The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Akihisa Ushirokawa - One of the best experts on this subject based on the ideXlab platform.
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Multiuser space-time interference cancellation system for CDMA mobile communications
Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324), 1999Co-Authors: Naoto Ishii, S. Yoshida, Akihisa UshirokawaAbstract:An efficient combination of a smart antenna and a multi-stage multiuser interference canceller is proposed for W-CDMA system enhancement. In the proposed advanced receiver, interference cancellation is carried out at the Signal level before beamforming by regenerating a Spread Signal replica of each user Signal with the inverse beamforming process. Computer simulation demonstrates that the proposed space-time processing enables one to achieve a joint capacity gain given by the smart antenna and multiuser detection.
Atilio Gameiro - One of the best experts on this subject based on the ideXlab platform.
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VTC Fall - Frequency shift based multiple access interference canceller for DS-CDMA systems
IEEE 54th Vehicular Technology Conference. VTC Fall 2001. Proceedings (Cat. No.01CH37211), 2001Co-Authors: Luis Goncalves, Adão Silva, Atilio GameiroAbstract:The cyclostationary properties of direct sequence Spread spectrum Signals are well known. These cyclostationary properties imply a redundancy between frequency components separated by multiples of the symbol rate. We present a multiple access interference canceller that explores this property and applies it to UMTS-TDD. This frequency domain canceller acts on the Spread Signal in such a way that minimizes the interference and noise at its output (minimum mean squared error criterium). The performance is evaluated in two detector configurations: one including the frequency shift canceller (FSC) and the other plus a parallel interference canceller (PIC). The results are benchmarked against the performance of the conventional RAKE detector and the conventional PIC detector.
Xin Li - One of the best experts on this subject based on the ideXlab platform.
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The design and realization of Spread Signal tracking loop based on FPGA
2009 IEEE International Symposium on Industrial Electronics, 2009Co-Authors: Wei Wang, Xin Feng, Xin LiAbstract:The technology of spectrum Signal tracking and demodulation not only involves the designs of complex high-speed digital circuits, but also includes the designs of tracking algorithm. In the traditional design, the designers usually adopt the design methods based on FPGA&DSP to achieve all the above contents, which means that the carrier-DCO, code-DCO, the circuits of correlation and integral can be realized in the FPGA chip, while the tracking algorithms are realized in the DSP chip. Differing from the traditional design, this paper constructed one Nios II CPU core in the FPGA chip with the thought of SOPC technology, which made all the function modules could be realized in one FPGA chip.
T. M. Dirk - One of the best experts on this subject based on the ideXlab platform.
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Blind decentralized projection receiver for asynchronous CDMA in multipath channels
Annales Des Télécommunications, 1999Co-Authors: Irfan Ghauri, T. M. DirkAbstract:An asynchronous direct sequence code division multiple access (DS-CDMA) system employing periodic Spreading sequences is considered to be operating in a frequency selective channel. The cyclostationary Spread Signal is received at multiple sensors and/or is sampled multiple times per chip (oversampling), leading to a stationary vector-valued received Signal. Hence, such a model represents a very particular multi-input multi-output (MIMO) system with plentiful side information in terms of distinct Spreading waveforms for the input Signals. Depending upon the finite impulse response (FIR) length of the propagation channel, and the processing gain, the channel of a certain user spans a certain number of symbol periods, thus inducing memory or intersymbol interference (ISI) in the received Signal in addition to the multiple-access interference (MAI) contributed by concurrent users. The desired user’s multipath channel estimate is obtained by means of a new blind technique which exploits the Spreading sequence of the user and the second-order statistics of the received Signal. The blind minimum mean square error-zero forcing (MMSE-ZF) receiver or projection receiver is subsequently obtained. This receiver represents the proper generalization of the anchored MOE receiver [1] to the asynchronous case with delay Spread. Classification of linear receivers obtained by various criteria is provided and the MMSE-ZF receiver is shown to be obtainable in a decentralized fashion by proper implementation of the unbiased minimum output energy (MOE) receiver, leading to the minimum variance distortionless response (MVDR) receiver for the Signal of the desired user. This MVDR receiver is then adapted blindly by applying Capon’s principle. A channel impulse response is obtained as a by-product. Lower bounds on the receiver filter length are derived, giving a measure of the ISI and MAI tolerable by the receiver and ensuring its identifiability.RésuméCet article traite du problème de l’annulation de brouillage dans un système à accès multiple par répartition en code (AMRC) à séquence directe pour des canaux sélectifs en fréquence et des conditions asynchrones. Le Signal étalé cyclostationnaire est reçu par des antennes multiples ou est sur échantillonné par rapport à la période des bribes. Il est donc converti en un Signal vectoriel sta-tionnaire. Le sur-échantillonnage ou les antennes multiples donnent naissance à un système à entrées et sorties multiples (MIMO) disposant de nombreuses connaissances a priori relatives à la forme des séquences d’étalement distinctes pour les signaux d’entrée (utilisateurs), En fonction de la longueur de la réponse impulsionnelle finie (RIF) du canal de propagation et du facteur d’étalement, le canal d’un utilisateur déterminé s’étale sur un certain nombre de symboles, engendrant une interférence intersymbole (ISI) qui s’ajoute au brouillage d’accès multiple (MAI) dû aux utilisateurs concurrents. L’estimation du canal de l’utilisateur voulu est obtenue par une nouvelle technique aveugle qui utilise la séquence d’étalement de l’utilisateur et la statistique d’ordre deux du Signal reçu. Le récepteur à forçage de zéro minimisant l’erreur quadratique moyenne (MMSE-ZF) s’en déduit. Ce récepteur généralise au cas asynchrone et pour les canaux à trajets multiples le récepteur ancré qui minimise l’énergie à la sortie (MDE) [1]. Différents récepteurs linéaires sont obtenus par critères divers. On montre que le récepteur MMSE-ZF peut être réalisé d’une manière décentralisée en appliquant le critère MOE non biaisé, conduisant au récepteur à réponse sans distorsion et à variance minimale (MVDR) pour le Signal de l’utilisateur donné. Le récepteur MVDR est ensuite adapté en aveugle en appliquant le principe de Capon. Cela donne, par ailleurs, l’estimation de la réponse impulsionnelle du canal. En établissant des bornes inférieures sur la longueur du filtre de réception, on obtient une estimation de l’ISI et du MAI tolerable par le récepteur, ainsi que des conditions d’identificabilité de celui-ci.
Naoto Ishii - One of the best experts on this subject based on the ideXlab platform.
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Multiuser space-time interference cancellation system for CDMA mobile communications
Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324), 1999Co-Authors: Naoto Ishii, S. Yoshida, Akihisa UshirokawaAbstract:An efficient combination of a smart antenna and a multi-stage multiuser interference canceller is proposed for W-CDMA system enhancement. In the proposed advanced receiver, interference cancellation is carried out at the Signal level before beamforming by regenerating a Spread Signal replica of each user Signal with the inverse beamforming process. Computer simulation demonstrates that the proposed space-time processing enables one to achieve a joint capacity gain given by the smart antenna and multiuser detection.