改进高速率全分集准正交差分空时码方案

传统的方案中,将准正交空时码(quasi-orthogonal space-time code)经过调制之后转换为酉空时码(unitary space-time code)再进行差分编码,但信息传输速率的提高会带来性能的严重下降。为了克服传统方案这一不足,给出一种引入幅值的修正方案,并且对幅值的选取也进行了说明。与传统的准正交差分空时码相比,所提方案提高了其信息传输速率,对误比特性能和信息传输速率进行了一个较好的折中。     

一种新型的多维Turbo码联合交织器设计

Turbo码由于具有逼近香农信道容量限的性能,已经被CDMA2000协议采纳。交织器是Turbo码的关键组成部分,也是影响其性能的关键因素。针对原S随机联合交织器设计存在的存储空间大、计算复杂度高、运算时间长的问题,提出了一种与原方案设计准则相同、新型的点对点设计方案,在保证原性能不损失的前提下,存储空间减少到原有方案的2/N2,计算复杂度也大为降低,适用于实际应用。     

A bound on the minimum distance of generalized quasi-twisted codes

Generalized quasi-twisted (GQT) codes form a generalization of quasi-twisted (QT) codes and generalized quasi-cyclic (GQC) codes. By the Chinese remainder theorem, the GQT codes can be decomposed into a direct sum of some linear codes over Galois extension fields, which leads to the trace representation of the GQT codes. Using this trace representation, we first prove the minimum distance bound for GQT codes with two constituents. Then we generalize the result to GQT codes with s constituents. Finally, we present some examples to show that the bound is better than the well-known Esmaeili-Yari bound and sharp in many instances.     

环GR(4,2)上一类负循环码的Gray象

研究了GR(4,2)上长为2~s的负循环码的Gray象,证明了GR(4,2)上长为2~s的负循环码的Gray象是F_4上长为2~(s+2)指数为2的准循环码.通过计算GR(2~a,m)上长为2~s的负循环码的齐次距离,确定了GR(4,2)上长为2~s的负循环码的Gray象的汉明距离.     

Performance of multi level‐turbo coding with neural network‐based channel estimation over WSSUS MIMO channels

This paper presents the performance of the transmit diversity‐multi level turbo codes (TD‐MLTC) over the multiple‐input–multiple‐output (MIMO) channels based on the wide sense stationary uncorrelated scattering (WSSUS). The multi level‐turbo code (ML‐TC) system contains more than one turbo encoder/decoder block in its structure. At the transmitter side, the ML‐TC uses the group partitioning technique that partitions a signal set into several levels and encodes each level separately by a proper component of the encoder to improve error performance. The binary input sequence is passed through the MLTC encoder and mapped to 4‐PSK and then fed into the transmit diversity scheme for high data transmission over wireless fading channels. At the receiver side, distorted multi‐path signals are received by multiple receiver antennae. WSSUS MIMO channel parameters are estimated by using an artificial neural network and an iterative combiner. Input sequence of the first level of the MLTC encoder is estimated at the first level of MLTC decoder. Subsequently, the other input sequences are computed by using the estimated input bit streams of the previous levels. 4‐PSK two‐level turbo codes are simulated for 2T_x?1R_x and 2T_x?2R_x antenna configurations over WSSUS MIMO channels. Here, TD‐MLTC and its efficient implementations are discussed and simulation results are given. Copyright © 2008 John Wiley & Sons, Ltd.     

一种线性分组码的查表译码法及其应用

针对纠正两个随机错误的线性分组码,采用重复查表译码法,通过多次查询含一个错误的伴随式与错误图样的译码表,实现了一种占有很少存储空间的查表译码算法。该算法在码长较短时译码的计算量较少,可适用于利用单片机等低运算能力情况下的通信应用中。文中对纠正2个错误的（26,16）缩短循环码的译码进行了实现,验证了算法的可行性。     

Peterson–Gorenstein–Zierler algorithm for skew RS codes

We design a non-commutative version of the Peterson–Gorenstein–Zierler decoding algorithm for a class of codes that we call skew RS codes. These codes are left ideals of a quotient of a skew polynomial ring, which endow them of a sort of non-commutative cyclic structure. Since we work over an arbitrary field, our techniques may be applied both to linear block codes and convolutional codes. In particular, our decoding algorithm applies for block codes beyond the classical cyclic case.     

基于Windows的考试系统的研究与实现

设计并实现了一种基于Windows操作平台的考试系统.该系统由考试和阅卷2个相对独立的部分构成,实现了考试与阅卷的分离.考试系统的题型为单选题、多选题、填空题和操作题,可以用在含此类题型的各种考试中.该系统采用Visual Basic 6.0实现界面设计和代码编写,后台数据库采用的是Microsoft Access.该系统在本校两年期末考试中使用过,效果良好.     

Crooked binomials

A function f : GF(2 ^r ) → GF(2 ^r ) is called crooked if the sets {f(x) + f(x + a)|x ∈ GF(2 ^r )} is an affine hyperplane for any nonzero a ∈ GF(2 ^r ). We prove that a crooked binomial function f(x) = x ^d + ux ^e defined on GF(2 ^r ) satisfies that both exponents d, e have 2-weights at most 2.