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06 Handou 1
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- 1Kinds of Noise in Data TransmissionsWhite noise (Thermal noise or Gaussian noise)
Impulse noise (Noise spike
Crosstalk
Echo
Jitter
Attenuation - 2It is always present to some degree in transmission media and electronic devices and is dependent on the temperature of the medium. In this noise, when the temperature increases, the level of noise increases because of the increased activity of the electrons in the electronic device.White noise (Thermal noise or Gaussian noise)
- 3It is a noncontinuous noise and one of the most difficult errors to detect because it can occur randomly. Typically, the noise is an analog burst of energy. If this interferes with an analog signal, removing it without affecting the original signal can be difficult.Impulse noise (Noise spike)
- 4It is an unwanted coupling between two (2) different signal paths. This unwanted coupling can be electrical, as might occur between two (2) sets of twisted pair wire (as in a phone line), or it can be electromagnetic (as when unwanted signals are picked up by microwave antennas).Crosstalk
- 5It is the reflective feedback of a transmitted signal as the signal moves through a medium. It is usually a signal bouncing back from the end of a cable and creating this.Echo
- 6It is the result of small timing irregularities that become magnified during the transmission of digital signals as the signals are passed from one device to another. To put it another way, when a digital signal is being transmitted, the rises and falls of the signal can start to shift or become blurry and, thus, produce this.Jitter
- 7It is the continuous loss of a signal's strength as it travels through a medium. It is not necessarily a form of error but can indirectly lead to an increase in errors affecting the transmitted signal.Attenuation
- 8Types of Errorssingle-bit error
burst error - 9it indicates that only one (1) bit of a given data unit (such as a byte, character, or packet) is changed from 1 to 0 or from 0 to 1.single-bit error
- 10it indicates that two (2) or more bits in the data unit have changed from 1 to 0 or from 0 to 1. This error is more likely to occur than a single-bit error because the duration of the noise signal is normally longer than the duration of 1 bit, which means that when noise affects data, it affects a set of bits. For example, if we are sending data at 1 kbps, a noise of 1/100 second can affect 10 bits; if we are sending data at 1 Mbps, the same noise can affect 10,000 bits.burst error
- 11The central concept in detecting or correcting errors . To be able to detect or correct errors, we need to send some extra bits with our data. These redundant bits are added by the sender and removed by the receiver. Their presence allows the receiver to detect or correct corrupted bits.redundancy
- 12It can be performed in the data link layer. When a device creates a frame of data at the data link layer, it inserts some type of this code. When the frame arrives at the next device in the transmission sequence, the receiver extracts this and applies it to the data frame. Then, the data frame is reconstructed and sent to the next device in the transmission sequence.Error detection
- 13It is commonly used for ASCII characters where seven (7) bits are used for actual character encoding, and the eighth bit is for it. A simple method of error detection is by adding redundant bits called __ bits to each character.Parity Check (Vertical Redundancy Check) -
- 14the 0 or 1 added to the string produces an even number of binary 1s.even parity
- 15the 0 or 1 added to the string produces an odd number of binary 1s.odd parity
- 16blocks of data are organized as a two-dimensional array. This method increases the likelihood of detecting burst errors. Specifically, each row of the array is a data block that is to be transmitted. A parity bit is appended to each column based on if even or odd parity is used.Two-Dimensional Parity (Longitudinal Redundancy Check)
- 17It is a sequence of numbers and letters used to check data for errors. This sum is then added to the end of the message, and the message is transmitted to the receiving end. Many higher-level protocols used on the Internet (such as TCP and IP) use a form of error detection in which the characters to be transmitted are "summed" together.Arithmetic Checksum
- 18Arithmetic Checksum 2 sidessender’s side (checksum creation) and receiver’s side (checksum validation)
- 19This method treats the packet of data to be transmitted (the message) as a large polynomial, which adds 8 to 32 check bits to large data packets and yields an error-detection capability, approaching 100 percent. Review the XOR function and Binary Division. he remainder of the binary division is the CRC to be appended to the original message.Cyclic Redundancy Checksum
- 20The number of errors and the size of the message are important factors in dealing with __. These mechanisms deal with __ by retransmission.error correction
- 21Three (3) error control schemes based on the automatic repeat request (ARQ)Stop-and-Wait ARQ
Go-Back-N ARQ
Selective Repeat ARQ - 22It is used to deal with errors that occur when the stop-and-wait flow control protocol is used. Errors can occur in four ways:Stop-and-Wait ARQ -
- 23it deals with errors that occur when the sliding window protocol is used.Go-Back-N ARQ
- 24Under this scheme, only the frame in error is retransmitted. The drawback is that the receiver must provide enough buffer to store the frames that were transmitted after the erroneous frame until the frame has been retransmitted.Selective Repeat ARQ.
- 25ACK NAK ARQpositive acknowledgment (ACK)
negative acknowledgment (NAK).
automatic repeat request (ARQ)
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- easy Data and Digital Communications Fichas sobre 06 Handou 1, creado por Eljin Aguilar el 26/11/2024.
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- Eljin Aguilar
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