A spectral analysis of anisotropic magnetohydrodynamic turbulence, in presence of a constant magnetic field, is presented using high-resolution direct numerical simulations. A method of decomposing the spectral space into ring structures is presented and the energy transfers between such rings are studied. This decomposition method takes into account the angular dependency of energy transfers in anisotropic systems, while it allows one to recover easily the known shell-to-shell energy transfers in the limit of isotropic turbulence. For large values of the constant magnetic field, the total-energy transfer appears to be most dominant in the direction perpendicular to the mean magnetic field. The linear transfer due to the constant magnetic also appears to be important in redistributing the energy between the velocity and the magnetic fields.