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Computer Engineering Articles
Page 32 of 36
What is Polynomial Code?
A polynomial code is a linear code having a set of valid code words that comprises of polynomials divisible by a shorter fixed polynomial is known as generator polynomial.They are used for error detection and correction during the transmission of data as well as storage of data.Types of Polynomial CodesThe types of polynomial codes are:Cyclic Redundancy CodeBose–Chaudhuri–Hocquenghem (BCH) CodesReed–Solomon CodesRepresentation of Bit Strings with PolynomialsThe code words, which are essentially bit strings, are represented by polynomials whose coefficients are either 0 or 1. A 𝑘 – bit word is represented by a polynomial ranging from 𝑥0 to 𝑥𝑘−1. The order ...
Read MoreA Utopian Simplex Protocol
The Simplex protocol is data link layer protocol for transmission of frames over computer network. It is hypothetical protocol designed for unidirectional data transmission over an ideal channel, i.e. a channel through which transmission can never go wrong.It is assumed that both the sender and the receiver are always ready for data processing and both of them have infinite buffer. The sender simply sends all its data available onto the channel as soon as they are available its buffer. The receiver is assumed to process all incoming data instantly. It is does not handle flow control or error control. Since ...
Read MoreWhat is algorithm for computing the CRC?
Cyclic Redundancy Check (CRC)Cyclic Redundancy Check (CRC) is a block code that was invented by W. Wesley Peterson in 1961. It is commonly used to detect accidental changes to data transmitted via telecommunications networks and storage devices.CRC involves binary division of the data bits being sent by a predetermined divisor agreed upon by the communicating system. The divisor is generated using polynomials. So, CRC is also called polynomial code checksum.Before sending the message over network channels, the sender encodes the message using CRC. The receiver decodes the incoming message to detect error. If the message is error-free, then it is ...
Read MorePositive Acknowledgement with Retransmission (PAR)
Positive Acknowledgement with Retransmission (PAR) is a group of error – control protocols for transmission of data over noisy or unreliable communication network. These protocols reside in the Data Link Layer and in the Transport Layer of the OSI (Open Systems Interconnection) reference model. They provide for automatic retransmission of frames that are corrupted or lost during transit. PAR is also called Automatic Repeat ReQuest (ARQ).PARs are used to provide reliable transmissions over unreliable upper layer services. They are often used in Global System for Mobile (GSM) communication.Working PrincipleIn these protocols, the receiver sends an acknowledgement message back to the ...
Read MoreThe Data Link Layer Frame and Frame Fields
Data Link Layer FrameA frame is a unit of communication in the data link layer. Data link layer takes the packets from the Network Layer and encapsulates them into frames. If the frame size becomes too large, then the packet may be divided into small sized frames. At receiver’ end, data link layer picks up signals from hardware and assembles them into frames.Fields of a Data Link Layer FrameA data link layer frame has the following parts:Frame Header: It contains the source and the destination addresses of the frame and the control bytes.Payload field: It contains the message to be ...
Read MoreA Simplex Stop-and-Wait Protocol for an Error-Free Channel
Stop – and – Wait protocol is data link layer protocol for transmission of frames over noiseless channels. It provides unidirectional data transmission with flow control facilities but without error control facilities.This protocol takes into account the fact that the receiver has a finite processing speed. If data frames arrive at the receiver’s end at a rate which is greater than its rate of processing, frames be dropped out. In order to avoid this, the receiver sends an acknowledgement for each frame upon its arrival. The sender sends the next frame only when it has received a positive acknowledgement from ...
Read MoreBandwidth Delay Product
Bandwidth delay product is a measurement of how many bits can fill up a network link. It gives the maximum amount of data that can be transmitted by the sender at a given time before waiting for acknowledgment. Thus it is the maximum amount of unacknowledged data.MeasurementBandwidth delay product is calculated as the product of the link capacity of the channel and the round – trip delay time of transmission.The link capacity of a channel is the number of bits transmitted per second. Hence, its unit is bps, i.e. bits per second.The round – trip delay time is the sum ...
Read MoreWhat is pipelining?
In computer networking, pipelining is the method of sending multiple data units without waiting for an acknowledgment for the first frame sent. Pipelining ensures better utilization of network resources and also increases the speed of delivery, particularly in situations where a large number of data units make up a message to be sent.Flow Diagram of Pipelined Data TransmissionThe following flow diagram depicts data transmission in a pipelined system versus that in a non-pipelined system. Here, pipelining is incorporated in the data link layer, and four data link layer frames are sequentially transmitted.Data Link Protocols that uses PipeliningTwo data link layer ...
Read MoreGo-Back-N ARQ
Go-Back-N Automatic Repeat reQuest (Go-Back-N ARQ), is a data link layer protocol that uses a sliding window method for reliable and sequential delivery of data frames. It is a case of sliding window protocol having to send window size of N and receiving window size of 1.Working PrincipleGo – Back – N ARQ uses the concept of protocol pipelining, i.e. sending multiple frames before receiving the acknowledgment for the first frame. The frames are sequentially numbered and a finite number of frames. The maximum number of frames that can be sent depends upon the size of the sending window. If ...
Read MoreStorage Device Hierarchy
Computer storage has components that store computer data. The different storage types in the storage hierarchy are as follows: Primary Storage This is also known as the main memory and is the memory directly accessible by the CPU. All the instructions are executed in the main memory by CPU and the data required by these instructions is also stored in main memory. Main memory primarily consists of the RAM which is volatile in nature. It is also quite small compared to secondary memory and expensive as well. Secondary Storage Secondary or external storage is not directly accessible by the ...
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