Exploiting mobility patterns for inter-technology handover in mobile environments
Yanmin Zhu
a,b,
⇑
, Lei Ni
a,b
,BoLi
c
a
Shanghai Key Lab of Scalable Computing and Systems, Shanghai, China
b
Department of Computer Science and Engineering, Shanghai Jiao Tong University, Shanghai, China
c
Hong Kong University of Science and Technology, China
article info
Article history:
Received 21 December 2011
Received in revised form 19 July 2012
Accepted 26 August 2012
Available online 6 September 2012
Keywords:
Mobility pattern
Handover
Markov decision process
Entropy
Implementation
abstract
Mobile terminals with multi-radio devices have become increasingly prevalent. This makes it possible for
Internet applications to be supported by heterogeneous wireless networks while the terminal is on the
move. As the user is constantly moving, it is highly desirable that the terminal connects to the best net-
work and retains high performance of network connections. Handovers can be made within the same
type of network (horizontal handover) or different types of networks (vertical handover). This paper
focuses on link-layer inter-technology vertical handovers. Vertical handovers present several great chal-
lenges, such as user mobility randomness, high handover overhead and optimality requirement. Existing
work often focuses only on the current network condition when making handover decisions, ignoring
future performance of the terminal. As a result, a handover decision good for the current moment may
soon become poor when the user moves to another place. This paper is motivated by the observation that
users in a given mobile environment, such as university or enterprise campus, exhibit clear mobility pat-
terns. We propose an approach for making handover decisions, which explicitly exploits user mobility
patterns. This approach can produce high-performance handover decisions in the long run. Employing
a comprehensive framework for preference customization, the approach supports user customization
caring for different user preferences. Extensive real trace driven simulations and comparative study show
our algorithm is better than the conventional vertical handover algorithms.
2012 Elsevier B.V. All rights reserved.
1. Introduction
Recent years have witnessed the boom of different wireless
technologies including WiFi, WiMAX, 3G and LTE [4]. It has become
increasingly prevalent for mobile terminals, such as notebook, PDA
and smart phones, which are equipped with multi-radio devices.
As a user is moving in an environment with heterogeneous wire-
less access technologies, the terminal can connect to different net-
work access points [14]. The IEEE 802.21 working group has been
working towards the standardization of Media Independent Hand-
over (MIH) [5], i.e., towards seamless handover between IEEE 802
and non-IEEE 802 (e.g., 3GPP, 3GPP2) access technologies. It will
become possible for users to roam among different wireless net-
works by integrating various wireless access networks with the
help of network-layer (IP) mobility management architectures
[12], such as Mobile IP [2], Mobile IPv6 [3] and Proxy Mobile
IPv6 [1]. By actively switching among different wireless networks,
the user may be able to experience better network connection
performance [6].
Traditionally, a horizontal handover is made when there is only
one type of wireless network, with the user changing from one net-
work attachment point to another in the same network. When
there are over two types of wireless networks, not only horizontal
handover but also vertical handover is possible. A vertical hand-
over is made when the mobile terminal migrates across different
wireless networks. It usually involves three major phases: i.e., sys-
tem discovery, vertical handover decision and vertical handover
execution [15]. In the system discovery phase, the mobile terminal
periodically senses its current network condition. The network
condition may include many dynamic parameters, such as network
feasibility, available bandwidth, delay, jitter, and coverage. In a
wireless environment, the network condition of a mobile terminal
is largely determined by the location of the user. In the vertical
handover decision phase, a base station or access point selection
should be made with the objective of maximizing the connection
performance of the user. In the last phase, the vertical handover
decision is executed and the terminal connects to the selected base
station. A typical execution process includes authentication, asso-
ciation, transfer of the context information, and update of wired
network routers. This process may introduce handover cost, such
as delay and interruption to ongoing sessions.
This paper focuses on link-layer inter-technology handovers.
More specifically, we study vertical handover decisions in a
0140-3664/$ - see front matter 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.comcom.2012.08.016
⇑
Corresponding author at: Department of Computer Science and Engineering,
Shanghai Jiao Tong University, Shanghai, China. Tel.: +86 34205120 210.
E-mail addresses: yzhu@sjtu.edu.cn, yzhu@cs.sjtu.edu.cn (Y. Zhu), nilei@sjtu.
edu.cn (L. Ni), bli@cse.ust.hk (B. Li).
Computer Communications 36 (2013) 203–210
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Computer Communications
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