Enhancement of proposed OFDM-CDMA system by using dwt over selective fading channel

الملخص EN

High transmission bandwidth efficiency in mobile communication can be produced by schemes such as direct sequence code division multiple access (DS / CDMA) and orthogonal frequency division multiplexing (OFDM).

The combination of OFDM signaling and CDMA scheme has one major advantage (hat it can iower the symbol rale in each subcarrier so that longer symbol duration makes it easier to quasi-synchronize the transmission.

In this work, two OFDM-CDMA models were investigated.

Also in the work, OFDM-DS-CDMA model was presented.

For further enhancement, discrete wave؛et transform based OFDM system was proposed to improve the bandwidth efficiency by removing the cyclic prefix (CP).

In the proposed (DWT-OFD،M-CDMA) system IDWT and DWT replace the IFFT and FFT, respectively.

These systems were simulated and evaluated over Rayleigh selective fading channel.

The simulation results inciude a comparison between all systems with different spreading codes.

The result shows that the performance of OFDM system enhanced by CDMA system.

Furthermore, the perfcnnance of OFDM-CDMA systems is further enhanceed using the DWT,