01-10-2012, 10:35 AM
Adaptive Guard Channel based CAC scheme in a 3G-WLAN
Integrated Network
Adaptive Guard Channel.pdf (Size: 85.05 KB / Downloads: 19)
ABSTRACT
In wireless networks, guard channel based Call Admission Control (CAC) schemes are widely
used to protect handoff calls for seamless wireless services. However, the introduction of the
guard channels in wireless networks results in the increases in the new call blocking probability.
This general situation also occurs in a 3G-WLAN integrated network. To solve this problem in
a 3G-WLAN integrated network for QoS support, we propose an adaptive guard channel based
Call Admission Control (CAC) scheme in this paper. The main objective of our guard channel
based CAC scheme is to alleviate the increase in the new call blocking probability due to guard
channels while it can still protect the handoff calls. For the design of our adaptive guard channel
based CAC scheme, we first develop and analyze a performance model for a general guard
channel based CAC scheme based on a non-homogeneous quasi birth and death model. The
analytic results are used to design our adaptive guard channel based CAC scheme. Numerical
studies show that our adaptive guard channel based CAC scheme can achieve its objective.
INTRODUCTION
In the current wireless networks, heterogeneous wireless networks coexist such as wireless
cellular networks, wireless Local Area Networks (WLAN), wireless mesh networks, etc. Since
each wireless network has its own advantages and disadvantages in spectral efficiency and mobility,
the integration of heterogeneous networks can provide more efficient wireless services to
mobile terminals (MTs) [1]. For this reason, many recent studies are focusing on the integration
of heterogeneous networks, e.g., WiMAX-WLAN [2,3] and 3G-WLAN [4–8].
In this paper, we consider a 3G-WLAN integrated network. As explained in [6,22], 3G cellular
networks and WLAN have their own advantages and disadvantages. A cellular network
guarantees a broad coverage area but provides low speed services at high cost. On the contrary,
the access point (AP) of WLAN provides high speed services at low cost but has a geographically
small coverage area.
The coverage area of a base station (BS) is usually called a cell. Since the coverage area by
an AP of WLAN is smaller than the coverage area of the BS, several APs are usually contained
in a cell. For later use, we call the coverage area of APs the WLAN area. The remainder area
of the cell is called the Cellular area. So, a cell consists of two kinds of technology areas, i.e.,
the cellular area and the WLAN area. In the 3G-WLAN integrated network considered in this
paper, the operation of the network is performed as follows. When an MT is located in the
WLAN area, the MT is serviced through an AP of the WLAN area. When the MT is located in
the cellular area, the MT is serviced by the BS of the cellular area.
In the 3G-WLAN integrated network, we have two types of handoff calls. The first type
handoff calls are called horizontal handoff (HHO), which hand off from one cell to its adjacent
cell. On the other hand, the second type handoff calls are called vertical handoff (VHO) [9,10],
which hand off one technology area to the other technology area. Note that we consider two
technology areas - the cellular area and the WLAN area in this paper. In addition, VHO is a new
factor to be added up in the integrated network. Due to VHO calls, the available radio resource
changes more frequently in time in the integrated network than in homogeneous network because
a VHO attempt results in some changes in the available radio resource of the BS and the
available radio resource of the AP.