To many users, antennas are just one of life\'s great mysteries. They know from

Question

To many users, antennas are just one of life's great mysteries. They know from experience that any antenna is better than having no antenna, and that the higher the antenna is located, the better the reception will be. Yet the antenna is arguably one of the most important parts of a wireless network. Antennas play a vital role in both sending and receiving signals, and a properly positioned and functioning antenna can make all the difference between a wireless LAN operating at peak efficiency or a network that nobody can use. Use the Internet to research antennas for APs. What different types of antennas are used? What are their strengths? What are their weaknesses? Which types would be used to concentrate a signal to a more confined area? Write a one-page paper on what you find

Explanation / Answer

A major and very important component of the wireless communication is antenna.

As in wireless communication the wires are done away with so the name wireless i.e. without wires. Then to connect the components of communication antennas are used.The signals in wireless communication travel freely in space without guidance unlike wired communication where the path is guided by the wire. So these signals need to be given out to space from communicating component and the signals travelling in space need to be catched by a device this device is antenna i.e. at sender side the the signals (energy ) are coupled outside by antenna called transmitter and at receiver side the signals from outside are coupled to the antenna. And antennas are connected physically to the communicating device

IN WLAN AP is access point which facilitates communication between various station(STA)

Following types of anteenas are there:-

Isotrophic radiator :- An ideal kind of antenna which transmits equal power in all direction the points with equal power forms a sphere and center of this sphere is antenna i.e. a symmetric radiation pattern.

This is a very much a theory concept and non-existent in reality.

Directive antennas:- antennas in reality are actually directive i.e. the power is not same in all direction.

With simplest antenna being hertzian dipole which is center fed and thin and is made of two collinear conductors which are of equal length and the length is fixed and the conductors have a gap between them.

Omnidirectional Antenna:- Such antenna have a 360 degree coverage thus providng the widest possible cover The main type of omnidirectional antenna used by AP is rubber duck antenna.

Such antennas form a uniform pattern in one plane.

And in other two plane an eight figure of pattern is formed.

Advantages and disadvantages:-

Such an antenna has the disadvantage of it being covering the whole area even if the requirement is not such wide thus wasting lot of power and the actual recepient does not get the whole power. Thus only way to enhance the power in one direction is by increasing the power in all direction to overcome various environmental challenge.

It can be easily installed

low distortion

lower sensitivity

Range is less

less precise in diffuse field

Directional Antenna:- In this antenna the signal is transmitted and received in preferred direction such an antenna is useful in places like valley, between buildings and all eg:- satellite dish

Advantages and disadvantages:-

These antennas are widely used in cellular systems.

Frequency reuse

More sensitive

Higher distortion

less smooth

Good in both near and diffuse field

More powerful

Line of sight needed

Network planning difficult

Complex Installation

Less loss, limited eavesdropping

Sectorized Antenna:- Many directional antenna are combined together such antennas can have different antennas and they create different sector with different coverage. Thus hlping in frequency reuse.

The directional antennas are used to concentrate a signal to a more confined area

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