To meet capacity challenges in current and next-generation (CDMA) cellular systems, operators have few good choices. The most direct approach to expanding cellular capacity involves increasing the density of tower sites. This option is both costly and limited by local municipality site restrictions. New frequency allocations are also becoming expensive or simply unavailable. In order to improve frequency re-use, smart antenna technology is expected to see more widespread deployment. Enhancements range from basic dynamic sectorization schemes to sophisticated phased-array approaches.
Successful communication between handset and cell site depends upon signal propagation through indirect reflected paths between the handset and the cell tower. Characteristic of such paths are the spatial and temporal variations observed in signal strength. Additionally, the receiving system must handle the background interference contributed by other active CDMA handsets. Because of the spatial variations in signal strength, reliable reception relies on the deployment of multiple antennas atop each cell tower. In current practice, a separate receiver channel is utilized for each antenna with the strongest signal available at a given moment selected for cell-phone processing. Unfortunately, this simple diversity reception approach is wasteful of system capacity. In a fashion similar to the way NavTrack™ enhances GPS signal reception in conditions of fading, blockage, and jamming, WaveTrack™ optimally processes the raw signal from each diversity element in recovering the best overall signal from each element. This method of CDMA capacity improvement is applicable to diversity systems utilizing both conventional and phased array antenna structures.