Multi-carrier spread spectrum (MCSS) communication systems are able to mitigate the effects of fading, interferences and Doppler frequency shifts as well as to support multiple access schemes. It is possible to get optimum performance from MCSS systems by carefully choosing the spreading sequences. However, due to inter-user interferences, performance degrades as the number of users increases unless the transmission channels are modeled and estimated. In this paper, we present a new spreading sequence obtained from a complex quadratic sequence multiplied by a pseudo random noise sequence, thus exploiting the properties of constant e . . .nvelope and statistical independence. Our approach is based on the time-frequency characterization of the wireless communication channel by means of discrete evolutionary transform. The properties of the new spreading sequence enables us to estimate the parameters of multi-user channels, both for uplink and downlink transmission cases, and design a receiver that is robust to channel noise, inter-user interference and intentional jammers. The performance of the proposed system is illustrated by simulations
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One must first make sure that a given matrix subject to factorization is symmetric, and then use it in Cholesky algorithm, in MATLAB. This may cost machine time to check for symmetry, however, saves much more of it by preventing errors due to inherent structure of the built-in algorithm.
Süreç kontrol endüstrisinde, orantı-türev-integral (PID) tip kontrolörler en önemli kontrol elemanlarından biridir. Uygulamada, analog kontrolörlerde genellikle işlemsel kuvvetlendiriciler kullanılmaktadır. Öte yandan ikinci nesil akım tasıyıcı ve akım geri beslemeli işlemsel kuvvetlendiriciler gibi akım çıkıslı olarak çalısan devreler, islemsel kuvvetlendiricilerle karşılaştırıldıklarında daha geniş bir frekans bandına, daha düşük güç tüketimi ile çalışma, ve daha iyi doğrusallık ve kararlılık özelliklerine sahip olduklarından, son zamanlarda oldukça çok dikkat çekmektedirler. Bu çalışmanın amacı akım tasıyıcılar (CCII) kullanarak . . .bir analog kontrolör gerçeklemek için gerekli tasarım yöntemini vermektir. Tasarımı yapılan PID devresi için optimum parametre toleransları hesaplanmıştır. Bu toleranslar önerilen PID kontrol edicinin duyarlık davranışlarının iyileştirilmesi ve kontrol edilmesinde kullanılabilirler.
In process control industry, the proportional-integral-derivative (PID) controllers are one of the most important control elements. In practice, operational amplifiers are generally used in analog controllers. On the other hand, current-mode (CM) circuits such as second-generation current conveyors (CCII) and current feedback operational amplifiers (CFOA) have considerable attention due to their wider frequency band, lower power consumption, better linearity and stability properties compared to their voltage-mode counterparts, operational amplifiers. The purpose of this study is to present a synthesis procedure for the realization of analog PID controller by the use of CCIIs. For the designed PID circuit, the optimum parameter tolerances are determined. These tolerances can be used to improve and to control the sensitivity performance of the proposed PID controller
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In this paper, the performance of turbo coded signals are investigated over a new channel model, denoted as 1 ± Dn / Partial Response Fading Channels (PRFC) with imperfect phase reference. The combined effects of the 1 ± Dn /PRFC and nonideal coherent receiver on the phase of the received amplitude and of a noisy carrier reference are considered, each modelled by the Rician and Tikhonov distributions respectively. As an example, the jitter performance of turbo coded signals are evaluated over 1D / PRSC channel with different fading parameter K, effective signalto-noise ratio in the carrier tracking loop a, iteration nu . . .mber and data block size N. The numerical results clearly demonstrate the error performance degradation due to both amplitude fading and phase noise process
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Bu makalede Turbo Kafes Kodlamalı (TKK) sistemlerin AWGN ve Rician ortamlarda faz bozulması durumunda hata başarımı elde edilmiştir. TKK yapısı ikili Turbo modülasyonu gibidir ancak TKK çok boyutludur. Turbo kodlamanın Kafes Kodlama ile birlikte kulanımı kodlayıcı yapısının değişimini gerektirir. Alıcıda ise ikili kodlayıcılarda olduğu gibi iteratif kod çözücü yapısı vardır. Burada 8PSK modülasyonda TKK farklı Rician katsayısı K, faz bozulma katsayısı a için benzetim sonuçları elde edilmiştir. Elde edilen sonuçlar hem genlikte hem de faz daki bozulmayı içermektedir.
In this paper, we investigate the performance of Turbo Trellis Code . . .d Modulation (TTCM) over AWGN, and Rician channels and assume that phase disturbance is available. As we know Turbo Trellis Coded Modulation (TTCM) is similer to binary turbo codes, but employs Trellis Coded Modulation (TCM) codes which include multi-dimensional codes. The combination of turbo codes with trellis codes leads to a strigthforward encoder structure, and allows iterative decoding as binary turbo decoder. However, iterative Turbo Decoder needs to be adapted to the decoding of TCM codes. Here, we investigate TTCM for 8PSK for several Rician parameter K and effective signal-to-noise ratio in the cafrier tracking loop a. Thus, our results will reflect the degredations both due to the effects of the fading on the amplitude of the received signal and of a noisy carrier reference
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Mineralized natural protein based novel bone replacement materials are investigated for tissue engineering. Mineralized silk fibroin composite foams and films display excellent biocompatibility. In this study, the biomimetic and electrochemical mineralization of orderly oriented silk fibroin scaffolds was studied. Commercially obtained pure silk woven fabric was boiled in 0.02 M Na2CO3 for 20 min. Calcium phosphate was deposited at 37°C for twenty minutes in seven sequential immersion steps, using 250 mM CaCl2 2H2O and 120 mM K2HPO4, containing 0.15 M NaCl and 50mM TRIS-HCl, pH 7.4, followed by electrochemical treatment in modif . . .ied SBF solution at 40°C at a current density of -25mA/cm2 for 60 min. The amount of biomimetically deposited Ca-P increased with the number of immersion steps. SEM images and XRD analysis of the Ca-P deposit indicated the initial formation of brushite with its monoclinic crystal structure and characteristic peak at 11.76 2?, and electrochemical conversion of brushite to hydroxyapatite on silk after electrochemical cathodization as confirmed by XRD and SEM analysis. Thus, a silk-fibroin-hydroxyapatite composite material prepared as a xenograft consisting of biocompatible components, and easily prepared as an economical bone segment replacement material with highly oriented fibers
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In this study,an electronic intra-oral artificial larynx system is designed. The objective of this study is to provide an alternative speech rehabilitation method to the totally-laryngectomized patients that will generate vibrations of fundamental frequency of human vocal cords. A prototype based on that design that is mounted into a dental prosthesis is established. The design of that system is presented in this paper.
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