Module 02 Flashcards
What is a parity bit?
A simple error detection mechanism that adds an extra bit to a data sequence to indicate whether the number of 1s is even or odd.
It helps in detecting errors during transmission.
What is even parity?
The parity bit is set so that the total number of 1s in the data (including the parity bit) is even.
Example: Data 1011 (3 ones → odd) requires a parity bit of 1 to make the total count even.
What is odd parity?
The parity bit is set so that the total number of 1s is odd.
Example: Data 1011 (3 ones → odd) keeps the parity bit as 0 to maintain an odd total.
How does a parity bit help in error detection?
If a single bit flips during transmission, the parity no longer matches, indicating an error.
Example: Sent data 10111 received as 10011 with incorrect parity detects an error.
What are the limitations of parity bits?
Cannot correct errors, only detects them; fails for even-numbered bit errors.
Example: Flipping two bits maintains parity and goes undetected.
List three applications of parity bits.
- Serial communication protocols (e.g., UART, RS-232)
- Memory error detection (e.g., older RAM modules)
- Network transmission (basic error-checking in communication systems)
What is a checksum?
A simple error detection method used to verify data integrity during transmission or storage.
It is calculated using a mathematical function on the data.
How does checksum verification work?
The receiver recalculates the checksum from the received data and compares it with the transmitted checksum.
A mismatch indicates an error.
What is a simple checksum (modulo sum)?
Adds up all bytes or words of data and takes the modulo of a fixed number (e.g., 256 or 65536).
Example: For data 1011 1100 1001, the checksum modulo 16 is 0010.
What is an XOR checksum?
Uses bitwise XOR operation on all bytes of data to detect single-bit errors effectively.
What is a Cyclic Redundancy Check (CRC)?
An error-detection technique using polynomial division to generate a checksum appended to data.
It ensures data integrity during transmission.
List the steps involved in CRC calculation.
- Data representation as a binary sequence
- Appending zeros based on generator polynomial
- Polynomial division using modulo-2 division
- Transmitting data with CRC checksum
- Receiver verification
What are common CRC standards?
- CRC-8: ATM, Bluetooth
- CRC-16: USB, XMODEM
- CRC-32: Ethernet, ZIP, PNG
- CRC-64: Storage, Security
What are some advantages of CRC?
- Highly reliable for detecting burst errors
- Fast computation using XOR operations
- Lightweight implementation in hardware and software
What are the limitations of CRC?
- Cannot correct errors, only detects them
- Fails for some specific error patterns
What is an Information Transmission System?
A structured process that enables the transfer of information from a sender to a receiver through a communication channel.
List the components of an Information Transmission System.
- Source (Sender)
- Encoder
- Transmission Channel
- Noise
- Decoder
- Receiver
- Feedback (Optional)
What is analog transmission?
Continuous signals that vary in amplitude and frequency.
Example: Radio, TV broadcasting, telephone calls.
What is digital transmission?
Data is transmitted in discrete binary format (0s and 1s).
Example: Internet, mobile networks, digital television.
What is the Shannon-Weaver Model?
A mathematical model describing the communication process with key features: Source → Encoder → Channel → Decoder → Receiver.
What are error detection techniques in transmission?
- Parity Bits
- Checksums
- Cyclic Redundancy Check (CRC)
What are error correction techniques mentioned?
- Hamming Codes
- Reed-Solomon Codes
- Turbo Codes
- LDPC (Low-Density Parity-Check) Codes
List applications of Information Transmission Systems.
- Telecommunication networks
- Computer networks and the Internet
- Broadcasting
- Data storage and cloud computing
- IoT and embedded systems
True or False: CRC can correct errors.
False
