  A general method for constructing convolutional codes from units in Laurent
series over matrix rings is presented. Using group ring as matrix rings, this
forms a basis for in-depth exploration of convolutional codes from group ring
encoding, wherein the ring in the group ring is itself a group ring. The method
is used to algebraically construct series of convolutional codes. Algebraic
methods are used to compute free distances and to construct convolutional codes
to prescribed distances.
