Abstract
Modulation identification, a major task of intelligent receivers, is of vital importance for applications in military and civilian fields. In this work, we develop and analyze a blind modulation identification algorithm for two-path successive relaying systems. Analytical expressions for the correlation functions adopted as the basis of the proposed algorithm are derived, and the computational cost of the algorithm is addressed. By taking advantage of the space-time redundancy, we mathematically prove that a group of modulation types exhibits peaks for specific correlation functions while the other group does not. Exploiting this feature, we propose a binary tree hypothesis test for decision-making. A packet length estimator is also introduced as an auxiliary task for the proposed algorithm. The proposed algorithm does not require information about channel coefficients and noise power. The identification performance of the proposed algorithm is evaluated through Monte Carlo simulations under different conditions. Results show that the performance of the proposed algorithm is remarkably better than the traditional algorithms.