RPR中一种高性能公平算法的研究

针对目前应用于弹性分组环（RPR）的公平算法存在的不足，文章提出了一种新的公平算法-HP—fa（High Performance—fairnessaigorithm），并对此算法进行了理论分析和仿真验证，结果表明该算法不仅带宽利用率高、收敛迅速，而且能够更好地实现环网的公平。     

Time-frequency localisation of Shannon wavelet packets

It is well known that the 2/spl pi/ minimally supported frequency scaling function /spl phi//sup /spl alpha//(x) satisfying /spl phi//spl circ//sup /spl alpha//(/spl omega/)=/spl chi//sub (-/spl alpha/,2/spl pi/-/spl alpha/)/(/spl omega/), 0相似文献   

The /spl alpha/-EM algorithm: surrogate likelihood maximization using /spl alpha/-logarithmic information measures

A new likelihood maximization algorithm called the /spl alpha/-EM algorithm (/spl alpha/-expectation-maximization algorithm) is presented. This algorithm outperforms the traditional or logarithmic EM algorithm in terms of convergence speed for an appropriate range of the design parameter /spl alpha/. The log-EM algorithm is a special case corresponding to /spl alpha/=-1. The main idea behind the /spl alpha/-EM algorithm is to search for an effective surrogate function or a minorizer for the maximization of the observed data's likelihood ratio. The surrogate function adopted in this paper is based upon the /spl alpha/-logarithm which is related to the convex divergence. The convergence speed of the /spl alpha/-EM algorithm is theoretically analyzed through /spl alpha/-dependent update matrices and illustrated by numerical simulations. Finally, general guidelines for using the /spl alpha/-logarithmic methods are given. The choice of alternative surrogate functions is also discussed.     

Convolutive blind source separation by minimizing mutual information between segments of signals

A method to perform convolutive blind source separation of super-Gaussian sources by minimizing the mutual information between segments of output signals is presented. The proposed approach is essentially an implementation of an idea previously proposed by Pham. The formulation of mutual information in the proposed criterion makes use of a nonparametric estimator of Renyi's /spl alpha/-entropy, which becomes Shannon's entropy in the limit as /spl alpha/ approaches 1. Since /spl alpha/ can be any number greater than 0, this produces a family of criteria having an infinite number of members. Interestingly, it appears that Shannon's entropy cannot be used for convolutive source separation with this type of estimator. In fact, only one value of /spl alpha/ appears to be appropriate, namely /spl alpha/=2, which corresponds to Renyi's quadratic entropy. Four experiments are included to show the efficacy of the proposed criterion.     

Optimal design and applications for quasi-phase-matching three-wave mixing

Solutions of quasi-phase-matching three-wave mixing (TWM) for a nonuniform grating structure with phase-shifted segments are derived by use of a matrix operator, for the first time to the authors' knowledge, under the small-signal approximation. Compared with iterative methods of coupled-mode equations, using these expressions can significantly shorten the calculation time, and they can be effectively applied to all-optical signal processing in TWM. The signal and pump bandwidths of wavelength conversion in difference-frequency mixing, as well as the all-optical gating bandwidth in sum-frequency mixing, are optimized with the matrix solutions. By comparison with loss-free waveguide, the propagation loss a of the waveguide decreases the conversion efficiency /spl eta/, but has little influence on the bandwidth. Numerical results show that /spl alpha/ can be ignored for nonlinear lengths L<20 mm, and the optimal bandwidth /spl Delta//spl lambda/ is sensitive to /spl eta/ and the variation in the grating period, but not to /spl alpha/.     

A cone-based distributed topology-control algorithm for wireless multi-hop networks

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology-control (CBTC) algorithm. This algorithm does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of the algorithm is that a node u transmits with the minimum power p/sub u,/spl alpha// required to ensure that in every cone of degree /spl alpha/ around u, there is some node that u can reach with power p/sub u,/spl alpha//. We show that taking /spl alpha/=5/spl pi//6 is a necessary and sufficient condition to guarantee that network connectivity is preserved. More precisely, if there is a path from s to t when every node communicates at maximum power then, if /spl alpha//spl les/5/spl pi//6, there is still a path in the smallest symmetric graph G/sub /spl alpha// containing all edges (u,v) such that u can communicate with v using power p/sub u,/spl alpha//. On the other hand, if /spl alpha/>5/spl pi//6, connectivity is not necessarily preserved. We also propose a set of optimizations that further reduce power consumption and prove that they retain network connectivity. Dynamic reconfiguration in the presence of failures and mobility is also discussed. Simulation results are presented to demonstrate the effectiveness of the algorithm and the optimizations.     

Temperature sensitivity of 1300-nm InGaAsN quantum-well lasers

The temperature sensitivity of metal-organic chemical vapor deposition (MOCVD)-grown highly strained (/spl Delta//spl alpha///spl alpha//spl sim/2.7%) In/sub 0.4/Ga/sub 0.6/Asand In/sub 0.4/Ga/sub 0.6/As/sub 0.995/N/sub 0.005/ quantum-well (QW) active lasers, with lasing wavelength of 1.185 and 1.295 /spl mu/m, respectively, is analyzed in terms of measured fundamental device parameters. From our analysis, the lower To values for the InGaAsN QW lasers can be explained in terms of the temperature dependence of the current injection efficiency, presumably due to increased carrier leakage in the InGaAsN QW lasers.     

Evaluation of high-temperature absorption coefficients of optical fibers

The large absorption coefficient /spl alpha/ of single-mode optical fiber at high temperatures is closely related to the generation of the fiber fuse phenomenon. We propose a high-temperature loss-increase mechanism, which includes three factors that bring about an increase in the /spl alpha/ values: 1) point-defect (Ge E' center) formation; 2) electronic conductivity due to the thermal ionization of a Ge-doped silica core; and 3) thermochemical SiO production in the silica glass. Ge E'-center formation and electronic conductivity in the Ge-doped silica core are dominant factors at temperatures near the critical temperature of 1323 K. However, these factors cannot explain the large /spl alpha/ values observed at high temperatures above 2273 K. By contrast, SiO gas and/or solid, which are thermochemically produced in the silica glass, exhibit large /spl alpha/ values of the order of 10/sup 4/ m/sup -1/ at 2293 K. The /spl alpha/ value estimated at 0.5 /spl mu/m is close to the experimental value reported in the fiber fuse experiments.     

Order statistics from a logistic distribution and applications to survival and reliability analysis

Joint moments involving arbitrary powers of order statistics are the main concern. Consider order statistics u/sub 1/ /spl les/ u/sub 2/ /spl les/ /spl middot//spl middot//spl middot/ /spl les/ u/sub k/ coming from a simple random sample of size n from a real continuous population where u/sub 1/ = x/sub r(1):n/ is order-statistic #r/sub 1/, u/sub 2/ = x/sub r(1)+r(2):n/ is order statistic #(r/sub 1/ + r/sub 2/), et al., and u/sub k/ = x/sub r(1)+/spl middot//spl middot//spl middot/+r(k):n/ is order statistic #(r/sub 1/ +/spl middot//spl middot//spl middot/+ r/sub k/). Product moments are examined of the type E[u/sub 1//sup /spl alpha/(1)/ /spl middot/ u/sub 2//sup /spl alpha/(2)//sub /spl middot/ /spl middot//spl middot//spl middot//spl middot//u/sub k//sup /spl alpha/(k)/] where /spl alpha//sub 1/, ..., /spl alpha//sub k/ are arbitrary quantities that might be complex numbers, and E[/spl middot/] denotes the s-expected value. Some explicit evaluations are considered for a logistic population. Detailed evaluations of all integer moments of u/sub 1/ and recurrence relations, recurring only on the order of the moments, are given. Connections to survival functions in survival analysis, hazard functions in reliability situations, real type-1, type-2 /spl beta/ and Dirichlet distributions are also examined. Arbitrary product moments for the survival functions are evaluated. Very general results are obtained which can be used in many problems in various areas.     

Cyclic codes over GR(4/sup m/) which are also cyclic over /spl Zopf//sub 4/

Let GR(4/sup m/) be the Galois ring of characteristic 4 and cardinality 4/sup m/, and /spl alpha/_={/spl alpha//sub 0/,/spl alpha//sub 1/,...,/spl alpha//sub m-1/} be a basis of GR(4/sup m/) over /spl Zopf//sub 4/ when we regard GR(4/sup m/) as a free /spl Zopf//sub 4/-module of rank m. Define the map d/sub /spl alpha/_/ from GR(4/sup m/)[z]/(z/sup n/-1) into /spl Zopf//sub 4/[z]/(z/sup mn/-1) by d/spl alpha/_(a(z))=/spl Sigma//sub i=0//sup m-1//spl Sigma//sub j=0//sup n-1/a/sub ij/z/sup mj+i/ where a(z)=/spl Sigma//sub j=0//sup n-1/a/sub j/z/sup j/ and a/sub j/=/spl Sigma//sub i=0//sup m-1/a/sub ij//spl alpha//sub i/, a/sub ij//spl isin//spl Zopf//sub 4/. Then, for any linear code C of length n over GR(4/sup m/), its image d/sub /spl alpha/_/(C) is a /spl Zopf//sub 4/-linear code of length mn. In this article, for n and m being odd integers, it is determined all pairs (/spl alpha/_,C) such that d/sub /spl alpha/_/(C) is /spl Zopf//sub 4/-cyclic, where /spl alpha/_ is a basis of GR(4/sup m/) over /spl Zopf//sub 4/, and C is a cyclic code of length n over GR(4/sup m/).     

CDMA2000 1/spl times/EV-DO revision a: a physical layer and MAC layer overview

This article presents key enhancements to CDMA2000 1/spl times/EV-DO systems embodied in 1/spl times/EV-DO Revision A. These enhancements provide significant gains in spectral efficiency and substantial improvements in QoS support relative to 1/spl times/EV-DO Revision 0. In particular, 1/spl times/EV-DO Revision A approximately doubles the uplink spectral efficiency and doubles the number of terminals with delay-sensitive applications that can be simultaneously supported on the system. It provides substantial reduction in latencies (approximately 50 percent) during both connection setup and the connected state. It offers comprehensive network control over terminal and application performance to enable the desired trade-offs between capacity and latency/ fairness, thereby providing full QoS support and enhanced user experience. It also provides coverage improvement (approximately 1.5 dB) relative to 1/spl times/EV-DO Revision 0. This enables operators to offer services such as VoIP, video telephony, mobile network gaming, push-to-talk, Web browsing, file transfer, and video on demand to a larger number of simultaneous users. The 1/spl times/EV-DO Revision A network can provide downlink sector capacity of 1500 kb/s and uplink capacity of 500 kb/s (two-way receive diversity) or 1200 kb/s (four-way receive diversity) with 16 active users per sector, using just 1.25 MHz of the spectrum.     

Large field-induced refractive-index change on TM-polarized light in an InGaAlAs-InAlAs MQW waveguide structure

For optical modulation devices with low-loss and high efficiency, we have investigated field-induced refractive index change (/spl Delta/n) and absorption change (/spl Delta//spl alpha/) in the large detuning wavelength region where absorption is almost negligible using an InGaAlAs-InAlAs MQW waveguide structure. The result shows larger /spl Delta/n induced on TM-polarized light than that on TE-polarized light. Moreover, in induced on TM-polarized tight can become smaller than that on TE-polarized light. This suggests that TM-polarized light is more useful for low-loss and high-efficiency phase-modulation devices, especially large-scale matrix switches.     

Random properties of the highest level sequences of primitive sequences over Z(2/sup e/)

Using the estimates of the exponential sums over Galois rings, we discuss the random properties of the highest level sequences /spl alpha//sub e-1/ of primitive sequences generated by a primitive polynomial of degree n over Z(2/sup e/). First we obtain an estimate of 0, 1 distribution in one period of /spl alpha//sub e-1/. On the other hand, we give an estimate of the absolute value of the autocorrelation function |C/sub N/(h)| of /spl alpha//sub e-1/, which is less than 2/sup e-1/(2/sup e-1/-1)/spl radic/3(2/sup 2e/-1)2/sup n/2/+2/sup e-1/ for h/spl ne/0. Both results show that the larger n is, the more random /spl alpha//sub e-1/ will be.     

On The General Relation Between /spl alpha/ and Q (Correspondence)

The relation between the quality factor Q and the attenuation constant /spl alpha/ of a transmission line has been known as follows: /spl alpha/ = /spl beta/ / /2Q where /spl beta/ is the phase constant. Recently from the following relation of propagation constant at resonance /spl Gamma/(/spl omega//sub 0/) + /spl part//spl Gamma/ / /spl part//spl omega/ /spl Delta//spl omega//spl cong/ i/spl beta/(/spl omega//sub 0/), where /spl Gamma/(/spl omega//sub 0/) = /spl alpha/(/spl omega//sub 0/) + i/spl beta/(/spl omega//sub 0/). Yeh derived a general relation between Q and /spl alpha/, namely, /spl alpha/ = /spl upsi//sub p/ / /spl upsi//sub g/ /spl beta/ / /2Q where /spl upsi//sub p/, and /spl upsi//sub g/ are the phase velocity and group velocity of the wave respectively. This general relation can be derived very simply from the generally accepted definition of /spl alpha/ and Q.     

Parallel Pumping in Hexagonal Ferrites with the Dc Field Off the Easy Plane

This paper gives the theory of spinwave instability under parallel pumping in hexagonal Zn/sub 2/Y ferrites with planar anisotropy in the case of a sphere. The configuration considered in this paper is the one in which the dc field makes an angle /spl beta/ with the easy plane and the resultant magnetization lies at an angle /spl alpha/ to it. To obtain parallel pumping with this arrangement it is necessfly to align the RF field along the magnetization. This leads to a new spinwave spectrometer which allows the dependence of the spinwave linewidth upon the angle /spl alpha/ which the unstable spinwave makes with the c axis of the crystal to be determined. The experimental results obtained on two Mn-Zn/sub 2/Y single-crystal ferrite spheres show that the spinwave linewidth increases with the angle /spl alpha/.     

On /spl Zopf//sub 4/-linear Preparata-like and Kerdock-like codes

We say that a binary code of length n is additive if it is isomorphic to a subgroup of /spl Zopf//sub 2//sup /spl alpha// /spl times/ /spl Zopf//sub 4//sup /spl beta//, where the quaternary coordinates are transformed to binary by means of the usual Gray map and hence /spl alpha/ + 2/spl beta/ = n. In this paper, we prove that any additive extended Preparata (1968) -like code always verifies /spl alpha/ = 0, i.e., it is always a /spl Zopf//sub 4/-linear code. Moreover, we compute the rank and the dimension of the kernel of such Preparata-like codes and also the rank and the kernel of the /spl Zopf//sub 4/-dual of these codes, i.e., the /spl Zopf//sub 4/-linear Kerdock-like codes.     

Estimating the parameters of semiconductor lasers based on weak optical feedback self-mixing interferometry

The paper presents a practical approach for measuring the linewidth enhancement factor /spl alpha/ of semiconductor lasers and the optical feedback level factor C in a semiconductor laser with an external cavity. The proposed approach is based on the analysis of the signals observed in an optical feedback self-mixing interferometric system. The parameters /spl alpha/ and C are estimated using a gradient-based optimization algorithm that achieves best data-to-theoretical model match. The effectiveness and accuracy of the method has been confirmed and tested by computer simulations and experiments, which show that the proposed approach is able to estimate /spl alpha/ and C with an accuracy of 6.7% and 4.63%, respectively.     

Evidence of crossover phenomena in wind-speed data

In this paper, a systematic analysis of hourly wind-speed data obtained from three potential wind-generation sites (in North Dakota) is analyzed. The power spectra of the data exhibited a power-law decay characteristic of 1/f/sup /spl alpha// processes with possible long-range correlations. Conventional analysis using Hurst exponent estimators proved to be inconclusive. Subsequent analysis using detrended fluctuation analysis revealed a crossover in the scaling exponent (/spl alpha/). At short time scales, a scaling exponent of /spl alpha//spl sim/1.4 indicated that the data resembled Brownian noise, whereas for larger time scales the data exhibited long-range correlations (/spl alpha//spl sim/0.7). The scaling exponents obtained were similar across the three locations. Our findings suggest the possibility of multiple scaling exponents characteristic of multifractal signals.