نتایج جستجو برای: cdma چند سطحی

تعداد نتایج: 102047  

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه تربیت مدرس - دانشکده برق و کامپیوتر 1391

در سیستم های طیف گسترده دنباله مستقیم (ds/cdma )، کاربران بطور همزمان از طیف فرکانسی یکسان برای ارسال سیگنال های خود استفاده می نمایند. در این روش به کاربران مختلف کدهای متمایزی اختصاص داده می شود. در کانال های چند مسیره، سیگنال دریافتی در گیرنده حاصل ترکیب نسخه های تاخیر یافته ی سیگنال اصلی است که منجر به تداخل بین سمبلی ( isi) می شود. مسئله ی آشکارسازی بهینه برای مقابله با تداخل دسترسی چندگان...

Journal: :IEICE Transactions 2008
Teruhiko Miyatake Kazuki Chiba Masanori Hamamura Shin'ichi Tachikawa

SUMMARY We propose a novel asynchronous direct-sequence code-division multiple access (DS-CDMA) using feedback-controlled spreading sequences (FCSSs) (FCSS/DS-CDMA). At the receiver of FCSS/DS-CDMA, the code-orthogonalizing filter (COF) produces a spreading sequence , and the receiver returns the spreading sequence to the transmitter. Then the transmitter uses the spreading sequence as its upda...

Journal: :Wireless Communications and Mobile Computing 2008
Farrukh Rashid Athanassios Manikas

Multi-Carrier Code Division Multiple Access (MC-CDMA) is a modulation scheme that combines the advantages of OFDM and CDMA to provide robustness against frequency selectivity in wireless channels. Arrayed MC-CDMA systems combine MC-CDMA and antenna array technology to harness the spatial and temporal ’signatures’ of received signals, thus making it possible to realize high transmission rates en...

Journal: :Wireless Communications and Mobile Computing 2003
Sharif A. Matin Okechukwu C. Ugweje

The performance of a multitone Code Division Multiple Access (CDMA) system is investigated in this paper by considering the effect of multipath fading, diversity and narrowband interference. The performance is evaluated in terms of the average bit error rate when both multiple access and partial band interference are present. Results are obtained by deriving the statistics of the receiver outpu...

2001
Claudio Sacchi Gianluca Gera Carlo S. Regazzoni

This work is aimed at investigating the use of Multi Carrier CDMA (MC-CDMA) techniques in variable bitrate transmission over low-earth-orbit (LEO) satellite channels by means of realistic simulations. It is known by literature that MC-CDMA techniques are much more resilient with respect to multi-user interference effects in multipath fading channels than single-carrier DS/CDMA ones. Moreover, M...

2011
B. Sarala

Code Division Multiple Access (CDMA) is currently dominating air interface technique used in wireless communications for 3G and 4G systems. Multicarrier CDMA has become the focus of current research interests in wireless digital communication. Multi carrier CDMA, Orthogonal Frequency Division Multiplexing (OFDM) techniques used for 3rd Generation and 4 th Generation wireless network systems all...

2011
Taeyoon Kim Jaeweon Kim Theodore S. Rappaport

A novel multi-code multicarrier code division multiple access (MC-MC-CDMA) system is proposed and analyzed in a frequency selective fading channel. By allowing each user to tl'ansmit multiple orthogonal codes, the proposed MC-MCCDMA system can support various data rates, as required by next generation standards, and achieve spreading gain in the time domain. Multicarrier CDMA provides robustnes...

Journal: :IEEE Transactions on Information Theory 2021

Barcoding photons can provide a host of functionalities that could benefit future quantum communication systems and networks beyond today's imagination. As significant application barcoding photons, we introduce code division multiple-access (CDMA) for various applications. In this context, discuss the fundamental principles novel CDMA (QCDMA) technique based on spectrally encoding decoding con...

Journal: :IEEE Transactions on Vehicular Technology 2001

Journal: :Journal of Information Security 2014

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