In this paper we propose three new packet delay estimators for an adaptive, delay-bounded HPD (DBHPD) scheduling algorithm in the DiffServ context: simple Exponential Weighted Moving Average (EWMA) estimator, EWMA estimator with restart (EWMA-r) and EWMA based on proportional error of the estimate (EWMA-pe). We compare these estimators with the original, simple sum estimator with ns2-simulations using several traffic mixes. We show that the simple sum and EWMA estimators often lead to false scheduling decisions. On the other hand, the EWMA-r and especially the EWMA-pe estimator provide good estimates of the packet delay regardless of the traffic mix.