  In this paper, we present an error-trellis construction for tailbiting
convolutional codes. A tailbiting error-trellis is characterized by the
condition that the syndrome former starts and ends in the same state. We
clarify the correspondence between code subtrellises in the tailbiting
code-trellis and error subtrellises in the tailbiting error-trellis. Also, we
present a construction of tailbiting backward error-trellises. Moreover, we
obtain the scalar parity-check matrix for a tailbiting convolutional code. The
proposed construction is based on the adjoint-obvious realization of a syndrome
former and its behavior is fully used in the discussion.
