# Emerging Trends in Hybrid Wireless Communication and Data Management for the Industry 4.0
## 5 Hierarchical and Multi-Tier Communication and Data Management for the Industry 4.0
### Hierarchical and Multi-Tier Network Architecture  
Hierarchical management exploits the different capabilities of the available communication technologies (wired and wireless) to meet the wide range of requirements of industrial applications. The architectural scheme is very well aligned with the concepts that are being studied for Industrial 5G networks. The support of very different communication requirements demanded for a wide set of industrial applications (from time-critical applications to ultra-high demanding throughput applications) and the integration of different communication technologies (wired and wireless) are key objectives of the designed architecture. In fact, the scheme focusses on the design of a communication architecture that is able to efficiently meet the varying and stringent communication requirements of the wide set of applications and services that will coexist within the factories of the future; by contrast to the architectures proposed in [32; 34], that are mainly designed to guarantee communication requirements of a given type of service (to provide connectivity to a massive number of communication devices in [32], and mission-critical wireless communications in [34]). In addition, it goes a step further and analyses the requirements of the communication architecture from the point of view of the data management and distribution. The architectural scheme considers an industrial environment covered by several cells that can implement heterogeneous communication technologies. These cells can overlap in space. In this case, network nodes or end-devices will connect to the cell that is able to most efficiently satisfy its communication needs. Figure 4 shows an example of an Industrial Wireless Network deploying heterogeneous technologies. Technologies 2 and 3 could represent WirelessHART and 5G technologies. Technology 1 is used to connect each cell through a local management entity, referred to as Local Manager (LM), to a central management entity represented as Orchestrator in Figure 4, and it could be implemented with TSN (the communication link between LMs and the Orchestrator could also be implemented by a multi-hop link using also heterogeneous technologies for improved flexibility and scalability (for example, IEEE 802.11 and TSN). As presented in Figure 4, we consider a hierarchical management that combines local and decentralized management with centralized decisions to efficiently use the available communication resources and carry out the data management in the system. In terms of communication management, the Orchestrator is in charge of the global coordination of the whole network. It establishes constraints to the radio resource utilization that each cell has to comply with in order to guarantee coordination and interworking of different cells, and finally ensure the requirements of the industrial applications supported by the network. For example, the Orchestrator must avoid inter-cell interferences between cells implementing the same licensed technology. It must also guarantee interworking among cells implementing wireless technologies using unlicensed spectrum bands in order to avoid inter-system interferences, for example, dynamically allocating non-interfering channels to different cells based on  
Figure 4: Hierarchical and heterogeneous Industrial Wireless Network architecture. the current demand. LMs are implemented at each cell. A LM is in charge of the local management of the communications and radio resource usage within its cell and makes local decisions to ensure that communication requirements of nodes in its cell are satisfied. LMs are in charge of management functions that require very short response times, such as Radio Resource Allocation, Power Control or Scheduling functions; these functions locally coordinate the use of radio resources among the devices attached to the same cell. In addition, LMs also report the performance levels experienced within its cell to the Orchestrator.