Comparison of Frequency Domain Equalizers to Time Domain Equalizers in WCDMA

Author

Muhammad Atif Yaqoob

Summary, in English

Future mobile platforms will contain an increased amount of wireless technologies. As technologies mature it will be necessary to find synergies between them. This could be in the form of reusing hardware blocks and algorithms. By using Fast Fourier Transforms (FFT/IFFT) and performing channel cancellation/equalization in frequency domain for wideband code division multiple access (WCDMA) will provide us a platform which can support LTE and WiFi together with WCDMA. In this thesis, an equalizer based on Fast Fourier Transforming (FFT) the input signal, cancelling the propagation channel in frequency domain, and finally reverting to time domain using an IFFT would be devised for WCDMA. The performance of frequency domain equalizer is then compared with traditional time domain equalizer based on G-RAKE method for different performance metrics. To evaluate and compare the performance of frequency domain equalizer (FFT) with time domain equalizer (G-RAKE), a simulator is made in IT++. Several simulations are performed and the obtained results are analyzed in Matlab. Firstly, for channel estimation at the receiver, common pilot channel (CPICH) is used and multiple channel estimates are obtained to get a filtered channel estimate. Along-with CPICH pilot symbols, data symbols of a desired user and four other user‟s data symbols are transmitted from the base-station (Node B). Using QPSK signaling, un-coded bit-error-rate (BER) results of the desired data user are compared for the two equalization methods. Simulation results are obtained for single path and multi-path propagation channels with different delay spread values. Included in the modeling are one receive and transmit antenna, other cell interference, i.e., non-white noise, frequency errors at mobile station (UE), and analog-to-digital (A/D) quantization.

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