Repeaters for hotspot capacity in DS-CDMA networks

Currently, wireless operators around the world are building code-division multiple-access (CDMA) based radio access networks and big efforts are made to find the most cost effective way to do so. In this paper, the novel use of repeaters in a direct-sequence CDMA (DS-CDMA) system such as UMTS to improve capacity in areas with hotspots (small areas with increased traffic volume) is studied through static Monte Carlo simulations. The performance of the repeaters is shown to be sensitive to tuning of the repeater gain. With correct tuning, the simulations show that the repeaters are very beneficial for the downlink, which is the capacity-limiting link. When repeaters covering the hotspots are introduced, the system is thus seen to tolerate more hotspot traffic. For a scenario in which the hotspots are located close to the cell border, the system tolerates approximately twice as high hotspot traffic load. For hotspots located halfway between the base station and the cell border, the system tolerates approximately 80% more hotspot traffic load. Also in the uplink, more hotspot traffic is tolerated when repeaters are introduced. The effect is smaller than for the downlink, however. The results indicate that repeaters are well suited to increase capacity of a WCDMA /UMTS system in hotspot areas.