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A heterogeneous wireless network supporting multihoming gives multi-mode terminals the flexibility to be simultaneously connected to more than one radio access technologies (RATs). Existing joint call admission control (JCAC) algorithms designed for heterogeneous wireless networks block or drop an incoming call when none of the available individual RATs in the heterogeneous network has enough bandwidth to support the incoming call. Consequently, high bandwidth-demanding calls can easily be blocked or dropped in the network, especially during the peak hours. In order to reduce this problem of call blocking/dropping, this paper proposes a JCAC algorithm that selects multiple RATs for an incoming call when none of the available individual RATs has enough bbu to accommodate the incoming call. Selection of multiple RATs for an incoming call entails that the packet stream of the incoming call will be split among the selected RATs. The aim of the proposed JCAC algorithm is to admit an incoming call (that cannot be admitted into any of the available single RATs because of high load in the RATs) into two or more RATs. The residual bandwidths in the selected RATs are combined to support the incoming call, and the packet stream of the call is split among the selected RATs, thereby reducing call blocking/dropping probability. At the receiver, the split packet streams are then combined. An analytical model is developed for the proposed JCAC algorithm, and its performance is evaluated in terms of call blocking/dropping probability. Simulation results show that the JCAC algorithm reduces call blocking/dropping probability in heterogeneous wireless networks supporting multihoming.