Ambiguity Functions of Zadoff-Chu Signals for 5-G Synchronization Systems

Orthogonal frequency division multiplexing (OFDM) technique has been widely adopted in wireless systems, but it is known for being sensitive to synchronization errors. In this paper we present the method of the spread spectrum signals generating, in which as the pseudo-random baseband sequence are used the complex-valued Zadoff-Chu sequences, which have good correlation properties. For these signals the results of the study are the local properties of the two-dimensional ambiquity functions in the time-frequency plane. These functions define important characteristics of radio systems (resolution in time and frequency, interference in multiple access systems with code division of subscribers, interchannel interference with frequency division of signals, accuracy of estimating the time delay of signals and frequency offset carrier wave, etc.). It is shown that the two-dimensional ambiguity function of these signals have a periodic structure, whose parameters are to be considered in the analysis of the quality of the LTE 5G synchronization systems.