DATA COMMUNICATION REVIEW

Understanding Data Communications.
Data communication is electronic data transmission through several media.
These media can be a coaxial cable, fiber optic, microwave and
forth. System that allows data transmission is often
data communications network is called. This network is an important component
of the information carried by the community now.

The function of data communication systems:
1. Must be able to give information to the right people too.
2. Data communication systems must obtain a business data while the data
made.
3. Data communication system enables people and businesses who have
different geographic locations can communicate with each other.

The basic components of data communication systems.
Data communication systems can be divided into three main components:
1. Communication source.
2. Communications media.
3. Recipient (sometimes called a sink or host).

Introduction to data communication networks.
Network is a series of several points that are connected by several
types of communication channels. Each point (called node) is a computer,
although it may consist of changing equipment, printers, FAX machines or
other tools. Data communication network is a collection of communication circuits
data is managed as a single unit. Collection of communications networks
data and those who enter data, which receives the data and manage
and forming a network control communications systems.

Communications via satellite.
Although there are systems terrestrial cellular mobile communications, this system
only efficient to serve the densely populated areas. Cellular system
conventional, economically not feasible for mobile communication
in rural areas, where population density and the need for communication
still very low.
Utilization of satellite communications systems has provided the ability for
humans to communicate and obtain information from various parts
world simultaneously regardless of their relative distance.

Satellite transmission.
The basic components of satellite transmission is the earth station, which is used
to send and receive data, and satellite, is sometimes called
transponder. The satellite receives signals from earth stations (up-link), strengthening
the signal, change the frequency, and transmit data back to
earth station receiver other (down-link). If the change in frequency
happens the up-link will not disturb the down-link.
In satellite transmissions, there is a delay or a delay, because the signal must
walked out into space and back again to earth. Time delay
usually is 0.5 seconds. There is also an additional delay caused by
the time required to run the signal through the earth station.
As mentioned earlier, the satellite using a frequency
different to receive and transmit. Frequency range is between 4
up to 6 GHz, which is also called the C-band; 12 to 14 GHz is called Ku-band and
20 to 30 GHz. When the frequency falls, the size of the dish-antenna
required to receive and transmit the signal should be increased.
Ku-band is used to transmit television programs between the network and
individual television stations. Because the signal is in the Ku-band
have a higher frequency then the shortened wavelength.
This allows the receiver and the transmission station to concentrate its
signals and use the dish-antenna smaller.
Security is a problem for satellite communications, because it's easy
to capture the transmission, because he walked through the open air.
In some cases, pengurai (Scrambler) is used to distort the signal
before he was sent to the satellite and the author (descrambler) which is in
receiver stations used to produce the original signal back.