Methods for accurate use of finite dynamic range measurement data in radio path loss propagation model calibration
View Patent ↗Methods for accurately predicting radio propagation from signal strength measurements. Dynamic range limitations in the measurement data are explicitly taken into account. The resulting propagation models accurately predict signal strength for calculation of coverage and interference.
1. A method of accurately calculating an unbiased parameter set for application to a radio signal propagation model describing data of limited dynamic range, comprising the steps of:
a) representing a set of data points of radio signal data collected by a receiver as a censored data set, wherein said censored data set comprises a set of uncensored observations, a set of left-censored observations, and a set of right-censored observations; representing a set of N data points of radio signal data collected by a receiver as a truncated data set, wherein said truncated data set is truncated using a set of N lower truncation limits, wherein a lower truncation limit is calculated for each data point according to a sensitivity threshold of the radio signal data determined by said receiver, and wherein said truncated data set is further truncated using an upper truncation limit calculated according to an upper limit of the linear range of said receiver;
b) defining the set of uncensored observations as all measured data points with signal level within the linear range of said receiver;
c) defining the set of right-censored observations as the set of all measured points with a measured signal level above the linear range of said receiver;
d) defining the set of left-censored observations as the set of all signals not detected due to being below the minimum detection level of said receiver;
e) defining an upper censoring limit as equal to the upper limit on the linear range of said receiver;
f) defining a lower censoring limit as equal to the minimum detection level of said receiver; and
g) based on said censored data set, based on said lower and upper censoring limits, based on said sets of left-censored and right-censored observations, and based on a radio signal propagation model, calculating an unbiased parameter set maximizing the accuracy with which said radio signal propagation model describes said data set; wherein the method uses a censored likelihood function that only includes terms involving observed signals, the censoring limits, and said sets of censored observations.
2. The method of claim 1 , wherein said step of calculating comprises maximizing the likelihood of said radio signal propagation model to calculate radio path signal loss, given said data, said lower censoring limit, and said upper censoring limit.
3. The method of claim 1 , wherein said step of representing comprises representing the signal strength of the radio signal data.
4. The method of claim 1 , wherein said step of representing comprises representing the set of data points as collected by a cellular phone network.
5. The method of claim 1 , wherein said step of calculating is performed using a maximum likelihood (ML) fit.