# UAV Support for Mission Critical Services
## 2 Status of Mission-Critical Solutions
Its data transmission capacity is at least two orders of magnitude greater, and its functionality is much richer than TETRA. The LTE-MC architecture is similar to LTE (see Figure 2). It should be noted; however, that LTE to LTE-MC adaptation requires a significant effort--several new 3 GPP specifications have been already published, and at least several dozens have been updated. Before the Rel 13 version (2016), the 3 rd Generation Partnership Project (3 GPP) started working on mechanisms useful for implementing LTE-MC services. In particular, LTE-MC uses multicast/broadcast eMBMS (Enhanced Multimedia Broadcast and Multicast Service) communication [7], group connections (GCSE) [8], extensions to the IMS platform [9] and device-to-device communication services, Proximity-based Services (ProSe) [10]. Thus far, the ProSe services are used for car-to-car communication V2X and are expected to be used for UAV-to-UAV communication, particularly in the context of a swarm. These services enable the terminal to be used for direct device-to-device (D2D) communications or a relay in such communications. Some enhancements, however, are needed regarding the use of ProSe services for MCS. The mission-critical service requirements for mission-critical communication described in [11; 12; 13; 14] (Rel 13 and 14) were largely met by the LTE architecture and protocol specifications of Rel 13, 14 and 15. 3 GPP standards provide the possibility of using LTE for advanced dispatch communication, including Push-to-Talk, Push-to-Video, location of users/devices, the possibility of integration with biometric or chemical sensors, the determination of brigades' position in the field and prioritization of resource allocation and user connections in networks based on commercial infrastructure. 3 GPP Rel 14 introduces extensions to Mission-Critical Push-to-Talk (MCPTT) [11], Mission-Critical Data (MCData) [14] and Mission-Critical Video (MCVideo) [13] services. The combined LTE-MC and IMS platform fully emulates TETRA network voice services (group communication, Push-to-Talk). In [15], an overview of 4G mechanisms used for public safety is presented. The 3 GPP is still working on:  
* the operating mode of the base station without connection to the network (MCS support in the Isolated Operation for Public Safety mode of operation, [16]) and
* extensions to existing standards regarding location functions [17]. An issue with the LTE-MC is the lack of available terminals supporting the ProSe services and their limited--by the current specifications--power, which provides a range of 1 km only for the 700 MHz band. A complete LTE network in the form of a knapsack was developed to ensure coverage in areas with no power supply. Such solutions only require a connection to the IP network for commissioning. They can be put into operation in several minutes, provide a range of several kilometres and have relatively low power consumption. Using such solutions significantly impacts the deployment strategies of MCS solutions. This means that, instead of building infrastructure across the country that can operate for a relatively long time in the absence of power (the TETRA case), a system of mobile LTE  
Figure 2: LTE-MC architecture. stations can be created within a few hours (i.e., the time when batteries power the normal infrastructure) can provide coverage for a selected area. By definition, it is not the area of the entire country or province. However, such a solution, which can be called _LTE-MC On-Demand_, should be standardized by 3 GPP, which will significantly popularize its implementation. The basis of the work may be the recommendation for the operation of the LTE-MC base station in the absence of a backhaul to the Evolved Packet Core (EPC) network [16]. In many countries, where narrowband critical communication networks (TETRAPOL and TETRA) have been installed, the migration to broadband solutions is now ongoing. A concise comparison of TETRA and LTE-MC is provided in Table 1.  
The 5 th Generation (5G) network is an evolution of LTE.