This document discusses turbo and turbo-like codes. It begins with an introduction to turbo codes, describing them as a class of high-performance error correction codes that were the first practical codes to closely approach channel capacity. It then covers channel coding, Shannon's theory, existing coding schemes like block codes and convolutional codes, and the need for better codes. The document spends significant time explaining turbo codes in detail, including their structure using parallel concatenated convolutional codes, interleaving, and iterative decoding. It also discusses related coding schemes like turbo product codes and low-density parity check codes. Finally, it reviews the performance, practical issues, applications in standards, and future trends of turbo and turbo-like codes.
This chapter provides an introductory lecture note on the Error Control Coding techniques. Before one goes into the details of different types of Coding schemes, this note will acquaint the readers with all the terms related and associated to Error Control Coding. It is highly recommended that one goes through this article before delving deep into the coding schemes.
LDPC Encoding is explained in this ppt. for MATLAB code and more information you can visit link given below:
http://www.slideshare.net/bhagwatsinghmahecha/itc-final-report
A second important technique in error-control coding is that of convolutional coding . In this type of coding the encoder output is not in block form, but is in the form of an encoded
sequence generated from an input information sequence.
convolutional encoding is designed so that its decoding can be performed in some structured and simplified way. One of the design assumptions that simplifies decoding
is linearity of the code. For this reason, linear convolutional codes are preferred. The source alphabet is taken from a finite field or Galois field GF(q).
Convolution coding is a popular error-correcting coding method used in digital communications.
The convolution operation encodes some redundant information into the transmitted signal, thereby improving the data capacity of the channel.
Convolution Encoding with Viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN.
It is simple and has good performance with low implementation cost.
Manchester & Differential Manchester encoding schemeArunabha Saha
The two main variants of biphase encoding techniques are discussed here. Manchester and Differential Manchester encoding scheme are explained with examples. Comparison between several classes of polar encoding techniques are done along with the exposure about the advantages and disadvantages of both schemes.
LDPC codes have been discovered a long time ago & re-discovered after invention of turbo codes. These two codes are actors of revolution of error correcting codes theory.
In this thesis, the principle of LDPC codes will be studied.
Besides, based on this, design is done for the IP core, involves
LDPC code performance and construction of behavioural model for Encoder & Decoder using Generator matrix and parity check matrix , then use Model sim for compilation & simulation also test bench design is made to test Encoder & Decoder blocks.
LDPC - Encoding
LDPC code is a linear error correcting code, a method of transmitting a message over a noisy transmission channel. An LDPC is constructed using a sparse bipartite graph.
In our Project:
Encoding a LDPC code was done in Matlab hardware implementation was done on FPGA-Field ProgrammableGate-Array using Verilog
Energy-Efficient LDPC Decoder using DVFS for binary sourcesIDES Editor
This paper deals with reduction of the transmission
power usage in the wireless sensor networks. A system with
FEC can provide an objective reliability using less power
than a system without FEC. We propose to study LDPC
codes to provide reliable communication while saving power
in the sensor networks. As shown later, LDPC codes are more
energy efficient than those that use BCH codes. Another
method to reduce the transmission cost is to compress the
correlated data among a number of sensor nodes before
transmission. A suitable source encoder that removes the
redundant information bits can save the transmission power.
Such a system requires distributed source coding. We propose
to apply LDPC codes for both distributed source coding and
source-channel coding to obtain a two-fold energy savings.
Source and channel coding with LDPC for two correlated nodes
under AWGN channel is implemented in this paper. In this
iterative decoding algorithm is used for decoding the data, and
it’s efficiency is compared with the new decoding algorithm
called layered decoding algorithm which based on offset min
sum algorithm. The usage of layered decoding algorithm and
Adaptive LDPC decoding for AWGN channel reduces the
decoding complexity and its number of iterations. So the power
will be saved, and it can be implemented in hardware.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
This chapter provides an introductory lecture note on the Error Control Coding techniques. Before one goes into the details of different types of Coding schemes, this note will acquaint the readers with all the terms related and associated to Error Control Coding. It is highly recommended that one goes through this article before delving deep into the coding schemes.
LDPC Encoding is explained in this ppt. for MATLAB code and more information you can visit link given below:
http://www.slideshare.net/bhagwatsinghmahecha/itc-final-report
A second important technique in error-control coding is that of convolutional coding . In this type of coding the encoder output is not in block form, but is in the form of an encoded
sequence generated from an input information sequence.
convolutional encoding is designed so that its decoding can be performed in some structured and simplified way. One of the design assumptions that simplifies decoding
is linearity of the code. For this reason, linear convolutional codes are preferred. The source alphabet is taken from a finite field or Galois field GF(q).
Convolution coding is a popular error-correcting coding method used in digital communications.
The convolution operation encodes some redundant information into the transmitted signal, thereby improving the data capacity of the channel.
Convolution Encoding with Viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN.
It is simple and has good performance with low implementation cost.
Manchester & Differential Manchester encoding schemeArunabha Saha
The two main variants of biphase encoding techniques are discussed here. Manchester and Differential Manchester encoding scheme are explained with examples. Comparison between several classes of polar encoding techniques are done along with the exposure about the advantages and disadvantages of both schemes.
LDPC codes have been discovered a long time ago & re-discovered after invention of turbo codes. These two codes are actors of revolution of error correcting codes theory.
In this thesis, the principle of LDPC codes will be studied.
Besides, based on this, design is done for the IP core, involves
LDPC code performance and construction of behavioural model for Encoder & Decoder using Generator matrix and parity check matrix , then use Model sim for compilation & simulation also test bench design is made to test Encoder & Decoder blocks.
LDPC - Encoding
LDPC code is a linear error correcting code, a method of transmitting a message over a noisy transmission channel. An LDPC is constructed using a sparse bipartite graph.
In our Project:
Encoding a LDPC code was done in Matlab hardware implementation was done on FPGA-Field ProgrammableGate-Array using Verilog
Energy-Efficient LDPC Decoder using DVFS for binary sourcesIDES Editor
This paper deals with reduction of the transmission
power usage in the wireless sensor networks. A system with
FEC can provide an objective reliability using less power
than a system without FEC. We propose to study LDPC
codes to provide reliable communication while saving power
in the sensor networks. As shown later, LDPC codes are more
energy efficient than those that use BCH codes. Another
method to reduce the transmission cost is to compress the
correlated data among a number of sensor nodes before
transmission. A suitable source encoder that removes the
redundant information bits can save the transmission power.
Such a system requires distributed source coding. We propose
to apply LDPC codes for both distributed source coding and
source-channel coding to obtain a two-fold energy savings.
Source and channel coding with LDPC for two correlated nodes
under AWGN channel is implemented in this paper. In this
iterative decoding algorithm is used for decoding the data, and
it’s efficiency is compared with the new decoding algorithm
called layered decoding algorithm which based on offset min
sum algorithm. The usage of layered decoding algorithm and
Adaptive LDPC decoding for AWGN channel reduces the
decoding complexity and its number of iterations. So the power
will be saved, and it can be implemented in hardware.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Performance Analysis of Steepest Descent Decoding Algorithm for LDPC Codesidescitation
Among various hard decision based Bit Flipping (BF)
algorithms for decoding Low-Density Parity-Check (LDPC)
codes such as Weighted Bit Flipping (WBF), Improved
Reliability Ratio Weighted Bit Flipping (IRRWBF) etc., the
Steepest Descent Bit Flipping Algorithm (SDBF) achieves
better error performance. In this paper, the performance of
the Steepest Descent Algorithm for both single steepest
descent and Multi steepest descent modes is analysed. Also
the performance of IEEE 802.16e standard is analysed using
Steepest Descent Bit Flipping (SDBF) decoding algorithm.
SDBF requires fewer check node and variable node operations
compared to Sum Product Algorithm (SPA) and Min Sum
Algorithm (MSA). The SDBF achieves a coding gain of 0.1 ~
0.2 dB compared to Single-SDBF without requiring complex
log and exponential operations.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Reed Solomon Coding For Error Detection and Correctioninventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
PERFORMANCE ESTIMATION OF LDPC CODE SUING SUM PRODUCT ALGORITHM AND BIT FLIPP...Journal For Research
Low density parity check code is a linear block code. This code approaches the Shannon’s limit and having low decoding complexity. We have taken LDPC (Low Density Parity Check) code with ½ code rate as an error correcting code in digital video stream and studied the performance of LDPC code with BPSK modulation in AWGN (Additive White Gaussian Noise) channel with sum product algorithm and bit flipping algorithm. Finally the plot between bit error rates of the code with respect to SNR has been considered the output performance parameter of proposed methodology. BER are considered for different number of frames and different number of iterations. The performance of the sum product algorithm and bit flip algorithm are also com-pared. All simulation work has been implemented in MATLAB.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
A new channel coding technique to approach the channel capacityijwmn
After Shannon’s 1948 channel coding theorem, we have witnessed many channel coding techniques developed to achieve the Shannon limit. A wide range of channel codes is available with different complexity levels and error correction performance. Many powerful coding schemes have been deployed in the power-limited Additive White Gaussian Noise (AWGN) channel. However, it seems like we have arrived at an end of advancement path, for most of the existing channel codes. This article introduces a new coding technique that can either be used as the last coding stage of concatenated coding scheme or in parallel configuration with other powerful channel codes to achieve reliable error performance with moderately complex decoding. We will go through an example to understand the overall approach of the proposed coding technique, and finally we will look at some simulation results over an AWGN channel to demonstrate its potential.
LDPC BASED ERROR CORRECTION WITH BIT LEVEL AND SYMBOL LEVEL SYNCHRONIZATION USING MARKER CODE OPTIMIZATION
Low-density parity check code with error-correction capabilities and Marker code for synchronization purposes are used
The marker code structures offer the ultimate achievable rate when standard bit-level synchronization are performed
Symbol-level synchronization algorithm works on group of bits and show how it improves the achievable rate along with the error rate performance
When multiple pass decoding is performed the extrinsic information transfer (EXIT) charts are used to analyze the receiver
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
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2. Content:
Introduction to Turbo Codes
Channel Coding
Shannon’s Theory
FEC Coding Schemes
A Need for Better Codes
Turbo Codes
Turbo-Like Codes
Performance Analysis
Practical Issues for Turbo FEC
Turbo and Turbo-Like Codes in Standards
Future Trends
Conclusions
References
3. Introduction to Turbo Codes
In information theory, turbo codes are a class of high-
performance forward error correction (FEC) codes developed around
1990–91 (but first published in 1993), which were the first practical codes
to closely approach the channel capacity.
Turbo codes achieve their remarkable performance with relatively low
complexity encoding and decoding algorithms.
4. Channel Coding
To encode the information sent over a communication channel in such a
way that in the presence of channel noise, errors can be detected and/or
corrected.
It Can be categorized into:
1. Backward error correction (BEC)
2. Forward error correction (FEC )
5. Shannon’s Theory
For every combination of bandwidth (W), channel type, signal power (S)
and received noise power (N), there is a theoretical upper limit on the data
transmission rate R, for which error-free data transmission is possible. This
limit is called channel capacity or also Shannon capacity.
It sets a limit to the energy efficiency of a code.
A decibel is a relative measure. If E is the actual energy and Eref is the
theoretical lower bound, then the relative energy increase in decibels is
6. A Need for Better Codes
Energy efficiency vs Bandwidth efficiency
Codes with lower rate (i.e. bigger redundancy) correct more errors.then
communication system can operate with a lower transmit power, transmit
over longer distances, tolerate more interference, use smaller antennas
and transmit at a higher data rate. These properties make the code energy
efficient.
Low-rate codes have a large overhead and are hence more heavy on
bandwidth consumption. Also, decoding complexity grows exponentially
with code length.
8. Block Codes
A block code is any member of the large and important family of error-
correcting codes that encode data in blocks.
Most common example is Hamming Code.
Take a block of length ‘k’ (information sequence).
Then encode them into a codeword , the last (n-k)bits are called Parity bits.
Parity bits are used for error checking and correcting.
9. Convolution Codes
Convolution codes are error detecting codes used to reliably transmit
digital data over unreliable communication channel system to channel
noise.
The convolution codes map information to code bits , but sequentially
convolve the sequence of information bits according to some rule.
Convolutional codes are often described as continuous.
Viterbi and soft output Viterbi are most common.
10. ENCODING CIRCUIT
The code is defined by the circuit, which consists of different
number of shift registers
11. Cntd…
We generate a convolution code by putting a source stream through a
linear filter. This filter makes use of a shift register, linear output functions
and possibly linear feedback.
In a shift register, the information bits roll from right to left.
In every filter there is one input bit and two output bits. Because of each
source bit having two transmitted bits, the codes have rate ½.
12. DEFINING CONVOLUTION CODE
A convolution code can be defined by using a generator matrix that
describes the
encoding function u → x :
x = u .G
For 3 information bit long sequence u = (u0 ,u1 ,u2 )
we get
((x0 (1) x0 (2) ), (x1 (1)x1 (2) ), (x2 (1) x2 (2) )) = (u0 ,u1 ,u2 ) .G
13. PUNCTURING OF CONVOLUTION
CODES
The idea of puncturing is to delete some bits in the code bit sequence according to a fixed
rule.
In general the puncturing of a rate K / N code is defined using N puncturing vectors.
Considering a code without puncturing, the information bit sequence
u =(0,0,1,1,0) generates the (unpunctured) code bit
sequence
xNP= (00,00,11,01,01). The sequence xNP is punctured using a
puncturing matrix:
PI= 1110
1001
The puncturing period is 4. Using P1 , 3 out of 4 code .
The performance of the punctured code is worse than the performance of the mother code.
14. DECODING CONVOLUTION CODES
The most probable state sequence can be found using the min-sum
algorithm (also known as the Viterbi algorithm).
The viterbi algorithm is used to decode convolutional codes and any
structure or system that can be described by a trellis.
It is a maximum likelihood decoding algorithm that selects the most
15. Concatenated Codes
Some times single error correction codes are not
good enough for error protection.
Concatenating two or more codes will results more powerful
codes.
Types of concatenated codes
1. Serial concatenated codes
2. Parallel concatenated codes
17. Turbo Codes
The Parallel-Concatenated Convolutional Codes(PCCC), called turbo
codes, has solved the dilemma of structure and randomness through
concatenation and interleaving respectively.
The introduction of turbo codes has given most of the gain promised by
the channel coding theorem.
Turbo codes have an astonishing performance of bit error rate (BER) at
relatively low Eb /No.
18. Turbo Encoder
The output stream of data consists of the systematic data, parity bits from
encoder1, and parity bits from encoder2.
Through the use of the interleaver, the decoder will have two independent
looks at the same data, and can use both streams to decode the
information sequence
19. Interleaver
The interleaver’s function is to permute low weight code words in one
encoder into high weight code words for the other encoder.
A “row-column” interleaver: data is written row-wise and read column
wise. While very simple, it also provides little randomness.
A “helical” interleaver: data is written row-wise and read diagonally.
An “odd-even” interleaver: first, the bits are left uninterleaved and
encoded , but only the odd-positioned coded bits are stored. Then, the
bits are scrambled and encoded, but now only the even-positioned coded
bits are stored. Odd-even encoders can be used, when the second encoder
produces one output bit per one input bit.
20.
21. Recursive Systematic Coders
Recursive codes are typically systematic.
The example encoder is systematic because the input data is also used in
the output symbols.
Recursive systematic convolutional (RSC) codes have become more
popular due to their use in Turbo Codes.
22. Turbo Decoding
Criterion:
For n probabilistic processors working together to estimate common symbols, all
of them should agree on the symbols with the probabilities as a single decoder could do.
The inputs to the decoders are the Log likelihood ratio (LLR) for the individual symbol d.
LLR value for the symbol d is defined ( Berrou) as
The SISO decoder reevaluates the LLR utilizing the local Y1 and Y2 redundancies to
improve the confidence .
Compare the LLR output, to see if the estimate is towards 0 or 1 then take HD.
23. Cntd…
The value z is the extrinsic value
determined by the same decoder and it
is negative if d is 0 and it is positive if d
is 1
The updated LLR is fed into the other
decoder and which calculates the z and
updates the LLR for several iterations
After several iterations , both decoders
converge to a value for that symbol.
24. Turbo Product Codes
The serial concatenation of block codes separated by a structured
permutation (either implicit or explicit) was introduced in the 1950s. Codes
with this structure are referred to as product codes.
Product codes may have many dimensions but are usually restricted to 2
or 3.
Applying iterative decoding to such code structures results in TPCs, and
exchanging soft extrinsic information yields good performance.
Iterative decoding of TPCs is performed by alternately decoding along the
different dimensions of the code, where again reliability information is
represented as true or approximate LLRs.
Turbo Product Codes (TPCs) are based on block codes, not convolutional
codes.
25. Construction and Decoding of TPC
An elementary decoder for a single dimension of a multidimensional turbo product code
26. Low-Density Parity Check Codes
Any linear block code can be defined by its parity-check matrix. If this
matrix is sparse, i.e it contains only a small number of 1s per row or
column, then the code is called a low-density parity-check code.
Basically there are two different possibilities to represent LDPC codes:
─ Matrix Representation
─ Graphical Representation
A regular LDPC matrix is an binary matrix having exactly Y ones in each
column and exactly ones in each row , where < and both are small
compared to m.
If H is low-density but the number of 1’s in each row or column aren’t
constant the code is called a irregular LDPC code.
27. Representation
Parity Check Matrix: (with dimension “ n × m ” for a (8 ,4)
code)
─ ρ = the number of 1‘s in each row
─ γ = the number of 1’s in each column
For a matrix to be called low-density the two conditions
γ<<n, ρ<<m must be satisfied.
Bipartite Graph(so-called Tanner Graph): that means that
the nodes of the graph are separated into two distinctive
sets:
Variable nodes(v-nodes)
Check nodes(c-nodes)
─ m check nodes (the number of parity bits
─ n variable nodes (the number o bits in codeword
28. Turbo-Like Codes
Some forms of turbo FEC do not fall neatly into any of the previous three
categories and are referred to as turbo-like codes.
Hybrids of turbo codes and LDPC codes fall into this category.
Convolutional codes are often used as the constituent codes, resulting in
serially concatenated convolutional codes (SCCCs).
Decoding is performed in a manner similar to the parallel concatenated
case, iteratively applying SISO decoders for each constituent code.
29. Performance Analysis of Turbo Codes
BER performance of cdma2000
turbo code
WER performance of
cdma2000 turbo code
30. Performance Analysis of Turbo Product
Codes
BER performance of the IEEE
802.16 TPC
WER performance of the IEEE
802.16 TPC
32. Practical Issues for Turbo FEC
Error Rate Performance and Power Savings
Computational Complexity
Parallelism
Memory Requirements
Latency
Flexibility
Effect on Synchronization
33. TURBO OR TURBO-LIKE CODES IN
STANDARDS
3G Wireless:
1. W-CDMA(Wideband code-division multiple-access)
2. CDMA2000
3. TD-SCDMA(Time-division, synchronous CDMA)
Satellite Communications:
1. Consultative Committee for Space Data Systems (CCSDS)
2. Digital Video Broadcasting-Return Channel via Satellite
3. Digital Video Broadcasting via Satellite Second Generation
Wireless Networking:
1. Wi-MAX (IEEE 802.16)
2. Wi-Fi (IEEE 802.11)
34. Future Trends
Turbo and turbo-like codes will be widely used for at least the next decade
and probably substantially longer.
No single class of turbo or turbo-like codes will dominate in the way that
convolutional codes and Viterbi decoding did in the past.
Substantial improvements in computational efficiency and reductions in
unit costs are still possible.
An increasing number of turbo and turbo-like codes will be tailored to
different channel conditions and system designs.
The success of turbo FEC has led to the application of soft iterative
decoding techniques beyond channel coding.
35. Conclusions
The advent of turbo and turbo-like codes has shown that excellent
performance, closely approaching the ultimate Shannon capacity limit for
an AWGN channel.
It can be achieved through the soft iterative decoding of composite
channel codes.
Implementing and using turbo and turbo-like codes in real systems does
present challenges, but tremendous progress in addressing these issues
has been made, and all varieties of turbo FEC are finding application.
Turbo and turbo-like codes are no longer a curiosity or novelty, but a
powerful tool for improving the performance of communications systems.