Application Layer Multicast (ALM) is highly expected to be the new technological choice contents delivery in lieu of IP multicast Depending on each node's streaming application, ALM constructs multicast trees and delivers the stream through those trees. The problem of ALM is that when a node resides in tree leaves, the stream cannot be delivered to descendant nodes. To overcome this problem, Topology-aware Hierarchical Arrangement Graph (THAG) was proposed. By employing Multiple Description Coding (MDC), THAG first splits the stream into a number of sub-streams, and then uses Arrangement Graph (AG) to construct an independent tree for each sub-stream. However, using the same size of AG in THAG has a difficulty delivering a stream appropriately across a heterogeneous network. In this paper, we propose a method to change the size of AG dynamically in enhancing THAG performance well even in a heterogeneous network. Finally, we evaluate the proposed scheme by experiments in ns-2. By comparing with THAG, we show that our proposal scheme provides a better performance in throughput and Bandwidth Satisfaction Rate (BSR).