Cell average carrier-to-interference coverage improvement by using DSP interference rejection techniques

The performance of a cellular phone system can be evaluated from several perspectives, one of which is the capacity. The capacity of a cellular system can be described by the cell carrier-to-interference ratio coverage (or the percentage of a cell area in which the carrier-to-interference ratio (CIR) is greater than a specific threshold). A theoretical form of the cell carrier-to-interference ratio coverage is derived for both the forward and reverse links. The cell average CIR coverage is also compared to the cell worst case CIR coverage, where the mobile is at the edge of its serving cell but is at the location closest to its interfering cell. The analysis is used to show how the coverage and the capacity can be improved by incorporating digital signal processing (DSP) interference rejection techniques, such as a time-dependent adaptive filter (TDAF). Results indicate that the average CIR coverage can be increased from 90% to 98% for the seven cell reuse pattern assuming an 18 dB threshold. For a three cell frequency reuse pattern, the average CIR coverage is increased from 73% to 96% assuming the same threshold. The improvement is significant, even when a lower frequency reuse pattern is assumed. Thus, the TDAF improves the received signal quality and provides a means to increase the system capacity by using a lower frequency reuse pattern