Y.E.S: Chapter9:Communications and Networks

COMMUNICATION CHANNELS

In telecommunications and computer networking , a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel.
A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) to one or several receivers.
This medium can be a physical wire or cable, or in can be wireless. (1)

Mobile devices networks :mobile telecommunications

Global System for Mobile Communications (GSM): divided into three major systems: the switching system, the base station system, and the operation and support system.
Personal Communications Service (PCS): PCS is a radio band that can be used by mobile phones in North America and South Asia. Sprint happened to be the first service to set up a PCS.
D-AMPS: Digital Advanced Mobile Phone Service, an upgraded version of AMPS, is being phased out due to advancement in technology.

1. Microwave

Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently.
Practical microwave technique tends to move away from the discrete resistors, capacitors, and inductors used with lower frequency radio waves.
The boundaries between far infrared light, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
Microwave is a good medium for sending data between building in a city or on a large college campus.

(2)

(3)

2.Satelite

A satellite is an object which has been placed into orbit by human endeavor.
Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.
Common types used Satellites include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and research satellites.
Satellites are usually semi-independent computer-controlled systems.
Types of satelite >Astronomical satellites >Biosatellites >Communications satellites >Miniaturized satellites >Navigational satellites >Reconnaissance satellites >Reconnaissance satellites >Space stations >Tether satellites >Weather satellites (5)

Global Positioning System (GPS):

>A simulation of the original design of the GPS space segment, with 24 GPS satellites (4 satellites in each of 6 orbits), (45ºN) on earth .

> Global navigation satellite systems (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage.

>GNSS allows small electronic receivers to determine their location to within a few metres using time signals transmitted along a line-of-sight by radio from satellites.(5)