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Computer Engineering Articles
Page 6 of 36
Transmission of Light Through Fiber
In fiber optic communication, signals are transmitted through an optical fiber using the fundamental properties of light, specifically refraction and total internal reflection. Understanding these optical principles is essential for grasping how data travels through fiber optic cables over long distances with minimal loss. Refraction When a light ray travels from one transmission medium to another with different optical density, its direction changes at the interface between the two media. This phenomenon is called refraction of light. The optical density of a medium is measured by its refractive index. A higher refractive index indicates a denser medium. ...
Read MoreBaseband Transmission
Baseband transmission is a digital signaling method where data bits are directly converted into electrical signals without modulation. In this transmission technique, the entire bandwidth of the communication channel is used to transmit a single digital signal. In baseband systems, typically a higher voltage level represents bit 1, while a lower voltage level represents bit 0. The choice of encoding scheme affects factors like synchronization, error detection capability, and bandwidth efficiency. Types of Baseband Encoding Baseband encoding schemes can be categorized into three main types: unipolar, polar, and bipolar encoding. Each category uses different voltage levels and ...
Read MoreStructure of the Telephone System
The telephone system is organized as a highly redundant, multilevel hierarchy designed to provide reliable voice communication across vast distances. This hierarchical structure ensures efficient call routing and redundancy for uninterrupted service. Components of the Telephone System Subscriber telephone − The end user device that initiates or receives calls End office − Local central office directly connected to end users within a 1-10 km radius Local loop − A two-way connection between the subscriber's telephone and the end office Toll office − Switching centers that handle long-distance calls; called tandem ...
Read MoreConnection-Oriented Services
A connection-oriented service is one that establishes a dedicated connection between the communicating entities before data communication commences. It is modeled after the telephone system. To use a connection-oriented service, the user first establishes a connection, uses it, and then releases it. In connection-oriented services, the data streams/packets are delivered to the receiver in the same order in which they have been sent by the sender. Connection-Oriented Service Flow Sender Receiver 1. Connection Request 2. ...
Read MoreCellular Architecture
Cellular architecture is the foundation of mobile communication systems that enables wireless connectivity across large geographical areas. It divides service areas into smaller regions called cells, each served by a base station to provide efficient frequency reuse and seamless communication. The cellular architecture is constituted of the following components: A network of cells − Each cell contains a base station that provides radio coverage for mobile devices in that area. A packet switched network − Facilitates communication between base stations and mobile switching centers. The public switched telephone network (PSTN) − Connects ...
Read MoreConnectionless Services
A Connectionless service is a data communication method between two nodes where the sender transmits data without establishing a dedicated connection or ensuring the receiver's availability. In this model, each data packet contains complete destination addressing information and is routed independently of other packets through the network. Unlike connection-oriented services, connectionless communication requires no initial handshake or connection setup. Data packets, called datagrams, may take different paths to reach their destination, with the network making routing decisions independently for each packet. Connectionless Service - Independent Packet Routing Sender ...
Read MoreCharacter - Oriented Framing and Bit - Oriented Framing
Framing is a Data Link layer function that encapsulates packets from the Network Layer into frames. Data frames can be of fixed or variable length. In variable-length framing, frame sizes may differ, so a pattern of bits serves as a delimiter to mark frame boundaries. The two types of variable-sized framing are: Character-oriented framing Bit-oriented framing Character-Oriented Framing In character-oriented framing, data is transmitted as a sequence of bytes using an 8-bit coding system like ASCII. This approach treats data as a stream of characters rather than individual bits. ...
Read MoreConstraint length of the Convolutional Code
Convolutional codes are error correcting codes where data streams of indefinite lengths are encoded before transmission over noisy channels. The message streams are encoded by the sliding application of Boolean functions that generate a sequence of output bits. Convolutional codes were first introduced in 1955 by Elias. After extensive research by mathematicians, Viterbi developed an algorithm for maximum likelihood decoding in 1973, called the Viterbi algorithm, which led to modern convolutional codes. Parameters in Convolutional Codes For generating a convolutional code, information is passed sequentially through a linear finite-state shift register. The shift register comprises of K-bit ...
Read MoreHard and Soft Decision Decoding
A challenging task in error correction is decoding the codewords that have been received via noisy channels. Before data is transmitted, the sender adds redundant bits or parity bits to the message forming codewords. The codewords are then transmitted via computer networks. The receiver checks the incoming codewords and performs the decoding or error correction process to retrieve the original data. If there are no errors, i.e. the codewords find an exact matching, then it is easy to decode the data by eliminating the parity bits. However, if a match is not found, then more complex decoding mechanisms are ...
Read MoreLink Control Protocol (LCP)
Link Control Protocol (LCP) is a crucial component of the Point-to-Point Protocol (PPP) that operates at the data link layer. It is responsible for establishing, configuring, testing, maintaining, and terminating point-to-point links for data transmission. LCP also handles negotiation of setup options and features between the two endpoints of a communication link. How It Works When PPP initiates communication, it sends LCP packets before establishing connections over the point-to-point link. These LCP packets test the communication line to determine if it can handle the required data volume at the specified speed. Based on this assessment, LCP negotiates the ...
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