Differentially Encoded Quadrature Phase Shift Key Communication and Real-Time Implementation

摘要

Robust communication methods are integral to advances in modern technology. Software defined radios (SDRs) have been the chief instruments of communication for the last three decades. Upcoming generations of wireless networks and phone systems depend on successful implementations of increasingly sophisticated software defined modulation methods. The challenges presented by encoding, modulation, signal conditioning, timing, and decision algorithms are non-trivial. Adapting to the impacts of wired and wireless channels adds further complexity.While not comprehensive on the subject of communications, this text serves to introduce the practical concepts of binary communications, modulation methods, the digital signal processor (DSP), and software defined radio (SDR). The practical nature of this work is demonstrated through Matlab®simulation of quadrature phase shift key (QPSK) transmitter and receiver algorithms. The algorithms utilize automated controls for gain, I/Q constellation de-rotation, and symbol synchronization. The functionality of these algorithms is then verified on a modern floating point processor in a real-time implementation.This thesis can serve as a starting reference for any similar real world implementation of digital modulation schemes, such as OFDM or 16QAM. In addition, this document demonstrates detailed analysis of the functionality required to enable robust QPSK transmission and reception.