The satellite component of the future Universal Mobile Telecommunications System (UMTS) is anticipated to be partly composed of non-geostationary satellites such as Low-Earth Orbit (LEO) satellites. Those networks are designed to support multimedia traffic with different quality of service (QoS) requirements. This paper deals with the performance evaluation of a new channel resource management technique in Low-Earth Orbit (LEO) satellite systems based on a satellite-fixed cell concept. In cellular and satellite networks the resource capacity is shared among handovers and new calls. Forced termination has a significant impact on the quality of service perceived by the users. This is especially the case for those which have delay constraints (such as video or voice traffic). The guard channel scheme is an access priority that has been proposed in order to reduce the handover failure probability. Its effectiveness has been emphasized in terrestrial cellular networks. In this paper, we propose a dynamic reservation scheme for satellite networks which adapts the number of reserved channels, according to the current number of ongoing calls (voice or video traffic) and on the localization of users. A performance evaluation of the proposed mechanism has been carried out by simulations as regards with the blocking probabilities of each type of users.