International Journal of Signal Processing, Image Processing and Pattern Recognition
Vol.9, No.2 (2016), pp.127-134
http://dx.doi.org/10.14257/ijsip.2016.9.2.11
ISSN: 2005-4254 IJSIP
Copyright ⓒ 2016 SERSC
Identifying of Digital Signals Based on Manifold Learning
Qingbo Ji
1
, Boyang Feng
1
, Yun Lin
1*
, Zheng Dou
1*
, Zhiqiang Wu
2
and Zhiping Zhang
2
1
College of Information and Communication Engineering
Harbin Engineering University, Harbin, China
linyun@hrbeu.edu.cn
2
Department of Electrical Engineering
Wright State University, Dayton, Ohio, U.S.
zhiqiang.wu@wright.edu
Abstract
Modulation type is one of the most important characteristics used in signal recognition.
An algorithm to realize signal modulation identification is proposed in this paper. We
applied wavelet transformation and STFT to the signal, and then used manifold learning
method to reduce the high dimension and extracted the recognition feature. The proper
threshold value was set as the classifier to achieve the purpose of recognizing 4 kinds of
signals (MASK, MFSK, MPSK,QAM) in Gauss white noise environment. The algorithm
requires priori signal information no other than signal-to-noise rate. Simulation result
indicates the algorithm achieves good performance.
Keywords: Digital signals identification, Feature extraction, Manifold learning
method, Isomap
1. Introduction
Digital signals are widely used both in commercial and military fields. To analysis the
information transferred by the source, the signal mode needs to be figured out by
selecting the appropriate features. Feature selection is the process of choosing a subset of
the original predictive variables by eliminating redundant and uninformative ones. By
extracting as much information as possible from a given data set while using the smallest
number of features, we can save significant computing time and often build models that
generalize better to unseen points.
Among all the signal parameters, in-pulse characteristics have very special effects.
Many in-pulse characteristics have been used on signal recognition such as entropy
analysis, short time Fourier transformation, wavelet transformation, complexity feature
and so on. For example, Swami and Sadler [3] proposed a wavelet transform-based signal
identification method, with which the success rate of 98% at signal-to-noise ratio (SNR) 4
dB was reported. Zhang [4] proposed a support vector machine-based classifier to
classify the signals according to the proposed features. The types of the signals have been
identified with a success rate of about 90% for 0<SNR<5 dB. A digital modulation
classification system was proposed by Xu et al. [5] for CR using only temporal waveform
features. They reported a success rate of 95% at SNRs ranging from 10 to 80 dB. In [6],
the authors presented a high-performance multi-layer perception neural network with
resilient back propagation learning algorithm. In [7], a signal classification approach
based on neural network ensembles was proposed, which enables dynamic spectrum
access. From the research works mentioned above, it can be found that: (a) most of the
proposed methods can only recognise low-order and limited digital signals; (b) most of
*
Corresponding Author