DESIGN OF WIRELESS COMMUNICATION SYSTEM ON SDR USING M-QAM MODULATION

Abstract

Basic idea of this project is to design a communication channel using software defined radio.The main purpose of Software Defined Radio was to design a device which should be competent of working with many radios working at different parameters. Software Defined Radio provide an rational and economical solution for building multi-mode, multi-range and multifunctional wireless devices that can be revamped by means of software furtherance. In a PC significant signal processing can be done via SDR. In SDR, signal worked in digital sphere rather in analog sphere as in the orthodox radio. The analog signal can be changed to the digital domain with the aid of Analog to Digital converter. In the digital QAM, a fixed number of two phases and minimum two amplitudes are used. PSK modulation scheme are often made with the QAM theory, but are not deemed as QAM as the amplitude of the modulated carrier signal is same. We are using the QAM because of the issue that a amplitude modulated signal, i.e. double sideband with a suppressed carrier occupies two times the bandwidth of the modulating signal. Assumingly large spectral efficiencies can be get with QAM by adjusting a acceptable constellation range, fixed only by the noise stages and linearity of the communications channel. Quadrature amplitude modulation (QAM) is combination of analog and a digital modulation system. It fetchs two analog message signals, or two digital bit streams, by amending (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation system. The carrier signals of the like frequencies, mostly sinusoids, are out of phase with one other by 90° and are called quadrature carriers or quadrature parts — so the name of the system. The modulated waves are added, and the end waveform is a merger of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or, in the analog system, of phase modulation (PM) and amplitude modulation.