  Wireless access technologies have been extensively developed aiming to give
users the ability to connect to their expected networks anytime, anywhere. This
leads to an increment of the number of wireless interfaces integrated into a
single mobile device, hence, it allows the device to be able to connect to
multiple access networks. However, in some specific cases such as natural
disasters, having an uncorrupted and timely information exchanging means is
critical for affected victims to survive or to connect to the outside world.
This is because the essential network infrastructures in these cases could be
destroyed causing a large number of systems to stop working. In that cases, the
victims need a heterogeneous communications network in which they can
communicate, without a doubt, by using different wireless access technologies,
i.e., Bluetooth or Wi-Fi. The network must also be able to smoothly change the
access technologies, or called a vertical handover, to ensure QoS for ongoing
applications. In addition, the network must have a mechanism to save energy.
For hese reasons, an SDN approach, which has been proposed in a previous work,
is considered. The performance of the system has been validated by a set of
experiments in a real testbed. The obtained results show that the proposed
vertical handover can save at least 24.42 per cent of the energy consumed by
the wireless communication. The handover delay with different UDP traffic is
less than 150ms. Moreover, the network allows a device using Bluetooth to talk
with another one using Wi-Fi over a heterogeneous connection where the
end-to-end jitter is mainly below 20ms and the packet loss rate is as small as
0.2 per cent.
