In order to calculate the worst-case link delays in the EDD (Earliest Due Date) connection admission control scheme, a check called the point schedulability check is necessary for each of finite and discrete time in stants (checkpoints). In our previous calculation method, high speed calculation is attained by decreasing a upper bound value of checkpoints. However, the method can not calculate at high speed when networks are temporarily in congested state. The purpose of the paper is to improve the previous method. The upper bound value of the previous method depends on the slope and the intercept of a linear function called a covering function, and its value drastically increases for the small increase of the slope and slowly increases for the small increase of the intercept. Because the previous method uses a covering function whose slope is large in the temporal congested state, the calculation time becomes large. The improved method uses a covering function whose slope is minimum and whose intercept somewhat larger than the previous method, and consequently the upper bound value of checkpoints become smaller. The improved method therefore can attain high speed calculation in the temporal congested state. Numerical examples show that the improved method drastically decrease the calculation time in the temporal congested state.
