Simulation Study of DITMC Technique for Enhancing Channel Utilization in Speech Communication of Mobile Network

Author(s):  
Hemant Purohit ◽  
Kanika Joshi
2000 ◽  
Vol 01 (03) ◽  
pp. 221-245
Author(s):  
EKRAM HOSSAIN ◽  
VIJAY K. BHARGAVA

The performance of a centralized traffic priority based dynamic burst-level cell scheduling scheme is investigated in a correlated fading channel. The scheduling scheme is designed for the transmission of multiservice traffic over TDMA (Time Division Multiple Access)/TDD (Time Division Duplex) channels in a WATM (Wireless ATM) network. In this scheme, the number of slots allocated to a VC (Virtual Circuit) during a frame-time is changed dynamically depending on the traffic type, system traffic load, TOE (Time of Expiry) value of the data burst and data burst length. While allocating bandwidth, the channel error status is also taken into consideration. SR-ARQ (Selective Repeat - Automatic Repeat Request)-based link-level error control is assumed for all the traffic types in a multiservice traffic environment. The performance of the proposed scheme under correlated Rayleigh fading is evaluated using computer simulation for realistic voice, video and data traffic models and the QoS (Quality of Service) requirements of different traffic classes in a wireless mobile network. Simulation results show that the proposed scheduling framework can provide reasonably high channel utilization with predictive QoS guarantee in a multiservice traffic environment. The channel utilization and the perceived QoS for different services is highly affected by the traffic burstiness of the corresponding traffic type. Such a scheme can result in an energy efficient TDMA/TDD medium access control protocol for broadband wireless access.


2006 ◽  
Vol 11 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Alexander von Eye

At the level of manifest categorical variables, a large number of coefficients and models for the examination of rater agreement has been proposed and used. The most popular of these is Cohen's κ. In this article, a new coefficient, κ s , is proposed as an alternative measure of rater agreement. Both κ and κ s allow researchers to determine whether agreement in groups of two or more raters is significantly beyond chance. Stouffer's z is used to test the null hypothesis that κ s = 0. The coefficient κ s allows one, in addition to evaluating rater agreement in a fashion parallel to κ, to (1) examine subsets of cells in agreement tables, (2) examine cells that indicate disagreement, (3) consider alternative chance models, (4) take covariates into account, and (5) compare independent samples. Results from a simulation study are reported, which suggest that (a) the four measures of rater agreement, Cohen's κ, Brennan and Prediger's κ n , raw agreement, and κ s are sensitive to the same data characteristics when evaluating rater agreement and (b) both the z-statistic for Cohen's κ and Stouffer's z for κ s are unimodally and symmetrically distributed, but slightly heavy-tailed. Examples use data from verbal processing and applicant selection.


Methodology ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 11-20 ◽  
Author(s):  
Gregor Sočan

Abstract. When principal component solutions are compared across two groups, a question arises whether the extracted components have the same interpretation in both populations. The problem can be approached by testing null hypotheses stating that the congruence coefficients between pairs of vectors of component loadings are equal to 1. Chan, Leung, Chan, Ho, and Yung (1999) proposed a bootstrap procedure for testing the hypothesis of perfect congruence between vectors of common factor loadings. We demonstrate that the procedure by Chan et al. is both theoretically and empirically inadequate for the application on principal components. We propose a modification of their procedure, which constructs the resampling space according to the characteristics of the principal component model. The results of a simulation study show satisfactory empirical properties of the modified procedure.


Methodology ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Jochen Ranger ◽  
Jörg-Tobias Kuhn

In this manuscript, a new approach to the analysis of person fit is presented that is based on the information matrix test of White (1982) . This test can be interpreted as a test of trait stability during the measurement situation. The test follows approximately a χ2-distribution. In small samples, the approximation can be improved by a higher-order expansion. The performance of the test is explored in a simulation study. This simulation study suggests that the test adheres to the nominal Type-I error rate well, although it tends to be conservative in very short scales. The power of the test is compared to the power of four alternative tests of person fit. This comparison corroborates that the power of the information matrix test is similar to the power of the alternative tests. Advantages and areas of application of the information matrix test are discussed.


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