Hamming DistanceHamming distance is a metric for comparing two binary data strings. While comparing two binary strings of equal length, Hamming distance is the number of bit positions in which the two bits are different.The Hamming distance between two strings, a and b is denoted as d(a, b).It is used for error detection or error correction when data is transmitted over computer networks. It is also using in coding theory for comparing equal length data words.Calculation of Hamming DistanceIn order to calculate the Hamming distance between two strings, and , we perform their XOR operation, (a⊕ b), and then count ... Read More

Error Correcting CodesError-correcting codes (ECC) are a sequence of numbers generated by specific algorithms for detecting and removing errors in data that has been transmitted over noisy channels. Error correcting codes ascertain the exact number of bits that has been corrupted and the location of the corrupted bits, within the limitations in algorithm.ECCs can be broadly categorized into two types, block codes and convolution codes. Low - density parity check code (LDPC) is a linear error correcting block code. They are suitable for large block sizes in very noisy channels.LDPC codes were developed by Robert G. Gallager, in his doctoral ... Read More

Errors and Error Correcting CodesErrors in data occur when bits get corrupted in the data. When bits are transmitted over the computer network, they are subject to get corrupted due to interference and network problems, leading to errors.Error-correcting codes (ECC) are a sequence of numbers generated by specific algorithms for detecting and removing errors in data that has been transmitted over noisy channels. Error correcting codes ascertain the exact number of bits that has been corrupted as well as the location of the corrupted bits, within the limitations in algorithm.ECCs can be broadly categorized into two types, block codes and ... Read More

Errors and Error Correcting CodesErrors occurs when bits get corrupted while transmission over the computer network, due to interference and network problems.Error-correcting codes (ECC) are a sequence of numbers generated by specific algorithms for detecting and removing errors in data that has been transmitted over noisy channels. Error correcting codes ascertain the exact number of bits that has been corrupted and the location of the corrupted bits, within the limitations in algorithm.ECCs can be broadly categorized into two types, block codes and convolution codes.Binary Convolutional CodesIn convolutional codes, the message comprises of data streams of arbitrary length and a sequence ... Read More

Errors and Error Correcting CodesWhen bits are transmitted over the computer network, they are subject to get corrupted due to interference and network problems. The corrupted bits leads to spurious data being received by the receiver and are called errors.Error-correcting codes (ECC) are a sequence of numbers generated by specific algorithms for detecting and removing errors in data that has been transmitted over noisy channels. Error correcting codes ascertain the exact number of bits that has been corrupted and the location of the corrupted bits, within the limitations in algorithm.ECCs can be broadly categorized into two types −Block codes − ... Read More

Forward error correction (FEC) is an error correction technique to detect and correct a limited number of errors in transmitted data without the need for retransmission.In this method, the sender sends a redundant error-correcting code along with the data frame. The receiver performs necessary checks based upon the additional redundant bits. If it finds that the data is free from errors, it executes error-correcting code that generates the actual frame. It then removes the redundant bits before passing the message to the upper layers.Advantages and DisadvantagesBecause FEC does not require handshaking between the source and the destination, it can be ... Read More

Data-link layer uses error control techniques to ensure that frames, i.e. bit streams of data, are transmitted from the source to the destination with a certain extent of accuracy.ErrorsWhen bits are transmitted over the computer network, they are subject to get corrupted due to interference and network problems. The corrupted bits leads to spurious data being received by the destination and are called errors.Types of ErrorsErrors can be of three types, namely single bit errors, multiple bit errors, and burst errors.Single bit error − In the received frame, only one bit has been corrupted, i.e. either changed from 0 to ... Read More

Flow control is a technique that allows two stations working at different speeds to communicate with each other. It is a set of measures taken to regulate the amount of data that a sender sends so that a fast sender does not overwhelm a slow receiver.In data link layer, the sender continues to send frames only after it has received acknowledgments from the user for the previous frames. This is called feedback based flow control. Here, a restriction is imposed on the number of frames the sender can send before it waits for an acknowledgment from the receiver.Feedback based Flow ... Read More

High-level Data Link Control (HDLC) is a group of communication protocols of the data link layer for transmitting data between network points or nodes. Since it is a data link protocol, data is organized into frames. A frame is transmitted via the network to the destination that verifies its successful arrival. It is a bit - oriented protocol that is applicable for both point - to - point and multipoint communications.Transfer ModesHDLC supports two types of transfer modes, normal response mode and asynchronous balanced mode.Normal Response Mode (NRM) − Here, two types of stations are there, a primary station that ... Read More

Framing is a Data Link layer function whereby the packets from the Network Layer are encapsulated into frames. The data frames can be of fixed length or variable length. In variable - length framing, the size of each frame to be transmitted may be different. So, a pattern of bits is used as a delimiter to mark the end of one frame and the beginning of the next frame.The two types of variable - sized framing are −Character-oriented framingBit - oriented framingCharacter - Oriented FramingIn character - oriented framing, data is transmitted as a sequence of bytes, from an 8-bit ... Read More