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In a telephone system, the local loop is a two-wire connection between the subscriber’s house and the end office of the telephone company. It is commonly referred to as the “last mile” of the telephone network. The loop may run from 1km to as far as 10 km.CompositionTraditionally, local loops are composed of twisted pair copper cables. The old local loops have several limitations − narrow bandwidth, high attenuation, distortion of symbols, crosstalk's etc.In recent times, copper wires are being replaced by fiber optic cables for faster and more accurate performance. Installation of fiber cables is popularly known as FttH ... Read More
DefinitionPassive Optical Network (PON) is a FTTH (Fiber to the Home) technology deployed in both domestic and commercial consumers. It is called a passive network since it does not require a power equipment to amplify or process signals. A PON implements point – to – multipoint architecture, where a single optical line is divided into many optical splitters to serve multiple customers. It is used in the last mile of the network connection between an ISP and a user.ArchitectureThe passive optical network has three parts −Optical Line Terminator (OLT) − This is the end office of the service provider.Optical Distribution ... Read More
DefinitionDigital Subscriber Line (DSL) is a communication technology that offers high – bandwidth digital communication over standard telephone lines formed of copper wires.FeaturesDSL is a family of technologies under the general name of xDSL, for various x, like ADSL, HDSL, and RADSL. Originally, it was a part of the Integrated Services Digital Network (ISDN) and was called IDSL.DSL technology is used in the local loop of the telephone network, i.e. the part of the telephone network that connects the customer premises with the end office of the telephone company.Some DSL services provide more than the standard bandwidth of the telephone lines. ... Read More
The telephone system model is organized as a highly redundant, multilevel hierarchy. It comprises of the following components −Telephone of the subscriber or end userEnd office − Local central office directly connected to end user at a distance of 1 – 10km.Local loop − A two-way connection between the telephone and the end office.Toll office − switching centres which are called tandem offices when located within the same local area.Toll connecting trunk − Lines that connect end offices with toll offices.Intermediate switching offices − Interconnected non-hierarchical switching offices for connecting toll offices.Inter toll trunk − Very high bandwidth channels that ... Read More
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
In baseband transmission, the data bits are directly converted into signals. Generally a higher voltage level represents the bit 1, while a lower voltage level represents bit 0.The different encoding schemes are shown in the diagram. Among these, the first three are come in the category of polar encoding. In polar signaling, one logical state is represented by only one voltage state. In bipolar schemes, two voltage levels may be used to represent a logical state.NRZ (Non – Return to Zero)NRZ is an unipolar coding scheme. Here, a high voltage represents 1, while a low voltage represents 0. Non-return to ... Read More
Medium earth orbit (MEO) satellites lie between the two Van Allen Belts. MEOs are also called Intermediate Circular Orbits (ICOs).The altitudes of these satellites range from 2, 000 km to 35, 000 km, i.e. above the low earth orbits and below the geosynchronous orbits. The orbital periods of MEOs range from 2 hours to more than 23 hours, depending upon their attitudes.Types of MEOs according to orbitsMEOs with circular orbits − They revolve at constant speed at an constant altitude.MEOs with elliptical orbits − Lowest altitude is called perigee and the speed is highest here. Highest altitude is called apogee ... Read More
An array is a data structure/container/object that stores a fixed-size sequential collection of elements of the same type. The size/length of the array is determined at the time of creation.The position of the elements in the array is called as index or subscript. The first element of the array is stored at the index 0 and, the second element is at the index 1 and so on.Creating an arrayIn Java, arrays are treated as referenced types you can create an array using the new keyword similar to objects and populate it using the indices as −int myArray[] = new int[7]; ... Read More
Array is a container which can hold a fix number of items and these items should be of the same type. Most of the data structures make use of arrays to implement their algorithms. Following are the important terms to understand the concept of Array.Element − Each item stored in an array is called an element.Index: Each location of an element in an array has a numerical index, which is used to identify the element.The size of the array will be determined at the time of creation.Disadvantages of arraysDeleting or inserting − You cannot insert a new element at the ... Read More
To find continuous sub array whose sum is equal to a given number −Iterate through the array.At each element add the next n elements one by one, when the sum equals to the required value print the sub array.Exampleimport java.util.Arrays; import java.util.Scanner; public class sub_arrays { public static void main(String args[]){ //Reading the array from the user Scanner sc = new Scanner(System.in); System.out.println("Enter the size of the array that is to be created: "); int size = sc.nextInt(); int[] myArray = new int[size]; ... Read More