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Case Study: Satellite Simulator Satellite communications have long been subject to noticeable signal delays. The lag in satellite TV broadcasts and phone calls are examples that many of us have experienced first hand. Travelling at the speed of light, it takes over 200 ms to reach geosynchronous orbit (GEO) and back. Even using satellites at low earth orbit (LEO) of 200 to 400 km, transmission times between two terrestrial locations can be significant. Next generation satellite communications technologies are now being developed using much higher bandwidth then ever before. Defence applications, in particular, will use gigabit, and even ten gigabit, data rates. In some cases, “free space optics” is being researched as a way to transmit high bandwidth signals between satellites in space. As a result of higher data rates, emulating and testing satellite communications using fiber optic cables in a traditional lab environment is increasingly common. Anue Emulators, with their precise, controllable and enormous delay capabilities fit this satellite simulation requirement perfectly. In Fall 2004, Anue Systems received an order from a large DoD contractor for three ten Gigabit Signal Delay Emulators. Anue's ten gigabit product platform, called the “H” Series, delays and impairs SONET/SDH OC192/STM64, Ten Gigabit Ethernet (LAN Phy and WAN Phy), and 10 Gigabit Fibre Channel traffic. SONET G.709 and GigE FEC data rates are also included. This customer began testing in early 2005 a simulation of an “Internet in the Sky” defence shield. Initially, with a setup of three routers (either Cisco 15454 or Juniper M320) as geo-stationary “satellites” and the Anue Emulator as the OC192 “links” between the three satellites, the effects of latency on high bandwidth communications between orbiting satellites is being tested. Since the three satellites will be moving in relation to one another, the ability to dynamically vary delay times is essential. This requirement led to the development of Anue's “Doppler Shift” functionality, which is available on all Anue “H” Series Systems as an option. Using Doppler Shift, a user can automatically increase and/or decrease the delay time injected by the Anue Simulator in increments as small as one part per million (ppm). After the initial test setup is verified, this contractor plans to add LEO satellites to its test bed and, after that, simulated ground based communication stations. The total number of links will grow to the thousands, and data rates, protocols and requirements between the different nodes will vary. The result of these multi-year tests will be a thoroughly validated communications system that can then be incorporated into actual satellite and ground station equipment. Downloads |
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