Efficient Location-Based Hard Handoff Algorithms for Cellular Systems Antonis Markopoulos, Panagiotis Pissaris, Sofoklis Kyriazakos, and Efstathios D. Sykas National Technical University of Athens, School of Electrical and Computer Engineering, Telecommunications Laboratory, 9 Heroon Polytechneiou Street, Zographou 15773, Athens, GREECE Contact: antony@telecom. ntua. gr Abstract. Mobile world's rapid growth hasspurred development of new proto- cols and new algorithms to meet changing operation requirements- such as mo- bile networking, and quality-of-service support. Handoff is one of the most critical procedures in cellular systems. Network operators give emphasis to op- timize handover, since it is strongly related to dropped calls, network overload and subsequently users' criticism. Handoff can be seen as a blind procedure, if it is only based on the comparison of measurements, without the information of location. Since signal propagation and pathloss are complex in nature, we can expect unnecessary and wrong handoff executions. Both UMTS and those of the second generation (GSM) systems will require redefined handoff algorithms of active connections as the smooth mobility support and continuous connec- tion are essential issues for obtaining high performance and increasing user satisf action. In this paper we present a set of intelligent algorithms using the mobile terminal (MT) location information and area awareness to assist safe handoff decisions. The implemented algorithms are validated by means of cel- lular network simulators that clearly show the impact of these techniques to major system performance metrics. 1 Introduction The paper mainly focuses on the improvement of network performance when MT position is taken into account. For that purpose, we defined and implemented new innovative handoff algorithms. Wehave also developed two network simulators, one for GSM and one for UMTS, to validate those algorithms. The simulators were de- veloped from scratch and are used to evaluate the performance of existing handoff algorithms as weil as to validate the simulator models of our new al gorithms. To produce safe results a !arge nurober of simulations were performed. The paper is organized around 5 sections. Section 1 is the introduction. Section 2 introduces innovative handoff algorithms based on MT location and area information. In section 3 we present the basic simulators Iayout and results of numerous simula- tions that show the network performance behavior for both systems. The results are very optimistic since increased network performance under normal and high traffic Ioad situations is clearly shown. Finally in secti on 4 we sum up with the conclusions. N. Mitrou et al. (Eds.): NETWORKING 2004, LNCS 3042, pp. 476--489, 2004. © IFIP International Federation for Inf ormation Processing 2004