Electrical Computer Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/74

Browse

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Comparative Performance Analysis of Channel Estimation Techniques for Massive MIMO System
    (Hawassa University, 2021-12-17) Ashenafi Gebre
    The need for an internet connection is growing universally, so people need much higher data rate connection to meet their need but every physical resource in communication like frequency band, transmit signal strength are finite. Within the given limited resource, higher data speed is accomplished by a new technology called massive Multiple Input Multiple Output (massive MIMO) system. Massive MIMO fulfills the high data rate requirement through antenna diversity gain. It is one of 5G wireless network technology with array antennas at both transmitter and receiver sides to providing high spectral and energy efficiencies. In massive MIMO, the signal obtained by the receiver is in different phase and amplitude from the transmission signal. Therefore, the system quality is highly depending on the accuracy of the channel estimation. Channel estimation plays a significant role in the performances of massive MIMO system because the dimension of the channels matrix is large, phase changes and noises are added when the signals pass through channel, these reduces the efficiencies of the whole system. To solve these problems, this Thesis focuses on the comparative analysis of pilot-based channel estimation schemes for massive MIMO system, which includes: Minimum Mean square Error (MMSE), Element Wise Minimum Mean Square Error (EW-MMSE), Maximum Likelihood (ML) and Least Square (LS) estimator with respect to Normalized Mean square Error (NMSE), Signal to Noise Ratio (SNR), Spectral Efficiency (SE), number of BS antennas, and number of computational complexities. Based on the simulation results, MMSE channel estimator has the best performance, followed by EW-MMSE, ML and LS channel estimators in terms of NMSE and SNR. And depending on the number of computational complexities of each coherent block as a function of BS antennas M with constant UE, the complexity of LS is less than that of MMSE, and it has almost the same complexity as ML and EW-MMSE. And also, according to SE with respect to BS antenna M, the MMSE provides the highest SE using the highest complexity, EW-MMSE and ML achieves a good balance between SE and complexity, and LS has the lowest complexity, but also provides the lowest SE. Finally, the result confirms that MMSE channel estimation technique has the best performance compared to EW-MMSE, ML and LS channel estimators with the cost of high complexity
  • No Thumbnail Available
    Item
    Performance Analysis of Modulation Techniques for 5G Networks
    (Hawassa University, 2018-03-17) GETACHEW HAGOS
    The new 5G cellular network systems will feature several innovative strategies as compared to existing LTE systems, such as extensive adoption of small cells, use of mm-wave communications for short-range links, large scale antenna arrays installed on macro base stations, cloud-based radio access network, cognitive radio etc. All these strategies will be impacted by the modulation format used at the physical layer. At the same time, 5G cellular networks will have more stringent requirements than LTE in terms of latency, energy efficiency and data rates, which again are impacted by the adopted modulation scheme. Hence, proper selection and utilizing efficient modulation scheme is critical. The current modulation technique such as orthogonal frequency division multiplexing (OFDM) suffers from high peak to average power ratio which results in low efficiency of power amplifier and increases the battery consumption. Moreover, the OFDM spectrum has high out of band side lobes or side lobe leakage causing problem of low spectral efficiency. Therefore, OFDM can fulfill the requirements of 5G wireless networks in a limited way. In order to overcome some of these drawbacks of OFDM, new modulation techniques for 5G communication systems are considered. Among them, Filter bank multicarrier (FBMC), and Universal filtered multicarrier (UFMC) are expected be in race to be considered for the selection. In this paper, we perform the performance analysis of OFDM, UFMC, and FBMC in terms of its spectral efficiency (SE), power spectral density (PSD), peak to average power ratio (PAPR), and bit error rate (BER) using the MATLAB software tools. We analyze the results by varying the parameters of the modulation techniques which affects the performance of OFDM, UFMC, and FBMC. The plot shows that, FBMC has better SE for large burst durations but for small burst duration the SE of UFMC is better. In terms of PSD and BER FBMC is better. In terms of PAPR UFMC is better. The result of this research will play a significant role in selecting efficient modulation scheme for the upcoming 5G cellular networks