Comparison between LDPC codes and QC-LDPC codes in term of PAPR in OFDM system with different encoding techniques

Abstract In this paper, LDPC codes and OFDM technologies are studied, and combines LDPC and OFDM to simulate and verify the performance. The encoding of LDPC and logarithmic domain BP decoding algorithm and the principle of OFDM are introduced. Through MATLAB, the simulation of OFDM-LDPC system in different channel, different code length, different iteration times, LDPC and OFDM-LDPC in the same conditions are compared. Through simulation analysis, we can know that the performance of OFDM-LDPC system will improve with the increase of the code length. When the SNR is small, the number of iterations has little effect on the performance of OFDM-LDPC system. When the SNR is large, the performance of the system will be improved with the increase of the number of iterations. The performance of OFDM-LDPC codes is better than that of LDPC codes. The performance of OFDM-LDPC code is better than LDPC code in multipath Rayleigh fading channel.

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MIMO-Filtered OFDM System Improvement Using Modified Concatenated RS/LDPC Codes

10.21203/rs.3.rs-1022604/v1 ◽

2021 ◽

Author(s):

Ghasan Ali Hussain

Keyword(s):

Wireless Communication ◽

Communication Systems ◽

Ldpc Codes ◽

Ldpc Code ◽

Error Rates ◽

Wireless Communication Systems ◽

Ofdm System ◽

Rs Codes ◽

Concatenated Code ◽

Ber Performance

Abstract In mobile communication systems, there are errors that will be generated in the digital signal due to fading and interference. Consequently, different techniques are used to improve the system's reliability and enhance the signal's robustness. Channel coding techniques are used to enhance the system reliability of 5G wireless communication systems . In the upcoming wireless technologies, LDPC codes are still introduced as an alternative to turbo codes. However, the error floor phenomenon is one of the biggest demerits of using LDPC code in the different communication systems that need low error rates. This paper uses RS codes with LDPC codes in a concatenated code to solve this demerit of LDPC codes. Meanwhile, a modified concatenated RS/LDPC codes are created using outer RS codes with inner LDPC codes then appended by interleaver, unlike the conventional concatenated codes that use the interleaver between both codes. Thereafter, the modified concatenated RS/LDPC codes were suggested to enhance BER performance for the f-OFDM system. The results showed that using the proposed concatenated code outperformed using single and familiar concatenated RS/LDPC code in terms of improving BER performance. Meanwhile, the proposed system achieved lower OOBE values than the conventional OFDM system. Therefore, the resulted system can be introduced as a competitor candidate for 5G wireless communication systems due to these features

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Performance Studies of Advanced QC-LDPC Codes Applied to CO-OFDM System

Asia Communications and Photonics Conference 2013 ◽

10.1364/acpc.2013.af2f.13 ◽

2013 ◽

Author(s):

Niu Huijuan ◽

Bai Chenglin ◽

He Feifei ◽

Xu Hengying ◽

Wang Qiuguo ◽

...

Keyword(s):

Performance Studies ◽

Ldpc Codes ◽

Ofdm System

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Improvement of LDPC Codes Decoding Algorithm in the Application of the Rotational OFDM System

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.934.235 ◽

2014 ◽

Vol 934 ◽

pp. 235-238

Author(s):

Zeng You Sun ◽

Huan Huan Li

Keyword(s):

Turbo Codes ◽

Computational Cost ◽

Ldpc Codes ◽

Bp Algorithm ◽

Ofdm System ◽

Decoding Algorithm ◽

Ldpc Decoding ◽

Rotational Modulation ◽

Channel Environment ◽

Better Than

Because the performance of LDPC codes is better than Turbo codes, convolution codes, etc., so the combination of LDPC codes and the OFDM technology has higher effectiveness. Traditional LDPC decoding algorithm (BP algorithm) exists large amounts of multiplication, division and index calculation, and when decoding cycle, its computational cost will increase exponentially, which not only increases the complexity, and makes the numerical stability of the algorithm deteriorates, therefore, in this paper, we propose an improved decoding algorithm, namely the combination algorithm of Offset-BP-base and Offset BP. In the AWGN channel environment and the rotational modulation of OFDM, compared with LLR BP algorithm and BP-based algorithm, the improved algorithm improves the performance of the system, and the complexity is reduced.

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