Browsing by Author "Oumer, Berhan"

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    MMSE Rake Receiver MMSE Equalizer for DS CDMA UWB Systems
    (Addis Ababa University, 2012) Oumer, Berhan; Mekuria, Getahun (PhD)
    The increasing demand for portable, high data rate communications has focused much attention on wireless technology. Ultra Wide Band (UWB) waveforms have the ability to deliver megabits of information while maintaining low average power consumption within a short range. Therefore, UWB is regarded as a good PHY layer solution to the PAN applications. In accordance with recent FCC rulings, UWB systems are now allowed to operate in the unlicensed spectrum of 3.1 to 10.6 GHz, motivating renewed interest in the thirty year old concept of impulse radio. The main subject of this thesis is to develop and check the performance of MMSE Rake Receiver and MMSE Equalizer for DS-CDMA UWB Systems. Since UWB is characterized by longer root-mean square delay spread, this thesis work com- bines MMSE Rake receiver and a simple linear MMSE equalizer to combat severe ISI which is the result of long delay spread. The MMSE equalizer will be done both in time and frequency domain and comparison will be made. Using MRC rake receiver the simulation results illustrate that an ideal ARAKE receiver using DS-BPSK-UWB transmitted signal format has the best perfor- mance for all type of channel models. The result also shows that at higher SNRs MRC rake receiver exhibit an error oor and, appending an equalizer on MRC rake is better than employing additional rake ngers, especially at higher SNRs and relatively large number of ngers. The proposed Rake-Equalizer outperforms the conventional rake receiver, which maximize the output SNR. The simulation also shows that the cascaded MMSE Rake-Equalizer achieves almost the same BER performance as MRC A-RAKE receiver for CM2 and frequency domain equalizer outperforms time domain MRC rake-equalizer at higher SNRs for CM4. All the above simulations have been conducted using MATLAB software.