19-06-2013, 01:02 PM
TAKEOVER: A New Vertical Handover Concept for Next-Generation Heterogeneous Networks
Next-Generation Heterogeneous.pdf (Size: 249.09 KB / Downloads: 22)
Abstract
One of the major challenges for seamless mobility
in next-generation heterogeneous networks is vertical handover,
which is the process of maintaining a mobile user’s active
connections as it changes its point of attachment. For seamless
vertical handover, we introduce a new concept, Takeover, which
enables a neighbor node to process requests of a mobile node. We
develop protocol and operation for the takeover and apply it to
vertical handover for next-generation heterogeneous networks.
The proposed handover scheme using the takeover protocol
reduces average handover latency and so enables a fast and
seamless handover between two different access technologies. The
simulation results show that the takeover-based vertical handover
scheme achieves better performances compared with conventional
handover schemes, with respect to handover delay, packet loss,
and power consumption.
INTRODUCTION
Next-generation communication requires universal wireless
access and ubiquitous computing through seamless personal
and terminal mobility. One of the major challenges for seamless
mobility is vertical handover, which is the process of
maintaining a mobile user’s active connections as it moves
between different types of network. In order to achieve seamless
vertical handover in heterogeneous network environments,
it is necessary to guarantee service continuity and quality-ofservice
(QoS), which means low latency and low packet loss
during handover [1].
Generally, conventional handover schemes have been proposed
by using pre-registration or post-registration method,
which can reduce the handover delay because they separate
layer 2 (L2) and L3 handovers and perform the L3 handover
earlier or later than the L2 handover [2]. However, these
scheme can not be applied in heterogeneous network environments
without modification, because they need pre-defined
signaling between two access nodes involved in handover.
Moreover, current pre-registration or post-registration schemes
consider only registration process during handover, and so it
is difficult to apply conventional schemes to the handover
between heterogeneous networks.
TAKEOVER PROTOCOL
Takeover happens between two MNs that can communicate
each other. Fig. 1 shows the basic operation of takeover
protocol in which MN tries to request a takeover to NN.
Takeover operation consists of four phases: neighbor node
discovery, takeover initiation, takeover process, and takeover
completion phases.
PROPOSED VERTICAL HANDOVER SCHEME
We apply the takeover protocol to vertical handover scheme
in heterogeneous network environments. Fig. 2 and 3 illustrate
operation and signaling procedure for the proposed vertical
handover based on takeover protocol, respectively.
First, an MN that hands over from old AN (oAN) to new
AN (nAN) decides to start handover or takeover based on
signal strength from two ANs. If the MN wants to initiate the
takeover process, it broadcasts Ready-to-Takeover message to
search a suitable NN which can help the MN during vertical
handover period. The Ready-to-Takeover message contains
MN’s address, aim of the takeover, and identity of the nAN
where the MN wants to move.
SIMULATION RESULTS
Simulation Environments
To evaluate the performances of proposed vertical handover
scheme, we carry out computer simulation [3]. Table I shows
parameters used for simulation. The radius of an AN is 1km
and the radius of MN is 100m, which means maximum
distance that two MNs can communicate each other. The
number of AN is unlimited and all ANs are placed to satisfy
that distance between adjacent two ANs .
CONCLUSIONS
For seamless vertical handover, we introduce a new concept,
takeover, which enables an NN to process requests of an
MN. We develop protocol and operation for the takeover and
apply it to vertical handover for next-generation heterogeneous
networks. The simulation results show that the takeoverbased
vertical handover scheme achieves faster and seamless
handover compared with conventional handover schemes without
the takeover. Therefore, our proposed vertical handover
scheme guarantees seamless mobility and service continuity by
using a novel concept of takeover in heterogeneous networks.
This takeover concept is also applicable to various situations
in which an MN is restricted by its coverage, battery power,
resource, and so on.