Telecommunication Engineering

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Browsing Telecommunication Engineering by Subject "Addis Ababa"

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    Inter-Cell Interference Mitigation in LTE-Advanced Network by Using Coordinated Multipoint Transmission Technique: The Case of Addis Ababa, Ethiopia
    (Addis Ababa University, 2021-10) Getaneh, Molla; Yihenew, Wondie (PhD)
    The number of mobile broadband subscribers is increasing along with mobile data traffic on the Ethiopian mobile network. Mobile customers are facing dissatisfied service quality as the number of subscribers is increasing due to resource sharing as well as increasing interference. To improve service quality, network optimization and expansion work has been continuously performed. In order to maximize network capacity and coverage, ethio telecom upgrading the cellular network by using Long Term Evolution Advanced (LTE-A), an indoor building solution system, and adding base stations/transmitters. In such networks, Inter-Cell Interference (ICI) becomes more challenging, which mainly affects network performance. So, to overcome the aforementioned problem, operators are required to develop an effective approach that adopts different interference mitigation techniques. This thesis study presents a Coordinated MultiPoint (CoMP) transmission technique that can be considered as an effective way to improve spectral efficiency and system throughput performance. The thesis focused on downlink ICI mitigation in the LTE-A network within Addis Ababa. Comparative analyses and evaluations were performed for various CoMP and non- CoMP schemes. Taking into account performance metrics such as Signal to Interference plus Noise Ratio (SINR), spectral efficiency, and system throughput by performing radio propagation using WinProp and system-level simulation using the static simulator Matlab. The performance evaluation of the simulation study results obtained that the SINR gain improves 1.2dB and 1.4dB for the intra-site CoMP system, the Dynamic Point Blanking (DPB) CoMP system improves up to 3dB and 1.9dB, and the Joint Transmission (JT) CoMP system improves 3.7dB and 2.8dB for the cell edge and average users respectively. Spectral efficiency gain improved by 1.4bps/Hz, 2.4bps/Hz, and 3.2bps/Hz for intra-site CoMP, DPB CoMP, and JT CoMP scenarios, respectively. In addition, the throughput gain was achieved at 33% and 15% for intra-site CoMP, 70%, and 45% for DPB CoMP, and 97% and 70% for JT CoMP for the cell edge and average users, respectively. Therefore, the proposed interference mitigation solutions have been proven to provide a significant performance improvement for the LTE-A network and are worthy of deployment on the existing Addis Ababa LTE-A networks.
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    Investigation and Optimization of Electrical Tilt and Azimuth for Addis Ababa LTE Network
    (AAU, 2018-11) Taddege, Assefa; Beneyam, Berehanu (PhD)
    Demand for mobile broadband connectivity is significantly increasing and mobile network operators are continuously improving their network by introducing new technologies to accommodate the demand. After mobile network is operational for the first time, to maximize network performance, it is common to perform further optimization of initially planned and configured network parameters. One important category of such network parameters that incur significant network performance impact is antenna parameters that mainly include antenna tilt and azimuth. Optimization of antenna tilt and azimuth plays a major role in optimization of coverage, capacity, load balancing and interference of mobile networks. Long Term Evolution (LTE) network is operational in some parts of Addis Ababa since 2015. This thesis work reviews Addis Ababa LTE network, deployed antenna solutions and ethio telecom antenna optimization practices. The work continues by evaluating the performance of this LTE network from electrical down tilt and azimuth steering perspective. Based on observed performance, the tilt and azimuth parameters are also optimized by applying educated trial and error approach. The performance evaluation and optimization of the network are performed through Signal-to-Interference-Plus-Noise-Ratio (SINR) and throughput parameters obtained using WinProp based network simulation backed by Matlab. Results show that, by optimizing electrical tilt, SINR and throughput can be improved by 12.5% and 4.4% respectively. On the other hand, there is negligible performance gain by optimizing the azimuth.
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    Optimization of Soft Handover for Addis Ababa UMTS Radio Access Network
    (Addis Ababa University, 2020-02) Nigussie, Beyene; Beneyam, Berehanu (PhD)
    Handover is an essential radio management technique of mobile communication to enable seamless communication while users move from one cell to another one. To mitigate impacts of interference on cell-edge users, third Generation (3G) supports soft handover where users can be simultaneously served by two or more cells, in addition to hard handover, where a user is served by only one cell. The number of soft handover users and their active cells determine the degree of soft handover overhead. The soft handover overhead data for the year 2018 of Addis Ababa 3G network is 87% average overhead, which is considerably beyond the maximum recommended value. This figure indicates the requirement to optimize the soft handover overhead using the soft handover related network parameters’ configurations. In this thesis, soft handover overhead performance of the Addis Ababa 3G network is analyzed. The spatial distribution of the overhead is visualized using data collected from the network management system. Furthermore, optimization of soft handover overhead is done through fine-tuning window add, pilot power, and electrical antenna down tilt. We apply a heuristic algorithm for the optimization considering potential sets of values for the optimization variables. Moreover, obtained results are compared with a result obtained using existing default network configuration parameters. For the sample 3G sites network simulation, we use WinProp while we also use MATLAB and Google Earth for soft handover performance analysis and visualization. Soft handover overhead performance analysis of 5 Radio Network controllers (RNCs) shows that the Addis Ababa network is within the range of 111 to 115% for the 90 th percentile. Sites in RNC4 using carrier three are selected for the simulation and optimization as 5 to 21 more number of radio links used comparing with the other three carriers. After optimization, results show that soft handover overhead and network capacity are considerably improved by fine-tuning the window add, pilot power, and antenna tilt parameters. For instance, soft handover overhead is reduced from 85.4 % to 57.7% and network capacity gain by 3.76% when using window add of 2 dB, pilot power of 7.5%, and electrical antenna down tilt by 2 degrees. Soft handover overhead is reduced from 85.4 % to 46.6% and network capacity gain by 5.72% when using window add of 1.5 dB, pilot power of 5% and electrical antenna down tilt by 3 degrees.
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    Performance Analysis of Spectrum Scenarios for Outdoor LTE Small Cell Planning: The Case of Addis Ababa, Ethiopia
    (Addis Ababa University, 2019-12) Bezuayehu, Zerihun; Beneyam, Berehanu (PhD)
    Due to the increasing penetration of smart devices and data intensive applications, mobile network operators are experiencing exponential data growth. In effect, network capacity limitation that leads to performance degradation is observed. To address this limitation, deployment of different types of small cells under umbrella macro network that results Heterogeneous Networks (HetNets) has been considered as one key capacity enhancement approach. In the introduction of HetNets, operator decision on spectrum allocation scheme significantly determines network performance. The Ethiopian sole telecom operator, ethio telecom, has recently started the path to operate and manage HetNets by deploying small cells within its existing macro network. Nevertheless, there is no thorough performance study on potential spectrum scenarios considering Ethiopia’s network environment so that an informed spectrum usage strategy is formulated. Spectrum scenarios can be cochannel, where small cells apply same frequency band used by macro cells, dedicated, where they apply different frequency bands or a hybrid of cochannel and dedicated. In this thesis, performance analysis is carried out for the spectrum scenarios formulated using 1800MHz and 2600MHz bands from network planning perspective while considering realistic network environment for selected area of Addis Ababa, Ethiopia. Multiobjective optimization based on Genetic Algorithm is applied for network planning. Network simulation is implemented using MatLab while propagation computation is performed using WinProp. Performance results show that, allocating dedicated 20MHz band for small cell in 2600MHz band provides better aggregate capacity than allocating dedicated same amount of band in 1800MHz. For instance, dedicated 20MHz in 2600MHz band achieves 0.036Gbps per square km more capacity than in 1800MHz band for around three small cells per sector optimal deployment. On the other hand, dedicated 20MHz in 1800MHz achieves 2.3% less user outage rate than dedicated same amount of band in 2600MHz with around three small cells per sector optimal deployment. With regards to small cell distribution, planning results show that outdoor small cell deployment is needed more in locations other than main street.
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    Techno-Economic Investigation of Street Furniture Usage for Outdoor Small Cell Planning: The Case of Addis Ababa, Ethiopia
    (Addis Ababa University, 2020-02) Addis, Ebba; Beneyam, Berehanu (PhD)
    For more than a decade, mobile network data traffic and users’ demand are considerably increased due to the advent of evolving mobile technologies, capable end-user devices and data-intensive content. Different forecasts show that the growth will continue for similar reasons. To accommodate the increasing network traffic and users’ demand, operators should continuously expand the capacity of their mobile networks using different capacity enhancing technologies. Network densification using small cells is one of the important capacity enhancement methods that are being implemented. To successfully exploit capacity benefits of network densification, efficient network planning is needed to address its deployment challenges including availability and cost of site, energy source and backhaul while minimizing interference and maximizing network capacity and users’ throughputs. Using street furniture including lamp posts and utility poles during the planning of dense/ultra-dense networks is being considered as one method to address the availability of sites and cost challenges. But technoeconomic benefits of using the furniture and usage methods are not studied in the context of Addis Ababa. In this thesis work, the techno-economic benefits of using the furniture from an outdoor network planning perspective for a selected area of Addis Ababa will be investigated. The outdoor planning optimization is performed using technical and economic objectives while considering lamp posts and utility poles of the selected areas as part of candidate locations for small cells. The multiobjective optimization is solved using Genetic algorithm and its implementation and result analysis are performed using MATLAB. Propagation computation for network simulation is undertaken using a deterministic dominant path model that is implemented within WinProp. Empirical economic analysis results show that using streetlamp posts and utility poles decreases deployment cost by 17% compared to using a new standalone pole (dedicated pole used for only small cell deployment). Furthermore, obtained Pareto optimal networks from outdoor planning simulation that considers 143 lamp posts and 81 utility poles as candidate cells provide 53 lamp posts and 43 utility poles. Thus, only 24% is consumed by street posts for 96 sites while for 13 sites using new standalone pole 57% of the total deployment cost is consumed.