This paper proposes a family of raptor-like rate-compatible spatially coupled low-density parity-check(RL-RC-SC-LDPC)codes from RL-RC-LDPC block codes.There are two important keys.One is the performance of the base ma...This paper proposes a family of raptor-like rate-compatible spatially coupled low-density parity-check(RL-RC-SC-LDPC)codes from RL-RC-LDPC block codes.There are two important keys.One is the performance of the base matrix.RL-LDPC codes have been adopted in the technical specification of 5G new radio(5G-NR).We use the 5G NR LDPC code as the base matrix.The other is the edge coupling design.In this regard,we have designed a rate-compatible coupling algorithm,which can improve performance under multiple code rates.The constructed RL-RC-SC-LDPC code property requires a large coupling length L and thus we improved the reciprocal channel approximation(RCA)algorithm and proposed a sliding window RCA algorithm.It can provide lower com-plexity and latency than RCA algorithm.The code family shows improved thresholds close to the Shannon limit and finite-length performance compared with 5G NR LDPC codes for the additive white Gaussian noise(AWGN)channel.展开更多
Due to its high efficiency, high precision and high flexibility, CNC lathe is widely used in the machinery manufacturing industry increasingly, and becomes one of CNC machine too[s that most widely used. However, to g...Due to its high efficiency, high precision and high flexibility, CNC lathe is widely used in the machinery manufacturing industry increasingly, and becomes one of CNC machine too[s that most widely used. However, to give full play to the role of CNC lathes, the key is programme, that is, preparing the reasonable and efficient processing procedures depending on the features and precision parts. This paper discussed the problems of programming and processing techniques of the CNC lathe parts.展开更多
Machine embroidery is a multi-step process with many variables that govern the quality of the final product.In Sri Lanka a few large-scale factories use machine embroidery process.They import heavy and very expensive ...Machine embroidery is a multi-step process with many variables that govern the quality of the final product.In Sri Lanka a few large-scale factories use machine embroidery process.They import heavy and very expensive machines from the other countries in the world.The main disadvantage of these machines is,they are not suitable for production of small order quantities due to high cost.Also,these machines and the required software for the designing and operating process are comparatively expensive.Small scale apparel factories and domestic industrialists cannot afford the high cost of hardware and software.Besides,it requires persons with high skills for design,operation and maintenance.There are a few domestic type automated embroidery machines,but those are exorbitant.The present study aims to design and fabricate retrofit for ordinary sewing machine that is capable of performing given embroidery pattern.The retrofit comprises of an frame which can be moved in X and Y directions by three controlling motors.The design of the embroidery is converted to a G-code using GBRL software and then the microcontroller governs the movement of the frame to produce the embroidery.The retrofit designed and developed performed embroidery function and the quality of the output was checked and it was found to be satisfactory as far as first conceptual model is concerned.Further development work is required to improve user requirements and technical requirements including the increase of speed of operation which may be done with synchronization of the three motors.展开更多
In this paper,we propose a transmission scheme for uplink and downlink transmissions,where the fifth generation(5G)low-density parity-check(LDPC)codes are implemented for error correction.In the proposed scheme,the ac...In this paper,we propose a transmission scheme for uplink and downlink transmissions,where the fifth generation(5G)low-density parity-check(LDPC)codes are implemented for error correction.In the proposed scheme,the acknowledgment(ACK)or negative acknowledgment(NACK)feedback information is transmitted along with the payload data by cyclically shifting coded sequence,while the re-transmitted codewords are superimposed(XORed)partially on the current codewords.The distinguished feature of the proposed transmission scheme is that it requires neither extra transmission bandwidth nor extra transmission power.We also propose to truncate the error patterns for the purpose of reducing the implementation complexity and reducing the error propagation.Numerical results show that the proposed scheme significantly outperforms conventional LDPC-coded transmission.For the 5G LDPC code with length 1920 at the signal-to-noise ratio(SNR)of 1.3 dB,the word error rate(WER)of the data transmitted by the proposed scheme is about 10^(−4),while that of the conventional LDPC-coded transmission is about 10^(−2).展开更多
文摘This paper proposes a family of raptor-like rate-compatible spatially coupled low-density parity-check(RL-RC-SC-LDPC)codes from RL-RC-LDPC block codes.There are two important keys.One is the performance of the base matrix.RL-LDPC codes have been adopted in the technical specification of 5G new radio(5G-NR).We use the 5G NR LDPC code as the base matrix.The other is the edge coupling design.In this regard,we have designed a rate-compatible coupling algorithm,which can improve performance under multiple code rates.The constructed RL-RC-SC-LDPC code property requires a large coupling length L and thus we improved the reciprocal channel approximation(RCA)algorithm and proposed a sliding window RCA algorithm.It can provide lower com-plexity and latency than RCA algorithm.The code family shows improved thresholds close to the Shannon limit and finite-length performance compared with 5G NR LDPC codes for the additive white Gaussian noise(AWGN)channel.
文摘Due to its high efficiency, high precision and high flexibility, CNC lathe is widely used in the machinery manufacturing industry increasingly, and becomes one of CNC machine too[s that most widely used. However, to give full play to the role of CNC lathes, the key is programme, that is, preparing the reasonable and efficient processing procedures depending on the features and precision parts. This paper discussed the problems of programming and processing techniques of the CNC lathe parts.
文摘Machine embroidery is a multi-step process with many variables that govern the quality of the final product.In Sri Lanka a few large-scale factories use machine embroidery process.They import heavy and very expensive machines from the other countries in the world.The main disadvantage of these machines is,they are not suitable for production of small order quantities due to high cost.Also,these machines and the required software for the designing and operating process are comparatively expensive.Small scale apparel factories and domestic industrialists cannot afford the high cost of hardware and software.Besides,it requires persons with high skills for design,operation and maintenance.There are a few domestic type automated embroidery machines,but those are exorbitant.The present study aims to design and fabricate retrofit for ordinary sewing machine that is capable of performing given embroidery pattern.The retrofit comprises of an frame which can be moved in X and Y directions by three controlling motors.The design of the embroidery is converted to a G-code using GBRL software and then the microcontroller governs the movement of the frame to produce the embroidery.The retrofit designed and developed performed embroidery function and the quality of the output was checked and it was found to be satisfactory as far as first conceptual model is concerned.Further development work is required to improve user requirements and technical requirements including the increase of speed of operation which may be done with synchronization of the three motors.
基金supported by National Key R&D Program of China(No.2020YFB1807100)the National Natural Science Foundation of China(No.61971454).
文摘In this paper,we propose a transmission scheme for uplink and downlink transmissions,where the fifth generation(5G)low-density parity-check(LDPC)codes are implemented for error correction.In the proposed scheme,the acknowledgment(ACK)or negative acknowledgment(NACK)feedback information is transmitted along with the payload data by cyclically shifting coded sequence,while the re-transmitted codewords are superimposed(XORed)partially on the current codewords.The distinguished feature of the proposed transmission scheme is that it requires neither extra transmission bandwidth nor extra transmission power.We also propose to truncate the error patterns for the purpose of reducing the implementation complexity and reducing the error propagation.Numerical results show that the proposed scheme significantly outperforms conventional LDPC-coded transmission.For the 5G LDPC code with length 1920 at the signal-to-noise ratio(SNR)of 1.3 dB,the word error rate(WER)of the data transmitted by the proposed scheme is about 10^(−4),while that of the conventional LDPC-coded transmission is about 10^(−2).
