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