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The Global Broadcast System (GBS) implemented by the U. S. Department of Defense utilizes commercially-based Digital Video Broadcast (DVB) technology to enable highrate (IO'S of Mb/s), one-way, data dissemination to a large number of users. Currently, however, user terminals are limited to receive-only operation. For many users, a receive-only configuration is not adequate and a low to medium-rate (10's to 100's of kb/s) return channel is required for true network-centric operations and enhanced mission effectiveness. This paper describes a frequency re-use architecture that provides such return channel connectivity to a large number of users without requiring additional satellite bandwidth and with minimal interference to current receive-only users.

One of the first military communication systems to realize the promise of network-centric operations is the Blue Force Tracking (BFT) global messaging system. The situational awareness gained from the Force XXI Battle Command Brigade and Below − Blue Force Tracking (FBCB2-BFT) includes a clear digital view of the battlefield with the geographic location of individual soldiers, weapons, command posts, vehicles, and operational facilities. The system also provides for the delivery of messages and other types of information to ground vehicles including tanks, armored personnel carriers, and infantry fighting vehicles, as well as U.S. Army rotary wing aircraft. Numerous stories from the battlefields of Iraq and Afghanistan recount how moving units were able to identify friendly forces that they at first thought might be enemy threats, saving lives each time. Now the satellite industry is at work developing a BFT system upgrade that will increase the accuracy and capacity of this vital network, and stretch its capabilities out to the farthest edge of tactical operations. The goal is to make it faster and easier to send and receive the short, instant messages that update the digital battlefield view. The system approach is based on spread spectrum technology which can dramatically reduce latency and increase the number of simultaneous users in high density operational environments. The introduction of a proven commercial satellite technology will accelerate the system upgrade and quickly get the capability into the hands of the warfighter. This paper describes the technologies being used for the upgrade and the system level improvements that will result. The high density waveform is expected to increase simultaneous return links from four to 30, cut round-trip latency from minutes to less than two seconds, and boost messages per minute from a maximum of 600 to 5000.

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