• Title/Summary/Keyword: Code Rate

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A Study on the Compressed Code for Biological Signal (생체신호 데이터의 압축코드 알고리즘에 관한 연구)

  • Hong, Seung-Hong;Son, Chang-Il;Min, Hong-Gi
    • Journal of Biomedical Engineering Research
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    • v.5 no.1
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    • pp.93-102
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    • 1984
  • In this paper, the real-time compressed code generation method for the biological signal data, especially for the Electrocardiogram, is studied. For this purpose, variable length code is introduced. And from this code, we get a exactly the same reconstructed signal data as the original. Experimental results show that this program reduces the data rate by a factor of about 8, and codes the result in a form convenient for analysis.

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Robust Video Transmission System Employing Byte-Aligned Variable-Length Turbo Codes and Its Code-Rate Adaptation over Mobile Communication Channels (이동통신 환경에서 바이트 정렬 가변 길이 터보 코드의 적응 부호화율 적용을 통한 동영상 전송 시스템)

  • 이창우;김종원
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.7C
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    • pp.921-930
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    • 2004
  • In this paper, a robust video transmission system is proposed. To effectively prevent the corruption of video stream and its propagation in spatial and temporal domains, a version of turbo code, so-called as byte-aligned variable-length turbo code, is applied. Protection performance of the proposed turbo code is first evaluated by applying it to GOB-based variable-size ITU-T H.263+ video packets, where the protection level is statically controlled based on the joint source-channel criteria. This protection is then extended to support the adaptation of code ratio to best match the time-varying channel condition. The time-varying Rayleigh fading channel is modelled considering the correlation of the fading channel. The resulting performance comparison with the static turbo code as well as the conventional RCPC code clearly demonstrates the possibility of the proposed adaptation approach for the time-varying correlated Rayleigh-fading channel.

Multilevel Modulation Codes for Holographic Data Storage (홀로그래픽 데이터 저장장치에서의 멀티레벨 변조부호)

  • Jeong, Seongkwon;Lee, Jaejin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.9
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    • pp.13-18
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    • 2015
  • The mutilevel holographic data storage offers considerable advantage for capacity, since it can store more than one bit per pixel. In this paper, we search the number of codewords for each code depending on three conditions: (1) the number of levels, (2) the number of pixels in a codeword, and (3) the minimum Euclidean distance of a code. Increasing the number of levels per pixel creates more capacity, while causing more errors, by reducing the noise margin. Increasing the number of pixels in a codeword can increase the code rate, which means more capacity, but increases the complexity of the encoder/decoder of the code. Increasing the minimum distance of a code reduces the detection error, while reducing the code rate of the code. In such a fashion, a system design will always have pros and cons, but our task is to find out an effective one under the given conditions for the system requirements. Therefore, the numbers we searched can provide some guidelines for effective code design.

A Sparse-ON Pixel Two-Dimensional 6/8 Modulation Code (저밀도 ON 픽셀 2차원 6/8 변조부호)

  • Hwang, Myungha;Lee, Jaejin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.10
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    • pp.833-837
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    • 2013
  • Since holographic data storages read and write information on a volume and the information is processed per page, it has the advantage of high recording density and data transfer rate. However, there are two major drawbacks like 2-dimensional intersymbol interference and interpage interference as the density between pixels increases. Furthermore, a bright page that contains many ON pixels influences the reliable detection of the neighboring pages, which causes the less number of pages stored in the storage volume. We propose a sparse-ON pixel two-dimensional modulation code with the code rate 6/8 for increasing the number of pages stored in the volume. The proposed code is compared to conventional 6/8 balanced code, and it shows similar or a little bit better performance than that of the balanced code. Therefore, the proposed code can increase the recording capacity without loss of the performance.

Simulative Investigation of Spectral Amplitude Coding Based OCDMA System Using Quantum Logic Gate Code with NAND and Direct Detection Techniques

  • Sharma, Teena;Maddila, Ravi Kumar;Aljunid, Syed Alwee
    • Current Optics and Photonics
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    • v.3 no.6
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    • pp.531-540
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    • 2019
  • Spectral Amplitude Coding Optical Code Division Multiple Access (SAC OCDMA) is an advanced technique in asynchronous environments. This paper proposes design and implementation of a novel quantum logic gate (QLG) code, with code construction algorithm generated without following any code mapping procedures for SAC system. The proposed code has a unitary matrices property with maximum overlap of one chip for various clients and no overlaps in spectra for the rest of the subscribers. Results indicate that a single algorithm produces the same length increment for codes with weight greater than two and follows the same signal to noise ratio (SNR) and bit error rate (BER) calculations for a higher number of users. This paper further examines the performance of a QLG code based SAC-OCDMA system with NAND and direct detection techniques. BER analysis was carried out for the proposed code and results were compared with existing MDW, RD and GMP codes. We demonstrate that the QLG code based system performs better in terms of cardinality, which is followed by improved BER. Numerical analysis reveals that for error free transmission (10-9), the suggested code supports approximately 170 users with code weight 4. Our results also conclude that the proposed code provides improvement in the code construction, cross-correlation and minimization of noises.

A Sparse-ON Pixel Two-Dimensional 4-Level 4/6 Balanced-Modulation Code in Holographic Data Storage Systems (홀로그래픽 데이터 저장장치를 위한 저밀도 ON 픽셀 2차원 4-레벨 4/6 균형 변조부호)

  • Park, Keunhwan;Lee, Jaejin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.11
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    • pp.9-14
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    • 2016
  • In the holographic data storage system, the data can be stored more than one bit per pixel and the storage capacity and transmission rate can be increased. In this paper, we proposed a sparse-ON pixel 4/6 balanced-modulation code that the code rate is 1.33 (bit/pixel) with uniform page density. Even though the performance of the proposed sparse-ON pixel 4/6 balanced-code is similar to 2/3 and 6/9 modulation codes, it can increase the storage capacity more than these modulation codes and also store more pages in a volume by reducing the rate of ON pixels to mitigate IPI (inter-page interference).

Performance Analysis Based On Log-Likelihood Ratio in Orthogonal Code Hopping Multiplexing Systems Using Multiple Antennas (다중 안테나를 사용한 직교 부호 도약 다중화 시스템에서 로그 우도비 기반 성능 분석)

  • Jung, Bang-Chul;Sung, Kil-Young;Shin, Won-Yong
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.12
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    • pp.2534-2542
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    • 2011
  • In this paper, we show that performance can be improved by using multiple antennas in the conventional orthogonal code hopping multiplexing (OCHM) scheme, which was proposed for accommodating a larger number of users with low channel activities than the number of orthogonal codewords used in code division multiple access (CDMA)-based communication systems through downlink statistical multiplexing. First, we introduce two different types of OCHM systems together with orthogonal codeword allocation strategies, and then derive their mathematical expression for log-likelihood ratio (LLR) values according to the two different schemes. Next, when a turbo encoder based on the LLR computation is used, we evaluate performance on the frame error rate (FER) for the aformentioned OCHM system. For comparison, we also show performance for the existing symbol mapping method using multiple antennas, which was used in 3GPP standards. As a result, it is shown that our OCHM system with multiple antennas based on the proposed orthogonal codeword allocation strategy leads to performance gain over the conventional system---energy required to satisfy a target FER is significantly reduced.

A Low-Complexity Turbo coded BICM-ID System (Turbo coded BICM-ID의 복잡도 개선 기법)

  • Kang, Donghoon;Lee, Yongwook;Oh, Wangrok
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.8
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    • pp.21-27
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    • 2013
  • In this paper, we propose a low-complexity Turbo coded BICM-ID (bit-interleaved coded modulation with iterative decoding) system. A Turbo code is a powerful error correcting code with a BER (bit error rate) performance very close to the Shannon limit. In order to increase spectral efficiency of the Turbo code, a coded modulation combining Turbo code with high order modulation is used. The BER performance of Turbo-BICM can be improved by Turbo-BICM-ID using iterative demodulation and decoding algorithm. However, compared with Turbo-BICM, the decoding complexity of Turbo-BICM-ID is increased by exchanging information between decoder and demodulator. To reduce the decoding complexity of Turbo-BICM-ID, we propose a low-complexity Turbo-BICM-ID system. When compared with conventional Turbo-BICM-ID, the proposed scheme not only show similar BER performance but also reduce the decoding complexity.

Adaptive Multi-Rate(AMR) Speech Coding Algorithm (Adaptive Multi-Rate(AMR) 음성부호화 알고리즘)

  • 서정욱;배건성
    • Proceedings of the IEEK Conference
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    • 2000.06d
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    • pp.92-97
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    • 2000
  • An AMR(Adaptive Multi-Rate) speech coding algorithm has been adopted as a standard speech codec for IMT-2000. It is based on the algebraic CELP, and consists of eight speech coding modes having the bit rate from 4.75 kbit/s to 12.2 kbit/s. It also contains the VAD(Voice Activity Detector), SCR (Source Controlled Rate) operation, and error concealment scheme for robustness in a radio channel. The bit rate of AMR is changed on a frame basis depending on the channel condition. In this paper, we introduced AMR speech coding algorithm and performed the real-time implementation using TMS320C6201, i.e., a Texas Instrument's fixed-point DSP. With the ANSI C source code released from ETSI and 3GPP, we convert and optimize the program to make it run in real time using the C compiler and assembly language. It is verified that the decoded result of the implemented speech codec on the DSP is identical with the PC simulation result using ANSI C code for test sequences. Also, actual sound input/output test using microphone and speaker demonstrates its proper real-time operation without distortions or delays.

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Differential Code-Filtering Correlation Method for Adaptive Beamforming

  • Hefnawi Mostafa;Denidni Tayeb A.
    • Journal of Communications and Networks
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    • v.7 no.3
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    • pp.258-262
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    • 2005
  • An adaptive beamforming system based on code filtering and differential correlation approaches is proposed. The differential correlation method was originally proposed for time delay estimation of direct sequence code division multiple access (DS-CDMA) systems under near-far ratio conditions and the code filtering correlation algorithm, on the other hand, was proposed for array response estimation in DS-CDMA systems under perfect power control. In this paper, by combining differential correlation concept with the code filtering beamforming technology, an accurate estimate of the beam forming weights and an enhanced performance of DS-CDMA systems under sever near-far ratio conditions is achieved. The system performance in terms of beam pattern and bit-error-rate (HER) shows that the proposed adaptive beamformer outperforms the conventional code filtering correlation technique.