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اداء التجميع المتعامد لاشارات تقسيم الشفرات المتعدد الوصول ذات الحاملات المتعددة (Rayleigh) عبر قناة الخفوت الترددية الاختيارية من نوع == Performance Of Group Orthogonal Multicarrier Code Division Multiple Access Signal Over Frequency Selective Rayleigh Fading Channel
Author name:
حارث اكرم ناصر العبيدي
Supervisor name:
مها جورج زيا
General topic:
Electrical, Electronic and Communications Engineering
Specific topic:
Electrical and Electronic Engineering
Degree:
Master
University:
Mustansiriyah University - College Of Engineering - Department Of Electrical Engineering
Language:
English
University location:
Baghdad
First pages:
34T523 - p.pdf
Abstract:
مع ظهور قنوات الخفوت الترددية الاختيارية المتعددة المسارات. اصبح نظام تقسيم الشفرات المتعدد الوصول (CDMA) يعاني من التداخل بسبب تعدد المستخدمين (MUI) والتداخل بين الرموز(ISI) ولكن مع التصميم المناسب لنظام تقسيم الشفرات فانه يوفر التفريق الى مسارات متعدد | In the presence of frequency selective multipath fading channels, code division multiple access (CDMA) suffers from multiuser interference (MUI), and intersymbol interference (ISI), but when properly designed, it enjoys multipath diversity. Orthogonal frequency division multiple access (OFDMA) is MUI free, and it does not enable the available channel diversity without employing error control coding. But coded OFDMA may achieve lower diversity than a CDMA system employing the same error control codes. In this work, the advantages of OFDMA and CDMA are merged to minimize MUI effects, and also to make the maximum available diversity for every user possible, this system is called group orthogonal multicarrier CDMA (GO - MC - CDMA).In group orthogonal multicarrier CDMA (GO - MC - CDMA) scheme, groups of users share a set of subcarriers. By carefully choosing group subcarriers, there is aguarantees that every user transmits with maximum diversity. MUI is only present among users of the same group, and is suppressed via multiuser detection, which becomes practically feasible by assigning a small number of users per group. The performance of GO - MC - CDMA system is analyzed with 3M bits/sec in two paths frequency selective Rayleigh fading channel. Moreover, simulations are carried out to illustrate the performance of GO - MC - CDMA with number of active users, number of subcarriers, space diversity combining technique, types of spreading code, type of data detection techniques, finally, the effect of near - far problem.
