نتایج جستجو برای: مودم ofdm

تعداد نتایج: 10350  

Journal: :IEEE Transactions on Communications 2021

Orthogonal frequency division multiplexing with subcarrier number modulation (OFDM-SNM) has been recently proposed to improve the spectral efficiency (SE) of traditional OFDM system. In this paper, we propose a joint-mapping OFDM-SNM (JM-OFDM-SNM) scheme transmit signal vector constant length information bits by jointly considering activation patterns and constellation symbols. A low-complexity...

Journal: :international journal of information science and management 0
a. r. zolghadr asli ph.d. , e. e. dept., school of engineering, shiraz university, i. r. of iran b. amin shah m.s. , e. e. dept., school of engineering, shiraz university, i. r. of iran m. a. masnadi shirazi ph.d. , e. e. dept., school of engineering, shiraz university, i. r. of iran m. h. ghamat m.s. student , e. e. dept., school of engineering, shiraz university, i. r. of iran

one of the limitations of orthogonal frequency division multiplexing (ofdm) in many applications is its sensitivity to frequency shifts, errors normally referred to as carrier frequency offset (cfo). although, this small offset is negligible in conventional single carrier communication systems, it is a severe problem in the ofdm systems. because, the carriers in ofdm are inherently closely spac...

Journal: : 2021

OFDM-IM (İndeks Modülasyonlu Dikgen Frekans Bölmeli Çoğullama), 5G (Beşinci Nesil) ve ötesi iletişim sistemleri için aday iletim tekniklerinden birisi olarak son yıllarda üzerinde birçok çalışma gerçekleştirilmiştir. OFDM-IM'nin spektral verimliliğinin artırılması amacıyla geliştirilen OFDM-AIM (Tüm İndeks OFDM) tekniğinde, boş alt-taşıyıcıların bulunduğu OFDM-IM'den farklı tüm alt-taşıyıcılar ...

Journal: :Optical and Quantum Electronics 2023

A novel spectrally efficient modified asymmetrically and symmetrically clipped optical (mASCO)-OFDM for intensity modulated direct detection (IM/DD) systems is presented. The conventional ASCO-OFDM use two frames to transmit the (ACO)-OFDM (SCO)-OFDM system. proposed mASCO-OFDM system replaces frame SCO-OFDM by a single SCO (mSCO)-OFDM. mSCO-OFDM clips data on only one side of symmetry performs...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه علم و صنعت ایران 1380

در این پروژه نظریه نمونه برداری subharmonic مورد بررسی قرار گرفته و با استفاده از آن یک مودم dqpsk طراحی و شبیه سازی شده است . در این پروژه در ابتدا نظریه نمونه برداری subharmonic بررسی شده است و سپس مسائل آن نظیر: مقادیر مجاز نمونه برداری، نمونه برداری یکنواخت ، دقت نسبی فرکانس نمونه برداری، اثر باندهای محافظ و نویز در نمونه برداری مورد بررسی قرار گرفته است . در بخش بعد با استفاده از این نظریه...

Journal: :Photonics 2023

The performance of Low-Density Parity-Check (LDPC)-coded Orthogonal Frequency Division Multiplexing (OFDM) is investigated over turbulence channels in underwater wireless optical communications (UWOC). relation between the bit error ratio (BER) and parameters such as scintillation coefficient, signal-to-noise (SNR), length LDPC code, order OFDM quantified by simulation. Results show that while ...

Journal: :Photonics 2022

Non-orthogonal multiple access (NOMA) is deemed to be a prospective technology of the next generation. However, in visible light communication (VLC), when advanced hybrid optical orthogonal frequency division multiplexing (O-OFDM), such as asymmetrically clipped O-OFDM (HACO-OFDM), combined with NOMA, error propagation induced, which degrades system performance. Therefore, novel reconstructed O...

Journal: :IEEE Communications Letters 2022

Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which transmits information bits via $M$ -ary constellation symbols and indices of the active subcarriers, is a promising OFDM-based multicarrier transmission...

Journal: :Photonics 2021

Conventional optical orthogonal frequency division multiplexing (OFDM) schemes, such as adaptively biased OFDM (ABO-OFDM) and hybrid asymmetrically clipped (HACO-OFDM), are unable to tap all the resources of subcarriers only achieve relatively high power efficiency. In this paper, a adaptive bias (HABO-OFDM) scheme for visible light communication (VLC) is proposed improve spectral efficiency HA...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه علم و صنعت ایران 1378

حداقل پهنای باند صوتی تئوری لازم برای انتقال دیتای باینری با نرخ 9600 baud ، 4800hz است . چون یک رادیو nbfm معمولی دارای پاسخ فیلتر نشده از صفر تا 8khz است انتقال نرخ بیت 9600 از چنین سیستمی ممکن است . این طرح یک طراحی با کارایی بالا و حالت دوطرفه(full duplex) است که برای بسته هایی که از nbfm رادیویی باند صوتی استفاده می کنند و همچنین ماهواره هایی که با این مشخصات رادیویی سازگار باشند مناسب است...

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