Estimating the Cell Radius from Signal Strength Measurements

Abstract

A robust method for determining the boundaries of cells and the associated reliability of the RF coverage within these boundaries is presented. The procedure accurately determines the effective cell radius using a linear regression of RF signal strength samples. The accuracy of this estimate is quantified both as a radius uncertainty (e.g.,± 100 meters) and as a cell coverage reliability (i.e., area/edge) through 1) simulation, 2) analysis of real data, and 3) theoretical analysis. It is shown that if the estimate of the cell radius meets the desired accuracy, then the corresponding estimates of coverage reliability (both area and edge) are more than sufficiently accurate. It is discovered that estimating the cell radius is a much more critical step in determining the quality of RF coverage than the more common practice of simply estimating the area reliability. In addition, a formula for estimating area reliabiliy is given and shown to be more accurate than the estimate of the cell radius. The validation method presented here is particularly useful in wireless planning since it accurately determines the effective geographic extent of reliable RF coverage. It is recommended that radio survey analyses incorporate this cell radius estimate as part of the coverage validation process.