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Asymptotic NotationsAsymptotic notations are used to represent the complexities of algorithms for asymptotic analysis. These notations are mathematical tools to represent the complexities. There are three notations that are commonly used.Big Oh NotationBig-Oh (O) notation gives an upper bound for a function f(n) to within a constant factor.We write f(n) = O(g(n)), If there are positive constants n0 and c such that, to the right of n0 the f(n) always lies on or below c*g(n).O(g(n)) = { f(n) : There exist positive constant c and n0 such that 0 ≤ f(n) ≤ c g(n), for all n ≤ n0}Read More
Asymptotic NotationsAsymptotic notations are used to represent the complexities of algorithms for asymptotic analysis. These notations are mathematical tools to represent the complexities. There are three notations that are commonly used.Big Oh NotationBig-Oh (O) notation gives an upper bound for a function f(n) to within a constant factor.Little o NotationsThere are some other notations present except the Big-Oh, Big-Omega and Big-Theta notations. The little o notation is one of them.Little o notation is used to describe an upper bound that cannot be tight. In other words, loose upper bound of f(n).Big Omega NotationBig-Omega (Ω) notation gives a lower bound for ... Read More
Advanced mobile phone system (AMPS) was a standard for analog cellular phone system developed by Bell Labs and officially introduced by AT&T in 1983.FeaturesIt is an analog system based on the initial electromagnetic spectrum allocation for cellular service by the Federal Communications Commission.It uses frequency division multiple access (FDMA) for multiple simultaneous conversations.Frequency ranges within the 800 and 900 MHz are allocated for cellular telephones in AMPS. Half of the signal is used for sending signals and half is used for receiving signals.It has a high bandwidth requirement particularly when the number of conversations is very high.It was the first ... Read More
Cellular architecture is constituted of the following −A network of cells each with a base station.A packet switched network for communication between the base stations and mobile switching centers.The public switched telephone network to connect subscribers to the wider telephony networkCellular ConfigurationIn all cellular systems, land area is divided into a number of cells each with its radio service. In AMPS the area is large which in digital services, the area is much smaller.Conventionally cells are hexagonal in shape.Each cell uses a frequency range that is not used by its adjacent cells. However frequencies may be reused in non-adjacent cells.At ... Read More
Mobile telephone service (MTS) connects mobile radio telephones with other networks like public switched telephone networks (PSTN), other mobile telephones and communication systems like Internet.Basic Mobile Communications SystemMobile phones and other mobile devices, called mobile stations are connected to base stations. Communication between the mobile stations and the base stations are done by wireless radio signals, which may be both data signals and voice signals. Each base station has a coverage area around it, such that mobile stations within this area can connect provided they have access permissions. Base stations contain transmitters and receivers to convert radio signals to electrical ... Read More
Message switching is a connectionless network switching technique where the entire message is routed from the source node to the destination node, one hop at a time. It was a precursor of packet switching.ProcessPacket switching treats each message as an individual unit. Before sending the message, the sender node adds the destination address to the message. It is then delivered entirely to the next intermediate switching node. The intermediate node stores the message in its entirety, checks for transmission errors, inspects the destination address and then delivers it to the next node. The process continues till the message reaches the ... Read More
Circuit switching is a connection-oriented network switching technique. Here, a dedicated route is established between the source and the destination and the entire message is transferred through it.Phases of Circuit Switch ConnectionCircuit Establishment : In this phase, a dedicated circuit is established from the source to the destination through a number of intermediate switching centres. The sender and receiver transmits communication signals to request and acknowledge establishment of circuits.Data Transfer : Once the circuit has been established, data and voice are transferred from the source to the destination. The dedicated connection remains as long as the end parties communicate.Circuit Disconnection ... Read More
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