07-09-2013, 02:10 PM
Energy Optimization Mechanism for Mobile Terminals using Vertical Handoff between WLAN and CDMA2000 Networks
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Abstract
This paper presents energy optimization mechanism for mobile terminals
(MTs) using vertical handoff between Wireless LAN (WLAN) and
CDMA2000 networks. Several techniques for optimizing the power
consumption of MTs have been considered in literature. Some of these
techniques could be used separately or in tandem. Considering the importance
of efficient energy management for MTs, the research in this area could be
taken a step further. The technique considered in this paper allows a
multimode terminal to take advantage of two integrated networks to
efficiently manage its energy consumption. Two integrated networks
considered are WLAN and CDMA2000. This paper develops an algorithm
that allows the MT to always get connected to the most cost-effective
network. The results obtained showed that the MTs power is more efficiently
managed when the MT is using the integrated networks than when it is using
each of the networks independently.
Introduction
In recent times, the use of Internet has allowed users ease of communication access at
anywhere at any time. There are also emerging voice and data networks, each requiring
mobile access devices. The need for users to take advantage of the various access networks
without carrying about multiple terminals has lead to the development of multimode
terminals. Most popular types of these multimode terminals presently are those that can
access wireless LAN (WLAN) and CDMA2000 networks. Also, the users’ desire to be
always best connected anytime, anywhere, with any device has fuelled the research on
network integration. Network integration has been shown to have good prospects to both
users and network providers alike.
The release of the IEEE 802.11 WLAN standards in 1997 gave rise to a number of
other related standards which form the 802.11 family of standards. These standards were
made to facilitate the interoperability of WLANs, and allow for the introduction of several
new services. One of these services introduced is the public wireless access data networks
more commonly known as “hot-spots”. The great success and massive recent deployment of
WLAN technology indicates that these networks will play an important role in the
development of the 4G networks [1]. To achieve the dream of universal mobile
telecommunications as specified by the international telecommunications union (ITU), it is
necessary to integrate WLAN and CDMA2000 cellular networks. The Internet certainly, will
be used to support this integration because it has become the main thrust of network
integration between complementary heterogeneous networks.
Description of the Optimization Method
In this section, we present the proposed energy optimization model that makes use of
vertical handoff to support the optimization of MT’s power consumption without network
degradation. This is an algorithm that makes the MT to select the best network (CDMA2000
or WLAN) in terms of power consumption rate of their network interface card (NIC)
respectively at a time without reduction in QoS. Before the MT enters a given state, the
decision model computes the energy consumption for each NIC with respect to that state. The
decision on what interface to be selected is based on the outcome of the computation. The
interface with lower power consumption rate is activated while the other is deactivated. NICs
generally can be in any one three conditions (Uploading or transmitting, downloading or
receiving and idle or redundant mode) when activated. Table 1 shows the power consumption
requirements of two NICs (CDMA1x wireless modem and Orinoco IEEE802.11b wireless
LAN modem) as reported in [6, 7] used as a case study in this paper.
Performance Evaluation
This section presents the effect of the power optimization algorithm on MT power
consumption. Several data downloads from the Internet were made using the three different
states (Idle, Download and Upload) a MT could be in a time. In each case, we estimated the
time required to perform the requested service was estimated. This is denoted as service time
(t) in seconds. Let Idle state, Download state and Upload state be denoted by ID, DL and UP
respectively. In addition, User Preference (u).
Conclusion and Future Works
This paper proposed an energy optimisation mechanism for MT using VHO between
WLAN and CDMA2000 network. We designed an algorithm that could provide efficient
power management in MTs without network degradation. The power consumption rates of the
two popular NICs, one for each network, were used to carry out this work. The result shows
that our proposed mechanism performs considerably well. The benefits of the two
complementary heterogeneous networks have also been discussed. There are, however other
issues that are not addressed in this paper such as network QoS, network security, handoff
latency etc. These could be considered as future works in this area.