REDUCING CONTROL DATA IN JOINT TRANSMISSION USING HIERARCHICAL CLUSTER-HEAD TABLE

Abstract

ABSTRACT Users on the edge of the cell experience a combination of low received signal strength and high co-channel interference that originates from adjacent base stations. This significantly affects the perceived quality of mobile communication service at the edge user. In order to improve the poor indices of edge users, the concept of joint transmission was developed so that potential interferers would become potential co-transmitters of useful information to the edge user. Being co-transmitters implies that multiple base stations will transmit user data along with the main base station to the edge user. A set of multiple transmission points, also called cluster is coordinated by a central processing unit or cluster-head in an approach known as Coordinated Multipoint (COMP). For this to occur, control messages required for Coordination must be generated. The number of control messages required to perform joint transmission is prohibitive, and competes with the user data for bandwidth. The remaining bandwidth available for user may be insufficient for large number of users, especially the edge user. The lack of sufficient bandwidth further introduces significant delay causing the latency to increase. Both the problem of limited bandwidth for user data and increase in latency are detrimental to the goals of 5G communications. This research work focuses on reducing the number of control data required to perform COMP Joint Transmission (JT). The developed scheme, Hierarchical JT COMP develops a COMP weight from throughput and satisfaction index of base stations, and introduces a hierarchical table for JT COMP from which cluster- heads are selected. The Hierarchical JT COMP approach simplifies the method of selection of the cluster head for JT COMP by listing all base stations in an ordered table as potential cluster-heads. An algorithm for Hierarchical JT COMP is implemented on MATLAB 2019, and the outcomes are measured against state-of-the-art Direct CSI- Feedback to Elected Coordination-Station (DCEC) COMP JT for the control data and the latency. However the SINR index is measured against non-JT COMP transmission to project the clear advantage of JT COMP over non-JT COMP approach for edge users. Results obtained showed that control data in Hierarchical JT COMP achieved up to 10.5% reduction, while network latency improved by about 17.39% compared to DCEC JT COMP after incorporating delays from data fetching from saved Hierarchical tables. For the SINR, non-JT-COMP users on the edge performed 377% worse than the JT COMP users on the edge of the cell. This research shows that control data can be further reduced in JT COMP using the Hierarchical JT COMP to take up less bandwidth, which implies more bandwidth available for user data.