Quiz 8: Data and Network Communication Technology

Computing

Effective Data Transfer Rate Calculation The block check character (BCC) adds one byte of data to each 48 bytes of raw data to be transmitted as a block. The details provided in the problem are given below: img Therefore, img The problem also states that img Therefore, for 1000 blocks img Since the problem states an average error rate of 1 per thousand, the number of transmissions becomes 1001. Therefore, img Therefore, the efficiency of the transmission is given as img The raw data rate is given as 10 Mbps. So the effective data transfer rate of the given problem is calculated below: img Therefore, the effective data transfer rate of the given transmission is img .

Error Detection and Correction in Memory Based on error detection, there are primarily two types of memory. There types are described below: • Parity Memory : Parity memory is the most widely used type of error detection memory. The memory has moderate fault tolerance, but is generally error free. Parity memory is a memory chip with built in error checking mechanisms. The errors are detected on start-up using an additional parity bit for each 8 bits of data. • Error Correcting Code (ECC) Memory : ECC memory is primarily used in critical situations where fault tolerance is very low such as in a server. ECC memory uses multiple additional bits to both detect and correct errors in data. Parity Checking in Memory Module The memory module counts the number of 1 value bits in each 8 bits (1 byte) of data. This count is called parity. The two types of parity are given below: • Even Parity : If the count of 1 value bits in a byte is odd, the parity bit is set to 1. If the count of 1 value bits in a byte is even or all bits are 0 valued, the parity bit is set to 0. • Odd Parity : If the count of 1 value bits in a byte is odd, the parity bit is set to 0. If the count of 1 value bits in a byte is even or all bits are 0 valued, the parity bit is set to 1. Error Detection and Response When the chip reads the data, the bits are again counted and compared with the parity bit. If the total does not correspond to the parity bit, the data are invalid and dumped with a new request for the same data again. Use Parity memory provides error detection mechanism and performance depends on the reliability of the memory hardware. Parity memory is primarily used in wide access non-critical systems such as home-based desktop computers. ECC memory provides both error detection and error correction mechanisms. The performance depends on the access rate of the memory hardware. ECC memory is primarily used in selective critical systems such as servers and defense related hardware.

Communication Channel A communication channel consists of a sending device, a receiving device, and the transmission medium connecting them. A communication channel is essentially a connection between a sender and a receiver for the transfer of data bits. The components of a communication channel are given below: • A sending device or transmitter • A receiving device or receiver • A transmission medium The basic structure of a communication channel is illustrated below: img