(LNB) – This is the receiving element of the terminal. The LNB's job is to amplify the received satellite radio signal bouncing off the dish and filter out the noise, which is any signal not carrying valid information. The LNB passes the amplified, filtered signal to the satellite modem at the user's location. Indoor unit (IDU) The satellite modem serves as an interface between the outdoor unit and customer-provided equipment (i.e. PC, router) and controls satellite transmission and reception. From the sending device (computer, router, etc.) it receives an input bitstream and converts or modulates it into radio waves, reversing that order for incoming transmissions, which is called demodulation. It provides two types of connectivity: Coaxial cable (COAX) connectivity to the satellite antenna. The cable carrying electromagnetic satellite signals between the modem and the antenna generally is limited to be no more than 150 feet in length. Ethernet connectivity to the computer, carrying the customer's data packets to and from the Internet content servers. Consumer grade satellite modems typically employ either the DOCSIS or WiMAX telecommunication standard to communicate with the assigned gateway. Challenges and limitations Signal latency Latency (commonly referred to as "ping time") is the delay between requesting data and the receipt of a response, or in the case of one-way communication, between the actual moment of a signal's broadcast and the time it is received at its destination. A radio signal takes about 120 milliseconds to reach a geostationary satellite and then 120 milliseconds to reach the ground station, so nearly 1/4 of a second overall. Typically, during perfect conditions, the physics involved in satellite communications account for approximately 550 milliseconds of latency round-trip time. The longer latency is the primary difference between a standard terrestrial-based network and a geostationary satellite-based network. The round-trip latency of a geostationary satellite communications network can be more than 12 times that of a terrestrial based network. Satellite latency can be detrimental to especially time-sensitive applications such as on-line gaming (although it only seriously affects the likes of first-person shooters while many MMOGs can operate well over satellite Internet), but IPTV is typically a simplex operation (one-way transmission) and latency is not a critical factor for video transmission. The effects of this delay may be mitigated using data compression, TCP-acceleration, and HTTP pre-fetching. Geostationary orbits A geostationary orbit (or geostationary Earth orbit/GEO) is a geosynchronous orbit directly above the Earth's equator