ISSN (Print) : 2320 – 3765 ISSN (Online) : 2278 – 8875 International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering Vol. 2, Issue 4, April 2013 Copyright to IJAREEIE www.ijareeie.com 1388 Call Admission Control in Cellular Network Shruti B. Deshmukh 1 , Vidya V. Deshmukh 2 M.E. Student, Dept. of E&TC, AISSMS College of Engineering, Pune, Maharashtra, India 1 Assistant Professor, Dept. of E&TC, AISSMS College of Engineering, Pune, Maharashtra,India 2 ABSTRACT: A call admission control (CAC) algorithm used for WCDMA prioritized uplink for UMTS, which combines QoS tolerance and service differentiation by priority for voice, data, multimedia. This CAC algorithm gives preferential treatment to high priority calls, such as soft handoff calls, by reserving some bandwidth margin (soft guard channel) , Power consumption, no. of users ( load ) to reduce handoff failures. In addition, queuing is also used to enhance the service quality. The algorithm uses the effective load as an admission criterion and applies different thresholds for new calls, handoff calls, bandwidth requirement, power consumption. Finally, the study considers three types of services: voice, data and multimedia calls. Use of CAC algorithm indicate that this algorithm reduces the drop of handoff calls and increases the total system capacity and performance; hence the Grade of Service ( GoS ) of the system can significantly be improved especially in case of high mobility environments. Keywords: No. of users(load), Bandwidth, Power Consumption, CAC, UMTS, W-CDMA, QOS. I. INTRODUCTION Now a days Third generation radio communication systems are designed to offer multimedia services, including voice and video telephony and high-speed Internet access. In Universal Mobile Telecommunication System (UMTS), the radio interface is based on the Wideband Code- Division Multiple Access (W-CDMA) technology. UMTS WCDMA is a Direct Sequence CDMA system (DS-CDMA). WCDMA has two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). In the FDD mode, uplink and downlink transmissions use different frequency bands while for the TDD mode, uplink and downlink transmissions can be implemented on unpaired bands but separated by a guard period. In this paper DS-CDMA (FDD) is considered [1]. The measurement of the resource capacity in a spread spectrum system is distinct from conventional TDMA/FDMA systems. In conventional TDMA and FDMA systems such as IS-54 (TDMA) and GSM (hybrid TDMA/FDMA), the number of traffic channels are fixed. It is determined by the number of time slots in the TDMA system or by the number of non-overlapping frequencies in the FDMA system. The spread spectrum system, such as WCDMA, does not have a fixed number of channels. Instead, the capacity of the CDMA system is limited by the total interference the system can tolerate. Such a system is referred to as an interference-limited system. Each additional active mobile user will increase the overall level of interference. Normally, the interference level increases rapidly when the system load reaches a certain level. Users with different traffic profiles and attributes such as the service rate, the signal to- Interference ratio (SIR) requirement, media activity, etc. introduce different amounts of interference to the system. These factors are especially important in 3G wireless networks that support multimedia services. The coverage of WCDMA is assumed uplink limited in high-load scenarios. The capacity of DS-CDMA networks depends on the reverse link (uplink) rather than the forward link (downlink). Uplink call admission control strategies play a very important role in the performance of CDMA systems as it directly controls the number of users in a cell and thus limit the interference in the system. In this paper only the uplink direction is considered. With desired features such as high system capacity (soft capacity), low power transmission, soft handoff, multipath mitigation, and interference suppression [1], code-division multiple access CDMA) has been adopted for third- generation wireless communication systems. The third generation wideband CDMA cellular system must be able to support integrated services with differentiated quality-of-service (QoS) requirements. Thus, a sophisticated call admission control (CAC) is needed so that the system can satisfy various QoS constraints such as the forced termination (drop call) probability for handoffs and the outage probabilities for different services, and maximize the spectrum utilization[6]. II. REQUIREMENTS FOR CAC SYSTEM 1. Limit the interference 2. QoS Requirements 3. To support multimedia services 4. Fast internet access