PROCESSOR EQUIPM FIGURE 102.7 Block diagram of a hub hub, VSAT, network management system, and associated transmission and processing subsystems. These sub systems along with sophisticated satellite access protocols and terrestrial protocol interfaces make interactive networks a flexible and powerful communication medium The hub performs all functions that are necessary to establish and maintain virtual connections between the location and VSATs. In private dedicated networks, the hub is co-located with the user's data processing In shared hub networks, the hub is connected to the user equipment via terrestrial backhaul circuits. the hub is a single point for failure in a star network, it is typically configured with 1: 1 or 1: Redundancy The hub consists of antenna, RE, and baseband equipment(Fig. 102.7). It will handle multiple channels of inbound and outbound data and often one or more channels of audio or video broadcast The hub antenna consists of a parabolic reflector and associated electrical and mechanical support eq he RF subsystem converts the modulated carrier to RF frequency, provides the necessary signal amplif and transmits the resulting RF carrier to the antenna subsystem. It also receives RF signals from the subsystem, provides low-noise amplification, RF/IF conversion, and passes the resulting IF carriers to the baseband equipment subsystem. The hub baseband equipment consists of the modem equipment and the rocessing equipment. The hub modems employ continuous modulators and burst demodulators. The pro cessing equipment interfaces to the modem equipment and provides the satellite access processing and protocol processing for interface to the customer host. VSAT The VSAT consists of an antenna, outdoor unit(ODU), interfacility link(IFL), and indoor unit(IDU ). The IFL connects the IDU and ODU subsystems, providing the transmit and receive lines, monitor and control signals, and dc power for the ODU electronics. A single-cable IFL, in which all signals are multiplexed on the same cable, is usually used to reduce the cost of IFL VSATs nominally use a 1. 2-or 1. 8-m offset feed parabolic antenna. Smaller antenna sizes are preferable to reduce the installation cost. Options for small antennas include the use of either a submeter parabolic reflector or a flat-plate antenna. The choice of antenna is a tradeoff mong performance, installation cost, and aesthetic considerations. The ODU consists of a solid-state power amplifier(SSPA), a low-noise amplifier, upconverter, and a down converter. VSAT SSPA modules are usually between 1.0 to 3.0 w. The OdU cost can be significantly lowered by utilization of a low-power SSPA (0. 1 to 0.5 W) consistent with obtaining the required output power. The VSAT receive side front end can be economically configured using an LNB Low-cost HEMT LNBs are currently available with 50-60 dB gain and noise figures lower than 1.3 dB e 2000 by CRC Press LLC© 2000 by CRC Press LLC hub, VSAT, network management system, and associated transmission and processing subsystems. These sub￾systems along with sophisticated satellite access protocols and terrestrial protocol interfaces make interactive networks a flexible and powerful communication medium. Hub The hub performs all functions that are necessary to establish and maintain virtual connections between the central location and VSATs. In private dedicated networks, the hub is co-located with the user’s data processing facility. In shared hub networks, the hub is connected to the user equipment via terrestrial backhaul circuits. Since the hub is a single point for failure in a star network, it is typically configured with 1:1 or 1:N redundancy. The hub consists of antenna, RF, and baseband equipment (Fig. 102.7). It will handle multiple channels of inbound and outbound data and often one or more channels of audio or video broadcast. The hub antenna consists of a parabolic reflector and associated electrical and mechanical support equipment. The RF subsystem converts the modulated carrier to RF frequency, provides the necessary signal amplification, and transmits the resulting RF carrier to the antenna subsystem. It also receives RF signals from the antenna subsystem, provides low-noise amplification, RF/IF conversion, and passes the resulting IF carriers to the baseband equipment subsystem. The hub baseband equipment consists of the modem equipment and the processing equipment. The hub modems employ continuous modulators and burst demodulators. The pro￾cessing equipment interfaces to the modem equipment and provides the satellite access processing and protocol processing for interface to the customer host. VSAT The VSAT consists of an antenna, outdoor unit (ODU), interfacility link (IFL), and indoor unit (IDU). The IFL connects the IDU and ODU subsystems, providing the transmit and receive lines, monitor and control signals, and dc power for the ODU electronics. A single-cable IFL, in which all signals are multiplexed on the same cable, is usually used to reduce the cost of IFL. VSATs nominally use a 1.2- or 1.8-m offset feed parabolic antenna. Smaller antenna sizes are preferable to reduce the installation cost. Options for small antennas include the use of either a submeter parabolic reflector or a flat-plate antenna. The choice of antenna is a tradeoff among performance, installation cost, and aesthetic considerations. The ODU consists of a solid-state power amplifier (SSPA), a low-noise amplifier, upconverter, and a down￾converter. VSAT SSPA modules are usually between 1.0 to 3.0 W. The ODU cost can be significantly lowered by utilization of a low-power SSPA (0.1 to 0.5 W) consistent with obtaining the required output power. The VSAT receive side front end can be economically configured using an LNB. Low-cost HEMT LNBs are currently available with 50–60 dB gain and noise figures lower than 1.3 dB. FIGURE 102.7 Block diagram of a hub