Thesis Cdma System

Thesis Cdma System-51
It was found that OFDM performs extremely well compared with CDMA, providing a very high tolerance to multipath delay spread, peak power clipping, and channel noise.In addition to this it provides a high spectral efficiency.The main sources of these errors are frequency stability problems; phase noise of the transmitter; and any frequency offset errors between the transmitter and receiver.

It was found that OFDM performs extremely well compared with CDMA, providing a very high tolerance to multipath delay spread, peak power clipping, and channel noise.

Finally, I would like to thank my computer for only crashing seriously once during the writing of this thesis.

Multi-user detection allows for the efficient use of bandwidth in Code-Division Multiple-Access (CDMA) channels through mitigation of near-far effects and multiple-access noise limitations.

We investigate the bit error rate at both uplink and downlink for different channel conditions.

Performance improvement due to error correction coding scheme is shown.

The data is transmitted in a frame by frame basis through a time varying channel.

The transmitted signal is corrupted by multiple access interference which is generated in a structured way rather than treating it as Additive White Gaussian Noise (AWGN).The simulator developed can be an invaluable tool for investigating the design and implementation of WCDMA systems.Thesis submitted by Eric Lawrey in October 1997 in partial fulfilment of the requirements for the Degree of Bachelor of Engineering with Honours in Computer Systems Engineering at James Cook University.This can result in the carriers being lost in the noise.For the modulation schemes investigated (BPSK, QPSK and 16 QAM), clipping of the OFDM signal was found to have little effect on the performance of the system, allowing the peak power of the signal to be clipped by up to 6 - 9d B before the symbol error rate became significant.This tolerance to clipping reduces the dynamic range overhead required in output stages of OFDM transmitters.The noise performance of OFDM was found to depend solely on the modulation technique used for modulating each carrier of the signal.In a typical system a delay spread of up to 100 msec could be tolerated, corresponding to multipath reflections of 30 km.The only problem caused by multipath is frequency selective fading, which can result in carriers being heavily attenuated due to destructive interference at the receiver.The performance of OFDM was assessed by using computer simulations performed using Matlab, and practical measurements.These measurements were performed by recording a low bandwidth (audio) OFDM signal, generated using Matlab, on to a tape player.

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