In the 21st Century the provision of secure, reliable communications and data is paramount in maintaining national and global security and the safe deployment and operation of military forces. This article outlines the vital role that microwave technology plays, giving examples that illustrate the practical deployment of microwave systems and the logistical, climatic and operational environments they operate in.
Mirroring every other organization in this computer age, today’s armed forces are totally dependent on data. A constant supply of rich information is fundamental to the success of any form of military action, from peacekeeping and border control, to combined air and ground assault. Voice communications on the battlefield have always required robust networks, but modern communications networks have to carry much richer data. In addition to reliability, modern battlefield communications require high bandwidth to deliver video, high resolution images and graphical intelligence.
What would generally be viewed as boardroom tools are being deployed on the battlefield. For example, the Norwegian military is a heavy user of video conferencing, deploying 180 consoles throughout its bases, command centers and mobile outposts. With a geographically distributed force, such a system enables the chief of defense to ensure good communication down the chain of command.
Other modern communications may not be quite so accessible to the military in the field of operations. Unlike most organizations, the armed forces cannot rely on ready access to a mobile network, leased line, or other broadband connection. In many of their operating environments, there is little or no infrastructure. And even where the infrastructure exists, it may not offer the requisite levels of reliability and security. In a fast-paced environment, armed forces need networks that can be deployed quickly, whatever the geographical, weather, or security conditions.
Meeting the Challenges
One ally in this struggle is microwave technology, which has proven to be a reliable solution to the problem of quickly delivering secure voice and data services in the toughest of environments. High capacity links can be deployed in a matter of hours, spanning all manner of terrain, and surviving the most intense weather conditions. For example, in Afghanistan the Canadian armed forces have deployed a dedicated microwave network to support in-country operations and connect troops back to the command structure in Canada. Afghanistan is a country of weather extremes, with the northern lowlands reaching almost +50°C in summer, while bitter northerly winds from Russia and Kazakhstan can drive the temperatures down to –50°C in the mountains in winter. In a country with only one phone line for every hundred people, microwave has quickly provided a secure, reliable system of communications.
Also, in French Guiana, the French military has deployed a software-configurable microwave radio system that overcomes the challenges posed by the country’s dense jungles and river systems. The system links teams securing common borders with Suriname and Brazil, providing communications much more cost-effectively and at higher bandwidths than alternatives such as satellite.
Naval Deployment
These are just some of the many examples of land-based uses for microwave radio systems in military applications. A more unusual example is the US Navy’s deployment of microwave radios to command the world’s largest remote control battleship.
In March 2003 the decommissioned Spruance-class destroyer USS Paul F. Foster was handed over to the Naval Surface Warfare Center (NSWC) Port Hueneme Division to serve as the Navy’s new Self Defense Test Ship (SDTS) on the waters of the Pacific Sea Test Range off the coast of Southern California. The SDTS, which operates unmanned and under remote control, is used as a test platform for various US Navy defensive weapon systems. The SDTS provides a flexible test platform with reduced safety constraints compared with manned ships. During a typical live fire test, various threats are aimed at a decoy barge towed 150 ft. behind the unmanned SDTS, protecting the ship and its assets. Clearly, control of such an asset must be reliable; losing control of a remotely operated battleship would be problematic to say the least.
To address this issue NSWC Corona Division Telecom Engineering designed a state-of-the-art 45 Mbps (DS3) ship-to-shore, line-of-sight communications link for the SDTS to transfer control commands in one direction and send back telemetry. Spanning up to 50 miles, this would be one of the longest ship-to-shore microwave links in the world. The US Navy wanted to use cost-effective commercially available microwave systems, but needed to be able to support a complex path-protection scheme to increase link reliability. The system also needed to integrate with a stabilized antenna pointing system to enable communications to be maintained with the test ship, regardless of its position and attitude within the test range. This would enable constant remote control of the ship’s maneuvering and weapon systems during operations at sea.
Working with the Navy and its chosen contractors, Harris Stratex Networks provided an Eclipse Nodal Wireless system. This system is able to select the best signal operating between four independent links that are separated spatially and by frequency to ensure a high availability communications link over 50 miles of water.
The four microwave links operate in two parallel sets comprised of two frequency-diverse links operating in the 5 and 7 GHz bands. Traffic is duplicated over each link, with the best quality signal being selected at the remote site. Frequency diversity operates on this premise: since each link operates on a different channel frequency (in this case, in entirely different frequency bands) the propagation characteristics of each will be very different, with fading in each link uncorrelated to the other.
Consequently, when the signal received from one radio (the 5 GHz link, for example) is degraded, the signal from the diversity link (the 7 GHz link) will be less affected. The selection between the two available paths is performed automatically by an external switch/router.
Microwave radio systems are traditionally designed to operate on fixed links between two fixed sites, so special arrangements were made to ensure that the antennas at each end of the link remained aligned while the SDTS moved around the test range.
To achieve this, the ship and shore antennas and RF outdoor units (ODU) were mounted on special stabilized pedestals of the type that have been used for ship-based satellite communications systems. Each diversity ODU set is mounted on a separate pedestal, which remains locked onto the signal received from the corresponding set at the far end of the link.
The pedestal is able to automatically lock onto and track the signal using a combination of the radio received signal level (obtained from the ODU AGC monitoring point) and the ship’s GPS positioning system. This enables free, 360° movement and also allows the link to cope with changes in elevation and azimuth caused by the pitch and roll movement of the ship (see Figure 1).
A single shore communications tower hosts both sets of links, while the ship-based equipment is split between the forward mast and aft masts, respectively (see Figure 2). This enables the link to be maintained during ship maneuvering when either of the two ship-mounted sets is obscured from the shore site by the ship infrastructure. The system automatically switches between the fore and aft diversity radio ODU set when blockage or path failure occurs.
Mission-critical Microwave
This is just one example of the use of microwave technology. Because of the critical nature of their activities, military organizations often require rapid access to secure, reliable and flexible high bandwidth communications systems, even when there is little or no infrastructure available. Microwave is a proven technology capable of delivering these mission-critical attributes, and as such, can deliver high value solutions that meet the objectives of any military organization in extreme conditions, regardless of climate or terrain.
Wireless microwave networks are inherently less vulnerable and more reliable than networks using buried or pole-mounted copper or fiber. Since cable is a solid medium, wireline networks rely on a continuous connection deployed and physically secured every inch of the way between termination points. Overhead cables are vulnerable to extreme conditions, such as wind, rain, flood waters, falling and flying objects, and other hurricane conditions. Buried cables are primarily vulnerable to construction excavation (back hoe fade, in industry terminology) and tampering. Microwave technology uses the air as the transmission medium, so networks need only be secured and protected at each end of the links or hops within the network. In contrast, a cabled network, with miles of space in between, requires installation and maintenance across the full extent of the network. With a microwave system, network operators can dedicate their resources to making certain each site is fully secured against the most extreme elements, sabotage or attack.
These advantages make microwave systems a logical choice for military communications as they need only protect the links. For reasons of security, flexibility and rapid deployment, microwave systems can clearly be one of the most valued communications tools in military applications.
As vice president, marketing at Harris Stratex Networks, Shaun McFall provides overall direction for programs to position the company in its focus markets. He has been with the company since the formation of its UK subsidiary in 1989, when his initial assignment was in new business development, first in the UK and later the European market. In 1994 he relocated to the company’s headquarters in San Jose, CA, assuming responsibility for worldwide product marketing. He has accumulated over 20 years of experience in the wireless telecommunications industry, holding prior positions with two UK-based companies: Ferranti International Signal plc and GEC Telecommunications Ltd. He holds a BS degree in electrical and electronic engineering from the University of Strathclyde, Glasgow, UK.
