Numerical Approach to Performance Analysis of Multi-Parametric CAC in Multi-Service Wireless Networks

Abstract

Cellular wireless network (CWN) consists of radio access points, called base stations (BS), each covering certain geographic area. With the distance power of radio signals fade away (fading or attenuation of signal occurs) which makes possible to use same frequencies over several cells, but in order to avoid interference, this process must be carefully planned. For better use of frequency recourse, existing carrier frequencies are grouped, and number of cells, in which this group of frequencies is used, defines so called frequency reuse factor. Therefore, in densely populated areas with large number of mobile subscribers (MS) small dimensioned cells (micro-cells and pico-cells) are to be used, because of limitations of volumes and frequency reuse factor. In connection with limitation of transmission spectrum in CWN, problems of allocation of common spectrum among cells are very important. Unit of wireless spectrum, necessary for serving single user is called channel (for instance, time slots in TDMA are considered as channels). There are three solutions for channels allocation problem: Fixed Channel Allocation (FCA), Dynamic Channel Allocation (DCA) and Hybrid Channel Allocation (HCA). Advantages and disadvantage of each of these are well known. At the same time, owing to realization simplicity, FCA scheme is widely used in existing cellular networks. In this paper models with FCA schemes are considered. Quality of service (QoS) in the certain cell with FCA scheme could be improved by using the effective call admission control (CAC) strategies for the heterogeneous traffics, e.g. see [1][3]. Use of such access strategy doesn’t require much resource, therefore this method could be considered operative and more defensible for solution of resource shortage problem. Apart from original (or new) calls (o-calls) flows additional classes of calls that require special approach also exist in wireless cellular networks. These are so-called handover calls (h-calls). This is specific only for wireless cellular networks. The essence of this phenomenon is that moving MS, that already established connection with network, passes boundaries between cells and gets served by new cell. From a new cell’s point of view this is h-call, and since the connection with MS has already established, MS handling transfer to new cell must be transparent for user. In other words, in wireless networks the call may occupy channels