I-Q diagram utilization in a novel modulation classification technique for cognitive radio applications

Abstract

We report here on the utilization of signal in-phase-quadrature (I-Q) diagrams in a novel modulation classification (MC) technique. This MC technique is able to classify linear digital single-carrier modulations as well as multi-carrier modulations. The method uses the waveforms' I-Q diagrams and, by employing a combination of k-center and k-means algorithms, determines the type of modulation. Implementation and refinement of the novel single-carrier modulation classification technique using the I-Q diagrams are discussed in detail. Further, a model for classification of multi-carrier signals is presented, including Gaussianity, cyclostationarity, and autocorrelation tests for further extracting orthogonal frequency division multiplexing signal parameters. Finally, results of this method are presented and compared to other classification methods, and the considerations for implementing the method in hardware are briefly discussed. As a future direction of this research, the performance of the algorithm in fading channels is an interesting topic to pursue.

Automatic modulation classification technique for radio monitoring

“…The variable z ik is the membership indicator, which is equal to unity, if the input data x i belongs to the cluster k and zero otherwise. The membership indicator z ik is calculated based on the shortest distance of the input data x i to the prototypes P K given in (2), where w i represents the index k of the winning prototype P k for the input data…”

“…The 'K-means' algorithm iteratively solves the clustering problem stated in (2) by alternating between a competitive and a learning step. In the competitive step, the allocation of the input symbols x i to the prototypes P K is carried out in such a way that J in (1) is minimised.…”

“…Simulation: The performance of the proposed HCPM algorithm with the utility function F = F 2 1 F 2 was tested in a simulation for a candidate pool M S,K of the following modulation schemes: 4 quadrature amplitude modulation (QAM), 16 QAM, 32 QAM, 64 QAM, binary phase shift keying (PSK), 4 PSK, 8 PSK and 16 PSK. The simulation did not include any effects (frequency offset, phase offset and so on) that have to be solved in the preprocessing block.…”

“…2. The SNR for the detection rate of 1 in the defined test setup for QAM are summarised in Table 1 and compared with the results of the ‘two threshold sequential algorithmic scheme (TTSAS)’ and ‘fuzzy’ algorithm in [3] and the ‘K‐centre’ algorithm in [2]. The SNR in this Letter is defined as E s / N 0 , where E s is the energy per symbol and N 0 is the power spectral density of the Gaussian noise.…”

“…To our best knowledge only a few of these algorithms are implemented in a real system and most of the presented evaluations in the literature are limited to simulated data only. In [2], a combination of the 'K-means' and 'K-centre' algorithms is used for AMC and the standard deviation of the calculated prototypes is used for the AMC decision. In [3], a fuzzy 'K-means' algorithm is implemented and the AMC decision is based on a Hamming neural network.…”