broadband strategies handbook.pdf - Khazar University

From a geosynchronous vantage point, satellites can transmit signalscovering as much as one-third of Earth’s surface. This stable “footprint”coverage makes satellites an ideal medium for distributing television(TV) and Internet content on both a single point-to-point basis and apoint-to-multipoint basis. Today’s advanced satellites also make use of“spot beams” (principally in the Ka band) that allow higher power to beconcentrated in specific regions to improve bandwidth and signal quality.These beams can also be steered or reconfigured to match bandwidthto specific areas of demand.A satellite network can be configured in various ways, ranging from asimple one-direction link to a more complex mesh network. Communicationswith the satellite take place via an earth station or individualantenna. The size of the antenna depends partially on the frequency beingused and also affects the volume of information that can be exchangedwith the satellite. Large antennas are typically installed at earth stationsfor high-bandwidth applications, while smaller antennas, such as verysmall aperture terminals (VSAT) or direct to home (DTH) dishes are usedfor applications such as lower-bandwidth Internet access in rural areas orsatellite TV reception. An estimated 3 million commercial VSATs areused for commercial and consumer purposes around the world, with themajority supporting broadband Internet or high-data-rate services. 6Each communication satellite requires several hundred million dollarsin investment to cover its construction, insurance, launch, and tracking.These satellites have a limited usable life (usually around 20 years)because operators cannot make repairs or add fuel to the propulsionmotors to keep them in proper orbit and pointed at the correct angletoward Earth. Additionally, satellites have comparatively less transmissioncapacity than terrestrial options, such as fiber optic cables. The largedistance between the satellite and users on Earth also results in delays,known as latency, due to the time it takes for instructions to reach a satelliteand content to arrive on Earth. Despite these limitations, satellitesexcel in their ability to distribute broadband content, such as television, tomany locations and are advantageous for different developing-countrycharacteristics such as archipelagos or difficult terrain as well as for emergencyand disaster situations.Microwave“Microwave” systems are named for the wavelengths they use to communicateand are generally implemented using frequencies between6 GHz and 38 GHz (Hansryd and Eriksson 2009). Microwave systemsTechnologies to Support Deployment of Broadband Infrastructure 203