Amath Ndao thesis defense

Abstract : We live in a world where the demand for service is growing daily. The challenge is to manage all these demands while respecting delay and capacity constraints. To satisfy these demands, operators have to deploy more and more base stations. Building more base stations and implementing new techniques means high costs for mobile operators. The existing D-RAN architecture is not sufficient to solve the problem, because it does not facilitate the pooling of resources. In this context, the Open Radio Access Network (O-RAN) is proposed by the O-RAN Alliance, which holds great promise for flexible and efficient 5G wireless networks. The O-RAN architecture comprises three main units: the radio unit (RU), the distributed unit (DU) and the centralized unit (CU). The aim of this thesis is to minimize the system cost of radio networks. First, we analyze the throughput between O-RAN interfaces. Based on this analysis, we propose an efficient integer linear programming (ILP) model. The objective is to minimize the O-RAN cost as a function of DU placement while respecting delay and capacity constraints. Secondly, we combine O-RAN and the multi-band system and consider a RAN load that varies during the day, and study the placement of DUs for different frequency bands. First, we analyze the percentage of use, throughput and modulation and coding scheme (MCS) of each frequency band for each hour of the day. Based on our analysis, we propose an ILP model aimed at minimizing computation and routing costs. Thirdly, we investigate the optimal placement of DUs and the deactivation of unnecessary frequency bands. First, we propose an algorithm to find the number of frequency bands needed to satisfy user  demand for different reallocation periods. Based on these results, we formulate the problem of DU placement and frequency band deactivation in theform of an ILP whose objective is to minimize computational and routing costs. We have evaluated our models on a real topology. Our results give interesting indications of the savings achieved compared with the existing architecture.