Alireza Bagheri Salec - Department of Mathematics, Faculty of Science, University of Qom, Qom, Iran.
Seyyed Mohammad Tabatabaie - Department of Mathematics, Faculty of Science, University of Qom, Qom, Iran.
Javad Saadatmandan - Department of Mathematics, Faculty of Science, University of Qom, Qom, Iran.

In this paper, we introduce admissible vectors of covariant representations of a dynamical system which are extensions of the usual ones, and compare them with each other. Also, we give some sufficient conditions for a vector to be admissible vector of a covariant pair of a dynamical system.  In addition, we show the existence of Parseval frames for some special subspaces of $L^2(G)$ related to a uniform lattice of $G$.

Admissible vector, Covariant representation, Dynamical system