This paper combines improved Hamming codes and parity codes to assure the reliability of memory in presence of multiple bit upsets with low cost overhead.The redundancy bits of improved Hamming codes will be appended ...This paper combines improved Hamming codes and parity codes to assure the reliability of memory in presence of multiple bit upsets with low cost overhead.The redundancy bits of improved Hamming codes will be appended at the end of data bits,which eliminates the overhead of interspersing the redundancy bits at the encoder and decoder.The reliability of memory is further enhanced by the layout architecture of redundancy bits and data bits.The proposed scheme has been implemented in Verilog and synthesized using the Synopsys tools.The results reveal that the proposed method has about 19% less area penalties and 13% less power consumption comparing with the current two-dimensional error codes,and its latency of encoder and decoder is 63% less than that of Hamming codes.展开更多
Various index structures have recently been proposed to facilitate high-dimensional KNN queries, among which the techniques of approximate vector presentation and one-dimensional (1D) transformation can break the curs...Various index structures have recently been proposed to facilitate high-dimensional KNN queries, among which the techniques of approximate vector presentation and one-dimensional (1D) transformation can break the curse of dimensionality. Based on the two techniques above, a novel high-dimensional index is proposed, called Bit-code and Distance based index (BD). BD is based on a special partitioning strategy which is optimized for high-dimensional data. By the definitions of bit code and transformation function, a high-dimensional vector can be first approximately represented and then transformed into a 1D vector, the key managed by a B+-tree. A new KNN search algorithm is also proposed that exploits the bit code and distance to prune the search space more effectively. Results of extensive experiments using both synthetic and real data demonstrated that BD out- performs the existing index structures for KNN search in high-dimensional spaces.展开更多
We study the impact of various modulation mapping strategies and signal constellation shapes on the se- crecy rates achievable with bit-interleaved coded modulation (BICM) schemes. Transmission over an ergodic Rayle...We study the impact of various modulation mapping strategies and signal constellation shapes on the se- crecy rates achievable with bit-interleaved coded modulation (BICM) schemes. Transmission over an ergodic Rayleigh fading channel is assumed throughout this work. Various constellations and mapping techniques are considered in this work to maximize the capacity difference between the main channel and the eavesdropper channel, rather than to opti- mize the capacity of both channels. We show that in terms of achievable secrecy rate, Gray and Quasi-Gray mappings only perform Well at low SNR but outperformed by other mapping techniques when SNR increases. The proper design of signal mapping can significantly enhance the achievable secrecy rate in BICM schemes. It is indicated that the key parameter to the secrecy rate of a BICM system is the distance spectrum of Euclidean distances for mappings.展开更多
Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is a bandwidth ef- ficient transmission, where the bit error rate is reduced through the iterative information exchange between the inner demapper and...Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is a bandwidth ef- ficient transmission, where the bit error rate is reduced through the iterative information exchange between the inner demapper and the outer decoder. The choice of the symbol mapping is the crucial design parameter. This paper indicates that the Harmonic Mean of the Minimum Squared Euclidean (HMMSE) distance is the best criterion for the mapping design. Based on the design criterion of the HMMSE distance, a new search algorithm to find the optimized labeling maps for BICM-ID system is proposed. Numerical results and performance comparison show that the new labeling search method has a low complexity and outperforms other labeling schemes using other design criterion in BICM-ID system, therefore it is an optimized labeling method.展开更多
利用混合激励线性预测(mixed excitation linear prediction,MELP)算法和码激励线性预测(code excitation linear prediction,CELP)算法的优点,提出了一种混合MELP/CELP语音编码模型。编码端对强浊音帧采用MELP编码,对弱浊音帧和清音帧...利用混合激励线性预测(mixed excitation linear prediction,MELP)算法和码激励线性预测(code excitation linear prediction,CELP)算法的优点,提出了一种混合MELP/CELP语音编码模型。编码端对强浊音帧采用MELP编码,对弱浊音帧和清音帧进行CELP编码。MELP编码器采用相位对齐技术提取强浊音帧的相位参数,解决了合成语音与原始语音在时间上不同步的问题。对实现的4 kbit/s混合MELP/CELP声码器进行客观MOS(mean opinion score)值和主观DRT(diagnostic rhythm test)清晰度测试,结果表明,该声码器的合成语音具有较高的可懂度和清晰度。展开更多
为了研究不同码型的卷积码在水下湍流信道中的误码率(BER)性能,采用接受-拒绝采样模拟湍流信道乘性干扰,并选择二进制相移键控(BPSK)调制方式,建立Gamma-Gamma湍流信道通信系统仿真模型。仿真结果表明:在不同强度的湍流信道中,采用卷积...为了研究不同码型的卷积码在水下湍流信道中的误码率(BER)性能,采用接受-拒绝采样模拟湍流信道乘性干扰,并选择二进制相移键控(BPSK)调制方式,建立Gamma-Gamma湍流信道通信系统仿真模型。仿真结果表明:在不同强度的湍流信道中,采用卷积码编码均能提升系统的BER性能;卷积码的码率越小,系统BER性能提升越显著;随着信噪比(SNR)增大,记忆深度越长,系统BER下降速度越快;采用软译码比采用硬译码时增益至少提升2.82 d B;卷积码的解码不仅受当前信息的影响,还与之前的码元信息有关。展开更多
In Digital Radio Mondiale (DRM) system, achieving good audio quality becomes a challenge due to its limited band-width of 9 or 10kHz and the very bad fading channels. Therefore, DRM needs highly efficient channel codi...In Digital Radio Mondiale (DRM) system, achieving good audio quality becomes a challenge due to its limited band-width of 9 or 10kHz and the very bad fading channels. Therefore, DRM needs highly efficient channel coding schemes. This paper, proposes the schemes which use the Low-Density Parity-Check (LDPC) coded Bit-Interleaved Coded Modulation (BICM) schemes for the implementation of DRM systems. Simulation results show that the proposed system is more efficient than the Rate Compatible Punctured Con volutional (RCPC) coded DRM system on various broadcast channels, and may be recommended as a coding technology for Digital Amplitude Modulation Broadcasting (DAMB) systems of China.展开更多
In order to improve the bit error rate(BER) performance of turbo codes with short frame size at a wide range of signal to noise ratio(SNR),a new method by optimizing the bit energy is proposed.At first,a formula deriv...In order to improve the bit error rate(BER) performance of turbo codes with short frame size at a wide range of signal to noise ratio(SNR),a new method by optimizing the bit energy is proposed.At first,a formula derived from the Union Bound is introduced.It describes the relations between the bit error rate distribution and the minimum weight distribution.And then,by mathematically optimizing the formula,the energy for every bit of the codeword is optimized to achieve the minimum BER at high SNR region.At last,an adjustable parameter is employed to compensate the degradations of BER at low and moderate SNR regions.Case studies indicate that the improvements of BER for turbo codes with short frame size are significant at a wide range of SNR.展开更多
Information embodied in machine component classification codes has internal relation with the probability distribu- tion of the code symbol. This paper presents a model considering codes as information source based on...Information embodied in machine component classification codes has internal relation with the probability distribu- tion of the code symbol. This paper presents a model considering codes as information source based on Shannon’s information theory. Using information entropy, it preserves the mathematical form and quantitatively measures the information amount of a symbol and a bit in the machine component classification coding system. It also gets the maximum value of information amount and the corresponding coding scheme when the category of symbols is fixed. Samples are given to show how to evaluate the information amount of component codes and how to optimize a coding system.展开更多
基金Sponsored by the Opening Project of National Key Laboratory of Science and Technology on Reliability PhysicsApplication Technology of Electrical Component(Grant No.ZHD200903)
文摘This paper combines improved Hamming codes and parity codes to assure the reliability of memory in presence of multiple bit upsets with low cost overhead.The redundancy bits of improved Hamming codes will be appended at the end of data bits,which eliminates the overhead of interspersing the redundancy bits at the encoder and decoder.The reliability of memory is further enhanced by the layout architecture of redundancy bits and data bits.The proposed scheme has been implemented in Verilog and synthesized using the Synopsys tools.The results reveal that the proposed method has about 19% less area penalties and 13% less power consumption comparing with the current two-dimensional error codes,and its latency of encoder and decoder is 63% less than that of Hamming codes.
基金Project (No. [2005]555) supported by the Hi-Tech Research and De-velopment Program (863) of China
文摘Various index structures have recently been proposed to facilitate high-dimensional KNN queries, among which the techniques of approximate vector presentation and one-dimensional (1D) transformation can break the curse of dimensionality. Based on the two techniques above, a novel high-dimensional index is proposed, called Bit-code and Distance based index (BD). BD is based on a special partitioning strategy which is optimized for high-dimensional data. By the definitions of bit code and transformation function, a high-dimensional vector can be first approximately represented and then transformed into a 1D vector, the key managed by a B+-tree. A new KNN search algorithm is also proposed that exploits the bit code and distance to prune the search space more effectively. Results of extensive experiments using both synthetic and real data demonstrated that BD out- performs the existing index structures for KNN search in high-dimensional spaces.
文摘We study the impact of various modulation mapping strategies and signal constellation shapes on the se- crecy rates achievable with bit-interleaved coded modulation (BICM) schemes. Transmission over an ergodic Rayleigh fading channel is assumed throughout this work. Various constellations and mapping techniques are considered in this work to maximize the capacity difference between the main channel and the eavesdropper channel, rather than to opti- mize the capacity of both channels. We show that in terms of achievable secrecy rate, Gray and Quasi-Gray mappings only perform Well at low SNR but outperformed by other mapping techniques when SNR increases. The proper design of signal mapping can significantly enhance the achievable secrecy rate in BICM schemes. It is indicated that the key parameter to the secrecy rate of a BICM system is the distance spectrum of Euclidean distances for mappings.
基金Supported by the National Natural Science Foundation of China (No.60472104).
文摘Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is a bandwidth ef- ficient transmission, where the bit error rate is reduced through the iterative information exchange between the inner demapper and the outer decoder. The choice of the symbol mapping is the crucial design parameter. This paper indicates that the Harmonic Mean of the Minimum Squared Euclidean (HMMSE) distance is the best criterion for the mapping design. Based on the design criterion of the HMMSE distance, a new search algorithm to find the optimized labeling maps for BICM-ID system is proposed. Numerical results and performance comparison show that the new labeling search method has a low complexity and outperforms other labeling schemes using other design criterion in BICM-ID system, therefore it is an optimized labeling method.
文摘为了研究不同码型的卷积码在水下湍流信道中的误码率(BER)性能,采用接受-拒绝采样模拟湍流信道乘性干扰,并选择二进制相移键控(BPSK)调制方式,建立Gamma-Gamma湍流信道通信系统仿真模型。仿真结果表明:在不同强度的湍流信道中,采用卷积码编码均能提升系统的BER性能;卷积码的码率越小,系统BER性能提升越显著;随着信噪比(SNR)增大,记忆深度越长,系统BER下降速度越快;采用软译码比采用硬译码时增益至少提升2.82 d B;卷积码的解码不仅受当前信息的影响,还与之前的码元信息有关。
基金Supported by the National Natural Science Foundation of China(No.60072013).
文摘In Digital Radio Mondiale (DRM) system, achieving good audio quality becomes a challenge due to its limited band-width of 9 or 10kHz and the very bad fading channels. Therefore, DRM needs highly efficient channel coding schemes. This paper, proposes the schemes which use the Low-Density Parity-Check (LDPC) coded Bit-Interleaved Coded Modulation (BICM) schemes for the implementation of DRM systems. Simulation results show that the proposed system is more efficient than the Rate Compatible Punctured Con volutional (RCPC) coded DRM system on various broadcast channels, and may be recommended as a coding technology for Digital Amplitude Modulation Broadcasting (DAMB) systems of China.
基金Supported by the National High Technology Research and Development Programme of China(No.2014AA01A705)the National Natural Science Foundation of China(U1204607)
文摘In order to improve the bit error rate(BER) performance of turbo codes with short frame size at a wide range of signal to noise ratio(SNR),a new method by optimizing the bit energy is proposed.At first,a formula derived from the Union Bound is introduced.It describes the relations between the bit error rate distribution and the minimum weight distribution.And then,by mathematically optimizing the formula,the energy for every bit of the codeword is optimized to achieve the minimum BER at high SNR region.At last,an adjustable parameter is employed to compensate the degradations of BER at low and moderate SNR regions.Case studies indicate that the improvements of BER for turbo codes with short frame size are significant at a wide range of SNR.
基金Projects supported by the Hi-Tech Research and Development Pro-gram (863) of China (No. 2004AA84ts03) and the Science and Technology Committee of Zhejiang Province (No. 2004C31018), China
文摘Information embodied in machine component classification codes has internal relation with the probability distribu- tion of the code symbol. This paper presents a model considering codes as information source based on Shannon’s information theory. Using information entropy, it preserves the mathematical form and quantitatively measures the information amount of a symbol and a bit in the machine component classification coding system. It also gets the maximum value of information amount and the corresponding coding scheme when the category of symbols is fixed. Samples are given to show how to evaluate the information amount of component codes and how to optimize a coding system.