共查询到20条相似文献,搜索用时 31 毫秒
1.
Park W.J. Jr. Komo J.J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(1):183-186
It is shown that m -sequences over GF(q m ) of length q nm-1 corresponding to primitive polynomials in GF[q m,x ] of degree n can be generated from known m -sequences over GF(q ) of length q nm-1 obtained from primitive polynomials in GF[q ,x ] of degree mn . A procedure for generating the m -sequences over GF(q 2) from m -sequences over GF(q ) was given which enables the generation of m -sequences over GF( p 2n). In addition it was shown that all of the primitive polynomials in GF[q ,m,x ] can be obtained from a complete set of the primitive polynomials in GF[q ,x ] 相似文献
2.
Retter C.T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(4):983-994
The author provides a simple method for determining the orthogonality of binary codes derived from Reed-Solomon codes and other cyclic codes of length 2m-1 over GF(2m) for m bits. Depending on the spectra of the codes, it is sufficient to test a small number of single-frequency pairs for orthogonality, and a pair of bases may be tested in each case simply by summing the appropriate powers of elements of the dual bases. This simple test can be used to find self-orthogonal codes. For even values of m , the author presents a technique that can be used to choose a basis that produces a self-orthogonal, doubly-even code in certain cases, particularly when m is highly composite. If m is a power of 2, this technique can be used to find self-dual bases for GF(2 m). Although the primary emphasis is on testing for self orthogonality, the fundamental theorems presented apply also to the orthogonality of two different codes 相似文献
3.
Fast decoding of codes from algebraic plane curves 总被引:2,自引:0,他引:2
Justesen J. Larsen K.J. Jensen H.E. Hoholdt T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(1):111-119
Improvement to an earlier decoding algorithm for codes from algebraic geometry is presented. For codes from an arbitrary regular plane curve the authors correct up to d */2-m 2 /8+m /4-9/8 errors, where d * is the designed distance of the code and m is the degree of the curve. The complexity of finding the error locator is O (n 7/3 ), where n is the length of the code. For codes from Hermitian curves the complexity of finding the error values, given the error locator, is O (n 2), and the same complexity can be obtained in the general case if only d */2-m 2/2 errors are corrected 相似文献
4.
A dispersion formula ϵ*eff(f )=ϵ* -{ϵ*-ϵ*eff(0)}/{1+( f /f 50)m}, for the effective relative permittivity ϵ*eff(f ) of an open microstrip line is derived for computer-aided design (CAD) use. The 50% dispersion point (the frequency f 50 at which ϵ*eff(f 50)={ϵ *+ϵ*eff(0)}/2}) is used a normalizing frequency in the proposed formula, and an expression for f 50 is derived. To obtain the best fit of ϵ *eff(f ) to the theoretical numerical model, the power m of the normalized frequency in the proposed formula is expressed as a function of width-to-height ratio w / h for w /h ⩾0.7 and as a function of w /h , f 50, and f for w /h ⩽0.7. The present formula has a high degree of accuracy, better than 0.6% in the range 0.1<w /h ⩽10, 1<ϵ*⩽128, and any height-to-wavelength ratio h /λ0 相似文献
5.
Van Oorschot P.C. Vanstone S.A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(2):444-453
The problem of finding roots in F of polynomials in F [x ] for F =GF(q m), where q is a prime or prime power and m is a positive integer greater than 1 is considered. The problem is analyzed by making use of the finite affine geometry AG(m ,q ). A new method is proposed for finding roots of polynomials over finite extension fields. It is more efficient than previous algorithms when the degree of the polynomial whose roots are to be found is less than dimension m of the extension field. Implementation of the algorithm can be enhanced in cases in which optimal normal bases for the coefficient field are available 相似文献
6.
A mathematical model is developed for the reliability of a system made up of m unreliable nodes arranged in a ring. The model can be used to calculate the reliability of single-ring networks in which the network recovery mechanism depends on bypassing failed stations, but link signal power margins are inadequate to overcome losses due to more than n bypass switches in series. Computational complexity is 0(n 2m +nm 2/2) in time, and 0(m 2/2) in memory requirements 相似文献
7.
Peransin J.-M. Vignaud P. Rigaud D. Vandamme L.K.J. 《Electron Devices, IEEE Transactions on》1990,37(10):2250-2253
The 1/f noise in normally-on MODFETs biased at low drain voltages is investigated. The experimentally observed relative noise in the drain current S I/I 2 versus the effective gate voltage V G=V GS-V off shows three regions which are explained. The observed dependencies are S I/I 2∝V G m with the exponents m =-1, -3, 0 with increasing values of V G. The model explains m =-1 as the region where the resistance and the 1/f noise stem from the 2-D electron gas under the gate electrode; the region with m =0 at large V G or V GS≅0 is due to the dominant contribution of the series resistance. In the region at intermediate V G , m =-3, the 1/f noise stems from the channel under the gate electrode, and the drain-source resistance is already dominated by the series resistance 相似文献
8.
A linear (m , n )-lattice system consists of m ·n elements arranged like the elements of a (m ,n )-matrix, i.e. each of the m rows includes m elements, and each of the n columns includes m elements. A circular (m ,n )-lattice system consists of m circles (centered at the same point) and n rays. The intersections of the circle and the rays represent the elements, i.e. each of the circles includes n elements and each of the rays has m elements. A (linear or circular) (m , n )-lattice system is a (linear or circular) connected-X -out-of-(m ,n ):F lattice system if it fails whenever at least one subset of connected failed components occurs which includes failed components connected in the meaning of connected-X. The paper presents some practical examples and the reliability formulas of simple systems using results of consecutive-k -out-of-n :F systems 相似文献
9.
Some fundamental contributions to the theory and applicability of optimal bounding ellipsoid (OBE) algorithms for signal processing are described. All reported OBE algorithms are placed in a general framework that demonstrates the relationship between the set-membership principles and least square error identification. Within this framework, flexible measures for adding explicit adaptation capability are formulated and demonstrated through simulation. Computational complexity analysis of OBE algorithms reveals that they are of O (m 2) complexity per data sample with m the number of parameters identified. Two very different approaches are described for rendering a specific OBE algorithm, the set-membership weighted recursive least squares algorithm, of O (m ) complexity. The first approach involves an algorithmic solution in which a suboptimal test for innovation is employed. The performance is demonstrated through simulation. The second method is an architectural approach in which complexity is reduced through parallel competition 相似文献
10.
Hou X.-D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(2):366-378
Let R (r ,m ) be the r th-order Reed-Muller code of length 2m and let ρ(r ,m ) be its covering radius. R (2,7), R (2,8), R (3,7), and R (4,8) are among those smallest Reed-Muller codes whose covering radii are not known. New bounds for the covering radii of these four codes are obtained. The results are ρ(2,7)⩾40, ρ(2,8)⩾84, 20⩽ρ(3,7)⩽23, and ρ(4,8)⩾22. Noncomputer proofs for the known results that ρ(2,6)=18 and that R (1,5) is normal are given 相似文献
11.
Many systems can be regarded as flow networks whose arcs have discrete and multi-valued random capacities. The probability of the maximum flow at each various level and the reliability of such a flow network can be calculated in terms of K-lattices which are generated from each subset of the family of all MCs (minimal cutsets). However the size of such a family 2m-1 (m =number of MCs) grows exponentially with m . Such a flow network can be considered as a multistate system with multistate components so that its reliability can be evaluated in terms of upper boundary points of each level d (named d -MCs here). This work presents an algorithm to generate all d -MCs from each MC for each system capacity level d . The new algorithm is analyzed and compared with the algorithm given by J. Xue (1985). Examples show how all d -MCs are generated; the reliability of one example is computed 相似文献
12.
Isaksson M. Zetterberg L.H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1993,39(2):337-346
Channel codes where the redundancy is obtained not from parity symbols, but from expanding the channel signal-set, are addressed. They were initially proposed by G. Ungerboeck (1982) using a convolutional code. Here, a block coding approach is given. Rate m /(m +1) coded 2m+1-ary phase-shift keying (PSK) is considered. The expanded signal-set is given the structure of a finite field. The code is defined by a square nonsingular circulant generator matrix over the field. Binary data are mapped on a dataword, of the same length as the codewords, over an additive subgroup of the field. The codes using trellises are described, and then the Viterbi algorithm for decoding is applied. The asymptotic coding gain ranges from 1.8 to 6.0 dB for QPSK going from blocklength 3 to 12. For 8-PSK, the gain is from 0.7 to 3.0 dB with blocklength 4 to 8. With only four states in the trellis, codes of any length for QPSK and 8-PSK are constructed, each having an asymptotic coding gain of 3.0 dB. Simulation results are presented. It is found that the bit-error rate performance at moderate signal-to-noise ratios is sensitive to the number of nearest and next-nearest neighbors 相似文献
13.
The authors present an efficient algorithm for the computation of the 4×4 discrete cosine transform (DCT). The algorithm is based on the decomposition of the 4×4 DCT into four 4-point 1-D DCTs. Thus, only 1-D transformations and some additions are required. It is shown that the proposed algorithm requires only 16 multiplications, which is half the number needed for the conventional row-column method. Since the 2m×2m DCT can be computed using the 4×4 DCT recursively for any m , the proposed algorithm leads to a fast algorithm for the computation of the 2-D DCT 相似文献
14.
The asymptotic (M →∞) probability of symbol error P e,m for M -ary orthogonal modulation in a Nakagami-m fading channel is given by the incomplete gamma function P (m , mx ) where x =In 2/(E b/N 0) and E b is the average energy per bit. For large signal-to-noise ratio this leads to a channel where the probability of symbol error varies as the inverse m th power of E b/N 0. These channels exist for all m ⩾1/2. The special case of m =1 corresponds to Rayleigh fading, an inverse linear channel 相似文献
15.
Kumar P.V. Wei V.K. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(5):1474-1482
Two results are presented concerning the partial periods (p-p's) of an m -sequence of period 2n-1. The first proves the existence of an m -sequence whose p-p's of length approximately (n +d log2 n ) have minimum distance between d and 2d for small d . The second result is of an asymptotic nature and proves that the normalized minimum distance of p-p's whose length is any fraction of the period of the m -sequence, approaches 1/2 as the period of m -sequence tends to infinity 相似文献
16.
Hurkx G.A.M. Klaassen D.B.M. Knuvers M.P.G. 《Electron Devices, IEEE Transactions on》1992,39(2):331-338
A recombination model for device simulation that includes both trap-assisted tunneling (under forward and reverse bias) and band-to-band tunneling (Zener tunneling) is presented. The model is formulated in terms of analytical functions of local variables, which makes it easy to implement in a numerical device simulator. The trap-assisted tunneling effect is described by an expression that for weak electric fields reduces to the conventional Shockley-Read-Hall (SRH) expression for recombination via traps. Compared to the conventional SRH expression, the model has one extra physical parameter, the effective mass m *. For m *=0.25 m 0 the model correctly describes the experimental observations associated with tunneling. The band-to-band tunneling contribution is found to be important at room temperature for electric fields larger than 7×105 V/cm. For dopant concentrations above 5×1017 cm-3 or, equivalently, for breakdown voltages below approximately 5 V, the reverse characteristics are dominated by band-to-band tunneling 相似文献
17.
Optimality property of the Gaussian window spectrogram 总被引:1,自引:0,他引:1
It is shown that for any signal x (t ) the minimum of ∫-∞∞∫-∞ ∞ [(t -t x)2+(f -f x)2] S x(w)(t , f ) dt df over all normalized time-windows w (t ) is achieved by the Gaussian window w (t )=21/4 exp (-πt 2). Here (t x, f x) is the center of gravity of the signal x (t ), S x(w) (t , f ) is the spectrogram of x (t ) due to the window w ( t ), and the double integral is a measure of the spread of S x(w) (t , f ) around (t x, f X) in the time-frequency plane 相似文献
18.
Jen-Shyan Wu Rong-Jaye Chen 《Reliability, IEEE Transactions on》1993,42(1):163-164
The time complexities of previously published algorithms for circular consecutive-k -out-of-n :F systems are O (nk 2) and O (nk ). The authors propose a method to improve the original O (nk 2 ) algorithm, and hence derive an O (nk ) algorithm 相似文献
19.
The electrical transport properties of β-SiC/Si heterojunctions were investigated using current-voltage (I -V ) and capacitance-voltage (C -V ) characteristics. The heterojunctions were fabricated by growing n-type crystalline β-SiC films on p-type Si substrates by chemical vapor deposition (CVD). The I -V data measured at various temperatures indicate that at relatively high current, the heterojunction forward current is dominated by thermionic emission of carriers and can be expressed as exp(-qV bi/kT ) exp(V /ηkT ), where V bi is the built-in voltage of the heterojunction and η(=1.3) is a constant independent of voltage and temperature. At lower current, defect-assisted multitunneling current dominates. The effective density of states and the density-of-states effective mass of electrons in the conduction band of SiC are estimated to be 1.7×1021 cm -3 and 0.78m 0, respectively. This study indicates that the β-SiC/Si heterojunction is a promising system for heterojunction (HJ) devices such as SiC-emitter heterojunction bipolar transistors (HBTs) 相似文献
20.
The observed 1/f noise in the light-output power S p of four different types of heterostructure lasers is explained in terms of spatially uncorrelated gain fluctuations and spontaneous emission fluctuations. Two possible noise sources are suggested: fluctuations in the absorption coefficient and fluctuations in the number of free carriers. Both models are in agreement with the experimental results obtained from index-guided and gain-guided diodes at wavelengths of 1.3 and 0.8 μm. The dependence S p ∝P m has been observed with P the average light-output power and m =3/2 under spontaneous emission, a small transition region with m =5/2, m =4 in the superradiation region, and 0⩽m ⩽1 in the laser region 相似文献