Ethernet: The connectivity platform of choice for UAVs

Story

April 29, 2015

Ronen Isaac

MilSource

Ethernet has become the connectivity platform of choice for military unmanned aerial vehicle (UAV) system designers.

Fixed- and rotary-wing unmanned aerial vehicles (UAVs) are employed extensively by the military for reconnaissance, search and rescue, counterterrorism, and combat. UAVs function in missions where it is too dangerous, too difficult, or too demanding to send a pilot, whether the mission is in inaccessable terrain or a war zone, whether the objective is covert surveillance, a long-haul flight, or continuous extended observation.

Unmanned aircraft require the use of onboard computers and mission-critical equipment in order to support mission profiles. They use multiple sensors, including visual, infrared, near-infrared, radiation, biological, and chemical. The equipment uses multiple visual cameras to provide 180-degree forward and downward views for remote pilots and recording of mission data. Also on board a UAV may be short-range radios, satellite links, radar, and other tactical communications devices to communicate back to centralized command. All of these devices demand dependable, flexible, and fast connectivity to produce an onboard system that works in harmony and keeps the mission on track.

Ethernet – the well-established standard for wired connectivity technologies in government and commercial applications – is now rapidly becoming the standard for military and other rugged applications due to its proven interoperability, reliability, and speed. Dedicated bus architectures have been traditionally used in military applications, including UAVs, but have in the past resulted in heavier, proprietary, and inflexible systems.

Why Ethernet for UAVs?

Ethernet has been shown as a viable alternative for military UAV applications for a number of reasons:

Ethernet and IP technologies are ubiquitous
Ethernet devices are inherently interoperable, encouraging modularity
Rugged commercial off-the-shelf (COTS) components are readily available
Ethernet continues to receive large technology investments
Ethernet operates over world-spanning distances using established infrastructures

An increasing number of components in UAVs used by the military are now being modularized and connected via Ethernet.

The benefits of Ethernet connectivity in UAVs

First off, Ethernet is robust. Previous generations of connectivity were vulnerable to the elements that a UAV faced under normal conditions. Dirt, moisture, temperature deviations, and vibration can all reduce the efficacy and efficiency of standard bus architecture connectivity. Ethernet is a more solid and dependable connectivity platform; moreover, interconnectivity between switches can make these connections even more reliable. For example, multiple switches can be used in UAVs to provide redundancy and to eliminate the possibility of a single point of network failure. Switches are interconnected so that the failure of a switch or link between switches can be avoided by routing around the failure.

Ethernet also offers a diagnostic feature. Managed Ethernet switches can increase the resiliency of the internal communication of the UAV. The system can be set to self-detect and self-manage modules, thereby adding to the UAV’s uptime.

In some bus architectures, modules that communicate with each other via direct electrical connections can crash the entire system if one module fails. In Ethernet architecture, however, modules are electrically isolated so that if one module fails, the loss is limited to the loss of that module.

The modularity of Ethernet components also allows UAVs to have design and implementation flexibility. UAVs can be built for more than one function because of the flexibility of Ethernet components, and UAVs in the field can be modified on-site and outfitted to fit specific needs.

Ethernet can also help with size, weight, power, and cost (SWaP-C) concerns. Every ounce of decreased weight means more flight time for UAVs, so every ounce of component weight must provide and maintain optimal system performance. Each square inch must carry as much functionality as possible. Power management is also a challenge, and finding a balance for a deployed UAV is critical. Lightweight, rugged Ethernet switches are an excellent combination to make the most of SWaP-C pressures and constraints, as they save real estate room on a UAV for other devices.

Power over Ethernet

The power part of SWaP can be enabled by a concept called Power over Ethernet, or POE. It is a technology that enables a single cable to provide both data connection and electrical power to networked pieces of equipment such as sensors, IP video cameras, and even wireless mesh nodes. POE works across standard network cabling (i.e. CAT5) to supply power directly from the data ports to which networked devices are connected.

In traditional enterprise networking, POE has been implemented for years to help simplify the wiring of network devices – especially where running both electrical and CAT5 cables can be cumbersome and costly. In battlefield and avionics communications networks, using POE switches can provides both data connectivity and power on a single device to drastically reduce space requirements and wiring complexity on these mobile platforms. By eliminating power sources and associated wiring within a single mobile platform, these space-constrained platforms can use that much-needed space to support new devices to enhance communication and battlefield effectiveness.

Today the IEEE has two common standards for POE that support two levels of power classification. These two standards assure that all devices that use POE are compatible and will interoperate with each other. The original 802.3af POE standard provides up to 15.4 W of DC power to each device using 48 V. In most cases only 12.95 W is assured to be available at the powered device, as some power is dissipated in the cable. Examples of devices that only require this lower wattage power include standard IP cameras, most WLAN access points, and IP phones.

As remote devices became more complex and more compute power was required at the device, the electrical power needed to run them increased as well. Some of these devices include pan tilt zoom (PTZ) cameras and high-power wireless communications devices. More recently, the IEEE updated the standard to the 802.3at-2009 POE standard, also known as POE+ or POE plus, which provides as much as 25.5 W of power for these increased power requirements. Powering devices must support 30 W of DC power to compensate for dissipation in the cable.

When evaluating POE switches, one needs to evaluate the true power available in those switches. Although a switch may have, for instance, eight ports on the switch, the overall POE power budget for that switch may not be enough to support POE+ on every port. A full evaluation of what type of devices and their power draws need to be calculated and planned.

Long life

Finally, Ethernet boasts long design life: The Ethernet standard has been around for a long time – more than 40 years – which means that UAV designers can mitigate design obsolescence. The systems that employ it can enjoy a long life cycle.

UAVs are extending mission potential, mitigating risk, and increasing efficiency, enabling the modern military to undertake operations never before possible, in ways never before possible. As the desired functions for UAVs grow, UAV technology constantly faces new requirements and tasks, which calls for changing approaches to design and systems. Onboard Ethernet connectivity facilitates much of the design flexibility to meet the ever-changing demands for UAVs.

Progress in standards and speed

To keep up with the exponential demand for and sharing of data, Ethernet has taken some huge leaps in speed over the last five years. In 2010, the IEEE took an unprecedented step and ratified two Ethernet standards at once – the 40 GbE standard for local server applications and the 100 GbE rate for Internet backbones. Together these standards are known as Higher Speed Ethernet; 40 GbE consolidates four lanes of 10 GbE and 100 GbE consolidates four lanes of 25 GbE (a totally new technology). The 40 GbE implementation is gaining momentum in connecting servers and routers to each other within a data center (east/west traffic), while service providers are implementing 100 GbE in their network backbones (north/south traffic). Both standards require higher-speed optical fibers to make the connections.

Earlier last year, the IEEE started forming working group task forces to create standards to implement both 25 GbE (a single lane of the four 25-GbE lanes developed to support 100 GbE) and 400 GbE (the consolidation of four 100-GbE links).

As Ethernet becomes more and more pervasive as the technology of choice to connect devices and data transmission from person to desktop to home to cars over wired and wireless networks, it will continue to evolve. The beauty of Ethernet is that, as a standard, no matter what speed a device supports, all speeds are backward-compatible through switches and routers; moreover, devices that use Ethernet as a standard connection will always be able to communicate with each other.

It’s an exciting time for military embedded and non-embedded systems. Government mandates for COTS and standardization bring us one step closer to delivering the same commercial applications adoption rate to military applications that will enable us to protect and save lives.

Ronen Isaac is the general manager for Milsource. He has been designing and implementing corporate and government connectivity and video security solutions for the last 15 years. His newest company, MilSource, serves the U.S. market for ultra-compact, military-grade Ethernet connectivity for manned/unmanned aerial vehicles built from the ground up for SWaP-constrained environments. Readers may reach him at [email protected].

Milsource www.militaryethernet.com