X-Code is one of the most important redundant array of independent disk （RAID）-6 codes which are capable of tolerating double disk failures. However, the code length of X-Code is restricted to be a prime number, and...X-Code is one of the most important redundant array of independent disk （RAID）-6 codes which are capable of tolerating double disk failures. However, the code length of X-Code is restricted to be a prime number, and such code length restriction of X-Code limits its usage in the real storage systems. Moreover, as a vertical RAID-6 code, X-Code can not be extended easily to an arbitrary code length like horizontal RAID-6 codes. In this paper, a novel and efficient code shortening algorithm for X-Code is proposed to extend X-Code to an arbitrary length. It can be further proved that the code shortening algorithm maintains the maximum-distance-separable （MDS） property of X-Code, and namely, the shortened X-Code is still MDS code with the optimal space efficiency. In the context of the shortening algorithm for X-Code, an in-depth performance analysis on X-Code at consecutive code lengths is conducted, and the impacts of the code shortening algorithm on the performance of X-Code in various performance metrics are revealed.展开更多
Focusing on the space-time coded multiuser mobile communication systems in the frequency-selective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time (V-BLAST) coded Multicarrier Code-Divi...Focusing on the space-time coded multiuser mobile communication systems in the frequency-selective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time (V-BLAST) coded Multicarrier Code-Division Multiple-Access (MC-CDMA) scheme and its blind channel identification algorithm. This algorithm employs an ESPRIT-like method and the singular value decomposition, and the channels between every transmit antenna of every user and every receive antenna of the base station are blindly estimated with a closed-form solution. Based on it, an equivalent Minimum Mean-Squared Error (MMSE) time-domain multiuser detector is derived. Moreover, the proposed scheme exploits the precoding in the transmitter in order to eliminate the constraint of more receive antennas than transmit ones, required by most conventional V-BLAST codec schemes. Computer simulation results demonstrate the validity of this proposed scheme.展开更多
Vertical array codes have less computational complexity and update complexity in comparison with horizontal array codes.However,the fault tolerance of the existing vertical array codes is in general lower than that of...Vertical array codes have less computational complexity and update complexity in comparison with horizontal array codes.However,the fault tolerance of the existing vertical array codes is in general lower than that of horizontal array codes.In addition,the cross-rack bandwidth is often the bottleneck of the update performance in erasure-coded storage systems.In this paper,we propose a cross-rack update(CRU)mechanism for vertical array codes intended to improve both the fault tolerance and update performance of erasure-coded storage systems.CRU builds on three parts:(i)stripe encoding,which can improve the fault tolerance of vertical code by encoding multiple sub-stripe;(ii)node grouping,which filters out the best combination of nodes to minimize cross-rack update traffic;(iii)selective logging,which can selectively log based on the location of data sub-blocks and parity sub-blocks to reduce disk I/O and cross-rack traffic.We evaluate CRU via trace-driven analysis and local cluster experiments.Evaluations show that CRU can significantly reduce cross-rack update traffic and improve system update throughput.展开更多
基金supported by the National Basic Research Program of China (Grant Nos.2011CB302300, 2011CB302301)the National High-Technology Research and Development Program of China (Grant Nos.2009AA01A401,2009AA01A402)+1 种基金the National Natural Science Foundation of China (Grant Nos.60873028, 60933002, 61025008)the Changjiang Innovation Group of Education of China (Grant No.IRT0725)
文摘X-Code is one of the most important redundant array of independent disk （RAID）-6 codes which are capable of tolerating double disk failures. However, the code length of X-Code is restricted to be a prime number, and such code length restriction of X-Code limits its usage in the real storage systems. Moreover, as a vertical RAID-6 code, X-Code can not be extended easily to an arbitrary code length like horizontal RAID-6 codes. In this paper, a novel and efficient code shortening algorithm for X-Code is proposed to extend X-Code to an arbitrary length. It can be further proved that the code shortening algorithm maintains the maximum-distance-separable （MDS） property of X-Code, and namely, the shortened X-Code is still MDS code with the optimal space efficiency. In the context of the shortening algorithm for X-Code, an in-depth performance analysis on X-Code at consecutive code lengths is conducted, and the impacts of the code shortening algorithm on the performance of X-Code in various performance metrics are revealed.
基金Partially supported by the National Natural Science Foundation of China (No.60502022)the Research Fund for Doctoral Program of Higher Education of China (No. 20020698024, No.20030698027)
文摘Focusing on the space-time coded multiuser mobile communication systems in the frequency-selective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time (V-BLAST) coded Multicarrier Code-Division Multiple-Access (MC-CDMA) scheme and its blind channel identification algorithm. This algorithm employs an ESPRIT-like method and the singular value decomposition, and the channels between every transmit antenna of every user and every receive antenna of the base station are blindly estimated with a closed-form solution. Based on it, an equivalent Minimum Mean-Squared Error (MMSE) time-domain multiuser detector is derived. Moreover, the proposed scheme exploits the precoding in the transmitter in order to eliminate the constraint of more receive antennas than transmit ones, required by most conventional V-BLAST codec schemes. Computer simulation results demonstrate the validity of this proposed scheme.
基金the National Key R&D Program of China under Grant 2020YFA0712300the National Natural Science Foundation of China under Grant 62071121。
文摘Vertical array codes have less computational complexity and update complexity in comparison with horizontal array codes.However,the fault tolerance of the existing vertical array codes is in general lower than that of horizontal array codes.In addition,the cross-rack bandwidth is often the bottleneck of the update performance in erasure-coded storage systems.In this paper,we propose a cross-rack update(CRU)mechanism for vertical array codes intended to improve both the fault tolerance and update performance of erasure-coded storage systems.CRU builds on three parts:(i)stripe encoding,which can improve the fault tolerance of vertical code by encoding multiple sub-stripe;(ii)node grouping,which filters out the best combination of nodes to minimize cross-rack update traffic;(iii)selective logging,which can selectively log based on the location of data sub-blocks and parity sub-blocks to reduce disk I/O and cross-rack traffic.We evaluate CRU via trace-driven analysis and local cluster experiments.Evaluations show that CRU can significantly reduce cross-rack update traffic and improve system update throughput.
