# Multi-RAT Orchestration Method for Heterogeneous Wireless Networks
###### Abstract  
Currently, energy efficiency (EE) of wireless communication is essential where many wireless networks with different Radio Access Technologies (RATs) coexist together. The RATs can be effectively selected and managed on a higher level to achieve maximum EE and save energy, e.g., save batteries. The approach to wireless traffic steering in mobile networks with a proof-of-concept solution is presented in this paper, owing to the developed high-level multi-RAT (multi-Radio Access Technology) heterogonous network orchestration approach. Based on the high-level network orchestrator, which traces network indicators, it is possible to decrease the user mobile terminal energy consumption, keeping traffic speed at an adequate level. The solution discussed was implemented in an experimental testbed with Software Defined Radio transmission systems. Downlink and uplink data links were toggled among different RATs according to the decisions that were taken by the end-to-end multi-RAT orchestrator based on the received proper network traffic-related indicators. The authors focused on finding an adequate algorithm that allowed for reduced power usage in the user terminal and made the attempt to verify how to reach the power reduction without introducing RAT-specific rules. The results showed that the proposed orchestration EE reduction was observed (from \(11\%\) to \(42\%\) for two different scenarios) in relation to the single LTE network deployment. The orchestration compared to the Wi-Fi network does not provide EE gain (\(-7\%\) and \(0\%\), respectively), but allows the user to achieve a higher data rate (\(23\%\) and \(39\%\) gain, respectively), thus keeping the energy efficiency at almost the same level. wireless communication; network orchestration; multi-RAT; Software Defined Radio; 6G 202120130 August 20  
integrated networks from the transmission medium point of view [5; 6]. From a user point of view, usually only end-to-end (E2E) connection with a defined adequate quality based on defined KPIs (Key Performance Indicators) is needed--for example, expected throughput, delay, or others. In these future wireless networks, new requirements are expected that will also allow for the implementation of the E2E connections through various common managed radio interfaces via multi-RAT (multi-Radio Access Technologies) coexisting together. On top of this multi-network scenario, the E2E orchestrator placed outside a single RAN (Radio Access Network) may take the role of a data traffic controller, which will secure the proper indicator values (e.g., throughput), even including additional indicators that have not yet been defined for 5G networks (e.g., link-level energy savings, cost savings related to the spectrum fees or other factors, usage of unlicensed bands, or radio protocols with lower energy demand) [7]. Therefore, our work was undertaken to analyze the current directions of research in this field and to develop a practical prototype of the new type of wireless network orchestration. The main goal of our research was to develop a high-level solution to manage connectivity based on different indicators and to establish optimal decisions, for example--for user terminal power saving counters, taking into account the active monitoring of user throughput, as battery lifetime directly affects user experience--despite the fact that the performance matrices are good [8]. The paper is organized as follows. First, in Section 2, the current state-of-the-art is reviewed concerning heterogeneous wireless networks and SDR (Software Defined Radio) solutions, with particular emphasis on the solutions and practical tests that form the background of this work. Next, the energy efficiency aspects are presented. In Section 3, Materials and Methods, the concept and implementation of the proposed technical solution for the heterogeneous network orchestration are described. The measurement outcomes achieved in the testbed implementation are presented in Section 4.