Vertical handover mechanism is an important issue in heterogeneous wireless networks. Continuity of service during handover and QoS are relevant issues to deal with. This paper focuses on vertical handover decision making. It proposes a Rank Average method for the best access network selection. This method is an aggregation of two Multi Attributes Decision Making (MADM) methods: Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and VIse Kriterijumska Optimizacija kompromisno Resenja (VIKOR), together with Shannon entropy-based weights. Entropy is an adequate tool to weigh up the handover criteria in a quiet easy and straightforward way. Rank Average outperforms TOPSIS and VIKOR in terms of throughput, end to end delay, packet loss, and significantly reduces the number of unnecessary handovers related to the ping-pong effects. Performance results are obtained within the scope of MIH through NS3 simulator.