Análisis de la contaminación de Códigos de Mezclado en un sistema WCDMA

Abstract

In the present work is developed a methodology to find out the pilot pollution within a Wideband Code Domain Multiple Access WCDMA network, generated by the coverage overlapping of the different base stations serving one area or region. The analysis is based on coverage estimation maps created from punctual power levels measurements made in the field from one of the key performance indicators of the WCDMA system, the Common Pilot Channel, CPICH. The experimental analysis is conducted by delimiting a study area and using specialized measurement equipment with demodulation capabilities of WCDMA signal to obtain the Scrambling Codes. Scrambling Codes are used in the Downlink direction to identify and separate cells and sectors that are transmitted by the base stations –NodeB- over the physical channel named Common Pilot Channel CPICH. From over the air measurements of WCDMA signal collected in an outdoor environment, relevant information is extracted and post processed in Matlab Software. CPICH power coverage estimation maps initially tagged with only GPS Geographic Positioning System information from the row data are further mapped on GIS Geographic Information System, allowing to identify problematic zones, coverage overlapping and trends in the WCDMA signal propagation. The presence of too many strong sectors in a location creates what is called as pilot pollution with consequences such as low data rate, low capacity, and excessive soft handoffs deteriorating the Quality of Service.