Information Theory and Coding I Seminar. Final Presentation

1. Electrical Engineering and Computer Science
Department
Analysis of Coding Techniques in
LTE-Advanced / 4G
Advisor: Dr. Torkamani
Instructor: M. Naslcheraghi
Jan, 2015

2. Retransmission of data
Information
Reliable
Information
number of
symbols in the
source encoded
message is
increased
Error
Detection
Correction
Amount Depends on SNR
coding techniques in LTE-Advance
a broadly used term mostly referring to the
forward error correction code
Transmission channel
can often be avoided, at the cost of higher
bandwidth requirements on average

3. Performance Evaluation of physical layer of 4G
•Reed-Solomon Coding
•convolution coding
For Coding
Schemes
•Cyclic Prefix
•Interleaving
For
Modulation
Schemes

4. Physical Layer Infrastructure Setup
Random Data
Generation
IFFT Cyclic Prefix
insertion
Chanel Encoding Mapping
Cyclic Prefix
Removal
FFT
De-mappingChanel DecodingOutput Data
IEEE 802.162004

5. Step 1
• Randomization
Step 2
• Forward Error Correction (FEC)
Step 3
• Interleaving
Step 2.1
• Reed-Solomon (RS)
Step 2.2
• Convolutional Code
Channel Encoding Setup

6. Full Channel Coding/Decoding Setup
Data
Randomization
Reed-Solomon
Encoding
Convolutional
Encoding
Interleaving
De-Interleaving
Convolutional
Encoding
Reed-Solomon
Encoding
De- Randomization
Encoding Setup
Decoding Setup

7. Randomization necessity
On each burst of each allocation, a long sequence of
continuous ones and zeros will be generated.
Solution is Randomization with Scrambler
Implementation with a Pseudo Random Binary
Sequence (PRBS) Generator which uses 15 stage shift
register with a generator polynomial of 1+x14+x15
with XOR gates in feedback configuration.

8. Reed-Solomon coding setup
Block Format
Randomized
Data
Before Coding
single 0X00 tail byte is
appended to the end of each burst
RS Encoder

9. Implementation of RS
(Specially in LTE Systems)
Encoder
• Systematic RS with these Parameters:
(N=255, K=239, T=8) With GF= 2
Code Generator and Field Generator Derived from
8

10. Main Characteristic of
LTE-RS Encoder
• support shortened and punctured code to facilitate variable block sizes and
variable error correction capability.
k´ bytes Shortened Block ?
adding
239k´
zero
bytes
Data
Block
RS- Encoding
Encoded
Data Block
Will be Discarded after decoding

11. Convolutional Coding Setup
• Fed for encoder ?
convolutional
encoder
RS-Encoded
Data Block
Final Encoded
Data Block

12. Implementation of Convolutional
Encoder (Specially in LTE)
native rate of ½
constraint length of 7

13. Size of the block is depended on the numbers of bit
encoded per sub channel.
In one OFDM symbol.
Defined in IEEE 802.16
Final Encoded
Data Block
Block
Interleaver
Interleaved Data
RSCC

14. IFFT
• The grey mapped data are then sent to IFFT for time domain mapping. Mapping to time domain
needs the application of Inverse Fast Fourier Transform (IFFT). In our case we have incorporated the
MATLAB ´IFFT´ function to do so. This block delivers a vector of 256 elements, where each complex
number clement represents one sample of the OFDM symbol.

15. Cyclic Prefix Insertion
• A cyclic prefix is added to the time
domain samples.
• to combat the effect of multipath

16. References
1. International Journal of Computer Applications (0975 –
8887), Analysis of Coding Techniques in LTE.
2. Google!

17. Direct Download
www.Teleinfra.net/download/coding.pdf