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We address a recent application of realtime scheduling in wireless communication industry; namely, the uplink scheduling problem for WiMAX systems. More specially, we have worked on the problem of maximizing the number of data packets to be sent through an uplink subframe such that the expectations from the system are guaranteed. We argue that this problem is NP-hard. Thus far, only a number of heuristic...
Analysis of MESFET traveling wave multipliers (TWM) has been presented. Moreover, a systematic approach to its design has been presented. The analysis has revealed that the transmission-line attenuation and gate phase factor are the critical factors in the design of the TWM. In order to confirm these approaches two doublers were designed from 7 to 17 GHz, and the results are presented.
In this paper we introduce an effective bandwidth- based Call Admission Control (CAC) with adaptive modulation technique to manage the traffic in a wireless IP-based network. Since the next generation of communication networks will carry different classes of traffic, e.g., voice, video, fax, data and multimedia, over the same network and these different classes of traffic usually require different...
Expansion of virtual learning is one of the most suitable approaches for making higher education more accessible to everybody to meet all demands in society. Therefore there is a serious trend towards virtual learning in Ministry of Science, Research and technology (MSRT). E-learning in Iran, first, developed in the most famous and high-ranking universities like, Shiraz university, Amir kabir university,...
A quantitative analysis, leading to the design and optimization of an active microwave frequency tripler is presented in this paper. Optimum matching networks are developed which produced a stable design with conversion gain up to 2.5 dB for specific biasing condition. At the last the coupled filter in desired third harmonic and its characterizations are presented.
Speech recognition accuracy degrades in presence of additive noise especially when recognizer's training data are clean. Several methods have been proposed to compensate effects of noise on recognition accuracy among these methods missing feature techniques (MFT) have shown promising results in making speech recognition systems robust. In MFT spectral vectors of speech signal are conventionally modeled...
Speech recognition accuracy degrades in presence of additive noise especially when recognizer's training data are clean. Several methods have been proposed to compensate effects of noise on recognition accuracy among these methods Feature- Based Missing Feature Techniques, have shown promising results in making speech recognition systems robust. In these methods first corrupted parts of speech spectrogram...
Cross ambiguity function is a common method for joint estimation of TDOA/FDOA. CAF performance degrades in wideband situation. The maximum likelihood estimator in wideband model contains data resampling. Because of intensive computational burden data resampling isnpsilat viewed as a practical method. Calculation of short time CAFs and summation of them is suggested as a practical alternative method...
A direct conversion transceiver based on a five-port structure has been presented that is very suitable for ultra-wideband applications. The transceiver has been fabricated using microstrip components. The simulation and measurement results have been conducted to show its capabilities as a direct modulator and demodulator.
A direct conversion transceiver based on a five-port structure has been presented that is very suitable for WiMAX applications. The transceiver operates in a wide bandwidth of 2.3-3.8 GHz. This low cost transceiver covers two WiMAX bandwidths of 2.3-2.7 GHz and 3.3-3.8 GHz. The simulation results show the performance of transceiver for this application.
Cluster-based reconstruction is a feature based method that shown promising results in improvement of speech recognition accuracy but in low SNR values and multiple clusters, classification of noisy vectors is badly degrade the recognition accuracy. Main idea of this paper is to take advantage of phonetic properties and phonetic clustering to overcome disadvantage of classification step. We proposed...
Acoustic voice analysis is an effective, cheap and non-invasive tool that can be used to confirm the initial diagnosis and provides an objective determination of the impairment. The nonlinearities of the voice source mechanisms may cause the existence of chaos in human voice production. Voice pathology can cause to addition colored noise to voice wave. Added noise to a chaotic signal causes reduction...
This paper provides an intelligent method for medium and long-term energy demand forecasting of a complicated electrical system. In this method we use energy data of several past years to train an adaptive network based on fuzzy inference system (ANFIS). We use this intelligence network to estimate the time series behavior of energy consumption for several future years. Several simulations have been...
In this paper, the diversity-multiplexing tradeoff (DMT) for a multiple-input multiple-output (MIMO) channel with two transmitter and two receiver antennas (2times2 MIMO) at finite signal to noise ratio (SNR) has been studied. To characterize the trade-off, the outage probability of the mutual information between transmitted and received signals versus SNR is extracted. The diversity gain is the slope...
The particle swarm optimization (PSO) was showed to converge rapidly during the initial stages of a global search, but around global optimum, the search process will become very slow. On the other hand, genetic algorithm is very sensitive to the initial population. In fact, the random nature of the GA operators makes the algorithm sensitive to initial population. This dependence to the initial population...
A cross layer approach based on adaptive modulation (AM) at the physical layer and truncated automatic repeat request (ARQ) protocol at the data link layer has been presented. To realize the system the MIMO channel is decomposed into single-input single-output (SISO) channels, then the probability density function in these sub-channels is extracted and approximated by Gamma distribution. An upper...
In this paper, we consider multiple-input single-output (MISO) and single-input multiple-output (SIMO) systems, and study the diversity-multiplexing tradeoff (DMT) for them at finite signal to noise ratio (SNR). To characterize the tradeoff, the outage probability versus SNR is extracted. The diversity gain is defined as the slope at a particular SNR of the outage probability versus SNR curve and...
This paper provides an intelligence method for medium and long-term energy demand forecasting of a complicated electrical system. In this method we use energy data of several past years to train an Adaptive Network based on Fuzzy Inference System (ANFIS). We use this intelligence network to estimate the time series behaviour of energy consumption for several future years. Several simulations have...
Frequency synthesizer design issues for WLAN applications in IEEE 802.11n standard (draft) are proposed in a systematic aspect. A new concept is introduced on effective phase noise traded off with the settling time which is optimized through widening the loop filter band-width. Simulations are carried out through PLL Design Assistant. Expected phase noise and settling behavior of standard are translated...
An efficient FPGA implementation of an irrational CIC filter for decimation in digital receivers is presented in this paper. The proposed approach employs dual-port RAMs prevailing in almost all recent FPGAs, favorably decreases the number of used slices and increases the operating frequency. The circuit has been implemented on a Xilinx Virtex-II Pro XC2VP50-6 and has been used in some digital demodulators...
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