Deck 8: Data and Network Communication Technology

Question 1

Calculate the effective data transfer rate for a dedicated channel, given these characteristics: Data is transmitted in blocks of 48 bytes at 100 Mbps, an 8-bit BCC is used for error detection, and an error is detected, on average, once every 1000 transmitted blocks.

Answer 1

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:
Therefore,
The problem also states that
Therefore, for 1000 blocks
Since the problem states an average error rate of 1 per thousand, the number of transmissions becomes 1001. Therefore,
Therefore, the efficiency of the transmission is given as
The raw data rate is given as 10 Mbps. So the effective data transfer rate of the given problem is calculated below:
Therefore, the effective data transfer rate of the given transmission is
.

Question 2

Parity checking is often used in computer memory to detect errors. Investigate current memory types, including parity and error-correcting code (ECC) memory. How is parity checking implemented in the memory module? How are errors detected, and what happens when an error is detected? What types of computer systems should use parity or ECC memory, and why?

Answer 2

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.

Question 3

What are the components of a communication channel?

Answer 3

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:

Question 4

__________________transmission sends bits one at a time over a single transmission line or electrical circuit.

Question 5

For data transmitted over twisted-pair cable, you have these characteristics: A signal s power on the channel is 75 dB, signal attenuation is 5 dB per 100 meters, and average noise power on the cable is 0.1 dB per meter. Answer the following questions:
• What 's the S/N ratio at the end of a 50-meter channel?
• What 's the S/N ratio at the end of a 1-kilometer channel?
• What 's the maximum channel length if the receiving device requires at least 20 dB of S/N ratio for reliable operation?

Question 6

Research InfiniBand Architecture (www.infinibandta.org) to investigate some issues not addressed in the chapter. What signal encoding, cables, and connectors are used? Is the channel serial or parallel? Is transmission synchronous or asynchronous? How are errors detected and corrected?

Question 7

What are the components of a communication protocol?

Question 8

During half-duplex transmission, sender and receiver switch roles after A(n)____________________ message is transmitted.

Question 9

Investigate the IEEE FireWire data communication standard. How is data encoded, and what is the raw transmission speed? Describe how the standard enables quality of service guarantees when transmitting multimedia and other time-sensitive data.

Question 10

Describe frequency modulation, amplitude modulation, phase-shift modulation, and on-off keying.

Question 11

__________________encodes data by varying the distance between wave peaks in an analog signal.

Question 12

Investigate the IEEE 806.16 (WiMAX) wireless networking standard. How do transmission speeds and distances compare with the IEEE 802.11 standards? What methods are used to detect and correct transmission errors? Will 802.16 networks eventually replace 802.11 networks? Why or why not?

Question 13

How does multilevel coding increase a channel s effective data transfer rate?

Question 14

____________________ converts a digital signal to an analog signal so that digital data can be transmitted over analog phone lines.

Question 15

Describe the relationship between bandwidth, data transfer rate, and signal frequency.

Question 16

Serial transmission standards, including__________________ and__________________ , are replacing parallel transmission standards for connecting secondary storage devices and controllers.

Question 17

How can noise and distortion be introduced into a transmission medium? How does a channel s S/N ratio affect the reliability of data transmission?

Question 18

The __________________of a sine wave is measured in hertz.

Question 19

Compare twisted-pair, coaxial, twin-axial, multimode fiber-optic, and single-mode fiber-optic cable in terms of construction, susceptibility to EMI, cost, and bandwidth or transmission speed.

Question 20

Most local phone service uses __________________switching to route messages from a wired home phone to the local phone-switching center.

Question 21

What are the advantages of wireless transmission using RF waves compared with infrared and visible light waves?

Question 22

Most networks use__________________ switching to send messages from sender to receiver.

Question 23

Describe simplex, half-duplex, and full-duplex transmission and compare them in terms of cost and effective data transfer rate.

Question 24

In__________________ , a bit is added to each character or byte, and the bit value is determined by counting the number of 1 bits.

Question 25

Why is a channel s actual data transfer rate usually less than the theoretical maximum of the technology used to implement the channel?

Question 26

____________________ signal is a discrete signal that can encode only two possible values.

Question 27

Compare serial and parallel transmission in terms of channel cost, data transfer rate, and suitability for long-distance data communication. Why are standards for connecting secondary storage devices migrating from parallel to serial transmission?

Question 28

____________________ wave transports encoded data through a transmission medium.

Question 29

What are the differences between synchronous and asynchronous data transmission?

Question 30

With parity checking, sender and receiver must agree whether error detection is based on __________________or __________________.

Question 31

What is character framing? Why is it generally not an issue in parallel data transmission?

Question 32

A channel' s__________________ describes the mathematical relationship between noise power and signal power.

Question 33

Describe the differences between even and odd parity checking.

Question 34

__________________ is any change in a signal characteristic caused by components of the communication channel.

Question 35

What' s a block check character? How is it computed and used?

Question 36

For any error-detection method, a decrease in__________________ is accompanied by an increase in __________________error.

Question 37

Compare frequency-division and time-division multiplexing. What physical characteristics of the communication channel does each technique require? Which provides higher data transmission capacity?

Question 38

__________________ can t affect optical signals but can affect electrical or RF signals.

Question 39

What 's the difference between an amplifier and a repeater?

Question 40

A communication channel using electrical signals must have at least two wires A(n)____________________ and A(n)____________________ to form a complete electrical circuit.

Question 41

Compare IEEE 802.11b, 802.11g, and 802.11n wireless transmission in terms of raw data transfer rates, transmission frequencies, efficient use of available bandwidth, and susceptibility to noise and interference.

Question 42

__________________measures a channel s theoretical capacity. measures the actual capacity of a channel when a specific communication protocol is used.

Question 43

Multiple messages can be transmitted on a single transmission line or circuit by__________________ multiplexing or multiplexing.

Question 44

____________________ signal can encode an infinite number of possible numeric values.

Question 45

__________________is a measure of peak signal strength.

Question 46

In asynchronous transmission, at least one__________________ is added to the beginning of each message.

Question 47

The term__________________ describes encoding data as variations in one or more physical parameters of a signal.

Question 48

In______________ transmission, blocks or characters arrive at unpredictable times, and no signal is transmitted during idle periods.

Question 49

A medium __________________s is the difference between the highest and lowest frequencies that can be transmitted.

Question 50

__________________mode implements two-way transmission with two separate communication channels; __________________mode implements two-way transmission with only one communication channel.

Question 51

__________________encodes data by varying the magnitude of wave peaks in an analog signal.

Question 52

__________________ transmission uses multiple lines to send multiple bits simultaneously.

Question 53

____________________ extends a signal s range by retransmitting the signal without any noise or distortion from earlier transmission stages.

Question 54

generates A(n)____________________ consisting of a single parity bit for each bit position in the group of characters or bytes.

Question 55

In__________________ transmission, signals are transmitted continuously, even when there s no data to send, to ensure clock synchronization.

Question 56

__________________uses more than two signal characteristic levels to encode multiple bits in a single signal.

Question 57

__________________encodes bit values with rapid pulses of electrical or optical power.

Question 58

__________________ is noise added to the signal from EMI generated by adjacent transmission lines in a parallel communication channel.

Question 59

Frequency-division multiplexing of optical channels is sometimes called __________________.

Question 60

The length of a parallel communication channel is limited by __________________, which can cause bits to arrive at slightly different times.

Question 61

A receiver informs a sender that data was received correctly by sending A(n)____________________ message. It informs the sender of a transmission or reception error by sending A(n) __________________message.

Question 62

__________________is loss of signal strength as it travels through a transmission medium.

Question 63

Messages transmitted by time-division multiplexing are divided into____________ before physical transmission.

Question 64

_________________ cable is an improved version of Category 5 cable that transmits data at high speeds more reliably.

Question 65

Wireless LANs following the IEEE__________ ,________________ , and _________________standards transmit in the 2.4 GHz band.