Path loss data normalization for growth management of a cellular system
The RF propagation of a wireless system is normalized to remove the directionality, orientation and gain characteristics of the antennae deployed in the system to allow for enhanced growth management of a wireless system. RF propagation data for a wireless system is gathered by any collection method. For example, drive test of the cellular system can be performed to receive and measure the signal strength throughout the system to determine the receive power of signals from cell sites in the system. Other methods such as uplink collection, E911 data can be used. After measurements of the system are collected, the data is post-processed to remove the effective gain achieved by each antenna associated with each of the signals to normalize the signals to a conceptual antenna having an isotropic radiation pattern. A database of the antenna gain and deployment patterns of the actual antennae in the system is used to normalize the data. The expected receive power of the conceptual antennae signals at the locations throughout the cellular system are determined using a propagation model. The modeled conceptual signals correspond to the measured signals and the characteristics of the conceptual antennae substituted to model the conceptual signals. The Propagation modeling can be revised through analysis of the correlation with the measured data. Once the system has been normalized and the propagation model is acceptably accurate, the system designer can model data corresponding to a variety of antenna gain, directionality and orientation choices to effectively enhance growth management through effective redeployment and specification of antennae without the need to physically experiment with antenna of varying characteristics and perform numerous data collections after antennae substitutions or reconfigurations. A final data collection such as a final drive test can be performed after implementation of a new antenna deployment.
1. A method of refining the determination of the quality of signal coverage in a wireless system, comprising the steps of:
measuring actual path loss data at a plurality of locations within said wireless system by gathering signal level data at said plurality of locations, differentiating individual signals within said signal level data, determining the sector of origin of each of the individual signals, determining the path loss for each of the individual signals, retrieving a set of antenna parameters for each antenna corresponding to the sector of origin for each antenna, and normalizing the path loss value for each signal as a function of the retrieved antenna parameters;
obtaining predicted path loss data from a propagation model applied to said wireless system; and
combining said measured data and said predicted data to augment said measured path loss data to determine data for locations without measured data.
2. The method of claim 1 , wherein:
said combination is a weighted combination wherein said measured data and said predicted data are assigned confidence indicators to determine the optimal weighting of each of said data.
3. The method of claim 1 , further comprising:
assigning a confidence factor to each value within each set of data wherein said confidence factor is greater for measured data and is based upon the relationship between the data for a particular location and the data for proximate locations.
4. A method of managing the growth of a wireless system, comprising the steps of:
sub-dividing a drive test region into a plurality of spatial bins;
within each of said plurality of bins, measuring a signal from each of a plurality of sectors, which are within a region of examination that is at least partially co-extensive with or within propagation distance of said drive test region, to determine the receive power of said measure signal;
removing the effective gain achieved by an antenna associated with each said measured signals to normalize each of said measured signals to a conceptual antenna having an isotropic radiation pattern;
applying a propagation model to a conceptual signal from each sector of said plurality of sectors to determine the predicted receive power of the conceptual signal within each of said plurality of bins, wherein each of said modeled conceptual signals corresponds to a different one of said measured signals and the characteristics of said conceptual antenna are used to model said conceptual signals; and
correlating each of said measured signals with said corresponding modeled conceptual signal.
5. The method of claim 4 , further comprising the step of:
revising said propagation model, based on said correlation between each measured signal with said corresponding modeled conceptual signal, to create a revised propagation model that better predicts an expected path loss of said conceptual signal.
6. The method of claim 5 , further comprising the step of:
applying said revised propagation model to said conceptual signal from each sector of said plurality of sectors to determine the expected path loss to a number of additional spatial bins.
7. The method of claim 5 , further comprising the step of:
applying said revised propagation model to a planned signal from each sector of a planned plurality of sectors to determine the expected path loss of said planned signal to each of said plurality of bins.
8. The method of claim 7 , further comprising the step of:
varying a propagation parameter value of said planned signal;
applying said revised propagation model to said planned signal and each of said plurality of bins; and
identifying an improved overall co-channel signal-to-noise ratio for said system based upon a revised propagation corresponding to a set of varied propagation parameters.