A NUE Network Emulators are an essential tool for satellite communications testing providing vari- able path delays, jitter simulation, and dynamic error introduction, acting just like in a real satellite network link. High-bandwidth satellite networks provide a grow- ing variety of network services. Before these services can be deployed they must be thoroughly tested on the ground. Since satellites are frequently in orbits that are great distances apart, it is essential to emulate those dis- tances while testing on the ground. Round-trip transmission times to and from geo- synchronous orbit – where satellites park some 22,300 miles above the equator – are approximately 250 msec, a long time for a communications network! The satellites’ position is not constant and, in fact, because they communicate with both ground stations and other satellites, there will be transmission paths of many different distances to consider. Unlike a fixed length of fiber optic cable, the Network Emulator is like a variable-distance cable without dB loss, so it can be used for all-distances testing rather than specific- distance testing. Using Anue Nework Emulators to simulate satellite links WWW.ANUESYSTEMS.COM INFO@ANUESYSTEMS.COM +1 (512) 527-0453 • • ANUE SYSTEMS,INC. 9111 JOLLYVILLE ROAD SUITE 100 AUSTIN, TX 78759 U.S.A. • • • • Test Solution #301 Satellite Communications Satellite Communications The communication satellite is a moving object with a continuously-varying distance to what it communicates with. A Doppler effect simulation feature requested by Anue customers emulates the variations in distance with a continuous smooth slew of delay distance. One of the Doppler effects is receiver signal jitter. A receiver expects a pulse of data at very regular intervals. The receiver’s eye pattern determines which signals it finds acceptable. Should the edge of a signal change at a time inside the eye pattern the receiver may go out of syn- chronization and communication might be temporarily lost. As the transmitter receiver pair move relative to each other the regular intervals may not be regular enough. The Network Emulator forces the jitter to see how the receiver and in fact the application reacts. The impact on applications of long delays, jitter, Doppler effects, and other impairments, can be critical and must be tested before any satellite-based communi- cation system is launched. After launch may be too late, that is why an Network Emulator is essential to the satellite communications lab. ANUE Satellite services previously reserved for large businesses are becoming more available to smaller enterprises with more consumers using services including telecommunications and TV distribution. A direct-to-the-consumer architecture is used in direct broadcast systems, mobile communications satellite systems, and now even in broadband, high data rate multimedia satellite products and services. Applications such as collaborative computing, distributed CAD/CAM, scientific visualization, remote sensing data relay, messaging and navigational services, electronic publishing, and others, create demand for new satellite telecommunications networks. The effects of dynamic variation of data path length and related jitter must be considered and tested for with each new application to assure it will work before release to consumers.