Wherever emergencies happen, on a battlefield, across a disputed border, or as the result of hurricanes, floods, or fires, on-site communication managers face an immediate set of unnerving trade-offs.

Traditional spectrum management consists of frequency coordination that governs access to the available wireless capacity by strictly controlling all emitters in an area. However, when the number of satellites covering a small area limits the total available capacity, channel assignment is no longer enough and communication managers also want to establish dynamic use-policies that can be enforced in real-time.

The dispatch of tactical troops or civilian first responders relies on a high degree of confidence that no further harm or injury will occur to these responders.

Unmanned Aerial Vehicles (UAVs) are frequently used to survey an area to ensure no secondary explosions or attack are possible, followed quickly by tactical troops or civilian public safety officers to secure the area. Only then are recovery and medical teams allowed into the area to assist survivors.

During these events, the need for satellite communications capacity is insatiable. All UAVs demand downlink spectrum and data capacity for remote command and control, but today’s sensor and target tracking packages can also consume every amount of available uplink capacity in the area of the incident for the duration of the flight.

Tactical first responders rely heavily on satellite capacity during intelligence and reconnaissance missions as well as to enhance command and control through robust audio and video communications during any secondary actions, but are often forced to wait for any UAV activity in the area to end. Additionally, battlefield surgeons and EMS personnel are trained to operate autonomously, but the demand for remote surgical support is high.

Given enough satellite data capacity, tele-surgery based on live audio and video is being used with great success from the scene of the injury, saving lives that might otherwise have been lost.

Ideally, there would be enough satellite coverage over every affected area to offer each of these complementary operations full access to all the bandwidth they might require. The challenge of having enough satellite capacity exactly where it is needed will always be with us — we have to plan on deployments to locations that may have limited coverage.



Military Use Of Satellite Capacity
The Joint Network Node (JNN) / Warfighter Information Network – Tactical (WIN-T) program describes a steady increase in the use of satellite and terrestrial wireless networking for the future and builds upon the TCP/IP networks being used today.

This strategic architecture evolves from communications on the halt, to a fully integrated mobile communications infrastructure that includes support of UAVs or other airborne platforms and satellites, while fully extending mobile communications from the Brigade to the Company level in Increments 2 and 3. Net Ops resources at the Brigade level promise unprecedented levels of coordination and real-time management of the available wireless capacity once these future Increments are deployed.

Using The Available Capacity
Today, as different operational units gain access to satellite capacity, they each investigate and specify methods to improve the performance of TCP/IP applications over satellite to serve their individual missions. Working with the tools originally established for enterprise customers, these users have rapidly adopted commercial VSAT solutions to their unique needs.

In many cases, the users have simply selected WAN or application accelerators and deployed them in a tactical environment. These legacy products help avoid application issues related to the low bandwidth and high delay of satellite links. In each case, the operational units consume as much of the available spectrum as the equipment can access, but these users remain subject to a complete spectrum outage when an unmanned aerial vehicle enters the airspace.

We have reached a critical tipping point in the use and management of satellite capacity in tactical scenarios. Ideally, we could partition the spectrum and avoid conflicting use of overlapping channels by different functional groups. However, today, there is simply never enough capacity in any one area.

The spectrum coordination function and the command authority to dynamically restrict and manage the use of the available spectrum to include UAVs is defined as a part of Net Ops in WIN-T, but today, few devices in the wireless topology provide the functionality for dynamic policy enforcement.

Managing The Wireless Capacity
The immediate situation has resulted in a new class of equipment, the wireless optimizer, which is designed to optimize the performance of all applications using TCP/IP over the satellite network. These devices can also allow remote management of the wireless capacity in shared networking environments.

This device has many of the characteristics of traditional WAN or application accelerators as well as many distinct functions that have not evolved from the requirements of commercial enterprise users. These new functions come from the perspective of a wireless network operator. They relate to control and use of the spectrum and provide an immediate set of tools for military operators today.

A wireless optimizer must, first of all, be small and portable, ideally with a version of software that can be embedded in mobile terminals or handheld devices. The wireless optimizer must focus on very efficient algorithms for enhancing TCP/IP, often operating in very limited memory and CPU on mobile devices, unlike WAN optimizers that can always rely on substantial CPU, memory, and even disk storage in the devices where they operate.

Wireless optimization should be conceptually viewed as having a network based component as well as an edge device component and should be priced to address this wide variation in deployment models. Rate shaping and congestion control algorithms may be different on either end of a shared satellite space segment to fully maximize the data that can be sent over each link. Wireless optimizer software must accommodate different network types without sacrificing interoperability, the primary reason to continue to deploy products based on the Space Communications Protocol Specification (SCPS).

The other requirement for these network-deployed optimizers is one of policy enforcement. Remote programming interfaces (API’s) must exist that enable the Network Operations (Net Ops) center to dynamically control the amount of data each device in the shared network is allowed to transmit. The fact that wireless optimizers sit in-line, closely bracketing each satellite link, makes them the ideal place for further managing the overall spectrum from a central location. Once informed of the available bandwidth (or the allowed bandwidth), the optimizer must quickly shape the user traffic to this new level using rate control algorithms.

Remotely controlling the raw bits per second of space capacity that a user or a LAN is allowed to access, by updating the rate control algorithm using API’s, enables the Net Ops controllers to free up capacity for some users while locking down others, based on the tactical environment. The users of the network are assured their applications are operating at maximum capacity, even during periods when their bandwidth may be limited. Using embedded systems software, this function can be extended to ground based vehicles, UAVs, and man-portable systems.

By installing wireless optimizers across an organization, Net Ops can ensure that each operational unit is getting the maximum capacity from the bandwidth they are allocated while also using tools to balance the overall use of the available spectrum for the benefit of all users in the area. These techniques work hand in hand with operator based quality of service features. Additional wireless optimizer functions such as data compression, Internet caching, and pre-fetch ,all continue to operate over the programmable fixed rate control algorithm that is shaping the bandwidth to the configured data rate and are transparent to the end user.

In the best of situations, there may be plenty of satellite capacity to support on-going operations, where users are simply optimizing their applications over the space segment. However, in situations where satellite capacity may be limited, the use of wireless optimizers that have intelligent programmable rate control algorithms delivers an element of control over spectrum usage that is highly desirable today.

About the author
Jeff is the Director of Technical Marketing at Montreal based XipLink, a leader in the development of wireless optimization products and software. Jeff has been active in the digital and RF data communications industry for over 25 years and acquired his engineering education from the U.S.A.F. as a Space Systems Specialist and can be reached at 954.415.0870 or jweaver@xiplink.com.