COVERAGE ENHANCEMENT IN CELLULAR RADIO NETWORKS BY APPLYING DIGITAL FIXED RELAY

Abstract

The modern cellular networks are always endeavoring continuously to present multi services, like internet service, multimedia, file transfer, download etc, in addition to providing high quality voice for customers. All these services need a high data rate coverage. Therefore, interest has focused on increasing the coverage area to enhance the performance of networks. In this paper, we present employment of the Digital Relay to increase the coverage ratio of cell, through covering the areas that are not covered by Base station (BS), these areas are known as coverage holes (dead spots), which are studied in accurate form. This paper includes how to determine the position and angle of the coverage holes, which depend on analysis of the results of propagation Model and Signal to interference ratios. Therefore, we propose to put relays in these areas (coverage holes) with distance equal to fifth of cell radius between this position and the edge of cell. Also in this paper, the optimum number of Digital Relay is determined for each cell and the optimum transmitted power from Base station and Digital Relay to avoid the interference problem. The simulation system in this paper focuses on the handoff process between Base Station and Digital Relay, the results show that the proposed position gives suitable period to execute the handoff process without blocking the calls. The results show when the cluster size of system consists of seven cells high enhancement in performance of cellular networks which apply the Digital Relay. Where the enhancement ratios when comparison the cellular networks that applying Digital Relay technique with conven-tional cellular networks 33.16% in the blocking probability and 18% in the number of users. When the cluster size of system consists of thirteen cells, the enhancement ratios is 34.18% in the blocking probability and 18% in the number of users.