DDS Assignment 1

A set of error correction codes that can be used to detect and correct bit
errors that can occur when compute data is moved or stored.
Used for error free communication in communication system.
In communication system, information data transferred from source to

destination by channel.
In between source and destination data may be corrupted due to any type of
noise.
To find original information we use Hamming code error detection and

correction technique.
Extra bits that are generated and transferred along with data transfer to
ensure no bits were lost during data transfer.
We add these redundancy bits to the information data at the source end and
remove at destination end.
Presence of redundancy bit allows the receiver to detect or correct corrupted

bit
To get error free data at destination, we
1. Encrypt information data according to even and odd parity method before
transmission of information at source end.
2. Decryption and Correction(in case of any errors) at the receivers end.
Formula for generating redundancy bit ---2^ r >= D + r + 1 ------------------------------------------- (1)
Here r = number of redundancy bit;

D = number of information data bit
Calculate the
number of number of redundancy bit for 25 bit of input data string by above
formula we get 5 redundancy bit required.
The redundancy bits are placed at the position that corresponds to the power
of 2, i.e., 1, 2, 4, 8 and so on.
TRANSMITTER
The First block with data input represents the input, which we will give to the
encoder.
Next, the Encoder part will add the redundancy bits to the data and give out
the data to PiSo.
The PiSo is responsible for converting the given parallel input to serial output.
Every bit is transferred separately.
RECEIVER
We use serial to parallel conversion to get the location of the bits.
Decoder part receives the parallel data from SiPo, responsible for detecting
error, and correcting the error. The decoder will give out the location of the
erroneous bit, with the actual data without any error and without any
redundancy bits.
In hamming code with even and odd parity check method by using Verilog
HDL, we transmit 25 bit information data with 5 redundancy bits from source
and receive this data at destination.
To find the value of these redundancy bits we have two methods
1. Even parity method

2. Odd parity method
Destination receives 30 bit data, which was transmitted by source end.
This received data may be corrupted due to noise. To remove this noise we
find the address of error bit then correct them.
For finding the location of error bit and correct them we use again even parity
check method and/or odd parity check method .
In addition, we have added two Converters
1. PISO (Parallel In Serial Out ) and

2. SIPO (Serial In Parallel Out)
Used to transmit the data.
We have also written code for decrypting this 30 bit encrypted data into 25
bit information data.
No need to use another circuit for decryption of encrypted data. Up to today,

at destination we were using one circuit for correcting error bit and another
circuit for finding the information data from encrypted data.
Now we can use only one circuit for correction error bit and finding the actual
information data.
We transmit 8 bits of information using 4 redundancy bits.
Suppose the actual data we want to transfer is

01001101
Procedure:
Redundancy bits are placed at positions 1, 2, 4, 8
??0?100?1101
P1= ? 0 1 0 1 0 = 0
P2= ? 0 0 0 1 0 = 1
P3= ? 1 0 0 1
=0
P4= ? 1 1 0 1
=0
Redundancy bits are placed at positions 1, 2, 4, 8

??0?100?1101
P1= ? 0 1 0 1 0 = 0
P2= ? 0 0 0 1 0 = 1
P3= ? 1 0 0 1
=0
P4= ? 1 1 0 1
=1
New Encoded data to be transmitted is,

010010011101
Data to be received at the receiver.

010010011101
Actual data received( due to noise or error)

010010011111
Calculate parity bits again
P1= 0 0 1 0 1 1
(Parity not correct)
P2= 1 0 0 0 1 1
P4= 0 1 0 0 1
(correct)
P8= 1 1 1 1 1
Parity bits 1 , 2 and 8 are not correct. So to find erroneous bit position we add
1+2+8 = 11.
This implies 11th bit is the erroneous bit. So we change it to 0.
The decrypted and corrected data is

therefore, 0 1 0 0 1 0 0 1 1 1 0 1
We have used Xilinx ISE 10.1 Simulator for simulating and synthesized
Verilog HDL Code.
Xilinx ISE 10.1 Simulator is a simulator which is used for simulating HDL
language and schematic circuit diagram.

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A set of error correction codes that can be used to detect and correct bit

errors that can occur when compute data is moved or stored.

Used for error free communication in communication system.

In communication system, information data transferred from source to

To find original information we use Hamming code error detection and

Presence of redundancy bit allows the receiver to detect or correct corrupted

To get error free data at destination, we

Formula for generating redundancy bit ---2^ r >= D + r + 1 ------------------------------------------- (1)

Here r = number of redundancy bit;

Every bit is transferred separately.

We use serial to parallel conversion to get the location of the bits.

To find the value of these redundancy bits we have two methods

1. Even parity method

Destination receives 30 bit data, which was transmitted by source end.

In addition, we have added two Converters

1. PISO (Parallel In Serial Out ) and

Used to transmit the data.

No need to use another circuit for decryption of encrypted data. Up to today,

We transmit 8 bits of information using 4 redundancy bits.

Suppose the actual data we want to transfer is

Redundancy bits are placed at positions 1, 2, 4, 8

Redundancy bits are placed at positions 1, 2, 4, 8

New Encoded data to be transmitted is,

Data to be received at the receiver.

Actual data received( due to noise or error)

Calculate parity bits again

(Parity not correct)

(Parity not correct)

(Parity not correct)

This implies 11th bit is the erroneous bit. So we change it to 0.

The decrypted and corrected data is

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