In the advanced T-DMB (AT-DMB) system, the performance of the base layer is affected by both modulation noise and a demodulation method. The amount of modulation noise is determined by the hierarchy parameter of the transmitter, and thus it is not controllable at the receiver. On the other hand, a demodulation method for the base layer can be freely selected by the designer and it dominates the performance of the base layer. This paper focuses on the performance analysis of the base layer in the AT-DMB system according to the choice of a demodulation method and provides useful information for designing receivers for the AT-DMB system.