共查询到20条相似文献,搜索用时 15 毫秒
1.
Honkala I.S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(4):1203-1206
The concept of a (k , t )-subnormal covering code is defined. It is discussed how an amalgamated-direct-sumlike construction can be used to combine such codes. The existence of optimal (q , n , M ) 1 codes C is discussed such that by puncturing the first coordinate of C one obtains a code with (q , 1)-subnorm 2 相似文献
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The performance of a statistical multiplexer whose inputs consist of a superposition of voice packet streams is studied. The delay for such a system is analyzed by solving the ΣD i/ D /1 queue. The analytic method can be used to find the approximate mean delay for an arbitrarily large number of trunks and the approximate delay distribution when the number of trunks is less than 100. An efficient hybrid simulation of the packet voice multiplexer which can be used to find the delay distribution for a large number of trunks is presented. In addition, easily computable error bounds for the present approximation are provided, and the accuracy of the M / D /1 approximation is investigated 相似文献
4.
Kasami T. Takata T. Fujiwara T. Lin S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(1):164-167
Two important structural properties of block M (=2' )-ary PSK modulation codes, linear structure and phase symmetry, are investigated. An M -ary modulation code is first represented as a code with symbols from the integer group S M-PSK=(0,1,2,---,M -1) under modulo-M addition. Then the linear structure of block M -PSK modulation codes over S M-PSK with respect to modulo- M vector addition is defined, and conditions are derived under which a block M -PSK modulation code is linear. Once the linear structure is developed, the phase symmetry of block M -PSK modulation codes is studied. In particular, a necessary and sufficient condition for a block M -PSK modulation code that is linear as a binary code to be invariant under 2h/180°M phase rotation, for 1⩽h ⩽l is derived. Finally, a list of short 8-PSK and 16-PSK modulation codes is given, together with their linear structure and the smallest phase rotation for which a code is invariant 相似文献
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It is shown that for worst-case partial-band jamming, the error probability performance (for fixed E b/N I) becomes worse with increasing M for (M >16). The asymptotic probability-of-error is not zero for any E b/N I(>ln 2), but decreases inverse linearly with respect to it. In the fading case, the error-probability performance (for fixed E b/N 0) improves with M for noncoherent detection, but worsens with M for coherent detection. For large E b/N 0 the performance of the Rayleigh fading channel asymptotically approaches the same limit as the worst case partial-band jammed channel. However, for values of M at least up to 4096, the partial-band jammed channel does better. While it is unlikely that an M -ary orthogonal signal set with M >1024 will be used in a practical situation, these results suggest an important theoretical problem; namely, what signal set achieves reliable communication 相似文献
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The effect of nonnormality on E {X } and R charts is reported. The effect of departure from normality can be examined by comparing the probabilities that E {X } and R lie outside their three-standard-deviation and two-standard-deviation control limits. Tukey's λ-family of symmetric distributions is used because it contains a wide spectrum of distributions with a variety of tail areas. The constants required to construct E {X } and R charts for the λ-family are computed. Control charts based on the assumption of normality give inaccurate results when the tails of the underlying distribution are thin or thick. The validity of the normality assumption is examined by using a numerical example 相似文献
8.
Al-Hussaini E.K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1988,76(6):731-733
In previous studies by V.G. Hansen (1973) and by Hansen and J.H. Sawyers (1980), performance models were developed for the smaller of (SO) and greater of (GO) constant false alarm rate (CFAR) detectors processing a single sweep (or single pulse). Here, performances of the SO and GO detectors are derived when M pulses are incoherently integrated in a homogeneous environment. This situation is fitted to the case of a radar system processing M sweeps per range bin 相似文献
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Fadavi-Ardekani J. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1993,1(2):120-125
The architecture of a design method for an M -bit by N -bit Booth encoded parallel multiplier generator are discussed. An algorithm for reducing the delay inside the branches of the Wallace tree section is explained. The final step of adding two N ±M -1-bit numbers is done by an optimal carry select adder stage. The algorithm for optimal partitioning of the N ±M -1-bit adder is also presented 相似文献
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Using a multidimensional approach, the author discovers a large family of rotationally invariant trellis-coded M -PSK (M-ary shift keying) schemes, M ⩾8, with nominal coding gains ranging from 3 to 5 dB and with bandwidth requirements the same as, or even less than, those of uncoded M /2-PSK schemes at the same information bit rate. The rotationally invariant schemes have performance and complexities comparable to the best known nonrotationally-invariant trellis-coded two-dimensional M -PSK schemes. Computer simulation results for these schemes, assuming an additive white-Gaussian-noise (AWGN) channel, are reported 相似文献
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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
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Cheung K.-M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1990,36(5):1149-1153
An explicit formula is derived that enumerates the complete weight distribution of an (n , k , d ) linear code using a partially known weight distribution. An approximation formula for the weight distribution of q -ary linear (n , k , d ) codes is also derived. It is shown that, for a given q -ary linear (n , k , d ) code, the ratio of the number of codewords of weight u to the number of words of weight u approaches the constant Q =q -(n-k) as u becomes large. The error term is a decreasing function of the minimum weight of the dual. The results are also valid for nonlinear (n , M , d ) codes with the minimum weight of the dual replaced by the dual distance 相似文献
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A passive, single-hop, fiber-optic interconnection among N stations, each with two transmitters and one receiver, and a round-robin transmission schedule for it, which jointly permit log 2 N concurrent noninterfering transmissions on a single wavelength, has recently been described. This is a substantial improvement over the previously known limit of two concurrent transmissions, but the layout of this interconnection poses a challenge in terms of both wiring complexity and path loss. A power-efficient implementation of this interconnection using several stages of balanced fiber-optic star couplers is presented here. With lossless components, path loss is N , the same as that of a single-star interconnection that permits only a single transmission at a time. Consequently, the high degree of parallelism translates into higher capacity. The required number of (2×2) star couplers is also very similar to that required for implementing a single N ×X star 相似文献
14.
Yamaguchi S. Cheville A. Hofmann T. Sauerbrey R.A. Wilson W.L. Jr. Tittel F.K. 《Quantum Electronics, IEEE Journal of》1991,27(6):1288-1295
Optimum energy extraction from an electron-beam-pumped XeF(C →A ) laser is achieved with a five-component rare gas halide mixture. The characterization and modeling of laser action in such a gas mixture requires a knowledge of small-signal gain and absorption coefficients not only on the blue-green XeF(C → A ) transition, but also in the ultraviolet (UV) region for the competing XeF(B →X ) and KrF(B →X ) transitions. The authors report gain measurements on the XeF(C →A ) transition and small-signal gain and absorption coefficients at or near both the XeF(B →X ) (351 and 353 nm) and KrF(B →X ) (248 nm) transitions. A study of the gain for the UV and visible transitions as a function of Kr and Xe partial pressure is reported, and its impact on the XeF(C →A ) kinetics is discussed 相似文献
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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
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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
17.
Interpretation and control of C -V measurementsusing pattern recognition and expert system techniques
Walls J.A. Walton A.J. Robertson J.M. 《Semiconductor Manufacturing, IEEE Transactions on》1991,4(3):250-262
The authors demonstrate how a pattern-recognition system can be applied to the interpretation of capacitance-voltage (C -V ) curves on an MOS test structure. By intelligently sequencing additional measurements it is possible to accurately extract the maximum amount of information available from C -V and conductance-voltage (G -V ) measurements. The expert system described, (CV -EXPERT), is completely integrated with the measurement, instrumentation, and control software and is thus able to call up a sequence of individually tailored tests for the MOS test structure under investigation. The prototype system is able to correctly identify a number of process faults, including a leaky oxide, as shown. Improvements that could be gained from developing rules to coordinate G -V , capacitance-time, and doping profile measurements simply by recognizing the important factors in the initial C - V measurement are illustrated 相似文献
18.
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
19.
Wu J. Costello D.J. Jr. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(3):933-939
Set partitioning is applied to multidimensional signal spaces over GF(q ), i.e., GFn1(q ) (n 1⩽q ), and it is shown how to construct both multilevel block codes and multilevel trellis codes over GF(q ). Multilevel (n , k , d ) block codes over GF(q ) with block length n , number of information symbols k , and minimum distance d min⩾d are presented. These codes use Reed-Solomon codes as component codes. Longer multilevel block codes are also constructed using q -ary block codes with block length longer than q +1 as component codes. Some quaternary multilevel block codes are presented with the same length and number of information symbols as, but larger distance than, the best previously known quaternary one-level block codes. It is proved that if all the component block codes are linear. the multilevel block code is also linear. Low-rate q -ary convolutional codes, word-error-correcting convolutional codes, and binary-to-q -ary convolutional codes can also be used to construct multilevel trellis codes over GF(q ) or binary-to-q -ary trellis codes 相似文献
20.
The problem of achieving optimal system size (n ) for {k ,n -k +1}-out-of-n systems, assuming that failure may take either of two forms, is studied. It is assumed that components are independently identically distributed (i.i.d.) and that the two kinds of system failures can have different costs. The optimal k or n that maximizes mean system-profit is determined, and the effect of system parameters on the optimal k or n is studied. It is shown that there does not exist a pair (k ,n ) maximizing the mean system-profit 相似文献