Hi Friends......

I am going to write about wireless communication.As this field is very interesting to me hopefully all of you will like this blog.

           

For a better understanding of todays wireless systems a short history of wireless communication is necessary to understand.

History:

            The use of light for wireless communication reaches back to ancient times.In former times,the light was modulated using mirrors to create a certain light pattern.The use of smoke signals for communication is mentioned by Polybius,Greece,as early as 150 BC.It is also reported from the early Han dynasty in ancient China that light was used for signalling messages along a line of signal towers towards the capital Chang"an.Using light and flags for wireless communication remained important for the navy until the radio transmission was introduced and even today a sailor has to know some codes represented by flags if all other means of wireless communication fail.

 Wired communication started with the first commercial telegraph line between Washington and Baltimore in 1843 and Alexander Graham Bell's invention of the telephone in 1876.

All optical transmission systems suffer from the high frequency of the carrier light.As every little obstacle shadows the signal,rain and fog make communication almost impossible.At that time it was not possible to focus light as efficiently as can  be done today by means of laser,wireless communication did not really take off until the discovery of electromagnetic waves and the development of equipment to modulate them.

 

 

Sidra  Usman