Cramer-Rao lower bounds for nonhybrid and hybrid localisation techniques in wireless networks

Theoretical performances of localisation techniques are revisited in this paper. Expressions of asymptotic Cramer-Rao lower bounds are derived for nonhybrid and hybrid localisation techniques based on received signal strength indicator, time of arrival and time difference of arrival under Gaussian uncorrelated measurements assumption. These localisation techniques and the useful expressions of their maximum likelihood estimators are presented in this paper. From these expressions, asymptotic Cramer-Rao lower bounds expressions are derived. Simulations are then carried out using realistic location-dependent parameters (LDPs) values to evaluate different nonhybrid and hybrid techniques of localisation. Simulations show that the fusion of more than one LDP enhances localisation accuracy and gives alternatives for the lack of LDPs. Moreover, the number, the nature, the precision of measurements and the reference nodes positions are the key parameters that influence localisation accuracy. Copyright (C) 2011 John Wiley & Sons, Ltd.