Tactical communications are an essential part of the operational capability of unmanned aerial systems (UAS) – facilitating both the remote control of vehicles (UAVs) and mission payloads, and relaying status and camera/video surveillance (or other) payload data back to operators and users of the surveillance images.
Various communication options are available, depending on the size of the aircraft, logistics constraints (e.g. transportability) and the user’s access to frequency bands and associated dedicated infrastructure:
- Commercial off-the-shelf (COTS) solutions,
- Military or custom designed options, and
- Frequency modulation (FM) schemes
Each comes with its own topologies, restrictions and advantages.
Since not all users have access to satellite communication to begin with (and small-to-medium UAVs cannot carry satellite radios), users typically employ dedicated ground-air-ground Line-Of-Sight (LOS) data links to provide reliable communications.
This in turn presents various options and challenges including: the cost-prohibitive and technically challenging need to fly at sufficient altitude to “see over” the radio horizon; the problem of disseminating tactical data to the main point of use (typically near the target/point of ground based activity); and certain logistical constraints. Another risk factor is the possibility of deliberate interference with both the communication and navigation systems from opposing forces.
These problems can be overcome using a distributed networked communications architecture with multiple ground data terminals, linked and networked via a fibre or secure terrestrial microwave radio network.
This mode of operation allows two options:
- Operation by a single team (pilot and payload operator), with the link transferred via the network from one ground data terminal to the next and bringing about a manpower saving.
- Operation by physically separate teams, by connecting directly to the network (typically additional/alternate payload operators) – this ensures availability of payload data at the point of need, tactical flexibility and the option of using multicast Internet Protocol (IP) video from the aircraft by forward personnel located closer to the point of ground activity than the UAV operators typically working at a safe distance.
To solve the problem of GPS navigation system manipulation, one or more of the following alternative navigation solutions may be considered: Global navigation satellite receivers, or, if a LOS system is used, accurate monopulse azimuth tracking and ranging, or a digital elevation model used in conjunction with optical and aircraft based sensors for navigation.
A distributed architecture will not only solve the LOS problem but will also allow operators to keep UAVs at lower altitudes to ensure longer endurance, longer engine life, improved payload performance, reduced personnel costs if using a single team, and split UAV/payload control (physical separation of the aircraft and payload operators) if required.