• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.9A
• /
• pp.1313-1321
• /
• 2000

In recent years LEO(Low Earth Orbit) satellite communication systems have gained a lot of interest as high speed multimedia services by satellite are about to be provided. It is mandatory to use very efficient ECC(Error Correcting Code) to support high speed multimedia services over LEO satellite channel. Turbo codes developed by Berrou et al. in 1993 have been actively researched since it can achieve a performance close to the Shannon limit. In this paper, a LEO satellite channel model is adopted and the fading characteristics of LEO satellite channel are analyzed for the change of elevation angle in various propagation environments. The performance of turbo code is analyzed and compared to that of conventional convolutional code using the satellite channel model. In the simulation results using the Globalstar orbit constellations, performance of turbo codes shows 1.0~2.0dB coding gain compared to that of convolutional codes over all elevation angle and propagation environment ranges we have investigated. The performance difference resulting from the change of elevation angle in various propagation environments and the performance of different ECC are analyzed in detail, so that the results can be applied to choose an appropriate ECC scheme for various system environment.

• Information and Communications Magazine
• /
• v.18 no.6
• /
• pp.74-91
• /
• 2001

본 고에서는 통신 시스템에 응용되고 있는 블록부호에 대한 소개와, IMT-2000 시스템의 표준화에서 채널 부호화 기법으로 규격에 반영된 길쌈부호(Convolutional code) 및 터보부호(Turbo code)에 대하여 소개하고, 현재 3세대 이동통신 표준화에서 논의중인 Hybrid ARQ(Adaptive Modulation and Coding), AMC(Adaptive Modulation and Coding) 기술에 대하여 설명한다. 그리고, 고속의 데이터 전송을 요하는 4세대 이동통신 시스템의 채널 부호화 기술로 현재 활발히 연구가 이루어지고 있는 Space-Time Code 및 LDPC(Low Density Parity Check Code)에 대해 소개하고, 차세대 이동통신 시스템의 채널 부호화 기술 전반에 대하여 전망한다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.2
• /
• pp.258-264
• /
• 2004

WLAN technologies enable high-speed data transmission in a small space with relatively low cost and power. There are two main standardizations regarding WLAN; namely, IEEE802.11a and ETSI BRAN. Two standards use a radio frequency of 5 ㎓ band and employs OFDM as a transmission mode. OFDM is known to provide high-frequency efficiency as well as high-speed data transmission. In this paper, We use SPW simulation tool and implement the HIPERLAN/2 system. Based on the HIPERLAN/2 system in the SPW platform, the system performance is analyzed and compared with turbo codes in place of a convolutional coder of the HIPERLAN/2 WLAN system. The simulation results show that the performance with the turbo codes (rate 1/3 and 1/4) at a data rate of 12 Mbps shows 3 ㏈ gain over the system with the convolutional codes. At a data rate of 36 Mbps, the performance with the turbo codes is further improved by approximately 4 ㏈.

• Proceedings of the KIEE Conference
• /
• 2008.10b
• /
• pp.396-397
• /
• 2008

OFDM 송수신 시스템에서 채널성능을 개선하기 위해 CDD(Cyclic Delay Diversity) 기술을 적용하면, Frequency Interlea ving의 영향으로 인해 burst error가 randomize되어, convolutional code/Viterbi decoding FEC의 BER 성능개선 효과를 배가 할 수 있다. 그러나 차세대 통신시스템에 적극 활용되는 Turbo FEC는 자체 interleaving 구조를 가지고 있으므로, CDD기술과의 결합으로 인한 영향을 증명하기 위하여, 본 논문에서는 Turbo FEE를 사용하는 OFDM CDD시스템을 MATLAB을 이용한 computer simulation을 통해서 BER 성능을 비교분석 하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.4
• /
• pp.11-16
• /
• 2004

A simple stopping criterion for iterative decoding based on min-sum processing is presented. While most stopping criteria suggested in the literature, are based on Cross Entropy (CE) and its simplification, the proposed stopping criterion is to check if a decoded sequence is a valid codeword along the encoder trellis structure. This new stopping criterion requires less computational complexity and saves mem4)ry compared to the conventional stopping rules. The numerical results are presented on the 3GPP turbo code and a Serially Concatenated Convolutional Cods (SCCC).

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.309-313
• /
• 2009

In this paper, the network performance of a turbo coded optical code division multiple access (CDMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated. We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) for satellite broadcasting communications is considered. In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical CDMA network can be substantially improved by increasing the interleaver length and the number of iterations in the decoding process. The results of this paper can be applied to implement the satellite broadcasting communications.

• 한국정보통신설비학회:학술대회논문집
• /
• 2009.08a
• /
• pp.314-319
• /
• 2009

In this paper, the network performance of a turbo coded optical code division multiple access (COMA) system with cross-layer, which is between physical and network layers, concept is analyzed and simulated We consider physical and MAC layers in a cross-layer concept. An intensity-modulated/direct-detection (IM/DD) optical system employing pulse position modulation (PPM) is considered In order to increase the system performance, turbo codes composed of parallel concatenated convolutional codes (PCCCs) is utilized. The network performance is evaluated in terms of bit error probability (BEP). From the simulation results, it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding and decoding complexity. Also, it is confirmed that the performance of such an optical COMA network can be substantially improved by increasing the interleaver length and the number of iterations in the decoding process. The results of this paper can be applied to implement the indoor optical wireless LANs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.6C
• /
• pp.570-579
• /
• 2003

The performance of turbo codes is investigated in the direct detection optical PPM channel. We assume that an ideal photon counter is used as an optical detector and that the channel has background noise as well as quantum noise. Resulting channel model is M-ary PPM Poisson channel. We propose the structure of the transmitter and receiver for applying turbo codes to this channel. We also derive turbo decoding algorithm for the proposed coding system, by modifying the calculation of the branch metric inherent in the original turbo decoding algorithm developed for the AWGN channel. Analytical bounds are derived and computer simulation is performed to analyze the performance of the proposed coding scheme, and the results are compared with the performances of Reed-Solomon codes and convolutional codes.

• The Journal of the Acoustical Society of Korea
• /
• v.39 no.6
• /
• pp.585-591
• /
• 2020

The adaptive transmission techniques are efficient method for underwater acoustic communication to improve the system efficiency by varying transmission parameters according to channel conditions. In this paper, we construct four transmission modes with different data rates using the convolutional codes, which is freely set to size of information bits. On the receiver side, one critical component of adaptive system is to find which mode has best performance. In this paper, we proposed threshold detection algorithm to decide appropriate mode and applied turbo equalization method based on BCJR decoder in order to improve performance. We analyzed the performance of four modes based on threshold detection algorithm through the lake experiment.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.1
• /
• pp.67-72
• /
• 2001

Convolutional code and turbo code are used in the forward and backward link of IMT-2000. In this research, we will be in consideration of Viterbi algorithm In this paper, we design Viterbi decoder with 3-bits soft decision and SMT for the convolutional code in the forward link and backward link of IMT-2000 system. The major parameters of 3-bits Viterbi decoder is determined by simulation to have identical performance with the 4-bit soft decision Viterbi decoder.