unbouded media

• unbouded media is media transport electromagnetic waves without using a physical conductor.
• signals are broadcast through air or water.

They are two type of antenna 

                                                                                                                                

Parabolic dish

it is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish.

Horn antenna

A horn antenna is used for the transmission and reception of microwave signals. It derives its name from the characteristic flared appearance. The flared portion can be square, rectangular, or conical. The maximum radiation and response corresponds with the axis of the horn. In this respect, the antenna resembles an acoustic horn. It is usually fed with a wave guide.

Satellite microwave

Satellite micro wave transmission is used to transmit signals through out the world. These system use satellites in orbit about 50,000 Km above the earth. Satellite dishes are used to send the signals to the satellite where it is again send back down to the receiver satellite. These transmissions also use directional parabolic antenna’ with in line of side.

In satellite communication micro wave signals at 6 GHz is transmitted from a transmitter on the earth through the satellite position in space. By the time signal reaches the satellites becomes weaker due to 50,000 Km distance. The satellite amplifies week signals and transmits it back to the earth at the frequency less than 6 GHz.

3G

3G system is based on wideband CDMA that operates in 5 MHz of bandwidth and can produce download data rates of typically 384 kb/s under normal conditions and up to 2 Mb/s in some instances. Another 3G standard, cdma2000, was developed by Qualcomm. It uses 1.25 MHz bands to produce data rates to 2 Mb/s. Another version of cdma2000 is an improved IS-95 version. It is a 3GPP2 standard. It can transmit data at a rate to 153 kb/s and up to 2 Mb/s in some cases.

4G

The fourth generation has been defined but we are not in it, yet. Yes, many if not most of the mobile carriers and the various phone and equipment manufacturers actually advertise 4G now. The formal definition of 4G as declared by the 3GPP and the ITU-T is something called Long Term Evolution-Advanced (LTE-A). The standard has not been fully completed but basically it is an improved and enhanced version of LTE that uses wider bandwidth channels and a greater number of MIMO antennas. The theoretical upper data rate is 1 Gb/s. That remains to be seen in practice.

differences between 3G & 4G

1. 3G stands for 3rd generation while 4G stands for 4th generation
2. 3G technologies are in widespread use while 4G compliant technologies are still in the horizon
3. 4G speeds are much faster compared to 3G
4. 3G is a mix of circuit and packet switching network while 4G is only a packet switching network

Cellular phone

is a device that can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile phone operator, allowing access to the public telephone network. By contrast, a cordless telephone is used only within the short range of a single, private base station.
In addition to telephony, modern mobile phones also support a wide variety of other services such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, gaming and photography. Mobile phones that offer these and more general computing capabilities are referred to as smartphones.