Classification of OQPSK-Type Signals by Detecting Offset-Timing between I/Q Samples

It is seldom discussed how to classify OQPSK-type signal (MSK, OQPSK or pi/2BPSK; and other digital quadrature modulation (QPSK and 16QAM). A new algorithm called C-DOT (classifier on detecting offset-timing) is provided in this paper to resolve this problem. The spectrum of carrier-synchronized signal's SST (symmetric square transform) is constructed firstly. The maximal bin of its nonlinear filtered version is taken as a test variable then. If test variable is greater than a well-chosen threshold, the received signal can be claimed one of the OQPSK-type signal. The Monte Carlo simulation indicates the new algorithm is a competent preliminary classifier for further discrimination