Selective call-dropping and bandwidth adaptation for reducing multiple-call handoff dropping

Small cells such as femto cells are commonly being deployed for traffic offloading in heterogeneous wireless networks (HetNet), and multimode terminals designed for HetNets have the capability to simultaneously support two or more different classes of calls. A user having a multimode terminal with multiple ongoing calls that are connected through a femto cell may experience necessary handoff when the user moves outside the coverage area of the femto cell in a HetNet. However, the multiple handoff calls from the multimode terminal may be dropped because none of the available radio access technologies has enough residual capacity to accommodate the multiple handoff calls from the femto cells. In order to reduce the probability of dropping multiple handoff calls in HetNets, this paper proposes a handoff decision scheme that uses selective call dropping and bandwidth adaptation to decrease overall call dropping probability of multiple handoff calls. The proposed scheme uses individual call priority for performing selective call dropping. Performance of the proposed scheme is evaluated and compared for four different scenarios. Results show that the proposed scheme significantly reduces the probability of dropping essential handoff calls in HetNet.