Simulation Of Physical Layer Impairments On Communication System

A practical software radio system (SDR) typically suffers from a number of impairments in its migration from a baseband signal at the transmitter to its replication at the receiver. This gives rise to error generation and degradation in overall system performance. Analog impairments at the intermediate frequency (IF) can have many of the same issues as radio frequency (RF) signals and they also include modulator and demodulator mismatches between the I and Q-channels. These RF and analog impairments are not confined to SDR systems but may be found in any digital radio system. The fact that the SDR uses such a large portion of digital logic and direct conversion receiver (DSP) introduces additional impairment concerns that may not be found in a traditional radio design. The digital radio receiver's main function is to extract the variable RF signals in the presence of interferences and transform them into a close replica of the original signal that is the baseband signal. Therefore the main objective of this thesis is to help one understand the impact of measure and visualize implementation impairments related to both the transmitter and the receiver at all stages of a communication system and how they affect the overall accuracy of the system and its effect on the performance. Towards this end a basic communication system was set up with ability to insert and simulate user selectable levels of multiple implementation impairments and software was created to measure and identify the most common impairments in the design and results are presented through constellation plots, eye diagrams and power spectrum.