MINIMIZATION OF SIGNAL INTERFERENCE IN COLLOCATION ANTENNA

Abstract

Due to the expansion of wireless technology globally in terms of the number of users, there is a need to improve both the capacity and coverage of the wireless network. Such need for more capacity and coverage has a very serious cost implication in the course of deployment and maintenance of the infrastructure and other necessary things. Bent on ensuring adequate capacity and coverage, telecommunication operators often combine to build the infrastructure and then collocate their transceivers on the same tower to minimize cost, giving rise to collocation sites. This collocation situation is known to give rise to interference that degrades the quality of service, even resulting in call dropping, poor voice quality and other ugly experiences. This research work looked at minimization of interference in such collocated situations.  A collocated site at Winners Chapel, Ozuoba (Lat. 4.871113 and Long. 6.925878) and a single site at pipeline road (Lat 4.872134 and Long 6.921143), still at Ozuoba, were studied. The signal strength of both the single and collocated sites were measured using Radio Frequency Signal Detector (RFSD) at twenty different points, with the first point being 50m from the base stations and each of the subsequent points being 50m apart, giving a total of 1km. Network signal to interference noise ratio for the single and collocated sites was computed using the measured data. The capacity loss as a result of interference from the collocated site was also determined. Antenna isolation and filtering techniques as adopted as means to minimize interference. The result of the research work showed that collocated system is adversely affected by interference compared to single site. The highest capacity loss due to interference in the collocated system was found to be 64%, and this occurred at a distance of 200m from the base station with 55 mobile stations connected. The least capacity loss was 4.1% at 1000m from the base station and 15 mobile stations connected, indicating that the closer an interferer is to the system, the greater the level of capacity loss. It was also found that SINR for the collocated system was 0.92dBm at 1000m and 0.69dBm at 50m while for a single site SINR was 0.61dBm and 0.47dBm at 1000m and 50m respectively