State-assignment technique for synchronous sequential machines

The letter presents a new state-assignment technique for synchronous sequential machines. The method makes use of the shortest clearing sequence of each state in assigning a binary code for that state. A clearing sequence is defined as a sequence of inputs which will bring a sequential machine to the same predefined state, no matter which state the sequential machine starts from. The method of state assignment described in the letter shows the shift-register properties of the sequential machine. The stronger these properties are, the simpler the realisation.     

Buffered stack memory organisation

Slow unidirectional shift registers can be used to realise a large-size inexpensive stack. A simple configuration of such a shift-register stack will frequently force a processing unit needing access to it into an idle state. In the letter, a scheme using a small number of fast bidirectional shift registers appended to a unidirectional shift-register stack is suggested. This configuration makes the entire stack look, for most of the time, as if it were made of fast bidirectional shift registers. A design method is presented to determine the number of bits needed in the bidirectional shift register to meet given specifications.     

卷积码编码原理的解释

现有的信息论与编码教材在介绍卷积码编码时通常是直接给出码的生成多项式或编码器的移位寄存器实现,没有将编码原理和卷积相联系.本文从离散时间系统引出卷积码编码器的移位寄存器实现,深入浅出地阐明了码生成多项式矩阵的由来及其重要性,同时采用计算离散时间序列卷积的方法求解编码输出序列,从而对卷积码编码的原理以及卷积二字的含义给予了更精准的解释和验证.     

Distributive Pilot Arrangement Based on Modified M-sequences for OFDM Intercarrier Interference Estimation

The intercarrier interference (ICI) matrix for the orthogonal frequency division multiplexing systems usually has a fairly large dimension and changes over time for mobile communications. In this paper, we design the modified maximum-length shift-register sequences and propose a new distributive allocation scheme together with a linear interpolation for both pilot-aided and non-pilot-aided ICI vector estimates; this new method can combat the realistic non-circulant ICI matrix problem, where almost all other existing schemes could not perform effectively. Monte Carlo experiments show the significant advantages of our new ICI matrix estimator especially when the signal-to-noise ratio is larger than 15 dB     

Condition for the nonsingularity of a feedback shift-register over a general finite field (Corresp.)

The necessary and sufficient condition for a feedback shift-register over a general finite field to be nonsingular is established. The general condition is contrasted to the well-known necessary and sufficient condition for nonsingularity of a binary feedback shift-register.     

Shift-register synthesis and BCH decoding

It is shown in this paper that the iterative algorithm introduced by Berlekamp for decoding BCH codes actually provides a general solution to the problem of synthesizing the shortest linear feedback shift register capable of generating a prescribed finite sequence of digits. The shift-register approach leads to a simple proof of the validity of the algorithm as well as providing additional insight into its properties. The equivalence of the decoding problem for BCH codes to a shift-register synthesis problem is demonstrated, and other applications for the algorithm are suggested.     

Non-real-time realization of any finite-state sequential machine using a single shift-register

A model for simulating any finite-state sequential machine is presented as an alternative to the single shift-register model in [1]. The proposed model not only uses a single shift-register but also has the advantage of allowing a machine to be synthesized whose speed is improved by a factor of 2 and whose cost is reduced by nearly a factor of 2 over machines produced by the synthesis procedure associated with the former model.     

A new teletext character set with enhanced legibility

Teletext is difficult to read, partly because of the letter fonts employed. Present fonts are contained in a matrix of 6 (horizontal) × 10 (vertical) elements. Research on matrix characters of optimum legibility started in 1969 at the Institute for Perception Research. Criteria resulting from this research have now been used to design alphanumeric characters in a matrix of 12 × 10 elements for use in Teletext. Several versions of each character were designed and their legibility tested in recognition experiments. The legibility of the best new version for each letter was compared with and shown generally to be greater than that of the presently used version.     

Permutation polynomials and nonsingular feedback shift registersover finite fields

A necessary and sufficient condition is established for nonsingularity of a feedback shift-register of degree at most two over a finite field. Several relations between permutation polynomials and nonsingular feedback shift-registers over finite fields are also studied. Four theorems are given and discussed     

Modified Berlekamp-Massey algorithm for two-sided shift-registersynthesis

A modification of the Berlekamp-Massey algorithm (BMA) for linear feedback shift-register (LFSR) synthesis is presented. The algorithm realises a two-sided strategy for processing the digits of a given sequence, starting with an arbitrary index. Finally, some applications are indicated     

The bipolar transistor bucket-brigade shift register

An analysis of the bipolar transistor bucket-brigade shift-register operation is presented for comparison to other charge-transfer shift-register schemes. It is shown that incomplete charge transfer, the most important performance limiting effect for the charge-coupled device and the IGFET bucket brigade, is very small under most practical operating conditions for the bipolar transistor bucket brigade. In addition to charge loss due to finite transistor current gain h/SUB fe/ the next most important performance limitation comes from collector-emitter capacitance. It is shown that this collector-emitter capacitance leads to reduced analog time delay on transfer through the register and to signal attenuation effects similar to those resulting from incomplete charge transfer. Using the results of the analysis, experimental data reported by Sangster are discussed and a comparison of the advantages and disadvantages of the bipolar bucket-brigade register with the MOS charge-transfer registers is made.     

Matrix method to determine shift-register connections for delayed pseudorandom binary sequences

A practical method is described to determine the modulo-2 feedback shift-register connections for producing advanced (or delayed) versions of a pseudorandom binary sequence.     

A New ICI Matrices Estimation Scheme Using Hadamard Sequence for OFDM Systems

The intercarrier interference (ICI) matrix for the orthogonal frequency division multiplexing (OFDM) systems usually has a fairly large dimension. The traditional least-square solution based on the pseudo-inverse operation, therefore, has its limitation. In addition, the provision of a sufficiently long training sequence to estimate the complete ICI matrix is not feasible, since it will result in severe throughput reduction. In this paper, we derive a lower bound for the mean-square estimation error among the least-square ICI matrix estimators using different training sequences and prove that the minimum mean-square error (MMSE) optimality is attained when the training sequences in different OFDM blocks are orthogonal to each other, regardless of the sequence length. We also prove that the asymptotical mean-square estimation error using the maximal-length shift-register sequences ($m$-sequences) as in the existing communication standards is 3 dB larger than that using the perfectly orthogonal sequences for ICI matrix estimation. Thus, we propose to employ the training sequences based on the Hadamard matrix to achieve a highly efficient and optimal ICI matrix estimator with minimum mean-square estimation error among all least-square ICI matrix estimators. Meanwhile, our new scheme involves only square computational complexity, while other existing least-square methods require the complexity proportional to the cube of the ICI matrix size. Analytical and experimental comparisons between our new scheme using Hadamard sequences and the existing method using$m$-sequences (pseudo-random sequences) show the significant advantages of our new ICI matrix estimator. The proposed method is most suitable for OFDM systems with large amount of subcarriers, using high order of subcarrier modulation, and designed for high-end of RF frequency band, where accurate ICI estimation is crucial.     

时钟畸变对多级移位寄存器的影响及其消除技术

本文分析了时钟畸变对移位寄存器的影响 ,提出了几种消除技术 ,并分析了它们的适用场合。     

Determining the burst-correcting limit of cyclic codes

Two new computationally efficient algorithms are developed for finding the exact burst-correcting limit of a cyclic code. The first algorithm is based on testing the colmn rank of certain submatrices of the parity-check matrix of the code. An auxiliary result is a proof that every cyclic(n,k)codes with a minimum distance of at least three, corrects at least all bursts of lengthlfloor (n - 2k + 1)/2 rflooror less. The second algorithm, which requires somewhat less computation, is based on finding the length of the shortest linear feedback shift-register that generates the subsequences of lengthn - kof the sequence formed by the coefficients of the parity-check polynomialh(x), augmented withlfloor (n-k)/2 rfloor -1leading zeros and trailing zeros. Tables of the burst-correcting limit for a large number of binary cyclic codes are included.     

Comments on "On minimal realization of transfer function matrices using Markov parameters and time moments"

It is pointed out that the algorithm proposed in the above letter was published by the authors in 1976. Some important features of this algorithm, which have been missed in the above letter, are also described. In the above paper Shrikhande et al. have presented a method of minimal normalization based on a modified Hankel matrix containing time moments as well as Markov parameters Several comments are in order.     

Rational approximants to the matrix exponential

The letter develops a method for obtaining a square matrix eNAt such that every element of eNAt is a proper rational function of t and is an efficient approximant to the corresponding element of the matrix exponential exp (At). Some useful general properties of eNAt are deduced and various procedures for computing eNAt are discussed.     

Implementation of Turing machines as finite automata

Logical systems are often represented using the Turing-machine concept. A design method is described whereby the normal transition tables for a Turing machine may be translated into a state table defining the control unit as a finite-state machine, and a special shift-register configuration in place of the computing tape. Design equations and circuits are given for a 4-state Turing machine embodying a 2-symbol alphabet.     

Ternary pseudonoise sequences

A simple criterion is derived to determine when the auto-correlation function of a ternary-feedback shift-register sequence is zero. This permits the isolation of several types of pseudonoise sequences, including the well known maximal-length sequences as well as many other varieties. Some of these sequences are seen to approximate to white noise even more closely than the familiar maximal-length type.     

Calculating poles and zeros of matrix transfer functions

The letter is concerned with a computational procedure for determining the poles and zeros of a matrix whose elements are in the field of rational functions.