• Journal of Communications and Networks
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• v.8 no.3
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• pp.306-312
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• 2006

This paper studies theoretically the bit error rate (BER) performance of cooperative transmission using space-time block code (STBC) in a fully distributed manner. Specifically, we first propose a STBC-based cooperative signaling structure to make the cooperation of three single-antenna terminals possible. Then, we derive the closed-form BER expressions for both cooperation and noncooperation schemes under flat Rayleigh fading channel plus additive white Gaussian noise (AWGN). The validity of these expressions is verified by Monte-Carlo simulations. A variety of numerical and simulation results reveal that the cooperative transmission achieves higher diversity gain and better performance than the direct transmission for the same total transmit power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12C
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• pp.1062-1067
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• 2008

ABBA codes, a class of quasi-orthognal space-time block codes (QoSTBC) proposed by Tirkkonen and others, allow full rate and a fast maximum likelihood (ML) decoding, but do not have full diversity. In this paper, a linear complex precoder is proposed for ABBA codes to achieve full rate and full diversity. Moreover, the same diversity produce as that of orthogonal space-time block code with linear complex precoder (OSTBC-LCP) is achieved. Meanwhile, the size of the linear complex precoder can be reduced by half without affecting performance, which means the same complexity of decoding as that of the conventional ABBA code is guaranteed.

• Journal of IKEEE
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• v.22 no.4
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• pp.1163-1167
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• 2018

The selective encryption scheme for canonical Huffman codes using the inversion of bit values is proposed. The symbols are divided into blocks of a certain size, and each symbol in the block is compressed by canonical Huffman coding. Blocks are determined to be sent in the original code or encrypted form. The encryption block inverts the values of the whole bits, and bits of block that do not encrypt are not inverted. Those compressed data are transmitted with the encryption information. It is possible to decrypt the compressed data on the receiving side using the encryption information and compressed data.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.136-139
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• 2000

In this paper, we propose a prime code and a new cryptographic algorithm for encryption and decryption as its application. The characteristics of prime numbers with irregular distribution and uniqueness are used to generate the prime code. Based on the prime code, an encryption algorithm for secret key is presented. Since the algorithm requires simpler operations than existing encryption such as DES, the burden for hardware implementation of the encryption and decryption process is alleviated.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.273-276
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• 2000

Recently, Turbo code has been considered for channel coding in IMT-2000(International Mobile Telecommunication-2000) system, because it offers better error correcting capability than the traditional convolution/viterbi coding . In this paper, a turbo code decoder for speech transmission in IMT-2000 system with frame size 192 bits, constrait length K=3, generator polynomials G(5,7) and code rate R=1/3 is designed using SOVA(Soft Output Viterbi Algorithm) and block interleaver

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.39-50
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• 2010

In this paper, we analyze and simulate the performance of a tactics mobile communication system based on ultra wide band (UWB) in multi-user interference (MUI) environments. This system adopts a double binary turbo code for forward error correction (FEC). Wireless channel is modeled a modified Saleh and Valenzuela (SV) model. We employ a space time block coding (STBC) scheme for enhancing system performance. System performance is evaluated in terms of bit error probability. From the simulation results, it is confirmed that the tactics mobile communication system based on UWB, which is encoded with the double binary turbo code, can achieve a remarkable coding gain with reasonable encoding and decoding complexity in multi-user interference environments. It is also known that the bit error probability performance of the tactics mobile communication system based on UWB can be substantially improved by increasing the number of iterations in the decoding process for a fixed cod rate. Besides, we can demonstrate that the double binary turbo coding scheme is very effective for increasing the number of simultaneous users for a given bit error probability requirement.

• The KIPS Transactions:PartB
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• v.18B no.6
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• pp.355-364
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• 2011

In most applications requiring high-confidential images, reversible watermarking is an effective way to ensure the integrity of images. Many watermarking researches which have been adapted to authenticate contents cannot recover the original image after authentication. However, reversible watermarking inserts the watermark signal into digital contents in such a way that the original contents can be restored without any quality loss while preserving visual quality. To detect malicious tampering, this paper presents a new block-based image authentication algorithm using differential histogram-based reversible watermarking. To generate an authentication code, the DCT-based authentication feature from each image block is extracted and combined with user-specific code. Then, the authentication code is embedded into image itself with reversible watermarking. The image can be authenticated by comparing the extracted code and the newly generated code and restored into the original image. Through experiments using multiple images, we prove that the presented algorithm has achieved over 97% authentication rate with high visual quality and complete reversibility.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.3
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• pp.309-316
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• 1986

A concatenated coding system using a binary code as the inner code and a nonbinary code as the outer code has been constructed for the purpose of error correction. The complexity of a conventional coding system grows exponentially as the code length of a block code becomes longer. To reduce the complexity for ling code, an effective communication system has been proposed by cascading two codes-binary and norbinary codes. Using a parallel-to-serial circuit and a serial-to-parallel circuit, the concatenated coding system has been designed and constructed by empolying a (7,3) burst error correcting code as the inner code and a (7,3) Reed-Solomon code as the outer code. This system has been simulated and tested using a micro-computer. For the (49,9) concatenated coding system, the error probability of the channel has been evaluated and compared to different coding systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.402-406
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• 2005

A multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) system using low-density parity-check (LDPC) code and iterative decoding is presented. The iterative decoding is performed by combining the zero-forcing technique and LDPC decoding through the use of the 'turbo principle.' The proposed system is shown to be effective with high order modulation and outperforms the space frequency block code (SFBC) method with iterative decoding.

• Journal of Communications and Networks
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• v.13 no.3
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• pp.205-210
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• 2011

This paper presents an approach to the construction of multiple-rate quasi-cyclic low-density parity-check (LDPC) codes. Parity-check matrices of the proposed codes consist of $q{\times}q$ square submatrices. The block rows and block columns of the parity-check matrix correspond to the hyperplanes (${\mu}$-fiats) and points in Euclidean geometries, respectively. By decomposing the ${\mu}$-fiats, we obtain LDPC codes of different code rates and a constant code length. The code performance is investigated in term of the bit error rate and compared with those of LDPC codes given in IEEE standards. Simulation results show that our codes perform very well and have low error floors over the additive white Gaussian noise channel.