Assessment of the algorithm for optimum coherent reception of OFDM signals with multi­position amplitude­phase modulation

Abstract

The paper examines the issues of optimal coherent reception of OFDM signals with multi-position amplitude-phase modulation in conditions of a priori uncertainty of the state of the telecommunications network. It was determined that modern telecommunication systems, due to the complexity of the system’s behavior caused by the nature of random external influences, require invariant procedures for optimal reception and processing of the input signal. The paper considers the procedure for ranking input readings, which turns them into a sequence of integers — ranks that depend on the relative level of this reading among the observed set, which has the widest range of invariant properties. Based on it, algorithms for optimal coherent reception of OFDM signals with multi-position amplitude-phase modulation were developed and proposed. The proposed algorithms solve the problem of coherent reception of a multiposition AFM signal both in the presence of a special sync signal and in the absence of it. At the same time, the reception and processing of a coherent signal according to the proposed algorithm in the presence of a sync signal consists in the fact that the averaging is carried out on the interval of the sync signal. And in the case of reception without the presence of a synchronization signal — in the corresponding algorithm, averaging is carried out on a continuous interval of N parcels preceding the parcel that is being processed at the moment. Approbation of the proposed algorithms was carried out on the basis of coherent processing of 16-position OFDM signals with amplitude-phase modulation. The considered algorithms for coherent processing of multi-position AFM or AFRM signals are especially convenient for multi-channel (multi-frequency) systems with orthogonal channel signals, because in these systems the same procedure is used for the distribution of orthogonal signals, the calculation of the projections of the received signal on two mutually orthogonal oscillations with an arbitrary initial phase.