Telecommunication Systems 17:1,2, 233–241, 2001  2001 Kluwer Academic Publishers. Manufactured in The Netherlands. NACR: A New Adaptive Channel Reservation in Cellular Communication Systems ANDRÉ-LUC BEYLOT beylot@enseeiht.fr ENSEEIHT – IRIT/Tesa Lab., 2 Rue C. Camichel, BP 7122, 31071 Toulouse Cedex 7, France SELMA BOUMERDASSI boumer@cnam.fr CNAM-Cedric Lab., 292 Rue St. Martin, 75141 Paris Cedex 3, France GUY PUJOLLE guy.pujolle@lip6.fr LIP 6, 4 Place Jussieu, 75005 Paris, France Abstract. Future Personal Communication Networks (PCN) will employ microcells and picocells to sup- porta higher capacity, thus increasing the frequency of handoff calls. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The proposed guard chan- nel schemes for radio channel allocation in cellular networks reduce handoff call blocking probability at the expense of increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. Under uniform traffic assumptions, it has been shown that a fixed number of guard channels leads to good performance results. In a more realistic system, non-uniform traffi conditions should be considered. In this case, the achieved call blocking probability may deviate signifi- cantly from the desired objective. In this paper, we propose a new adaptive guard channel scheme: New Adaptive Channel Reservation (NACR). In NACR, for a given period of time, a given number of channels are guarded in each cell for handoff traffic. An approximate analytical model of NACR is presented. Tabu search method has been implemented in order to optimize the grade of service. Discrete event simulations of NACR were run. The effectiveness of the proposed method is emphasized on a complex configuration. Keywords: adaptive bandwidth resource management, dynamic guard channel scheme 1. Introduction The bandwidth in a wireless network is perhaps the most precious and scarce resource of the entire communication system. This resource should be used in the most efficient manner. A base station sometimes may need to reserve resources, even if this means denying access to a mobile terminal requesting admission to the network. Handoff call blocking are generally more objectionable than new call blocking from the subscriber’s perspective. Consequently, a base station should keep enough resources to support active users currently outside of its coverage area, but who may soon emigrate to its cell. Thus base stations must maintain a balance between the two conflicting requirements: first maintaining maximum resource (bandwidth) utilisation and second reserving enough bandwidth resources so that the maximum rate of unsuccessful incoming handoffs (due to insufficient resources) is kept below an acceptable level. The probability of an unsuc-