) at the R station, one or more subcarriers having the lowest signal-to-noise ratios (SNRs) on both hops are first omitted, and then the SCM is performed. Analytical and simulation results have shown that in this way significant BER performance improvements are attained in the regions of medium and high SNRs

Abstract—In a multicarrier system, transmit power allocation over different subchannels is an effective means of improving the performance. We develop the optimal transmit power allocation scheme to improve bit-error rate (BER) performance in a mul-ticarrier system with diversity reception. A

Relevance feedback is an automatic process, introduced over 20 years ago, designed to produce improved query formulations following an initial retrieval operation. The principal relevance feedback methods described over the years are examined briefly, and evaluation data are included to demonstrate

The problem of mining sequential patterns was recently introduced in [3]. We are given a database of sequences, where each sequence is a list of transactions ordered by transaction-time, and each transaction is a set of items. The problem is to discover all sequential patterns with a user-specified minimum support, where the support of a pattern is the number of data-sequences that contain the pattern. An example of a sequential pattern is "5 % of customers bought `Foundation' and `Ringworld' in one transaction, followed by `Second Foundation ' in a later transaction". We generalize the problem as follows. First, we add time constraints that specify a minimum and/or maximum time period between adjacent elements in a pattern. Second, we relax the restriction that the items in an element of a sequential pattern must come from the same transaction, instead allowing the items to be present in a set of transactions whose transaction-times are within a user-specified time window. Third, given a user-defined taxonomy (is-a hierarchy) on items, we allow sequential patterns to include items across all levels of the taxonomy. We present GSP, a new algorithm that discovers these generalized sequential patterns. Empirical evaluation using synthetic and real-life data indicates that GSP is much faster than the AprioriAll algorithm presented in [3]. GSP scales linearly with the number of data-sequences, and has very good scale-up properties with respect to the average data-sequence size.

by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy systems. In this paper, we compare several schemes designed to improve the performance of TCP in such networks. We classify these schemes into three broad categories: end

the BER performance according to changing parameter, equation, and initial values of chaos map’s PDF. In addition, we propose new chaos map to improve BER performance. Simulation results show that BER performance of CDSK(Correlation Delay Shift Keying) is changed when PDF of chaos map changed

of the work we related the SNR and the error performance of MIMO systems with the diversity schemes, in the later part of the paper, implementations of different equalizers are also verified for the improvement of the BER performance. Each chapter is rounded by a number of simulations to deepen

of channel estimation accuracy and BER. Simulation results show the interest of considering the polarization as a channel parameter in order to increase the performance. Improvement in the path separation and received signal power is obtained and, because of this, channel estimation accuracy and data

Adaptive equalisers are characterised in general by their structures, the learning algorithms and the use of training sequences. This paper presents a novel technique of improving the performancc of convcntional multilayer perceptron(MLP) based decision feedback equaliser (DFE) of reduced

method with lower computational complexity is proposed and comparisons with the existing strategies are presented. The proposed selection criteria enable remarkable improvements in system performances with the addition of proportionally smaller number of extra antennas, comparing to the linear detection