978-1-7281-1536-8/18/$31.00 ©2018 IEEE 45
A NOVEL AUTOMATIC MODULATION CLASSIFICATION FOR M-QAM
SIGNALS USING ADAPTIVE FUZZY CLUSTERING MODEL
GUO-YU ZHANG
1
, XIAO YAN
1
, SHI-HAO WANG
2
, QIAN WANG
1
1
School of Aeronautics and Astronautics, University of Electronic Science and Technology of China,
Chengdu 611731, China
2
School of Information and Communication Engineering, University of Electronic Science and Technology of China,
Chengdu 611731, China
E-MAIL: zhangguoyu@std.uestc.edu.cn, yanxiao@uestc.edu.cn
Abstract:
An automatic modulation classification (AMC) method
for M-ary Quadrature Amplitude Modulation (M-QAM)
signals using adaptive fuzzy clustering model is presented. In
the proposed framework, the neighborhood radius of
subtractive clustering algorithm is emphatically researched to
satisfy different modulation orders. An adaptive construction
mechanism of neighborhood radius is designed according to
the amplitude component of M-QAM signals. Euclidean
distance of the clustering center numbers between test signal
and standard signals are utilized to identify the modulation
types. Monte Carlo simulation results and theoretical analysis
demonstrate that the proposed AMC method can provide
promising performance.
Keywords:
Modulation classification; M-ary quadrature Amplitude
modulation (M-QAM); Subtractive clustering; Adaptive
neighborhood radius; Euclidean distance
1. Introduction
Automatic modulation classification (AMC), which
can classify the modulation schemes automatically, is an
indispensable step between signal detection and
demodulation. Since the received signals usually lack priori
knowledge, AMC plays an important role in the field of
non-cooperative communication, including military and
civilian areas, such as electronic reconnaissance,
communication confrontation, electronic warfare and
cognitive radio [1-2]. Nowadays, the increasingly complex
communication environments require a more efficient
utilization of spectrum resources which is already limited
and almost fully occupied. High-order Quadrature
Amplitude Modulation (QAM), because of its high
spectrum efficiency, is wildly used in many fields such as
intelligent communication, satellite communication and
microwave communication etc. Thus the research on AMC
for M-QAM signals is of significant value.
Classical AMC methods are generally divided into two
categories, the Likelihood-based (LB) approach and the
Feature-based (FB) approach [3]. In terms of M-QAM
signals, the FB approach is more frequently employed for
its low computational complexity and suboptimal results.
Among FB approaches, constellation shape is a commonly
used feature, existing constellation reconstruction method
in previous work including subtractive clustering analysis
[4], K-means clustering analysis [5] and density spectrum
based approach [6] etc. Among constellation reconstruction
methods mentioned above, subtractive clustering is a
simple but effective solution: (i) an initial clustering center
number is not required; (ii) the number of clustering centers
is equal to modulation order for noise-free signals in theory.
However, the neighborhood radius (hereinafter referred to
as radius) which is essential for clustering accuracy, is short
of detailed and unambiguous description of how it is valued
in previous work.
In this paper, we propose a novel AMC algorithm for
M-QAM signal via adaptive fuzzy clustering model. The
rest of this paper is organized as following. Section 2 is
background knowledge which describe the subtractive
clustering theory. In section 3, the proposed AMC algorithm
including the adaptive construction mechanism of the
clustering radius is discussed in detail. In section 4, Monte
Carlo simulation experiments are carried out to investigate
the effectiveness of our proposed work, the comparison
results are shown in the figures. And the last section is
conclusion.
2. Background
The most significant feature of M-QAM is that the
constellation shape strongly depends on modulation order.
As the modulation order increases, the number of