Fuzzy call admission control combined with distributed dynamic channel assignment and reassignment for cellular mobile systems

Shih-Cheng Horng,Shieh-Shing Lin

doi:10.1186/s13638-015-0330-5

Abstract

In a cellular mobile system (CMS), the service area is divided into cells, each of which has numerous channels, which are shared by two types of call - new calls and handoff calls. Giving a higher priority to handoff calls than new calls is common practice. However, giving too much priority to handoff calls will result to excessive blocking of new calls. This work firstly proposes a distributed dynamic channel assignment and reassignment (DDCAR) scheme to satisfy three types of constraint - co-channel constraint (CCC), adjacent channel constraint (ACC), and co-site constraint (CSC), simultaneously. The purpose is to minimize the number of available channels that become unavailable for the assignment to new calls and to maximize the number of unavailable channels that become available for release when calls complete. To provide a higher priority to handoff calls, a fuzzy call admission control (FCAC) scheme, combined with the DDCAR, is proposed herein for implementation at the base station. A 7 × 7 CMS with two traffic patterns is employed as the test example. The test results reveal that the FCAC scheme significantly reduces the dropping probability of handoff calls at the cost of increasing the blocking probability of new calls to an acceptable level.

Highlights

Nowadays, the cellular mobile system (CMS) has become one of the most profitable mobile systems because more applications are being made available for smart phones, which have very attractive functions [1,2]
In a CMS, three types of interference are generally treated as constraints; these are the co-channel constraint (CCC), the adjacent channel constraint (ACC), and the co-site constraint (CSC) [3,4]
The shortcomings of such centralized schemes are as follows; (i) the mobile switching center (MSC) is increasingly likely to fail owing to an overload of call requests as the size of the CMS grows with the growth in the number of mobile users [15,16], and (ii) determining the best available channel is time consuming even when heuristic methods are used, and a new call may be blocked as a result of just one unsuccessful assignment

Summary

Introduction

The cellular mobile system (CMS) has become one of the most profitable mobile systems because more applications are being made available for smart phones, which have very attractive functions [1,2]. In all of the above approaches, the DCA is centrally implemented in the mobile switching center (MSC) or in a cell with a central controller, which collects information about all of the cells in the CMS The shortcomings of such centralized schemes are as follows; (i) the MSC is increasingly likely to fail owing to an overload of call requests as the size of the CMS grows with the growth in the number of mobile users [15,16], and (ii) determining the best available channel is time consuming even when heuristic methods are used, and a new call may be blocked as a result of just one unsuccessful assignment.

Distributed dynamic channel assignment and reassignment

Test results and comparison

Findings

Conclusions