Channel Models

Jan 22 • Engineering Notes • 1372 Views • 2 Comments on Channel Models

Channel Models

Narrowband  Channel

Channel Models it describes a channel models in which the bandwidth of the message does not significantly exceed the channel’s coherence bandwidth of the channel.In the study of wireless communication channels narrow band channels implies that the channel under consideration is sufficiently narrow that is frequency response can be considered flat of that signal. The message bandwidth is  therefore be less than the coherence bandwidth of the channel of the signal. This is usually used as an idealizing assumption as no channel has perfectly flat fading but  if the analysis of many aspects of wireless systems is greatly simplified then flat fading can be assumed quickly .Narrowband can be used with the audio spectrum so as  to describe sounds which occupy a narrow range of frequencies. The telephony channel has narrowband which is usually considered to cover frequencies 300–3400 Hz.

Wideband Channel

A system is wideband when the message bandwidth exceeds the bandwidth of the coherence channel in the communication.  In some communication channels links have a high data rate so that they are forced to use a wider bandwidth and other links may have low data rates but use a wider bandwidth that is “necessary” for that data rate in order to gain more advantages in communication.

Antenna

Introduction

150px-Canberra_Deep_Dish_Communications_Complex_-_GPN-2000-000502It is also known as aerial. It is an electrical device which helps in converting  the electric power into radio waves & vice versa. Usually uses a radio transmitter or radio receiver. During transmisson of  sgnal a radio transmitter supplies an oscillating frequency of radio signal in the form of electric current to the  terminal of the antenna and the antenna radiates the energy from the current as radio waves in the transmission.During reception an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals which is applied to a receiver for amplification  of the signal.

Antennas for base station

antenna2There are mobile phone base station antennas  situated on towers and buildings throughout  the area. These antennas are part of the mobile telephone network which emit radiation consisting radio frequency through the signal. The fact i.e. the radiation provides the possibility of adverse health effects arising from exposure to this radiation.

 

Antennas for mobile station

INSTALLATION-GSM-ANTENNA[1]

There are mobile station antennas on towers and buildings throughout  the locations. These type of  antennas are part of the mobile telephone network and they emit radiation consisting radio frequency.

Some related question and answer 

1. What does the narrow band channel band implies?

Ans. In wireless communication channels narrow band channels implies that the channel under consideration is sufficiently narrow where a frequency response can be considered flat.

2. when a system has wideband?

Ans. A system has wide band when the message bandwidth exceeds the bandwidth of the coherence channel.

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2 Responses to Channel Models

  1. this is a good article it clearly explains the channel models.

  2. Dinesh says:

    By traveling on the road side i have seen all this antennas but after reading article only i came to know the difference about these antennas

    very useful post

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