# UV System Architecture: Challenges and Evolution
## 1 Introduction  
The rapid advance in the research and use of unmanned vehicles (UVs) is undeniable. They are used in military and civil applications, and everything indicates that they will have greater use in the future. UVs have different names according to their operating environment. Using the definitions in [1], four types are defined depending on the medium in which they are mobilized: UAV (unmanned aerial vehicle), UGV (unmanned ground vehicle), UMV (unmanned maritime vehicle), and unmanned space systems. The latter does not have a defined acronym and corresponds to unmanned vehicles created for space applications. UMVs can be divided into two types: if they are surface vehicles (mostly boats or small ships), they are known as unmanned surface vehicles (USVs). If they are submerged, they are called unmanned underwater vehicles (UUVs). The Mars Rovers [2] are the most popular UGVs known to the public. In the specific case of rovers, they usually have a predefined route for data collection and, in some cases, soil samples or materials that they can collect along the way. Data are usually sent directly to the ground as they are collected, and in the case of soil samples, will be analyzed when the return to the ground base is determined. In most cases, the operation is usually largely autonomous and programmed in advance. Like any technology, there are problems and challenges to solve. One of those is the real-time response of a UV system to specific events, which, according to [3], is possible to classify into three categories: hard real time, soft real time, and firm real time. Hard real-time systems are those where the failure to respond in time means destruction. It is relatively simple to identify and sometimes hard to approach. Not responding within thetime period determined by the requirements implies destruction and/or inconsistency of the system. Soft real-time systems are those where the response quality can be defined as a function of time. There are time limits, but a response after the limit does not necessarily imply destruction or inconsistency of the system but rather affects the quality (e.g., temperature control of an environment). The longer the post-limit delays, the higher the level of degradation of the response quality. Firm real-time systems are those where the discarding of certain messages and/or responses is performed when necessary. The eventual absence/loss of a response within the time/deadline limit does not generate destruction, but it has no value either. It is discarded, like in streaming. The loss of a frame or block cannot be processed later in time. It is discarded and some quality is lost, but the video/audio is not lost. To explain the devolution of the proposed UV architecture, the minimum operating requirements are defined as the following: the UV architecture must include the system as a whole, as many of the architectures only involve the vehicle and do not consider the base station or the other components of the system; and the architecture must allow the use of different types of UVs (UGVs, UAVs, etc.) and the parts that form the system. Also, there are many challenges to resolve in a UV architecture. These challenges are addressed in the following topics:  
* Processing: devices (Arduino, Raspberry, and Custom), processor types, available memory, requirements, resources used, and navigation; relationship between available resources and processing requirements; optimization and analysis of requirements of real-time systems or subsystems. * Communications: types (Xbee, GSM, Wifi, and Satellite), range/reach, power consumption, interference, implementation complexity, and resources used; relationship between data and sensed information; capacity of available communication devices. * Sensors: types (video, image, sound, and scalar sampling), requirements, and resources used; study of the relationship between sampling frequencies, availability, and capacity of resources; impact on communications. * Power: power systems, energy consumption, and type of power supply.