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A class of quasi-cyclic LDPC codes from B2 （mod m） sequences

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Science china(Information Sciences) 2011年第8期54卷 1645-1653页

作者： ZHANG GuoHua & WANG xinMei state key laboratory of integrated Service network,xidian university,xi’an 710071,china state key laboratory of integrated Service network Xidian University Xi’an China

A new class of binary low-density parity-check (LDPC) codes is proposed based on B 2 (mod m) sequences. The parity-check matrix of such a code has a column weight of three and a row weight of an arbitrary integer,and a quasi-cyclic *** parity-check matrix also has a girth at least 8,and corresponds to a code with minimal distance at least *** m is prime,an 8-cycles reduction method is presented to completely avoid the two types of 8-cycles within the total four types existed in the Tanner *** results show that,for a prime integer m,the new LDPC code outperforms the random (quasi-) regular counterpart generated by the PEG ***,a heuristic algorithm based on a strategy called neighboring extension search is presented to search for the B 2 (mod m) sequences whose lengths approach or meet the upper bound.

关键词： channel coding LDPC code B2 (mod m) sequencegirth

A network coding based hybrid ARQ algorithm for wireless video broadcast

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Science china(Information Sciences) 2011年第6期54卷 1327-1332页

作者： LU Ji , WU ChengKe, xiAO Song & DU JianChao state key laboratory of integrated services network, xidian university, xi’an 710071, china state key laboratory of integrated services network Xidian University Xi’an China

This paper proposes a network coding (NC) based hybrid ARQ (HARQ) algorithm for video broad- cast over wireless networks. The sender applies NC technique to combine the lost packets of different terminals, so that multiple terminals can recover their lost packets via per transmission from the sender. The proposed algorithm combines the advantage of FEC scheme and NC based ARQ scheme so as to maximize not only wireless throughput but also video quality for broadcast communication. Simulation results show that our algorithm significantly improves both wireless throughput efficiency and video quality, compared with ARQ and HARQ schemes.

关键词： wireless networks network coding hybrid ARQ video transmission

Threshold proxy quantum signature scheme with threshold shared verification

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Science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3,4 & WEN QiaoYan2 1 College of Computer Science and Technology,Beijing university of Technology,Beijing 100124,china 2.state key laboratory of networking and Switching Technology,Beijing university of Posts and Tele-communications,Beijing 100876,china 3 state key laboratory of integrated services network,xidian university,xi’an 710071,china 4 state key laboratory of Information Security(Graduate university of Chinese Academy of Sciences) ,Beijing 100049,china College of Computer Science and Technology Beijing University of Technology Beijing China state key laboratory of integrated services network Xidian University Xi’an China state key laboratory of Information Security (Graduate university of Chinese Academy of Sciences) Beijing China state key laboratory of networking and Switching Technology Beijing University of Posts and Telecommunications Beijing China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

Quantum threshold group signature

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Science china(Physics,Mechanics & Astronomy) 2008年第10期51卷 1505-1514页

作者： YANG YuGuang1,2,3 & WEN QiaoYan4 1 College of Computer Science and Technology, Beijing university of Technology, Beijing 100124, china 2.state key laboratory of integrated services network, xidian university, xi’an 710071, china 3 state key laboratory of Information Security (Graduate university of Chinese Academy of Sciences), Beijing 100049, china 4 state key laboratory of networking and Switching Technology, Beijing university of Posts and Tele-communications, Beijing 100876, china College of Computer Science and Technology Beijing University of Technology Beijing China state key laboratory of integrated services network Xidian University Xi’an China state key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing China state key laboratory of networking and Switching Technology Beijing University of Posts and Telecommunications Beijing China

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

关键词： threshold quantum signature trusted party quantum cryptography

Threshold quantum secret sharing between multi-party and multi-party

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2,3 & WEN QiaoYan4 1 College of Computer Science and Technology,Beijing university of Technology,Beijing 100124,china 2.state key laboratory of integrated services network,xidian university,xi’an 710071,china 3 state key laboratory of Information Security (Graduate university of Chinese Academy of Sciences),Beijing 100049,china 4 state key laboratory of networking and Switching Technology,Beijing university of Posts and Tele-communications,Beijing 100876,china College of Computer Science and Technology Beijing University of Technology Beijing China state key laboratory of integrated services network Xidian University Xi’an China state key laboratory of Information Security (Graduate university of Chinese Academy of Sciences) Beijing China state key laboratory of networking and Switching Technology Beijing University of Posts and Telecommunications Beijing China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

Space-time cooperative diversity scheme using full feedback

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The Journal of china Universities of Posts and Telecommunications 2009年第3期16卷 8-13页

作者： SUN De-chun,YI Ke-chu,LI xiao-hui state key laboratory of integrated Service networks,xidian university,xi’an 710071,china state key laboratory of integrated Service networks Xidian University Xi'an 710071 china

This article proposes a new space-time cooperative diversity scheme called full feedback-based cooperative diversity scheme （FFBCD）. In contrast to the conventional adaptive space-time cooperative diversity schemes that utilize the feedback from only the destination node, the new scheme utilizes the feedback from both the destination node and the cooperation node. With the feedback from the destination node, the occasional successful reception of the destination node in the information distribution stage can be detected, thus avoiding unnecessary retransmissions in the information delivery stage. The feedback from the cooperation node indicates the receiving state of the cooperation node in the information distribution stage, and the source node and the cooperation node will not perform cooperative retransmission during the information delivery stage unless the cooperation node is received successfully in the information distribution stage. In this way the new scheme can reduce the number of transmission attempt and improve the channel utilization. The expressions of the average number of transmission attempt are given. Numerical approximations and simulation results both show that the new scheme performs better than the non-cooperative scheme and the conventional adaptive space-time cooperative diversity scheme.

关键词： space-time cooperative diversity simple feedback adaptive cooperative diversity transmission attempt

Exact thresholds for low-density parity-check codes over the binary erasure channel

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Progress in Natural Science:Materials International 2009年第7期19卷 897-900页

作者： Jianjun Mu a, xiaopeng Jiao a, xinmei Wangb a School of Computer Science and Technology, xidian university, xi’an 710071, china b state key laboratory of integrated Service networks, xidian university, xi’an 710071, china School of Computer Science and Technology Xidian University Xi’an 710071 China state key laboratory of integrated Service networks Xidian University Xi’an 710071 China

A simple method for determining the threshold of irregular LDPC codes over the binary erasure channel (BEC) under message-passing decoding is proposed. An exact formula for calculating the threshold of irregular LDPC codes over the BEC is proved. This generalizes the known result on the threshold of regular LDPC codes to irregular LDPC codes. Moreover, our new method can avoid the computation of the inverse of the degree distribution function for irregular LDPC codes. Numerical results demonstrate the correctness of our proposed method.

关键词： Binary erasure channel (BEC) LDPC codes Threshold

Pair-wise error probability and its Chernoff upper bound for unitary space-time code

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Science china(Information Sciences) 2010年第8期53卷 1613-1621页

作者： ZHANG DaPeng 1,2 , LIU Ju 1 , XU HongJi 1 & JI Hui 1 1 School of Information Science and Engineering, Shandong university, Jinan 250100, china 2.state key laboratory of integrated services networks, xidian university, xi’an 710071, china School of Information Science and Engineering Shandong University Jinan China state key laboratory of integrated services networks Xidian University Xi’an China

Unitary space-time code is ideally suited for rapid fading scenarios as it can operate well without channel state information (CSI), which is of vital significance for improving the effectivity and reliability of wireless communication systems. Pair-wise error probability (PEP) is an important factor for studying the reliability of a communication system. However, the existing scheme only gives the final result of PEP and the corresponding Chernoff upper bound (CUB) is obtained through magnification, which is not of universal significance for this kind of problems. In this paper, we employ the log-likelihood ratio of probability density functions of the received signals conditioned on the two possibly transmitted signals and by virtue of moment generating function we give the details in deriving the final precise residue expression for PEP and its CUB. At last, we verify the above results by simulations.

关键词： multiple-input multiple-output space-time code unitary space-time code pair-wise error probability Chernoff upper bound

Optimal user scheduling and power control in multi-user cognitive broadcast systems

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Science china(Information Sciences) 2012年第6期55卷 1402-1414页

作者： WANG QunHuan 1,2,3,WANG HuiMing 1,2,3 & YIN QinYe 1,3 1 School of Electronic and Information Engineering,xi'an Jiaotong university,xi'an 710049,china 2.state key Lab for integrated services networks,xidian university,xi'an 710071,china 3 Ministry of Education key Lab for Intelligent networks and network Security,xi'an Jiaotong university,xi'an 710071,china. School of Electronic and Information Engineering Xi’an Jiaotong University Xi’an China state key Lab for integrated services networks Xidian University Xi’an China Ministry of Education key Lab for Intelligent networks and network Security Xi’an Jiaotong University Xi’an China

Cognitive radio systems should not only have the ability to sense and exploit "frequency spectrum holes",but also the ability to sense and utilize "spatial spectrum holes".In this paper,we consider the issue of maximizing the throughput of the cognitive systems by fully utilizing "spatial spectrum holes" brought in by multiple cognitive users,in the scenario where a pair of licensed users and a cognitive broadcast system share multiple spectrum *** exploiting the channel reciprocity under the premise that the licensed system adopts the time-division-duplexing (TDD) mode,we propose a more practical cognitive access scheme that can sense the interference at the licensed user caused by the cognitive transmitter,based on the existing feedback signals from the licensed user to the licensed base *** both interferences from the licensed base station to the cognitive receiver and from the cognitive transmitter to the licensed user into consideration,we investigate the optimal user scheduling and power allocation scheme that can maximize the ergodic sum rate of the cognitive *** show that scheduling the user whose channel gain to interference and noise ratio (CGINR) is the largest for each frequency band is *** also derive the dynamic power allocation scheme meeting the three practical constraints,i.e.,the transmitter's average transmission power constraint,the power amplifier's instantaneous transmission power constraint,and the interference power constraint at the licensed *** result shows that in different coherent time intervals and different frequency bands,the power allocation has a multi-level waterfilling *** analysis shows that the strategy scheduling user with the largest CGINR introduces significant performance improvement compared with the traditional strategy scheduling user with the largest channel gain to noise ratio (CGNR).We also illustrate the impact of power constraints and the number of users on system p

关键词： cognitive radio distributed spatial spectrum holes opportunistic scheduling power allocation