共查询到20条相似文献,搜索用时 672 毫秒
1.
Chao-Ping X. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(3):1140-1142
Sufficient and necessary conditions are obtained for which the geometric Goppa codes C (D ,G ) and C ( D ,H ) are equal for two divisors G and H . In particular, it is proven that if G and H are two effective divisors of the same degree smaller than n -1, then C (D ,G ) and C (D ,H ) are equal, if and only if G =H 相似文献
2.
van Wee G.J.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1988,34(2):237-245
The sphere bound is a trivial lower bound on K (n ,R ), the minimal cardinality of any binary code of length n and with covering radius R . By simple arguments it is considerably improved, to K (n ,1)⩾2 n/n for n even. A table of lower and upper bounds on K (n ,R ) for n ⩽33, R ⩽10 is included 相似文献
3.
Hou X.-D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1990,36(3):683-685
Two upper bounds for the norm N (C ) of a binary linear code C with minimal weight d and covering radius R are given. The second of these bounds implies that C is normal if R =3 相似文献
4.
Connectivity properties of a packet radio network model 总被引:16,自引:0,他引:16
Philips T.K. Panwar S.S. Tantawi A.N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(5):1044-1047
A model of a packet radio network in which transmitters with range R are distributed according to a two-dimensional Poisson point process with density D is examined. To ensure network connectivity, it is shown that πR 2D , the expected number of nearest neighbors of a transmitter, must grow logarithmically with the area of the network. For an infinite area there exists an infinite connected component with nonzero probability if π R 2D >N 0, for some critical value N 0. It is shown that 2.195<N 0<10.526 相似文献
5.
Gaussian feedback capacity 总被引:2,自引:0,他引:2
Cover T.M. Pombra S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(1):37-43
The capacity of time-varying additive Gaussian noise channels with feedback is characterized. Toward this end, an asymptotic equipartition theorem for nonstationary Gaussian processes is proved. Then, with the aid of certain matrix inequalities, it is proved that the feedback capacity C FB in bits per transmission and the nonfeedback capacity C satisfy C ⩽C FB ⩽2C and C ⩽C FB⩽ C +1/2 相似文献
6.
Patapoutian A. Kumar P.V. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(4):1375-1382
A simple technique employing linear block codes to construct (d ,k ) error-correcting block codes is considered. This scheme allows asymptotically reliable transmission at rate R over a BSC channel with capacity C BSC provided R ⩽C d,k-(1+C BSC), where C d,k is the maximum entropy of a (d ,k ) source. For the same error-correcting capability, the loss in code rate incurred by a multiple-error correcting (d ,k ) code resulting from this scheme is no greater than that incurred by the parent linear block code. The single-error correcting code is asymptotically optimal. A modification allows the correction of single bit-shaft errors as well. Decoding can be accomplished using off-the-shelf decoders. A systematic (but suboptimal) encoding scheme and detailed case studies are provided 相似文献
7.
The problem of counting the number of cuts with the minimum cardinality in an undirected multigraph arises in various applications, such as testing the super-λ-ness of a graph, as described by F.T. Boesch (1986), and calculating upper and lower bounds on the probabilistic connectedness of a stochastic graph G in which edges are subject to failure. It is shown that the number |C ( G )| of cuts with the minimum cardinality λ(G ) in a multiple graph G =(V ,E ) can be computed in O (|E |+λ(G )|V |2 +λ(G )|C (G )||V |) time 相似文献
8.
Honkala H.S. Hamalainen H.O. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(2):372-375
The normality of binary codes is studied. The minimum cardinality of a binary code of length n with covering radius R is denoted by K (n ,R ). It is assumed that C is an (n ,M )R code, that is, a binary code of length n with M codewords and covering radius R . It is shown that if C is an (n ,M )1 code, then it is easy to find a normal (n ,M )1 code by changing C in a suitable way, and that all the optimal (n ,M )1 codes (i.e. those for which M =K (n ,1)) are normal and their every coordinate is acceptable. It is shown that if C is an abnormal (n ,M ) code, then n ⩾9, and an abnormal (9118)1 code which is the smallest abnormal code known at present, is constructed. Lower bounds on the minimum cardinality of a binary abnormal code of length n with covering radius 1 are derived, and it is shown that if an (n ,M )1 code is abnormal, then M ⩾96 相似文献
9.
The authors consider linear lightwave networks with a single waveband that have N inputs, each with a transmitter, and N outputs, each with a receiver, interconnected by optical links, broadcast stars, and wavelength-independent 2×2 switches. The transmitters and receivers can tune to C different wavelengths. The authors describe a rearrangeably nonblocking network that is a modification of the Benes network and uses transmitters that are fixed tuned and switches with two states. The network uses [1+o (1)] N /log2(N /C ) switches, which is shown to be nearly the minimum number. It is also shown that, if C =o (log N ), then a rearrangeably nonblocking network requires [1+o (1)]N log2N switches even if the switches have more than two states 相似文献
10.
Brualdi R.A. Pless V.S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1990,36(2):399-401
If C is a code, an orphan is a coset that is not a descendant. Orphans arise naturally in the investigation of the covering radius. Case C has only even-weight vectors and minimum distance of at least four. Cosets that are orphans are characterized, and then the existence is proved of a family of orphans of first-order Reed-Muller codes R (1, m ). For m ⩽5 all orphans of R (1, m ) are identified 相似文献
11.
Ytrehus O. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(2):349-351
A binary, linear block code C with block length n and dimension n is commonly denoted by [n , k ] or, if its minimum distance is d , by [n , k ,d ]. The code's covering radius r (C ) can be defined as the smallest number r such that any binary column vector of length (n -k ) can be written as a sum of r or fewer columns of a parity-check matrix of C . An [n ,k ] code with covering radius r is denoted by [n ,k ]r . R.A. Brualdi et al., (1989) showed that l (m ,r ) is defined to be the smallest n such that an [n ,n -m ]r code exists. l (m ,2) is known for m ⩽6, while it is shown by Brualdi et al. that 17⩽l (7,2)⩽19. This lower bound is improved by A.R. Calderbank et al. (1988), where it is shown that [17,10]2 codes do not exist. The nonexistence of [18,11]2 codes is proved, so that l (7,2)=19. l [7.2)=19 is established by showing that [18,11]2 codes do not exist. It is also shown that [64,53]2 codes do not exist, implying that l (11,2)⩾65 相似文献
12.
Short codes with a given covering radius 总被引:1,自引:0,他引:1
Brualdi R.A. Pless V.S. Wilson R.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(1):99-109
The covering radius r of a code is the maximum distance from any vector in the space containing the code to the nearest codeword. The authors introduce a new function l (m ,r ), called the length function, which equals the smallest length of a binary code of codimension m and covering radius r . They investigate basic properties of the length function. Projective geometries over larger fields are used to construct families of codes which improve significantly the upper bound for l (m ,2) obtained by amalgamation of Hamming codes. General methods are developed for ruling out the existence of codes of covering radius 2 with a given codimension and length resulting in lower bounds for l (m ,2). A table is presented which gives the best results now known for l (m ,r ) with m ⩽12 and r ⩽12 相似文献
13.
A coding technique for improving the reliability of digital transmission over noisy partial-response channels with characteristics (±D m), m =1, 2, where the channel input symbols are constrained to be ±1, is presented. In particular, the application of a traditional modulation code as an inner code of a concentrated coding scheme in which the outer code is designed for maximum (free) Hamming distance is considered. A performance comparison is made between the concentrated scheme and a coding technique presented by Wolf and G. Ungerboeck (see ibid., vol. COM-34, p.765-773, Aug. 1986) for the dicode channel with transfer function (1- D ) 相似文献
14.
Feng G.-L. Rao T.R.N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(1):37-45
A simple decoding procedure for algebraic-geometric codes C Ω(D ,G ) is presented. This decoding procedure is a generalization of Peterson's decoding procedure for the BCH codes. It can be used to correct any [(d*-1)/2] or fewer errors with complexity O (n 3), where d * is the designed minimum distance of the algebraic-geometric code and n is the codelength 相似文献
15.
Generalized Hamming weights of linear codes 总被引:4,自引:0,他引:4
Helleseth T. Klove T. Ytrehus O. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(3):1133-1140
The generalized Hamming weight, d r(C ), of a binary linear code C is the size of the smallest support of any r -dimensional subcode of C . The parameter d r(C ) determines the code's performance on the wire-tap channel of Type II. Bounds on d r(C ), and in some cases exact expressions, are derived. In particular, a generalized Griesmer bound for d r(C ) is presented and examples are given of codes meeting this bound with equality 相似文献
16.
The performance of nonblocking packet switches such as the knockout switch and Batcher banyan switch for high-speed communication networks can be improved as the switching capacity L per output increases; the switching capacity per output refers to the maximum number of packets transferred to an output during a slot. The N ×N switch with L =N was shown to attain the best possible performance by M.J. Karol et al. (1987). Here a N ×N nonblocking packet switch with input and output buffers is analyzed for an arbitrary number of L such that 1⩽L ⩽N . The maximum throughput and packet loss probability at input are obtained when N =∞ 相似文献
17.
Decoding performance of Reed-Solomon (RS) coded M -ary FSK with noncoherent detection in a frequency-hopping spread spectrum mobile radio channel is theoretically analyzed. Exact formulas and an approximate one for evaluating word error rates (WERs) of error correction and error-and-erasure correction schemes on decoding the RS codes are derived. It is shown that with K symbol erasure and C symbol error detection, RS coded M -ary FSK achieves the equivalent diversity order of (K +1)(C +1) 相似文献
18.
A simple relationship between the inductance matrix and the auxiliary capacitance matrix is given. For a multiconductor transmission line consisting of N c conducting cylinders in inhomogeneous media consisting of N d homogeneous regions with permeabilities μi and permittivities ϵ i, the inductance matrix [L ] for the line is obtained by solving the magnetostatic problem of N c conductors in N d regions with permeabilities μ i. The capacitance matrix [C ] for the line is obtained by solving the electrostatic problem of N c conductors in N d regions with permittivities ϵ i. It is shown that [L ]=μ0ϵ0[C '] -1, where [C '] is the capacitance matrix of an auxiliary electrostatic problem of N c conductors in N d regions with relative permittivities set equal to the reciprocals of the relative permeabilities of the magnetostatic problem, i.e. ϵ' i/ϵ0=μ0/μi 相似文献
19.
Honig M.L. Steiglitz K. Norman S.A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(5):1327-1341
Given a linear, time-invariant, discrete-time channel, the problem of constructing N input signals of finite length K that maximize minimum l2 distance between pairs of outputs is considered. Two constraints on the input signals are considered: a power constraint on each of the N inputs (hard constraint) and an average power constraint over the entire set of inputs (soft constraint). The hard constraint, problem is equivalent to packing N points in an ellipsoid in min(K ,N -1) dimensions to maximize the minimum Euclidean distance between pairs of points. Gradient-based numerical algorithms and a constructive technique based on dense lattices are used to find locally optimal solutions to the preceding signal design problems. Two numerical examples are shown for which the average spectrum of an optimized signal set resembles the water pouring spectrum that achieves Shannon capacity, assuming additive white Gaussian noise 相似文献
20.
Gutman M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(2):401-408
The decision problem of testing M hypotheses when the source is K th-order Markov and there are M (or fewer) training sequences of length N and a single test sequence of length n is considered. K , M , n , N are all given. It is shown what the requirements are on M , n , N to achieve vanishing (exponential) error probabilities and how to determine or bound the exponent. A likelihood ratio test that is allowed to produce a no-match decision is shown to provide asymptotically optimal error probabilities and minimum no-match decisions. As an important serial case, the binary hypotheses problem without rejection is discussed. It is shown that, for this configuration, only one training sequence is needed to achieve an asymptotically optimal test 相似文献