DATA COMM. - Midterms (copy)

simplex transmission

data can only flow in one direction, which is usually from the source to the sink.

half-duplex transmission (HDX)

data can flow in both directions, but never simultaneously. It first flows in one direction, and then in the other direction.

full-duplex transmission (FDX)

data can flow in both directions simultaneously.

Serial data 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.

Asynchronous transmission

is used when data is transmitted as individual characters.

Synchronous transmission

is used to transmit large blocks of data at a time.

Parallel data transmission

multiple data bits are transmitted over multiple channels at the same time.

Transmission media

is a communication channel that carries the information from the sender to the receiver in which data is transmitted through the electromagnetic signals.

Transmission media

is to carry the information in the form of bits through the network.

Guided media

enables the transfer of information between two or more points that are connected by an electrical conductor.

Twisted Pair

it consists of two insulated copper wires that are typically about 1mm thick and twisted together in a helical form.

Coaxial Cable

to facilitate two-way communication, the cable bandwidth is split into two sets of channels: upstream channels and downstream channels.

Optical Fiber

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.

Unguided media

do not require physical links between two or more devices.

Wireless communication

is based on radio waves communications in the frequency spectrum.

Radio waves

These are easy to generate and can penetrate through buildings.

Microwaves

It is a line of sight (LOS) transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. These are majorly used for mobile phone communication and television distribution.

Infrared/Infrared waves

are used for very short distance communication.

Antennas

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.

Log Periodic 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.

Wire Antennas

These antennas use a length of wire for transmitting and receiving wavelengths of signals.

Traveling Wave Antennas

it is a directional aperiodic antenna that uses a travelling wave as its guiding structure.

traveling wave

is a temporary wave that creates a disturbance and moves along the transmission line at a constant speed.

Microwave Antennas

This type of antenna uses microwave transmission to broadcast signals between two or more locations.

Microwave

is a form of electromagnetic radiation that is used mostly in point-to-point communications and radar.

Frequency Spectrum

It is the range of frequencies contained by a signal.

Wave Propagation

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.

Ground Wave

This is used for a low-frequency range transmission, mostly less than 1 MHz. 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.

Sky Wave

This is used for the propagation of EM

waves with a frequency range of 3-30

Mhz. These waves makes the use of ionosphere in which it is the ionized part of the earth's upper atmosphere.

Space Wave

This is used for a line of Sight communication (LoS). Space satellite communication and very high-frequency waves use this propagation method.

Multiplexing (MUX)

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.

demultiplexing

It is a process where the receiver recovers the separate signals.

Media Sharing Technique

The utilization of such media can be increased by allowing multiple users to transmit their data simultaneously, or close to simultaneously.

Frequency-division multiplexing (FDM)

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.

Time-division multiplexing (TDM)

where transmission time is divided into non-overlapping time slots that are assigned to users. Transmissions are staggered using a round-robin method to schedule the transmissions.

Spread spectrum (SS)

where the output signal, which appears like noise, occupies more bandwidth than the original signal.

Carrier Sense

means that each station on the LAN continually listens to (tests) the cable for the presence of a signal before transmitting.

Multiple Access

means that many computers are attempting to transmit and compete for the opportunity to send data.

Collision Detection

means that when a collision is detected, the stations will stop transmitting and wait a random length of time before retransmitting the data.

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Instead of detecting and reacting to collisions, it tries to avoid them by having each computer signal its intention to transmit before transmitting.

Token passing

It is a media access method by which collisions are prevented. Collisions are eliminated under token passing because only a computer that possesses a free token (a small data frame) can transmit.

Demand priority

an active hub is an essential requirement that can control access to the network.

hardware interface

is an architecture used to interconnect 2 devices together. 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.

De facto standard

it is something that is used so widely that it is considered a standard for a given application although it has no official status.

Composition

it is the whole content of an entity of an interface standard.

Electrical component

deals with voltages, line capacitance, and other electrical issues.

Mechanical component

deals with items such as the connector or plugs description.

Functional component

deals with the function of each pin used in an interface.

Procedural component

describes how the circuits are used to perform an operation.

Universal Serial Bus (USB)

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.

Hot plugging (hot swapping)

is the ability to add and remove devices to a computer system while the computer is running and have the operating system automatically recognize the change.

Fire Wire

It is a type of interconnection between peripheral devices (such as wireless modems and high-speed digital video cameras) and a microcomputer.

Thunderbolt

It is currently found on Apple laptops and provides a 10-Gbps connection to peripheral devices.

Lightning

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.

SCSI - SCSI (Small Computer System Interface)

is a technique for interfacing a computer to high-speed devices such as hard disk drives, tape drives, CDs, and DVDs.

InfiniBand

This interface is used due to its high-speed connection that is mostly found in networks that require large amounts of peripheral storage.

Fibre Channel

is like InfiniBand in that it too is a serial, high-speed network that connects a computer to multiple input/output devices.

Asynchronous connection

a single character, or byte of data, is the unit of transfer between the sender and receiver.

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.

Isochronous connection

a special kind of data link connection used to support various types of real-time applications such as streaming voice, video, and music.

Bandwidth

refers to the data-carrying capacity of a channel or medium.

Radiation

refers to the leakage of signal from the medium due to undesirable electrical characteristics of the medium.

Noise Absorption

refers to the susceptibility of the media to external electrical noise that can cause distortion of the data signal.

Attenuation

refers to the loss of energy as signal propagates outwards.

Bandwidth

is the measurement of the ability of an electronic communications device or system to send and receive information.

Hertz

is the range of frequencies contained in a composite signal or the range of frequencies a channel can pass.

Bits per Seconds

The term bandwidth can also refer to the number of bits per second that a channel, a link, or even a network can transmit.

Throughput

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.

Latency

It is a measure of delay. It measures the time it takes for data to get to its destination across the network.

Propagation time

measures the time required for a bit to travel from the source to the destination.

Transmission time

measures the time how long a message will pass in channel corresponding with the bandwidth.

Queuing time

measures the time needed for each intermediate or end device to hold the message before it can be processed.

Processing delay

measures how data is processed through or from links.

Bit Rate

is the amount of data (number of bits) that can be transmitted per second.

Baud Rate

refers to the number of signal elements or symbol changes that occur per second.

symbol

is one of several voltage, frequency, or phase changes.

swtiched network

data is transferred from source to destination through a series of intermediate switching nodes.

Circuit switching

involves establishing a path from source to destination before the commencement of communication.

Packet switching

involves organizing data in blocks called packets that are sent in a store-and-forward manner without prior establishment of the communication path.

broadcast network

transmission from a source is received by all nodes in the network. Itcensures that all the nodes in the network see the transmitted data.