Cisco 3825 Hardware Installation Guide - Page 349

Chapter 33 Connecting Cisco IP VSAT Satellite WAN Network Modules Information About the NM-1VSAT-GILAT Network Module Satellite Hub Placed in orbit around the earth, a satellite is a specialized repeater that receives radio-frequency signals from earth stations and retransmits them to other earth stations. The satellite also amplifies the signals and switches the frequencies between the uplink and the downlink carriers. Gilat SkyEdge systems use geostationary satellites with a fixed satellite-to-earth delay of about 250 ms. The central hub-sometimes referred to as the "master earth station" but most often simply called the "hub"-contains many components, including: • Large dish antenna (15 to 36 feet [4.5 to 11 m] in diameter) • Satellite network management system (NMS) and provisioning stations, from which a network operator can monitor and control all components of the enterprise satellite communications network. • Baseband equipment that handles satellite access, routing between the hub and remote earth stations, dial backup, quality of service (QoS), TCP acceleration, and HTTP acceleration. • Optional components: web caches, MPEG transport coder/decoder, application server farms, and audio/video broadcast programming devices. Note Throughout this document, the "hub" refers specifically to a Gilat SkyEdge hub. VSATs A very small aperture terminal (VSAT) is an earth station that can be divided into two areas: • Indoor unit (IDU), which generally serves to connect the local network to the hub through the satellite link. The IDU components vary, depending on the functions required, but the components typically include these items: - Integrated receiver decoder (IRD) for the tuning - Demodulation and decoding of L-band or other type of intermediate frequency (IF) passed from the dish - End-user input/output • Outdoor unit (ODU), which includes a "very small" dish antenna (2 to 6 feet [0.5 to 2 m] in diameter) and its components, shown in Figure 33-3. The ODU is typically mounted on a building roof or outer wall, or placed on the ground. The NM-1VSAT-GILAT network module functions as the IDU of a VSAT and is connected to the ODU through coaxial cables. A power supply is connected to the NM-1VSAT-GILAT network module to provide power over the coaxial cables to the ODU. Note The NM-1VSAT-GILAT network module supports only the ODU equipment and power supply that comes in the "Sat Kit" provided by a Gilat SkyEdge satellite service provider. OL-2485-20 Cisco Network Modules Hardware Installation Guide 33-5