Design of high speed reconfigurable coprocessor for interleaver and de interleaver operations

1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 30-38 © IAEME
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DESIGN OF HIGH SPEED RECONFIGURABLE
COPROCESSOR FOR INTERLEAVER AND DE-
INTERLEAVER OPERATIONS
Mallikarjunaswamy S1
, Dr.Nataraj K.R2
, Balachandra P3
, Sharmila N.4
1
Research Scholar Jain University,
2, 3
SJB Institute of Technology, Bangalore-60,
4
R.N.S.Institute of Technology, Bangalore-98
ABSTRACT
In this paper we present the high speed reconfigurable co –processor for interleaver and de-
interleaver system. Today’s communications systems have to perform in the midst of extreme signal,
complex depth and diversity .With help of reconfigurable co-processor we can ensure the
communications systems are ready for next generation operations . The communication system
commonly uses an interleaver and de-interleaver technique for security purpose to overcome burst
error such as correlated channel noise and authentication. The proposed reconfigurable co-processor
for interleaver and de-interleaver is more accurate, reliable and flexible. The interleaver and de-
interleaver coprocessor has been implemented using VHDL and the synthesis has been done by
model-sim. The critical path is of about 0.16 nm technology and gate count of about 34,000.The
Performance comparisons shows the Proposed co-processor can reduce the clock cycles for
interleaving (8-bit=50%, 32-bit =81.45%),67 % de-interleaver for the IEEE 802.11a standard (12
Mbps data rate). and compared with existing DSP’s. From the results, the proposed co-processor
show good performance compered to existing DSP chip in terms of number clock’s per cycle.
Keywords: Interleaver, De-interleaver, Binary symmetric channel (BSC) and length shift register
sequence (LFSR)
INTRODUCTION
Digital communications are disposed to random correlated channel noise such as fading or
burst errors. Interleaving is most commonly used for error correction in stream of codes to make
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2. International Journal of Electronics and Communication Engineering &
6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp.
them operative in a burst noise location
blocks of data. Any burst noiseoccurring will be reflected on the receiver side decoder
interleaver as self-regulating random symbol error which is more controllable than burst errors.
Interleavers can be classified as either pseudo random or periodic
for periodic interleaving, periodic
interleaver accepts the symbols in
interleaving is most commonly invoked as it is easily accomplished in hardware .
interleaver rearranges the data in a pseudo random sequence.
Interleaving and De-interleaving
systems toovercome burst error such as correlated channel noise and authentication
rearranges input data such that sequential
data is organized back into the original
interleaving, correlated noise introduced in
independent at the receiver and thus allows better error correction.
form of two-dimensional array, the data is read in along its row wise. Once the array is full, same
data is read out along its column wise, thus changing the order of the data. (The interleaver process is
denoted by the Greek letter π and de
is illustrated in Figure 4 the original data order
process. The de-interleaver arranged in the form of two
its column wise and read out by row wise. This interleaver may be present between the outer encoder
and inner encoder at transmitter side there is two component codes uses a concatenated code .the de
interleaver between the inner decoder and outer decoder at receiver side, as shown in Figure 4. Due
this process the changing of some order of original data in o
of two-dimensional array, the data is read in along its row wise. Once the array is full, same data is
read out along its column wise, thus changing the order of the data. (The interleaver process is
denoted by the Greek letter π and de
Figure.1. Concatenated code Encoder and Decoder with Interleaver
The interleaver process is illustrated in Figure 1
corresponding de-interleaver process
array.The data is read in along its column wise and read out by row wise. This interleaver may be
present between the outer encoder and inner encoder at transmitter side there is two component
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
6472(Online), Volume 6, Issue 1, January (2015), pp. 30-38
31
location. The interleaver spreads out end-to-end
Any burst noiseoccurring will be reflected on the receiver side decoder
regulating random symbol error which is more controllable than burst errors.
either pseudo random or periodic. Block interleaving is an example
eriodic interleaverinstruct the data in a repeating sequence
interleaver accepts the symbols in form of blocks and necessary operations perform on
interleaving is most commonly invoked as it is easily accomplished in hardware .
eaver rearranges the data in a pseudo random sequence.
interleaving is a technique most commonly used in communication
toovercome burst error such as correlated channel noise and authentication
sequential data are spread out. At the receiver end, the interleaved
back into the original data sequence by the de-interleaver.
interleaving, correlated noise introduced in the transmission channel appears to be statistically
independent at the receiver and thus allows better error correction. The interleaver arranged in the
dimensional array, the data is read in along its row wise. Once the array is full, same
ata is read out along its column wise, thus changing the order of the data. (The interleaver process is
and de-interleaver process is denoted by π–1.) The interleaver process
is illustrated in Figure 4 the original data order can be restored by a corresponding de
interleaver arranged in the form of two-dimensional array, the data is read in along
its column wise and read out by row wise. This interleaver may be present between the outer encoder
nner encoder at transmitter side there is two component codes uses a concatenated code .the de
interleaver between the inner decoder and outer decoder at receiver side, as shown in Figure 4. Due
this process the changing of some order of original data in order to interleaver arranged in the form
dimensional array, the data is read in along its row wise. Once the array is full, same data is
read out along its column wise, thus changing the order of the data. (The interleaver process is
and de-interleaver process is denoted by π–1.)
. Concatenated code Encoder and Decoder with Interleaver
ess is illustrated in Figure 1.The original data order can be restored by a
process [1]. The de-interleaver arranged in the form of two
data is read in along its column wise and read out by row wise. This interleaver may be
present between the outer encoder and inner encoder at transmitter side there is two component
Technology (IJECET), ISSN 0976 –
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end data over numerous
Any burst noiseoccurring will be reflected on the receiver side decoder after De-
regulating random symbol error which is more controllable than burst errors.
Block interleaving is an example
the data in a repeating sequence of bytes. This
perform on data. Periodic
interleaving is most commonly invoked as it is easily accomplished in hardware .Pseudo random
commonly used in communication
toovercome burst error such as correlated channel noise and authentication. The interleaver
At the receiver end, the interleaved
interleaver. As a result of
the transmission channel appears to be statistically
The interleaver arranged in the
dimensional array, the data is read in along its row wise. Once the array is full, same
ata is read out along its column wise, thus changing the order of the data. (The interleaver process is
1.) The interleaver process
can be restored by a corresponding de-interleaver
dimensional array, the data is read in along
its column wise and read out by row wise. This interleaver may be present between the outer encoder
nner encoder at transmitter side there is two component codes uses a concatenated code .the de-
interleaver between the inner decoder and outer decoder at receiver side, as shown in Figure 4. Due
rder to interleaver arranged in the form
dimensional array, the data is read in along its row wise. Once the array is full, same data is
read out along its column wise, thus changing the order of the data. (The interleaver process is
. Concatenated code Encoder and Decoder with Interleaver
original data order can be restored by a
e form of two-dimensional
data is read in along its column wise and read out by row wise. This interleaver may be
present between the outer encoder and inner encoder at transmitter side there is two component

3. International Journal of Electronics and Communication Engineering &
6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp.
codes uses a concatenated code .the de
receiver side, as shown in Figure 1
order to make extraction of the original signal difficult to the un
shown in Figure 2.
Figure.2. Operations of Interleaver and De
A COMMUNICATION SYSTEM AND INTERLEAVER
Figure
Figure 3 shows the basic communication
(sequence of messages or producing
message to maintain security, modulation process and convert it to a suitable signal for operations), a
channel (a medium like wire or air etc.)
the destination (a machine or a person)
noise (switch noise, lightening), channel distortion or white
noise. The different modulation takes
channel model termed as binary symmetric channel (BSC).
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976
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32
codes uses a concatenated code .the de-interleaver between the inner decoder and outer decoder at
eiver side, as shown in Figure 1, due to this process the changing of some order of original data in
order to make extraction of the original signal difficult to the un-authorization perso
Operations of Interleaver and De-Interleaver.
A COMMUNICATION SYSTEM AND INTERLEAVER – FIRST ENCOUNTER
Figure.3. Basic communication system model
the basic communication system. It consists of an information source
(sequence of messages or producing a message), transmitterit have a capability to operate on the
message to maintain security, modulation process and convert it to a suitable signal for operations), a
like wire or air etc.), a receiver (basically inverse of transmitter operations),and
the destination (a machine or a person)[2]. The noise source can be definedas fading
, channel distortion or white noise. In this paper deals only on burst
takes place at transmitter side. For binary transmission we are using
channel model termed as binary symmetric channel (BSC).
Technology (IJECET), ISSN 0976 –
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oder and outer decoder at
, due to this process the changing of some order of original data in
authorization person this process
.
FIRST ENCOUNTER
consists of an information source
it have a capability to operate on the
message to maintain security, modulation process and convert it to a suitable signal for operations), a
basically inverse of transmitter operations),and
as fading or burst errors
n this paper deals only on burst
place at transmitter side. For binary transmission we are using

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6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 30-38 © IAEME
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Figure.4. A simplified transmission and reception over a noisy channel
Figure 4 shows a basic binary symmetric channel (BSC) with transition probability p. It can
be calculated by knowing the value of signal properties, amount of noise expected (i.e. probability
distribution of noise) and the quantization thresholds of the modulator. With the encoding process, at
receiver side the message bits are encoded in to code word c with a probability P(r c)of the received
vector r [4].
BLOCK DIAGRAM DESCRIPTION
Based on different implementation features, the interleavers are divided in two main types
named as convolutional interleaver and block interleave. There are some other classifications based
on their properties, which will also be discussed briefly in later sections.at transmitter side of the
interleaver, the information coming from the encoder is in the form of blocks. The permutations are
appliedand then block of data is passed to two dimension array for further modulations. The normal
implementation of a block interleaver is performed by Row-Column matrix of size R x C, where R is
total number of rows and C is the total number of columns.
Figure.5. Simple block interleaving without permutations
Figure 5shows the basic block diagram and performance of interleaving. In this illustration
there is no inter-row or inter-column permutations are used, thus the interleaver is operated on some
systematic order. The row-column block of interleaver gives the advantage that it isolates the burst
errors of size R by a distance C [5]. If some situation a periodic single error sequence with period R
affects the transmission, at receiver side a de-interleaver produces a burst of errors with size C. In
this situation further permutations need and it increase the implementation complexity.

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Figure.6. Block interleaving with row and column permutations
Figure.6.shows an illustration of an interleaver block withdifferent row and column
permutations is given in. The permutations are applied with certain format after the information has
been written to the R x C row column matrix [6]. At receiver side the original data order can be
restored by a corresponding de-interleaver process
Other than row-column matrix construction, a block interleaver can also be constructed by
using other methods. An example of generating the block interleaver is by defining a primitive
polynomial to generate a maximal length shift register sequence called maximal length LFSR as
shown in Figure 7. A maximal length LFSR generates all the addresses by cycling through all the
possible states except the state where all bits are zero. The start of addressing sequence is defined by
introducing a starting seed value. When block size is less than the complete cycle of the primitive
polynomial, a pruning device has to be incorporated to discard the invalid indices. Based on different
construction methodologies and properties, the block interleavers can further be divided in different
sub-categories which will be described in a later section.
Figure 7 A maximal length LFSR with n=12

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Figure 7 shows an interleaver module used for primitive polynomial to be generated by using
maximal length shift register sequence is called maximal length LFSR. This module generates all
physical addresses by cycling through the entire probable states apart from the state where all bits are
zero [7][8]. The starting seed value defines the staring addresses sequence. If complete cycle is
greater than the block size ofthe primitive polynomial, in such case a pruning device has to be in-
corporate to reject the invalid indices. Based on different construction properties and methodologies,
the interleaver module can further be divided in different sub-categories.
CONVOLUTIONAL INTERLEAVER
Figure 8 shows a convolutional interleaver. It consists of X rows of shift registers, with
different delay in each row. In general each consecutive row and columns has a delay which is N
codes duration higher than the previous row. The encoder sends a code word symbols into the array
of shift register, one code symbol to each row .ever time each new code word symbols the
commutator switches to a new shift registers and right most columns code word symbol come out to
the channel. The ith
(1<i≤ X-1) shift register has a length of (i-1) N levels where N=M/X and the last
row require M-1 number of delay elements. The convolution de-interleaver executes the inverse
operation of the interleaver and structure and delay elements are also different. Zeroth row of the
interleaver becomes an X-1 row in the de-interleaver,1st row of the pervious becomes N-2 row of
later and so on.
Figure.8. Convolutional Interleaver
HARDWARE DESCRIPTION OF COPROCESSOR
In our experimentation, Xilinx Spartan-3 (device XC3S 400) with 400K gate count FPGA is
used [9]. Ithas total 896 numbers of configurable logic blocks (CLBs) arranged in 32 X 28 matrix
fashion. Each CLBhas four slices and two of them are named as SLICEM and rest two as SLICEL.
Each SLICEM can be used as16 bit (embedded) shift register (SRL16). DAB application requires a
convolutional interleaver of array size [6]; of 17 X j (j = 0, 1… 11) = 1122 numbers of delay
elements. Numbers of SRL 16 required to implement the interleaver is 77 which is only 4.3% of
available SRL16. Because of our efficient FPGA implementation technique, sufficient FPGA
resources are made available for implementing other circuitry of the transmitter / receiver [9].

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PROPOSED MODEL OF CONVOLUTIONAL INTERLEAVER
In our proposed work interleaver and de-interleaver coprocessor has been implemented by
using VHDL and synthesis has been done by model-sim. The critical path of about 0.16 nm
technology and gate count of about 34,000 FPGA is used [10].it has total 900 configurable logic
blocks (CLBs) arranged in 48x28 matrix. Each configurable logic blocks has four slices and digital
audio broadcast application requires a convolution interleaver of array size [11]
A novel architecture of reconfigurable co-processor for interleaver and de-interleaver of an 8
bit convolutional interleaver with N=1 is shown in figure 9. The code word symbols (Xin) received
in serial from an encoder is converted by the serial input parallel output (SIPO) register converts the
code word symbols (Xin) received from an encoder into an 8 bit parallel code word. The SIPO
output changes its value with respect to clock which is not necessary at the input of the delay input.
The delay unit receives a word from the buffer unit after every 8 clock cycles. A buffer unit sends a
code word to the delay unit. The delay unit is comprised of eight rows and is requiring a structure as
narrated in figure 9. Each 8 bit code word of the code symbols isapplied to the respective rows of the
delay unit. In delay unit the code word is scrambled and the scrambled code word then applied to the
8:1 multiplexer (MUX) which converts it into stream of serial data (Xout).the SIPO register in an
interleaver circuit is driven by the clock signal, a three bit counter and a clock circuit. The clock
circuit divides the system clock frequency by 8 which in turn used to drive the delay and buffer unit.
The 3-bit counter generates a select input for the 8:1 MUX.The proposed reconfigurable co-
processor for de-Interleaver is exactly similar to figure 9 but inverse operation. The scrambled code
word is converted into its original code word at the de-interleaver output side.
Figure.9. Block diagram of proposed 8 bit convolutional interleaver.
Figure 10 shows the 8 bit input signal (111111112) is applied at data_in input of the
interleaver at receiver side. The interleaver generates a scrambling output data at data_out. This
scrambled output is applied as a input to the De-interleaver which rearranges them in such a way that
the original code word is generated at output side(data_out).
CRITICAL ANALYSIS OF MODEL-SIM IMPLEMENTATION RESULTS
The novel architecture model of Convolutional interleaver de-interleaver pairs (both 8 bit, 32
bit and 64-bit) has been implemented by using VHDL and synthesis has been done by model-sim
Xilinx Spartan-3 (Device: XC3S400) FPGA platform. Table I shows the comparison between
proposed co-processor for interleave, de-interleaver and Star-Core SC140 the Proposed co-processor

8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 30-38 © IAEME
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can reduce the clock cycles for interleaver (8-bit=50%, 32-bit =81.45%) and 67 % de-interleaver for
the IEEE 802.11a standard (12 Mbps data rate).
Table I Performance Comparison for Interleaver and De-Interleaver
Interleaver
word length
1 bit delay
units required
SC140 Proposed system
Slice
saving in %
8 bit 8 X 7 = 56
56 ÷ 2 =
28
14 50.00 %
32 bit
32 X 31 =
992
992 ÷ 2
= 496
92 81.45 %
Figure 10. Simulation result with input code word = 111111112
CONCLUSIONS
In this work, we have proved the design and the implementation of high speed reconfigurable
Co-processor for interleaver and De-interleaver. The reconfigurable coprocessor that can support
various communication standards and algorithms. Interleaver and De-interleaver influential
conventional and scramble technique. Main objective of this paper is to improve the security
purpose, overcome burst error such as correlated channel noise and authentication, to increases the
redundant by using co-processor and perform many parallel operations without any overhead and
performance of reconfigurable co-processor is compared with existing DSP (SC140). The interleaver
and de-interleaver coprocessor has been implemented by using VHDL and synthesis has been done

9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 30-38 © IAEME
38
by model-sim. The critical path of about 0.16 nm technology and gate count of about 34,000.The
Performance comparisons shows the Proposed co-processor can reduce the clock cycles for
interleaving (8-bit=50%, 32-bit =81.45%), 67 % de-interleaver for the IEEE 802.11a standard (12
Mbps data rate) and compared with existing DSP’s. From the results, the proposed co-processor
shows good performance compered to existing DSP chip in terms of number clock’s per cycle.
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