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Data and Computer Communications Chapter 8 – Multiplexing

Multiplexing Multiple links on 1 physical line Common on long-haul, high capacity, links To make efficient use of high-speed telecommunications lines, some form of multiplexing is used. Multiplexing allows several transmission sources to share a larger transmission capacity. A common application of multiplexing is in long-haul communications. Trunks on long-haul networks are high-capacity fiber, coaxial, or microwave links. These links can carry large numbers of voice and data transmissions simultaneously using multiplexing. Common forms of multiplexing are frequency division multiplexing (FDM), time division multiplexing (TDM), and statistical TDM (STDM). Stallings DCC8e Figure 8.1 depicts the multiplexing function in its simplest form. There are n inputs to a multiplexer. The multiplexer is connected by a single data link to a demultiplexer. The link is able to carry n separate channels of data. The multiplexer combines (multiplexes) data from the n input lines and transmits over a higher-capacity data link. The demultiplexer accepts the multiplexed data stream, separates (demultiplexes) the data according to channel, and delivers data to the appropriate output lines.

Data and Computer Communications Chapter 8 – Multiplexing

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1/28 Chapter 8 Multiplexing. 2/28 Multiplexing  To make efficient use of high-speed telecommunications lines, some form of multiplexing is used  Multiplexing.

Note Bandwidth utilization is the wise use of available bandwidth to achieve specific goals. Efficiency can be achieved by multiplexing; privacy and.

Presentation on theme: "Data and Computer Communications Chapter 8 – Multiplexing"— Presentation transcript:

1 Data and Computer Communications Chapter 8 – Multiplexing

Dr. Rami Dmaithan Halloush Department of Telecommunications Engineering Hijjawi Faculty for Engineering Technology Yarmouk University

2 Multiplexing Multiple links on 1 physical line

Common on long-haul, high capacity, links To make efficient use of high-speed telecommunications lines, some form of multiplexing is used. Multiplexing allows several transmission sources to share a larger transmission capacity. A common application of multiplexing is in long-haul communications. Trunks on long-haul networks are high-capacity fiber, coaxial, or microwave links. These links can carry large numbers of voice and data transmissions simultaneously using multiplexing. Common forms of multiplexing are frequency division multiplexing (FDM), time division multiplexing (TDM), and statistical TDM (STDM). Stallings DCC8e Figure 8.1 depicts the multiplexing function in its simplest form. There are n inputs to a multiplexer. The multiplexer is connected by a single data link to a demultiplexer. The link is able to carry n separate channels of data. The multiplexer combines (multiplexes) data from the n input lines and transmits over a higher-capacity data link. The demultiplexer accepts the multiplexed data stream, separates (demultiplexes) the data according to channel, and delivers data to the appropriate output lines.

3 Multiplexing The widespread use of multiplexing is due

The higher the data rate the more cost effective transmission facility Individual data communicating devices requires a modest data rate support

4 Multiplexing Frequency division multiplexing

Time division multiplexing Statistical TDM

5 Frequency Division Multiplexing

When bandwidth on transmission medium exceeds required for signals transmission Number of signals can be carried simultaneously Each signal is modulated on a different carrier frequency Carrier frequencies are sufficiently separated Freq. bands of signals don’t significantly overlap

6 Frequency Division Multiplexing

Six signal sources are fed into a mux Mux modulates each signal onto different frequency Each modulated signal requires certain bandwidth centered on its carrier frequency (channel) Channels are separated by guard bands (unused portions of the spectrum) Composite signal transmitted is analog Input may be digital or analog Digital input passed through modem Analog signal modulated move it to appropriate frequency band Frequency division multiplexing can be used with analog signals. A number of signals are carried simultaneously on the same medium by allocating to each signal a different frequency band. FDM is possible when the useful bandwidth of the transmission medium exceeds the required bandwidth of signals to be transmitted. A number of signals can be carried simultaneously if each signal is modulated onto a different carrier frequency and the carrier frequencies are sufficiently separated that the bandwidths of the signals do not significantly overlap. A general case of FDM is shown in Stallings DCC8e Figure 8.2a. Six signal sources are fed into a multiplexer, which modulates each signal onto a different frequency (f1, …, f6). Each modulated signal requires a certain bandwidth centered on its carrier frequency, referred to as a channel. To prevent interference, the channels are separated by guard bands, which are unused portions of the spectrum. The composite signal transmitted across the medium is analog. Note, however, that the input signals may be either digital or analog. In the case of digital input, the input signals must be passed through modems to be converted to analog. In either case, each input analog signal must then be modulated to move it to the appropriate frequency band.

7 Frequency Division Multiplexing

At sender: n analog or digital signals multiplexed on the same medium Each signal is modulated onto a subcarrier fi Modulated signals summed to form a composite signal Composite signal maybe modulated; i.e., shifted as a whole to another carrier frequency fc by additional modulation step At receiver: FDM signal is demodulated to retrieve the composite signals Composite signal is passed through n bandpass filters each centered on fi to split the signal into components Each component is demodulated to recover the original signal

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IM425UNIT22017 Flashcards

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Term 1 / 45 digital

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Definition 1 / 45

Data can exist in either analog or _________ form.

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Terms in this set (45)

digital

Data can exist in either analog or _________ form.

analog

A(n) _________ signal is one in which the signal intensity varies in a smooth fashion over time.

digital

A(n) _________ signal is one in which the signal intensity maintains a constant level for some period of time and then changes to another constant level.

periodic

The simplest sort of signal is a(n) _________ signal, in which the same signal pattern repeats over time.

peak amplitude

The __________ is the maximum height of the wave above or below a given reference point.

frequency

The _________ is the number of times the signal makes a complete cycle within a given time frame.

phase

________ is a measure of the position of the waveform relative to a given moment of time within the period of a signal.

wavelength

The _________ of a signal is defined as the distance between two points of corresponding phase of two consecutive cycles, such as maximum amplitudes or where the wave crosses zero.

spectrum

The _________ of a signal is the range of frequencies that it contains.

noise

For guided media such as twisted pair, coaxial cable, and optical fiber, the most significant sources of signal quality impairments are: attenuation and attenuation distortion, delay distortion, and __________.

crosstalk

The four categories of noise are: thermal noise, intermodulation, impulse noise, and __________.

crosstalk

__________ has been experienced by anyone who, while having a telephone conversation, has been able to hear another telephone conversation.

channel capacity

The rate at which data can be transmitted over a given communication path, or channel, under given conditions, is referred to as the ___________.

error rate

The designer of a communications facility must deal with four factors: the bandwidth of the signal, the data rate that is used for digital information, the amount of noise and other impairments, and the level of __________ that is acceptable.

bandwidth

The width of the range of frequencies that comprise the signal is the ________.

signals

________ are electric or electromagnetic representations of data.

signaling

_________ is the physical propagation of the signal along a communication medium.

transmission

__________ is the communication of data across a computer network by the propagation and processing of signals.

analog

_________ data take on continuous values on some interval; for example, voice and video are continuously varying patterns of intensity.

digital

________ data take on discrete values; examples are text, integers, and binary data.

analog signal

An _________ is a continuously varying electromagnetic wave that may be transmitted over both guided and unguided media.

digital signal

A _________ is a sequence of voltage pulses that may be transmitted over a wired medium; for example, a constant positive voltage may represent binary 0, and a constant negative value may represent binary 1.

modem

Converting digital data to analog signals involves the use of a _________.

codec

In an operation, very similar to that performed by a modem, analog data can be represented by a digital signal; the device that performs this function is a ________.

encoding

The mapping from binary digits to signal elements is the ________ scheme.

cable

A _______ modem permits Internet access over cable television networks.

synchronous

With ________ transmission, a block of bits is transmitted in a steady stream without start and stop codes.

error correction

The process of error control involves two elements: error detection and _________.

asymmetric digital subscriber line (ADSL)

The _________ is the most widely publicized of a family of modern technologies designed to provide high-speed digital data transmission over ordinary telephone wire.

asymmetric digital subscriber line (ADSL)

The data plus preamble, postamble, and control information are called a _________.

T-1

One of the most popular forms of synchronous TDM is known as ________.

frequency division multiplexing (FDM)

Although the use of ________ for voice transmission is declining, it is still used widely for television distribution systems, including broadcast television and cable TV.

physical interface

_________ standards provide a means by which a stream of data can be transmitted, either synchronously or asynchronously, onto a transmission medium.

flow control

________ is a technique for assuring that a transmitting entity does not overwhelm a receiving entity with data.

damaged

A __________ frame is a recognizable frame that arrives, but some of the bits have been altered during transmission.

wavelength-division multiplexing (WDM)

________ is used in fiber-to-the-home (FTTH) systems.

time-division multiplexing (TDM)

_________ is possible when the data rate of the transmission medium exceeds the required data rate of signals to be transmitted and a number of digital signals, or analog signals carrying digital data, can be carried simultaneously by interleaving portions of each signal in time.

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VLSI TECHNOLOGY

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The development of microelectronics spans a time which is even lesser than the average life expectancy of a human, and yet it has seen as many as four generations. Early 60’s saw the low density fabrication processes classified under Small Scale Integration (SSI) in which transistor count was limited to about 10. This rapidly gave way to Medium Scale Integration in the late 60’s when around 100 transistors could be placed on a single chip.

It was the time when the cost of research began to decline and private firms started entering the competition in contrast to the earlier years where the main burden was borne by the military. Transistor-Transistor logic (TTL) offering higher integration densities outlasted other IC families like ECL and became the basis of the first integrated circuit revolution. It was the production of this family that gave impetus to semiconductor giants like Texas Instruments, Fairchild and National Semiconductors. Early seventies marked the growth of transistor count to about 1000 per chip called the Large Scale Integration.

By mid eighties, the transistor count on a single chip had already exceeded 1000 and hence came the age of Very Large Scale Integration orVLSI. Though many improvements have been made and the transistor count is still rising, further names of generations like ULSI are generally avoided. It was during this time when TTL lost the battle to MOS family owing to the same problems that had pushed vacuum tubes into negligence, power dissipation and the limit it imposed on the number of gates that could be placed on a single die.

The second age of Integrated Circuits revolution started with the introduction of the first microprocessor, the 4004 by Intel in 1972 and the 8080 in 1974. Today many companies like Texas Instruments, Infineon, Alliance Semiconductors, Cadence, Synopsys, Celox Networks, Cisco, Micron Tech, National Semiconductors, ST Microelectronics, Qualcomm, Lucent, Mentor Graphics, Analog Devices, Intel, Philips, Motorola and many other firms have been established and are dedicated to the various fields in "VLSI" like Programmable Logic Devices, Hardware Descriptive Languages, Design tools,Embedded systems etc.

--->VLSI[very large scale integration] commonly classified in to two types

1)Front End design 2)Back End design

--->In earlier days computers were made of Vaccum tubes and it occupies the space in whole room.

--->The older computer performs 360 multiplications of 10 digits in a second.

--->Modern day computers are getting smaller,faster,cheaper and power efficient

The major design steps are

1)Problem Specification

2)Architectural Definition

3)Functional Design 4)Logic Design 5)Circuit Design 6)Physical Design

6.1)  Circuit Partitioning

6.2)  Floor Planning and Placement

6.3)  Routing

6.4)  Layout Compaction

6.5 Extraction and Verification

7)Packaging

---> The major parameters considered at this level are performance, functionality, physical dimensions, fabrication technology and design techniques.

--->The  specifications include the size, speed, power and functionality of the VLSI system.

--->Basic specifications like Floating point units, which system to use, like RISC[Reduced Instruction Set Computer],CISC[Complex Instruction Set Computer] , number of ALU’s cache size etc.

---> Interconnect requirements between units.

--->Physical and electrical specifications of each unit.

---> Boolean expressions, control flow, word width, register allocation etc. are developed and the outcome is called a Register Transfer Level (RTL) description. T

--->Netlist is done in this step.

--->Gates, transistors and interconnects are put in place to make a netlist.

--->The conversion of the netlist into its geometrical representation is done in this step and the result is called a layout.

--->Because of the huge number of transistors involved, it is not possible to handle the entire circuit

---> Hence the whole circuit is broken down into blocks which are interconnected.

--->Choosing the best layout for each block from partitioning step and the overall chip

---> Routing involves the completion of the interconnections between modules.

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