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UAV and High Frequency Radio
Unmanned aircraft vehicles (UAV) have been in use for some 30 years and used for a variety of purposes. Most commonly, these aircraft are used for military or scientific reconnaissance missions, where data is gathered to improve the ability of professionals to perform their duties. There are, however, a variety of challenges that must be met when these aircraft are in use. One of these is the way in which communication and navigation occurs in order to ensure that no accidents or crashes occur. Because there is no visibility at the site of the aircraft's operation, the radio and video signals that are relayed to and from it must be of the highest quality and accuracy. These accuracy requirements present significant challenges for unmanned aerial vehicles, including available radio frequencies and the accuracy and compression of visual data.
Unmanned aircrafts can be referred to as either unmanned air vehicles or unmanned aircraft systems (Austin, 2010, p. 3). It is built up of a number of sub-systems, including the aircraft itself, the payload in the aircraft, the control station, aircraft launch, recovery sub-systems, support sub-systems, communication sub-systems (which would include the radio or video signals involved in steering the craft accurately, and transport sub-system. Because of these highly complicated sub-systems, it is vitally important to maintain accurate communications.
Part of these communications is the wider environment within which UAVs operate. This environment consists not only of other aircraft that must be taken into account, but also of certain rules, regulations, and disciplines (Austin, 2010, p. 3). Hence, while UAVs are certainly set apart from other air vehicles in terms of make-up and purpose, they cannot be regarded in isolation from other airspace traffic.
Because there is no aircrew aboard an unmanned vehicle, a ground-based subsystem should be in place to interface with the controls of the aircraft. This purpose is served by an electronic intelligence and control subsystem.
According to Clot (n.d.), there are two inherent challenges that concern unmanned aircraft. This involves communication and control. Communication involves obtaining data from the aircraft, while control, as the word suggests, involves manipulating the craft without in fact being on board. These functions are also known as Command and Control. Because space on the electromagnetic spectrum, used for these functions, is becoming increasingly scarce, UAV systems should be carefully placed to ensure their success. This is becoming an increasing challenge as the number of UAVs rise.
Communications in UAV operations are highly important, since a breakdown in communication can mean failure. All decision making therefore occurs either before or during the flight on the ground. Another important component is the fact that most flights are aimed at positioning payload. While most manned flights are involved in moving people and freight, unmanned flights tend to be concerned with payload.
In terms of communications, the main issue is frequency and how much data needs to be transmitted. There are a limited number of useable frequencies worldwide. Hence, an important issue is where major data processing will be carried out. This will determine design criteria for communications. Some UAVs have capabilities to process data onboard in order to minimize the amount of data to transmit.
Unmanned aircraft can be distinguished from drone aircraft in that the latter have zero intelligence and are required only for pre-programmed missions after which they return to base. There are no in-flight communications, and information gathered by the aircraft is generally only obtained after the mission is complete and the craft has landed.
In contrast, a UAV has some degree of automatic intelligence, which means that it is able to communicate with its controller to provide data such as images, position, airspeed, and altitude during its flight. It can also transmit information regarding its condition, including temperature and amount of fuel during its flight path. These communications can then be used to assess damage or faults and the corrective action that might be taken to avoid further damage or crashes.
One major challenge is handling the loss of communication between a UAV and its base. Some aircraft are programmed to search for the radio beam it lost or to switch to a different radio frequency to establish contact once again. Some craft have been fitted with a type of low-level artificial intelligence capability to increase its autonomy of operation.
Everaerts (2008, p. 1187) notes that, although there is no physical crew present in unmanned aerial vehicles, the actual crew involved in its mission is in fact larger than for more conventional aerial vehicles. Indeed, because of the communications and control systems involved, the vehicle itself is simply a prominent part of the entire system, as seen above. A reliable communication system link with the Ground Control Station is therefore vital. In cases where the craft flies higher than 150-200 m above the ground, communication links must also be established with Air Traffic Control authorities.
One important function of Unmanned Aerial Vehicles is that their use by the military. Sending these vehicles into enemy territory to gather intelligence regarding planned missions or offenses has the advantage of less danger to military personnel, while also making planning missions easier and more effective. However, one challenge these vehicles face is with communications (Defense Industry Daily, 2011).
During the U.S. wars in Iraq and Afghanistan, for example, thousands of UAVs were gathering and distributing enemy-related data. The challenge was, however, that each system was connected to its own proprietary subsystem, both for its in-flight control and its communications in terms of receiving and processing data. What made this difficult is that commanders needed access to all types of UAV information gathered in the areas of their operation.
For this reason, an effort was made to create a single Ground Control Station for all types of unmanned vehicles during military operations. This would increase the speed and ease with which information could be communicated to and from the vehicles. As mentioned, all data is disseminated by and returns to the Ground Control Station (GCS). Information received from the UAV is processed and rerouted via data link to the end user.
One example of this is the MQ-1 Predator UAV system, which includes four vehicles, one GCS, and a suite of UHF and VHF radio relay links. It also includes a C-band line-of-sight data link and Ku-band satellite data links. The craft has no onboard recording equipment, so all imagery recording occurs in the GCS. External communications occur by means of HF/UHF/VHF, cellular and landline phones, and hardwire connectivity via satellite. The craft is capable of delivering raw images or video on demand. The challenge with this system is that the GCS only controls one craft at a time and cannot control or process any information from vehicles other than the Predator. The same is true of other systems, such as the Global Hawks and other proprietary systems. This creates the problem mentioned above, that commanders cannot obtain all data in their areas from a single GCS. This can impact the timing and effectiveness of missions and potentially cost lives.
To handle this challenge, a tri-service UAS control segment working group was set up to define an open architecture for Ground Control Stations. The model the Pentagon used for the effort is NATO STANAG 4586. This model provides standards for command-and-control interfaces used by UAVs. This involves five levels of interoperability (Defense Industry Daily, 2011): 1) The transfer of data obtained from a UAV to a third party; 2) direct transfer of UAV data live from the vehicle via a ground station to a remote system; 3) onboard systems control by commanders; 4) in-flight control; and 5) full flight control, including takeoff and landing.
Another possible solution is to upgrade the One System developed to control the RQ-7 Shadow Tactical Unmanned Aerial System (TUAS). This system could also control other UAVs, which would therefore eliminate the problem of different command stations for different types of UAVs. Current upgrades required include a move towards a Universal Ground Control Station (UGCS). Such a station would control and process information from multiple unmanned vehicles at the same time, and also store this information for up to 30 days. The system is also based on Remotely Operated Video Enhanced Receiver (ROVER). This means that, in its current form, its capability extends to a wide range of UAVs and sources. By means of GPS technology, the system limits talk time among UAVs and recipients. Hence describing targets and coordinating attacks become much more time efficient and effective.
In addition to the more efficient distribution of data from UAVs of all types, the UGCS would also reduce accidents among UAVs. These are generally the result of procedural errors, ground station design, lack of situational awareness, and human error factors. A universal system would provide both situation awareness and operational capabilities.
According to Sharma and Chakravarti (2005, p. 29), UAV crashes are expensive. In addition to the reputation of the ground crew suffering as a result, other consequences include…[continue]
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"UAV's And Related Hf Issues", 29 December 2011, Accessed.21 October. 2016, http://www.paperdue.com/essay/uav-and-related-hf-issues-48702