Comparative Study of the Performance of Different Digital Modulation Schemes

Abstract

The choice of a digital modulation scheme to be used in a given application depends on the most desired performance parameters in that application. Different communication set up requires different performance parameters to be set to priority. Wireless communication requires spectrum efficient modulation and demodulation schemes under limited bandwidth. Modulation scheme that requires the least power to transfer information are also desirable as well as modulation schemes that offer the least bit error rate at the receiver. These performance parameters need to be set right to avoid misplacement of priority in a given communication set up. Knowing the parameters for the different modulation schemes and the relationship between the parameters will enable the designer to make a wise choice on the best suited digital modulation scheme to be used in a particular application. We shall compare different digital modulation schemes based on four different performance parameters - Spectral efficiency, power efficiency and bit error rate and signal-to-noise ratio. We shall calculate their numerical values for a given application, show relationship between them and suggest application where they are best suited for in order to help the designer make a wise choice on the choice of a modulation scheme that best suits his communication link design. As we shall see, we cannot achieve the best value for all four simultaneously; one needs to be traded for another most times. We shall be comparing the Binary phase shift keying (BPSK), Quadrature phase shift keying (QPSK) and 8-Level phase shift keying (8-PSK) modulation schemes.