Found 1625 Articles for Computer Network

Fiber optic communications and satellite communications are complementary to each other. Their properties are very different from one another and consequently their usage varies.Comparison between satellite communication and optical fiber communication can be done based upon the following areas −TerrainSatellite communication is best suited for rough terrains, poorly connected areas and places where it is difficult to lay wires.On the other hand, fibers are suited for urban areas with good infrastructures, where it is convenient to lay communication lines.BandwidthFiber optic promises extremely higher bandwidth with negligible electromagnetic interference. Satellites have lesser bandwidth and are prone to interferences.Data Rate and DelayThe ... Read More

Low earth orbit (LEO) satellites systems orbit below 2000 km from the earth’s surface, i.e. below the lower Van Allen belt. They move at very high speeds and may not have any fixed space with respect to the earth.The following diagram depicts LEO satellites in their orbits.Features of LEO SatellitesA network of LEO satellites are needed for global coverage as their orbits are not geostationary.These satellites are not as powerful as the MEO and GEO satellites.Due to their high speeds, satellites move in and out of the earth station’s range from time to time. So, data is handed off from ... Read More

VSATs (Very Small Aperture Terminals) is a two way, lost cost, ground micro station for transmitting data to and from communication satellites. A VSAT has a dish antenna with diameters between 75 cm to 1 m, which is very small in comparison with 10 m diameter of a standard GEO antenna. It accesses satellites in geosynchronous orbits or geostationary orbits. Data rates in VSATs ranges from 4 Kbps to 16 Mbps.Configurations of VSATsStar Topology − This has a central uplink site which transmits data from and to each VSAT through the satellite.Mesh Topology − Each VSAT transmits data via the ... Read More

Geosynchronous Satellite and Geosynchronous Orbit (GSO)A geosynchronous satellite is a communication satellite that has an orbital period same as the period of rotation of the earth. Hence, it appears to be permanently in the same area of the sky at a particular time each day when viewed by an observer on the earth.The orbit in which a geosynchronous satellite is placed is called geosynchronous orbit (GSO). Its orbital period is the sidereal day, i.e. 23 hours 56 minutes 4 seconds and its orbital altitude is 35, 800 km.Geostationary Satellite and Geostationary Orbit (GEO)A circular geosynchronous satellite which is placed at ... Read More

Fiber optic cables are finding increasing usage due to a number of advantages over the traditional copper wires. However, there are a few flipsides in its usage too.Advantages of Fiber Optics Cables over Copper WiresFiber optic cables transmit data at much higher speed than copper wires. This is because the speed of light is greater than the speed of electrons.Fiber optic cables have a much larger bandwidth of over 60 Tbps in comparison to 10 Gbps bandwidth of copper wires.Fiber optic cables have very low attenuation. Repeaters need to be added only after every 50 km as compared to 5 ... Read More

Optical fiber cables are transparent, flexible fibers made up of glass or plastic through which light waves can pass. A bunch of fiber optic cables is shown in the following diagram −Structure of a Fiber – Optic CableA cross section of a fiber optic cable reveals three parts −Core −  It is the innermost portion of an optical fiber through which light propagates. It is cylindrical in shape and it made up of a flexible glass of high refractive index. The diameter of the core of a single mode fiber is 8 – 10 μm while multimode fibers are 50 ... Read More

In fiber optic communication, signals are transmitted through an optical fiber. This is based upon certain characteristics of light, namely refraction and total internal reflection.RefractionWhen a light ray goes from a denser transmission medium to a rarer one or vice versa, then its direction changes at the interface of the two medium. This phenomenon is called refraction of light.The density of an optical medium is measured in refractive index. Higher the refractive index, denser it is.The angle between the incident ray and the normal is called angle of incidence Θi, while the angle between the refracted ray and the normal ... Read More

In fiber optic communication, data is transmitted from the source to the destination by sending light pulses through optical fibers. It changes electrical pulses to light signals and vice versa for communication. Fiber optic communications are preferred when a huge amount of data needs to be transmitted across large distances.The process of communication using fiber optics has the following steps −Conversion of input electrical data to light signals : The data to be sent by the sender is in the form of electrical signals. These signals are converted to light pulses by the transmitter circuitry using a light source. A ... Read More

Coaxial cables, commonly called coax, are copper cables with metal shielding designed to provide immunity against noise and greater bandwidth. Coax can transmit signals over larger distances at a higher speed as compared to twisted pair cables.Structure of Coaxial CablesCoax has a central core of stiff copper conductor for transmitting signals.  This is covered by an insulating material. The insulator is encased by a closely woven braided metal outer conductor that acts as a shield against noise. The outer conductor is again enclosed by a plastic insulating cover. The structure is shown in the following figure −Categories of Coaxial CablesCoaxial ... Read More

The primary purpose of computer networks is to transfer data from a source machine to a destination machine. One of the elementary ways to transfer data between machines is to use removable storage media. The steps for the transfer are −Copy data from the source computer to the removable storage device.Physically transport the removable device to the source computer.Copy data from the removable device to the destination computer.Some of the removable media that can use for transferring data between devices are −Magnetic tapesOptical discs like CDs, DVDs, and Blu-ray DiscsUSB flash drivesZip discs and floppy discsMemory cards and Memory sticksAdvantages ... Read More