NON LINEAR DISTORTION AND COMPENSATION TECHNIQUE IN WIMAX BROADBAND
Date
2015-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Pulchowk Campus
Abstract
WiMAX (Worldwide Interoperability for Microwave Access) is a wireless
communications standard designed to provide 30 to 40 Mbps data rates. The
physical layer of WiMAX is based on Orthogonal Frequency Division Multiplexing
(OFDM) technique. OFDM is a Frequency Division Multiplexing (FDM) technique
used as a digital multi-carrier modulation method. The major advantages of OFDM
are robustness in multipath fading and high spectral utilization efficiency. However,
it has some serious problem like highly sensitive to timing and frequency offset,
and more specifically Peak-to-Average Power Ratio (PAPR) problem. Since
OFDM is constructive superposition of the subcarriers, it has significant numbers
of large peak resulting in high PAPR causing large fluctuation in input signal which
requires the use of highly linear amplifier. Due to the amplifier imperfection the
peaks are distorted non-linearly which generates inter modulation product causing
both in-band distortion and Out-of-Band (OOB) radiation. The design of a
compensation technique to improve the linearity of the power amplifier is
performed in this thesis work. The adaptive pre-distortion method to compensate
the non-linearity of power amplifier includes the LSE estimation of non-linearity
and pre-distortion techniques. The analysis of Phase Realignment (PR) and
Modified Phase Realignment (MPR) techniques for PAPR reduction for the
performance improvement of the system showed that the combination of predistortion
and PR/MPR technique has superior capability in mitigation of the nonlinear
distortion as compared to the implementation of individual techniques.
Description
WiMAX (Worldwide Interoperability for Microwave Access) is a wireless
communications standard designed to provide 30 to 40 Mbps data rates.
Keywords
OFDM,, WiMAX,, PAPR,, Non-linear distortion,, HPA
Citation
MASTER OF SCIENCE IN INFORMATION AND COMMUNICATION ENGINEERING