A cellular network or mobile network is a wireless network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell. Cellular Network Devices Cellular Identifiers In Advanced Mobile Phone System (AMPS), a cell phone subscription is identified using three numbers: Electronic Serial Number (ESN): unique 32 bit number programmed into the cell when it was manufactured. Mobile Identification Number (MIN): 10 digit phone ...
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Infrastructure mode & ad-hoc mode All data is transferred using the access point as the central hub. All wireless nodes in an infrastructure mode network connect to an access point. All nodes connecting to the access point must have the same service set identifier (SSID) as the access point, and if the access point is enabled with Wired Equivalent Privacy (WEP) they must have the same WEP key or other authentication parameters. Ad-hoc mode network It is a decentralized type of wireless network.The network is ad hoc because it does not rely on a pre existing infrastructure, such as routers ...
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Bluetooth is a standard developed by a group of electronics manufacturers that will allow any sort of electronic equipment — from computers and cell phones to keyboards and headphones — to make its own connections, without wires, cables or any direct action from a user. A key difference with other existing wireless technologies is that bluetooth enables combined usability models based on functions provided by different devices. The Bluetooth Special Interest Group comprises more than 1000 companies.The major companies who created the technology include Intel 3 com Ericcson IBM Motorola Nokia Toshiba The Name – Bluetooth? The name is attributed ...
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ETHERNET It defines a number of wiring for the physical layer, through means of Network access at the Media Access Control (MAC)/Data Link Layer, and a Common addressing format. The combination of the twisted pair versions of Ethernet with the fiber optic versions largely replacing standards such as coaxial cable Ethernet. In recent years, Wi-Fi, the wireless LAN standardized by IEEE 802.11, has been used instead of Ethernet for many home and small office networks and in addition to Ethernet in larger installations. The Institute of Electrical and Electronics Engineers Standards Association (IEEE- SA) is an organization within IEEE that ...
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Introduction The multiplexing is used to combined a number of independent signals into a composite signal suitable for transmission over a common channel . It is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource. For example, in telecommunications, several telephone calls may be carried using one wire. A device that performs the multiplexing is called a multiplexer (MUX), and a device that performs the reverse process is called a demultiplexer (DEMUX or DMX). Types of Multiplexing Frequency-Division Multiple Access ...
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DATA COMMUNICATION Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Characteristics Must be a Sender and Receiver A protocol is a set of rules which governs the transfer of data between computers. Protocols allow communication between computers and networks. Handshaking is used to establish which protocols to use. Handshaking controls the flow of data between computers Protocols will determine the speed of transmission, error checking method, size of bytes, and whether synchronous or asynchronous Examples of protocols are: token ring, CSMA/CD, X.25, TCP/IP Every communication system has ...
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BLOCK CODING Unlike line codes which operate on a stream of information bits, block codes operate on block of information bits. Redundant bit(s) are added to each block of information bits to ensure synchronization and error detection
What is operating system? Computer = set of resources –Processor(s), memory, I/O & communication devices OS –Enables use of resources –Manages resources –The low-level software that supports a computer’s basic functions, such as scheduling tasks and controlling peripherals Resources not limited to hardware Shift from –Pure efficient use of resources to –Enhance user experience Operating System Model As you can see in the above diagram the application runs on top of the OS. Only the OS has full access to the underlying hardware. What is the kernel? A kernel is a central component of an operating system. It acts as ...
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Finite number of resources to be distributed among a number of competing processes A set of blocked processes each holding a resource and waiting to acquire a resource held by another process in the set. The Deadlock Problem Example –System has 2 tape drives. –P1 and P2 each hold one tape drive and each needs another one. Example –semaphores A and B, initialized to 1 P0 P1 wait (A); wait(B) wait (B); wait(A) Bridge Crossing Example Traffic only in one direction. Each section of a bridge can be viewed as ...
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A thread is the smallest unit of processing that can be performed in an OS. In most modern operating systems, a thread exists within a process – that is, a single process may contain multiple threads A thread has its own: Program counter System registers Stack A thread shares following information with peer threads: Code segment Data segment Open files A basic unit of CPU utilization. It consists of a thread ID, a program counter, a register set, and a stack. It is a single sequential flow of control within a program If a process has multiple threads of control, ...
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