p>
      <p>From the results obtained, we can conclude
that the presence of bit reversal accelerates
the BER attenuation by 0.2 dB. Connecting CRC
increases noise immunity by 0.5 dB.</p>
      <p>In Figs. 10a and 10b we present the results
of a study of the number of BER from the SNR
for a communication system [32] with
different exclusion list sizes (L) and different
code rates, respectively.
(b)
Figure 10: Dependence of BER on Eb/N0 for a
communication system (a) With different
decoder list sizes lengths: 1 is the no list; 2 is
the L = 1; 3 is the L = 2; 4 is the L = 4; 5 is the
L = 8; 6 is the L = 16; 7 is the L = 32; (b) With
different code rates: 1 is the R = 1/5; 2 is the
R = 1/3; 3 is the R = 2/5; 4 is the R = 1/2; 5 is
the R = 2/3; 6 is the R = 3/4; 7 is the R = 5/6; 8
is the R = 8/9
For modeling, the length of the code word was
M = 4000, the length of the code word at the
output of the encoder N = 4096, and the
number of punctured bits P = 96.</p>
      <p>From the obtained dependencies we can
conclude that the SLC decoder makes it
possible to increase the noise immunity of the
communication system: even the list size L = 2
increases the noise immunity by 0.7 dB
compared to the classic SL decoder. Further
increasing the list size does not provide a
significant performance improvement:
increasing the list size from L = 2 to L = 32
increases noise immunity by 0.8 dB, but adds
significant latency. Increasing the code rate has
a greater impact on the bit error rate:
increasing the code rate from 1/5 to 8/9
requires a 10 dB increase in the signal-to-noise
ratio, but allows a 4.5 times higher data rate.</p>
    </sec>
    <sec id="sec-9">
      <title>6. Conclusion</title>
      <p>A study of the P-C communication system was
carried out. The encoder, P-C decoder, and the
principles of channel polarization are
considered. The effect of the B-EC channel on a
sequence of bits is analyzed. The capacity I(W)
of each virtual polarized channel and the
principles of dividing these channels into “bad”
and “good” by BP value are determined.</p>
      <p>A study of the number of bit errors from the
signal-to-noise ratio was carried out for a
communication system with BPSK modulation
and different code block lengths, cyclic
redundancy code and bit reversal, different
sequential exclusion list sizes, and different
code rates. From the results obtained, we can
conclude that with an increase in the size of
the data block (codeword) from 64 bits to
1024 bits, the noise immunity of the
communication system increases by 1 dB. The
presence of bit reversal accelerates the BER
attenuation by 0.2 dB. Connecting CRC
increases noise immunity by 0.5 dB.</p>
      <p>Using an SLC decoder with a list size of L = 2
increases the noise immunity of the
communication system by 0.7 dB compared to
the classic SLC decoder. Further increasing the
list size L = 32 increases noise immunity by 0.8
dB, but adds a significant delay. Increasing the
code rate has a greater impact on the bit error
rate: increasing the code rate from 1/5 to 8/9
requires an increase in the SNR by 10 dB, but
allows you to increase the data transmission
rate by 4.5 times.</p>
    </sec>
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