Available Bandwidth estimation is one of the major problems in multimedia and real time data transmission. To enhance the performance of MANETs, an efficient management is needed in sharing the available bandwidth among multiple users. Existing probing techniques creates extra traffic in the resource constrained network. To overcome this, the proposed bandwidth estimation LP-ABE involves a passive technique to improve its accuracy in estimating the bandwidth by considering the random factors such as retransmission time, link capacity along with link expiration time. The implemented results show the improved performance in the estimation of bandwidth for LP-ABE compared to the existing method. Keywords: Available Bandwidth, Channel Capacity, Link Expiration Time, QoS, Transmission Time.