RF Analog Impairments Modeling for Communication Systems Simulation: Application to OFDM-based Transceivers

4.1 Introduction

With the ever-escalating demand for high-data rates for end-users, in addition to the use of larger frequency bandwidths, new wireless communication systems also specify higher order modulation, such as 64-QAM in mobile WiMAX and 3GPP-LTE, which necessitate high SNR in order to be properly demodulated. Consequently, these new high data-rate systems are particularly sensitive to the RF analog front-end impairments that are difficult to avoid in low-cost low-power transceivers integrated in deep sub-micrometer CMOS technology. Instead of trying to improve the RF analog blocks, which is neither cost nor power efficient, today the new trend in communication systems design is to accept increased RF analog front-end impairments, called dirty RF (Fettweis et al., 2007), and to compensate the resulting errors in digital with advanced signal processing (Horlin and Bourdoux, 2008; Schenk, 2008).

In Chapters 2 and 3 we have described and simulated the major inevitable RF analog impairments we encounter in any practical communication system. These impairments are phase noise, mixer I and Q mismatch, amplifier nonlinearities, DAC and ADC clipping, sampling jitter, and carrier and SFOs). The aim was to analyze their impact on system performance with a special emphasis on OFDM modulation, which is widely used in modern communication standards (IEEE 802.11 a/g/n, 3GPP-LTE, Mobile WiMAX). We have seen that these impairments can severely degrade the link performance by generating ...