Multiuser detection in cdma system and its simulation in Matlab

Abstract

Bu tezde, kanal kodsuz ve evri§im kodlu ilintisiz alicili dogrudan dizilerle kod payla§imh 9oklu eri§im (DS-CDMA) haberle§me sisteminin, toplanir beyaz Gauss giiriiltu (AWGN) kanalmda ve Rician faktorii 1, 10 ve 100 olan Rician kanahnda performansi incelenmi§tir.Yiiksek Rician faktoriinde, Rician kanali AWGN kanalma benzemektedir. Du§iik Rician faktoriinde ise Rician kanali Rayleigh kanalma yakla§arak sitemin performansi azalmaktadir.Kanal kodsuz ve evri§im kodlu sistemin mukayesesinde, evri§im kodlu sistem kodsuz sisteme gore olduk9a iyi performans gostermektedir. 1/2 ve 2/3 evri§im kod oranlarmm mukayesesinde ise, aym bit hata orani (BER), 2/3 kod oranma gore 1/2 kod oranmda daha dii§iik i§aret-giirultu orani (SNR) degerinde elde edilmektedir.

In this thesis, we investigated performance of uncoded and with convolutional coded direct sequence code division multiple access (DS-CDMA) with decorrelating detection communication systems in additive white Gauss noise (AWGN) channel and Rician channel with Rician factors of 1, 10, 100.Rician channel with a high Rician factor will gradually resemble an AWGN channel. But as the Rician factor is made smaller, the error performance degrades, finally approaching the Rayleigh limit.Comparisons of uncoded and convolutional coded system show that: convolutional coded system has much better performance than the uncoded system. Two different convolutional code rates, which are 1/2, and 2/3 are tested. It is observed that for the same bit error rate (BER) value, at the code rate 1/2 has a lower signal-noise ratio (SNR) value than the code rate 2/3.