# Multi-RAT Orchestration Method for Heterogeneous Wireless Networks
## 2 State-of-the-Art  
Many types of services today (e.g., industry, healthcare, public sector, mass events, home automation, entertainment, media, etc.) require access to wireless networks as never before. While each vertical has its own specific needs, the demand for applications and services even within such a single market segment may vary significantly. An example of this is the production and industrial environment in factories, where there are various requirements for wireless communication types existing simultaneously. Needs in such environments range from low data rate and at the same time very low latency, closed-loop communication between (parts of) machines, interaction over real-time based on requiring high throughput and reliability 3D video transmission, collaborative robots and people, downloading large amounts of data--which are not time-critical, to updating machine software. In many cases, different applications and services must share the same wireless infrastructure and compete for access to limited spectrum resources, which makes it difficult to meet the QoS (Quality of Service) demand requirements for different types of services in the same environment within one network radio. Radio resource management that are currently available in wireless technologies have to manage extremes (ultralow latency, very high throughput, and very high reliability) and with divergent needs (low and high data rates, time-critical communication needs), which becomes possible (sometimes partially and not all at the same time) only in the current 5G network solutions (3 GPP rel. 16-17). Therefore, the development of wireless networks is currently taking place at different levels, which enable the creation of many parallel network slices [9], each of which creates a separate data stream dedicated to specific applications. There are also many types of radio interfaces, including Wi-Fi, 4G/LTE, 5G/NR, LoRa, Zigbee, Sigfox, and others embracing a wide range of different Radio Access Technologies (RATs). In a given market segment (e.g., factory), dedicated radio interfaces for different applications are typically used. Oftenit is a situation where the appropriate QoS quality and appropriate network parameters are available at a given location of the factory in one radio interface (RAT) and it is not possible in other RATs or some (noncritical) services may be performed with lower quality, e.g., in another radio interface, leaving adequate space for high QoS and Key Performance Indicators (KPIs) for critical services. Therefore, the concepts of using multiple different (from a technology point of view) radio networks (heterogeneous networks) are developed simultaneously by means of the so-called multi-RAT (multi-Radio Access Technology) networks [10]. In the concept of a multi-RAT heterogeneous network, service management is dedicated to ensuring the appropriate quality of services and its indicators for individual links (end-to-end E2E) without the need to use a defined one radio layer (RAT) at the start. The proposed network has a wireless architecture consisting of interfaces of many radio networks, ensuring tight integration of radio access through selected network interfaces and appropriate traffic control, data path selection, and aggregation of traffic flows from (and to) various sources, ensuring appropriate link parameters. This enables increased quality, a variety of network bandwidth variants, and increased network reliability with different QoS levels. In particular, it is possible to trace and control the traffic of users connected to several radio interfaces on a common higher layer control plane by means of an orchestrator managing these technologies and interfaces. This concept goes beyond the traditional 5G network solution, as the 5G network itself may be only one element of a wider multi-RAT network environment, characterized by specific features and various KPIs, which are not defined within the current 5G state-of-the-art solutions by ITU and/or 3 GPP for the 5G NR.