Generalized Relativistic Kinematics

We propose a method for deforming an extended Galilei algebra that leads to a nonstandard realization of the Poincar'e group with the Fock-Lorentz linear fractional transformations. The invariant parameter in these transformations has the dimension of length. Combining this deformation with the standard one (with an invariant velocity $c$) leads to the algebra of the symmetry group of the anti-de Sitter space in Beltrami coordinates. In this case, the action for free point particles contains the dimensional constants $R$ and $c$. The limit transitions lead to the ordinary ($R\to \mathrm{\infty }$) or alternative ($c\to \mathrm{\infty }$) but nevertheless relativistic kinematics.