Browsing by Author "Ruhama Girma"

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    ILP Based Optimal BBU Pool Planning for Cloud-RAN Deployment: in the Context of Ethiotelecom
    (Addis Ababa University, 2023-08) Ruhama Girma; Yihenew Wondie (PhD)
    Cloud radio access network (C-RAN) is a novel mobile network architecture that decouples the baseband units (BBUs) from their corresponding cell sites and takes the baseband processing unit to a virtualized and shared central location. This increases wireless networks' scalability, manageability, and significantly saves both the capital and operational costs of mobile network operators (MNOs). Although this BBU centralization enables power savings, it imposes much higher bandwidth on the fronthaul network. Since with distributed radio access network (D-RAN) there is a higher building, maintenance and operational costs there should be a RAN architectural change, and in addition to previously done researches in this area this thesis comprise the impact of wireless interface delay on BBU centralization. We investigate the optimal planning of BBU pools for C-RAN deployment in the context of Ethiotelecom and shows how to optimally determine the required number of BBU pools for different use cases using an integer linear programming (ILP) optimization problem and calculates the required budget to deploy a single BBU pool. We also figure out which functional split is cost-effective for fronthaul networks while providing the centralization benefits. Simulation results show that the wireless interface delay has an impact on BBU centralization therefore it should be considered in the BBU pool planning process. On the other hand, the number of BBU pools required varies depending on the use cases considered, hence for the chosen area ultra-reliable and low latency communication (URLLC) services require 5 BBU pools, real-time functions such as voice over long-term evolution (VoLTE) require 3 BBU pools; in contrast latency-insensitive applications, such as email 2 BBU pools are sufficient to meet the required performance requirements. Furthermore, split option 7.2 was selected
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    Study on the Application of Just-In-Time Philosophy to Construction: A Case Study of Reinforcement Bar Production and Delivery System
    (Addis Ababa University, 2023-05) Ruhama Girma; Abraham Assefa (PhD)
    In cities like Addis Ababa, storage and working space are usually inadequate for construction projects. Construction materials like rebar require a lot of space for storage and production. For the temporary storage and production of rebar, some firms had to pay extra to rent space. Also, some use the roadside for storage and production areas. Furthermore, most activities performed during the construction process do not add value to the project but incur unnecessary costs and time that affect the project's performance. Therefore, this study intends to analyze the rebar production practice and explore whether applying the just-in-time concept to the rebar production and delivery system would be advantageous from the perspective of value. To achieve the study objective, case studies were carried out on two contractors. The contractors were selected based on their approaches to rebar production. The first one uses the on-site rebar production method, while the other contractor uses off-site rebar production with JIT delivery. The data collected from case studies was analyzed using descriptive analysis and by developing a discrete event simulation model. Finally, the study's findings revealed that there is a considerable amount of non-value-added and necessary but non-value-adding activities on site during the production of rebars. According to the simulation analysis result, off-site rebar production with JIT delivery is shown to decrease rebar production time, increase productivity, and decrease idleness of labor and machines. Additionally, the study revealed the motivating and challenging factors for JIT implementation. In general, on the basis of value, applying JIT to rebar production and delivery is efficient. Thus, it is important for construction companies to start considering the benefits of this production and delivery system.