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Titre : | Etude d'un système MC-CDMA dans un canal multi trajet associé à une technique de diversité |
Auteurs : | Dr. Aboura Lamia Touria, Directeur de thèse ; BOUAB Abdelkader, Auteur ; BEKHTI Saad, Auteur |
Type de document : | texte imprimé |
Editeur : | [S.l.] : Algèrie:unv saida-Dr Moulay Tahar, 2021-2022 |
Format : | 70p. / 29cm |
Accompagnement : | CD |
Note générale : | Bibliographie |
Langues: | Français |
Catégories : | |
Résumé : |
The MC-CDMA scheme is a promising technology for future wireless communication
systems. Future wireless communication requires a system supporting a large number of users, which can simultaneously provide high data rate. The MC-CDMA is a type of multiple access that utilize the benefits of both CDMA and OFDM schemes. The multi carrier part reduces the multipath fading and ISI, whereas the spread spectrum technology utilizes the limited spectrum in an efficient way. The high data rate transmission will make a resistive channel. The multi carrier part will overcome this problem by transmitting high data rate data into low rate parallel subcarriers. The overlapping of carriers provides high spectral efficiency. Compared to the other multicarrier technique, in a MC-CDMA scheme the original data symbols are first spread with a pseudorandom sequence, followed by the modulation on different carriers. That is, in a MC-CDMA system the chips of same symbol are modulated on different carriers. Hence the spreading is said to be done in frequency domain. In MC- CDMA the codes that is used to distinguish each user are modulated in frequency domain, hence the need of complex rake receiver is avoided. BPSK modulation is used as the modulation technique. The modulated outputs are then spreaded by a suitable spreading sequence in frequency domain and transmitted simultaneously on NC parallel subcarriers. The number of subcarriers is kept equal to the spreading code length. These parallel subcarriers are orthogonal to each other and can be generated using inverse fast Fourier transform (IFFT). Similar to an OFDM system, the MC- CDMA system reduces the interference between the successive symbols by cyclically extending the FFT block with cyclic prefix of NP samples. A parallel to serial converter (P/S) converts the parallel data into serial data stream. The signal is then transmitted through a channel having transfer function Hch (f) and the signal received at the receiver is affected by additive white Gaussian noise (AWGN) w(t) having power spectral density N0/2. At the receiver, the serial data is first converted into parallel and then subjected to the cyclic prefix removal. This step is followed by the fast Fourier transform (FFT) of the received signal. Finally, the data is retrieved after demodulating and decoding the received signal. The data is retrieved after demodulating and decoding the received signal. Finally we add a diversity combining technique to improve bit error rate in MC-CDMA system. The EGC combining improve the bit error rate slightly as compared with non combining system. MRC technique gives better BER performance as compared with EGC combining diversity techniques, but it is more complex in the design. |
Note de contenu : |
1-Generalities about wireless communications
2-MC-CDMA system 3-Simulation and results |
Exemplaires (1)
Code-barres | Cote | Support | Localisation | Section | Disponibilité |
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TECT01744 | T.EN.MS00601 | Périodique | Salle des Thèses | Electronique | Exclu du prêt |
Documents numériques (1)
Etude d'un système MC-CDMA dans un canal multi trajet associé à une technique de diversité Adobe Acrobat PDF |