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Träfflista för sökning "L773:0018 9448 OR L773:0018 9448 srt2:(1990-1994)"

Sökning: L773:0018 9448 OR L773:0018 9448 > (1990-1994)

  • Resultat 1-10 av 12
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1.
  • Chen, Eric Zhi, 1963- (författare)
  • Further results on difference triangle sets
  • 1994
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 40:4, s. 1268-1270
  • Tidskriftsartikel (refereegranskat)abstract
    • Further results on the upper bounds for difference tri8nglesets (DTS) are derived from disjoint difference sets and additive sequencesof permutations, whit3 greatly improve the known bounds.
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2.
  • Chen, Eric Zhi, 1963- (författare)
  • Six new binary quasi-cyclic codes
  • 1994
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 40:5, s. 1666-1667
  • Tidskriftsartikel (refereegranskat)abstract
    • Six new quasi-cyclic codes are presented, which improve thelower bounds on the minimum distance for a binary code. A localexhaustive search is used to find these codes and many other quasi-cycliccodes which attain the lower bounds.
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3.
  • Chepyshov, V.V, et al. (författare)
  • The free distance of fixed convolutional rate 2/4 codes meets the Costello bound
  • 1992
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 38:4, s. 1360-1366
  • Tidskriftsartikel (refereegranskat)abstract
    • The long standing question whether the free distance of fixed rate convolutional codes is as good as the Costello bound was almost solved by K.S. Zigangirov and J.L. Massey (1987). They proved that this is indeed the case for codes with long branch length and rates 2/c, c>or=5. It is shown that there exist fixed convolutional codes of rate 2/4 whose free distance d/sub free/ meets the Costello bound originally derived for time varying convolutional codes
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4.
  • Holst, Ulla, et al. (författare)
  • Recursive estimation in mixture models with Markov regime
  • 1991
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448. ; 37:6, s. 1683-1690
  • Tidskriftsartikel (refereegranskat)abstract
    • A recursive algorithm is proposed for estimation of parameters in mixture models, where the observations are governed by a hidden Markov chain. The performance of the algorithm is studied by simulations of a symmetric normal mixture. The algorithm seems to be stable and produce approximately normally distributed estimates, provided the adaptive matrix is kept well conditioned.
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5.
  • Johannesson, Rolf, et al. (författare)
  • A linear algebra approach to minimal convolutional encoders
  • 1993
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 39:4, s. 1219-1233
  • Tidskriftsartikel (refereegranskat)abstract
    • The authors review the work of G.D. Forney, Jr., on the algebraic structure of convolutional encoders upon which some new results regarding minimal convolutional encoders rest. An example is given of a basic convolutional encoding matrix whose number of abstract states is minimal over all equivalent encoding matrices. However, this encoding matrix can be realized with a minimal number of memory elements neither in controller canonical form nor in observer canonical form. Thus, this encoding matrix is not minimal according to Forney's definition of a minimal encoder. To resolve this difficulty, the following three minimality criteria are introduced: minimal-basic encoding matrix, minimal encoding matrix, and minimal encoder. It is shown that all minimal-basic encoding matrices are minimal and that there exist minimal encoding matrices that are not minimal-basic. Several equivalent conditions are given for an encoding matrix to be minimal. It is proven that the constraint lengths of two equivalent minimal-basic encoding matrices are equal one by one up to a rearrangement. All results are proven using only elementary linear algebra
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6.
  • Johannesson, Rolf, et al. (författare)
  • Strengthening Simmon's bound on impersonation
  • 1991
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 37:4, s. 1182-1185
  • Tidskriftsartikel (refereegranskat)abstract
    • Simmons' lower bound on impersonation P1⩾2 -I(M;E) where M and E denote the message and the encoding rule, respectively, is strengthened by maximizing over the source statistics and by allowing dependence between the message and the encoding rule. The authors show that a refinement of their argument, which removes the assumption of independence between E and the source state S, leads to an even stronger bound
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7.
  • Johansson, Thomas (författare)
  • Lower bounds on the probability of deception in authentication with arbitration
  • 1994
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448. ; 40:5, s. 1573-1585
  • Tidskriftsartikel (refereegranskat)abstract
    • The paper investigates a model for authentication in which not only an outsider, but also the transmitter or the receiver, may cheat. Lower bounds on the probability of success for different types of deception as well as on the parameters of secure authentication codes are derived. The latter bounds are shown to be tight by demonstrating codes in projective space that meet the bounds with equality.
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8.
  • Koski, Timo, et al. (författare)
  • On quantizer distortion and the upper bound for exponential entropy
  • 1991
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 37:4, s. 1168-1172
  • Tidskriftsartikel (refereegranskat)abstract
    • A sharp upper bound is derived for the exponential entropy in the class of absolutely continuous distributions with specific standard deviation and an exact description of the extremal distributions. This result is interpreted as determining the least favorable cases for certain methods of quantization of analog sources. It is known that for a large class of quantizers (both zero-memory and vector) the rth power distortion, as well as some other distortion criteria, are bounded below by a constant, depending on r, multiplied by a certain integral of the source's probability density. It is pointed out that this bound can be rewritten in terms of the exponential entropy. The exponential entropy measures the quantitative extent or range of the source distribution. This fact gives a physical interpretation of the indicated limits of quantizer performance, further elucidated by the main result
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9.
  • Koski, Timo, et al. (författare)
  • On the statistics of the error in predictive coding for stationary Ornstein-Uhlenbeck processes
  • 1992
  • Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 38:3, s. 1029-1040
  • Tidskriftsartikel (refereegranskat)abstract
    • Explicit expression are derived for the conditional expectation and variance of the encoder in a predictive DPCM coder with an N-level quantizer, when a stationary Ornstein-Uhlenbeck process is a source. A representation of the encoder in terms of a stochastic integral is presented. These expressions yield a nonlinear stochastic difference equation for the decoding error process and a stochastic differential equation (SDE) as a weak limit for the error process. The statistical properties of the error obtained as a solution of the limiting SDE are interpreted in terms of the slope overload error
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10.
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  • Resultat 1-10 av 12

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