Data Communications Flashcards
In a blank, data can only flow in one
direction, which is usually from the source to the sink.
simplex transmission
3 Dataflow Transmission
simplex transmission, half-duplex transmission, full-duplex transmission (FDX),
2 Data Transmission
Serial data transmission and Parallel data transmission
In a blank data can flow in both directions simultaneously. It can be viewed as a pair of simplex lines between the source and sink with one line going from the source to the sink and the other going from
the sink to the source.
full-duplex transmission (FDX),
In a blank , data can flow in both
directions, but never simultaneously. It first flows in one
direction, and then in the other direction.
half-duplex transmission
when data is sent or received, the data bits are organized in a specific order since they can only be sent one after another.
Serial data transmission
is used when data is transmitted as individual characters. In this method, each character is preceded by one start bit and one or two stop bits that are used by the receiver for synchronization purposes.
Asynchronous transmission
is used to transmit large blocks of data at a time. In this scheme, data is usually organized in frames and each frame is preceded by a flag that consists of a few bits and terminated by another flag.
Synchronous transmission
multiple data bits are transmitted over multiple channels at the same time.
Parallel data transmission
enables the transfer of information between two or more points that are connected by an electrical
conductor
Guided media
is a communication channel that carries the information from the sender to the receiver in which
data is transmitted through the electromagnetic signals via copper wire, fiber optics, atmosphere, water, and vacuum
Transmission media
refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber the optical cable.
Optical Fiber
it consists of two insulated copper wires that are typically about 1mm thick and
twisted together in a helical form
Twisted Pair
to facilitate two-way communication, the cable bandwidth is split into two
sets of channels: upstream channels and downstream channels.
Coaxial Cable
do not require physical links between two or more devices. Wireless communication is based on radio waves communications in the frequency spectrum.
Unguided media
These are easy to generate and can penetrate through buildings.
Radio waves
The sending and receiving antennas need not be aligned.
Radio waves
It is a line of sight (LOS) transmission i.e. the sending and receiving antennas need to be properly aligned with each other. T
Microwaves
Infrared waves are used for very short distance communication.
Infrared
They cannot penetrate through obstacles.
Infrared
It is the metal rod or dish that catches radio waves and turns them into electrical signals feeding into something like a
radio or television or a telephone system.
Antennas
It is a directional antenna that is made of a series of dipoles placed along its axis at
different space intervals of time followed by a logarithmic function of frequency.
Log Periodic Antennas
This type of antenna uses microwave transmission to broadcast signals between two or more locations
Microwave Antennas
It is a directional aperiodic antenna that uses a travelling wave as its guiding structure.
Traveling Wave Antennas
These antennas use a length of wire for transmitting and receiving wavelengths of signals.
Wire Antennas
A blank is a temporary wave that creates a disturbance and moves along the transmission line at a constant speed.
traveling wave
This type of antenna uses microwave transmission to broadcast signals between two or more locations.
Microwave Antennas
is a form of electromagnetic radiation that is used mostly in point-topoint communications and radar.
Microwave Antennas
It is the range of frequencies contained by a signal.
Frequency Spectrum
The following are the frequencies that are designated by the
International Telecommunications Union (ITU).
Frequency Spectrum
These waves are basically defined as superimposed oscillations of an electric and a magnetic field in space with their direction of propagation perpendicular to both.
Wave Propagation
This is used for a low-frequency range
transmission, mostly less than 1 MHz.
Ground Wave
This type of propagation employs the
use of large antennas order of which
is equivalent to the wavelength of the
waves and uses the ground or
Troposphere for its propagation.
Ground Wave
This is used for the propagation of EM
waves with a frequency range of 3-30
Mhz.
Sky Wave
These waves makes the use of
ionosphere in which it is the ionized
part of the earth’s upper atmosphere.
Sky Wave
This is used for a line of Sight communication (LoS).
Space Wave
satellite communication and very highfrequency waves use this propagation method.
space
is a way of sending multiple signals or streams of information over a communications link at the
same time in the form of a single, complex signal
Multiplexing
The receiver recovers the separate signals, a process called blank
demultiplexing.
The utilization of such media can be increased by allowing multiple users to transmit their data simultaneously, or close
to simultaneously.
Media Sharing Technique
where the frequency spectrum of the medium is partitioned into
multiple frequency blocks called channels that are assigned to users who can use these channels
simultaneously without interference from each other.
Frequency-division multiplexing (FDM)
where transmission time is divided into non-overlapping time slots that are
assigned to users.
Time-division multiplexing (TDM)
where the output signal, which appears like noise, occupies more bandwidth than the
original signal.
Spread spectrum (SS)
means that each station on the LAN continually listens to (tests) the cable for the
presence of a signal before transmitting.
Carrier Sense
4 Media Access Methods
Carrier Sense Multiple Access with Collision Detection (CSMA/CD),
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA),
Token passing, Demand priority
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
Carrier Sense, Multiple Access , Collision Detection
means that many computers are attempting to transmit and compete for the
opportunity to send data (i.e., they are in contention)
Multiple Access
means that when a collision is detected, the stations will stop transmitting and
wait a random length of time before retransmitting the data
Collision Detection
Instead of detecting and reacting to collisions, CSMA/CA tries to avoid them by having each computer
signal its intention to transmit before transmittin
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
It is a media access method by which collisions are prevented.
Token passing
Collisions are eliminated under token
passing because only a computer that possesses a free token (a small data frame) can transmit.
Token passing
In demand priority, an active hub is an essential requirement that can control access to the network.
Demand priority
The terminals on a network are required to obtain permission from the hub before they start
transmitting the bytes over a network.
Demand priority
A blank is an architecture used to interconnect two (2) devices together.
hardware interface
It includes the design of the plug
and socket, the type, and the number and purpose of the wires and the electrical signals that are passed across them.
hardware interface
2 Characteristics of Interface Standards
De facto standard, Composition
it is the whole content of an entity of an interface standard
Composition
it is something that is used so widely that it is considered a standard for a given
application although it has no official status.
De facto standard
4 Composition
Electrical component, Mechanical component, Functional component , Procedural component
deals with voltages, line capacitance, and other electrical issues.
Electrical component
deals with items such as the connector or plugs description.
Mechanical component
deals with the function of each pin used in an interface.
Functional component
describes how the circuits are used to perform an operation.
Procedural component
It is a digital interface that uses a standardized connector
(plug) for all serial and parallel type devices which provides a digital interface and known for being hot-pluggable
Universal Serial Bus (USB)
It is a type of interconnection between peripheral devices (such as wireless
modems and high-speed digital video cameras) and a microcomputer.
Fire Wire
It is currently found on Apple laptops and provides a 10-Gbps connection
to peripheral devices
Thunderbolt
It is an 8-pin connector in which it can be found as the primary connector on
the newer versions of Apple’s iPhone as well as Apple devices such as the iPad.
Lightning
is like InfiniBand in that it too is a serial, high-speed network that
connects a computer to multiple input/output devices
Fibre Channel
This interface is used due to its high-speed connection that is mostly found
in networks that require large amounts of peripheral storage
InfiniBand
is a technique for
interfacing a computer to high-speed devices such as hard disk drives, tape drives, CDs,
and DVDs
Small Computer System Interface
The sender prepares a data character for transmission, transmits that character with irregular timing, and then begins preparing the next data character for transmission.
Asynchronous connection
a single character, or byte of data, is the unit of transfer between the sender and receiver.
Asynchronous connection
Data Link Connections
Asynchronous connection, Synchronous connection -
the unit of transmission is a sequence of characters. This sequence of characters may be thousands of characters in size with regular timing sent.
Synchronous connection
The blank capabilities of various media vary differently depending upon the various factors
Data Transmission Factors
a special kind of data link connection used to support various types of real-time applications such as streaming voice, video, and music.
Isochronous connection
Data Transmission Factors
Bandwidth, Radiation, Noise Absorption, Attenuation
refers to the data-carrying capacity of a channel or medium. Higher bandwidth communication channels support higher data rates.
Bandwidth
refers to the leakage of signal from the medium due to undesirable electrical characteristics of the
medium.
Radiation
refers to the susceptibility of the media to external electrical noise that can cause distortion of the data signal.
Noise Absorption
refers to the loss of energy as signal propagates outwards. The amount of energy lost depends on frequency. Radiations and physical characteristics of media contribute to attenuation.
Attenuation
Bandwidth and Throughput
Bandwidth is the measurement of the ability of an electronic communications device or system to send and
receive information. There are two terms:
Bandwidth in blank is the range of frequencies contained in a composite signal or the range of
frequencies a channel can pass
Hertz
is the measurement of the ability of an electronic communications device or system to send and receive information. There are two terms:
Bandwidth
The term bandwidth can also refer to the number of bits per second that a channel, a link, or even a network can transmit.
Bits per Seconds
is the amount of data that enters and goes through a system. In layman’s term, it is a measure of how fast we can actually send data through a network.
Throughput
It is a measure of delay. It measures the time it takes for data to get to its destination across the network
Latency
Bit Rate and Baud Rate
Bit Rate, Baud Rate
is the amount of data (number of bits) that can be transmitted per second
Bit Rate
refers to the number of signal elements or symbol changes that occur per second. A symbol is one of several voltage, frequency, or phase changes.
Baud Rate
Data Transfer Technique
switched network, broadcast network
In a blank, data is transferred from source to destination through a series of intermediate switching
nodes. Data passes through a subset of the network nodes.
switched network
involves establishing a path from source to destination before the commencement of
communication
Circuit switching
involves organizing data in blocks called packets that are sent in a store-and-forward manner without prior establishment of the communication path.
Packet switching
In a blank, a transmission from a source is received by all nodes in the network.
broadcast network
A broadcast network ensures that all the nodes in the network see the transmitted data.
broadcast network
