Electrical Computer Engineering

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    PERFORMANCE COMPARISON OF CHANNEL MODELS FOR UFMC SYSTEM
    (Hawassa University, 2019-08-29) TILAHUN BELAYNEH MAMO
    This paper presents the bit error rate (BER) vs. signal-to-noise (SNR) ratio performance of channel models under UFMC system with 32- FSK, PAM, DPSK, 4-QAM, 16-QAM, 32-QAM, 64-QAM and 128-QAM modulation. In future it is believed to be more challenging and complicated with the evolution of different types of fading model. These types of fading models determined in urban and rural areas. Rayleigh fading model is considered to be most common fading model, found in urban environment for non-line of sight. Rician fading consists of line of sight communication and found to be more applicable for satellite communication. Nakagami fading model is mostly suited for urban multipath propagation and it is sought to be most practical model, specially used in mobile communication. In order to achieve error free signal at the receiver the choice of modulation scheme should be done wisely. The combination of best efficient modulation scheme along with the block coding helps in getting the signal error free at the receiver. The condition of signal is decided by SNR v/s BER (bit error rate) simulation. Our main objective is to get error free result at the receiver, so for this different data transmission techniques are used to transmit the data from transmitter to receiver in various fading channels under different modulation schemes. Effect of shape factor on Nakagami fading is also covered in this thesis to get efficient results. The BER performance was to compared with Additive White Gaussian Noise (AWGN), Rayleigh-faded, Nakagami-m faded and Rician-faded channels. It has been further concluded that the BER vs. SNR performance graph in AWGN channel environment is better than that in Rayleigh, Nakagami-m and Rician-faded channel. It is also observed that by varying the standard-deviation of the channel, the BER vs. SNR performance graph is not going to be affected if the channel is considered Rayleigh-faded. In this paper we address a new aspect of UFMC system performance by investigating its capability to overcome the channel fading channels’ effects and to provide good and reliable performance levels overcome these channel effects.
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    PERFORMANCE ANALYSIS AND COMPARISON OF LINEAR PRECODING TECHNIQUES IN MASSIVE MIMO UNDER DIFFERENT FADING CHANNEL
    (Hawassa University, 2020-10-16) KETEMA TULLU
    Wireless communication and its featuring technology is continuously moving forward because of high demand in wireless communication services. Precoding techniques are very important in future telecommunication technology because in order to increase data rate the simplest method is increasing bandwidth. This method is difficult, because of scarcity in radio-frequency spectrum therefore, research over the last ten years has been focused towards improving spectral efficiency, so that higher data rates can be achieved with in a given band width for all above mentioned scenarios M-MIMO gives practical solution. Massive MIMO technology is now attracting attention of both academic and industry. This motivates us to work on this topic. Most of the studies considered the uplink performance. Here, we study massive MU-MIMO for down-link system with linear precoding. We deliberate the system performance when the number of antennas and the number of users are large. Our area of interest in this work focus on performance analysis and comparison of transmitter precoding so, it is very much essential to know all the aspects of precoding techniques. The main objective of this thesis is to analyze and compare the performance of linear precoding schemes in massive MIMO under Rayleigh fading channel and Rician fading channel. The performance Analysis and comparison issues include number of base station antenna, number of users, signal to noise ratio and Spectral efficiency under both complete and incomplete channel state information at the transmitter (CSIT) using MATLAB software. Finally from this thesis work it was observed that as the number of users increases the mathematical complexity of SINR and spectral efficiency increases for all MF, ZF and RZF linear precoding schemes. Generally, in thesis work it is observed that ZF gives better performances at all transmission power and in an increasing number of BS antenna over RZF and MF in both perfect and imperfect channel state information under Rayleigh and Rician fading channel.