02-02-2013, 11:44 AM
Call Admission Control for Next Generation Wireless Networks Using
Higher Order Markov Model
Call Admission Control.pdf (Size: 418.91 KB / Downloads: 31)
Abstract
The Next generation wireless networks (NGWN) will be heterogeneous which will have different radio access
technologies (RATs) operating together. The Radio Resource Management (RRM) is one of the key challenges in
NGWN. The Call admission control (CAC) mechanism is one of the Radio Resource Management technique plays
instrumental role in ensuring the desired QoS to the users working on different applications which are having the
diversified nature of QoS requirements to be fulfilled by the wireless networks. One of the key challenges to be
addressed in this prevailing scenario is the distribution of the available channel capacity amongst the multiple traffic
with different bandwidth requirements so as to guarantee the QoS requirements of the traffic .The call blocking
probability is one such QoS parameter for the wireless network and for better QoS it is desirable to reduce the call
blocking probability. In this customary scenario it is highly advantageous to bring about an analytic Performance model.
In this paper we propose a call admission control framework based on higher order Markov chains to effectively handle
the call blocking probability in NGWN and to provide optimal QoS for the mobile users. In the proposed algorithm we
have considered three classes of traffic having different QoS requirements.
Introduction
The recent advances in the wireless networks and mobile devices are inclined towards emerging of ubiquitous
computing where the users and applications running in the mobile terminal (MT) can enjoy seamless roaming. It is well
known that the basic problem in the wireless networks is the scarce of the radio resources. The efficient radio resource
management is very essential. The admission control is one of the radio resource management technique which plays
dominant role in effectively managing the resources. The admission control in the wireless networks will reduce the call
blocking probability in the wireless networks by optimizing the utilization of the available radio resources. The mobile
communication environment is featured by moving terminals with different QoS requirements and in this current
scenario the need of guaranteed QoS is more sought for.
Related Work
At present, dissimilar wireless access networks including 2.5G , 3G , Bluetooth , WLAN and Wi-Max coexist in the
mobile computing environment, where each of these Radio access technologies offer complementary characteristics and
features in terms of its coverage area, data rate, resource utilization , power consumption etc.. With all these there are
constant improvements in the existing technologies offering better performance at lesser cost. This is beneficial in both
the end users and service provider’s perspective. The idea of benefiting from integrating the different technologies has
lead to the concept of beyond International mobile telephony 2000(IMT-2000) wireless networks known as the next
generation wireless networks (NGWN). In this heterogeneous environment, the end user is expected to be able to
connect to any of the different available access networks. The end user will also be able to roam seamlessly within these
access networks through vertical handover mechanisms. The global roaming is supplemented by the existence of IP
networks as the backbone which makes the mobile computing environment to grow leaps and bounds and can
effectively address the issue with regard to converge limitations is concerned. In this multifaceted wireless radio
environment the radio resource management plays major role. The effective utilization of the limited available resources
is the challenge. The admission control is one such challenge a network service provider face to achieve better system
utilization face in handling this complex scenario to provide the best QoS to the users of the network.
Call admission control schemes can be divided into two Categories, local and collaborative schemes [1]. Local schemes
use local information alone (e.g. local cell load) when taking the admission decision. Examples of these schemes are(T.
Zhang, E.v.d. Berg, J. Chennikara, P. Agrawal, J.-C. Chen, T. Kodama, 2001)(C.-T. Chou, K.G. Shin, 2002)(C.W. Ahn,
R.S. Ramakrishna, 2004). Collaborative schemes involve more than one cell in the admission process. The cells
exchange information about the ongoing sessions and about their capabilities to support these sessions (T. Zhang, E.v.d.
Berg, J. Chennikara, P. Agrawal, J.-C. Chen, T. Kodama, 2001).The fundamental idea behind all collaborative
admission control schemes is to consider not only local information but also information from other cells in the network.
The local cell, where the new call has been requested, communicates with a set of cells that will participate in the
admission process. This set of cells is usually referred to as a cluster. In general, the schemes differ from each other
according to how the cluster is constructed, the type of information exchanged and how this information is used. In (M.
Naghshineh, M. Schwartz, 1996) for example, the cluster is defined as the set of direct neighbors. The main idea is to
make the decision of admission control in a decentralized manner.
System Model
In this paper we propose a novel analytical model for admission control for the call blocking probability there by
increasing the resource utilization. This would achieve the Objective of guaranteeing the user QoS requirements. The
proposed model is able to handle three types of applications which are complementary in nature with respect to their
QoS requirements are considered. The applications considered for the study involves conversation traffic,
interactive traffic and background traffic. The representative applications could be voice calls, Web browsing and file
transfer applications respectively. We have considered a heterogeneous network which comprises a set of RATs Rn with
co-located cells in which radio resources are jointly managed. Cellular networks such as Wireless LAN and Wi-Max
can have the same and fully overlapped coverage, which is technically feasible, and may also save installation cost. H is
the set of heterogeneous wireless networks coexisting is given as H= {RAT 1, RAT 2, RAT k} and where K is the total
number of RATs in the heterogeneous wireless network. The heterogeneous wireless network supports n-classes of calls,
and each RAT in set H is optimized to support certain classes of calls.
Conclusion and Future Work
In this paper, we have proposed a performance model for call admission control mechanism in the heterogeneous RATs
and analyzing the call blocking probability keeping the variation in the number of channels. In order to measure the call
blocking probability of the analytical model the simulation study was made and following observations were made. In
the experiment setup all the types of traffic was varied and Firstly, increase in the number of type1 users will increase
the call blocking probability of type2 and type3 calls and vice versa. Second, Increase in the traffic intensity of one type
of traffic will increase the system blocking probability.
The concept of minimizing the call blocking probability is an optimization technique to provide fair QoS to the set of
users in the wireless network and there is also a need of intelligent call admission control strategy in the admission
control mechanism to make the decision of accepting are rejecting a call keeping the blocking probability minimal in a
heterogeneous RATs based network working under dynamic network condition. The future work of this research is
pitched upon using Intelligence to the call admission control decision process .The future work includes application of
Fuzzy neural technique for the decision making .It is evident from the above discussion that that the application of
intelligent techniques with multiple criteria for decision making is worthwhile.