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324 articles for “channel”
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Research ArticleOpen accessEvery word in the titlePerformance of MMSE Receiver based Multi Input Multi Output-Interleave Division Multiple-Access System with Multi-user Detection over Frequency Selective Wireless Communication ChannelKuttathatti Srinivasan Vishvaksenan, R. SeshasayananProblem statement: This study presents the performance analysis of turbo assisted Interleave Division Multiple-Access (IDMA) system with Multi Input Multi Output (MIMO) support for multi user scenario over correlated frequency selective and uncorrelated frequency selective channel. Approach: The key principle of IDMA is that interleaver unique which distinguishes the users in contrast to spreading sequence in Code Division Multiple Access … …Journal of Computer Science, Vol. 7, Issue 7 · 30 Jun 2011 · 6,834 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleSynthesis and Calcium Channel Blocking Activity of 1, 4-Dihydropyridine Derivatives Containing Ester Substitute and Phenyl Carbamoyl GroupBassem Sadek, Khairi Mustafa Salem Fahelelbom, Laurentiu Morusciag, Sigurd ElzProblem statement: Several studies on the synthesis of new nifedipine analogs have been carried out, but the literature reveled that no study on the synthesis and calcium channel blocking activity of the substituted ester with an amide (5-phenylcarbamoyl) moiety has been reported. Approach: Six new derivatives of m-nifedipine have been successfully synthesized by substituting an ester moiety with an amide … …American Journal of Applied Sciences, Vol. 8, Issue 4 · 18 Apr 2011 · 8,247 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleAnalytical Modeling of IEEE 802.11e Enhanced Distributed Channel Access under a Non-Saturation ConditionG. Prakash, P. ThangarajProblem statement: The IEEE 802.11e EDCA protocol with different access Categories (ACs) supporting for Quality-of-Service (QoS). Due to internal or external packet collision, the Contention Window (CW) of the station increases the channel idle time under high Bit Error Rate (BER). Approach: In this study, we propose an analytical model for performance evaluation of IEEE 802.11e EDCA scheme under non-saturation … …Journal of Computer Science, Vol. 7, Issue 4 · 4 Apr 2011 · 7,095 accessesView PDFCite
Research ArticleOpen accessEvery word in the titlePerformance Analysis of Multi-user Multi Input Multi Output- Interleave-Division Multiple-Access System Employing Turbo Coding with Multi-User Detection over Frequency-Selective Wireless Communication ChannelKuttathatti Srinivasan Vishvaksenan, R. Seshasayanan, Yuvaraj KrishnamoorthyProblem statement: This study presents the performance analysis of multi-user Multi Input Multi Output (MIMO) assisted interleave based multiple-access system. In IDMA, different interleavers are used to distinguish users as against different signature sequence in a conventional code-Division Multiple-Access (CDMA) scheme. Approach: The basic principle of IDMA is that the interleaver is unique for the users. Results: In this study, … …Journal of Computer Science, Vol. 7, Issue 2 · 25 Feb 2011 · 6,881 accessesView PDFCite
Research ArticleOpen accessEvery word in the titlePerformance Evaluation of Multi-Pulse Based Code Excited Linear Predictive Speech Coder with Bitrate Scalable Tool over Additive White Gaussian Noise and Rayleigh Fading ChannelsSuphattharachai ChomphanProblem statement: In the modern speech communication technology, the speech coding with bitrate scalability was needed. However, various types of noises in the communication channels cause damages in the transmitted information especially speech data. Tonal-language speech was also affected by this situation. Approach: Based on the high pitch delay resolution technique, the MPCELP speech coding was proposed over the environment … …Journal of Computer Science, Vol. 6, Issue 12 · 6 Nov 2010 · 7,085 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleHistory Based Contention Window Control in IEEE 802.11 MAC Protocol in Error Prone ChannelAli Balador, Ali Movaghar, Sam JabbehdariProblem statement: IEEE 802.11 Medium Access Control (MAC) protocol is one of the most implemented protocols in this network. The IEEE 802.11 controls the access to the share wireless channel within competing stations. The IEEE 802.11 DCF doubles the Contention Window (CW) size for decreasing the collision within contending stations and to improve the network performances but it is not … …Journal of Computer Science, Vol. 6, Issue 2 · 28 Jul 2010 · 7,662 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleIterative Channel Estimation Algorithm in Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing SystemsMona Nasseri, Hamidreza BakhshiProblem statement: The objective of this study is improving channel estimation accuracy in MIMO-OFDM system because channel state information is required for signal detection at receiver and its accuracy affects the overall performance of system and it is essential to improve the channel estimation for more reliable communications. MIMO-OFDM system was chosen in this study because it has been widely … …Journal of Computer Science, Vol. 6, Issue 2 · 28 Feb 2010 · 8,297 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleEfficient Detection Algorithm for a Multiple-Input and Multiple-Output Multiuser Multi-Carrier Code Division Multiple Access in Time-Varying ChannelsFares Sayadi, Mahamod Ismail, Norbahiah Misran et al.Problem statement: Maximum Likelihood (ML) decoding has been applied for the uplink of a Multi-Carrier Code Division Multiple Access (MC-CDMA) system based on Orthogonal Frequency Division Multiplexing (OFDM). Multiple-Input Multiple-Output (MIMO) channel from k users, which moves at vehicular speed, to the Base-Station (BS) is time-varying. For time-varying channels, Sphere Decoding (SD) was introduced to perform ML decoding. Whereas, computational … …American Journal of Engineering and Applied Sciences, Vol. 2, Issue 4 · 31 Dec 2009 · 7,576 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleWeighted Semi-Blind Channel Identification by Cross Relation MethodMohamed Tahar Taba, S. FemmamProblem statement: The bandwidth efficiency of many communication systems could be improved if the transmission channel was estimated blindly without resort to training sequences. GMSK was a spectrum-efficient modulation scheme and it was adopted as the modulation standard of GSM systems. Approach: However, because of its phase modulation, Gaussian filtering and partial response signalling properties, Results: The simulation results showed … …American Journal of Applied Sciences, Vol. 6, Issue 6 · 30 Jun 2009 · 6,891 accessesView PDFCite
Research ArticleOpen accessEvery word in the titleVoltage-Gated Channels as Causative Agents for EpilepsiesMutasem Abuhamed, Xiao Bo, Kun Xia et al.Problem statement: Epilepsy is a common neurological disorder that afflicts 1-2% of the general population worldwide. It encompasses a variety of disorders with seizures. Approach: Idiopathic epilepsies were defined as a heterogeneous group of seizure disorders that show no underlying cause .Voltage-gated ion channels defect were recognized etiology of epilepsy in the central nervous system. The aim of this article … …American Journal of Immunology, Vol. 4, Issue 4 · 31 Dec 2008 · 6,959 accessesView PDFCite