Accurate localization using biased estimation

Localization of mobile stations(MS) is of considerable interest in wireless communication. In this paper, three algorithms are developed for accurate mobile location using the time-of-arrival measurements. The first algorithm is an unconstrained least square estimator(LSE) which has implementation simplicity. Our methods referring linear bias estimator(LBE) and affine bias estimator(ABE) are proposed based on the recently published research on biased estimation theory. Using MSE as the performance measure, we evaluate and compare the performance of such estimators. To our knowledge, performance improvement of our approaches over LSE is not resulted from additional information supplied by the constraint of MS itself, but from an expansion of the class of estimator under consideration. Traditional CRLB only acts as a theoretic bound of the unbiased estimator. Theoretical analysis and simulation demonstrate that the biased estimators are preferable to unbiased estimators at low or moderate SNR level.