Introduction of Wireless Networks contd...

Signal

Definition: 1. Signals are nothing but they are the physical representation of data.

                   2.Mathematically, we can say that signals are functions of time and location. so the following is the right representation for signal:-   f(x,t)

Here f(x,t) represents the signal which is the function of location and time.

                      

                    Users of communication uses these signals for communication. Here,signal parameters represents the data values which are to be transmitted from sender to receiver.

                     

For radio transmission, the periodic signals (i.e. sine wave ) are used as carriers. The general form of a sine wave is :    g(t) = A sin (2 pi f t + phi t)

The signal parameters are the 

                     

 Amplitude --> A

Phase Shift --> phi

frequency   --> f

Here the amplitude as a factor of the function g may also change over time.

The frequency f expresses the periodicity of the signal over with the period (T = 1/f).

The  frequency f may change over time.

Now , the remaining signal parameter is phi which represents the phase shift of the signal. The phase shift determines the shift of the signal relative to the same signal without a shift .

NOTE: 

• Shifting of phase is also used to represent data.                  
• Sine wave has  special emphasis as it is possible to construct every periodic signal g by using only sine and cosine function according to a fundamental eqn of FOURIER.