works (“stovepipes”) may need to be set up for some types of traffic to ensure that their service requirements can be met.
Earlier sections of this report describe current and planned tactical information network use in some detail. This section briefly recapitulates and then proceeds to translate these traffic considerations into more general architectural demands on the tactical network.
Sensor feeds. A wide range of sensor data flows into a tactical network. These feeds range from such heavy flows as imagery and synthetic aperture radar (SAR) from airborne platforms, through lesser flows such as moving-target indicators (MTIs), and down to sporadic and light traffic from cues such as unattended ground sensors or underwater sensors. Most types of imagery do not need particularly accurate transmission; they can withstand fairly high bit error rates. But more highly processed information, such as MTI tracks, require quite reliable delivery.
Weapons control. Real-time control of weaponry can range from the exceedingly time-critical “in-the-loop” applications, such as shooting down incoming missiles in the cooperative engagement capability (CEC) system, to relatively undemanding “update” applications for tracking a slowly moving target. Traffic delivery deadlines can thus range from milliseconds, in the most demanding cases, to tens of seconds in the least demanding. In either case, however, extremely high reliability is required in the delivery of control commands to an in-flight weapon.
Common tactical picture. The common tactical picture is a human-visible representation of the current situation, delivered with the appropriate level of detail so that the operations personnel can understand those aspects of the situation relevant for them and make decisions accordingly. This type of application can be implemented in a number of different ways, and each will impose different types of requirements on the tactical network. As an example, the U.S. Army’s Force XXI Battle Command Brigade and Below (FBCB2) program uses a hierarchical reporting mechanism in which each moving platform reports its position to a server, at a rate depending on how fast it is moving. The entire picture is then periodically distributed to everyone and filtered down to its relevant details at each receiver. This particular implementation imposes a fairly heavy “background hum” of position (and related) information on the network, with short messages and required latencies on the order of 1 s. However, high reliability is not required because messages are constantly being resent. If one is lost, the next will probably get through.
Tactical command and control (C2). Many tactical commands will be given by voice. Some fraction, however, will be delivered as data messages.