Adaptive Algorithm for Admission Control in Wireless Networks Ahlem SADDOUD Electronics and Information Technology Laboratory, National School of engineering of Sfax (ENIS) ahlem.saddoud@fsegs.rnu.tn Lamia FOURATI CHAAR! Lott KOU Electronics and Information Technology Laboratory, National School of engineering of Sfax (ENIS) lotf.kamoun@isecs.ru.tn Electronics and Information Technology Laboratory, National School of engineering of Sfax (ENIS) lamia.chaari@enis.rnu.tn Abstract-Real time multimedia applications become an important part of Internet trafc and require a guaranteed quality of services. Call Admission Control (CAC) is a key element in the provision of guaranteed (QoS) in wireless networks. An adaptive algorithm is proposed in this paper. The QoS measures studied are new call blocking probability and handot call probability. We describe and we compare several adaptive admission control schemes in terms of performance and complexity. Also, maintaining the blocking probability below a certain value (threshold) adaptively to QoS requirements is the common purpose of the proposed CAC algorithm. The bandwidth resources allocated to handot calls and new calls change dynamically in order to maintain the threshold of the call blocking probabilities. Keords- admission control; cal blocking probabit; Hanof cal; bandidh resources I.INTRODUCTION Wireless Systems are expected to support multimedia services with diverse quality of services, such as voice, video and data. Due to the rapid growth in mobile users and limited radio resources, CAC becomes a crucial factor that guaranties the QoS and utilizes the network resources [1]. CAC is critical step for the provision of QoS guaranteed services in wireless networks [2]. When a subscriber station SS send a request to the base station (BS) with a certain QoS parameters for a new connection, the BS will check whether it can provide the required QoS for that connection. If the request was accepted, the BS verifes whether the QoS of all the ongoing connections can be maintained. Based on this it will take a decision on whether to accept or reject the connection. The process described above is called as CAC mechanism. Thus, CAC restricts the access to the network in order to prevent network congestion or service degradation for already accepted users. The most important concern for providing CAC in wireless networks is to guarantee QoS of connections and at the same time decreasing the Call blockng probabit (CBP). Most CAC algorithms have a strong relationship with the bandwidth utilization [3] [9] [10], the total number of calls and the call blocking probability [4]. The admission control schemes described in section 1 and 2 use two kinds of calls namely new calls and handof calls. Both of them (new and handof calls) may be rejected if there are not enough resources. However, Handoff calls are more prioritized than new calls. In the following sections, we will discuss the admission control algorithms and we will focus on "Call blockng probabit" as it is an important parameter that refects the CAC schemes efciency. Call blocking probability for the new and handoff call are defned as follows: New-Call Blocking Probability (CBP): according to resource utilization of cell system, new calls may be rejected or accepted. In a certain time span, there are rejected new calls (denoted as Nd) and accepted new calls (denoted as Nc). The ratio of total rejected new calls to total new calls (the sum of Nd and Nc) in a certain time span is defned as Call-Blocking Probability (Pb), which can be described as follows: Pb = Nd /( Nc + Nd) Handoff-Call Blocking Probability (HBP): Similarly, according to resource utilization of cell system, the call handofed from neighbour cells may be rejected or accepted. In a certain time span, there are rejected handoff calls (denoted as Hd) and accepted handof calls (denoted as Hc). The ratio of total rejected handoff calls to total handof calls (the sum of Hc and Hd) in a certain time scale is defned as Handof-call Blocking Probability, which can be described as follows: Pd= Hd /(Hc + Hd). The remainder of the paper is organized as follows: section1 describes several adaptive algorithms for call admission control in wireless networks. The Quality of Service Adaptive Call Admission Control (QoS AdCAC) is described in section2. Section3 evaluates the performance of the diferent CAC schemes by 978-1-4244-8840-7110/$26.00 ©2010 IEEE