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CONCATENATED CODESLDPC concatenated space-time block coded system inmultipath fading environment: Analysis and evaluation

PROPOSED BY:SHAVEL

2K14-MRCE-MTECH-ECE-07

UNDER THE GUIDENCE OF: MR. ABHISHEK ANAND MR.LOKESH BHARDAWAJ MR. ANAND SINGH RAJPOOT

WIRELESS DATA IS GROWING

EXPONENTIALLY…… YouTube In 2014 ~ average 192 views for every person on Earth. (Over 1 Trillion views) More videos is uploaded to YouTube in one month than the 3 major US networks created in 60 years. 72 hours of video are uploaded to YouTube every minute. 25% of global YouTube views come from mobile devices. SOURCE: https://www.youtube.com/user/Usersurvey

Internet video traffic is growing at 48% CAGR SOURCE:http://www.cisco.com/c/en/us/solutions/collateral/service-provider/ip-ngn-ip-next-generation-network/white_paper_c11-481360.html1

11

…LEADING TOP RF SPECTRUM SHORTAGE

SOURCE: http://www.cisco.com/assets/sol/sp/vni/forecast_highlights_mobile

OBJECTIVE

To reduce BER of a channel so that we can send the signal

with minimal noise through the communication path of a

channel.

To achieve the speed enhancement.

HOW TO EVALUATE CODE

PERFORMANCE?

Need to consider Code Rate (R), SNR (Eb/No), and Bit Error Rate (BER).

Coding Gain is the saving in Eb/No required to achieve a given BER when coding is used vs. that with no coding.

Generally the lower the code rate, the higher the coding gain.

Better Codes provides better coding gains.

Better Codes usually are more complicated and have higher complexity.

LDPC : LOW DENSITY PARITY CHECK

In 1962, Gallager reported work on binary codes defined in terms of low density parity check matrices.

In 1996, LDPC codes are re-discovered by D. MacKay and R. Neal.

They show it to have very good coding gain performance.

LDPC represented by parity check matrix and tanner

graph.

PROCEDURE FOR ENCODING

Consider a 6-bit long code word

There are three parity check equation as shown below:- ,

H is a the parity check matrix. It defines the code rate Check1 to check3 are check nodes. Variable1 to variable6 are variable nodes. H=

CONTD.

Code word is said to be valid if it satisfies the syndrome calculation:-

Systematic form of H by applying gauss Jordan elimination:-

From H generator matrix can be obtained:-

Code word(C) =

TANNER GRAPH

Variable nodes check nodes

DECODING OF LDPC CODE

There are two types of decoding of LDPC codes:-

Hard decision.

Soft decision.

LDPC use message passing decoding technique.

Hard decision is based on Gallager algorithm.

Soft decision is based on Belief Propagation

STEPS INVOLVED IN DECODING

The Steps involve in Message passing decoding :

Initialize the decoder by sending the received value of the

variable node to the check node.

In each check node, message for each neighbor variable

node is calculated and sent.

Each variable node calculate a new value for itself depending

upon a received value and extrinsic information from the

check node.

CONTD.

Output is checked by the parity check equation and if all are

checked then decoding is over.

Otherwise message for each neighbor check node is

calculated and sent.

Repeat the steps until the maximum no. of iteration is

reached.

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Iterative message passing decoding

Receivernoise

Iteration 1

Transmitter

Iteration 5 Iteration 15 Iteration 16

channel

Ethernet cable,Wireless,

or Hard disk

DECODING PICTURE EXAMPLE

CONCATENATED CODES

Coined in 1966 by Dave Forney as a solution to the problem of finding a code that has both exponentially decreasing error probability with increasing block length and complexity.

Concatenated codes form a class of error-correcting codes that are derived by combining an inner code and an outer code.

Turbo codes, as described first in 1993, implemented a parallel concatenation of two convolutional codes

STBC: SPACE TIME BLOCK CODE

STBC used in wireless communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data-transfer.

STBCs may be orthogonal or quasi-orthogonal.

Spatial multiplexing MIMO systems, such as BLAST, achieve high throughput but generate high levels of co-channel interference, which degrades performance.

OSTBCs are popular because they achieve full diversity and good performance for low detection complexity.

BLOCK DIAG: TX & RX STRUCTURE

CONCLUSION The bit error rate performance of concatenated irregular

LDPC codes has been evaluated in faded environments.

STBC along with LDPC, it helps in increasing the channel capacity.

It is use in high data rate systems.

Increases efficiency of simulation algorithm. Work can be extended to increase the system reliability

and reduce the decoder complexity.

THANK YOU