Role of Pulse Shaping in Communication Systems:

The duals – Sinc and Rectangular Functions
In communication systems, data is transmitted as binary bits ( ones and zeros). It is easier to implement a binary system using switches, where turning on a switch represents ’1′ and turning it off represents ’0′. Such simple binary systems essentially represents ones and zeros as rectangular pulses of finite duration (say τ).
In frequency domain a rectangular pulse of finite duration τ manifests itself as a sinc pulse of infinite duration. Also, most of the energy of the rectangular pulse is concentrated with in -1/τ to 1/τ in the frequency domain. This implies a pulse of duration τ requires twice its bandwidth for reliable transmission. This poses a limitation when it comes to bandwidth limited system, if we wish to increase the transmission data rate. The challenge here is, how do we transmit the data with highest possible data rate in a given band-limited system. The answer is : Pulse Shaping.