Relationship between the maximum likelihood emitter location estimators based on received signal strength (RSS) and received signal strength difference (RSSD)

Under the assumption of a log-normal path loss model, maximum likelihood (ML) emitter location estimators are derived for both received signal strength (RSS) and received signal strength difference (RSSD) information. It is then shown that these ML estimators are identical, contrary to the seemingly common perception that the RSS-based ML location estimator should outperform the RSSD-based ML location estimator. The Cramer-Rao lower bounds (CRLB) for the average miss distance are also shown to be identical. Using the least squares estimation criterion, a non-linear least squares (NLS) emitter location estimator is also formulated in this paper for comparison. These theoretical developments are illustrated by computer simulation experiments.